If you want to see the ping pong ball–sized nest of a hummingbird up close, start by searching for a hawk. A study published today in Science Advances shows that hummingbirds use the proximity of hawks’ nests as protection from predatory birds like jays.
Ornithologists knew that hummingbirds tend to build their nests in clusters near hawks' nests, but they didn't know why. Over the course of three seasons, researchers in Arizona surveyed 342 hummingbird nests that had been built around 12 hawks’ nests, six of which were unoccupied. Only one-fifth of the hummingbirds set up camp near the abandoned nests. The majority clustered around nests that were still active. The hummingbird nests that were situated within hawk territory had a higher survival rate than those that weren’t.
Because hawks prefer to pursue their prey from higher vantage points, jays will avoid foraging any place lower than where the hawks are perched. This no-fly zone for jays creates a cone-shaped area of safety for hummingbirds that starts at the hawk’s nest and grows wider the lower it gets. Jays pose one of the biggest threats to hummingbird eggs and chicks, and hawks provide them with what’s essentially an enemy-free area.
This idea was further supported after four of the active hawks’ nests were destroyed by predators. After two weeks without the hawks’ protection, the survival of the hummingbird nests had dropped down to nearly zero. It pays to have neighbors who've got your back—especially when you lay eggs the size of a jellybean.
All Photos Courtesy of Harold F. Greeney, Yanayacu Biological Station