Climate change and the risks associated with delayed breeding in a tropical wild bird population

Abstract

There is growing evidence of changes in the timing of important ecological events, such as flowering in plants and reproduction in animals, in response to climate change, with implications for population decline and biodiversity loss. Recent work has shown that the timing of breeding in wild birds is changing in response to climate change partly because individuals are remarkably flexible in their timing of breeding. Despite this work, our understanding of these processes in wild populations remains very limited and biased towards species from temperate regions. Here, we report the response to changing climate in a tropical wild bird population using a long-term dataset on a formerly critically endangered island endemic, the Mauritius kestrel. We show that the frequency of spring rainfall affects the timing of breeding, with birds breeding later in wetter springs. Delays in breeding have consequences in terms of reduced reproductive success as birds get exposed to risks associated with adverse climatic conditions later on in the breeding season, which reduce nesting success. These results, combined with the fact that frequency of spring rainfall has increased by about 60 per cent in our study area since 1962, imply that climate change is exposing birds to the stochastic risks of late reproduction by causing them to start breeding relatively late in the season.

Phenological Changes in the Southern Hemisphere

“…These characteristics potentially make island species more vulnerable to rapid climate shifts (e.g. the Mauritius Kestrel Falco punctatus [81]). However, some highly migratory bird species, such as the South Polar Skua Catharacta maccormicki show a wide variation in their migration behaviours, even within a single breeding population, indicating the potential for buffering in some species [82].…”

Opposing selection and environmental variation modify optimal timing of breeding

“…(i) Timing of first breeding by multibrooded parrotlet females influences the number of nesting attempts and offspring that they produce in a year, whereas most temperate birds nest one time and raise a single brood annually (30). (ii) Longer tropical breeding seasons may alter the relationships between adult and juvenile survival, food availability, and breeding date (22,31). (iii) Nonbreeding males and females are common in parrotlets (and other tropical species), causing strong competition for nest sites and infanticide (12,31,32).…”

“…The environmental condition most commonly examined in studies of timing of breeding is temperature, because it influences food availability in northern temperate regions, where climate warming has resulted in shifts in the timing of breeding in some species (13-16, 19, 20). In tropical regions, however, food availability is more strongly affected by rainfall than temperature fluctuations, which has been shown in parrotlets; therefore, rainfall may influence selection on timing of breeding in tropical species (21)(22)(23). Rainfall is also expected to respond to climate change and may have a greater effect on tropical species than climate warming (21,22,24).…”

“…In tropical regions, however, food availability is more strongly affected by rainfall than temperature fluctuations, which has been shown in parrotlets; therefore, rainfall may influence selection on timing of breeding in tropical species (21)(22)(23). Rainfall is also expected to respond to climate change and may have a greater effect on tropical species than climate warming (21,22,24). If rainfall before breeding is positively related to food availability (21), then fecundity selection for breeding earlier in the year should occur.…”

Assessing population viability while accounting for demographic and environmental uncertainty

“…This task is becoming increasingly urgent, as global climate change leads to changes in temperature and rainfall patterns around the world, which may affect many populations (Both et al 2009, van de Pol et al 2010, Senapathi et al 2011. Environmental perturbations or long-term climatic changes can affect several demographic parameters, and integrating these complex interactions to assess the viability of a population can be challenging (Katzner et al 2006, Nadeem andLele 2012).…”