A tale of strange tails

Bill deformities and tumors are not the only abnormalities noted in the birds we band here at RRBO. Feather color abnormalities are pretty common, but today I'd like to focus on a rarer plumage oddity: weird tails.

The tail feathers of birds, known as "rectrices" or "rects", help with flight, balance, and often sexual display or as a means of signaling and communication. The songbirds we band at RRBO have pretty standard tails -- usually 6 pairs of generally graduated feathers. Every so often, we find an exception.

The tail below belongs to a young (hatching-year, or HY) White-throated Sparrow banded on 5 October 2008. The central rect on the right side was around 10 mm longer than the other feathers. All the rects were fully grown in, so it wasn't a case of the other feathers having not reached their full length.


Also this fall, we got this HY Carolina Wren with a funny paddle-like extension on the central rect. We first caught it on 25 August. The extension was apparent, but the bird was still undergoing its fall molt. However, it was recaptured several times, including in early October, when this funky paddle was still there.


Notice also the odd lines in some of the feathers that look like breaks, or as if the feather was folded. These types of "growth bars" or "fault bars" can occur if feather growth is interrupted, often by a shortage of food due to drought, extended periods of rain, or other environmental conditions. Usually this slow-down of growth creates a fault bar that appears more like a faded line. The Hermit Thrush below has one of these kinds of fault bars, a rather extreme example. In the thrush, the fault bar is an even line across all the feathers. The only time a bird normally grows all its tail feathers simultaneously is as a nestling, so the presence of a fault bar like this can often be used to help age a young bird (although this same pattern can occur in adults that accidentally lose all their tail feathers).

The Carolina Wren above was not our only paddle-tailed bird. In October 2004, we banded the HY House Wren shown in the next two photos. There are several interesting things about the tail of this bird. Five of its rects had the same kind of paddle-like tip (it was worn off in one of them); these extended about 5 mm past the "normal" ends of the feathers.

All the tail feathers were fully grown in except for the three on the right in the photo below. Any feather that gets pulled out will begin to regrow immediately. Several weeks prior to capture, this wren had lost these three feathers which were now nearly replaced. Note how much fresher and blunt-tipped they are compared to the three feathers on the outer left.

In many species of birds, HY individuals have more pointed outer rects than do adult birds. This is an especially useful tool to help age warblers -- I'll do a post in the future with some better examples of how we use feather shape to help age birds. Finally, note that the wren appears to have one extra tail feather. The tip of the second feather on the left looks split in two, but you can see the feather has only one shaft.

Wrens and sparrows haven't cornered the market on extra tail flourishes. We occasionally capture Cedar Waxwings that not only have those pretty little red waxy tips on their wing feathers (specifically the secondaries, or inner wing feathers), but also on the tips of their rects. I've also heard these waxy tips may occur in rare instances on the outer wing feathers (primaries) or the row of feathers over the wing feathers (greater coverts). The function or purpose of these waxy tips -- wherever they occur -- is not known.

We always keep our eyes peeled for these interesting little oddities.

RRBO in the Dearborn city calendar

That's right, I'm Ms. September.

A few months ago, the city of Dearborn had a contest. Residents were asked to submit short essays on why they loved Dearborn. The authors of winning entries would have their photo taken for the 2009 city calendar.

I wrote about my favorite thing about Dearborn: the great birds here on campus and the Rouge River Bird Observatory! Here is the page out of the new calendar. It features Dana Wloch, yours truly, Greg Norwood, Beth Johnson, and Mike Perrin out on the lakeside trail, and an inset of me holding a flycatcher accompanied by an excerpt from my essay. I'm a bit disheveled, which is typical for me on banding days.


You can see the entire two-page spread by downloading this PDF. This calendar goes out to every household in Dearborn -- great visibility for RRBO!

Recovery -- a rare event!

Since not very many banded birds are re-found away from the place they are banded, the majority of what we learn from banding birds comes from data we gather when we band them, and when we recapture birds on site. Nonetheless, every so often we hear about a recovery of one of our banded birds. These reports come from the USGS Bird Banding Lab, which administers bird banding in the U.S. We just got one this week, and it is quite special!

A Northern Waterthrush banded here on campus on 30 April 2007 was recaptured and released at Cedar Grove Ornithological Station in Sheboygan County, Wisconsin on 21 October 2008. The map below shows the location of Cedar Grove with a red marker, and our location in blue (click to enlarge).

How rare is this? Of the 32 recoveries that have been reported to us since 1992, this is only the 14th to have been reported outside the state of Michigan -- you can view an interactive map of all out of state recoveries here. Typically, these birds are found dead. The most common reason, if one is given, is that the bird has been killed by a cat. This waterthrush is just the third bird that has been captured and released by another bander. The others were a Yellow-rumped Warbler we banded in May 1997 that was recaptured in Tallahassee, Florida in March 1998, and a White-throated Sparrow banded in October 1999 that was recaptured on the Bruce Peninsula in Ontario in April 2006 (not a typo!).

But several more factors make the recovery of this waterthrush even more unusual.

1. The warbler and the sparrow are short-distance migrants, wintering in the U.S. The waterthrush is a long distance migrant. After we banded it, it probably nested in northern Michigan or Canada, then it likely spent the winter somewhere in the West Indies or perhaps Central America (you can view a range map here). Then it went north, nested again, and was headed back south along the western shore of Lake Michigan when it was captured at Cedar Grove.
2. Cedar Grove is a hawk banding station. For over 50 years, raptors have been banded at Cedar Grove, and small songbirds are only captured incidentally!
3. I've banded 167 Northern Waterthrushes during spring migrations, but only one has had a bill deformity...this one! So I happened to have photographs of it, which are below.

This slight deformity apparently did not hinder the bird prior to it being banded. It had a lot of fat, and at 22.1 grams, it was the second heaviest waterthrush RRBO has handled in spring, with the average being 18.0 grams.

Update: I've heard from one of the banders in charge at Cedar Grove. He told me that because they do not really "process" songbirds, the waterthrush was not checked for fat or weighed, nor was any abnormality noted. Bummer. I've caught only a few birds banded by other people (the last one was a Ruby-crowed Kinglet in 2005), but -- perhaps because I'm so astonished that it happens at all -- I give them a really thorough going-over.

The results are in: Fall 2008 banding summary

I have posted the fall 2008 banding summary on the RRBO web site. The numbers on the right sidebar are also updated. Also updated on the RRBO site are tables on the most commonly banded species and all the species banded on campus since 1992.

Just because the banding season is over does not mean I won't continue to post here at Net Results over winter. I have some posts planned on interesting bird tails, more on our thrush research, updates on publications, winter bird survey results, the Christmas Bird Count, and whatever else might unexpectedly come up. Please stay tuned.

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.