Spring banding 2005 took place on 26 days from 15 April to 29 May. An average of 17 nets (12 meter equivalent1)were open an average of 4.6 hours per day. We lost five whole and eight partial days to bad weather or other circumstances — just like last spring. Often our closures were due to wind, but one day it was due to snow.
We banded 366 new birds and had 70 recaptures of 60 species (includes Ruby-throated Hummingbird and House Sparrow, which are not banded). A total of 462 birds were netted (this includes birds released unbanded). Our capture rate was 22.9 birds per 100 net-hours, our second lowest capture rate in 13 spring seasons. Here’s a quick comparison of this year versus previous spring means —
Due to the weather, it was a lackluster season. In fact, some people with a lot of spring migrations behind them said it was the worst in decades. Frontal boundaries blocked northbound migrants during much of the front half of the period. Reports of migrants such as Swainson’s Thrushes still in Texas when they should have already been passing through the upper Midwest at least let us know the birds were out there somewhere. When fair weather finally prevailed, many birds bypassed this area, resulting in good numbers of migrants north of here, but dull birdwatching in this area.
Numbers were down overall, so trend analysis for most species is relatively meaningless. But there were certainly bright spots in spring 2005 banding. Having banded 136 species prior to this season, there isn’t a huge potential for capturing new species here at RRBO. So two new species this spring were definitely highlights.
On 18 April, we banded our first Northern Mockingbird (above). A mockingbird has been present year-round on the other end of campus for about five years. This was a different bird (darker eyes) and one of a number of reports from the region this spring.
On 4 May, RRBO’s first Grasshopper Sparrow was banded. There are only a handful of records for Dearborn, and in general sightings of this state Special Concern species in migration are quite rare. This was an exceptionally bright bird, with lores and shoulder that were much brighter than indicated in this photograph.
It’s always nice to recapture migrant birds. The recapture of passage migrants in the same season is the basis of research on stopover ecology. The recapture of migrant birds that nest here (of which we have over 300 records) between years gives us information on site fidelity. Much, much rarer is the recapture of passage migrants between years, and this year we had two such recordss.
On 15 April, White-throated Sparrow originally banded here on 14 April 2003 was recaptured. On 27 April, I recaptured a Dark-eyed Junco that I had originally banded on 14 April 2004. Both of these species winter here, so they may represent wintering birds that I caught during migration, but still, they were a special surprise.
On 22 April, I netted a banded bird that represented and even more rare event. It was a Ruby-crowned Kinglet that had originally been banded on 23 October 2003 in Toronto. To catch someone else’s bird is rare, that bird being a kinglet is even more unusual. You can read all about this special kinglet here.
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- 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. ↩