Friday, September 12, 2008

Week #4 in review, and longevity records

Another week shortened by rain at the beginning (Sunday) and end (today). In between, numbers were disappointing. Over last weekend one wave of migrants representing good diversity arrived, but it continued to dissipate over the course of the week. Not helping matters was an adult Broad-winged Hawk (Buteo platypterus) that was hanging around the area the entire time. This is the first time in 16 years we have ever had an individual of this species even perch in the banding area, much less stick around for a few days! It hasn't approached the nets (Broad-winged Hawks eat primarily small mammals and amphibians, and rarely adult birds), but has a chilling presence. It may be attracted to by what seems an unusually high number of chipmunks and Red Squirrels in this immediate area. Happily, this issue should be self-limiting, as Broad-winged Hawks migrate almost en masse, with peak passage in this area tightly focused around 15 September. I think these are beautiful birds, but won't be sad to see the last of this one!

I've updated the fall totals in the right sidebar. They are quite dismal for this time of year, and our capture rate actually declined this week. We have only had 5 years out of the last 16 in which our rate was less than 50 birds per 100 net-hours, and only two where it was below 40 (our high was in 1996, when it was 63).

Only a few new species were banded this week, including Yellow-bellied Flycatcher (Empidonax flaviventris), pictured at the top of the post. This is probably the easiest eastern Empid to identify, although I have never been entirely successful at capturing their beautiful yellow-olive color with a point-and-shoot camera.

We did have a few interesting recaptures from previous years. Two were catbirds -- one was first banded as an adult in September 2007, the other as an adult in September 2006. It isn't too unusual for us to get a lot of between-year recaptures of catbirds. The third bird was a female American Goldfinch. She was first banded as an adult in August 2004. Almost four years between captures is not a record for us (that stands at 6 years, 7 months for goldfinches here), but still impressive for a small songbird. I have a compilation of some of the birds that have had at least two years between recaptures at the RRBO web site. You can also examine longevity records based on banded birds at the USGS's Bird Banding Lab web site.

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