A busy early week of movements in the West shuts down by week’s end, while widespread favorable conditions arrive by mid to late week in the East and spawn moderate to heavy movements in many areas. Species on the move this week will include Swainson’s Thrush, Least Flycatcher, Yellow Warbler, Magnolia Warbler, American Redstart, Baltimore Oriole, Yellow-billed Cuckoo, White-throated Sparrow, Ruby-crowned Kinglet, and Dark-eyed Junco.
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 overspread much of the West over the weekend, and southerly flow will facilitate light to moderate movements in many areas. Scattered precipitation associated with a disturbance moving through the Pacific Northwest may bring potential for concentration and fallouts from there through the northern Rockies. As this system moves through the region, unfavorable conditions associated with it shut down many movements in more northerly areas, while the southern portion of the region continues to see widespread light to moderate movements. By midweek, this system’s influence covers much of the region and shuts down most migration, with the exception of portions of the Desert Southwest, southeastern California, and the central Rockies. And by the end of the period, much of the region sees migration grind to a halt. Species on the move this week will include arriving Swainson’s Thrush, Yellow Warbler, Western Tanager, Western Wood-Pewee, Black-headed Grosbeak, Bullock’s Oriole, Spotted Sandpiper, Warbling Vireo, and MacGillivray’s Warbler. Departing species will include Least Sandpiper, Greater Yellowlegs, and Golden-crowned Sparrow.
A slow start to the weekend, with only light to moderate movements in the central Plains, will give way to increasingly active migration nights as the week continues. Favorable conditions will build into the region, becoming widespread and facilitating increasingly more extensive moderate to heavy movements by Tuesday night. As a disturbance moves slowly through the region, more northerly areas see movements diminish rapidly, eventually shutting down by Thursday night. More southern areas will continue to see moderate to heavy movements, and birders should watch where these movements interact with precipitation for potential fallouts and concentrations. By week’s end, much of the region sees only limited movements as scattered precipitation and unfavorable winds keeps most birds on the ground. Species on the move this week will include arriving Least Flycatcher, Yellow Warbler, Blackpoll Warbler, Gray Catbird, Orchard Oriole, Eastern Wood-Pewee, Wilson’s Warbler, American Redstart, Rose-breasted Grosbeak, Swainson’s Thrush, Black Tern, Tennessee Warbler, Baltimore Oriole, Ovenbird, Indigo Bunting, Red-headed Woodpecker, Clay-colored Sparrow, Gray-cheeked Thrush, and Common Yellowthroat. Departing species will include Pied-billed Grebe, Greater Yellowlegs, Franklin’s Gull, Bufflehead, Dark-eyed Junco, and Northern Shoveler.
Upper Midwest and Northeast
A patchwork of favorable conditions lead to a similar patchwork of moderate to locally heavy movements to begin the weekend. But this changes quickly as low pressure moves through the region and keeps most migrants grounded. The lingering effects of this low pressure remain and keep migration light until more widespread favorable conditions return by Wednesday night. Note that this includes coastal New England, suggesting the potential for an interesting interaction where favorable and unfavorable conditions meet. Birders along the New England coast should watch this interaction carefully, as it may lead to some unexpected concentrations. By Thursday, almost the entire region will experience favorable conditions for moderate to heavy movements, but the approach of a frontal boundary should make for an interesting weekend as favorable conditions facilitating these large movements will change rapidly as precipitation arrives. Species on the move this week (there are a lot!) will include Magnolia Warbler, American Redstart, Chestnut-sided Warbler, Baltimore Oriole, Blackpoll Warbler, Veery, Black-throated Blue Warbler, Cape May Warbler, Wilson’s Warbler, Scarlet Tanager, Rose-breasted Grosbeak, Bay-breasted Warbler, Least Flycatcher, Eastern Wood-Pewee, Common Yellowthroat, Indigo Bunting, Swainson’s Thrush, Blackburnian Warbler, Canada Warbler, Bobolink, Red-eyed Vireo, Gray Catbird, Great Crested Flycatcher, Tennessee Warbler, Ovenbird, Ruby-throated Hummingbird, Eastern Kingbird, Gray-cheeked Thrush, Least Sandpiper, Golden-winged Warbler, Wood Thrush, Acadian Flycatcher, Nashville Warbler, Yellow Warbler, Yellow-billed Cuckoo, Semipalmated Plover, Warbling Vireo, Common Tern, Black-throated Green Warbler, Common Nighthawk, Philadelphia Vireo, Northern Parula, Black-billed Cuckoo, Lincoln’s Sparrow, Black Tern, and White-crowned Sparrow. Departing species will include Dark-eyed Junco, Ruby-crowned Kinglet, Bufflehead, Hermit Thrush, White-throated Sparrow, Green-winged Teal, Blue-winged Teal, Rusty Blackbird, Wilson’s Snipe, Northern Shoveler, and Ring-necked Duck.
Gulf Coast and Southeast
With the departure of a frontal boundary to the east, building high pressure will bring increasingly favorable conditions for moderate and heavy movements to return by the end of the weekend. These conditions continue to improve through the early week, as these movements become more widespread. This pattern continues through the end of the week, although another approaching frontal boundary will ground migrants and create concentrations from Texas to the Mississippi River by the end of the period. Species on the move this week will include arriving Yellow-billed Cuckoo, Wilson’s Warbler, Canada Warbler, American Redstart, Magnolia Warbler, Eastern Wood-Pewee, Least Flycatcher, and White-rumped Sandpiper. Departing species will include White-throated Sparrow, Palm Warbler, Yellow-rumped Warbler, and Ruby-crowned Kinglet.