Monday, October 15, 2012

American Robin

These two photos are of young American Robins that I banded this fall. The top bird seems to be in odd plumage, with its chestnut eye ring, supercilliary stripe, and throat. Normally robins look more like the bottom robin, with a white eye ring and throat. A cursory review of my field guides and banding references fails to come up with an explanation for the chestnut bird.

Even more curious has been the relative lack of robins at my banding stations in Northfield. This spring (April through June) I only banded 7 robins. In July and August I banded none--no adults, no speckled fledglings! September and October has welcomed a plethora of migrating thrushes, with 55 robins banded so far.

I can not explain this summer's lack of robins. According the the University of Wisconsin, however, robins are West Nile Virus' "Super Spreader." University researchers conclude that robins are "more important to the spread of West Nile in the Northeast and Midwest than any other host." This year's West Nile Virus season has been intense. Scientific American suggests that West Nile Virus is responsible for the leveling off of once-growing robin populations. Perhaps our local robins were adversely affected.

1 comment:

  1. I wonder why they were scarce in your area too. I saw quite a few this summer in multiple counties, Dan. Since migration has started this fall I have seen many hundreds.