Multiple intrinsic markers identify carry-over effects from wintering to breeding sites for three Nearctic–Neotropical migrant swallows

Abstract

Carry-over effects from one stage of the annual cycle to subsequent stages can have profound effects on individual fitness. In migratory birds, much research has been devoted to examining such effects from the nonbreeding to the breeding period. We investigated potential carry-over effects influencing spring body condition, breeding phenology, and performance for 3 species of sympatric, declining Nearctic–Neotropical migratory swallows: Bank Swallow (Riparia riparia), Barn Swallow (Hirundo rustica), and Cliff Swallow (Petrochelidon pyrrhonota). To examine carry-over effects, we used structural equation modeling and several intrinsic markers, including stable isotope (δ 2H, δ 13C, and δ 15N) and corticosterone (CORTf) values from winter molted-feathers, and changes in telomere length between breeding seasons. We found support for carry-over effects for all 3 species, however, the specific relationships varied between species and sexes. Effects leading to lower breeding performance were only observed in male Bank, female Barn, and female and male Cliff Swallows. In most cases, carry-over effects were attributed to differences in stable isotope values (most commonly with δ 2H) presumably related to differences in winter habitat use, but, for Cliff Swallows, negative carry-over effects were also linked to higher CORTf values and greater rates of telomere shortening. This work provides further support for the potential role of nonbreeding conditions on population declines, and indicates how multiple intrinsic markers can be used to provide information on ecological conditions throughout the annual cycle.

Regional variability in trajectories of Barn Swallow populations across Canada are not predicted by breeding performance

“…In particular, the Barn Swallows in New Brunswick may benefit from living in colonies, as we found a positive relationship between colony size and nest success at the study sites in that region. We suggest that timing of reproduction is likely affected by carryover effects from the wintering grounds or migration routes (Rioux Paquette et al 2014, Imlay et al 2019 and by weather conditions experienced on the breeding grounds (Saino et al 2004).…”

Assessing pesticides exposure effects on the reproductive performance of a declining aerial insectivore

“…Assessing the role of pesticides in population declines not only implies to better estimate the levels of exposure to pesticides, but also to document when and where they occur as well as how their effects may carry over life stages (Imlay et al. 2019). Coupling spatially explicit, longitudinal data on pesticide use (e.g., Pesticide National Synthesis Project of the USGS), population trends and year‐round tracking data of individuals (Knight et al.…”

“…Similar to aerial insectivores, farmland birds show considerable population declines and it is imperative to better assess the role that pesticides may play in those trends, be it trophic, toxicologic or both (Stanton et al 2018). Assessing the role of pesticides in population declines not only implies to better estimate the levels of exposure to pesticides, but also to document when and where they occur as well as how their effects may carry over life stages (Imlay et al 2019). Coupling spatially explicit, longitudinal data on pesticide use (e.g., Pesticide National Synthesis Project of the USGS), population trends and year-round tracking data of individuals (Knight et al 2018, Gow et al 2019) may prove instrumental in pursuing such a quest.…”

Favorable spring conditions can buffer the impact of winter carryover effects on a key breeding decision in an Arctic‐breeding seabird

“…Variation in habitat quality on the wintering grounds may carry over to impact subsequent reproduction (Imlay et al, 2019; Norris, 2005; Rockwell et al, 2012; Szostek & Becker, 2015). An important mechanism linking wintering habitat quality to reproduction is food availability (Ballesteros et al, 2013; Brown & Sherry, 2006; Shertzer & Ellner, 2002).…”