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Hummingbirds are no exception when it comes to snazzy performances, as males of many species perform spectacular courtship dives. Broad-tailed hummingbirds (Selasphorus platycercus) fly up to 100 feet in the air before sweeping down toward a perched female, then climb back up for a subsequent dive in the opposite direction. At the Rocky Mountain Biological Laboratory in Gothic, Colorado, home to a population of breeding broad-tailed hummingbirds, researchers from Princeton University have been investigating how hummingbirds combine speed, sound and color in their displays. Their work appears in the Dec. 18 issue of the journal Nature Communications.
"The dives are truly amazing feats for such small birds," said Benedict Hogan, a postdoctoral research associate in ecology and evolutionary biology and the study's lead author. "We know from previous work that the males can reach really high speeds. They combine that speed with intriguing noises generated by their wing and tail feathers, and of course with their brightly iridescent plumage." But how do these different components fit together, and what might a dive sound like and look like to a female?
Hogan - Mary - Caswell - Stoddard - Assistant
To explore this, Hogan and Mary Caswell Stoddard, an assistant professor of ecology and evolutionary biology and the study's senior author, created video and audio recordings of 48 dives performed by wild male broad-tailed hummingbirds. They then used image-tracking software to estimate each male's trajectory and speed throughout the dive. Combining these estimates with the audio data, the researchers measured the precise time at which the males produce a mechanical "buzz" with their tail feathers.
To incorporate information about iridescent plumage color, which is difficult to extract from the video recordings, the team headed to the American Museum of Natural History in New York City. Using a multi-angle imaging technique and an ultraviolet-sensitive camera, they photographed broad-tailed hummingbird specimens. Hummingbirds are tetrachromatic --...
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