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Unrelated offspring care could be birds’ investment strategy

Seychelles-warbler-3-credit-Sjouke-Anne-KingmaBIRDS WILL CARE for unrelated birds’ offspring and postpone their own chance of reproduction to improve their future prospects, a new study suggests.

Evolutionary biologist Sjouke Kingma’s study, published last month in the journal Nature Communications, opposes the widely accepted idea that birds only help family members in order to pass on their genes, without having to reproduce themselves.

But Mr Kingma claims that individuals not only help family members; many are more eager to help non-family members if they stand to inherit their territory in the future.

Over several decades, Mr Kingma, from the University of Groningen in the Netherlands, studied published papers on 44 cooperative breeding species and analysed brooding and parenting help. He found that being tolerated in a non-family members’ territory and the chance to inherit that territory are considered rewards, for which some birds are willing to postpone their own chances of reproduction.

Mr Kingma explained: “Birds see their territory in the same way as we see our house. Some species of ‘home-owners’ allow other birds to live in their territory and help them to care for their offspring. This may seem logical if the birds living in the same territory and helping each other are related. But this isn’t always the case.

“Home-owners get much more help if the helpers stand to inherit their territory in the future.”

The results also showed that in many species, larger groups are better able to defend the territory, and that helping to improve the group enables territory persistence, which could give a higher chance of inheriting the territory.

Mr Kingma continued: “Moreover, larger groups may expand the territory so that subordinates can split off a part of it, a common route to independent breeding in some species, e.g. laughing kookaburras (Dacelo novaeguineae) and Florida scrub-jays (Aphelocoma coerulescens).”

In addition, researchers say helping behaviour could aid survival, as helpers avoid aggression and eviction by breeders.

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