Early spring migrants in the middle of winter

Andrew Farnsworth The Cornell Lab Feb 01, 2013

January in the temperate Northern Hemisphere is not typically a time that most consider as falling within “spring migration.” Rather, local and facultative movements of  wintering birds and irruptive movements tend to dominate birding discussions, observations, and field trips. However, here we are on 1 February talking about the arrivals of the earliest migrants in the US. Purple Martins have started returning to the southern tier of the US, appearing from early to mid January and increasing in numbers throughout the month.

Purple Martins are perhaps the earliest spring migrant to arrive. Numerous observers from Texas to Florida reported martins during the last 2-3 weeks of January.

Although these arrivals are on the extreme early end of spring migration, it is not too early to begin to consider more substantial movements of migrants. Forecast models for the end of the first week and beginning of the second week of February 2013 suggests that a pulse of warm air will occur in the Northeastern US. This pulse may be sufficient to facilitate movements of early migrants like some waterfowl, raptors, sparrows, and blackbirds. Team Birdcast will follow up on this pattern next week to see how strong it is forecast to be and how extensive.

These images show the results of two different models that predict the distribution, extent and magnitude of temperature anomalies. The images show isohypses, or lines of constant height, particularly 500mb Heights, which describe the height in the atmosphere at which pressure reaches 500mb. Low values in blues indicate anomalously colder air (troughs) whereas high value in reds (ridges) indicates anomalously warmer air (warm air expands producing higher heights). Notice that forecast models predict warmer temperatures for the Northeastern US in the first 7-10 days of February 2013. Such warming trends may facilitate the movements of some early migrants such as waterfowl, raptors, sparrows, and blackbirds.