Changeable conditions in the West and the East bring pulses and pockets of moderate to very heavy movements this week among numerous disturbances moving east across the country. Species on the move this week will include numerous shorebirds, Yellow-billed and Black-billed Cuckoos, Alder, Willow, and Yellow-bellied Flycatchers, numerous warblers such as Northern Waterthrush, Mourning Warbler, Connecticut Warbler, Tennessee Warbler, Cape May Warbler, Northern Parula, Black-throated Blue Warbler, Palm Warbler, Yellow-rumped Warbler, and Lincoln’s, White-throated, and White-crowned Sparrows.
Arrows show wind speed and direction (arrow points in the direction to which wind is blowing) 100 m above ground level. Areas with southerly winds are colored red; northerly winds colored blue. Accumulated precipitation (in 6 hour intervals) is green, outlined by white. Broadly speaking, areas of the map in red will experience conditions that are favorable for migration, and areas where red and green (and red and blue) intersect and overlap may experience migrant concentrations and fallouts as migrants interact with precipitation.
Favorable conditions are scattered widely across the region to begin the weekend, and moderate movements co-occur with these areas. By the end of the weekend, these conditions will spread across much of the region with the exception of portions of the Great Basin and central Rockies, and widespread moderate movements are likely. But following the greatest extent of favorable conditions and the movements that associate with them, the scenario changes: moderate movements becomes increasingly restricted to the Desert Southwest over the course of the work week, as a low pressure system moves into the central Rockies. The effects of the low pressure system will continue through the end of the period, with scattered precipitation occurring in a number of areas. Light to moderate movements will occur where favorable conditions persist, but birders should watch the areas of precipitation for later-season migrant concentrations particularly in the central and southern Rockies. Species on the move this week will include American Wigeon, Bufflehead, Dunlin, Least Sandpiper, Western Sandpiper, Long-billed Dowitcher, Wilson’s Phalarope, Western Wood-Pewee, Willow Flycatcher, Cordilleran Flycatcher, Eastern Kingbird, Gray Vireo, Red-eyed Vireo, Gray Catbird, Northern Waterthrush, Orange-crowned Warbler, Yellow-rumped Warbler, Townsend’s Warbler, Green-tailed Towhee, White-crowned Sparrow, Golden-crowned Sparrow, Blue Grosbeak, and Bobolink.
A slow start to the weekend quickly gives way to widespread favorable conditions by the end of the weekend, when heavy and even very heavy movements will be widespread. These movements will likely continue during the work week, but primarily in the southern Plains as high pressure farther north near the border keeps movements substantially lighter in those areas. By the end of the week, favorable conditions are again more widespread, but scattered precipitation and pockets of unfavorable winds are forecast. Birders should watch these areas carefully, as they may concentrate late season waterbird and land bird migrants. Species on the move this week will include Lesser Yellowlegs, Least Sandpiper, Yellow-billed Cuckoo, Black-billed Cuckoo, Common Nighthawk, Western Wood-Pewee, Yellow-bellied Flycatcher, Acadian Flycatcher, Alder Flycatcher, Willow Flycatcher, Blue-headed Vireo, Ruby-crowned Kinglet, Brown Thrasher, Orange-crowned Warbler ,Nashville Warbler, Yellow-rumped Warbler, Connecticut Warbler, Hooded Warbler, Cape May Warbler, Bay-breasted Warbler, Pine Warbler, Canada Warbler, Yellow-breasted Chat, Chipping Sparrow, Clay-colored Sparrow, Vesper Sparrow, Lincoln’s Sparrow, White-throated Sparrow, Harris’s Sparrow, and White-crowned Sparrow.
Upper Midwest and Northeast
Moderate and heavy movements in New England ahead of a slow moving frontal boundary provide the action that kicks off the weekend. Birders in New England should pay close attention to the interactions between migrants and the frontal boundary, as the potential for fallouts and concentrations exists, particularly in Maine and in the Canadian Maritimes. As this front passes, unfavorable conditions keep movements mostly light to moderate, despite the northerly flow. But patches of more favorable conditions may allow for higher densities to occur. As high pressure gradually drifts east, more favorable conditions build from the west, and moderate to heavy movements follow suite in the Mississippi River valley and Great Lakes to begin the work week. These conditions and the moderate to heavy movements associated with them spread over much of the region by the middle of the week, but precipitation will shut down movements and concentrate birds where it occurs. Furthermore, as the next disturbance moves through the region, increasingly unfavorable conditions expand over much of the region and diminish movements to light to moderate levels. Note, however, that portions of the coast Northeast continue to experience favorable conditions for heavier movements through Thursday night before the whole region sees northerly flow and scattered precipitation at the end of the week. Species on the move this week will include Sooty Shearwater, Solitary Sandpiper, Lesser Yellowlegs, Ruddy Turnstone, White-rumped Sandpiper, Semipalmated Sandpiper, Arctic Tern, Common Tern, Olive-sided Flycatcher, Eastern Wood-Pewee, Yellow-bellied Flycatcher, Alder Flycatcher, Willow Flycatcher, Cedar Waxwing, Ruby-crowned Kinglet, Northern Waterthrush, Mourning Warbler, Black-and-white Warbler, Tennessee Warbler, Nashville Warbler, Cape May Warbler, Northern Parula, Black-throated Blue Warbler, Palm Warbler, Yellow-rumped Warbler, Black-throated Green Warbler, White-throated Sparrow, and White-crowned Sparrow.
Gulf Coast and Southeast
Moderate to heavy movements are the norm in the western portions of the region for the weekend, while much less extensive and intense movements occur farther to the east. The beginning of the week sees the expansion of favorable conditions and moderate to heavy movements to many areas west of the Appalachians and Florida Peninsula, expanding to the greatest extent by Wednesday night when all but the Florida Peninsula experiences moderate to heavy movement. The remainder of the period sees most moderate to heavy flights again restricted primarily to the west of the Mississippi River. Species on the move this week will include for those of you lucky enough to go on pelagic trips Sooty Shearwater, Cory’s Shearwater, Great Shearwater, Wilson’s Storm-Petrel, Band-rumped Storm-Petrel, Audubon’s Shearwater, Leach’s Storm-Petrel, Black-capped Petrel, Long-tailed Jaeger, Pomarine Jaeger, and for you land-lubbers Spotted Sandpiper, Least Sandpiper, Least Flycatcher, Philadelphia Vireo, Swainson’s Thrush, Northern Waterthrush, Tennessee Warbler, Nashville Warbler, American Redstart, Magnolia Warbler, Blackburnian Warbler, Yellow Warbler, Chestnut-sided Warbler, Blackpoll Warbler, and Wilson’s Warbler.