Hummingbirds have two creative strategies for flying through tight spaces

Anna's hummingbirds (Calypte anna) were studied. They are among the most frequent West Coast hummingbirds. The ping-pong ball-sized birds feature iridescent emerald feathers and flashing pink neck plumage.  

Berkeley researchers created a two-sided flight arena for the experiment. The hummingbird was trained to fly through a 2.48 square inch gap in the arena partition using alternate rewards.  

They only supplied a flower-shaped feeder with sugar water if the bird returned to the feeder on the other side through one of the openings. This encouraged the 4.7-inch-winged birds to fly around the arena.  

The crew then replaced the flying arena's separation with smaller oval and circular holes ranging from 4.7 inches to 2.3 inches in height, width, and circumference. High-speed cameras captured the birds' movements to see how they navigated the apertures.  

Next, the team created a computer software to track each bird's bill as it passed through each hole. For hummingbird wing positions as they passed, the algorithm located their wing tips.

Hummingbirds hovered in front of the circular opening to assess its size in the first tactic. They then moved sideways, stretching forward with one wing and sweeping the other back like a cross.

Second, the birds swung their wings backwards to pin them to their bodies. After shooting through the beak, they swept their wings forward. After passing through the circle, they flapped again. As they became braver and more comfortable, all hummingbirds in the study used this method.