Aptly named, Greater Yellowlegs are larger than Lesser Yellowlegs and have long, yellow legs. This species is migratory with the first birds typically arriving in Maine in the month of April, earlier than most other shorebird species. Though they breed in marshes to our north, individuals can be found in proper habitat in New England through the month of November.
When they occur alongside Lesser Yellowlegs, their differing size makes them easy to sort out. When observing a lone bird, try to assess the relative length of the bill. Is it 1.5 times longer than the head (as in Greater), or about the same length as the head (as in Lesser)? And whereas a Lesser's bill is straight, the bill of a Greater is usually slightly upturned.
Another useful way to sort them out is to listen for their calls. Greater Yellowlegs have big voices and often give 3-5 notes (dew dew dew) in quick succession. Here's a sample:
Compare their loud calls with the less emphatic, usually paired or single notes of the Lesser Yellowlegs.
To learn more about these long-legged shorebirds, visit All About Birds.