Migration Report: 27 April – 3 May 2012

Benjamin Van Doren The Cornell Lab May 04, 2012

Late April and early May is peak migration for many of the more southerly sections of the United States, with the northern states and southern Canadian provinces seeing peak movements during the second and third weeks of May. By late April, the latest-arriving migrants in Texas and Florida should be making their first appearances, and this was true this week. Almost regardless of the weather, new arrivals and obvious migration were apparent throughout North America this week. With so many birds on the move, weather had a profound effect on bird movements this week. The amazing fallout on Key West is one such example. In general, cool and wet weather suppressed migration in the West and Northeast, but southerly flow allowed for some great movements into the mid-continent. When migration is stalled by weather (as it has been this week), be prepared to get out birding as soon as the weather breaks, since it could bring a flood of migrants! Read below for a summary of last week’s migration, and read this week’s BirdCast Forecast to know what to expect in the week ahead.

To see this week’s radar animation, click here.

Black-throated Blue Warbler. Photograph by Jim McCree.

Black-throated Blue Warbler. Photograph by Jim McCree.

This week we begin by highlighting a new map product from the American Bird Conservancy, since this new map ties in so well with the goals of BirdCast. Our usual migration report can be found below as well.

Bird migration map

The BirdCast project promises to advance our understanding of bird migration and movements in near real-time, drawing on your eBird observations, weather information from NOAA, and new computer modeling techniques. The ability to predict and monitor large-scale migratory movements has many important conservation implications. We already know that artificial lighting from city buildings, cell phone towers, and other structures pose a significant risk to migrating birds, which may become disoriented and collide with wires or buildings.  Lights are particularly dangerous for birds when foggy conditions occur on nights of high volume migration, and this can result in significant mortality. One of the goals of BirdCast is to provide information on migratory movements that might be used to employ lighting of structures in more strategic ways; for example, it could be turned off when risks of bird mortality become especially high.

Another project goal is to provide better information on bird movements to groups that are seeking to highlight areas where birds are vulnerable to potential mortality. Specifically, wind energy development may pose significant risks to migrating birds, since the best wind resources to develop may lie in the same areas as those used by migrating birds (e.g., along ridge lines or mountain passes). With the need for green, sustainable energies, wind power is expanding rapidly, and the wind industry and ornithological communities have a pressing need to better understand the conditions and areas that concentrate migrating birds. To that end, the American Bird Conservancy has released a new interactive web-based map showing the areas where birds would be most vulnerable to mortality from wind development. Forecasts and improved knowledge of the distribution of migrating birds in space and time will improve products like this, which can be used to develop wind energy with minimal impacts to birds.

Scattered precipitation shut down most movements in northern portions of the region to begin the period, whereas California and the Desert Southwest continued their trends of more widespread light migration. However, by Saturday and Sunday many areas of the region, with the exception of Montana and the northern Rockies, experienced increasingly widespread light to moderate movements as high pressure built over the Great Salt Lake. Note, this included some areas of heavier movements in the Pacific Northwest early Sunday morning. As another low pressure system moved toward the coast to begin the week, and areas away from the coast continued to experience light to locally moderate migration, particularly in the Desert Southwest and Great Basin. As this system moved east, more southerly portions of the region experienced primarily light movements with some locally moderate migration in coastal California; this pattern was evident through the remainder of the forecast period.

Great Plains
Substantial instability in the atmosphere was a hallmark for the period as low pressure moved through the region, facilitating migration in many areas but with substantial regional variation in volume and extent.

Migrant landbirds and shorebirds both started to heat up this week on the Great Plains. Shorebirds are one of the real highlights of the Great Plains, as most of the world’s population for species like American Golden-Plover, Buff-breasted Sandpiper, Baird’s Sandpiper, Pectoral Sandpiper, White-rumped Sandpiper, and Hudsonian Godwit funnel through a narrow corridor between the Rocky Mountains and the Mississippi River. This week saw some impressive counts coming in from known concentration points, and Quivira NWR in Kansas is one of the more famous ones. This 28 April list by Michael Heaney has 21 species of shorebirds gives a taste for how remarkable spring shorebirding can be

Upper Midwest and Northeast
The combination of instability in the atmosphere and a large pool of available migrants created interesting conditions this week in many portions of the region, with concentrations and fallouts occurring in numerous locations, especially in the Great Lakes region (see below, for example). The period began with the passage of a strong cold front that shut down movement in all but the far western portions of the region; light migration was widely scattered in these areas. With high pressure over the Great Lakes, and precipitation over western areas to begin the weekend, light migration was the norm in precipitation free areas around the Great Lakes, increasing in extent and amount to the south and east where locally moderate and heavy movements occurred closer to the Appalachians. As high pressure strengthened to end the weekend, most areas of the region experience little movement, other than widely scattered light migration. Monday saw high pressure move east, continuing to shut down much of the Northeast’s movements with cool temperatures and unfavorable winds; however, in precipitation free areas to the west and south, moderate to heavy movements occurred, particularly in the Ohio River valley and just to the west. As the high pressure center departed to the east, moderate to locally heavy movements occurred across a wider geographic area in areas free of precipitation; the Great Lakes and northern New England experienced primarily scattered light movements. Instability associated with low pressure and a stalled front over the northern Appalachians facilitated moderate to heavy movements in many areas away from precipitation, with the continued exception of northern New England which was still under the influence of high pressure to the east. The period ended with much the same pattern, though more extensive heavy migration occurred over much of the Upper Midwest.

David La Puma and Adrian Lesak had quite the eventful morning walk to work in Madison, WI, taking five hours to complete what is typically a 30-minute walk. Shortly after 7am, the two met in Hoyt Park, where La Puma found Lesak under some oaks saying, “I haven’t moved from here since I got here. I don’t know what to do–there are birds everywhere!” By the time the two had finished their walk, they had seen and heard 21 species of warbler, 5 species of vireos, 2 species of tanagers, and tallies some awesome numbers – 94 species and almost 1500 individuals. Here are six eBird checklists from the ‘morning’ walk:  Hoyt Park,  Hoyt Park OverlookQuarry ParkShorewood Hills (one stop),  1918 Marsh and  Picnic Point to Lakeshore Preserve.

In the Northeast, migrants mostly continued to trickle in. In the Mid-Atlantic though, some excellent movements occurred. For example, Todd Day birded central Virginia and had 20 species of warbler on one walk on 3 May. Most remarkable were the seven Cape May Warblers, an unusually high total for this area that usually lies east of the main corridor for the species.
Gulf Coast and Southeast
Circum-Gulf and Mexican and Caribbean trans-Gulf migration were in full effect for much of the period across the region. Moderate to heavy migration was pervasive over much of the region to begin the period, with the exception of areas close to the frontal boundary in the east. This pattern continued, intensified, and expanded eastward through much of the remainder of the period, with only scattered areas of lighter migration. Of particular interest in this region during the forecast period are areas where precipitation interacted with moderate to heavy movements underway. Note that precipitation over the coastal bend of Georgia and the Carolinas put down migrants in these areas. On early Sunday morning, precipitation was distributed extensively from the Florida Straits into the Bahamas and large volumes of arriving migrants encountered these storms, precipitating an historic fallout on the Florida Keys.

This fallout was perhaps most significant at Fort Zachary Taylor, which is essentially the westernmost point of the Florida Keys (not counting the Dry Tortugas). This park provides first landfall for passerines caught over open water to the south and west and struggling back towards shore. After the storms of 30 April, at least two eBirders were there to witness and document the fallout. Carl Goodrich arrived around 8:00 and reported thousands of birds flying past him out of the park. His checklist reports 20 species of warbler and some really exceptional counts. Morgan Tingley arrived a bit later in the morning and encountered similar numbers of birds. His checklist contains comments such as “500 Ovenbirds – Likely 1000s around in park” and “5000 Black-throated Blue Warbler – Had up to 100 on 10 ft of pathway at once. Likely true number in park around 25,000”. Between the two observers, eleven species of migrant were tallied in the 100s and four were estimated at 1500 or more!  It is hard to imagine seeing 5000 Black-throated Blues, 2000 American Redstarts, 135 Yellow-billed Cuckoos, or 600 Cape May Warblers! Events like this are amazing to witness, but they may cause significant mortality, since many of the birds do not arrive safely to the Florida Keys to ride out the storm.

Finally, those of us on Team Sapsucker can offer our own migration report from the Texas Gulf Coast for 27-29 April. On 27 April, we conducted our annual Big Day fundraiser, on which we strove to break last spring’s record-breaking run of 264 species. Starting in Uvalde, just south of the Texas Hill Country, we encountered a few migrant warblers (Nashville, Orange-crowned, Yellow) as well as a nice suite of Mexican and Hill Country breeders. Moving eastward, the high clouds provided a great backdrop for migrating hawks, and on the drive we saw Franklin’s Gulls, Mississippi and Swallow-tailed Kites, Broad-winged Hawks, and a number of other species aloft. Although relatively few migrants were apparent at our inland stop in the Texas Pineywoods west of Houston, were were hopeful that weak winds over the Gulf the previous night coupled with strong southerly surface winds would mean a good, late movement of birds over the Gulf Coast. When such movements occur, some birds always stop in the afternoon to refuel at places like High Island. Whereas these conditions are certainly nothing like a “fallout”, they can provide some good birding. We found the most migrants on the sheltered side of High Island–at Smith Oaks–and did our best to recreate an accurate eBird list despite the rapid pace of the Big Day birding. In a little over an hour of birding near dusk, we managed 10 warblers, two tanagers, three species of spotted thrushes, several flycatcher species, and one migrant vireo. Our final species tally of 264 (tying last year’s record!) should give a good sense of what migrants we found–and did not find–on our transect across Texas last week.

Thanks, as always, to those of you who supported the team and followed our progress on Facebook — from the highs (Rufous-capped Warbler, Purple Gallinule at 11:56 p.m.) to the lows (flat rite, traffic jams, missing Great Crested Flycatcher!) This is an critical fundraiser for eBird and the Lab’s Conservation Program and we could not have done it without your support!

Posted 4 May 2012 by Andrew Farnsworth, Marshall Iliff, Christopher Wood, and Brian Sullivan of the Cornell Lab of Ornithology and David Nicosia of NOAA, on behalf of Team eBird and BirdCast.