It is not always easy to distinguish the Lesser Yellowlegs from the Greater Yellowlegs, which also occurs in Puerto Rico.
However, the Greater Yellowlegs has a longer bill (noticeably longer than the head) than the Lesser Yellowlegs (the bill is as long as the head).

1st, 2nd & 3rd photo: Playa Tamarindo, Guánica State Forest, Puerto Rico, 19 January 2026
4th photo: Parguera Marina, Puerto Rico, 18 January 2026
5th photo: Cambalache area, Puerto Rico, 15 January 2026