Male Western Bluebirds Benefit From Staying In Mom's Nest Longer

It may be in the benefit of a young male western bluebird and his parents' lifespan for him to stick around with his for another year in their nest before building his own, according to recent findings published in the journal Behavioral Ecology.

Not only do female western bluebirds show an age bias--preferring older males--but behavioral ecologists have found that when sharing the workload with parents, this cooperative system equals a survival advantage. For long-lived species like bluebirds that can survivel for up to eight years, males can also increase their reproductive fitness throughout their lifetime (the representation of their alleles in the next generation) by delaying breeding and helping out in the meantime. 

"If you have this combination of an age bias - such that young males are not likely to sire offspring in another male's nest but old males are - and if helpers and their parents have a survival advantage, you can get this evolution of helping behavior even in systems with high rates of EPP," said lead study author Caitlin Stern, an Omidyar Fellow at the Santa Fe Institute, in a news release. 

The behavioral ecology literature is beginning to acknowledge the importance of considering a species' full life history when studying behaviors, added Stern. "Our study is a case-in-point for the need to do this," she concluded. "An individual's fitness accumulates over its lifespan, and we need to take that into account when we're looking at the evolution of behavior."

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