A long-term study spanning 16 years on a population of Seychelles warblers (Acrocephalus sechellensis) located on Cousin Island in the Seychelles has revealed important insights into how environmental factors, particularly rainfall, influence the durability of pair bonds in birds.
A long-term study spanning 16 years on a population of Seychelles warblers (Acrocephalus sechellensis) located on Cousin Island in the Seychelles has revealed important insights into how environmental factors, particularly rainfall, influence the durability of pair bonds in birds.
A team of international researchers, including Macquarie University’s Frigg Speelman, discovered that variations in rainfall before and during the breeding season significantly affect the chances of “divorce” among mates. This finding underscores the broader consequences of climate change on animal reproduction and conservation efforts.
In the context of species that are socially monogamous, divorce refers to the breakdown of a pair bond while both partners are still alive. This mating behavior is often linked to low reproductive success and has been observed in several bird species. Nevertheless, the connection between environmental factors, especially climate variability, and divorce is still not well understood.
Social monogamy indicates that two birds have formed a long-lasting pair bond and typically partner with each other for many years or even their entire lives. While these bonded birds usually live and rear young together, they are not necessarily sexually monogamous, which means they may mate with multiple partners over their lifetimes.
“After analyzing 16 years of data, we uncovered a complex, non-linear connection between rainfall patterns and divorce rates. Interestingly, divorce rates tend to rise during years of both low and high rainfall,” explained Speelman.
“The relationship was significantly affected by a major climatic event — the rainfall surge caused by the 1997 El Niño,” he added.
Key Findings:
- Rainfall and divorce: The research highlighted a quadratic relationship between rainfall and divorce rates, with the peak divorce rates occurring in years of either extremely low or high rainfall during the breeding season.
- The impact of the 1997 El Niño: The intense rainfall experienced in 1997 emerged as a significant anomaly in the data, showing that exceptionally high rainfall was associated with a notable rise in divorce rates. Excluding this event from the findings revealed a clearer negative correlation between rainfall and divorce.
- Reproductive success: Although rainfall was shown to affect divorce rates, the study did not find a direct correlation between reproductive success (defined as the number of offspring produced) and the likelihood of partners separating, indicating that other unidentified factors may be at play affecting the stability of partnerships.
Implications for conservation and adapting to climate change
This research, published in the Journal of Animal Ecology, contributes to the growing body of evidence illustrating how environmental factors, especially those tied to climate change, can directly shape the social behaviors and reproductive strategies of wildlife.
“As climate change continues to escalate, it is crucial to understand how changes in environmental conditions like rainfall impact the stability of socially monogamous species,” stated Speelman.
“This study not only deepens our comprehension of animal behavior in response to climate variability but also offers important insights that can enhance conservation strategies for species at risk due to climate change.”
The Seychelles warbler, which is native to the Seychelles islands, is already facing numerous conservation challenges, making the study’s findings particularly significant. The research indicates that environmental changes could further threaten this species’ reproductive success and overall population stability.
