Researchers have discovered that birds, including great tits (Parus major), choose to nest near birds they got along with the previous winter. By choosing friendly winter flockmates as neighbors, birds can potentially reduce territorial disputes and better cooperate in fending off predators. The findings are in a paper that was just published in the journal Ecology Letters.
A team of researchers from the University of Oxford studied great tits, noting that they make a good general model for studying bird behavior. The team observed flocks of great tits in Oxford, UK on a site that has been monitored since the 1960s. About 90% of the birds had already been tagged with identifying microchips. The researchers used data from observations and the microchips in order to study social interactions.
The team found that once the spring season arrived, birds preferred to nest near birds that were part of their winter social network. They tended to set up their nests next to birds they had been friendly with, choosing their closest “friends” as next-door neighbors. This trend was consistent regardless of the year, previous nesting choices, age, and other factors.
There are a couple of possible benefits to nesting with familiar birds. Previous research has already shown that friendly birds are more likely to engage in “mobbing” behavior, ganging up on large predators to scare them away. Birds that already know each other will also waste less time and energy on aggression displays and territorial disputes. The authors also speculate that there may be other benefits, such as less reproductive competition.
The new study will help scientists better understand bird social behaviors. Great tits make good models for studying general social behavior in flocking birds. The research team found that their winter social networks determined where they nested in spring. This may offer benefits such as increased cooperation and reduced aggression. Future studies will further investigate the benefits of choosing familiar birds as neighbors.
Josh A. Firth & Ben C. Sheldon. Social carry-over effects underpin trans-seasonally linked structure in a wild bird population. Ecology Letters (2016).