Ecology: Songbirds reduce reproduction during drought

Tropical songbirds in Venezuela and Malaysia reduced reproduction during drought, with greater reductions in species with higher average long-term survival, according to a paper published in Nature Climate Change. These findings suggest that species with longer lifespans may be able to mitigate the impacts of stressful climate events by reducing reproduction in those years.

Climate variability, including drought frequency and intensity, is projected to increase with future warming. Reproduction rates are typically lower for species with longer lifespans, which means that they are less able to recover from mortality during climate events. However, there is a trade-off between survival and reproduction, and reducing reproduction in years with harsh events may be a way to increase adult survival.

Thomas Martin and James Mouton investigated whether tropical songbirds from the New and Old World with different life histories (long-lived versus short-lived species) avoid mortality by reducing reproduction. They conducted field demographic studies of 38 different species — including the grey-breasted wood wren and white-crowned forktail — in Venezuela and Malaysia over multiple years, including one drought year for each field site. The authors also modelled future population dynamics under three different climate change scenarios.

They found that reproduction was reduced during drought by an average of 36% in the 20 Malaysian species and 52% in the 18 Venezuelan species. For most long-lived species that reduced reproduction, survival increased relative to years without droughts, whereas survival rates decreased for species that did not reduce reproduction, or did not substantially reduce reproduction, as well as for those heavily reliant on wet habitats. The negative effects of drought on modelled population growth were lower for longer-lived rather than shorter-lived species under climate change. This indicates that longer-lived species may be able to adjust reproduction to survive environmental variability under climate change.

Writing in a related News & Views article, Gonçalo Ferraz notes that this work informs conservation management by identifying species’ vulnerability, but writes that “it does not change the central importance of habitat availability for species survival.”

doi: 10.1038/s41558-020-0864-3

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