BirdCast Migration Forecast: 6 – 12 April 2012

by eBird on April 6, 2012

After an amazingly early start to spring migration across much of the eastern two-thirds of North America, we expect migration to return to a more typical schedule this week. Arrival dates should be only slightly ahead of average through the remainder of this week. The period will start with high pressure across much of the U.S.. This high will weaken as a storm system develops off the New England coast and tracks to southeastern Canada where it will take up residence through Wednesday. This slow moving system will combine with a large Canadian high pressure system and bring northerly winds across much of the eastern U.S through until late in the forecast period. The period will begin quiet on the West Coast until another storm hits Monday. This storm will track into the northern Plains by Friday. Southerly winds will develop ahead of it for the central U.S as high pressure covers the east Thursday and Friday. Generally unsettled weather conditions will prevail along the west coast much of the period after the weekend.

Daily forecast maps from NOAA with an overall summary are available here.

Virginia Rail

While many migrants are conspicuous and easy to find, Virginia Rails prefer to remain hidden in cattails and marsh grasses. This secretive species is often detected  only by ear. At this time of year Virginia Rails call frequently, which makes them somewhat easier to find. They vocalize most often in early morning, at dusk and at night. They often respond to other calling Virginia Rails, King Rails, and Soras, as well as loud crashing sounds (like clapping your hands). At times, individuals may be heard calling overhead as migrants, typically a tk’rrrrrrr. This species is already on the move with several early arrivals in the Northeast. During the next few weeks, listen for this species in marshes and wetlands almost throughout North America. Rails will become more common in the northern regions (and less common southward) as the month progresses. Listen for these and other rails on calm warm nights when they are most likely to vocalize.

West

To begin the weekend, generally clear conditions with light winds will likely facilitate light movements across the region. These conditions will likely continue into the early part of the week, though coastal areas may begin to see precipitation shutting down any movements locally. Areas to the east and southeast in the region may begin to see more moderate movements through the beginning of the week. By the middle of the week, more widespread precipitation along the coast will prevent most movement. Widespread light to moderate movements should occur from the Desert Southwest through the northern Rockies. Late week precipitation scattered across northern, central, and coastal portions of the region will keep birds on the ground where it occurs, though light winds in precipitation free areas could allow light migration. Conditions in the Desert Southwest should continue to be favorable for light to moderate movements in southerly and southwesterly winds.

  • This week would be a good time to find the first arriving Purple Martins in California. This species arrives much later in the West than they do in the East. The first few typically arrive in California about the time Eastern Purple Martins are appearing in the Great Lakes. Desert nesting birds typically aren’t expected in Arizona until the end of the month, and those in places like Colorado aren’t expected until well into May.
  • This is a good time to watch for passage of loons, particularly in portions of the Interior West where the birds are most often noted as a migrant. Unsettled conditions can be particularly favorable for depositing Common Loons in regions where they are rarely noted even as flyovers.
  • Expect moderately good movements of shorebirds this week. Long-billed Curlews will be moving through the Interior West in considerable numbers. As with loons, the largest numbers are often forced down by rain or snow (often the same storms that drop loons). Black-necked Stilt and American Avocet are likely north to Washington and British Columbia.
  • Expect the first Greater Pewees to return to southeastern Arizona this week with the great majority of the population returning by the end of the month.

Great Plains

Some widely scattered precipitation and northerly and westerly flow will probably shut down migration in most areas to begin the forecast period. As the week begins, conditions will not be particularly favorable for movements in many areas of the region, though light migration will likely occur in cool but light winds. Though scattered precipitation in some areas will keep birds on the ground by midweek, southerly flow along the Rockies in the western portion of the region may facilitate light to moderate movements by Wednesday and Thursday, including diurnal and nocturnal migrants. By Thursday more widespread movements should occur, with light to moderate movements over many areas, including some pockets of heavy migration in the southern and central portions. The end of the week sees the threat of precipitation, which will shut down movements in many areas; but southerly flow in some areas near precipitation could produce fallout conditions. Late week and early next weekend would be a good time to consider checking local migrants traps, particularly bodies of water and open areas which might hold migrant shorebirds.

  • A wide variety of shorebirds should be found in the region from Wilson’s Snipe, Baird’s Sandpiper and both yellowlegs in the north to a dozens or more species in n. Texas and Oklahoma. Wilson’s Phalaropes may be found as far north as Nebraska’s Rainwater Basin, and with luck maybe into the Dakotas.
  • Yellow-bellied Sapsucker should continue to slowly advance through northern portions of the Great Plains. While a very rare migrant, observers in westernmost portions of the Great Plains should watch for Red-naped Sapsucker.
  • Large flocks of migrant blackbirds have largely vacated the southern Great Plains. Yellow-headed Blackbirds should continue to arrive in many breeding locations this week. Given the continued northward march of Great-tailed Grackles, observers should watch for this species near the periphery of its range. Marshes and feed yards are good places to look.

Upper Midwest and Northeast

Clear skies and light southwesterly flow should facilitate light to moderate movements across the Great Lakes and Midwest to begin the weekend, whereas northerly flow in the Northeast will not be favorable for much movement. Much of the forecast period is likely to be dominated by scattered precipitation, continued cool temperatures and northerly flow, suggesting minimal movements. In areas with lighter than forecast wind, or less northerly wind direction, light to moderate movements could occur. Similar to last week, westerly components to winds in coastal areas should allow at least some new arrivals daily in areas without rain. The region does not see much change until late in the week, when more western portions of the region should see bona fide light to moderate movements before precipitation shuts down birds again on the weekend. Note, as forecast last week, birders in inland areas receiving precipitation should watch local bodies of water for waterfowl fallouts.

  • Unsettled conditions near the end of the week may result in another waterbird fallout from Maryland and West Virginia through Pennsylvania and New York. In addition to Long-tailed Duck, watch for Common Loon, Ruddy Ducks, scoters, and Horned Grebe. During inclement weather check lakes and other water bodies for birds that have been forced to land.
  • The first significant push of shorebirds should occur with Greater and Lesser Yellowlegs expected throughout as well as Dunlin and Pectoral Sandpiper.
  • While the first few Barn Swallows have been seen throughout much of the region, expect the species to become much more widespread by the end of the week. Purple Martins should also arrive throughout most of the region.
  • The first Blue-headed Vireos should appear across much of the Northeast and Upper Midwest, but will not become common for another week or so. Also watch for Blue-gray Gnatcatcher, Palm Warbler, Ruby-crowned Kinglet and Yellow-rumped Warbler.

Gulf Coast and Southeast

Conditions are forecast to be less favorable than recent days for much of the region, with light to moderate migration likely across the western and northern portions of the region in light winds, diminishing precipitously farther east and southeast in the region. This forecast period will see generally unfavorable conditions for trans-Gulf flights, more easterly flow favoring circum-Gulf movements in the western Gulf region. Throughout the region, scattered precipitation and variable winds will probably contribute to migration amounts to light to moderate in many areas that are free of precipitation. The end of the week sees trans-Gulf flights begin again, with trans-Gulf inputs during the day and moderate to heavy nocturnal movements probable across many areas of Texas, and light to moderate movements in Florida; however, precipitation is possible in many other areas of the region, suggesting migration could be shut down in many of these areas again.

  • With a break in the otherwise suboptimal conditions, the first significant waves of warblers should grace the Gulf Coast. Expect localized species totals of 15 species or so by the end of the week, including the vanguard of northern nesting warblers like Black-throated Green and Blackburnian Warblers.
  • Expect a strong push of Broad-winged Hawks into Texas with some reaching Arkansas and Louisiana. Observers should be very cautious in documenting the first reports of this species and compare their arrival dates with those found in eBird for their state and county. We anticipate the first moderate push of Mississippi Kites into Texas and Louisiana.
  • Purple Gallinules numbers should continue to build along the Gulf Coast this week with most birds likely to arrive in Louisiana by the end of April. This species occasionally wanders well outside its normal range, but we don’t anticipate vagrants to the north until near the end of April (about the same time Common Gallinule returns northward).

About BirdCast

BirdCast is a project of the Cornell Lab of OrnithologyOregon State University and NOAA that studies bird migration and weather, using eBird data in conjunction with NOAA weather forecasts and novel computer modeling techniques. In Spring 2012 we will publish weekly forecasts discussing and predicting bird migration. Your observations from before and after these events will be be used to develop better predictive models relating to birds and weather. Hopefully BirdCast will provide useful alerts about the best birding days in your area and heighten general awareness about the connection between bird migration and weather.

As always, we encourage you to get out both before and after the weather event, report your birds to eBird, and let us know what you see. One of the best ways to let us know is to post to our Facebook  page — be sure to include a link to your eBird Checklist!

Posted 6 April 2012 by Christopher Wood, Andrew Farnsworth, Brian Sullivan and Marshall Iliff of the Cornell Lab of Ornithology and David Nicosia of NOAA, on behalf of Team eBird and BirdCast.

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