The role of tropical rainfall in driving range dynamics for a long-distance migratory bird

Abstract

Predicting how the range dynamics of migratory species will respond to climate change requires a mechanistic understanding of the factors that operate across the annual cycle to control the distribution and abundance of a species. Here, we use multiple lines of evidence to reveal that environmental conditions during the nonbreeding season influence range dynamics across the life cycle of a migratory songbird, the American redstart ( Setophaga ruticilla ). Using long-term data from the nonbreeding grounds and breeding origins estimated from stable hydrogen isotopes in tail feathers, we found that the relationship between annual survival and migration distance is mediated by precipitation, but only during dry years. A long-term drying trend throughout the Caribbean is associated with higher mortality for individuals from the northern portion of the species’ breeding range, resulting in an approximate 500 km southward shift in breeding origins of this Jamaican population over the past 30 y. This shift in connectivity is mirrored by changes in the redstart’s breeding distribution and abundance. These results demonstrate that the climatic effects on demographic processes originating during the tropical nonbreeding season are actively shaping range dynamics in a migratory bird.

Flexibility in the face of climate change? A rapid and dramatic shift toward later spring migration in Hudsonian Godwits (Limosa haemastica)

“…Most studies have concluded that shifts in migratory timing occur in response to changes in climate 3 . This largely precludes the possibility that shifts can be nonadaptive in nature or in response to other environmental conditions 41 . Previously, godwits were advancing their breeding ground arrival timing and appeared to be shifting in relative synchrony with the climate 11,21 .…”