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Monday, February 14, 2011

Mass Movement of American Robins

American Robin Roost
Image Credit: Journey North

The return of American Robins is a clear sign that spring is on the horizon!

The vast majority of Robins head south for the winter. For most, south means Florida, the Gulf coast and central Mexico. For others, "south" may mean southern Canada or the northeast US. Here in Centre County, a few Robins are typically present throughout the winter. I observed my first two Robins of the year on January 2, at Scotia Barrens (SGL 176), and continued seeing a few each week through the end of January.

The first significant flocks I observed were seen at Millbrook Marsh on Jan 29th & 30th. I was looking for Rusty Blackbirds for the Rusty Blackbird Blitz. Late in the afternoon, small groups of Robins began coming in to roost. Over both days, about 120 Robins were tallied.

A week later, on Feb 6th, I was out at Shiloh Rd near the Benner Fish Hatchery. It was late in the afternoon and I was scanning the fields of the Rockview State Prison for raptors and owls. Although I did not pay close attention at first, I heard the flight calls from small flocks of Robins streaming overhead. I began counting the Robins as they passed overhead. Within 30 minutes, I was upwards of 1800 birds.

This past weekend (Feb 11th), I was back at Millbrook Marsh looking for Rusty Blackbirds. I was scanning the hills and fields to the northwest of the marsh and noticed a pretty good sized flock of 200+ Robins passing by the Mt. Nittany Medical Center. No sooner did the flock pass that another came by, followed by yet another, and another. Before it was all over, more than 5200 Robins were tallied. Because of my vantage point at the bottom of the hill, I undoubtedly missed a number of Robins that passed beyond my line of sight.

Oddly, both the '1800' and '5200' flocks were not heading north, but rather in a westerly direction. A quick look at the map (click here) shows that the Shiloh Rd site and the Medical Center are about 3 miles apart in a direct south-westerly line. The westerly movement of the Robins seems to have been a local non-mirgatory move, perhaps to a nearby roosting site. One likely destination would be Toftrees Gamelands. In past years, large numbers of Robins have been observed to roost there. I'll have to venture out that way and have a look.

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