Figure 4. Diel activity patterns of tree voles and nest
predators. Density plots (a) showing the hours in which six species or
groups were detected (using hour as the bin-width such that only one
detection per hour is included) at nest platforms in young trees,
central Coast Range, Oregon, USA. Shading indicates average nocturnal
period in the study area. Panel b shows weasel density plot split into
weasel detections whereby we assigned a high and low likelihood of a
tree vole mortality after a weasel was detected.
We observed a relatively strong pattern of birds digging late in wet
seasons (February – April) of 2016 and 2017, but weaker trends for
other species or groups (Fig. 5). Tree voles were detected on most nest
platforms with some reduction in use during the dry season, but presence
of juveniles was also highest during this season in 2016 and 2017 (Fig.
5). During most months flying squirrels were detected on most platforms
with lower number of platforms with a detection during February of 2016
and 2018 (Fig. 5). Weasels were not detected at nest platforms until
summer of 2016 and proportion of platforms with detections remained low
until the wet season in late 2017 to early 2018, which was also a peak
of birds digging detections (Fig. 5).