Those that aren’t familiar with the golden hoods of Catholic notaries may prefer the name Golden Swamp Warbler, which evokes the bird’s habitat as well as its color. Its loud ringing song reverberates through southern swamps and river edges during the spring and summer.
Spring migration in this species begins in mid-March, with arrivals on the Gulf Coast and at the more southerly breeding areas. The species winter in both Middle American and the Caribbean, so its arrival in the southeast is across a broad front and not along a more particular migratory path. It is not until mid-April that the species arrives on its more northerly breeding areas, and in some areas the first first birds do not appear until early May. A notoriously early fall migrant, Prothonotaries leave the breeding grounds starting in early August and are largely gone by early September. Like many southern breeding warblers, their fall migration is not pronounced, with most birds vacating the United States largely undetected by birders.
Although we’d like to make these models “smarter” when it comes to how bodies of water are used (i.e., our models for waterbirds tend to be not that good), there are some really neat patterns appearing here. While Prthonotaries at the southern edge of their range prefer swamplands, those at the northern edge of the range are restricted to river systems. Watch how the early spring migration proceeds up the lower Mississippi River and then in May watch the small, northern-breeding population snake its way along the Mississippi as they fill in the most northern breeding areas. The fact that the model is tying this species so closely to that major river valley shows that it is accurately getting at the main determining factor for Prothonotaries in the Upper Midwest. At times, the entire Mississippi is highlighted for us by the high Prothonotary occurrence.
[Note that, like Kentucky and Yellow-throated Warblers, the model over-extrapolates at the northern edge of the range. Prothonotaries occur in New York, Wisconsin, and Minnesota, but are extremely local and not nearly as widespread as the model suggests. Ongoing research, in addition to more data, will help us correct for this.]