Breeding Phenology of Red-Shouldered Hawks (Buteo lineatus) Is Related to Snow Cover and Air Temperature During the Pre-Laying Period

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.

Breeding Phenology and Nestling Morphology of Bald Eagles in the Upper Midwestern United States1

“…For example, size and growth of different morphological traits have been used to investigate adaptive modifications that may differ slightly by region (e.g., Ricklefs 1968, O'Connor 1977. Determining a reasonably precise age of nestlings is necessary for calculating breeding phenology and for assessing the effects of weather and climate, which can influence the timing and DECEMBER 2022 399 BALD EAGLE NESTLING MORPHOLOGY success of some breeding raptors (Dykstra et al 2021). For Bald Eagles in northern areas, the timing of ice-breakup on area rivers and lakes each spring can be particularly important for adults that often depend on aquatic prey to feed nestlings (Grim and Kallemeyn 1995).…”

Sibling Aggression, Feeding Rates, and Hatch Rank of Nestling Red-Shouldered Hawks (Buteo lineatus)

“…In southwestern Ohio, we and others studied a suburban population of Red-shouldered Hawks from 1997 to 2019 (Dykstra et al 2000(Dykstra et al , 2019(Dykstra et al , 2021a. Generally, Red-shouldered Hawks in this population engage in courtship behaviors and construct or refurbish nests from mid-February to mid-March, with egg laying beginning in mid-to late March (Dykstra et al 2020(Dykstra et al , 2021b. Clutch size typically ranges from two to four eggs (Portnoy andDodge 1979, Miller et al 2020) and incubation lasts about 33 d per egg (Miller et al 2020).…”