Bitter Lake is a favorite roosting place. This Eurasian bird was first seen in New Mexico at Bitter Lake. Bird watchers from every state and most of Europe have taken in the sights. Ducks numbering between 5,000 and 20,000 and geese numbering 20,000 to 40,000 can be observed during fall migrations. Large numbers terminate their migration in this area while others continue into Mexico.
Food is provided on the refuge by native aquatic plants as well as cultivated crops.
Many of the birds leave the refuge daily to forage in grain fields throughout the Pecos Valley. Some thirty species of waterfowl have been recorded. Canada Geese historically make Bitter Lake their winter home. Snow geese made their first appearance here in the early 1960s. The major portion of the world's population of lesser sandhill cranes winter in West Texas and Southeast New Mexico.