Use of a novel nest substrate in a Neotropical migratory bird, the veery (Catharus fuscescens)
In 2011, an early, record-breaking snowstorm in the Hudson Valley (NY) downed thousands of oak (Quercus spp.) limbs at our study site. These fallen oak limbs (FOL) retained brown leaves through the following two summers, providing a novel nesting substrate, averaging 40.7 FOL/ha (range 3-126). Such a widespread event had not occurred in the system for at least the prior 13 years, providing an opportunity to test hypotheses regarding behavioral responses to this novel nest substrate. Female Veery appear more cryptic when sitting in FOL, and we hypothesized that they select FOL to increase nest survival, particularly when they perceive predation risk to be high. We predicted that nest survival would be higher in FOL than other common substrates, which are primarily green-leaved shrubs. From May-July 2012 and 2013, we monitored Veery nests every 3 days. We used Program MARK to model nest survival as a function of nest substrate.
Of nest attempts in 2012 and 2013, 54% and 29% (respectively) were in FOL, compared to <2% of nests from 1998-2011. Barberry (Berberis thunbergii), typically the most common substrate, held 24% of nests annually from 1998-2013. We analyzed 126 nests (n2012 = 67 and n2013 = 59) using Program MARK. Daily nest survival (DNS) was similar for FOL and barberry, but higher than for all other substrates in both years, with nests in 2013 having overall higher survival. DNS2012 for FOL = 0.965 (SE = 0.007, 95% CI = 0.948-0.977) and DNS2012 for barberry = 0.963 (SE = 0.009, 95% CI = 0.939-0.978). DNS2013 for FOL = 0.970 (SE = 0.008, 95% CI = 0.950-0.982) and DNS2013 for barberry = 0.968 (SE = 0.009, 95% CI = 0.947-0.981). For all other substrates combined, DNS2012 = 0.951 (SE = 0.012, 95% CI = 0.923-0.970) and DNS2013 = 0.958 (SE = 0.008, 95% CI = 0.938-0.972). We conclude that the dramatic switch to FOL did not reduce Veery nest survival, as compared to barberry, and both were better than other substrates. This suggests this species may be behaviorally flexible in regards to nest substrate selection. Behaviorally flexible species might better adapt to rapidly changing environments, including those stemming from anthropogenic habitat modification.