Nocturnal migration was definitely in effect last night, but not for the coastal mid-Atlantic. Building southeasterly winds from the approaching hurricane appear to have kept birds from moving over New Jersey and coastal points south. Here’s the radar from 7:30pm last night through 5:00am this morning.

Frames are every 1/2 hour. Click on the thumbnail to view the full-sized animation.

Light and variable upper-level winds across most of the interior US triggered another big night of migration for the Central and Mississippi flyways, as well as the southeastern US. Hurricane Irene, now just south of North Carolina, churned out SE winds across the mid-Atlantic throughout the night which appear to have precluded any nocturnal bird migration over the region.

You can see on the velocity images that most of the movement across the radar was from the ESE->WNW, all of which was in the 10-15kt range or within the range of the prevailing winds. This suggests that whatever reflectivity was being picked up during the night was probably insect-based or non-biological (dust, etc.). Anecdotally, I noticed hundreds of Laughing Gulls feeding on dragonflies and other airborne insects last night along the Delaware Bay shore at sunset.

As Irene pushes north tonight, expect northerly winds to strengthen across middle America, triggering another night of migration along the Central and Mississippi flyways. The eastern Mid-Atlantic will most likely shut down during the storm passage, although soon after passing the conditions will improve for nocturnal migration. Expect migration to pick up on Sunday and Monday nights along the east coast as the storm clears.

Good Birding

David