I’ve got a guardian hawk (Image: Harold F. Greeney, Yanayacu Biological Station)

When you’re tiny, it’s good to have big friends in high places. That’s how hummingbirds in Arizona manage to protect their eggs and chicks from being eaten by voracious jays.

The hummingbirds can nest safely on low boughs surrounding a tree that has a hawk’s nest at the top. That’s because of the way hawks hunt, swooping on prey like jays horizontally or from higher up. As a result, jays stay away from a zone spreading out and down from the top of any tree where hawks are nesting.

Jays are agile and can hop around in foliage to rob hummingbird nests, so the hawks’ presence effectively envelops the hummingbirds in a cone-shaped force field that keeps their eggs safe. “The jays are food for the hawks, and the hummingbird eggs are just too small and take too long for a predator like a hawk to find,” says Harold Greeney, director of research at the Yanayacu Biological Station in Cosanga, Ecuador.


Greeney and his colleagues went to the Chiricahua mountains of south-east Arizona, where they mapped the positions of hawk and hummingbird nests, and tracked the movements of jays.

They found that jays avoided raiding hummingbird nests in conical zones beneath the 12 hawk nests they observed over three years. “It fans out roughly 100 metres in all directions from the hawk nest,” says Greeney. Instead, the jays foraged at altitudes above where the hawks were nesting.

However, hawks nests may be raided by coatis, tree-climbing raccoon-like mammals. In years when this happened and hawk nests were abandoned, the jays became much bolder – visiting what had been no-fly zones and taking more hummingbird eggs and chicks than when the hawks were around.

Greeney says that the phenomenon of a key predator providing sanctuary for much smaller species is unprecedented in the bird world.

But he doesn’t think the hummingbirds consciously seek out the protection. “They simply return to sites where they’ve previously had good breeding success, and this happens to be under the hawk nests,” he says.

Journal reference: Science Advances, DOI: 10.1126/sciadv.1500310