Forecast and Analysis

Regional Migration Analysis: 17-23 August 2013

Andrew Farnsworth The Cornell Lab Aug 23, 2013

Continental Summary

Light to moderate movements across the West were apparent on most nights of the period, as the East experienced a major pulse of moderate migration at the end of the week. Birds on the move this week included Green-winged and Blue-winged Teal, Red-eyed Vireo, Blue-gray Gnatcatcher, Black-and-white and Wilson’s Warblers, American Redstart, and Baltimore Oriole.


Light to moderate movements were the norm for this week across much of the region. Although scattered precipitation kept a lid on migration where and when it fell, these movements were particularly apparent over the more southerly reaches from the Central Valley East and South through the Desert Southwest and Four Corners. Over the Pacific Northwest and northern Rockies, migration was primarily minimal to light in most areas. Birds on the move this week included Green-winged Teal, Northern Shoveler, Marbled Godwit, Western Sandpiper, Red Knot, Black-throated Gray, Wilson’s and MacGillivray’s Warbler.

Great Plains

Widely scattered light movements began the period in the northern Plains, with slightly heavier and more extensive movements occurring farther South in the region in more favorable winds and skies. This pattern continued until the middle of the week, when a disturbance passing through the region reversed the pattern; light to moderate movements were apparent close to the Canadian border while minimal to light migration occurred over the southern Plains. As the disturbance moved East to end the period, the eastern edge of the Plains saw more extensive light to moderate movements, particularly eastern Nebraska and Kansas. Birds on the move this week included Blue-winged Teal, Green Heron Buff-breasted Sandpiper, Olive-sided and Least Flycatchers, Cliff and Bank Swallows, Blue-gray Gnatcatcher, Black-and-white, Tennessee, Canada, and Wilson’s Warblers.

Upper Midwest and Northeast

Light to moderate movements over the central Mississippi River valley were the most apparent and regular movements for the region for most of the early part of the week. Some scattered light and locally moderate movements also occurred North and East along the Appalachians into New York and New England. This pattern continued into the middle of the week. However, Wednesday night saw a change beginning, with a disturbance moving through the western Great Lakes spawning more widespread moderate movements as it passed and shutting down movements in advance of its passage. With this disturbance largely through the region by Thursday night, widespread moderate movements occurred from the western Great Lakes South and East through the central Mississippi River valley and locally East through New York and Delmarva. Birds on the move this week included Green Heron, Semipalmated Plover, Baird’s and Stilt Sandpipers, Wilson’s Phalarope, Common Nighthawk, Red-eyed Vireo, Blue-gray Gnatcatcher, Veery, Blue-winged, Black-and-white, Chestnut-sided, and Canada Warblers, Rose-breasted Grosbeak, Bobolink, and Baltimore Oriole.

Gulf Coast and Southeast

Although widespread precipitation in the coastal Southeast shut down migrants to begin the weekend, light to moderate movements from the southern Appalachians West through Texas proceeded in largely rain-free skies. This pattern continued through the weekend, although the heavier movements tracked more favorable clear skies and calm winds and began to shift East to begin the week. By midweek conditions were more marginal, with mostly light and locally moderate movements in many areas. However, Thursday night saw a return of more extensive moderate movements as a disturbance farther north moved East and opened the gates for migrants to take flight primarily East of the Mississippi. Birds on the move this week included Ruby-throated Hummingbird, Olive-sided, Alder, and Willow Flycatchers, Red-eyed Vireo, Purple Martin, Bank and Barn Swallows, Black-and-white, Yellow, Yellow-throated, and Hooded Warblers, and American Redstart.


Need a refresher on definitions of migration amounts and the regions? Please visit this post.