Friday, April 27, 2012

Bird Migration Forecast

Cornell's eBird website has released their bird migration forecasts for this week. I've excerpted the sections relevant to folks here in the northeast, but you can read the entire forecast here.

BirdCast Migration Forecast: 27 Apr - 3 May

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.

Daily forecast maps are available here.

Olive-sided Flycatcher
Olive-sided Flycatchers should be on the move this week, especially across areas along the West Coast. An interesting species, Olive-sided Flycatcher shows a strong pattern of earlier arrival on the West Coast, followed by a later May arrival into the eastern and northern portions of its range. Widespread geographically, Olive-sided may be a species worthy of further scrutiny, as its taxonomy is still confused. In the West birds average larger, especially the bill, and this difference is most pronounced in birds breeding in southern California. But there are other differences not readily apparent in the museum tray: the above mentioned migration timing differences, and perhaps most importantly a subtle difference in the songs of Eastern and Western birds: listen carefully to the length and delivery of the middle note of the three-parted song. More study is needed to describe these differences, but keep an eye out across the West this week for returning Olive-sideds, as well as a careful ear for their distinctive 'quick-three-beers' song. Observers in the East should also be alert, but don't expect to see Olive-sideds arrive there for another ~2 weeks.

Upper Midwest and Northeast
Southeast flow across the Upper Midwest will turn more southerly as high pressure moves south from Canada over the weekend. By Sunday morning we should see a strong interaction between the next cold front approaching from the west and the Canadian high now over the Mid Atlantic. This southerly flow will trigger widespread migration into the Upper Midwest from Sunday night into late next week. Because this southerly flow extends down into Texas, expect many Neotropical migrants to show up throughout the Upper Midwest during the forecast period. Birders in northeast Wisconsin and the central and western Upper Peninsula of Michigan should be on alert for fallout conditions on Monday morning due to thunderstorm potential, as well as concentrations along the northern and western shore of Lake Michigan as birds get pushed east on southwesterly winds. This could represent the first big push of neotropical migrants into the the Upper Peninsula. While winds should continue to be favorable across the region through mid-week, some storm activity moving into the Upper Midwest will likely shut things down locally. Conditions will deteriorate into late next week as precipitation becomes more widespread and winds turn northerly.

Birds will be grounded over the Northeast at least through Sunday as high pressure moves across the Great Lakes, pushing the low out of Eastern Canada. However, by Monday night conditions improve for most of the region and birds should be expected to move into the Ohio Valley again. This heavy push of migration should make Tuesday the first day that double digit warbler lists are likely in the Ohio Valley, with all but the last-arriving warblers (e.g., Mourning, Wilson’s, and maybe Blackpoll) making up the species mix. As high pressure moves off the New England coast on Monday night, expect things to really heat up with strong convection bringing birds out of the Southeast and into the region by Tuesday morning. Heavy precipitation along the southern Great Lakes and Ohio Valley could mean fallout potential on Tuesday and Wednesday mornings. Birders should keep an eye on the weather to see where they’re located in relation to the frontal boundary on Monday and Tuesday nights to determine whether to go north or south in anticipation of a fallout. Similar rainy conditions over the Coastal Mid Atlantic and New England on Wednesday could produce concentrations of migrants into Thursday morning as west winds convey migrants eastward.

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