It’s fall migration time and many birds are gearing up for their trek south. Consequently, they may not be in the habitats where they’re usually found during breeding season. Many of them are also sporting their non-breeding plumage or are in some phase of transitioning between plumages, making it difficult to distinguish between one drab brown or grey bird and another. What’s a birder to do?
As an intermediate birder working to become a master birder via the Audubon Society Master Birder program, I want to share with you some tips I’ve learned to help push you to the next level in your own birding adventures. This is the first in a series I call “ID Challenge.”
Telling one shorebird from another is one of the big headaches for birders of any skill level, especially this time of year. While you wouldn’t expect Colorado to have many seeing as it’s fairly far from either coast, the state has a good number of these plucky birds, both resident and passersby. That’s probably because “shorebird” is a pretty deceptive term. While some do enjoy a day at the beach, many shorebirds are just as happy with a rocky stream bank, mudflat, or even a grassy field.
A classic problem in shorebird ID is distinguishing between two very similar long-legged shorebirds, the Greater (Tringa melanoleuca) and Lesser (Tringa flavipes) Yellowlegs. As their names suggest, both Yellowlegs have bright yellow legs. These long, yellow legs along with their lanky bodies help easily set them apart from other shorebirds, but what about differentiating between the two species themselves? Their plumages are very similar, so there’s no help there. It’s easy to tell them apart when they’re together just by size, but what happens when you see them alone?
An easy way to tell a Greater Yellowlegs from a Lesser Yellowlegs is by looking at the bill. Is it thick and blunt-tipped with, possibly, a slight up-curve? If so, you probably have a Greater Yellowlegs on your hands. A Lesser Yellowlegs has a finer, straight, and more pointed bill. The clincher though is the length of the bill. The Greater Yellowlegs’s bill is 1 1/2 to 2 times the length of its head while the Lesser Yellowlegs’s bill is about the same length of the head or just a tiny bit longer.
But what if the bird isn’t cooperating and won’t give you a good side profile or you still can’t quite decide? Another way to tell the two apart is by their voice. Both birds are fairly vocal and both give off short whistles, but the Greater Yellowlegs gives off a greater number of whistles, usually 3-4 in quick succession. The Lesser Yellowlegs, however, gives off a lesser number of whistles, usually 1-2.
So, armed with this knowledge, go forth and see if you can find some Yellowlegs before they’ve all headed south for the winter!