Forecast and Analysis

Regional Migration Analysis: 21-27 September 2013

Andrew Farnsworth The Cornell Lab Sep 27, 2013

Continental Summary:

Changeable conditions across the West spawned scattered and sometimes moderate movements in a patchwork across the region, as strong high pressure dominated the eastern US and spawned extensive and continuing moderate to heavy movements. Birds on the move this week included Eastern Phoebe, Blue-headed and Warbling Vireos, Ruby-crowned and Golden-crowned Kinglets, Wilson’s, Palm and Yellow-rumped Warblers, and Swamp, White-throated, and White-crowned Sparrows.


Although little movement was apparent in much of the Great Basin and northern Rockies, light to moderate movements were scattered from the Cascades South and East into the southern Rockies to begin the period. Some movements were even locally heavy in the most southeastern reaches of the forecast area. This pattern evolved over the weekend to see light to moderate movements expand in more areas, though such movements were still generally isolated and local and almost exclusively West of the Rockies, where precipitation shut down movements. As a disturbance responsible for this precipitation shifted East, more moderate and even locally heavy movements occurred along the eastern front, while the remainder of the region was sparse for movements. For the duration of the period, light to moderate movements continued to occur, albeit scattered around the region where precipitation was not falling. Some of these movements were higher density flights, particularly during midweek in the Pacific Northwest and portions of the Great Basin. Birds on the move this week included Greater White-fronted Goose, Rufous Hummingbird, Wilson’s and MacGillivray’s Warblers, Western Tanager, and Golden-crowned Sparrow. Additionally, Blue-footed Booby and Elegant Tern are deserving of a special highlight for a bird on the move given the continued invasion of the species into California.

Great Plains

A pulse of moderate to heavy movements kicked off the weekend in the eastern Plains from the Canadian border South to Oklahoma. The pulse was short-lived, as high pressure built in rapidly and equally rapidly diminished movements, and then low pressure followed to end the weekend. As this disturbance meandered across the Plains, light to moderate and locally heavy movements occurred in its wake in marginal to favorable conditions for flights. This pattern shifted to the East and South, and even intensified in terms of increased locally heavy movements, as the low continued to move over the Mississippi River. However, the strong ridge of high pressure over the Appalachians and Atlantic Coast generally kept a lid on most movements through Wednesday evening in many areas. As the next frontal boundary passed into the region on Thursday night, moderate to heavy flights appeared in the Dakotas and Nebraska, with minimal movements farther to the South and East. Birds on the move this week included Ring-necked Duck, American Wigeon, Snowy Egret, Franklin’s and Ring-billed Gulls, Pinyon Jay, Mountain Bluebird, Sedge and Marsh Wrens, and Yellow-rumped Warbler.

Upper Midwest and Northeast

Away from the western Great Lakes’ and Mississippi River valley’s heavy flights, and isolated moderate to heavy movements in northern New England, most of the region experienced scattered light to moderate movements to kick off the weekend. However, as a strong frontal boundary moved East across the Appalachians, these heavy movements spread East across the region, finally reaching the Atlantic Coast by Sunday night. As high pressure moved in and shifted toward the Appalachians, western portions of the region shut down. However, moderate to heavy movements continued East of the Appalachians, and they continued for the remainder of the week. These movements included numerous good morning flight and nocturnal calling events. The high-pressure ridge established itself over the eastern half of the country and facilitated large-scale movements of migrants in these favorable conditions. Note that the distribution of these flights was almost exclusively East of the Mississippi and Ohio River valleys. Birds on the move this week included Canada Goose, Northern Flicker, Eastern Phoebe, Blue-headed Vireo, Brown Creeper, Winter Wren, Ruby-crowned and Golden-crowned Kinglet, Eastern Bluebird, Yellow-rumped, Palm, Blackpoll, Black-throated Green, and Black-throated Blue Warblers, and Lincoln’s, Swamp, Song, White-throated and White-crowned Sparrows.

Gulf Coast and Southeast

The contrast between the heavy flights in northern and central Texas and the dearth of birds farther East was extreme to begin the period. This pattern changed dramatically on Saturday night with the passage of a frontal boundary, spawning moderate and heavy flights from central Texas East to the southern Appalachians. Where these movements met precipitation in the southern Appalachians and eastern Gulf Coast, fallouts occurred. These fallouts continued in a number of areas for a couple of days, as the frontal boundary died and became stationary. To the West and North of the stalled front, moderate to heavy movements continued; however, they became increasingly local by Monday night. Instabilities in the atmosphere continued to expand in the vicinity of this stalled front on Tuesday night, keeping most movements light and heavier movements isolated. Farther West, much heavier flights continued behind a Hill Country-to-Ozarks front. This front followed the same path as the last, stalling over the eastern Gulf Coast, and facilitating mostly moderate movements to its North. Finally, with strong high pressure to the North and the front passing through Florida, moderate to heavy movements made there way into the Southeast and peninsular Florida to end the period, as most of the region West of the Mississippi was quiet. Birds on the move this week included Green Heron, Peregrine Falcon, Ruby-crowned Kinglet, Swainson’s, Gray-cheeked, and Wood Thrushes, Gray Catbird, Tennessee, Magnolia, Palm, Blackburnian, and Black-throated Green Warblers, and Rose-breasted Grosbeak.