Widespread light to moderate movements early in the weekend are shut down by two consecutive disturbances in the West, while the arrival of these same disturbances in the East brings a patchwork of moderate to locally heavy movements to the latter portion of the week. Species on the move this week will include Spotted Sandpiper, Wilson’s Phalarope, Wilson’s Snipe, American Kestrel, Least, Acadian, and Great Crested Flycatchers, Warbling Vireo, a suite of warblers and sparrows, Western and Scarlet Tanagers, Black-headed and Rose-breasted Grosbeaks, and Baltimore and Orchard Orioles.
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.
A pair of substantial disturbances move into and through the region over the weekend, bringing favorable conditions for migration in advance of their passage and shutting down migrants in their wake. Light to moderate movements will be widespread from the Desert Southwest north and east into the central Rockies on Friday night. These movements will occur over more easterly locations by Saturday night, with some of the movements even locally heavy to the east of the Rockies. Some portions of the Pacific Northwest will also experience movement, although these will be mostly scattered light to moderate movements. As precipitation spreads over more of the region, and unfavorable conditions prevail, migration generally shuts down with the exception of pockets of movements in the Desert Southwest. Birders should watch the movement of precipitation through the region, as there is potential for it to concentrate migrants in stopover habitat and on inland bodies of water (particularly in the central Rockies). Early week sees unfavorable conditions persist, breaking finally on Wednesday when pockets of light to moderate movements will return to portions of the Desert Southwest, Central Valley, and Great Basin. This patchwork of favorable conditions continues through the end of the period, with scattered light to moderate movements likely where favorable conditions occur. Note that portions of the California coast may experience higher density movements by Friday night. Species on the move this week will include Spotted Sandpiper, Wilson’s Phalarope, Red-necked Phalarope, Olive-sided Flycatcher, Western Wood-Pewee, Warbling Vireo, Ruby-crowned Kinglet, Swainson’s and Varied Thrushes, Yellow, Hermit, and Wilson’s Warblers, Yellow-breasted Chat, Western Tanager, Black-headed Grosbeak, Lazuli Bunting, and Fox, Lincoln’s, White-crowned and Golden-crowned Sparrows.
Highly favorable conditions bring moderate to heavy flights across the region by Saturday night, although a substantial low pressure system will shut down some of these movements by Sunday night. Note that Sunday night may provide an interesting opportunity to search for concentrations and fallouts, as southerly flow facilitating movements overlaps with precipitation in many areas. By Monday and Tuesday nights, the frontal passage will have all but shut down movements with a possible exception of pockets of light movements in the central Plains. This shut down continues through the remainder of the period, as mostly unfavorable conditions prevail across the region. This will keep movements light and scattered, although lighter than expected winds may allow for higher densities of movements to occur, particularly later in the week. Species on the move this week will include Double-crested Cormorant, American White Pelican, Osprey, Northern Harrier, Greater Yellowlegs, Hudsonian Godwit, Wilson’s Snipe, Franklin’s Gull, American Kestrel, Least and Great Crested Flycatchers, Warbling Vireo, Swainson’s Thrush, Gray Catbird, Tennessee, Orange-crowned, Nashville, and Yellow Warblers, Clay-colored Sparrow, Rose-breasted Grosbeak, Indigo Bunting, Dickcissel, and Orchard and Baltimore Orioles.
Upper Midwest and Northeast
Low pressure spinning through the region kicks off the weekend and brings favorable conditions to its east, where moderate to locally heavy movements will occur over portions of southern New England, and unfavorable conditions to its west, where migration will be scattered and light. As this system passes through the region, it becomes disorganized by Saturday night and creates a patchwork of conditions. Southern portions of the region will experience moderate and even locally heavy movements, as will some coastal locations, but much of the Great Lakes area will see minimal if any movement. This pattern starts again on Sunday, and continues through the week, as a new system organizes and slowly moves into the region; it brings a similar patchwork of moderate and locally heavy movements first to the west and then to the east of the Appalachians. Species on the move this week will include Northern Shoveler, Green-winged Teal, Ring-necked Duck, Bufflehead, Ruddy Duck, Pied-billed Grebe, Wilson’s Snipe, American Kestrel, Least and Great Crested Flycatchers, Warbling Vireo, Wood Thrush, Gray Catbird, Ovenbird, Nashville, Yellow, Chestnut-sided, Black-throated Blue and Black-throated Green Warblers, White-crowned Sparrow, Scarlet Tanager, Rose-breasted Grosbeak, and Baltimore Oriole.
Gulf Coast and Southeast
Favorable conditions for moderate to heavy movements prevail in Texas and locally along the Gulf Coast through Florida to begin the weekend. Movements become much more widespread on Saturday night, with the exception of Florida and portions of Georgia. Sunday continues to see southerly flow across the region, facilitating many moderate to heavy movements; note, however, that precipitation is forecast in some areas, which may concentrate birds where they interact with it during overland nocturnal migration. Additionally note that some concentrations of birds may appear around these storms as they actively avoid them (Team BirdCast will highlight this in a future post if this happens). A similar pattern persists on Monday night, as this disturbance begins to get organized. By Tuesday night, the low pressure system sits over the Mississippi River valley, effectively bisecting the region into favorable conditions to its east (where moderate to heavy movements will continue) and unfavorable conditions to its west (where northerly flow will shut down movements). Note that late Tuesday and Wednesday morning brings the boundary between air masses associated with this low pressure to the Gulf Coast, and conditions will be favorable for fallouts to occur along the central and western coast of the Gulf of Mexico as trans-Gulf migrants come ashore. From Wednesday through the end of the period, the frontal boundary slows and stalls, keeping precipitation in place in many areas and creating a patchwork of favorable conditions and related moderate to locally heavy movements. The distribution and orientation of precipitation during these days is favorable for more easterly fallouts to occur, primarily including Caribbean system trans-Gulf migrants. Species on the move this week will include Mississippi Kite, White-rumped Sandpiper, Yellow-billed Cuckoo, Eastern Wood-Pewee, Acadian and Least Flycatchers, Ruby-crowned Kinglet, Mourning Warbler, American Redstart, Magnolia, Bay-breasted, Yellow, Chestnut-sided, Yellow-rumped, Palm, and Wilson’s Warblers, Dickcissel, Bobolink, and Swamp and White-throated Sparrows.