(Image: Harold F. Greeney, Yanayacu Biological Station)
“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 at the Yanayacu Biological Station in Cosanga, Ecuador.
Greeney’s team studied the birds in the Chiricahua mountains of Arizona over three years and found that jays avoided raiding hummingbird nests found in each conical zone fanning out from the 12 hawk nests on treetops they observed. This, they say, is because of the way hawks hunt, swooping on prey including jays from higher up. This effectively envelops the hummingbird nests in a cone-shaped force field avoided by the jays.
However, when hawks abandoned their nests following raids by coatis, tree-climbing raccoon-like mammals, the jays became much bolder. They visited what had been no-fly zones and took more hummingbird eggs and chicks than when the hawks were around (Science Advances, doi.org/7hn).
Greeney 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.
This article appeared in print under the headline “Hawk’s invisible force field protects hummingbird nests”