Only two of our North American breeding wood-warblers use a cavity nest: Prothonotary (above photo) and Lucy’s.
Prothonotary nests usually occur in stumps and snags either standing in or near water. An old or abandoned woodpecker hole is typically employed, most often one previously occupied by a Downy Woodpecker or Black-capped/Carolina Chickadee. Nest heights range from 2 to 12 feet above ground or water, with an average of 5 feet in height. Prothonotaries occasionally nest in bird boxes and near buildings.
Lucy’s Warbler is the only cavity nesting warbler in the western USA. This species usually places its nest in four types of cavities: natural cavities in trees (usually mesquite) where the entrance is in a sheltered spot; under loose bark; in abandoned woodpecker holes (especially those of Gila Woodpecker (Melanerpes uropygialis) in saguaros [Carnegiea gigantean] or other trees); and in deserted Verdin (Auriparus flaviceps) nests. Lucy's Warbler occasionally nests in holes in banks, in soap tree yucca leaves (Yucca elata), elderberry (Sambucus mexicana), sycamore (Platanus spp.), or willow/
Lucy's Warbler rarely nests in burrows or depressions in river banks, rocky crevices, deserted thrasher (Toxostoma sp.) and Cliff Swallow (Hirundo pyrrhonota) nests, "pseudocavity" evacuated in mass of debris in tamarisk, or forks in small branches.
