Pulses of movements will track the advance of several low pressure systems across the continent this week, with those system producing light to moderate movements in the West and moderate to heavy movements in the East. Species on the move this week will include Spotted Sandpiper, Wilson’s Phalarope, Great Crested Flycatcher, Warbling and Red-eyed Vireos, House Wren, Swainson’s and Wood Thrushes, Brown Creeper, Orange-crowned, Nashville, Yellow, Black-and-white, and Blue-winged Warblers, and Orchard and Baltimore Orioles.
Arrows show wind speed and direction 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.
A patchwork of conditions across the West begins the period, with light to moderate movements occurring from the Desert Southwest north and east through the southern and central Rockies and scattered light movements elsewhere across the region. Birders in the central and northern Rockies as well as portions of the Desert Southwest should watch the distribution of precipitation, as some of these locations may see weather-related concentrations in local stopover habitats. Over the course of the weekend, areas with light and moderate movements become increasingly more widespread, but by Monday night much of the West experiences light to moderate movements again. A low pressure system moves east into the Great Basin and portions of the northern Rockies by Tuesday, shutting down most movements in those areas. But to the east and south of this system, highly favorable conditions will spawn moderate movements, with some locally heavy, in many portions of the Desert Southwest through the eastern front of the Rockies. The pattern continues in the Desert Southwest, in particular, through Wednesday night, though low pressure’s passage and arriving unfavorable conditions generally shut down most movements by Thursday night. The week ends with another pulse of favorable conditions spreading across the region, with many areas again experiencing light to moderate movements by Friday night. Species on the move this week will include Semipalmated Plover, Spotted Sandpiper, Wilson’s Phalarope, Vaux’s Swift, Olive-sided Flycatcher, Western Wood-Pewee, Warbling Vireo, Swainson’s Thrush, Ruby-crowned Kinglet, Hermit Warbler, Yellow-breasted Chat, Western and Summer Tanagers, Lazuli Bunting, Black-headed Grosbeak, and Fox, Golden-crowned, White-crowned, and Lincoln’s Sparrows.
Mostly favorable conditions prevail across the Plains for the weekend, facilitating moderate to heavy movements in many areas. Note that some pockets of unfavorable conditions may dampen movements in some areas. Furthermore, birders should watch the passage of low pressure through the region, as migrants will likely encounter precipitation and may fall out in some central and southern locales. The region quiets briefly as unfavorable conditions follow the frontal passage, but this situation is short-lived as another pulse of southerly flow fills in rapidly. Tuesday night will see a return to moderate and heavy movements in many areas. The pattern from earlier in the week repeats itself, with favorable conditions and continued moderate to heavy movements giving way to migration shut downs and potential for fallouts and concentrations by Thursday night as low pressure passes. The region is mostly quiet, with scattered light and locally moderate movements next Friday night. Species on the move this week will include Willet, Spotted Sandpiper, Wilson’s Phalarope, Chimney Swift, Eastern and Western Kingbirds, Great Crested Flycatcher, Warbling Vireo, House and Winer Wrens, Swainson’s Thrush, Brown Creeper, Orange-crowned and Nashville Warblers, Baltimore Oriole, Indigo Bunting, Clay-colored, Henslow’s and Fox Sparrows, and Dark-eyed Junco.
Upper Midwest and Northeast
Aside from marginal and locally favorable conditions in the northern Appalachians through New England, where moderate movements will occur, most of the region is quiet to begin the weekend. However, conditions improve over the course of the weekend, with favorable conditions spawning moderate flights by Saturday night and locally heavy flights by Sunday and Monday nights. The next low pressure system shuts down movements across most of the region by Tuesday night, but birders along the immediate Atlantic Coast should watch closely as precipitation meets migrants early in the evening’s migration. After the storm system passes, Wednesday night is mostly quiet away from the westernmost reaches of the region. But favorable conditions build back into the region to end the week, with moderate to heavy movements first in the Mississippi and Ohio River valleys then farther east by next Friday night. Species on the move this week will include Green-winged Teal, Bufflehead, Common Merganser, Horned Grebe, Bonaparte’s Gull, Yellow-bellied Sapsucker, Great Crested Flycatcher, Eastern Kingbird, Red-eyed and Warbling Vireos, Wood Thrush, House Wren, Brown Creeper, Gray Catbird, Blue-winged, Yellow and Black-and-white Warblers, Northern Waterthrush, Ovenbird, Common Yellowthroat, Orchard and Baltimore Orioles, Fox Sparrow, and Dark-eyed Junco.
Gulf Coast and Southeast
As low pressure spins east across the Florida Peninsula, most of the region (including the entirety of the trans-Gulf migration system) will feel the unfavorable effects of its passage to begin the weekend. Only the southernmost reaches of Florida may see scattered and short-lived movements on Friday night. Note, also, that some moderate movements will be apparent farther west in Texas. As the storms depart, moderate to heavy movements return to begin the week, but only west of the Mississippi River where favorable conditions have returned. These movements spread east on Monday night, but another approaching frontal boundary brings changes by Tuesday. Given the lack of trans-Gulf flights, because of unfavorable conditions, precipitation forecast for Tuesday may generate only circum-Gulf migrant concentrations and local fallouts where it falls. By Wednesday night, more favorable conditions return, again west of the Mississippi, bringing moderate to heavy movements back to much of Texas. Conditions further improve across almost the entire region by Thursday night, spreading far into the Gulf of Mexico and into northern Central America; this will facilitate moderate to heavy flights in many areas, and turn on the tap, so to speak, for the trans-Gulf migration system’s arrivals on Friday. Species on the move this week will include Green-winged Teal, Northern Harrier, Belted Kingfisher, Eastern Wood-Pewee, Gray-cheeked and Swainson’s Thrushes, Veery, Magnolia, Blackpoll, Chestnut-sided Warbler, Yellow, Bay-breasted, and Black-throated Blue Warblers, Dickcissel, Bobolink, Baltimore Oriole, Rose-breasted Grosbeak, Painted Bunting, and Swamp and White-throated Sparrows.