With peak migration of many species past, this week will see diminish but still evident light movements in the West, while the East continues to see increasingly scattered late season moderate to isolated heavy movements. Birds on the move this week will include late season shorebirds including Red Knot and White-rumped Sandpiper, Alder and Willow Flycatchers, and Mourning and Blackpoll Warblers.
Light winds and variable winds allow the last light to isolated moderate movements of birds to occur at the beginning and end of the forecast period. In between these periods of movement, increasing precipitation scattered locally across the region will inhibit migration where it occurs, beginning late in the weekend in the Pacific Northwest and spreading East into the northern and central Rockies by midweek. Birds on the move this week will include Common Nighthawk, Western Wood-Pewee, Willow Flycatcher, Veery, and Cedar Waxwing.
Nearly the last of the moderate and isolated heavy movements of the spring will occur in the coming week for the region, particularly as the weekend begins. Local fallouts and concentrations are likely in portions of the central and northern Plains states where birds meet rain. By the beginning of the week, although winds remain mostly favorable, the threat of precipitation and storm activity increases and shuts down movement in many areas over the days that follow. Additionally, portions of the northern Plains will see marginal and even unfavorable winds, which will also shut down movements. The degree to which this late season suite of movements is shut down will largely determine how much remaining migration is evident in the latter portion of the forecast period (and into very early June). Birds on the move this week will include late shorebirds, Yellow-billed Cuckoo, Red-eyed Vireo, Connecticut Warbler, and Nelson’s Sparrow.
Upper Midwest and Northeast
Strong high pressure brings more April like conditions to the region East of the Appalachians, largely shutting down movements through the weekend. As winds diminish and become less northerly and westerly, increasing moderate and even locally heavy movements may occur, though not until at least Monday night. Meanwhile, to the west, conditions become more favorable over the weekend as southerly flow returns. Moderate and locally heavy movements will occur, and fallouts and concentrations are likely in the Great Lakes to end the weekend. More favorable conditions spread over the entire region by Monday, facilitating the last major push of migration for many species this spring with moderate to locally heavy movements. By late week, as the threat of precipitation increases, and the number of migrants begins to dwindle, remaining movements will shut down in more western areas. Birders in the central Appalachians should watch the distribution of precipitation closely, as the southerly flow and scattered precipitation may bring a last late season waterbird and shorebird fallout or two in your areas by late in the week. Birds on the move this week will include Yellow-bellied, Alder and Willow Flycatchers, Red-eyed Vireo, Cedar Waxwing, and Mourning Warbler.
Gulf Coast and Southeast
Western portions of the region will see the last moderate and isolated movements beginning to fade over the course of this week, beginning with steady movements over the course of the weekend. More eastern areas will see more marginal conditions, but locally moderate movements will occur given the late date. These movements will begin to dwindle, noticeably, over the course of this week, as migration begins to wind down for most species. By midweek, moderate movements represent the peak, with some locally isolated heavy movements continuing in Texas. Birders along the Texas coast should pay particular attention to the precipitation forecast for late in the week on Thursday and Friday – few people continue to bird actively in coastal stopover habitat this late in the season, and vagrants and late migrants could be lurking in the conditions forecast late in the week. Birds on the move this week will include the continued presence recently arrived Gulf Stream pelagics, Red-necked Phalarope and Ruddy Turnstone, and a few late migrant Neotropical passerines including Yellow-bellied Flycatcher, scant Bicknell’s Thrushes, and Mourning Warbler.