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\title{Secondhand homes: Woodpecker cavity location and structure influences
secondary nester's success.}



\author[1]{Faith Hardin}%
\author[2]{Samantha Leivers}%
\author[3]{Jacquelyn Grace}%
\author[4]{Tyler Campbell}%
\author[2]{Brian Pierce}%
\author[3]{Michael Morrison}%
\affil[1]{Texas A and M University College Station}%
\affil[2]{Natural Resources Institute, Texas A\&M University }%
\affil[3]{Texas A\&M University College of Agriculture and Life Sciences}%
\affil[4]{East Foundation }%


\vspace{-1em}



  
  \date{May 13, 2024}


\begingroup
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\selectlanguage{english}
\begin{abstract}
1. Understanding how ecosystem engineers influence other organisms has
long been a goal of ecologists. Woodpeckers select nesting sites with
high food availability and will excavate and then abandon multiple
cavities throughout their lifetime. These cavities are crucial to
secondary cavity nesting birds (SCB) that are otherwise limited by the
availability of naturally occurring cavities. 2. Our study examined the
influence of food resources on the nest site location and home-range
size of woodpeckers, and the subsequent influence of woodpeckers on the
nesting success of SCB. 3. Using five years of avian point count data to
locate golden-fronted woodpeckers (GFWO), we correlated insect
availability with GFWO home range size, determined differences in insect
availability between GFWO occupied and unoccupied sites, and compared
nesting success for the GFWO and common SCB in south Texas. We used
model averaging to fit species-specific logistic regression models to
predict nest success based on cavity metrics across all species. 4.
Sites occupied by GFWO had a higher biomass of insects in orders
Coleoptera, Hymenoptera, and Orthoptera than unoccupied sites, and there
was a negative correlation between the availability of these insect
orders and home-range size. GFWO nest success increased with vegetation
cover and lower levels of tree decay. SCB had higher levels of nesting
success in abandoned GFWO, and in trees with lower levels of nest tree
decay. 5. Our results suggest that SCB may be drawn to nest in abandoned
woodpecker cavities where they have higher rates of nest success
compared to natural cavities. Additionally, the prevalence for GFWO to
excavate cavities in trees with lower levels of decay contradicts
previous literature, and may indicate a novel temperature trade-off,
with live trees requiring more energy to excavate, but providing
increased protection from high breeding season temperatures in arid and
semi-arid areas.%
\end{abstract}%



\sloppy


\textbf{1. INTRODUCTION}

Ecosystem engineers alter the availability of resources for other
species by causing physical state changes in biotic or abiotic materials
(Jones, Lawton \& Shachak, 1994; Wright, Jones, \& Flecker, 2002; Buse
et al., 2008). Given the important role they play in local environments,
the literature surrounding ecosystem engineers is historically focused
on how their actions affect other species (Jones et al.,
1994;\emph{Robles \& Martin, 2013};\emph{Tarbill, Manley, \& White,
2015};\emph{Wiebe, 2017}), but little research has been published on
what external factors influence the engineers themselves
(see\emph{Mikusinski, 2006};\emph{Jusino, Lindner, Banik, \& Walters,
2015}). Importantly, little has been done to investigate how ecosystem
engineers choose breeding and young rearing grounds (\emph{Nilsson,
Johnsson, \& Tjernberg, 1991}; Garmendia, C\selectlanguage{ngerman}árcamo, \& Schwendtner,
2006). Understanding these driving factors is essential to understanding
the ecology of not only the ecosystem engineers themselves, but the
organisms that rely on them for their own breeding and nesting grounds
as well.

The modifications made by ecosystem engineers have far-reaching
consequences and directly impact not only ecological associations, but
also the behavior of animals within an ecosystem. For example, animal
movement and community composition may be altered by the actions of
local ecosystem engineers (Lill \& Marquis, 2003; Bangert \&
Slobodchikoff, 2004). In this way, ecosystem engineers can indirectly
influence local trophic levels through multi-level environmental
modifications, such as altering local invertebrate diversity and
abundance, which in turn may increase foraging opportunities for other
vertebrates (Lill \& Marquis, 2003; Bangert \& Slobodchikoff, 2004), or
by providing more suitable species specific habitat for nesting
(Showalter \& Whitmore, 2002)

Although insects themselves can act as ecosystem engineers (Bell \&
Whitmore, 1997; Lill \& Marquis, 2003; Bangert \& Slobodchikoff, 2004),
they can also act as crucial resources for other ecosystem engineers at
higher trophic levels (\emph{Hess \& James, 1998};\emph{Pechacek \&
Kristin, 20}04). For example, declines in insect richness and abundance
have been reported with parallel declines in a number of insectivorous
ecosystem engineers, such as woodpeckers (\emph{Lister \& Garcia,
2018},\emph{Møller, 2019},\emph{Karr, 1976};\emph{Benton, Bryant, Cole,
\& Crick, 2002};\emph{Rioux Paquette, Pelletier, Garant \&}
\emph{Bélisle, 2014};\emph{Narango, Tallamy, \& Marra,
2017};\selectlanguage{english}\emph{Bowler, Heldbjerg, Fox, Jong, \& Böhning-Gaese, 2019}).
Therefore, ecosystem engineering activities may be better understood by
looking at the distribution and abundance of their food resources.

Woodpeckers are avian ecosystem engineers that have a large proportion
of insects in their diet (\emph{Jones et al., 1994};\emph{Tarbill et
al., 2015}), and control the location, construction, and availability of
nesting cavities, a limiting resource for secondary cavity nesting birds
(SCB; i.e. species that require a cavity to nest in but cannot create
the cavity themselves). Woodpeckers are primary excavators of nesting
cavities, often creating multiple cavities within their home range each
year to avoid predation, external parasite buildup, and cavity wood
degradation (Loye \& Carroll 1998; Husak \& Husak, 2002; Wiebe, 2017).
Once abandoned, these cavities are used by a variety of secondary cavity
nesting species (\emph{Martin \& Eadie, 1999},\emph{Pakkala, Tiainen,
Piha, \& Kouki, 2019}). Woodpeckers select nesting sites based on
characteristics that protect their eggs and nestlings from predation,
tending to nest high in moderately to heavily decayed trees with wide
diameters at breast height (DBH), and with limited vegetation covering
the cavity entrance (vegetation cover, Mannan, Meslow, \& Wight, 1980;
Li \& Martin, 1991; Loye \& Carroll, 1998; Newlon, 2005; Jusino et al.,
2016). Additionally, the shape of woodpecker cavities functions to
exclude nest predators by having small entrance holes and deep depths
(Sedgwick \& Knopf, 1990; Li and Martin, 1991; Martin, Aitken, \& Wiebe,
2004; Rhodes, O'donnell, \& Jamieson, 2009). Given the nest construction
preferences of woodpeckers, the cavities they leave behind are often
superior nesting spaces when compared to naturally occurring cavities,
both of which are used by SCB (Martin \& Li, 1992; Maziarz, Broughton,
\& Wesolowski, 2017).

Woodpecker resources can be defined both in terms of food (mainly wood
burrowing insects, largely in the order Coleoptera) and in the number of
trees suitable for excavation (\emph{Bonnot, Millspaugh, \& Rumble,
2009} ;\emph{Rota, Rumble, Lehman, Kesler, \& Millspaugh, 2015}). These
resources have been shown to be directly linked to woodpecker nest site
location and home range sizes (e.g. the area used by a bird in its daily
movements) (Worton, 1989; Powell, 2000;\emph{Wiktander, Olsson, \&
Nilsson, 2001};\emph{Pasinelli, 2007}). For example, the Black-backed
woodpecker (\emph{Picoides arcticus} ) selects nesting sites based on
infestations of the mountain pine beetles (\emph{Dendroctonus
ponderosae} ) (Rota et al., 2015), and the Three-toed woodpecker's
(\emph{Picoides dorsalis} ) home range size is negatively correlated
with the number of trees with suitable DBH for cavity excavation
(Pechacek \& d'Oleire-Oltmanns, 2004). However, no studies to date have
looked at the impact of food resources on both the nest site location
and home range sizes of woodpeckers, which in turn directly impacts
neighboring SCB.

The Golden-fronted woodpecker (GFWO, \emph{Melanerpes aurifrons} ), is a
poorly studied, medium sized bird, whose range extends from Central
America to Texas (Wetmore, 1948; Sauer, Link, Failon, Pardieck, \&
Ziolkowski, 2013; Schroeder, Boal, \& Glasscock, 2013). GFWO numbers are
in decline across their Texas distribution, and are considered a species
of concern in the Texas Wildlife Action Plan (Bender, 2007). As with
other woodpecker species, GFWO act as ecosystem engineers, providing
nesting cavities for SCB throughout their range (Husak \& Maxwell,
1998). Determining the factors that influence the nest site location and
construction of cavities is crucial to not only understand the
conservation needs of GFWO, but also for the conservation and basic
ecology of SCB that may rely on the cavities created by GFWO.

To investigate relationships between the GFWO and local SCB nesting
successes, we conducted an observational study on GFWO nesting success
(\selectlanguage{english}[?] 1 fledgling) in relation to nesting site locations, home range sizes,
local insect biomass, and cavity construction, along with the nesting
success of the four most common SCB in our study area, the Black-crested
Titmouse (BCTI; \emph{Baeolophus atricristatus} ), Ash-throated
Flycatcher (ATFL; \emph{Myiarchus cinerascens} ), Brown-crested
Flycatcher (BCFL; \emph{Myiarchus tyrannulus} ), and Bewick's Wren
(BEWR;\emph{Thryomanes bewickii} ) in the southern Texas Tamaulipan
Brushlands (Baumgardt, Morrison, Brennan, Pierce, \& Campbell, 2019).

The objectives of our study were to determine 1) the role of insect
availability in nest site location and home range size of GFWO, 2) the
role of nest metrics (e.g. DBH, vegetation cover) in the nesting success
of GFWO and the four species of SCB, and 3) if SCB cavity selection and
nesting success differed between abandoned woodpecker cavities and
natural cavities. We predicted 1) insect abundance would be greater at
GFWO occupied sites versus GFWO unoccupied sites and that home range
size would be negatively correlated with the availability of insect
orders commonly eaten by birds, 2) the same cavity metrics would
influence nest success in both GFWO and SCB species and 3) that SCB
would tend to nest in, and have higher nest success in abandoned
woodpecker cavities compared to natural cavities, and that abandoned
woodpecker cavities would share characteristics making them more
suitable for nesting birds, compared to natural cavities.

\textbf{2. MATERIALS AND METHODS}

\textbf{2.1 Study Area}

Our study was conducted on the East Foundation's \textasciitilde{}61,000
ha San Antonio Viejo (SAV) ranch located in Jim Hogg and Starr counties,
\textasciitilde{}25 km south of Hebbronville, south Texas. This area is
representative of the Tamaulipan/Mezquital Thornscrub ecological region
containing unique plants and animal communities within brush covered
dunes, grasslands punctuated with clusters of trees, and open woods of
mesquite (\emph{Prosopsis glandulosa} ). Annual rainfall during the
study year (2019) for this region was \textasciitilde{}30 cm and the
mean temperature during the breeding season (March - July) was
\textasciitilde{}27.8deg C (PRISM Climate Group 2019), similar to the 30
year norm for this region (PRISM Climate Group 2019). The SAV supports
approximately 70 residential bird species and 45 migratory species
(Baumgardt et al., 2019).

\textbf{2.2 Nest Location and Monitoring}

We used the East Foundation's extensive long-term breeding bird dataset,
constructed over 6 years, to create a heat map of areas most likely to
contain nesting GFWO (Baumgardt et al., 2019). We then used the Point
Density tool in ArcGIS version 10.3 (Environmental Systems Research
Institute, Redlands, CA, USA) to take a 500 m2 fishnet sample, and
interpolate density values across our study location. Within areas of
high GFWO density, we placed 12 1-km\textsuperscript{2} survey plots
(Figure S1) and from mid-April to late May, 2019 we visited each plot
four times using the spot mapping technique to locate nesting GFWO
(Martin \& Geupel, 1993).

After locating GFWO nests, we searched 150 m\textsuperscript{2} grids
centered around each nest every 3-5 days between April and July 2019 to
document active SCB nests (Rodewald, 2004). To select GFWO unoccupied
sites, we placed 150m\textsuperscript{2} grids 300 m away from occupied
sites that had the same vegetation association but no observed GFWO
activity (sightings, calling, drilling, foraging, and nesting) and
searched for SCB nests in the same way. The vegetation associations were
determined by the East Foundation's hierarchical vegetation
classification system, created in 2011-2012 where a vegetation
association was defined by the dominant and subdominant species
(Snelgrove, Dube, Skow \& Engeling, 2013). To determine SCB nesting
tendencies and any differences in cavity metrics between abandoned
woodpecker cavities and natural cavities, we recorded and monitored all
empty cavities we found in each grid throughout the breeding season.

We monitored each SCB and GFWO nest every 2-5 days to determine nest
success; a nest was considered successful if \selectlanguage{english}[?]1 fledgling was observed
outside the nest. After fledging, we measured the following nest metrics
that have historically been predictors of cavity nesting success: the
height of the nest measured from the center of the cavity opening to the
base of the tree (height), the tree's DBH, diameter of the cavity
opening (opening), the depth of the cavity (depth), and decay ranking
(decay), where a rank of one indicated a live tree and rank seven
indicated a dead tree with no branches, bark, and soft stem (Dobkin,
Pretare, \& Pyle, 1995; Bonar, 2001; Cockle, Martin, \& Wesolowski,
2011; Berl. Edwards, \& Bolsinger, 2015). Because increased vegetation
cover may be detrimental for cavity nesting birds (Schaaf, 2020), we
used 0.5 x 0.5 m2 cover boards to estimate the percentage of vegetation
cover at each cavity (Nudds, 1997; Chotprasertkoon, Pierce, Savini,
Round, Sankamethawee, \& Gale, 2017).

\textbf{2.3 Insect Sampling and Home range delineation}

To determine if GFWO were selecting nesting sites and home range sizes
based on available insects, we compared home range sizes to the
available insect biomass within each sample site. Home range size was
estimated by constructing minimum convex polygons (MCPs) on a randomly
chosen subset of the home ranges (n = 24). We constructed MCPs by
recording male movements over four, 30-minute visits that began after
observing a male leave their nest (\emph{Dudley \& Saab, 2007}). We
recorded 120 observation points for each male and built MCPs using the
minimum bounding geometry tool in ArcGIS version 10.3 (Environmental
Systems Research Institute, Redlands, CA, USA)

Within the same subset of home ranges, along with the associated
unoccupied sites, we quantified the availability of insects with an
array of 11 sweep net sampling locations from the center of the site (0
m) outwards in 15 m increments to 150 m (see Figure S2), visiting each
site once per week from May to mid-July 2019 (Doxon, Davis, \&
Fuhlendorf, 2011). We sorted the insects by order, dried them using an
Elite Eliminator Heater set at 55degC, and weighed them every 24 hours
until their mass stabilized.

\textbf{2.4 Statistical analysis}

\textbf{2.4.1. Insect availability}

We averaged insect mass over the seven visits across sampling locations
within a home range and summed all sampling locations per site to get a
single measure of insect order biomass per site. We used Mann-Whitney U
to determine differences (P = 0.05) in insect abundance between sites
occupied by GFWO and unoccupied sites, and used Spearman's Rho to test
for significant correlations between each insect order's biomass and
each male GFWO's home range size (Field et al., 2012).

\textbf{2.4.2. GFWO Nest Success}

We created logistic regression models in RStudio version 1.15.2, (R Core
Team 2013) with the package \emph{car} (Fox \& Weisberg, 2019) using
recorded cavity metrics to predict GFWO nest success. We considered
variance inflation factors (VIFs) \textgreater{}5 as indicators of
multicollinearity between variables and z-scaled all continuous
variables to account for varying units of measurement (O'Brien, 2007).
To create candidate models, we used the \emph{MuMIn}package (Barton,
2020) in R to generate a model selection table (Burnham \& Anderson,
2002; Field, Miles, \& Field, 2012), and evaluated model fit using AIC
adjusted for small sample sizes (AICc) (Burnham \& Anderson, 2002).
Models that had \selectlanguage{english}[?]10\% of the weight of the top model were considered
candidate models for model averaging (Burnham \& Anderson, 2004;
Mazerolle, 2006). Using the R package \emph{AICcmodavg}(Mazerolle, 2020)
we estimated the parameter coefficients through model averaging and
determined which parameters were significant using P\selectlanguage{english}\emph{[?]} 0.05 and
corresponding confidence intervals.

\textbf{2.4.3 SCB Nest Success}

To compare the structure of abandoned woodpecker cavities to natural
cavities we used Welch's tests for each set of measurements taken on all
cavities encountered (Field et al., 2012). We then followed the same
steps to create species specific logistic regression and model averages
for the four SCB (Nemes, Jonasson, Genell, \& Steineck, 2009; Field et
al., 2012). Observations on the ATFL and the BCFL were combined given
the similarity of their body metrics and life history traits, and
hereafter are referred to as ATBC (Cardiff and Dittmann 2000). We used
the same six cavity metrics, with the addition of whether the nest was
located in an abandoned woodpecker cavity or a natural cavity (cavity
type). As before, we used the R packages \emph{MuMIn}
and\emph{AICcmodavg} to evaluate candidate models and average parameter
coefficients per species.

\textbf{3. RESULTS}

\textbf{3.1 Insects define GFWO localities}

We collectively spent 560 hours recording GFWO activities and found 55
GFWO nests, along with an additional 2,880 observation hours to define
GFWO home ranges. We spent 220 hours collecting insect samples across 24
of these home ranges and 24 unoccupied equivalent ranges, and found that
insect orders Coleoptera (W = 19, P \textless{} 0.001), Orthoptera (W =
13, P \textless{} 0.001), and Hymenoptera (W = 186, P \textless{} 0.036)
had significantly higher masses on GFWO occupied sites than unoccupied
sites. All other insect orders were not significantly different.

GFWO home range sizes were negatively correlated with the same three
orders of insects, Coleoptera (P \textless{} 0.001, rho = -0.74, n =
24), Orthoptera (P = 0.007, rho = -0.55, n = 24), and Hymenoptera (P =
0.009, rho = -0.53, n = 24) (see Figure 1). The biomass of Phasmatodea
was positively correlated (P = 0.045, rho = 0.41, n = 24) with GFWO home
range size, and all other insect orders were not significantly
correlated.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}

\textbf{Figure 1:} Scatter plots of Golden-fronted woodpecker home range
size (m\textsuperscript{2}) correlated with average mass (g) of
significant insect orders. Shaded areas represent 95\% confidence
intervals. Data collected with sweep nets on the San Antonio Viejo
Ranch, East Foundation in south Texas, during the summer of 2019.

\textbf{3.2 GFWO nest success}

The mean height for a GFWO cavity within our study was 2.3 m \selectlanguage{ngerman}± 0.26, the
mean DBH of the nesting tree was 52 cm ± 6.2, the mean cavity diameter
was 9 cm ± 0.8, the mean depth was 7 cm ± 0.7, and the mean vegetation
cover was 43\% ± 6.3. Over 25\% of GFWO nests were in trees with decay
class 1 (Table 1).

\textbf{Table 1:} Nesting tree decay (1 = live tree, 7 = dead, decayed
tree), for each cavity nesting bird found within the study. Count and
percent of that species within each decay rank are shown for each
species of secondary cavity nesting bird, along with the primary cavity
nesting bird, the Golden-fronted woodpecker. The data on the
Ash-throated and Brown-crested Flycatchers were combined due to similar
life history traits between species. Data was collected on the San
Antonio Viejo Ranch, East Foundation in south Texas during the summer of
2019.\selectlanguage{english}
\begin{longtable}[]{@{}llllllll@{}}
\toprule
& Decay & Decay & Decay & Decay & Decay & Decay & Decay\tabularnewline
Species & 1 (\%) & 2 (\%) & 3 (\%) & 4 (\%) & 5 (\%) & 6 (\%) & 7
(\%)\tabularnewline
Ash-throated/Brown-crested Flycatcher & 14 (13.7) & 11 (10.8) & 16
(15.7) & 23 (22.5) & 19 (18.6) & 16 (15.7) & 3 (2.9)\tabularnewline
Black-crested Titmouse & 7 (17.9) & 5 (12.8) & 5 (12.8) & 3 (7.7) & 10
(25.6) & 6 (15.4) & 3 (7.7)\tabularnewline
Bewick's Wren & 16 (20.3) & 10 (12.7) & 13 (16.5) & 15 (19) & 14 (17.8)
& 11 (13.9) & 0 (0)\tabularnewline
Golden-fronted Woodpecker & 14 (25.5) & 8 (14.5) & 7 (12.7) & 4 (7.3) &
7 (12.7) & 9 (16.4) & 6 (10.9)\tabularnewline
\bottomrule
\end{longtable}

No VIFs were \textgreater{}5, thus all predictors were entered into the
global model (see Table S1 for candidate model selection). Model
averaging suggested that GFWO nests were less likely to be successful as
decay increased (\selectlanguage{greek}β \selectlanguage{english}= -0.91), and were more likely to be successful as
vegetation cover increased (\selectlanguage{greek}β \selectlanguage{english}= 0.10) (Table 2). Looking at the
magnitude of effect, decay was nearly ten times stronger at predicting
successful nests for GFWO than vegetation cover, though both were
significant. Notably, with every unit increase in decay (ranked 1-7)
nest success for the GFWO dropped 0.41.\selectlanguage{english}
\begin{longtable}[]{@{}llllllllll@{}}
\toprule
& \textbf{Table 2:} Model averaged estimates with 95\% confidence
intervals (CI) for variables retained in the candidate model sets that
predicted cavity nesting bird nesting success. All continuous variables
used to create candidate models were z-scaled. Decay was ranked 1 = live
tree, 7 = dead, decayed tree. Cavity Type = whether the nest was located
in an abandoned woodpecker cavity or a naturally occurring one, DBH =
diameter of the nesting tree at breast height. Flycatchers = combined
observations of Ash-throated and Brown-crested flycatchers. Data was
collected on the San Antonio Viejo Ranch, East Foundation in south Texas
during the summer of 2019. Bootstrapping was used to obtain CI. SE is
standard error and bolded variables are significant (P \textless{} 0.05)
& \textbf{Table 2:} Model averaged estimates with 95\% confidence
intervals (CI) for variables retained in the candidate model sets that
predicted cavity nesting bird nesting success. All continuous variables
used to create candidate models were z-scaled. Decay was ranked 1 = live
tree, 7 = dead, decayed tree. Cavity Type = whether the nest was located
in an abandoned woodpecker cavity or a naturally occurring one, DBH =
diameter of the nesting tree at breast height. Flycatchers = combined
observations of Ash-throated and Brown-crested flycatchers. Data was
collected on the San Antonio Viejo Ranch, East Foundation in south Texas
during the summer of 2019. Bootstrapping was used to obtain CI. SE is
standard error and bolded variables are significant (P \textless{} 0.05)
& \textbf{Table 2:} Model averaged estimates with 95\% confidence
intervals (CI) for variables retained in the candidate model sets that
predicted cavity nesting bird nesting success. All continuous variables
used to create candidate models were z-scaled. Decay was ranked 1 = live
tree, 7 = dead, decayed tree. Cavity Type = whether the nest was located
in an abandoned woodpecker cavity or a naturally occurring one, DBH =
diameter of the nesting tree at breast height. Flycatchers = combined
observations of Ash-throated and Brown-crested flycatchers. Data was
collected on the San Antonio Viejo Ranch, East Foundation in south Texas
during the summer of 2019. Bootstrapping was used to obtain CI. SE is
standard error and bolded variables are significant (P \textless{} 0.05)
& \textbf{Table 2:} Model averaged estimates with 95\% confidence
intervals (CI) for variables retained in the candidate model sets that
predicted cavity nesting bird nesting success. All continuous variables
used to create candidate models were z-scaled. Decay was ranked 1 = live
tree, 7 = dead, decayed tree. Cavity Type = whether the nest was located
in an abandoned woodpecker cavity or a naturally occurring one, DBH =
diameter of the nesting tree at breast height. Flycatchers = combined
observations of Ash-throated and Brown-crested flycatchers. Data was
collected on the San Antonio Viejo Ranch, East Foundation in south Texas
during the summer of 2019. Bootstrapping was used to obtain CI. SE is
standard error and bolded variables are significant (P \textless{} 0.05)
& \textbf{Table 2:} Model averaged estimates with 95\% confidence
intervals (CI) for variables retained in the candidate model sets that
predicted cavity nesting bird nesting success. All continuous variables
used to create candidate models were z-scaled. Decay was ranked 1 = live
tree, 7 = dead, decayed tree. Cavity Type = whether the nest was located
in an abandoned woodpecker cavity or a naturally occurring one, DBH =
diameter of the nesting tree at breast height. Flycatchers = combined
observations of Ash-throated and Brown-crested flycatchers. Data was
collected on the San Antonio Viejo Ranch, East Foundation in south Texas
during the summer of 2019. Bootstrapping was used to obtain CI. SE is
standard error and bolded variables are significant (P \textless{} 0.05)
& \textbf{Table 2:} Model averaged estimates with 95\% confidence
intervals (CI) for variables retained in the candidate model sets that
predicted cavity nesting bird nesting success. All continuous variables
used to create candidate models were z-scaled. Decay was ranked 1 = live
tree, 7 = dead, decayed tree. Cavity Type = whether the nest was located
in an abandoned woodpecker cavity or a naturally occurring one, DBH =
diameter of the nesting tree at breast height. Flycatchers = combined
observations of Ash-throated and Brown-crested flycatchers. Data was
collected on the San Antonio Viejo Ranch, East Foundation in south Texas
during the summer of 2019. Bootstrapping was used to obtain CI. SE is
standard error and bolded variables are significant (P \textless{} 0.05)
& \textbf{Table 2:} Model averaged estimates with 95\% confidence
intervals (CI) for variables retained in the candidate model sets that
predicted cavity nesting bird nesting success. All continuous variables
used to create candidate models were z-scaled. Decay was ranked 1 = live
tree, 7 = dead, decayed tree. Cavity Type = whether the nest was located
in an abandoned woodpecker cavity or a naturally occurring one, DBH =
diameter of the nesting tree at breast height. Flycatchers = combined
observations of Ash-throated and Brown-crested flycatchers. Data was
collected on the San Antonio Viejo Ranch, East Foundation in south Texas
during the summer of 2019. Bootstrapping was used to obtain CI. SE is
standard error and bolded variables are significant (P \textless{} 0.05)
& \textbf{Table 2:} Model averaged estimates with 95\% confidence
intervals (CI) for variables retained in the candidate model sets that
predicted cavity nesting bird nesting success. All continuous variables
used to create candidate models were z-scaled. Decay was ranked 1 = live
tree, 7 = dead, decayed tree. Cavity Type = whether the nest was located
in an abandoned woodpecker cavity or a naturally occurring one, DBH =
diameter of the nesting tree at breast height. Flycatchers = combined
observations of Ash-throated and Brown-crested flycatchers. Data was
collected on the San Antonio Viejo Ranch, East Foundation in south Texas
during the summer of 2019. Bootstrapping was used to obtain CI. SE is
standard error and bolded variables are significant (P \textless{} 0.05)
& \textbf{Table 2:} Model averaged estimates with 95\% confidence
intervals (CI) for variables retained in the candidate model sets that
predicted cavity nesting bird nesting success. All continuous variables
used to create candidate models were z-scaled. Decay was ranked 1 = live
tree, 7 = dead, decayed tree. Cavity Type = whether the nest was located
in an abandoned woodpecker cavity or a naturally occurring one, DBH =
diameter of the nesting tree at breast height. Flycatchers = combined
observations of Ash-throated and Brown-crested flycatchers. Data was
collected on the San Antonio Viejo Ranch, East Foundation in south Texas
during the summer of 2019. Bootstrapping was used to obtain CI. SE is
standard error and bolded variables are significant (P \textless{}
0.05)\tabularnewline
& & & & & & & 95\% CI & 95\% CI & 95\% CI\tabularnewline
& & Model averaged \selectlanguage{greek}β & SE & P & P & Lower & Lower & Upper &
Upper\tabularnewline
\textbf{Golden-fronted woodpecker (n = 55)} & \textbf{Golden-fronted
woodpecker (n = 55)} & & & & & & & &\tabularnewline
\textbf{Decay} & \textbf{Decay} & \textbf{-0.91} & \textbf{0.41} &
\textbf{0.015} & \textbf{0.015} & \textbf{-1.71} & \textbf{-1.71} &
\textbf{-0.1} & \textbf{-0.1}\tabularnewline
\textbf{Vegetation Cover} & \textbf{Vegetation Cover} & \textbf{0.09} &
\textbf{0.05} & \textbf{0.028} & \textbf{0.028} & \textbf{-0.001} &
\textbf{-0.001} & \textbf{0.19} & \textbf{0.19}\tabularnewline
DBH & DBH & 0.12 & 0.3 & 0.362 & 0.362 & -0.48 & -0.48 & 0.71 &
0.71\tabularnewline
Diameter of Opening & Diameter of Opening & 0.05 & 0.33 & 0.445 & 0.445
& -0.59 & -0.59 & 0.69 & 0.69\tabularnewline
Height & Height & 0.02 & 0.28 & 0.472 & 0.472 & -0.52 & -0.52 & 0.56 &
0.56\tabularnewline
Depth & Depth & 0.02 & 0.18 & 0.46 & 0.46 & -0.33 & -0.33 & 0.37 &
0.37\tabularnewline
\textbf{Bewick's wren (n = 79)} & \textbf{Bewick's wren (n = 79)} & & &
& & & & &\tabularnewline
Decay & Decay & -0.03 & 0.14 & 0.421 & 0.421 & -0.30 & -0.30 & 0.24 &
0.24\tabularnewline
\textbf{Vegetation Cover} & \textbf{Vegetation Cover} & \textbf{0.06} &
\textbf{0.02} & \textbf{0.002} & \textbf{0.002} & \textbf{0.02} &
\textbf{0.02} & \textbf{0.10} & \textbf{0.10}\tabularnewline
DBH & DBH & 0.63 & 0.49 & 0.104 & 0.104 & -0.34 & -0.34 & 1.59 &
1.59\tabularnewline
Diameter of Opening & Diameter of Opening & -0.04 & 0.18 & 0.408 & 0.408
& -0.40 & -0.40 & 0.31 & 0.31\tabularnewline
Height & Height & 0.01 & 0.17 & 0.480 & 0.480 & -0.34 & -0.34 & 0.33 &
0.33\tabularnewline
Depth & Depth & \textless{} 0.01 & 0.17 & 0.500 & 0.500 & -0.34 & -0.34
& 0.34 & 0.34\tabularnewline
\textbf{Cavity Type (natural)} & \textbf{Cavity Type (natural)} &
\textbf{1.92} & \textbf{0.95} & \textbf{0.023} & \textbf{0.023} &
\textbf{0.05} & \textbf{0.05} & \textbf{3.78} &
\textbf{3.78}\tabularnewline
\textbf{Flycatchers (n = 102)} & \textbf{Flycatchers (n = 102)} & & & &
& & & &\tabularnewline
\textbf{Decay} & \textbf{Decay} & \textbf{-0.40} & \textbf{0.19} &
\textbf{0.018} & \textbf{0.018} & \textbf{-0.77} & \textbf{-0.77} &
\textbf{-0.03} & \textbf{-0.03}\tabularnewline
Vegetation Cover & Vegetation Cover & \textless{} 0.01 & 0.01 & 0.383 &
0.383 & -0.01 & -0.01 & 0.01 & 0.01\tabularnewline
DBH & DBH & \textless{} 0.01 & 0.14 & 0.498 & 0.498 & -0.27 & -0.27 &
0.27 & 0.27\tabularnewline
Diameter of Opening & Diameter of Opening & -0.63 & 0.39 & 0.056 & 0.056
& -1.40 & -1.40 & 0.14 & 0.14\tabularnewline
Height & Height & 0.06 & 0.19 & 0.385 & 0.385 & -0.32 & -0.32 & 0.43 &
0.43\tabularnewline
Depth & Depth & -0.05 & 0.17 & 0.388 & 0.388 & -0.39 & -0.39 & 0.29 &
0.29\tabularnewline
\textbf{Cavity Type (natural)} & \textbf{Cavity Type (natural)} &
\textbf{3.54} & \textbf{0.77} & \textbf{\textless{} 0.001} &
\textbf{\textless{} 0.001} & \textbf{2.02} & \textbf{2.02} &
\textbf{5.05} & \textbf{5.05}\tabularnewline
\textbf{Black-crested titmouse (n = 39)} & \textbf{Black-crested
titmouse (n = 39)} & & & & & & & &\tabularnewline
\textbf{Decay} & \textbf{Decay} & \textbf{-1.02} & \textbf{0.41} &
\textbf{0.008} & \textbf{0.008} & \textbf{-1.83} & \textbf{-1.83} &
\textbf{-0.21} & \textbf{-0.21}\tabularnewline
Vegetation Cover & Vegetation Cover & 0.03 & 0.03 & 0.180 & 0.180 &
-0.03 & -0.03 & 0.08 & 0.08\tabularnewline
DBH & DBH & 0.07 & 0.29 & 0.403 & 0.403 & -0.49 & -0.49 & 0.63 &
0.63\tabularnewline
Diameter of Opening & Diameter of Opening & 0.02 & 0.21 & 0.460 & 0.460
& -0.39 & -0.39 & 0.43 & 0.43\tabularnewline
Height & Height & -0.05 & 0.29 & 0.429 & 0.429 & -0.63 & -0.63 & 0.52 &
0.52\tabularnewline
Depth & Depth & \textless{} 0.01 & 0.21 & 0.497 & 0.497 & -0.42 & -0.42
& 0.42 & 0.42\tabularnewline
\textbf{Cavity Type (natural)} & \textbf{Cavity Type (natural)} &
\textbf{2.53} & \textbf{1.28} & \textbf{0.025} & \textbf{0.025} &
\textbf{0.03} & \textbf{0.03} & \textbf{5.04} &
\textbf{5.04}\tabularnewline
& \emph{Note:} Candidate models were chosen if they had an AICc weight
[?]10\% of the AICc weight of the top model. & \emph{Note:} Candidate
models were chosen if they had an AICc weight [?]10\% of the AICc weight
of the top model. & \emph{Note:} Candidate models were chosen if they
had an AICc weight [?]10\% of the AICc weight of the top model. &
\emph{Note:} Candidate models were chosen if they had an AICc weight
[?]10\% of the AICc weight of the top model. & \emph{Note:} Candidate
models were chosen if they had an AICc weight [?]10\% of the AICc weight
of the top model. & \emph{Note:} Candidate models were chosen if they
had an AICc weight [?]10\% of the AICc weight of the top model. &
\emph{Note:} Candidate models were chosen if they had an AICc weight
[?]10\% of the AICc weight of the top model. & \emph{Note:} Candidate
models were chosen if they had an AICc weight [?]10\% of the AICc weight
of the top model. & \emph{Note:} Candidate models were chosen if they
had an AICc weight [?]10\% of the AICc weight of the top
model.\tabularnewline
\bottomrule
\end{longtable}

\textbf{3.3 Cavities and SCB nesting success}

Across all cavities found, whether a nest had been initiated in it or
not, abandoned woodpecker cavities were significantly different than
natural cavities: abandoned woodpecker cavities were built 42\% higher
in less decayed trees with 20\% larger DBH than natural cavities and had
18\% higher vegetation cover (Table 3). The size of the entrance hole
and the depth of the cavity were not significantly different between
nest types.\selectlanguage{english}
\begin{longtable}[]{@{}lllllllllll@{}}
\toprule
\textbf{Table 3:} Results of Welch's t-test comparing differences
between abandoned woodpecker cavities (AWC) and natural cavities (NC).
DBH = diameter of the nesting tree at breast height, Decay (1 = live
tree, 7 = dead, decayed tree). Data was collected on the SAV Ranch, East
Foundation during 2019. & \textbf{Table 3:} Results of Welch's t-test
comparing differences between abandoned woodpecker cavities (AWC) and
natural cavities (NC). DBH = diameter of the nesting tree at breast
height, Decay (1 = live tree, 7 = dead, decayed tree). Data was
collected on the SAV Ranch, East Foundation during 2019. & \textbf{Table
3:} Results of Welch's t-test comparing differences between abandoned
woodpecker cavities (AWC) and natural cavities (NC). DBH = diameter of
the nesting tree at breast height, Decay (1 = live tree, 7 = dead,
decayed tree). Data was collected on the SAV Ranch, East Foundation
during 2019. & \textbf{Table 3:} Results of Welch's t-test comparing
differences between abandoned woodpecker cavities (AWC) and natural
cavities (NC). DBH = diameter of the nesting tree at breast height,
Decay (1 = live tree, 7 = dead, decayed tree). Data was collected on the
SAV Ranch, East Foundation during 2019. & \textbf{Table 3:} Results of
Welch's t-test comparing differences between abandoned woodpecker
cavities (AWC) and natural cavities (NC). DBH = diameter of the nesting
tree at breast height, Decay (1 = live tree, 7 = dead, decayed tree).
Data was collected on the SAV Ranch, East Foundation during 2019. &
\textbf{Table 3:} Results of Welch's t-test comparing differences
between abandoned woodpecker cavities (AWC) and natural cavities (NC).
DBH = diameter of the nesting tree at breast height, Decay (1 = live
tree, 7 = dead, decayed tree). Data was collected on the SAV Ranch, East
Foundation during 2019. & \textbf{Table 3:} Results of Welch's t-test
comparing differences between abandoned woodpecker cavities (AWC) and
natural cavities (NC). DBH = diameter of the nesting tree at breast
height, Decay (1 = live tree, 7 = dead, decayed tree). Data was
collected on the SAV Ranch, East Foundation during 2019. & \textbf{Table
3:} Results of Welch's t-test comparing differences between abandoned
woodpecker cavities (AWC) and natural cavities (NC). DBH = diameter of
the nesting tree at breast height, Decay (1 = live tree, 7 = dead,
decayed tree). Data was collected on the SAV Ranch, East Foundation
during 2019. & \textbf{Table 3:} Results of Welch's t-test comparing
differences between abandoned woodpecker cavities (AWC) and natural
cavities (NC). DBH = diameter of the nesting tree at breast height,
Decay (1 = live tree, 7 = dead, decayed tree). Data was collected on the
SAV Ranch, East Foundation during 2019. & \textbf{Table 3:} Results of
Welch's t-test comparing differences between abandoned woodpecker
cavities (AWC) and natural cavities (NC). DBH = diameter of the nesting
tree at breast height, Decay (1 = live tree, 7 = dead, decayed tree).
Data was collected on the SAV Ranch, East Foundation during 2019. &
\textbf{Table 3:} Results of Welch's t-test comparing differences
between abandoned woodpecker cavities (AWC) and natural cavities (NC).
DBH = diameter of the nesting tree at breast height, Decay (1 = live
tree, 7 = dead, decayed tree). Data was collected on the SAV Ranch, East
Foundation during 2019.\tabularnewline
& & & & & & AWC & AWC & & NC & NC\tabularnewline
& & P & & t & & Average & (\selectlanguage{ngerman}±) & & Average & (\selectlanguage{ngerman}±)\tabularnewline
\textbf{Decay} & \textbf{Decay} & \textbf{\textless{} 0.001} & &
\textbf{9.3} & & \textbf{3} & \textbf{0.3} & & \textbf{4} &
\textbf{0.3}\tabularnewline
\textbf{Vegetation Cover (\%)} & \textbf{Vegetation Cover (\%)} &
\textbf{\textless{} 0.001} & & \textbf{6.4} & & \textbf{50} &
\textbf{1.6} & & \textbf{41} & \textbf{1.8}\tabularnewline
\textbf{DBH (cm)} & & \textbf{\textless{} 0.001} & & \textbf{8.3} & &
\textbf{63.1} & \textbf{1.5} & & \textbf{50.2} &
\textbf{1.2}\tabularnewline
Opening (cm) & Opening (cm) & 0.321 & & 20.1 & & 13.6 & 4.2 & & 15.2 &
6.7\tabularnewline
\textbf{Height (m)} & \textbf{Height (m)} & \textbf{\textless{} 0.001} &
& \textbf{22.1} & & \textbf{1.9} & \textbf{0.2} & & \textbf{1.1} &
\textbf{0.15}\tabularnewline
Depth (cm) & Depth (cm) & 0.297 & & 9.7 & & 20.2 & 5.7 & & 18.4 &
7.3\tabularnewline
\bottomrule
\end{longtable}

\par\null

Model averaging for the BEWR suggested that cavity type was 15 times
stronger at predicting successful nests than vegetation cover, though
both were significant (Table 2; see Table S1 for candidate model
selection), with nests more likely to be successful as vegetation cover
increased (\selectlanguage{greek}β \selectlanguage{english}= 0.06), and if nests were built in an abandoned woodpecker
cavity over a natural cavity (\selectlanguage{greek}β \selectlanguage{english}= 0.95). Model averaging for both the
BCTI and the ATBC suggested that decay and the cavity type were
significant predictors for nest success. As with the GFWO, with every
unit increase in decay, nest success dropped 0.19 for ATBC and 0.41 for
BCTI. Again, cavity type was the strongest predictor; cavity type was 3
times stronger at predicting nest success than decay for the BCTI, and
was 4 times stronger than decay for the ATBC. Across SCB species, cavity
type was the strongest predictor of nest success.

\textbf{4. DISCUSSION}

Decades of field observations in a range of bird species suggest the
importance of insects to birds during the breeding season, as protein
demands are increased while producing eggs and provisioning nestlings
(\emph{Capinera, 2011} ,\emph{Vitz \& Rodewald, 2012}). We identify
correlations between food resources and GFWO nest site location and home
range size, along with nest cavity characteristics that facilitate
successful broods and reveal the importance of abandoned woodpecker
cavities for secondary cavity nesting birds. Additionally, our results
suggest a novel trade-off between excavating live trees versus
dead/decaying trees, evident in the differences in nest success between
natural cavities and abandoned woodpecker cavities.

\textbf{Resource driven site location}All recorded orders of insects
collected within our study were found at all occupied and unoccupied
site types, though not every insect order was found at each sweep
netting location, nor at every visit. Previous literature has indicated
that Coleoptera and Hymenoptera are in high proportions of woodpecker
diets (Beckwith \& Bull, 1985; Hess \& James, 1998; Fayt, Machmer, \&
Steeger, 2005; Pechacek \& Kristin, 2010), and as we predicted in our
first objective, the biomass of both of these insect orders were higher
around GFWO nests than unoccupied sites and increases in their biomass
corresponded with decreased GFWO home ranges, up to 15,000
m\textsuperscript{2}. In addition, we found similar relationships
between Orthoptera and GFWO sites and home ranges.

Our findings indicate that resource availability (e.g. insect biomass)
may be driving the location and home range sizes of this ecosystem
engineer, as GFWO nests were located in areas that corresponded with
insect availability, and home ranges shrank in correlation with
increases in those same insect orders. This is in accordance with
previous literature which indicates that woodpeckers reduce their
defended areas when resources were abundant, and chose nesting sites
based on resource availability (Pasinelli, 2000; Tingley, Wilkerson,
Bond, Howell, \& Siegel., 2014). The differences we found in insect
biomass between occupied and unoccupied sites were most likely due to
fine scale variation in vegetation and water availability
indistinguishable by our vegetation associations (Huang, Zhao, \& von
Gadow, 2015).

\textbf{Interconnected nesting success}

In our second and third objectives, we predicted that the same cavity
metrics that influenced GFWO nest success would also influence SCB, and
that SCB would have higher nest success in abandoned woodpecker
cavities. As predicted, all SCB had higher nest success rates in
abandoned woodpecker cavities than in natural cavities and cavity type
was the strongest predictor for all species, with the BEWR having the
least impact, followed by the BCTI, and largest influence on ATBC.
Additionally, GFWO had higher success in trees with lower decay and
higher vegetation cover, which was mirrored in SCB; BCTI and ATBC were
more likely to produce fledglings in trees with low decay, and BEWR were
more likely to produce fledglings in cavities with high vegetation
cover. The BEWR was the only species not impacted by decay, potentially
explained by its generalistic nesting behavior (\emph{Taylor, 2003}). We
observed successful BEWR nests built in metal pipes or direct sun, thus
experiencing wide temperature swings throughout the day, indicating that
unstable nesting environments may be a deterrent for other cavity
nesting birds, but not this species.

Also in line with our third objective, we predicted that abandoned
woodpecker cavities would share characteristics making them better
nesting cavities than natural ones. To this, SCB within our study had
higher success rates within abandoned woodpecker cavities (81-93\%),
than in natural cavities (41-56\%). The structure of abandoned
woodpecker cavities present on our sites were distinctly different from
their natural counterparts; on average they were significantly higher in
trees, of lower decay, smaller DBH, and increased vegetation cover, all
characteristics that protect eggs and fledglings from shifting internal
temperatures and predation (Copeyon, 1990; Ojeda, Suarez, \& Kitzberger,
2007;\emph{Pakkala et al., 2019}). Considering that SCB are reliant on
pre-existing cavities to create their nests, the factors that drive the
creation and design of woodpecker cavities may then dictate the success
of local SCB.

\textbf{Tree decay and vegetation cover: a possible role for
temperature}

We found a higher than expected number of GFWO nests within live trees.
Previous literature on woodpecker nesting ecology has indicated a
preference for excavating cavities in partially to fully decayed trees,
which require less energy and time than dense, live wood (\emph{Conner,
Miller, \& Adkisson, 1976}; Cockle et al., 2011; Blanc \& Martin, 2012).
However, these studies have focused on temperate regions such as
northwestern, northeastern United States, Canada, and European countries
where breeding season temperature rarely exceeds 35\selectlanguage{ngerman}° C and occasionally
reach freezing during the early spring (\emph{Conner et al.,
1976};\emph{Blanc \& Martin, 2012};\emph{Seavy, Burnett, \& Taille,
2012}). In contrast, the mean breeding season temperature at our study
site in southern Texas was 27.8° C and daytime temperatures frequently
reached over 42.2° C Currently, there is little information on how
cavity nesting birds regulate nest temperature, though some species may
modulate incubation initiation and duration in relation to temperature
(Coe, Beck, Chin, Jachowski, \& Hopkins, 2015; Simmonds, Sheldon,
Coulson, \& Cole, 2017) and there are reports of GFWO clinging to the
sides of the cavity which could be an attempt to reduce heat transfer
(Skutch, 1969). Nest temperature is also affected by nest site location
and cavity design (although not always) (Butler, Whitman \& Dufty, 2009;
Zingg, Arlettaz \& Schaub, 2010; Sonnenberg, Branch, Benedict, Pitera \&
Pravosudov, 2020).

Tree decay, in particular, affects thermoregulation of the nest cavity,
in that live trees -with higher water content- provide greater
insulation against high and low temperature extremes (Grüebler, Widmer,
Korner-Nievergelt \& Naef- Daenzer, 2014). However, the same trait that
makes live trees good insulators also makes them more costly to
excavate; on average, live trees are denser than partially dead or
decaying trees. Therefore, these birds may be facing an energetic
trade-off; whether to put additional effort into excavating a dense live
tree- which has higher water content and is better able to
thermoregulate eggs and nestlings- or save time and energy by excavating
a less stable decayed tree and risk eggs and nestlings overheating.

This possible role for temperature in nest site selection and structure
is further strengthened by the trend we observed in vegetation cover,
with cavity nesters like the GFWO and the BEWR having higher success in
cavities with increased vegetation cover. While the effect size for
vegetation (\selectlanguage{greek}β \selectlanguage{english}ranged from 0.02 to 0.05) seems small at first, across the
large range of possibilities for cover (1-100) this variable showed a
strong effect. For example, with a 15 percent increase in vegetation
cover, the effect size for the BEWR grew to 0.30 and the same increase
in vegetation cover for the GFWO resulted in an effect size of 0.75,
rivaling that of stronger predictors such as decay and cavity cover.
Again, these results contrast with previous literature on cavity nesters
which indicated a preference for exposed cavities due to increased
visibility of approaching predators (Mannan et al., 1980; Li \& Martin,
1991; Loye \& Carroll, 1998; Newlon, 2005; Jusino et al., 2016).
Vegetated cavities in this region may provide increased shade and thus
reduced internal temperatures, resulting in another tradeoff, one
between temperature regulation and predation.

\textbf{Conclusion}

Here we evaluated the link between food resources and an ecosystem
engineer, and the subsequent influence of this engineer on local
secondary cavity nesters. We observed that GFWO nest site location and
home range size was positively correlated to biomass of the same three
orders of insects that make up large proportions of their diet, and that
all SCB had higher nest success in abandoned woodpecker cavities than
natural cavities. Thus, GFWO nest in areas with abundant food and SCB
reap the benefits of the stable cavities they leave behind, along with
opportunistically high insect loads. Our results also suggest that GFWO
nest characteristics may influence nest success in ways that differ from
more temperate species, indicating future research avenues into
energetics and predation pressure tradeoffs in high temperature regions.
Additionally, management for woodpeckers and SCB in southern Texas
should not focus on the availability of snags (a common management
strategy for woodpeckers in temperate climates), but on the number of
live trees with a DBH wide enough for nesting.

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\textbf{Supplementary}

Variables used throughout manuscript and supplementary materials:

\begin{itemize}
\tightlist
\item
  height = height of the nest measured from the center of the cavity
  opening to the base of tree
\item
  DBH = diameter at breast height of the tree
\item
  opening = diameter of the cavity opening
\item
  depth = depth of the cavity
\item
  decay = decay ranking, where a rank of one indicated a live tree and
  rank seven indicated a dead tree with no branches, bark, and soft stem
\item
  vegetation cover = percent of vegetation covering the cavity opening.
\item
  Cavity Type = whether it was in an abandoned woodpecker cavity or a
  natural cavity.
\end{itemize}

S. Table 1: Candidate Models for Model Averaging.\selectlanguage{english}
\begin{longtable}[]{@{}llllllllll@{}}
\toprule
\textbf{Bewick's Wren (n = 79)} & \textbf{Bewick's Wren (n = 79)} &
\textbf{Bewick's Wren (n = 79)} & & & & logLik & AICc & \selectlanguage{greek}Δ\selectlanguage{english}AICc &
Weight\tabularnewline
& M1: Decay + vegetation cover + Cavity Type & M1: Decay + vegetation
cover + Cavity Type & M1: Decay + vegetation cover + Cavity Type & & &
-11.672 & 32.520 & 0.000 & 0.185\tabularnewline
& M2: Decay+ Cavity Type & M2: Decay+ Cavity Type & & & & -13.420 &
33.526 & 1.005 & 0.112\tabularnewline
& M3: Decay + vegetation cover + Cavity Type + height & M3: Decay +
vegetation cover + Cavity Type + height & M3: Decay + vegetation cover +
Cavity Type + height & M3: Decay + vegetation cover + Cavity Type +
height & & -11.465 & 34.748 & 2.227 & 0.061\tabularnewline
& M4: Decay + vegetation cover + Cavity Type + DBH & M4: Decay +
vegetation cover + Cavity Type + DBH & M4: Decay + vegetation cover +
Cavity Type + DBH & M4: Decay + vegetation cover + Cavity Type + DBH & &
-11.498 & 34.815 & 2.295 & 0.059\tabularnewline
& M5: Decay + vegetation cover+ Cavity Type + opening & M5: Decay +
vegetation cover+ Cavity Type + opening & M5: Decay + vegetation cover+
Cavity Type + opening & M5: Decay + vegetation cover+ Cavity Type +
opening & & -11.573 & 34.964 & 2.443 & 0.054\tabularnewline
& M6: Decay + vegetation cover + Cavity Type + depth & M6: Decay +
vegetation cover + Cavity Type + depth & M6: Decay + vegetation cover +
Cavity Type + depth & M6: Decay + vegetation cover + Cavity Type + depth
& & -11.650 & 35.117 & 2.597 & 0.050\tabularnewline
& M7: Decay + Cavity Type + DBH & M7: Decay + Cavity Type + DBH & M7:
Decay + Cavity Type + DBH & & & -13.008 & 35.193 & 2.673 &
0.049\tabularnewline
& M8: Decay + Cavity Type + depth & M8: Decay + Cavity Type + depth &
M8: Decay + Cavity Type + depth & & & -13.381 & 35.938 & 3.418 &
0.033\tabularnewline
& M9: Decay + Cavity Type + height & M9: Decay + Cavity Type + height &
M9: Decay + Cavity Type + height & & & -13.412 & 36.001 & 3.481 &
0.032\tabularnewline
& M10: Decay + Cavity Type + opening & M10: Decay + Cavity Type +
opening & M10: Decay + Cavity Type + opening & & & -13.416 & 36.009 &
3.489 & 0.032\tabularnewline
& M11: Decay + vegetation cover & M11: Decay + vegetation cover & M11:
Decay + vegetation cover & & & -15.113 & 36.912 & 4.391 &
0.021\tabularnewline
& M12: Decay + vegetation cover + Cavity Type + DBH + height & M12:
Decay + vegetation cover + Cavity Type + DBH + height & M12: Decay +
vegetation cover + Cavity Type + DBH + height & M12: Decay + vegetation
cover + Cavity Type + DBH + height & M12: Decay + vegetation cover +
Cavity Type + DBH + height & -11.189 & 37.002 & 4.482 &
0.020\tabularnewline
& \emph{Null Model} & \emph{Null Model} & & & & \emph{-47.650} &
\emph{97.35} & \emph{31.3106} & \emph{3E-08}\tabularnewline
\textbf{Ash-throated/Brown-crested Flycatcher (n = 102)} &
\textbf{Ash-throated/Brown-crested Flycatcher (n = 102)} &
\textbf{Ash-throated/Brown-crested Flycatcher (n = 102)} &
\textbf{Ash-throated/Brown-crested Flycatcher (n = 102)} &
\textbf{Ash-throated/Brown-crested Flycatcher (n = 102)} & & logLik &
AICc & \selectlanguage{greek}Δ\selectlanguage{english}AICc & Weight\tabularnewline
& M1: Decay + DBH + Cavity Type + opening & M1: Decay + DBH + Cavity
Type + opening & M1: Decay + DBH + Cavity Type + opening & M1: Decay +
DBH + Cavity Type + opening & & -38.417 & 87.458 & 0.000 &
0.127\tabularnewline
& M2: Decay + Cavity Type + opening & M2: Decay + Cavity Type + opening
& M2: Decay + Cavity Type + opening & & & -39.564 & 87.541 & 0.083 &
0.121\tabularnewline
& M3: Decay + vegetation cover + Cavity Type + opening & M3: Decay +
vegetation cover + Cavity Type + opening & M3: Decay + vegetation cover
+ Cavity Type + opening & M3: Decay + vegetation cover + Cavity Type +
opening & & -39.233 & 89.090 & 1.632 & 0.056\tabularnewline
& M4: Decay + vegetation cover + Cavity Type + DBH + opening & M4: Decay
+ vegetation cover + Cavity Type + DBH + opening & M4: Decay +
vegetation cover + Cavity Type + DBH + opening & M4: Decay + vegetation
cover + Cavity Type + DBH + opening & M4: Decay + vegetation cover +
Cavity Type + DBH + opening & -38.134 & 89.152 & 1.694 &
0.054\tabularnewline
& M5: Decay + Cavity Type + depth + opening & M5: Decay + Cavity Type +
depth + opening & M5: Decay + Cavity Type + depth + opening & M5: Decay
+ Cavity Type + depth + opening & & -39.308 & 89.242 & 1.784 &
0.052\tabularnewline
& M6: Decay + Cavity Type + DBH + height + opening & M6: Decay + Cavity
Type + DBH + height + opening & M6: Decay + Cavity Type + DBH + height +
opening & M6: Decay + Cavity Type + DBH + height + opening & & -38.252 &
89.387 & 1.929 & 0.048\tabularnewline
& M7: Decay + Cavity Type + DBH + depth + opening & M7: Decay + Cavity
Type + DBH + depth + opening & M7: Decay + Cavity Type + DBH + depth +
opening & M7: Decay + Cavity Type + DBH + depth + opening & & -38.261 &
89.406 & 1.948 & 0.048\tabularnewline
& M8: Decay + Cavity Type + DBH & M8: Decay + Cavity Type + DBH & M8:
Decay + Cavity Type + DBH & & & -40.561 & 89.535 & 2.077 &
0.045\tabularnewline
& M9: Decay + Cavity Type + height + opening & M9: Decay + Cavity Type +
height + opening & M9: Decay + Cavity Type + height + opening & M9:
Decay + Cavity Type + height + opening & & -39.455 & 89.535 & 2.077 &
0.045\tabularnewline
& M10: Decay + Cavity Type & M10: Decay + Cavity Type & & & & -41.766 &
89.777 & 2.319 & 0.040\tabularnewline
& M11: Decay + vegetation cover + Cavity Type + depth + opening & M11:
Decay + vegetation cover + Cavity Type + depth + opening & M11: Decay +
vegetation cover + Cavity Type + depth + opening & M11: Decay +
vegetation cover + Cavity Type + depth + opening & M11: Decay +
vegetation cover + Cavity Type + depth + opening & -38.959 & 90.802 &
3.343 & 0.024\tabularnewline
& M12: Decay + vegetation cover + Cavity Type + height + opening & M12:
Decay + vegetation cover + Cavity Type + height + opening & M12: Decay +
vegetation cover + Cavity Type + height + opening & M12: Decay +
vegetation cover + Cavity Type + height + opening & M12: Decay +
vegetation cover + Cavity Type + height + opening & -39.023 & 90.930 &
3.472 & 0.022\tabularnewline
& M13: Decay + vegetation cover + Cavity Type + DBH + height + opening &
M13: Decay + vegetation cover + Cavity Type + DBH + height + opening &
M13: Decay + vegetation cover + Cavity Type + DBH + height + opening &
M13: Decay + vegetation cover + Cavity Type + DBH + height + opening &
M13: Decay + vegetation cover + Cavity Type + DBH + height + opening &
-37.872 & 90.936 & 3.477 & 0.022\tabularnewline
& M14: Decay + vegetation cover + Cavity Type + DBH + depth + opening &
M14: Decay + vegetation cover + Cavity Type + DBH + depth + opening &
M14: Decay + vegetation cover + Cavity Type + DBH + depth + opening &
M14: Decay + vegetation cover + Cavity Type + DBH + depth + opening &
M14: Decay + vegetation cover + Cavity Type + DBH + depth + opening &
-37.957 & 91.106 & 3.647 & 0.020\tabularnewline
& M15: Decay + Cavity Type + DBH + height & M15: Decay + Cavity Type +
DBH + height & M15: Decay + Cavity Type + DBH + height & M15: Decay +
Cavity Type + DBH + height & & -40.277 & 91.178 & 3.720 &
0.020\tabularnewline
& M16: Decay + Cavity Type + depth + height + opening & M16: Decay +
Cavity Type + depth + height + opening & M16: Decay + Cavity Type +
depth + height + opening & M16: Decay + Cavity Type + depth + height +
opening & M16: Decay + Cavity Type + depth + height + opening & -39.162
& 91.209 & 3.751 & 0.019\tabularnewline
& M17: Decay + Cavity Type + DBH + depth + height + opening & M17: Decay
+ Cavity Type + DBH + depth + height + opening & M17: Decay + Cavity
Type + DBH + depth + height + opening & M17: Decay + Cavity Type + DBH +
depth + height + opening & M17: Decay + Cavity Type + DBH + depth +
height + opening & -38.060 & 91.312 & 3.854 & 0.018\tabularnewline
& M18: Decay + vegetation cover + Cavity Type + DBH & M18: Decay +
vegetation cover + Cavity Type + DBH & M18: Decay + vegetation cover +
Cavity Type + DBH & M18: Decay + vegetation cover + Cavity Type + DBH &
& -40.344 & 91.313 & 3.854 & 0.018\tabularnewline
& M19: Decay + vegetation cover + Cavity Type & M19: Decay + vegetation
cover + Cavity Type & M19: Decay + vegetation cover + Cavity Type & M19:
Decay + vegetation cover + Cavity Type & & -41.503 & 91.419 & 3.961 &
0.017\tabularnewline
& M20: Decay + Cavity Type + height & M20: Decay + Cavity Type + height
& M20: Decay + Cavity Type + height & & & -41.549 & 91.511 & 4.052 &
0.017\tabularnewline
& M21: Cavity Type + opening & M21: Cavity Type + opening & & & &
-42.719 & 91.682 & 4.224 & 0.015\tabularnewline
& M22: Decay + Cavity Type + DBH + depth & M22: Decay + Cavity Type +
DBH + depth & M22: Decay + Cavity Type + DBH + depth & M22: Decay +
Cavity Type + DBH + depth & & -40.557 & 91.738 & 4.280 &
0.015\tabularnewline
& M23: Decay + Cavity Type + depth & M23: Decay + Cavity Type + depth &
M23: Decay + Cavity Type + depth & & & -41.751 & 91.914 & 4.456 &
0.014\tabularnewline
& \emph{Null Model} & \emph{Null Model} & & & & \emph{-67.350} &
\emph{136.74} & \emph{49.2824} & \emph{2.5E-12}\tabularnewline
\textbf{Golden-fronted Woodpecker (n = 55)} & \textbf{Golden-fronted
Woodpecker (n = 55)} & \textbf{Golden-fronted Woodpecker (n = 55)} &
\textbf{Golden-fronted Woodpecker (n = 55)} & & & logLik & AICc & \selectlanguage{greek}Δ\selectlanguage{english}AICc
& Weight\tabularnewline
& M1: Decay + vegetation cover & M1: Decay + vegetation cover & M1:
Decay + vegetation cover & & & -12.655 & 31.781 & 0.000 &
0.267\tabularnewline
& M2: Decay + vegetation cover + DBH & M2: Decay + vegetation cover +
DBH & M2: Decay + vegetation cover + DBH & M2: Decay + vegetation cover
+ DBH & & -12.319 & 33.439 & 1.657 & 0.117\tabularnewline
& M3: Decay + vegetation cover + opening & M3: Decay + vegetation cover
+ opening & M3: Decay + vegetation cover + opening & M3: Decay +
vegetation cover + opening & & -12.607 & 34.014 & 2.233 &
0.087\tabularnewline
& M4: Decay + vegetation cover + height & M4: Decay + vegetation cover +
height & M4: Decay + vegetation cover + height & M4: Decay + vegetation
cover + height & & -12.636 & 34.072 & 2.290 & 0.085\tabularnewline
& M5: Decay + vegetation cover + depth & M5: Decay + vegetation cover +
depth & M5: Decay + vegetation cover + depth & M5: Decay + vegetation
cover + depth & & -12.640 & 34.080 & 2.299 & 0.085\tabularnewline
& M6: Decay + vegetation cover + DBH + depth & M6: Decay + vegetation
cover + DBH + depth & M6: Decay + vegetation cover + DBH + depth & M6:
Decay + vegetation cover + DBH + depth & & -12.207 & 35.639 & 3.857 &
0.039\tabularnewline
& M7: Decay + vegetation cover + DBH + opening & M7: Decay + vegetation
cover + DBH + opening & M7: Decay + vegetation cover + DBH + opening &
M7: Decay + vegetation cover + DBH + opening & & -12.249 & 35.723 &
3.941 & 0.037\tabularnewline
& M8: Decay + vegetation cover + DBH + height & M8: Decay + vegetation
cover + DBH + height & M8: Decay + vegetation cover + DBH + height & M8:
Decay + vegetation cover + DBH + height & & -12.319 & 35.862 & 4.081 &
0.035\tabularnewline
& M9: Decay + vegetation cover + height + opening & M9: Decay +
vegetation cover + height + opening & M9: Decay + vegetation cover +
height + opening & M9: Decay + vegetation cover + height + opening & &
-12.567 & 36.358 & 4.577 & 0.027\tabularnewline
& \emph{Null Model} & \emph{Null Model} & \emph{} & \emph{} & \emph{} &
\emph{-32.227} & \emph{66.530} & \emph{34.749} &
\emph{7.6E-09}\tabularnewline
\textbf{Black-crested Titmouse (n = 39)} & \textbf{Black-crested
Titmouse (n = 39)} & \textbf{Black-crested Titmouse (n = 39)} &
\textbf{Black-crested Titmouse (n = 39)} & & & logLik & AICc & \selectlanguage{greek}Δ\selectlanguage{english}AICc &
Weight\tabularnewline
& M1: Decay + vegetation cover + Cavity Type & M1: Decay + vegetation
cover + Cavity Type & M1: Decay + vegetation cover + Cavity Type & M1:
Decay + vegetation cover + Cavity Type & & -11.672 & 32.520 & 0.000 &
0.185\tabularnewline
& M2: Decay + Cavity Type & M2: Decay + Cavity Type & & & & -13.420 &
33.526 & 1.005 & 0.112\tabularnewline
& M3: Decay + vegetation cover + Cavity Type + height & M3: Decay +
vegetation cover + Cavity Type + height & M3: Decay + vegetation cover +
Cavity Type + height & M3: Decay + vegetation cover + Cavity Type +
height & & -11.465 & 34.748 & 2.227 & 0.061\tabularnewline
& M4: Decay + vegetation cover + Cavity Type + DBH & M4: Decay +
vegetation cover + Cavity Type + DBH & M4: Decay + vegetation cover +
Cavity Type + DBH & M4: Decay + vegetation cover + Cavity Type + DBH & &
-11.498 & 34.815 & 2.295 & 0.059\tabularnewline
& M5: Decay + vegetation cover + Cavity Type + opening & M5: Decay +
vegetation cover + Cavity Type + opening & M5: Decay + vegetation cover
+ Cavity Type + opening & M5: Decay + vegetation cover + Cavity Type +
opening & & -11.573 & 34.964 & 2.443 & 0.054\tabularnewline
& M6: Decay + vegetation cover + Cavity Type + depth & M6: Decay +
vegetation cover + Cavity Type + depth & M6: Decay + vegetation cover +
Cavity Type + depth & M6: Decay + vegetation cover + Cavity Type + depth
& & -11.650 & 35.117 & 2.597 & 0.050\tabularnewline
& M7: Decay + Cavity Type + DBH & M7: Decay + Cavity Type + DBH & M7:
Decay + Cavity Type + DBH & & & -13.008 & 35.193 & 2.673 &
0.049\tabularnewline
& M8: Decay + Cavity Type + depth & M8: Decay + Cavity Type + depth &
M8: Decay + Cavity Type + depth & & & -13.381 & 35.938 & 3.418 &
0.033\tabularnewline
& M9: Decay + Cavity Type + height & M9: Decay + Cavity Type + height &
M9: Decay + Cavity Type + height & & & -13.412 & 36.001 & 3.481 &
0.032\tabularnewline
& M10: Decay + Cavity Type + opening & M10: Decay + Cavity Type +
opening & M10: Decay + Cavity Type + opening & & & -13.416 & 36.009 &
3.489 & 0.032\tabularnewline
& M11: Decay + vegetation cover & M11: Decay + vegetation cover & M11:
Decay + vegetation cover & & & -15.113 & 36.912 & 4.391 &
0.021\tabularnewline
& M12: Decay + vegetation cover + Cavity Type + DBH + height & M12:
Decay + vegetation cover + Cavity Type + DBH + height & M12: Decay +
vegetation cover + Cavity Type + DBH + height & M12: Decay + vegetation
cover + Cavity Type + DBH + height & M12: Decay + vegetation cover +
Cavity Type + DBH + height & -11.189 & 37.002 & 4.482 &
0.020\tabularnewline
& \emph{Null Model} & \emph{Null Model} & \emph{} & \emph{} & &
\emph{-26.917} & \emph{55.940} & \emph{23.422} &
\emph{1.52E-06}\tabularnewline
\bottomrule
\end{longtable}

\textbf{Supp Figs.}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image2/image2}

\end{center}
\end{figure}

\textbf{Sup Fig. 1: Visual of walking transects used to detect and
locate Golden-fronted woodpecker nests throughout the 12, 1 km plots
placed on the San Antonio Viejo Ranch, East Foundation, during spring
and summer 2019. Orange path was followed during visits 1 and 3, blue
path was followed for visits 2 and 4.}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image3/image3}

\end{center}
\end{figure}

\textbf{Supp Fig 2: Insect sampling method: A subset of 24
Golden-fronted woodpecker nests (occupied), and their corresponding
unoccupied sites (having same vegetation alliance) was chosen to conduct
insect surveys. Insects were sampled once a week from May-July with a
sweep net, samples were sorted to insect order, and dried and weighted.}

\selectlanguage{english}
\FloatBarrier
\end{document}

