As April passes into May, many migratory birds leave the tropics of Central and South America in search of bountiful summer resources in the sub-tropical United States. Among them, the very charismatic Prothonotary Warbler flies from the northern tropics to the hospitable habitats of the United States. Prothonotary warblers live in forests near bodies of slow-moving water where they can hunt for insects and nest in cavities in trees. The cypress swamps of Louisiana are about as good as it gets for a prothonotary warbler, and they stay from April to August.  If you get out into the swamp during the summer, look for their bright yellow figures darting through low-lying foliage.
Prothonotary warblers have experienced a population decline in recent years that experts attributed to the destruction of their wintering habitat in the tropics. To improve breeding success and survivorship, the Audubon Society and other ornithological enthusiasts have encouraged people to install nest boxes that help to protect warbler nests from failing. Many natural threats exist in swamps for warblers, including a variety of snakes, birds of prey, and mammals. Since brown-headed cowbirds will use prothonotary nests to lay their eggs in when given the chance, nest boxes are suggested to have a 1¼“ hole to prevent larger birds from entering the box but still allow the warblers to enter. Boxes are not left on the ground, and are often mounted on poles. Some predators can climb, so many boxes have a skirt/collar that prevents snakes, raccoons, and cats from climbing the poles into the nests. More guidelines for a good nest box can be found at https://nestwatch.org/learn/all-about-birdhouses/features-of-a-good-birdhouse/.
 Petit, L. J. (1999). Prothonotary Warbler (Protonotaria citrea), version 2.0. In The Birds of North America (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.408
 Kaufman, Kenn. “Prothonotary Warbler.” Audubon, National Audubon Society, 10 Mar. 2016, http://www.audubon.org/field-guide/bird/prothonotary-warbler.
Brannon, Peter. “Adult Male.” All About Birds, The Cornell Lab of Ornithology, Florida, 14 Sept. 2016, http://www.allaboutbirds.org/guide/Prothonotary_Warbler/id.