Birds

Waders are more likely to be divorced after successful breeding

An international team of scientists studying waders, led by the University of Bath, has found that successful plover parents are more likely to divorce after nesting than those who do not breed, unlike most other bird species that do splitting nesting bugs.

The researchers studied the mating behavior of eight different Charadrius plovers, covering 14 populations in different locations around the world.

These waders tend to lay 2-4 eggs per nest and can have up to four breeding attempts per season.

Plover chicks mature quickly and fly out of the nest about a month after hatching. Most plover species have both parents looking after the young, but in some species either parent can leave the nest to reproduce with a new partner.

Surprisingly, the researchers found that couples who successfully raised chicks were more likely to divorce, while unsuccessful couples tended to stick together and breed again.

Females were more likely than males to leave the nest, and those who often had more offspring in one season than parents who kept their partner.

Kentish Plover, copyright Glyn Sellors, from the Surfbirds Galleries

Divorced plover also spread over greater distances between breeding attempts to look for new mates.

The results, published in the journal Scientific Reports, suggest that a number of factors, including adult sex ratio, length of breeding season and adult lifespan, affect the fidelity and parental behavior of these birds, and not just species.

Naerhulan Halimubieke, PhD student at the Milner Center for Evolution at the University of Bath and first author of the paper, said, “Our results contradict what you would intuitively expect – this divorce would be triggered by low reproductive success.

“Interestingly, we found that partner fidelity varied between different populations of the same species. For example, Kentish plovers in Europe and China are serial polygamists and migrate, while those found on Cape Verde are exclusively monogamous.

“This shows that mating behavior depends not only on the species they belong to, but that other factors influencing the population are also important, such as the ratio of males to females and the temperature fluctuations of the habitat.”

Tamás Székely, Professor of Biodiversity at the Milner Center for Evolution, said: “Our previous work has shown that in populations where there are more women than men, women leave the nest after breeding to find a new nest with a new partner to build.

“Since plover chicks don’t need a lot of work to raise them, one of the parents can break out of the nest early and breed elsewhere.

“Women are more likely to leave their partners when the population is male-centered because they have more choice of potential partners and are therefore more likely to increase their reproductive success by breeding with another partner.

“More research is needed to fully understand how factors such as adult sex ratios and the climate of the populations influence the breeding behavior of these birds.”

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