Consequences of a changing environment on the breeding phenology and reproductive success components in a long‐distance migratory bird

Abstract

Migratory birds have a narrow time window to breed, especially in the Arctic, where early nesting typically yields the highest reproductive success. We assessed temporal changes (1991–2015) in reproductive success components in relation to timing of breeding in greater snow geese (Chen caerulescens atlantica). This species breeds in the Canadian Arctic, a region that has experienced a strong warming trend. We tested the effect of laying or hatching date, year and their interaction on six reproductive components: Total clutch laid, nesting success, egg survival, hatching success, prefledging, and postfledging survival. Over 25 years, mean laying date changed little, even though it advanced 1.8 days in early breeders and was delayed 3 days in late breeders. Likewise, the number of eggs in nests initiated early in the season decreased by 0.6 egg, whereas in late nests it increased by 0.3 egg. Success of nests initiated early and late in the season was lower than nests initiated near the population mean, and consistently increased over time. The proportion of eggs surviving to partial predation and postfledging survival decreased with laying date but the pattern did not change over time. In contrast, prefledging survival was not affected by laying date initially but declined in nests initiated late in the season toward the end of the study. Overall, nests initiated close to the population mean showed little temporal change for most components of reproductive success and seem to be less affected by environmental change than nests initiated early and late in the season.

Temporal changes in reproductive success and optimal breeding decisions in a long-distance migratory bird

“…The general pattern of seasonal variation in reproductive success of greater snow geese was maintained over a 25-year period, with the highest success achieved for birds laying before the population median. The maximum reproductive success increased over time and the date at which it was achieved advanced by at least 2 days although the median egg-laying date did not change in the population 25 . Consequently, the seasonal decline in reproductive success became steeper over time.…”

“…Reproductive success of birds laying at the population median or after changed little in contrast to those laying earlier. This is somewhat surprising considering that prefledging survival of late-hatched goslings tended to decrease over time 25 , possibly because the mismatch between hatching date and the peak in plant nutritive quality increased 21,24 . Recent evidence shows that black brant goslings (Branta bernicla nigricans) can respond to decreasing food availability with behavioural adjustments 33 (reduced resting periods and increased search time for food), which could partly buffer the negative effects of trophic mismatch.…”

“…However, laying too early also entails a cost, as reproductive success of the earliest breeders was low. The poor success of the earliest nests is driven mostly by the nesting success component 25 . These nests suffer higher predation by arctic foxes ( Vulpes lagopus ), the main cause of failure 26 , than nests initiated near the population mean.…”

“…Prior research documented strong seasonal effects on several components of reproductive success in greater snow geese, from egg-laying until young reach 1 year of age 12 . Despite a pronounced warming trend on their breeding ground on Bylot Island (Canada), there was little change in laying date over the past 3 decades, thereby increasing the potential for a trophic mismatch 22 , 25 . We previously showed that seasonal patterns of reproductive success components followed different and sometimes opposite trends over 25 years in this population 25 .…”

“…Despite a pronounced warming trend on their breeding ground on Bylot Island (Canada), there was little change in laying date over the past 3 decades, thereby increasing the potential for a trophic mismatch 22 , 25 . We previously showed that seasonal patterns of reproductive success components followed different and sometimes opposite trends over 25 years in this population 25 . Clutch size decreased with laying date but this effect weakened over time.…”