Migration Report: 23 – 30 March 2012

Benjamin Van Doren The Cornell Lab Mar 30, 2012

Last week’s BirdCast forecast predicted a slower week of migration, as weather in the East and Midwest turned cooler with northerly and westerly flow that would be less conducive to migration. Despite a record-early spring for many species to date, we predicted that the surge of early migrants would slow to a trickle during this week across much of the area. Migration may have actually been a bit heavier than we predicted on the Great Plains, with some neat arrivals in North Dakota (see below) being exemplary. We wondered if the early surge of migration along the East Coast might still trickle northward despite the comparatively poor conditions. As always, we grade our predictions below to see if BirdCast’s prognostications are borne our by the eBird data!

Ruby-crowned Kinglet

Ruby-crowned Kinglet


At the beginning of the forecast period through the early portions of the week, migration over much of the West was not evident, with the exception of some light movement in the desert Southwest, the Central Valley of California, and perhaps a few locations across the Pacific Northwest. With light winds associated with the arrival of a weak frontal passage by midweek, widely scattered light migration developed from the Central Valley south and west through New Mexico through the remainder of the period. These conditions presumably stretched as far north as the Great Basin and portions of the northern Rockies by mid-week, but subsided late in the week as scattered precipitation moved into these areas. The Pacific Northwest continued to get hammered with storms, making conditions mostly unfavorable beyond the early portion of the forecast period.

Great Plains

The weekend began with scattered light migration in light winds associated with high pressure over the southern Great Plains. Migration continued through the weekend, mostly near and ahead of the cold front that moved into the southern Great Plains. By Monday, scattered light to moderate migration occurred in light winds associated with a then-stalled frontal boundary, allowing birds to get aloft over the central Plains, but migration was more widely scattered farther to the north. On Tuesday, a new pattern emerged; although precipitation shut down movements in the northern Plains states, conditions to the south and east were much more favorable, with birds responding to a return of southerly flow and a stalled frontal boundary just west of the Mississippi Valley. Migration volume was moderate in many areas, with some scattered heavy movements. By midweek, cooler temperatures and northerly winds associated with frontal passages in the northern Plains states kept most birds grounded there, whereas conditions in the central and southern Plains states continued to be more favorable, with primarily moderate migration in many areas and some increasingly scattered heavy movements. Early Thursday, the Great Plains experienced migration in many areas, primarily scattered light movements to the north of a stalled frontal boundary and scattered precipitation in Kansas, as well as slightly more widespread moderate movements to the south into the Ozarks.

Upper Midwest and Northeast

With the exception of scattered light migration in the northern Appalachians and the tri-state New York metropolitan area, widely scattered precipitation and cooler temperatures shut down most movements over the weekend. Early in the week, a frontal boundary with cooler temperatures and unfavorable winds spanned the region, causing little migration in the Midwest and Northeast as most birds stayed grounded. By Wednesday, diminishing winds and ameliorating temperatures facilitated some scattered light migration across portions of the upper Midwest and northern Appalachians; however, precipitation in New England prevented most migrants from taking flight. Precipitation events did result in groundings of waterbirds in several locales. High pressure’s rapid return to the region on Thursday shut down movements in most of the Upper Midwest and Northeast, and precipitation in the Adirondacks and New England again prevented migrants from taking flight.

Gulf Coast and Southeast

Pockets of moderate to heavy migration in light winds were apparent in portions of Texas and along the Gulf Coast to kickoff the weekend, after the passage of a frontal boundary during the previous week. Some light movements were also apparent as far east as Florida and the coastal bend of Georgia. Although conditions continued to facilitate moderate migration in portions of Texas through the weekend, conditions were not favorable farther east, shutting down movements across much of the Southeast. Note, however, that the Florida Keys experienced a light influx of Caribbean migrants moving north from Cuba. Early in the week, pockets of moderate migration were still apparent in many portions of Texas, but conditions were still not favorable farther east, shutting down movements over much of the Southeast. By Tuesday, with high pressure stationed off the Louisiana coast, widespread moderate migration occurred over much of central and eastern Texas, gradually diminishing to light movements farther to the east along the Gulf Coast and over the Florida Keys. With high pressure dominating the Southeastern US from Texas to the Atlantic coast for the middle of the week, widespread moderate migration occurred across much of the region from the Edwards Plateau east to the central Florida Panhandle. This pattern continued into Thursday, with moderate migration across many portions of Texas, including around areas where intense precipitation was occurring, likely facilitating some local fallout conditions of circum-Gulf migrants. More widely scattered light movements occurred over much of the Southeast, with the exception of the region around the coastal bend of Georgia south into central Florida, where moderate to heavy migrations occurred.  Additionally, light to moderate movements from Cuba into the Florida Keys occurred.


Predictions for arrivals of the following species were borne out. See their eBird maps by clicking on the species name:

    • Hooded and  Bullock’s Orioles indeed made a strong push into California this week. Note that Bullock’s and Hooded also surged into Arizona, where you can see the linear concentration of birder activity along the I-10 corridor between Tucson and Phoenix. Surely the orioles are widespread now in southwestern Arizona as well, but there are few roads and few birders in those areas. A great place for exploration! Interestingly, while Hooded Orioles have reached breeding areas in south Texas, the Bullock’s do not usually start showing up until early April. eBird highlights migration timing differences like this in new ways.
    • It is fascinating to see some of the differences in timing for certain species in the East and West. The Pacific Coast is relatively warm, thanks to the moderating influence of the Pacific Ocean, so many species return much earlier there. Widespread western species, like Warbling Vireo, often return to coastal California up to a month earlier than they do to other areas.
    • One of the more interesting regional differences in timing to check out is that of Yellow Warbler. In the Yellow Warbler map below (for March 2012) there is a lot going on. Wintering Yellow Warblers in Florida, northern Mississippi (!), and the San Francisco Bay area appear as isolated stickpins. East of New Mexico, the migrants are still on their wintering grounds in Mexico and Central America. But in southeast Arizona and coastal California, the species is starting to surge northward. As discussed above, these warmer areas tend to get earlier migrants on average, but in this case, these are movements of discrete subspecies. Yellow Warbler is highly variable with nine subspecies (eight in the U.S. and Canada) recognized in the Northern group. Of those, S. p. sonorana breeds in Sonora, Mexico, and southeast Arizona, and S. p. brewsteri breeds on the Pacific Coast from northern Baja California to southern Washington. This snapshot below from 30 March shows that sonorana has already reached the northern limit of its breeding grounds, while brewsteri has reached southern California, but has not yet moved much north of there. We’ll revisit this species two weeks from now to see what is going on in mid-April.
Yellow Warbler March 2012

Yellow Warbler, March 2012

  • Checking back in on waterfowl arrivals in the Prairie Provinces,Five more species of waterfowl arrived in   Saskatchewan this week (Gadwall, Northern Shoveler, Canvasback, Ring-necked Duck, and Greater Scaup) and Manitoba added FOY Blue-winged Teal and Canvasback.
  • Franklin’s Gull arrival, which had a “spotty vanguard” that “almost reached Canada” last week, has now penetrated well to the north and into the Prairie Provinces, with records from the past week in Calgary, Regina, and Winnipeg defining the northern front.
  • Skye Hass has been keeping arrival dates for migrants for 8 years now in Marquette County on the Upper Peninsula of Michigan, and 30 species (!!) have seen record early arrivals. Just amazing really! Although the eBird data is not quite as complete as Skye’s personal records, sorting the Marquette County arrivalspage shows at least 16 record-early arrivals in March 2012. Skye has promised these will be entered very, very soon. Apparently, he’s too busy finding new arrivals.
  • In a normal year, our late March report would be discussing Tree SwallowEastern Phoebe, and maybe early Pine Warbler arrival in New England. But this is no normal year. This week, we encourage you to check back in on the 5-year line graphs (linked from species name above) for these species to see just how exceptional this year has been. You can see that all three species almost plateaued this week, whereas they would typically be just arriving! One thing to note about these graphs is that since they are daily they sometimes reflect weather conditions as much as bird occurrence–the big dip in Eastern Phoebeoccurrence on 26-27 March in New England was because of the rainy conditions, which kept the phoebes under cover.
  • Chipping Sparrow and “Yellow” Palm Warbler migration had almost reached New England by the end of the last BirdCast period. Despite the inclement weather that was not very conducive to migration, both Chipping Sparrow and Palm Warbler continued to advance, and these March Palm Warblers are now officially one to two weeks early, since they usually arrive in April.
  • Yellow-bellied SapsuckerWinter Wren, and Hermit Thrush made some good pushes this week, although not specifically mentioned in our last BirdCast. In general, the more northerly records (in the East) are the recent arrivals and most were from the final week of March. Try clicking around to see this.
  • In the Southeast, Blue-gray Gnatcatcher, Yellow-throated Warbler Northern Rough-winged SwallowProthonotary Warbler, and  Yellow-throated Vireocontinue to consolidate their southerly nesting areas. New arrivals this week in the Southeast include a number of Kentucky Warblers, widespread Hooded Warblers, and a few Swainson’s Warblers.
  • Early spring or not, some species just do not return early. Research is ongoing as to why, but long-distance migrants (those coming from South America for example) probably are less able to time arrivals based on local conditions. Perhaps this explains why Chimney Swifts this year are “on time” and not early inTexas/Louisiana and Georgia/South Carolina/North Carolina. eBird data are revealing certain other species to not have advanced migrations as well, and understanding these patterns is one of the cutting edge areas of migration and climate change research happening right now (See recent Hurlbert et al. paper for more theories as to why).

Checking back in on the on the March 2012 White-throated Swift map, we see that it still hasn’t shown much change from last week, with few records north of northern California, Arizona, or Colorado. The one outlier was a count of six in western Washington on 25 March. Is it simply lack of coverage or have the swifts just not headed north yet?
Here are a few additional cool lists from our eBird community:

  • Sandy Aubol birded Grand Forks, ND, and verified BirdCast’s predictions for migration into the area on 27 March. Among the migrants on her list are very early Northern Flickers, Ruby-crowned Kinglets, and a nicely-photographed Hermit Thrush, along with more expected late March migrants like American Robin, Golden-crowned Kinglet, and Brown Creeper.
  • David LaPuma, reporting from Wisconsin on 23 March, was one of the many eBirders to notice his “FOS” (First-of-season) Yellow-bellied Sapsucker this week,
  • James Fox sent us a note about his first Blue-headed Vireo of the season in the Shenandoah region of western Virginia from 28 March, a tad early. Also on his list were Louisiana Waterthrush and Chipping Sparrow, species that have been back for at least a week in that area.
  • Cape May eBirder Tom Reed regularly watches for migration going past the tip of the point and always has something interesting for our BirdCast. His watch on 25 March produced some waterbirds and herons moving into light northerlies.
  • As a reminder that this early spring does not pertain only to migration, this list from Eric Soehren and John Trent documents a record early nesting date for Louisiana Waterthrush, with a completed nest on 22 March. Eric returned 23 March and found no eggs, and then again on 27 March to find the nest destroyed by a predator, but did find egg remnants under the nest, setting a new record early egg date (of 24-26 March). The previous all-time earliest egg date, according to the Birds of North America (subscription required), is 8 April from Georgia.

Posted 30 March 2012 by Marshall Iliff, 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.