Forecast and Analysis

Migration Forecast: 13 – 19 April 2012

Andrew Farnsworth The Cornell Lab Apr 13, 2012

Expect the best migration so far this year for at least portions of this week throughout North America. Many areas of the country will see fallout potential this week for passerines and waterbirds. The Desert Southwest and scattered areas of the West should see at least light to moderate movements, and the potential for precipitation means birders should keep a watchful eye on migrant traps. The Great Plains should see an infusion of migrants early in the period before a front passes through the region. Birders in the Upper Midwest and Northeast should finally have a respite from the lackluster migration of the last several weeks, with moderate migration more widespread with the southwesterly flow. The Gulf Coast and Southeast should watch the passage of the low pressure system moving eastward across the country. It may spawn fallout conditions in numerous states from early in the week through to almost the end of the forecast period.See below for radar imagery showing a strong arrival of birds on the Texas Coast late of Friday.

Daily forecast maps are available here.

Shorebirds will be on the move this week. Watch for Upland Sandpipers on sod farms, fields and grassy hilltops.

Shorebirds will be on the move this week. Watch for Upland Sandpipers on sod farms, fields and grassy hilltops.

Upland Sandpiper

Expect a strong surge of shorebirds to push northward this week. Among these will be Upland Sandpiper, which is a long -distance migrant that winters in southern South America. Individuals should return to breeding grounds in much of the southern and central Great Plains as well as locally in the Midwest, Mid-Atlantic and Northeast. Within the last week there have been scattered individuals seen as far north as Roberts County, SDOzaukee Co., WI and Westchester County, NY (embedded photos in checklist); there are a few scattered reports from the Southeast. The biggest influx has been along the Gulf Coast, central Texas and northward into Kansas and Missouri. Even with rather sparse observer coverage there have been sightings from El Jocote, Honduras and several from La Ventosa, Mexico including 15 on this checklist.

Expect good numbers to push through central Texas and the southern Great Plains all week. We are a bit surprised that eBird has no reports of Upland Sandpiper in North Dakota anytime in April. Given the strong southerly flow into the Dakotas, this would be the April to find them there, perhaps even into the Prairie Provinces. As were the birds in Honduras and New York, Upland Sandpipers are often first detected by their bubbling calls. Be sure to also listen for them flying over at night. During the day, check sod farms and fields. Migrants often stop and rest on grassy hilltops, so be sure to check relatively high areas, particularly during inclement weather.

The below text suggests a lot of possibility for fallout conditions; be sure to read last week’s BirdCast Analysis for a review of what a fallout is and what to watch for to try to witness one!

Light to moderate migration is likely across the Desert Southwest and portions of the Four Corners and Great Basin region at the front end of the forecast period, although scattered precipitation may shut down movements where it occurs. Conditions will change through the weekend, though, as unfavorable winds and widely scattered precipitation will keep many birds grounded, there is potential for fallout in desert oases of southern California — check migrants traps carefully this weekend. Much of the week looks to be unfavorable for anything more than widely scattered light movements, because of precipitation and unseasonable winds throughout the region. Portions of the Southwest may see light to moderate movements by the week’s end, and light movements may occur locally in the Great Basin and Pacific Northwest depending on the extent of precipitation. Birders in the latter region should carefully watch the interaction of forecast southerly winds and precipitation in order to determine where and when to visit passerine migrant traps at week’s end.

Great Plains
Moderate to heavy migration should occur through the weekend over southern and central portions of the Great Plains, and birders should watch with interest where the favorable winds meet precipitation – fallouts and concentrations of migrants are possible from Missouri north and west to the Canadian border.  A change occurs early in the week with a passing frontal boundary and northerly flow that will likely shut down migration in the region, northern portions of the region may be far enough removed from the passage of that system to experience calm winds and light to moderate movements to begin the week. The Great Plains will be subject to changeable, light and variable winds through the middle of the week, which may allow for local light-to-moderate movements. By week’s end, southern and eastern portions of the region should again see moderate migration. Birders should be aware that forecast precipitation to the end of the week may interact with areas of light to moderate migration in the central and northern portions of the region; the potential of passerine and waterbird fallouts should be part of late-week planning.

Upper Midwest and Northeast

As we write, this region continues to experience the duality typical of many recent weeks, in which the Upper Midwest sees favorable conditions for light to moderate migration and the Northeast sees unfavorable conditions except very for some highly local light movements. However, these unfavorable conditions will finally collapse as the weekend begins, with many areas of the region experiencing favorable conditions for more widespread light to moderate movements (with some locally heavy movements), including favorable winds combined with the threat of precipitation. Birders in many areas of the Ohio River valley, eastern Great Lakes, and northern New York should watch for fallout conditions this weekend, whereas birders in coastal areas of the Northeast should watch coastal migrant traps for passerines. Sunday and Monday are likely to be especially good days for birding, and the pent-up migratory restlessness of early April landbirds is likely to result in a major changeover in the avifauna after this weekend. Watch, in particular, for herons,  Broad-winged Hawks, Chimney Swifts, Blue-headed Vireos, swallows, Blue-gray Gnatcatchers, Hermit Thrushes, and kinglets, . Also in the offing should be a mix of warblers, including early species (e.g., Louisiana Waterthrush and Palm, Pine, and Yellow-throated warblers) and not-quite-so-early species (e.g, Black-and-white, Prothonotary, Yellow, and Black-throated Green warblers). This pattern should continue into the beginning of the week, and the threat of precipitation may expand into the northern portion of the region where birders should watch for potential fallout conditions. As low pressure moves into the region, potential exists for fallouts in the western Great Lakes and Ohio River Valley, north and east through the Adirondacks. After the frontal passage, midweek should be much less active, with forecast northerly winds inhibiting any significant movements. Although conditions never fully return to ideal through the end of the week, western portions of the region should see slightly more widespread light movements occur, while the Northeast sees unfavorable northerly flow to end the period.  The end of the week may see more potential for waterbird fallouts in the western and central Great Lakes, so birders should watch the distribution of precipitation.

Gulf Coast and Southeast

Texas is back on the trans-Gulf migration train to kick off the weekend, with arrivals likely across many coastal areas in highly favorable conditions (see radar imagery for Friday, 13 April below!). Moderate movements should be the norm, with scattered heavy migration in southern and central Texas. Conditions farther to the east are less favorable,  with Florida and the Atlantic coastal plain receiving only locally light to moderate movements, depending on the extent of easterly flow associated with a high pressure center over the Outer Banks. The weekend sees the favorable conditions expand across a wide area, from Texas to Florida and the Atlantic coast. Trans-Gulf flights should arrive quickly in favorable southerly winds during the day on the Texas and Louisiana coasts, but concentration is unlikely, given the lack of precipitation. Birders should watch the approach of a frontal boundary early in the week, however, as it is forecast to cross into the Gulf of Mexico. If this occurs, conditions would be good for fallouts in Texas and Louisiana early in the week. Some fallouts in the western portions of the region may even contain more eastern, Caribbean-wintering species, depending on the extent of easterly flow across the Gulf of Mexico. Through the middle of the week, interesting fallout potential exists in more-eastern portions of the Gulf; birders should be ready to visit coastal spots.

As high pressure builds into the western portion of the region behind this frontal passage, midweek likely will see moderate movements of circum-Gulf migration in Texas despite northerly or light winds. By Thursday, Florida and the coastal Southeast should see fallout potential as the front (with its associated precipitation) moves into this part of the region. By late week, conditions begin to improve for more widespread moderate and locally heavy movements in Texas, whereas conditions will likely not be favorable for movements in the eastern portions of the region. The current forecast suggests that not until the weekend will trans-Gulf movements begin to recur in the farthest western reaches of the Gulf.  Note, during this forecast period, particularly toward the end of the week, portions of the Southeast may see more extensive light-to-moderate movements if winds are calmer and less northerly than forecast.

radar2 radar1

If you live in the area and get can get out to the Texas Coast, you may want to do it Friday evening or Saturday morning!  South-southeast winds are producing a strong arrival of migrants reaching the western Gulf Coast Friday afternoon. These are birds that likely departed the Yucatan Peninsula last night and have spent most of the night and day crossing the Gulf. If you are on the Gulf Coast, the conditions aren’t great for any kind of “fallout”, but at least some of the birds are sure to stop off in coastal migrant traps. In fact, we just spoke with Luke Seitz (one of our eBird reviewers for Maine), who is “on the scene” at High Island and says they are watching birds arrive now. Most seem to be Orchard and Baltimore Orioles, Rose-breasted Grosbeaks, Blue Grosbeaks, and other large, strong-flying birds. Usually the arrival of species like this precede the arrival of warblers, so this is a great sign that there will be a good arrival of those species too. The images below show the comparison of 10:29am (top)and 3:07pm local time (bottom). Many thanks for the heads-up on this movement to David LaPuma, an avid eBirder and radar watcher who runs the superb radar-watching website

Posted 13 April 2012 by Andrew Farnsworth, Christopher Wood, Marshall Iliff, and Brian Sullivan of the Cornell Lab of Ornithology and David Nicosia of NOAA, on behalf of Team eBird and BirdCast. Special thanks to Tony Leukering for helpful comments.