How young female birds benefit from an older male partner

A May-December romance brings benefits for young female gray jays mated to older males, according to new Canadian research.

The paper, published this month in the journal Animal Behaviour, used almost four decades of data on a marked population of gray jays in Ontario's Algonquin Park to study how the birds adjust their reproductive habits in response to changes in temperature and other conditions.

Gray jays, also known as Canada jays or whisky jacks, don't migrate south in the winter, instead living year-round in boreal forests across Canada and the northern U.S.

They manage this feat of survival by caching food all over their large, permanent habitats, then retrieving it during the winter months. The small, fluffy birds take advantage of those winter supplies to nest much earlier than most other birds, laying eggs between late February and March.

The researchers found that female gray jays that laid their eggs earlier in the season had the most reproductive success, with a higher survival rate for offspring.

"That's slightly counterintuitive when you're talking about a bird that nests in the winter, because earlier means colder," said Ryan Norris, an associate professor at the University of Guelph and co-author of the paper.

"But it presumably gives them more time for their young to develop over the breeding period."

By breeding early, said Norris, gray jay pairs give their young more time to learn the food caching and retrieval skills that will help them survive the winter.

The benefit of an older male mate

The choice to breed early comes with experience.

Older female gray jays tended to lay their eggs earlier than younger females, possibly because older birds are more effective at finding and caching food for winter.

However, young gray jay females were more likely to lay their eggs earlier — and achieve better reproductive outcomes — when partnered with an older male over a younger male, suggesting that "older male partners may buffer the effects of female inexperience."

The younger females mated with older males made those beneficial laying choices regardless of variations in temperature that might have influenced them to lay later if they had mated with a younger male. This suggests a surprising male influence in female reproductive timing, and shows that social environment can influence gray jays' reproductive choices.

"Nobody's reported this before in birds, this kind of effect that males can have on female laying decisions," said Norris.

Seeking insight into climate change

Although these findings about older males' influence on younger females' reproductive choices are interesting in and of themselves, the researchers set out to learn more about how gray jays reacted to climate change.

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"It contributes towards being able to predict the impact of climate change on populations," said Norris.

"Climate change is affecting wild populations everywhere around the world, and we have to be able to understand how, and we have to be able to predict what's going to happen in the future."

Gray jays are especially good for studying the long-term effects of climate change on reproduction because they have a remarkably long lifespan for such small birds — some of the Algonquin Park gray jays have been known to live as long as 16 years.

Because Algonquin Park represents the southern edge of the gray jays' range, the birds there experience relatively warm conditions, said Norris.

Decades of studying gray jays

The research findings are "partly a lesson on the value of long-term studies," said Norris, who credits co-author Dan Strickland with managing decades of research on the Algonquin Park gray jays and helping to produce such a long-term body of data.

Strickland himself credits Russ Rutter, an Algonquin Park naturalist who started studying the park's gray jays in the 1960s. Strickland continued and expanded the work after Rutter's death in 1976 and continued studying the gray jays even after he retired as chief park naturalist in 2000.

"It's doubtful that there's a study of a marked population in Canada, and maybe even the world, that has been studied as long as this one has," said Strickland.

But Strickland said Algonquin Park's gray jay population is in decline, possibly because of climate change, as the gray jays rely on cold weather to refrigerate their winter caches and provide enough food to feed their young.

Strickland speaks fondly of his years of interaction with the gray jays, which are known for boldly approaching humans in search of food.

"They're cute, and they're fluffy, and a lot of people mark their interest in nature going back to when they had a wild bird actually land on their hand and take food," said Strickland.

"It's a neat bridge between urban man and wild nature."