The intra-specific variation in life-history traits represents functional attributes (e.g., resource use and allocation, reproductive investment, modes of chick growth) that reflect selective forces acting under a rapidly changing climate (Berteaux et al., 2004; Gienapp et al., 2008). To this end, we monitored the annual arrival, pre-lay duration, nest initiation, clutch size, and nesting effort of brant, snow geese, semipalmated sandpipers, and longspurs, and measured relevant environmental variables across the breeding season. We predicted that geese would exhibit more flexibility to interannual variability in spring temperature and snowmelt compared to semipalmated sandpipers and longspurs by adjusting the timing of breeding and reproductive investment due to their comparatively greater endogenous reserves and relative flexibility along the capital-income spectrum.
Because species possess traits that may promote resilience during one phase of the reproductive cycle but other traits which may be detrimental at other phases, assessing the response of species to shared environmental conditions across different phases of the reproductive cycle (e.g., Nolet et al., 2020) provides more meaningful insights into reproductive outcomes than assessments focused on just one phase. As such, in addition to monitoring responses during the pre-breeding and nesting periods, we also monitored the growth of chicks of these four species in conjunction with climatic variables and measures of the seasonal availability of herbivorous and insectivorous food resources. Because numerous studies have demonstrated that rapid growth of avian young yields larger chicks (Larsson & Forslund, 1991; Ruthrauff & McCaffery, 2005) that survive at higher rates (Lindholm et al., 1994; Naef-Daenzer et al., 2001) and have a higher probability of recruitment (Cooch et al., 1993; Magrath, 1991; Sedinger et al., 1995) than smaller same-age chicks, variation in chick growth reflects a meaningful demographic response to environmental variability. We predicted that the young of brant, snow geese, and semipalmated sandpipers would be more sensitive to variation in food abundance due to their precocial nature. We predicted that this would be reflected by relatively strong variation in body mass as a function of food abundance compared to chicks of longspurs, which are provisioned entirely by adults. Taken together, assessments of climatological (temperature, wind, and snow cover) and environmental (seasonal availability and absolute abundance of food resources) factors in relation to life-history traits across multiple phases of the reproductive cycle elucidate characteristics of Arctic-breeding birds that may mitigate negative effects of future climate change.