A 16-year study on a closed population of Seychelles warblers (Acrocephalus sechellensis) on Cousin Island, Seychelles, has uncovered significant findings about how environmental factors – specifically rainfall – affect the stability of pair bonds in birds.
Macquarie University’s Frigg Speelman was part of an international team of researchers that found fluctuations in rainfall prior to and during the breeding season significantly influence the likelihood of "divorce" between mates, highlighting the broader implications of climate change for animal reproduction and conservation.
Divorce, in the context of socially monogamous species, refers to the termination of a pair bond while both individuals are still alive. This mating strategy is often associated with poor reproductive success and has been observed in various bird species. However, the relationship between environmental factors, particularly climate fluctuations, and divorce is poorly understood.
Social monogamy implies that two birds have formed a pair bond and associate with the same partner, usually over many years and even a lifetime. Although pair-bonded birds usually live and raise young together, they are not necessarily sexually monogamous, where they mate with only one partner for life.“We analysed 16 years of data and found a complex, non-linear relationship between rainfall patterns and divorce rates, with divorce being more likely during years of both low and high rainfall,” says Speelman.“This relationship was notably influenced by an extreme climatic event – the 1997 El Niño-induced rainfall spike.”
Key findings:
Rainfall and divorce: The study identified a quadratic relationship between rainfall and divorce rates, with the highest rates of divorce occurring in years with either extremely low or high rainfall during the breeding season.