Friday, October 24, 2008

The finale?

The last week or so has been a drag -- poor weather and poor health has kept me away from the nets for many days. The last couple of weeks of banding area always a challenge. Frosty nights mean frosty nets:
You can see the layer of frost on these closed nets. Often they are actually frozen shut, but even if they can be opened, it's like hanging out a bedsheet:

Not an effective way to catch birds! Nothing can be done but sit it out and wait for it to get warm enough for the frost to clear.

We did have our first Purple Finch of the season last week. Overall, about 80% of the birds we band in fall are young (hatch-year) birds. Young Purple Finches, male and female, have female-like plumage. So it's always cool to get a nice adult male like this one:

Purple Finches really are on the purple side of red -- a dark pink or raspberry color that distinguishes them from House Finches, which are red or orangish-red. Also note that Purple Finches really don't have much streaking on their sides. The abundant streaks of House Finches makes them look "dirty." Once you really get a good look at a Purple Finch, you'll see that it's easy to tell the two species apart. Banders have another clue: House Finches are pretty docile, but Purple Finches BITE!

We also had the last of the Orange-crowed Warblers. Other than Yellow-rumps, these are usually the final warblers to pass through.

Chipping Sparrows are very common on campus. This young bird was in our nets last week. It still has streaky juvenal plumage, especially the streaky cap. (And, no, I didn't spell that wrong. "Juvenile" birds have "juvenal" plumage.)

I've updated the stats on the sidebar again. I hope to be able to get in a few more hours next week as I begin removing the nets for winter. In many cases, I'd leave them up and see if I could extend the season, but a scout group will be coming in to put down landscape fabric and wood chips in the nets lanes. This will greatly reduce the pre-season net lane preparation for the next several years. I'm thrilled about it, so no complaints from me!

After it's all wrapped up, I'll update the stats and point you to the RRBO web site, where I will post a full summary of the fall banding season.

Monday, October 20, 2008

RRBO in the Metro Times

The Metro Times has come out with its annual Best of Detroit results. Readers are polled on their favorite things and places around metro Detroit, and the staff also gives its picks. The Metro Times picked the UM-Dearborn natural area as The Best Urban Getaway for 2008. The write-up notes:
"More than 250 bird species have been recorded by the Rouge River Bird Observatory, housed at the center. The observatory studies the role of this natural-amid-urban area as a stopover for migrating birds."
Many thanks to the Metro Times writers for the shout-out!

Saturday, October 18, 2008

Week #9 in review

The composition of species indicates that we are in the final stretch for fall banding, and winter is knocking on our door. This week, our first American Tree Sparrow was banded.

And a favorite winter visitor, a Red-breasted Nuthatch. On campus, there aren't many conifers; in the banding area there are just two scraggly cedars. So it's always a treat to catch one of these cuties.

Of all the species we band, none is as indignant as the Tufted Titmouse. From the minute you start taking them out of the net to the second you let one go, they let you know how thoroughly offended they are at this whole banding process. There is a continuous barage of weird sounds, from evil hissing to extremely high-pitched, piercing whistles. Titmouse can make these noises while simultaneously pecking and biting. They are just 20 grams of pissed-off bird!

We banded four titmice this week (3 in one net). That's kind of unusual for us.

As you can see from the running stats on the sidebar, we are still well under the average capture rate for the season. Things have been picking up -- this week our capture rate was 48.7 birds per hundred net hours -- but still quite dismal. In general, this is probably not too surprising given the trends of the last couple of years. Following the terrible deep freeze of the spring of 2007, we had a poor banding season last fall, and this spring migration had the lowest numbers since I've been counting here on campus.

I've heard from some observers that did not see this trend. Typically, they have gone birding during peak times at known migrant traps such as Crane Creek in Ohio, or Tawas Point or Whitefish Point in Michigan. This doesn't surprise me much -- coastal areas and migrant traps can be expected to congregate birds that may be reluctant to cross, or have just passed over, an ecological barrier. This is, of course, why people like to bird at these places and why bird observatories and banding stations are often located at these sites. Migration ecology experts theorize that inland sites, such as the UMD campus, present a more accurate representation of stopover behavior, because birds use inland sites only if appropriate resources are available.

This brings up the interesting point that our monitoring efforts may produce results unbiased by the "migrant trap effect". Certainly it offers a contrast to other data. Sure, I am sometimes disappointed by the low numbers of banded birds. But I'm not in any sort of competition here. I always keep in mind that low data or no data are themselves valid results, and tell their own important story.

Thursday, October 9, 2008

Week #8 in review

Here was the star of this week, an adult male Cooper's Hawk.

We don't catch many hawks, since the nets we use are really designed for small songbirds. Their mesh size is too small for hawks like this to really get struck in. Male Sharp-shinned Hawks are pretty small, and that's what we'd typically catch. This was only our second Coop. And it was a first for RRBO veteran bird bander Beth Johnson.

Sparrow season continues. The last to arrive are Fox Sparrows, but they are worth waiting for. Very handsome.

And while the majority of the warblers being banded now are Yellow-rumps, Orange-crowned Warblers have been coming through, and there are still several Nashville Warblers each week. This male Black-throated Blue Warbler was another straggler.

American Robins are also common now. Bander Darrin O'Brien's purple-stained fingers attest to the fruity diet of some robins he'd just handled!

Things have picked up the last couple of weeks, but are still not as busy as we might expect this time of year. If our modestly increased pace continues, we will at least not end up with the worst fall season in our history, but alas we will not make it to our 30,000th bird banded as I had hoped. That milestone will have to wait until next year.

Don't forget to check out our special offer for fall RRBO donors!

Saturday, October 4, 2008

Week #7 in review

Last week I mentioned we had banded our second Connecticut Warbler of the season, but I hadn't downloaded the photos yet. Here we go:

Connecticut Warbler #2

And we banded another last Sunday. Unfortunately, nearly everybody from the Detroit Audubon field trip had already departed for the day and missed it! Of course, it got a mug shot, too.

Connecticut Warbler #3

White-throated Sparrows arrived in good numbers this week. This species can be quite variable in plumage. There are two color morphs, one with brown and pale tan head stripes, and the other with black and white stripes. Some young birds can be really dull and dirty looking, and even have some breast streaking, like this one.

The adult below was a lot nicer looking. There is a subtle difference in the eye color of young and adult White-throated Sparrows. Young ones have gray-brown eyes, adults are a richer reddish brown color. This is best seen in bright light.

And to round off the sparrow gallery are these White-crowned Sparrows. Unlike White-throats, the difference in the head stripe color is strictly age-related, with the young birds having tan stripes, and the adults black and white.

Young (hatching year) White-crowned Sparrow

Adult (after hatching year) White-crowned Sparrow

So far, I've had a modest number of recaptures of passage migrants (those species that only use this area during migration, but don't breed or winter here). The species recaptures so far have been Gray-cheeked Thrush, Swainson's Thrush, Black-throated Blue Warbler, Blackpoll Warbler, American Redstart, Ovenbird, and Common Yellowthroat. Of the 12 individuals, all but 3 gained weight, the average being 7% of their original body mass. As a general rule of thumb, birds need to gain 3 to 5% to make another night's flight. Our analyses have indicated that the majority of individual birds do gain weight on stopver here at UM-Dearborn, but this varies widely between species. Most thrushes, for instance, gain a lot of weight. White-throated Sparrows overall tend to lose weight. This focus of our research will be discussed in upcoming posts.