Shorebirds are so-named because they typically feed along shores of rivers, lakes, or oceans. Shallow water tends to be teeming with small animals (such as insects, crustaceans, and juvenile fish) that make up the diets of shorebirds. Estuaries (shallow areas where rivers meet the ocean) are particularly rich in prey, but shorebirds may even find habitat in the shallow waters of a flooded agricultural field or seasonal pool of water. Shorebirds are adapted to take advantage of shallow-water food resources wherever they occur. But, shallow water habitats tend to be unstable, vulnerable to drying out, draining, or freezing. With long, tapered wings and light bodies, most shorebirds are excellent flyers, able to travel to other feeding areas when necessary. Shorebirds include some champion migrators, such as terns and plovers that travel many thousands of miles each year between breeding and overwintering areas