Yellow-billed Cuckoo. JamEs ParRis/Macaulay Library. 25 May 2016. eBird S29911144

Continental Summary

As the peak of migration in most areas recedes with another spring season passing, portions of the West experience light to moderate flights featuring White-throated Swift, Western Wood-Pewee, Warbling Vireo, Swanson’s Thrush, Cedar Waxwing, and Gray Catbird primarily mid and late period and patchily distributed moderate to heavy flights featuring Yellow-billed Cuckoo, Eastern Kingbird, Eastern Wood-Pewee, Cedar Waxwing, Orchard Oriole, and Bobolink occur in the East against a backdrop of a dynamic weather scene.

Arrows show wind speed and direction (arrow points in the direction to which wind is blowing) 100 m above ground level. Areas with southerly winds are colored red; northerly winds colored blue. Accumulated precipitation (in 6 hour intervals) is green, outlined by white. Broadly speaking, areas of the map in red will experience conditions that are favorable for migration, and areas where red and green (and red and blue) intersect and overlap may experience migrant concentrations and fallouts as migrants interact with precipitation.

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Quick Links to Regions

Upper Midwest and Northeast	Gulf Coast and Southeast
Great Plains	West

Upper Midwest and Northeast

A patchwork of scattered precipitation and favorable conditions sets the stage for a varied weekend of migration to start the period. Areas free of precipitation will see birds take advantage of favorable winds and warm temperatures in moderate to locally very heavy flights. By Monday, with the passage of low pressure to the east, less favorable conditions arrive in much of the region. These conditions persist for several days, when migration will be light. Note, however, that patches of more favorable conditions are forecast, and in these areas migration intensities will be locally higher. The end of the period sees the northern and eastern reaches of the region return to more favorable conditions, and moderate to locally very heavy flights will occur. Note that some of the unsettled weather earlier in the work week relates to the evolution and path of Invest 91L off the southeast coast. The fate of this system will have ramifications farther north in this region, both from a perspective of blocking remaining migrants from taking flight and potentially from a perspective of entraining vagrants and depositing them in the region.

Cedar Waxwing. Ken Janes/Macaulay Library. 25 May 2016. eBird S29909813

Species on the Move

Beginning Arrivals What is this?

Peaking Arrivals

Beginning Departures

Ending Departures

Gulf Coast and Southeast

A generally favorable start to the weekend will see the last big pulses of moderate to heavy flights commence for this spring across much of the region. However, the effects of a developing low pressure system off the southeastern US continues the soggy recent history for portions of the southeast, so too shutting down flights as precipitation arrives. For the first half of the work week, the region is divided approximately by the Mississippi River, with favorable conditions to the west seeing continued moderate to locally heavy flights and much less favorable conditions to the east seeing generally much lower migration intensities. By the end of the work week, unsettled conditions expand to more areas of the region, and migration will be much less evident. This is a function of the late date in spring, with most of the migrant pulse long past, and the unfavorable conditions.

Acadian Flycatcher. Kris Petersen/Macaulay Library. 17 May 2016. eBird S29748049

Beginning Arrivals What is this?

Peaking Arrivals

Beginning Departures

Ending Departures

Great Plains

A variable weather scene during the first half of the period will see similarly varied migration intensities and extents. For the most parts, conditions will not be favorable for more than local movements. In areas where precipitation does not fall, moderate to isolated very heavy flights will occur. Elsewhere, movements will be sparse. The second half of the period sees even more localized favorable migration conditions, and similarly reduced extents and intensities of flights.

Long-billed Curlew. Alex Hughes/Macaulay Library. 14 May 2016. eBird S29664351

Species on the Move

Beginning Arrivals What is this?

Peaking Arrivals

Beginning Departures

Ending Departures

West

Locally light to moderate flights will occur from portions of the Desert Southwest north through the Rockies and Great Basin to begin the period, as long as scattered precipitation does not keep birds grounded. Early work week flights will be even more localized, as more widespread unfavorable flow prevails. But by Thursday and Friday, slightly more favorable conditions return, again scattered across the region, bringing the last of the light to moderate flights for the spring to the montane and intermontane west as well as to portions of the Pacific Northwest.

Warbling Vireo. Thomas Hinnebusch/Macaulay Library. 9 May 2016. eBird S29519221

Species on the Move

Beginning Arrivals What is this?

Peaking Arrivals

Beginning Departures

Ending Departures

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Farnsworth and Van Doren