New World wood-warblers (that are not closely related to the various Old World warblers in the Eastern Hemisphere (e.g., Europe, Asia) are often identified to number as 112-115 species, occurring among 24-26 genera. The centers (or “epicenters”) of their breeding areas occur in eastern North America, the West Indies, Mexico and Central America, and Andean South America.
The majority of northern-latitude breeding species migrate, but many island and tropical species are sedentary. Many of these latter species remain close to their birthing areas or perform short-distance, post-breeding altitudinal/elevation migrations.
As for myself, I often see 20-30 wood-warbler species during early May when I return to homecoming birding forays in the Midwest (and, concurrently, attend the annual Wisconsin Society For Ornithology conference).
This year, I was lucky to visit Wisconsin both in the spring and fall to search for neotropical migrant species, including wood-warbler family members.
In so doing, I totaled 23 in the spring and 16 last month.
All of these species are rare to absent by November in Wisconsin, except for the occasional remaining American Redstart, Common Yellowthroat, Palm Warbler, and Yellow-rumped Warbler. The latter three may sometimes be detected during southern Wisconsin Christmas Bird Counts, with Yellow-rumped the most typical one seen.
In contrast, my n. CA residency, yields more warbler species during the breeding season — a result that surprises many people because the West is thought to host far fewer warbler species. For example, in Marin County (Bay Area) where I live, I often detect at least eight warbler species annually and, in the Sierra Nevada Mountains (near Yuba Pass and/or amid the Gold Lakes country off of Highway 49 near Bassetts), I sometimes successfully sleuth out nine warbler species.