Abstract
I aimed to better understand the community ecology of sympatric birdlife
in subtropical South East Queensland, Australia using patterns of
temporal species co-occurrence and principles from network theory. In
line with expectation, a hierarchical clustering analysis showed that
dates that were successive were joined by the shortest branch lengths
because of similar patterns of observed bird species. The only date
sampled in the Southern hemisphere Autumn was awarded its own branch in
the tree, indicating these observations were relatively distinct.
Estimates of total observed bird biomass were substantively higher in
the Autumn sample. Ranking each species on its average pairwise
correlation to the other 87 species in the set shows that,
unsurprisingly, raptors (such as Whistling Kites, Haliastur splenurus)
tend to be the most negatively correlated (hypergeometric enrichment
statistic P = 0.00029) indicating their presence is inhibitory to other
avian species. On the other hand, Silvereyes (Zosterops lateralis)
possess the highest number of total connections, the highest radiality
(or ‘network influence’) metric within the inferred co-occurrence
network and have the second highest average positive correlation to all
other bird species in the set (+0.32). Collectively, this means
Silvereyes can be seen as an indicators whose presence indicates an
enhanced likelihood of observing a diversity of other bird species.
Network clustering analysis detects a large module of positively
connected bird species within the overall structure (dominated by
non-threatening diminutive species as Z. lateralis, Little Friarbirds
Philomon citreogularis and Red Backed Fairy Wrens Malurus
melanocephalus), whereas all but one of the raptors sit on the
periphery. The use of the PCIT network reconstruction algorithm is
demonstrated for the first time in community ecology.