Migration Report: 6 – 12 April 2012

Benjamin Van Doren The Cornell Lab Apr 12, 2012

We will step through last week’s BirdCast forecast to see how it did with predicting the bird movements and species arrivals. The overall pattern has been of continued decent conditions for movement through the mid-continent, but northerly winds and cooler temperatures have essentially put a cork in the migration in the eastern third of the country. As a result, there are probably a lot of passerines waiting for good conditions to move (especially Blue-gray Gnatcatchers, Blue-headed Vireos, Louisiana Waterthrushes, and other species that usually arrive in early April). When the weather breaks this week (see the current BirdCast forecast) we can expect the floodgates to open. Until then, check out last week’s analysis to see what migration has been happening even in the absence of great conditions.

Broad-winged and Swainson's Hawks were widespread migrants last week.

Broad-winged and Swainson’s Hawks were widespread migrants last week.

See the week’s radar results here

Last week’s BirdCast made some predictions about what might occur this week, so this week we’ll step through some of those species to see what actually happened. But first, let’s look at our feature species: Virginia Rail. Although there are still not many reports of Virginia Rail from the Upper Midwest, the species seems to have arrived in force in the Northeast. Of course, this is a secretive bird, so it often does take a bit of special effort to find. One of the northwesterly outliers is this checklist with a Virginia Rail from Cherry River, Montana, which has some lovely photographs embedded in it.

Weekly Summary

Below are our weekly summaries of weather and migration activity, from our BirdCast radar analysis, followed by our species-by-species summaries to follow-up on last week’s predictions. See the radar animation here to follow along with the week’s movements and migration.


A substantial cold front had passed across most of the region by 6 April allowing for scattered light migration to occur across much of the region. Ahead of the frontal boundary, light migration occurred in eastern Arizona and New Mexico. As high pressure continued to build across the region for the weekend, more widespread light and moderate migration occurred in more western portions of the region, particularly by Sunday. This period saw little evidence of movements in northern portions of the region. By Wednesday coastal precipitation events shut down most movements, whereas interior areas continued to experience scattered light migration; this pattern included areas of the Central Valley of California and mountainous and northern portions of the region, from the Great Basin and northern Rockies south into Utah and Colorado and the Desert Southwest. By the end of the forecast period, scattered precipitation across the northern and central portions of the region stopped much movement, though scattered light movement persisted through the Desert Southwest and southern California.

Purple Martin – Although the widespread Pacific coast arrival is yet to come, the first arrivals did indeed occur this week in northern California (e.g., Arcata March, 9 Apr), Oregon, and Washington (e.g., Stiegerwald Lake NWR, 12 Apr). The one bird so far in Arizona was not the cactus-nesting population, but seemed to be a bird interested in possibly nesting in pines 31 March.

Common Loon – With loon migration well underway, and some birds already returning to breeding areas, the 2012 Common Loon map is filling in. Expect more loons to be moving overland for the next month or so.

Shorebirds – Although they first started returning in the last two weeks of March, Long-billed Curlews continued to fill in their breeding areas (see 2012 map). Although Black-necked Stilts have now been seen widely in Washington, eBird did not receive any reports from British Columbia (as predicted, although we did get two reports from neighboring Alberta on 10 Apr and 11 Apr. A somewhat better result for BirdCast, the front lines of American Avocet’s spring migration reached Montana and Washington and the first arrivals were noted in British Columbia 8 Apr, Alberta 10 Apr, and Saskatchewan 6 Apr.

Greater Pewee – Indeed, Arizona’s first arrivals occurred this week, with Carl Lundblad finding the earliest one on 6 Apr on Mt. Lemmon, near Tucson. Impressively, he also had a Buff-breasted Flycatcher, which was first found in the area on 27 March. Although we didn’t mention Buff-breasted Flycatcher in our BirdCasts this record is interesting since it is at the species’ northernmost outpost and since it shows how early this species returns. Many Empidonax, including Willow Flycatcher and most species in the East, do not arrive until late April or May.

Great Plains

To begin the weekend light migration occurred mostly in the far eastern portions of the Plains states in light southerly winds in advance of the cold front passing through the region. After the passage of this front on Sunday, migration all but shut down across the entirety of the region. As high pressure again built into the region, and a secondary low formed and moved east toward the Great Lakes, conditions over southern and eastern portions of the region spawned some light movements with widely scattered moderate movements in Oklahoma. This pattern continued into Tuesday and Wednesday, with some slight northward expansion of the movements into Kansas and Nebraska, even as far north as the border states (though only sparse light movements occurred in those areas in light winds near the center of high pressure). Similar light movements were apparent on Thursday, though primarily scattered in the eastern portions of the region from Oklahoma north to the border.

Shorebirds – Shorebirds pushed into the Great Plains in force this week. We were probably a bit out in front of the Wilson’s Phalaropes with last week’s BirdCast. Although we predicted arrival through much of the Great Plains and into the Dakotas, there were only single reports from Kansas and Nebraska last week.

Yellow-bellied Sapsucker – As predicted, they have continued to fill in their breeding range this week, and the grid map now shows them across Wisconsin. Look for them to fill in the state of Minnesota next week.

Blackbirds – Check out the Yellow-headed Blackbird map to see how they are filling in their range. Their return to breeding areas will continue over the next several weeks.

Upper Midwest and Northeast

With few exceptions, radar was quiet in the Northeast from a bird migration perspective, primarily as a result of cooler temperatures, passing precipitation, and northerly flow. The exceptions: Sunday saw sparse light migration in some areas from Pennsylvania east through New York, whereas Tuesday and Wednesday saw light migration in the far northeastern portions of the region. The Upper Midwest fared better, beginning the analysis period with local light to moderate migration in the western Great Lakes area, expanding early in the weekend across the Great Lakes and south into the Upper Mississippi and Ohio River valleys. However, precipitation and changing winds associated with the front that passed through the region shut down movements in most areas, with light movements and locally scattered moderate movements primarily restricted to a zone just west of the Appalachians from Lake Erie south into Kentucky. Most of the remainder of the period saw largely unfavorable conditions for extensive movements to occur, as some scattered precipitation followed by northerly flow were not conducive to many bird echoes on radar.  Note that Thursday saw some scattered light movement in the far northwestern portions of the region in high pressure and light winds.

  • The first significant push of shorebirds should occur with Greater and Lesser Yellowlegs expected throughout as well as Dunlin and Pectoral Sandpiper.
  • We predicted widespread Barn Swallow arrivals (along with advancing Purple Martins). Compared the current map of Barn Swallow with the one for just Marchto get a sense for how quickly this species has filled in its range in early April. Despite the warm blast in the first three weeks of March, Barn Swallow was a species that did not arrive much earlier than its recent average. Many ornithologists believe that longer-distance migrants (like Barn Swallow) are much less able to adjust their migrations in response to climate change than species like Tree Swallow (which are short distance migrants). Whether individual birds can respond is something of a different question as compared to how evolution will drive the average migration of the species. For example, Tree Swallows clearly showed an early arrival this season due to responses by the individual birds (i.e., it is warm, so I will migrate early), whereas natural selection could act quite strongly on birds that are arriving too late in warm years, affecting rapid changes in the average arrival times. Watching how these two factors play out will be interesting for eBirders and scientists to watch in the coming years.
  • The first Blue-headed Vireos have indeed appeared across Pennsylvania, but have yet to push into New England the Upper Midwest, so our BirdCast prediction of the first birds hitting those areas was a bit premature. The vireos are surely stalled, along with many other birds, bt the recent cold weather and northerly flow. Expect that to change 15-16 April!

Gulf Coast and Southeast

Widespread precipitation kept most birds in the Southeast grounded to begin the period, with Texas being the exception; widespread light movements occurred to the south of high pressure near the Texarkana border, becoming moderate farther south toward the Mexican border where more southerly winds occurred. The weekend saw more favorable conditions expand eastward, with moderate migration occurring over many areas of Texas diminishing to widely scattered light migration in the southern Appalachians on Saturday increasing to more widespread moderate movements on Sunday with locally heavy flights in many areas. Texas continued to experience local moderate to heavy flights to begin the week, whereas movements decreased in extent and amount in eastern portions of the region; a notable exception is Florida, where conditions were favorable for locally moderate to heavy movements ahead of a frontal boundary. Similar conditions prevailed through the middle of the week. Note, light movements of birds from Cuba into the Florida Keys occurred nightly from Monday through Wednesday. Note, also, a cold front pushed through the region and high pressure prevailed over much of the Gulf during much of this analysis period, biasing migration away from trans-Gulf flights toward circum-Gulf flights. By the end of the period, southern Texas continued to see moderate movements with locally heavy migration, gradually diminishing moving eastward across a stalled frontal boundary and then becoming minimal at best approaching the Atlantic coast of the region.

  • Last week’s prediction said “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.” This seems to be about right — Trip Davenport had 15 species at Paradise Pond on 11 April; Luke Seitz recorded 14 species at High Island on 9 April. The High Island bar chart shows as of 13 April they had recordeed 21 species of warbler this week (not counting Yellow-breasted Chat, since it isn’t a warbler!). Other Texas hotspots has the following totals:  Blucher Park, Corpus Christi (16 species); Port Aransas area (24 species); South Padre Island (25 species). Many places reported Black-throated Green and Blackburnian, along with the first arriving Cerulean Warblers, always a great bird to see on migration.
  • Broad-winged Hawks are indeed streaming into the country, with many first arrivals this week. Almost the entire population migrates up through a narrow band in southeast Texas in spring, and thousands will continue to funnel through that area for the next few weeks. On the current year’s Broad-winged Hawk mapyou can almost see the river of hawks flowing north and east–it is very cool. check it out now before it fills in more! Mississippi Kites arrive later and follow a similar path. This year’s map shows the first arrivals coming through Texas and reaching Louisiana and the Carolinas. Expect many more in the next few weeks!
  • Purple Gallinules did show their first arrivals on the Gulf Coast this week. Watch for numbers to build and expect a few vagrants to the Midwest and East Coast from late April to late May. A vagrant Purple Gallinule is always a sensation, so watch and listen for them in brushy pond edges and marshes, and be aware that they sometimes turn up in absurdly weird spots too, like parking lots, gardens, and lawns.

Posted 13 April 2012 by Marshall Iliff, Andrew Farnsworth, Christopher Wood, and Brian Sullivan of the Cornell Lab of Ornithology on behalf of Team eBird and BirdCast. Special thanks to David Nicosia, our partner at NOAA, for the weather maps and analysis in our BirdCast predictions.