Forecast and Analysis

Regional Migration Analysis: 14-20 September 2013

Andrew Farnsworth The Cornell Lab Sep 20, 2013

Continental Summary

As the East pulsed with a major frontal passage and moderate to heavy movements in its wake, the West continued previous weeks’ pattern of many moderate movements. Birds on the move this week included Broad-winged Hawk, Northern Flicker, Warbling Vireo, Northern Parula, Palm Warbler,  Common Yellowthroat, and Lincoln’s Sparrow.


Moderate movements in the Pacific Northwest and portions of the Desert Southwest began the period, among more scattered light to moderate movements in the remainder of the region free of precipitation. A similar pattern continued through forecast period in many areas, with widespread light to moderate movements being the norm. Of note, precipitation shut down migrants in the Pacific Northwest on Sunday night, and continued to impact movements in portions of the northern Rockies for the remainder of the period. Additionally, after most of the precipitation departed from the eastern front of the Rockies, numerous moderate movements occurred in portions of Colorado and New Mexico through the end of the period. Birds on the move this week included Northern Pintail, Gadwall, Eared Grebe, White-faced Ibis, Red-necked Phalarope, Vaux’s Swift, Western Wood-Pewee, Lincoln’s Sparrow, and Black-headed Grosbeak. Additionally, an honorary bird on the move this week: a special highlight is in order for Blue-footed Booby, appearing in many locations off the California coast.

Great Plains

Light movements in the northern Plains stood in stark contrast to the heavy flights in the southern Plains to begin the forecast period. However, changeable conditions, including some precipitation, kept movements mostly local and light to moderate for the days that followed. However, a frontal boundary with some strong passing storms cleared the air and spawned moderate to locally heavy movements on Wednesday night in the Dakotas; by Thursday night this frontal boundary had pushed East through most of the region, facilitating moderate to heavy movements in many areas, even locally very heavy movements areas of the southern Plains, as cooler temperatures and northerly winds overspread much of the region. Birds on the move this week included Double-crested Cormorant, Great Blue Heron, Osprey, Broad-winged Hawk, Franklin’s Gull, Blue Jay, Yellow-rumped Warbler, and Swamp, Lincoln’s, White-crowned and Harris’s Sparrows.

Upper Midwest and Northeast

Moderate to heavy movements in the Midwest spread East to the Atlantic to begin the weekend, with some locally very heavy movements close to the immediate coast. The movements East of the Appalachians continued on Saturday night, becoming strictly coastal movements by Sunday night, as the rest of the region calmed to primarily light movements. A new frontal boundary crossed the Great Lakes by Sunday night, spawning moderate to heavy flights farther West and keeping most birds East of the Appalachians on the ground. With frontal passage complete by Monday night, widespread moderate movements were apparent across much of the region East of the Mississippi River. However, in the wake of this system, return flow brought about greatly diminished movements through the end of the period, with only scattered light to moderate movements occurring, and those localized primarily to northern New England to end the period. Birds on the move this week included Broad-winged Hawk, Northern Flicker, Ruby-crowned Kinglet, Common Yellowthroat, Northern Parula, Yellow-rumped and Black-throated Blue Warblers, and Lincoln’s, Swamp, and White-throated Sparrows.

Gulf Coast and Southeast

A widespread pulse of moderate to heavy movements occurred across the region on Friday night with the passage of a substantial front to the North. The effects of this passage were still apparent on Saturday night, though muted. Light to moderate movements were the norm following this pulse, primarily North and East of the Mississippi River Delta and away from the immediate coast. Despite the appearances on radar, some locations experienced much heavier insect and local bat movement than bird movement during this period, as marginal conditions were made unfavorable by the presence of locally intense thunderstorms and primarily insects and bats took flight. By the end of the period, mostly light movements were the norm, as generally unfavorable conditions overspread the region. Birds on the move this week included Eastern Wood-Pewee, Swainson’s Thrush and Veery, Gray Catbird, Ovenbird, American Redstart, Nashville, Tennessee, Black-and-white, Cape May, Palm, Magnolia, and Black-throated Blue Warblers, and Rose-breasted Grosbeak.