Eastern Promises: Update 18 March 2013

Andrew Farnsworth The Cornell Lab Mar 18, 2013


Fieldfare, Carlisle, MA, 17 March 2013. Photographed by Jeremiah Trimble

We continue to track the Eastern promises that we highlighted in December, as this past weekend provided yet another tantalizing example of the potential fruits of such promises. A Fieldfare was discovered in Carlisle, MA and seen and photographed by many. This is no doubt one of the prizes of any year of Eastern Promises! Without seeming greedy, have we any more prizes heading to our shores?

Forecasts once again suggest the potential for European vagrants to appear in Northeastern North America over the coming two weeks. The two images below show the surface forecasts for the 20-21 March 2013, and the highlight to note is the strong easterly and northeasterly flow over the North Atlantic. As a strong low pressure system moves East across the ocean, and high pressure sits over Greenland, strong flow from the East connects the Palearctic and Nearctic regions. Look in particularly at the packing and orientation of isobars (lines of constant pressure) to the South and East of Greenland. This could facilitate the arrival of European shorebirds like European Golden-Plover (which is just arriving in Iceland) and Northern Lapwing, as well as more European passerines like Fieldfare and Redwing (which usually arrives in greater numbers in Iceland right around 21-25 March). Birders should be on alert in the Northeastern US and Atlantic Maritime Canada, particularly in areas where shorebirds and other wading birds concentrate and where large numbers of American Robins are present.r



Of course, at the heart of this pattern is a feature we have discussed and highlighted numerous times, the North Atlantic Oscillation index.  During periods when this index has a negative value, and high pressure persists over the North Atlantic, the easterly flow we show above and described in previous posts prevails. The coming two weeks have NAO index forecasts that are more strongly negative than past weeks. Will this pattern bring more European vagrants? Help us figure it out! Go to your favorite patch and go birding!