Forecast and Analysis

Regional Migration Analysis: 26 April – 3 May 2013

Andrew Farnsworth The Cornell Lab May 03, 2013

Continental Summary:

Light to moderate movements were widespread in the West, while the movements in the East continued to run the gamut from nonexistent to heavy in a wide range of weather conditions. Birds on the move this week included Warbling Vireo, House Wren, Gray Catbird, Yellow Warbler, and Baltimore Oriole.



Light to moderate movements were widespread across the region this week, particularly in California and the Desert Southwest. Other than some locally scattered precipitation, primarily in the Pacific Northwest and northern Rockies, conditions were generally favorable for birds to migrate. This was particularly true early in the forecast period, on Friday, Saturday and Sunday nights. Birds on the move this week included Red-necked Phalarope, Brown-crested and Olive-sided Flycatchers, Western Wood-Pewee, Swainson’s Thrush, and Western Tanager.

Great Plains

The period began with moderate to heavy movements in the border states, diminishing farther south to primarily light to locally moderate movements. By Sunday night moderate to heavy movements were more apparent farther south, as favorable conditions ahead of an advancing cold front facilitated migrant exodus. These conditions persisted through Monday, but, with the exception of the southern Plains states, precipitation and building high pressure over central Canada shut down most movements by Tuesday night. As high pressure dropped South and moved East into the region and brought cooler temperatures, wintry precipitation (!), and more northerly flow, most migrants stayed on the ground, with only scattered light to moderate movements, punctuated by isolated heavy movements, to end the forecast period. Birds on the move this week included Mississippi Kite, Great Crested Flycatcher, Warbling Vireo, Swainson’s Thrush, Brown Thrasher, Yellow Warbler, Rose-breasted Grosbeak, and Baltimore Oriole.

Upper Midwest and Northeast

High pressure over the northern Appalachians kept most birds grounded to begin the period, with the exception of light movements in the Ohio and Mississippi River valleys and locally moderate to heavy movements in the western Great Lakes. Conditions improved slightly on Saturday night, with more migrants taking flight in more areas including moderate to heavy coastal movements. However, this was short-lived as a disturbance with scattered precipitation shut down most movements to end the weekend. The Northeast continued to experience generally unfavorable conditions through the remainder of the period, with primarily scattered light movements being the norm. The Midwest experienced a very different set of conditions, with moderate to heavy movements occurring early in the week and continuing, though diminished by the increasing presence of rain and an approaching complex frontal boundary, through the end of the period. Birds on the move this week included Great Crested Flycatcher, Warbling Vireo, House Wren, Wood Thrush, Gray Catbird, Yellow Warbler, and Baltimore and Orchard Orioles.

Gulf Coast and Southeast

Friday night saw a large exodus of birds from the Texas coastal plain in the first reasonably favorable conditions for lift off in a number of days. Light to moderate movements began the weekend across the remainder of the Southeast. This pattern continued across the region over the course of the week, but it was punctuated by periods of intense storms that grounded birds where precipitation fell. This was particularly true in Texas, but also farther East as the week progressed, including fallouts as far East as the Florida Panhandle. This pattern was largely a result of a rather unstable atmosphere and the lack of an organized frontal boundary to clarify the differences between air masses. By Wednesday night, however, a cold front moving across Texas spawned a moderate to heavy coastal flight while shutting down movements in its wake, as the rest of the region saw only local movements because of scattered precipitation. Some areas of the eastern Gulf Coast did get fallouts, though, as birds departing from northern Central America hit precipitation over the Gulf and calm winds closer to shore. The front cleared the decks, so to speak, as it passed into the Gulf of Mexico and shut down the Texas movements, as continued unstable atmosphere limited movements farther East to localized light to moderate levels. Note that several areas of the western Gulf Coast, including a number of inland locations, experienced fallouts with this system’s passage. Birds on the move this week included Philadelphia Vireo, Gray-cheeked Thrush and Veery, Magnolia, Bay-breasted, and Chestnut-sided Warblers, Dickcissel, and Bobolink.