Shorebirds more likely to divorce after successful breeding

The researchers studied the mating behaviour of eight different species of Charadrius plovers, covering 14 populations in different locations across the world.

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

Plover chicks mature quickly and fly the nest around a month after hatching; in most plover species both parents care for the hatchlings, but in some species either parent can desert the nest to breed again with a new mate.

Surprisingly, the researchers found that pairs that successfully raised chicks were more likely to divorce, whereas unsuccessful pairs tended to stick together and try breeding again.

Females were more likely to desert the nest than males, and those that did often produced more offspring within a season than parents that retained their mate.

Plovers that divorced also dispersed across greater distances between breeding attempts to look for new mates.

The findings, published in the journal Scientific Reports, suggest that a range of factors including the adult sex ratio, the length of breeding season and adult lifespan affect the fidelity and parenting behaviour of these birds, rather than simply being due to the species.

Naerhulan Halimubieke, PhD student at the Milner Centre for Evolution at the University of Bath and first author of the paper, said: "Our findings go against what you'd intuitively expect to happen -- that divorce would be triggered by low reproductive success.

"Interestingly, we found that mate fidelity varied amongst different populations of the same species -- for example, Kentish plovers in Europe and China are serial polygamists and are migratory, whereas those found on Cape Verde are exclusively monogamous.

"This shows that mating behaviour is not simply down to which species they belong, but that other factors affecting the population are also important, such as ratio of males to females and temperature variation of the habitat."

Tamás Székely, Professor of Biodiversity at the Milner Centre for Evolution, said: "Our previous work has shown that in populations where there are more females than males, the female tends to leave the nest after breeding to make another nest with a new mate.

"Since plover chicks don't need much work in bringing them up, one of the parents can free themselves from the nest early and go on to breed elsewhere.

"Females are more likely to leave their partners if the population is skewed towards males, because they have a greater choice of potential partners and so are more likely to increase their reproductive success by breeding with another mate.

"More research is needed to fully understand how factors such as the adult sex ratio and the climate of the populations affects the breeding behaviour of these birds."