Telling the difference between Greater and Lesser Yellow Legs in the field can be troubling to many birders. Here are 3 simple ways to distinguish between the two.

1. If they are side by side then it is an easy problem since the 14″ Greater Yellowlegs stands out dramatically from the 11″ Lesser.
2. If they are alone and at a distance the size differences can be disguised. A good tact then is to look at the bill length. In the Greater the bill is one and half times bigger than the cross section of the head (between the base of the bill and the back of the head). That is fairly easy to see. In the Lesser Yellowlegs, the bill length is slightly bigger in this same cross section. One other point about the bills is that the Lesser has a straight bill while the Greater’s is slightly upturned at the tip. This upturn may be difficult to pick up at a distance.
3. These two bird species cab be vocal and can be distinguished by ear. The Greater, being larger is more emphatic and louder in voice. Also the Greater tends to have 3 or 4 tu tu’s in their call – – tu-tu-tu. The Lesser is softer and less aggressive when calling and tends to use two tu tu’s – – tu-tu. In flight these calls tend to be continuous. The number of tu tu’s called is a good rule of thumb but rules of thumbs are not laws of physics so expect some failures in the 2 or 3 rule.

Try these tips out in the field and telling the species apart should be simpler and more precise.