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Hormone similarity helps bird couples stay together

GreatTit002My husband and I — total opposites. He's neat, I'm messy. He's early, I'm late. He dislikes socializing, I love to go out with friends. He digs meat and potatoes, I'm a veggie. And I could go on.

So if we were a type of European songbird called the great tit, I'm afraid we wouldn't be together. Great tits choose mates quite similar to each other, with a recent study from the Netherlands Institute of Ecology showing they even have similar hormone levels. And those levels converge the longer the birds are together.

Researchers, who presented at the 2015 annual meeting of the Society for Integrative and Comparitive Biology, measured the levels of corticosterone, a stress hormone, in breeding pairs of great tits. Pairs with similar levels of hormones were also more likely to have more healthy babies. "For at least three years, the pairs that stay together increase their similarities year after year after year," ecologist Jenny Ouyang, PhD, said in a release.

Pairs with dissimilar levels were more likely to "divorce" or break-up, a costly move in the avian world when being without a mate reduces your chances to reproduce. Some researchers have speculated that coordinating the feeding of the babies might lead the partners to have more similar hormone levels. But the exact mechanism remains unknown.

Thankfully, my husband and I can talk, hopefully avoiding the need to compare our hormone levels, which I'd bet are quite different, and growing more so every day.

Previously: "Love hormone" may mediate wider range of relationships than previously thought, Stress hormones moonlight as immune-system traffic cops and My couple's match: Applying for medical residency as a duo
Photo by Shirley Clarke

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