Unlike most warblers that winter in the Neotropics, the Yellow-throated Warbler is an early spring migrant. Across much of the eastern United States there are only five expected March warblers: in addition to the short-distance migrants that winter primarily in the U.S. (Pine, Palm, and Yellow-rumped), two warblers winter almost exclusively in Central America, yet return in March much earlier than other warblers that winter in the same area: Louisiana Waterthrush and Yellow-throated. Sure, some other species return to Gulf Coast states in mid- to late March, including Prothonotary, Ovenbird, and others, but the waterthrush and Yellow-throated really do stand apart in areas to the north as among the earlier returnees.
Notice the northward movement into the Southeast by early March, and notice how evidence of migration is essentially gone by mid-April. Yellow-throated Warbler is a species that does not have a pronounced fall movement. In September it is possible to find a few migrants that are clearly on passage, but many birds seem to pass through undetected. It may be that some of the shorter-distance migrants (i.e., those moving from the southern U.S. to northern Mexico) may complete their migrations in just a few, or even in a single, hop. This might explain why species like Kirtland’s Warbler, Yellow-throated Warbler, and Prothonotary Warbler are seen comparatively rarely on the ground during migration. For Yellow-throated Warbler, the sudden appearance in breeding areas and the slow fade away in fall are both apparent on the animated map above. Conversely, Blackpoll, Black-throated Green, and other boreal forest breeders rank among the more common migrant warblers, perhaps because they need to refuel more on migration and complete their longer movements in multiple flights with refueling stops in between.
[Note: The faint Adirondacks signal is an artifact of sparse data and how the model attempts to compensate for that. This seems to be due to the association of Yellow-throateds with forest, and evergreen forest in particular, in southern parts of the same regional model. As the dataset grows, we will be able to use smaller and smaller regions for the models which will make issues like this go away. For now, the predictions in the Adirondacks (where data are sparse) are drawing from nearby areas, where Yellow-throateds do occur. This is a known issue and a research direction for us to minimize it.]