Relative importance off environmental variables in determining the growth off nestling Tree Swallows Tachycineta bicolor

Abstract

Unpredictable, short‐term changes in environmental conditions associated with weather patterns have severe impacts on the reproductive success of Tree Swallows Tachycineta bicolor, as well as other aerial insectivores. We examined the effects of day‐to‐day environmental variation on the growth of nestling Tree Swallows. Using path analysis, we compared the relative importance of changes in food availability, ambient temperature and wind speed on changes in mass and feather length over four years at our study site near Ithaca, New York. Changes in environmental conditions explained a significant amount of the variation in nestling growth, with daily high temperature having the greatest influence for nestlings younger than five days. Both food supply and temperature had significant direct effects on growth of nestlings older than nine days, with temperature also having a significant indirect effect through its influence on food availability. For both young and old chicks, mass gains were smaller for chicks hatched later in the season. Environmental conditions also explained a significant amount of the linear growth of the ninth primary feather in one of two years, with food supply showing the most consistent positive effect. Environmental conditions several days prior to the measurements significantly influenced feather growth, indicating that the effects of adverse conditions are spread out over several days of feather growth, but this effect was not seen for change in mass.

Effects of breeding date and weather on nestling development in White StorksCiconia ciconia

“…Indeed, McCarty & Winkler (1999) and Bradbury et al . (2003) showed that weather could affect Sky Lark and Yellowhammer nestling development in at least four ways.…”

Environmental variation at the onset of independent foraging affects full-grown body mass in the red fox

“…Environmental variation has also been shown to have a significant impact on growth and body size in a range of taxa, mediated by variation in food abundance and availability (bats: Tuttle 1976, Hoying & Kunz 1998carnivores: Russell et al 2002;insectivorous birds: Emlen et al 1991, McCarty & Winkler 1999ungulates: Post et al 1999, Knott et al 2005. In our study, the full-grown mass of foxes was dependent on pre-nutritional independence cub mass and sex, but appeared to be affected to a greater degree by environmentally induced variation in the abundance of an important food resource, earthworms, during the transition to independent foraging.…”

No effect of insect abundance on nestling survival or mass for three aerial insectivores

“…Relationships between insect abundance and swallow breeding success, especially nestling and postfledgling survival, have been investigated for Tree Swallows (e.g., Quinney et al 1986, McCarty and Winkler 1999a, Nooker et al 2005 and to a lesser extent for other species (e.g., Grüebler and Naef-Daenzer 2008). However, research examining these relationships with multiple species simultaneously has not been conducted.…”