|In the SF Bay Area, we get Lesser Yellowlegs passing through in Fall migration where they can be seen together with Greater Yellowlegs, which are winter residents here. The two species are easily separable by size when seen together, as above and below, Greater being much larger, but size isn't always easy to judge on a bird seen alone. The call helps: two syllables for Lesser, usually three for Greater. If they don't call, the size, shape, and coloring of the bill is the best identification mark. The Lesser's bill is typically about as long as the head, while the Greater's is half again as long. The Greater's bill is usually proportionately thicker, particularly at the base, paler toward the base, and slightly upturned, while the Lesser's is more uniformly colored and straight.