The prothonotary warbler is a small, brightly-colored yellow bird that frequents the tidal swamp forest in spring and summer. It is the only wood warbler in the eastern US that breeds in tree cavities. Although the neo-tropical migrant is small in stature, it has a loud, distinctive call. Visitors to the wetland boardwalk can listen for the zweet, zweet, zweet, zweet, zweet, zweet song all on one pitch. The species is declining over much of its breeding range (Florida to Wisconsin) but thriving at Presquile National Wildlife Refuge.