Mid-July through October
Peaks early Sept. through mid October
Each year after nesting is completed and young are fledged, millions of seabirds, waterfowl, wading birds, raptors, shorebirds, and land birds (such as hummingbirds and swifts, flycatchers, warblers, vireos, thrushes, and orioles) move south from northerly breeding sites to spend the winter in warmer climates. Some may fly south only as far as Louisiana and make coastal Louisiana their winter home. Others pass through and continue further south to the West Indies, Mexico, Central and South America. Louisiana’s diverse habitats, swamps, marshes and forested wetlands provide food and shelter for fall migrating birds.
Where do the migrants come from?
Coastal Louisiana is located at the southern end of the Mississippi or Central Flyway. They arrive from Western Alaska and across Canada, the northern ends of the Mississippi flyway on the Great Plains, and eastern parts of the United States. Migrating birds are funneled to the Louisiana coast as they fly southward. They are channeled to Louisiana by the geographic slope of the continent and continental air currents. As they approach the Gulf of Mexico their route is either over open water across the Gulf of Mexico (trans-Gulf) or they follow the western coastline of the Gulf (circum-Gulf). Fall migration routes for some species are different in spring and fall; species generally absent from Louisiana’s coast during spring migration can easily been seen during the fall migration (Alder Flycatcher, Mourning Warbler, Prairie Warbler). Some species common during spring migration are absent during fall migration (American Golden Plover, Hudsonian Godwit, White-rumped Sandpiper, and Blackpoll Warbler).
Fall migration is of long duration spanning several months and beginning as early July and extending into early December. Aggregations of migrating Purple Martins appear in late June. Huge numbers can be seen congregating in July on the New Orleans Causeway, which connects East Florida Loop 12 and Orleans Loop 2 loops, especially (site 7-2). Shorebirds start to return to Louisiana’s rice fields by early July. The first adults are returning from their Arctic nesting sites; and young birds follow typically about a month behind adults. Great Crested and Least flycatchers and Black-and-white warblers appear in coastal cheniers also during July. Species diversity increases through August. September and October offer the best opportunities to see the greatest species diversity of southbound migrants along the coast.
Fall migration is more leisurely than that of spring. Periods of southerly flow may concentrate more birds, but in general fall bird watching is not as hit or miss in the coastal cheniers as it is during spring migration—there are always migrants to look at. An additional challenge for fall bird watchers is that many songbirds will be in unfamiliar, often drab, winter plumage. This is especially true for many warblers that were so brightly colored and easily identified in spring, such as Chestnut-sided and Bay-breasted. Sometimes a glimpse of an unidentifiable warbler is referred to humorously as a “confusing fall warbler”.
Southbound migrants are rarely as concentrated as they can become during a spring “fall-out,” but weather does play a role. Occasionally birds “fall-out” during the fall. During September and October, large numbers of raptors and swallows can be seen moving west along the coast following a front. Ducks and geese are typically using the north winds of later fronts. Just as tired migrants can be seen coming in off the Gulf during spring migration, occasionally birds are accidentally blown out over the Gulf during the night by strong north winds. From sparrows to geese, these birds are often seen making their way back north from out over the Gulf.