Banding summaries: 2004-2008

Fall 2005

Our 14th fall banding season took place on 51 days from 17 August to 5 November. An average of 17 nets (12 meter equivalent1) were open an average of 4.2 hours per day.

Golden-winged Warbler

We ended up banding 1626 new birds and had 278 recaptures of 72 species A total of 1959 birds were netted (this includes birds released unbanded). Our capture rate was 55.9 birds per 100 net-hours. It was a pretty average fall up until October 27. The last six mornings of banding, we banded 497 of those new birds, nearly a third of the season total. For 3 of the days, only half the nets were open! Capture rate for this period was 164.5
birds per 100 net hours. Here are previous fall averages for comparison:

Fall 2005 Previous
fall mean
Days open 51 51
New birds 1626 1205
Total birds 1959 1554
Capture rate 55.9 52
Species 72 70

On October 11, RRBO reached a milestone: the 25,000th new bird banded, a White-throated Sparrow. Read about the relevance of that milestone in the University press release.

As far as other numbers, most notable was the large movement of goldfinches commencing on October 27. We ended up banding 247, shattering our previous fall total of 166, and over 200 of them were in the last six days. The other species that made up a large part of the latter part of the season was American Robin. We bested our former record of 351 by several birds.

The top ten bird species banded (new captures only) were:

American Robin — 353 (new record)
American Goldfinch — 247 (new record)
Gray Catbird — 155
White-throated Sparrow — 113
Song Sparrow — 57
Swainson’s Thrush — 50
Magnolia Warbler — 37
Cedar Waxwing — 36
Yellow-rumped Warbler — 35
White-crowned Sparrow — 32

Notable species included Blue-winged and Golden-winged Warblers, Scarlet Tanager, and Sharp-shinned Hawk.

Numbers and trends
The best way to examine trends in banding data is to look at the number of birds banded standardized to reflect the amount of effort: birds per 100 net hours (/100 NH). I examined 20 species in which the fall mean is at least 20 birds per year. Eleven had decreases /100NH, and nine had increases.

For a few of those species, the decreases probably represent actual trends.

We talked about the long-term decline in Gray Catbirds in both 2003 and 2004. Again, the number of catbirds banded was about 11% lower than the previous mean, but as you can see from the graphic, the trend is slowly moving up again.

Swainson’s Thrushes and Hermit Thrushes both had decreased numbers this year. The trends in these two species are somewhat similar, with a large peak in 1998, followed by a “correction.” Because Hermit Thrushes are late migrants, sometimes their capture numbers don’t represent actual numbers — we have much more down time late in the season due to frost, leaves, and cold weather. This probably accounts for the erratic ups-and-downs shown in the graph.

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  1. In order to compare different locations or years that may operate the same number of hours but with more or fewer nets, capture rate is calculated by “net-hours.” One net hour is one 12-meter net open one hour, or two 6-meter nets open one hour, etc. This rate is often expressed per 100 net-hours for more manageable numbers.

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