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Variation in incubation length and hatching asynchrony in Eastern Kingbirds: weather eclipses female effects


Murphy, Michael (2022), Variation in incubation length and hatching asynchrony in Eastern Kingbirds: weather eclipses female effects, Dryad, Dataset,


Incubation length and hatching asynchrony are integral elements of the evolved reproductive strategies of birds and here we here quantify intra- and interpopulation variation in both traits for Eastern Kingbird (Tyrannus tyrannus) populations from New York (NY), Kansas (KS), and Oregon (OR). Multiple samples from a subset of females demonstrated that neither incubation length nor hatching asynchrony was repeatable, that both traits varied with a female trait (clutch size), but that variation in both incubation length and hatching asynchrony was to a substantial degree linked to weather, namely ambient temperature and precipitation. Incubation length exhibited the same median (15 days) and range (13 to 17 days) at all sites, and model selection results indicated that incubation periods were longer in NY than KS, among the smallest and largest clutches, when rain was frequent throughout the period when eggs were in the nest, in replacement nests, and likely when ambient temperatures were low during egg-laying. Full hatching usually required 2 days (but up to 3), and more synchronous hatching was associated with small clutch size, short incubation periods, frequent rain during the egg-laying period, and low ambient temperatures during the first half of incubation. Only 5% to 9% of nestlings starved and starvation was not associated with greater hatching asynchrony, indicating the nestling starvation was likely not a cost of hatching asynchrony. Thus, although clutch size, a female trait, contributed to variation in incubation length and hatching asynchrony, weather was a greater source of variation, especially for incubation length. Weather thus influences length of exposure of eggs to destructive forces (predators and severe weather), and as a consequence, climate change has the potential to influence reproductive success.


National Science Foundation

American Museum of Natural History