Rainfall is associated with divorce in the socially monogamous Seychelles warbler

1. Divorce – the termination of a pair bond while both members are alive – is a mating strategy observed in many socially monogamous species, often linked to poor reproductive success. As environmental factors directly affect individual condition and reproductive performance, they can indirectly influence divorce. Given current climate change, understanding how partnership stability is affected by environmental fluctuations has important implications, including for conservation. Yet, the relationship between the ecological environment and divorce remains largely unstudied.2. We examined the influence of temporal environmental variability on the prevalence of divorce and the possible underlying mechanisms in a socially monogamous passerine.3. Using a 16–year longitudinal dataset, we investigated the relationship between rainfall and divorce in the Seychelles warbler (Acrocephalus sechellensis). First, we performed climate window analyses to test if specific temporal windows of rainfall predicted reproductive success and divorce. Then, we analyzed the effects of those temporal windows of rainfall on reproductive success and divorce and the influence of reproductive success on divorce. 4. Annual divorce rates varied from 1–16%. The probability of divorce showed a significant quadratic relationship with rainfall, increasing in years with low and high rainfall. Although the same temporal window of rainfall predicting divorce also significantly influenced reproductive success, we found no significant correlation between reproductive success and divorce.5. Our findings suggest that rainfall impacts divorce. Given that this effect is likely not directly mediated by reproductive success, we discuss the possible role of physiological stress. By adding to the growing body of literature showing that environmental conditions influence the stability of socially monogamous partnerships, we provide novel insights that may also be important for conservation efforts in times of climate change.