Wednesday, September 06, 2006

Got baby hummingbirds?

Every now and then I receive an email that goes something like this:

"I've been seeing a baby hummingbird coming to my flower garden. It's a tiny little thing compared to other hummingbirds I see. How long does it take them to become fully grown?"

Again, we'll turn to Cornell's BNA on-line in order to investigate the possibilities. In Wisconsin the overwhelmingly predominate hummingbird species is the Ruby-throated Hummingbird:

"Fledgling mass substantially greater than normal adult mass (4.85 vs. 3.3 g for average adult female). Mass often decreases sharply, presumably until foraging skills develop."

Growth of Ruby-throated Hummingbird nestlings (solid line, mean weight in grams, n = 4; dashed line, mean exposed culmen length in millimeters, n = 4; RRS). Figure adapted from Calder 1993.

Some recently fledged Ruby-throated Hummingbirds may actually appear to be slightly larger than an adult. So, what are these people seeing in their flower gardens? There are a few possible explanations:

  • It's the rare and exotic Northern Pygmy Hummingbird.
  • An observational error judging the size of a typical hummingbird.
  • It's an insect - a Hummingbird Clearwing Moth.

It's fascinating how adamant some people can be, persisting in the belief they've observed a bird and not an insect even after being presented with the evidence and a reasonable conclusion. But if you're certain that it's a bird and not an insect, please, take a photograph of it if you can!

Ruby-throated Hummingbird © image 2006 Mike McDowell

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