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.
To see this week’s radar animation, click here.
In areas free of precipitation, light to moderate migration was frequent on many nights across the region. High pressure built across much of the region through the week, and birds took advantage of clear and favorable conditions. This pattern was most evident early Wednesday morning, when light to moderate movements occurred in many different areas of the region. By Thursday, however, increasing and scattered precipitation and less favorable winds aloft began to slow movements in more northern and western portions of the region.
Moderate to heavy migration occurred across the region over the weekend with low pressure and favorable migration conditions over the Rockies and central Plains. As this pressure center became better organized and passed through the region early in the week, migration volume declined precipitously and shut down in areas of precipitation. Scattered light migration persisted after passage during midweek, and then built into more widespread heavy movements by Thursday as high pressure again began to dominate over the Rockies and across the middle of the US.
Upper Midwest and Northeast
Migration volume varied widely across the region, largely as a result of the distribution of precipitation and the passage of a frontal boundary. In areas free of precipitation, scattered heavy movements occurred frequently during the period along with more widespread light to locally moderate movements. As low pressure intensified and passed through the region on Wednesday night and Thursday morning, all but the most western portions of the region saw migration shut down due to precipitation, northerly winds, and cool temperatures.
Birding in city parks can be lively, at times incredible experiences. The first full week was certain lively in Central Park and Bryant Park, as evidenced by the diversity that Jacob Drucker and Ben Cacace observed, respectively.
Gulf Coast and Southeast
To begin the period, migration volume was typically moderate to heavy, particularly in Texas and Florida, as trans- and circum-Gulf movements continued to prime the migration system. Portions of the southern Appalachians and eastern Gulf Coast experienced less intense movements, to some extent a function of scattered precipitation moving through these areas. By Tuesday, a strong frontal boundary moved through Texas and out into the Gulf of Mexico, eventually diminishing the extent (though not the amounts) of movements in many areas of the region. However, by Thursday heavy movements were again the norm over Texas, whereas birds in many eastern portions of the region did not take flight in the aftermath of frontal passage.