High pressure will dominate much of the country during this forecast period. The West will experience widespread light to moderate migration this week, as high pressure and warmer temperatures build in across most of the region. Moderate to heavy movements will occur in the Great Plains, despite scattered precipitation that may inhibit movements locally. Despite largely unfavorable winds aloft for much of the period, most areas of the Upper Midwest and Northeast will experience moderate to heavy movements this week; the threat of scattered precipitation will diminish movements in some locations. The Gulf Coast and Southeast should see an influx of trans-Gulf migrants in the western Gulf early in the weekend, in the eastern Gulf early next week, and generally widespread moderate to heavy movements inland, despite some periods of unfavorable winds aloft and the threat of scattered precipitation early in the period. Birders in coastal areas should watch for potential fallouts through the early portion of the week.
As one might expect near the peak of spring migration diversity and abundance, this week saw nights with moderate to heavy migration across many areas of the continental US. In fact, higher than expected migration amounts occurred on several nights during the forecast period in multiple different portions of the region. Although we could easily chalk these anomalies up to slight differences in the observed weather relative to the original forecast, a better explanation is that we underestimated birds' drives to reach their destinations! Read below for a brief summary of last week's migration, and read this week's BirdCast Forecast to know what to expect in the week ahead.
eBirders often email us and ask where they should go birding in order to make the biggest impact in regions with little data. It's perhaps little surprise that eBird checklist submissions are most dense in areas with large human populations, so getting away from those areas is a good first step for filling in the data gaps in eBird. But seeing these gaps can be really astonishing, and with the help of map wizards Paul Hurtado and Tom Auer, we've come up with a few neat ways to visualize eBird data density at the county level. These maps are a visualization of the total number of eBird checklists submitted in each US county in the month of May across all years, or the total number of checklists per square mile of county area--a better way to see data density in states with large counties. So find a county that has sparse data, and then go do as many eBird checklists as you can there this May!
As several low pressure centers and their associated precipitation progress across the country, migration levels will vary more than usual. Primarily light to moderate movements will occur across more southerly portions of the West, whereas precipitation and generally unfavorable winds aloft will keep most migrants in more northerly portions grounded. Although a few areas of the Great Plains may see moderate to heavy movements early in the period and scattered movements for the remainder of the period, most areas will experience rather poor conditions for migration on most nights this week. Poor migration conditions will prevail more often than not across the Upper Midwest and Northeast, but birders should watch closely for marginally favorable migration conditions to develop, possibly producing moderate movements and fallouts may occur. The Gulf Coast and Southeast are in for another week of moderate to heavy movements, punctuated by a strong possibility of fallout conditions from Texas to the eastern Gulf late in the period.
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.
While most of Team eBird is down in Texas making Big Day history, I, David La Puma, have been charged with filling in for them in writing this week's migration forecast. In doing so, I have also called upon a team of migration experts from across the country to weigh in on the regional components of this most exciting BirdCast. Thanks to Drew Weber, Greg Haworth, Max Henschell, Tom Auer, Tim Schreckengost, Angel and Mariel Abreu for their contributions and local expertise. Thanks also to Team eBird’s Brian Sullivan and NOAA’s Dave Nicosia for their insight into species distributions and weather respectively. Now, let the games begin.
