Hummingbirds hum, sort of by definition. Usually when I notice them in the garden, it’s because it sounds like the world’s biggest, most badass hornet is in the neighborhood. But the other day I noticed a ruby-throated hummingbird in the honeysuckle and it must have been in stealth mode because it wasn’t making any noise whatsoever.
Does the hum of the hummingbird depend on their flight mode or the angle of attack of their wings? Do they make less noise when hovering? Is the noise directional so that it's more perceptible if the bird is heading towards you? Does the hummingbird ever use the buzz as a defense mechanism, deliberately racheting it up in volume so that it sounds threatening?
I have little hummingbird knowledge, but I’ve got a dandy encyclopedia. It didn’t mention anything about differing hums or defense humming, but did mention that there are around 300 different species ranging in weight from 2 to 20 grams, and that smaller hummingbirds have the most rapid wing beats, as much as 80 beats per second. Maybe size or beats per second varies the loudness of the hum. Most are nonmigratory, but the ruby-throated hummingbird you saw can fly 500 miles non-stop across the Gulf of Mexico.
While I am not certain of the precise details of sound production, to my ear the intensity of the sound of a hummingbird’s wings certainly seem to vary depending on flight mode and the orientation of the bird relative to the observer.
Some species of hummingbird definitely use the wing noise as a threat in territorial interactions as well as in courtship. In North American hummers, this is most pronounced in the Broad-tailed and Rufous Hummingbirds.
Roles of the Wing Whistle in the Territorial Behaviour of Male Broad-tailed Hummingbirds (Selasphorus platycercus)
Colibri
Staff Trochilidologist
Which brings up another question. My readings indicate that hummingbirds have almost no fat reserves and have to consume some ridiculous fraction (100%) of their body weight of nectar and insects per day. So a 500 mile flight must be just about the limit of the bird’s energy reserves. How does a brutal migration pattern like that ever get established?
During the days immediately preceeding a long migratory flight hummingbirds go on a feeding binge and may increase in weight by almost 50% (2.5 to 4.5 grams in the case of a Ruby-throat) through temporary accumulation of body fat. This apparently gives them just enough to be able to cross the Gulf of Mexico to Yucatan. However, not all birds in the population attempt this risky flight. Many migrate by land around the Gulf through Mexico, while others may stop off in Cuba or other islands.
[Rosanne Rosanadana]
Who lets them through the border? Where do they get their little passports? Are they smuggling cigars? Marihuanna??? Who is in charge of this operation, anyway?!?!?!?
[/R.R.]