One Bird Species or Two?
Here’s a handy phrase likely to get you odd looks if said near non-birdwatchers: sexual dimorphism. Far from being something you’ll see a shocking exposé on an afternoon chat program, it’s simply a scientific term that states the male and female of a single species look different from one another.
Some species, such as American Robins, show little if any sexual dimorphism. Other bird species, such as the Black-headed Grosbeaks caught on Audubon BirdCam by John at The Well-read Naturalist in Scappoose, Oregon, exhibit so much sexual dimorphism that male and female Black-headed Grosbeaks only vaguely appear to be the same species.
Indeed, early ornithologists were often fooled by sexually dimorphic birds. Both Black-headed and Rose-breasted Grosbeaks, as well as Red-winged Blackbirds were all at one time or another listed as two different species each. For more examples of bird species displaying sexual dimorphism, check out the Wingscapes Photo Gallery to see if you are a master of identification.