Even though they are able to fly quickly and blend into the surroundings, hummingbirds face many threats in the wild. Their biggest predator is the family of cats, but since they are so small (7.5–13 cm), larger types of birds are their enemies too. The good news is that hummingbirds in the Chiricahua Mountains of Arizona have found an interesting strategy to avoid predatory birds like Mexican jays: they use hawks as guard dogs.
This behavior was studied over the course of three seasons by ornithologist Harold Greeney and his colleagues. For their study, recently published in Science Advances, the team surveyed 342 hummingbird nests and 12 hawks. The scientists found that hummingbird nests built within 984 feet (300 meters) of active hawk nests have a daily survival rate of 19 percent. Outside of hawk territory, the daily survival rate drops to a mere 6 percent. Even more interesting is that building within the 560-foot (170 meter) of active hawk nests boosts the survival rate of the tiny birds up to 52 percent.
The explanation? The Cooper’s hawk and the northern goshawk, which are particular to the area, prefer to pursue their prey from higher vantage points. Jays – which are one of the biggest threats to hummingbird eggs and chicks – are aware of the danger. As a result they prefer to forage higher up in the forest canopy and avoid any place lower than where the hawks are perched quietly waiting for prey to pass below. This no-fly zone for jays creates a cone-shaped area of safety for hummingbird.
A mystery remains, though. Scientists haven’t discovered yet how the hummingbirds know to build near hawks. It is possible that they look for spots where other hummingbird nests are successful, or they simply learn the hard way by trial and error.