Forecast and Analysis

Regional Migration Analysis: 7-13 September 2013

Andrew Farnsworth The Cornell Lab Sep 13, 2013

Continental Summary:

Moderate movements took hold in many areas of the West, while a strong front produced excellent end of the period flights in the East after a pervasive summer-like air mass departed. Birds on the move included Barn Swallow, Ruby-crowned Kinglet, Swainson’s Thrush, Palm Warbler, Baltimore Oriole, and Lincoln’s and White-crowned Sparrows.



Light to moderate movements were widespread to begin the period, with the exception of the Pacific Northwest and some areas of the northern Rockies. These movements continued across the region this week, but numerous areas experienced more moderate movements than in any previous week so far this forecast season. In particular, portions of the Pacific Northwest experienced moderate movements to end the weekend and begin the week, and some of these even included locally heavy movements. Additionally, early week movements of moderate scale occurred in the northern Rockies and Montana as high pressure built into the area. California also experienced similar movements; and after a bout of scattered precipitation in the Desert Southwest, more extensive moderate movements occurred in this area as well by Wednesday evening. Birds on the move included American Wigeon, Vaux’s Swift, Western Wood-Pewee, Ruby-crowned Kinglet, American Pipit, Yellow Warbler, and White-crowned and Lincoln’s Sparrows.

Great Plains

A light to moderate pulse of movements began the weekend, but a disturbance moving into the region quick shut down migrants to begin the week. As this disturbance passed, more extensive light to moderate movements followed, first in more northerly portions of the region on Monday night and gradually farther south. Parts of the central and southern Plains, however, experienced persistent precipitation, building along the frontal boundary, which shut movements down for a large part of the week; however, by the end of the forecast period, as the slate for most of the region cleared with high pressure moving through the region, some areas of the southern Plains finally saw local moderate to heavy movements behind the frontal boundary. Birds on the move included Ruddy Duck, Ruby-crowned Kinglet, Swainson’s Thrush, American Redstart, Tennessee, Orange-crowned, and Palm Warblers, and Clay-colored and White-throated Sparrows.

Upper Midwest and Northeast

A large coastal movement with extensive moderate intensities began the forecast period, with scattered moderate movements around the remainder of the region. This pattern quickly gave way to greatly diminished movements through the weekend, as unfavorable conditions prevailed. However, this pattern of a rapid pulse of light to moderate movements appeared again, with the next pulse of light to moderate movements in the western Great Lakes on Saturday night quickly shifting to the Atlantic Coast for Sunday night. Most of the region experienced muted migration on Monday and Tuesday nights, as a warm and unstable air mass set up shop over the region; but the change to come was already beginning in the northwestern reaches of the region, behind the passing cold front, with moderate to locally heavy movements behind intense precipitation. This pattern intensified on Wednesday night, with many areas West of the Appalachians experiencing moderate movements and some areas of the southern Great Lakes experiencing heavy movements. One set of unexpected movements occurred on Wednesday night from New Jersey and eastern Pennsylvania North and East to eastern Massachusetts, most visible on the immediate coast of Connecticut. Although BirdCast forecast minimal to light movement on this night, observed movements on radar were light to moderate in these areas, the result of a passing gust front and different than expected weather conditions after sunset. Observers at the Tribute in Light had the good fortune of seeing this nocturnal movement evolve. Flight calling at this event, as birds were attracted and confused by the lights, was intense at times, in addition to the great visuals afforded by bright beams pointed skyward. A more expected set of movements occurred to end the forecast period, as a cold front finally passed through most of the region, spawning moderate and locally heavy movements, particularly in the central Mississippi River valley and portions of the Ohio River valleys, some of which were quite nicely audible by ear. Benjamin Van Doren filed this cool report.  Most of the immediate coast, however, was left waiting to the weekend to join the migration madness. Birds on the move included Hudsonian Godwit, Dunlin, Northern Flicker, Great Crested Flycatcher, Gray-cheeked and Swainson’s Thrushes, American Redstart, Ovenbird, Black-throated Blue, Black-throated Green and Palm Warblers, and Baltimore Oriole.

Gulf Coast and Southeast

Widespread light to moderate movements began the period, but unfavorable and generally summer-like conditions muted the movements thereafter through much of the region for much of the remainder of the forecast period. By Wednesday night slightly more extensive and intense movements were occurring, with locally moderate migration in portions of coastal Texas, the central Mississippi River valley, and scattered areas of the Southeast. As the front approached with changes in the air (literally), widespread light to locally moderate movements began, and the some northern areas saw the first moderate and heavy movements in many days. Birds on the move included Black Tern, Common Nighthawk, Eastern Kingbird, Swainson’s Thrush and Veery, Barn Swallow, and Bay-breasted, Tennessee, Hooded, and Black-and-white Warblers.