Not So Easy To Tell 'Em Apart

Even with every seeming advantage, it is still a real challenge for me to readily distinguish a Downy and Hairy Woodpecker. Take this BirdCam photo from earlier this week. At first blush this appears to be a beautiful side-by-side comparison of the two species. That's what it looked like to me. The suet cage offers a "yardstick" for sizing birds, and we know for certain that the bird on the left is a female Downy. So that makes the larger right hand bird a male Hairy, right? Well, there are problems. One is that the right hand bird's bill simply isn't long enough. And the left hand bird is farther away from the lens and is leaning forward, i.e. is foreshortened. Knowing the dimensions of the suet basket, I deduce that the left hand bird is almost four inches farther away and thus looks relatively smaller. All in all, this is a classic optical illusion. Both birds are Downys. And thus we learn that it isn't necessarily a cinch to distinguish these two similar species---even with help.