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April 13, 2012

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In bird “divorce,” females seen having the advantage

April 14, 2012
Courtesy of the University of Gothenburg
and World Science staff

Di­vorce might not be healthy—but at least it may be nat­u­ral, if find­ings from a new study are to be be­lieved.

The re­search ex­am­ined what sci­en­tists call “di­vorce” among shore­birds of a spe­cies known as Ca­li­dris al­pi­na, and found that fe­males tend to fare bet­ter in the af­ter­math of the split­ups.

Also called dunlins, these long-lived birds of­ten mate with the same part­ner over sev­er­al sea­sons, then go their se­par­ate ways, ac­cord­ing to bi­ol­o­gists Lars-Åke Flo­din and Don­ald Blom­qvist of the Uni­vers­ity of Goth­en­burg, Swe­den.

The sci­en­tists recorded 126 breed­ing at­tempts and found that 23 per­cent of the pairs di­vorced. They then com­pared the breed­ing suc­cess of males and fe­males be­fore and af­ter “di­vorce” to ex­plore some causes and con­se­quenc­es of the change. Fe­male di­vorcees that found new part­ners dou­bled their nest suc­cess, the re­search­ers found.

The im­prove­ment “ap­peared in­de­pend­ent of breed­ing ex­pe­ri­ence,” Flo­din and Blom­qvist wrote, re­port­ing their find­ings in the re­search jour­nal Be­hav­iour. “We were un­able to de­tect any ef­fect of di­vorce on male re­pro­duc­tive suc­cess.”

The researchers con­clud­ed that fe­male dun­lins di­vorce to up­grade to a bet­ter mate or ter­ri­to­ry.

Di­vorc­ing cou­ples weren’t found to dif­fer from non-divorcing cou­ples in nest suc­cess in the sea­son pre­ced­ing di­vorce, both in terms of to­tal nest fail­ure or the num­ber of eggs in the nest. Non-divorcing pairs and male di­vorcees that paired with new part­ners had si­m­i­lar nest suc­cess in con­sec­u­tive years.

“So­cial mo­nog­a­my is a rare mat­ing sys­tem among an­i­mals, oc­cur­ring com­monly only in birds,” the re­search­ers not­ed. “In long-lived birds, pair bonds may per­sist for sev­er­al sea­sons in some spe­cies, while in oth­ers mate change oc­curs even when both part­ners are still alive.”

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Divorce might not be healthy—but at least it may be natural, if findings from a new study are to be believed. The research examined what scientists call “divorce” among shorebirds of a species known as Calidris alpina, and found that females often fare better in the aftermath. These long-lived birds often mate with the same partner over several seasons, but then split up, according to biologists Lars-Åke Flodin and Donald Blomqvist of the University of Gothenburg, Sweden. The scientists recorded 126 breeding attempts and found that 23% of the pairs divorced. They then compared the breeding success of males and females before and after divorce to explore some causes and consequences of divorce. Female divorcees that found new partners doubled their nest success, the researchers found, concluding that female dunlins divorce to upgrade to a better mate or territory. The improvement “appeared independent of breeding experience,” Flodin and Blomqvist wrote, reporting their findings in the research journal Behaviour. “We were unable to detect any effect of divorce on male reproductive success.” Divorcing couples weren’t found to differ from non-divorcing couples in nest success in the season preceding divorce, both in terms of total nest failure or the number of eggs in the nest. Non-divorcing pairs and male divorcees that paired with new partners had similar nest success in consecutive years. “Social monogamy is a rare mating system among animals, occurring commonly only in birds,” the researchers noted. “In long-lived birds, pair bonds may persist for several seasons in some species, while in others mate change occurs even when both partners are still alive.”