Abstract
Global climate change has advanced the breeding phenology of many avian species. However, raptors’ breeding phenologies may not respond in the same way to the factors that influence passerine breeding dates. We studied reproduction of suburban and rural Red-shouldered Hawks (Buteo lineatus) in southern Ohio, United States, from 1997 to 2020. Mean hatching dates for 786 broods were 24 April [Julian day: 114.1 ± 0.3 d (SE)] for suburban birds and 25 April (Julian day: 114.5 ± 0.4) for rural birds. Egg-laying date averages approximately 33 days before hatching date, or about the third week of March. We used mixed models to test which factors influenced nestling hatching dates from 1997 to 2020. The best model included year, days of snow cover during the pre-laying period (February–March), and mean March temperature, with days of snow cover having the largest effect. Hatching date (in Julian days) was positively related to snow cover and negatively related to air temperature, i.e., young hatched earlier in years with fewer days of snow cover and in warmer years). Young also hatched slightly later as the study progressed. Overall, neither mean hatching date nor any of the weather variables showed a significant trend over the course of the study. Previously published reports indicate that many raptor species do not exhibit advancing hatching dates, and breeding phenologies often reflect local weather conditions. The complexity and diversity of raptor responses to climate change underscore the importance of long-term studies of raptors at multiple locations.
Highlights
Global climate change has advanced the breeding phenology of many avian species (Root et al, 2003; Thackeray et al, 2010), with subsequent effects on productivity, breeding success, and survival (Dunn and Møller, 2019)
Mean Red-shouldered Hawk hatching dates in southern Ohio did not advance over the 24 years from 1997 through 2020; our consistent methodology, large sample size, and length of Estimate St
Hatching dates were most influenced by the number of days with snow cover and the air temperature during the pre-laying period, with earlier hatching in years with less snow cover and warmer years
Summary
Global climate change has advanced the breeding phenology of many avian species (Root et al, 2003; Thackeray et al, 2010), with subsequent effects on productivity, breeding success, and survival (Dunn and Møller, 2019). Raptors’ breeding phenologies may not respond in the same way to the factors that influence passerine breeding dates (Bretagnolle and Terraube, 2019). Smaller birds such as passerines (and smaller raptors) may be more sensitive to temperature, more able to adjust their physiology, and more likely to exhibit advanced laying dates (Stevenson and Bryant, 2000; Lehikoinen et al, 2011; Bretagnolle and Terraube, 2019). In comparison to passerine studies, analyses of raptor breeding phenologies are relatively uncommon; yet shifts in raptor phenologies could have important impacts for the conservation of the individual species and trophic webs (Both et al, 2009; Lehikoinen et al, 2009; Heath et al, 2012)
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