In the Chiricahua Mountains of Arizona, black-chinned hummingbirds use a different kind of home security system. These small birds seek protection from neighboring northern goshawks and Cooper's hawks to defend their nests from Mexican jays.
A recent study discovered that about 80 percent of hummingbird nests built in this area are clustered near hawk nests. This is because the hummingbirds are small enough to live near hawks and be unheeded, while the jays are on the large raptors' radar and have to fly higher above to avoid being eaten. This tactic increases the hummingbirds' daily survival rate to 31 percent, compared to that of those living outside of hawk territory, where the daily survival rate drops to roughly six percent.
An international team of researchers, led by Harold Greeney, a biologist and the founder and director of the Yanayacu Biological Station Cosanga in Ecuador, observed patterns of hummingbirds, hawks and jays in the Chiricahua Mountains throughout three nesting seasons. Using statistical models, the researchers discovered that more than one-third of the jays' foraging behavior can be explained by hawk presence, meaning they would choose when and where it was best to search for food in order to avoid being eaten by the hawks.
The jays appear to be quite observant though. The researchers noticed that when the hawks left their nests the jays would destroy them. During one season alone, they took over four hawk nests and, within two weeks, attacked all surrounding hummingbirds' homes.
Their study was recently published in Science Advances.
A video of the egg-robbing jays can be found online.
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