Monday, December 29, 2008

Five years of Christmas Bird Counts at Humbug

It's hard to believe that I have been doing bird surveys at the Humbug Marsh Unit of the Detroit River International Wildlife Refuge (DRIWR, map) for five years. The Refuge was established in 2001 and includes a patchwork of properties along 18 miles of the lower Detroit River. The 410-acre Humbug Marsh unit, straddling Trenton and Gibraltar, was acquired in 2003 after a lengthy battle with developers. It represents the last mile of undeveloped land on the U.S. mainland side of the Detroit River.

RRBO's partnership with the U.S. Fish & Wildlife Service and the Refuge began in 2004. Although this area is within the Rockwood Christmas Bird Count (CBC) circle (itself established in 1974), it had never been accessible for bird surveys. Since 2004, RRBO has completed five CBCs at Humbug, as well as two North American Migration Counts, four years of Breeding Bird Atlas work, and two major insect surveys. Summaries and reports are available on the RRBO web site on our DRIWR partnership page.

December 27 was our fifth CBC at Humbug. The day started with very thick fog, making waterfowl counting difficult. Some years, much of the river is frozen and a lot of waterfowl gather in the channel between the mainland and Humbug Island. This water stays open due to the warm discharge from the Trenton Power Plant just upstream. Humbug Island is to the right in the photo below, but the thick fog bank in the center is completely obscuring Grosse Ile.

The day ended up breezy and very balmy, with record-breaking temperatures over 60F. This melted much of the snow we'd had in the previous weeks. In the southern portion of the Refuge, an old road was removed over the summer. In its place: thick muck and deep water-filled ruts covered in sloppy snow and thin ice. We were unable to fully cover this area because we just couldn't walk through it. Still, we had a nice adult male Sharp-shinned Hawk at this spot.

The Humbug Marsh Unit is not yet open to the public. When my husband Darrin O'Brien and I do the CBC there under RRBO's special use permit, we are alone to walk the many acres. There are a few new, formal trails, but usually we just have to follow deer trails or bushwhack. The northernmost part of the property is an old brownfield. It's quite open and in the winter has the fewest birds. Here I am traipsing across the middle of it.

We had 47 species at Humbug for the day. Highlights included two Bald Eagles, a Yellow-bellied Sapsucker, one American Crow (the first on the Humbug count in five years!), three Brown Creepers, one Winter Wren, five Golden-crowned Kinglets, three Hermit Thrushes, an Eastern Towhee, a Purple Finch, and six Rusty Blackbirds. The rusties were also the first we've had there in winter, and we were happy to see them because it is a species in significant decline. We had over 200 American Robins, and over 50 White-throated Sparrows (Humbug is a great site for wintering white-throats). In the midst of it all, I was able to take a short break on one of the new benches along the river.

The cumulative species total for the five years is a respectable 74. Only 16 have been seen all five years, in large part due to the variable mix in waterbirds influenced by river conditions. Unusual species have been Gray Catbird in 2005 and Common Yellowthroat in 2007. The species total will undoubtedly grow as habitat is restored and, when the unit is fully open to the public, the number of participants on the count increases.

January 1 is the date for the Detroit River CBC, which includes Dearborn. I'll post a report on that count next week!

Wednesday, December 10, 2008

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.

Monday, December 8, 2008

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!

Tuesday, November 25, 2008

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.

Most banded birds are found not by other banders, but by regular folks. Here's what you should do if you find a banded bird.

Friday, November 21, 2008

RRBO fall fundraiser on Birder's World blog


In October, I mentioned the special offer we have for our 2008 fall fundraiser: a free one-year gift subscription to Birder's World Magazine for those who make a donation to RRBO of $200 or more if we receive the donation before December 31, 2008. If you are already a subscriber, you can designate a gift.

Birder's World editor Chuck Hagner has written a really cool post at the magazine's blog Field of View, encouraging readers to become RRBO donors via this special offer. Go take a look -- and don't forget to browse the archives. Field of View is full of interesting material, including behind-the-scenes at the magazine, follow ups on articles, and current bird-related news.

This offer ends December 31, so I'll take this opportunity to cajole you again. RRBO is funded entirely by outside donations and grants. This is our main fundraiser. Your donation directly supports our research, is tax deductible (less the retail price of the magazine) , and you get a great magazine!

Download and print a donation form (PDF). If you do donate $200 or more, make sure to download and print the subscription coupon and return it with your donation.

Monday, November 10, 2008

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.

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!

Tuesday, October 7, 2008

RRBO's fall fundraiser

RRBO generally only does one fundraiser a year: a fall donation solicitation letter. If you are on our mailing list, you will have just received it recently (if you are not and would like to be, please send me and email: jac.rrbo AT gmail DOT com).

Many of you know that I am a Contributing Editor to Birder's World Magazine, a fantastic bi-monthly about birds and birding. I write a column in every issue, answering reader questions, and also write regular features. In celebration of my 15th year with the magazine, they are offering a free one-year gift subscription for those who make a donation to RRBO of $200 or more if we receive the donation before December 31, 2008. If you are already a subscriber, you can designate a gift.


For those of you who didn't get this offer in the mail, you can download and print a donation form (PDF). If you do donate $200 or more, make sure to download and print the subscription coupon and return it with your donation.

Remember that your donation (less the retail price of the magazine) is tax deductible -- and if you are a Michigan resident, that also means a 50% tax credit on your state taxes even if you don't itemize (up to a $200 credit). It's a great deal!

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.

Friday, September 26, 2008

Sampling for avian flu

RRBO is in its second full year of sampling birds for avian influenza. There are many different subtypes of "bird flu," most of which are mild "low pathogenic" avian flu viruses which are not dangerous to humans. The type of bird flu often in the news is the highly pathogenic subtype H5N1, which causes high mortality in domestic poultry. It has not been found in migratory songbirds in North America.

The Landbird Monitoring Network of the Americas (LaMNA; RRBO is a charter member) and UCLA's Center for Tropical Research initiated a program in 2006 to learn more about the identity, frequency, and geographic distribution of virus sub-types and strains carried by landbirds. Sampling for avian flu is done at migration monitoring stations such as RRBO, breeding bird stations (Monitoring Avian Production and Survivorship, or MAPS), and wintering bird stations in Latin America (Monitoreo de Sobrevivencia Invernal, or MoSI).

Sampling only takes an extra minute during our banding process. It consists of taking a very tiny sterile swab and sampling cells shed from the intestines at the entrance to the cloaca. The tip of the swab is cut off and placed in a vial of preservative. Two tail feathers are also taken. These can be used in stable isotope analysis, which can give us an idea of where a bird nested. Identifying the breeding areas of birds will help researchers map out where certain strains of virus originate.

Since beginning this project, RRBO has contributed over 300 samples of nearly 50 species. Some are migrants, and some are residents. For many years, we didn't band House Sparrows, beginning during a period when the band size they take (shared by abundant migrants such as thrushes, White-throated, White-crowned, and Song Sparrows) was in short supply. Now they are a valuable species to sample for viruses due to their communal nature and urban haunts. Here's a young male House Sparrow who donated a few cells and two feathers to science.

Sampling will continue through fall here on campus. Then I'll sample at my nearby home to use up any remaining vials -- I'm one of the only banders in the state that provides winter samples to the project.

This is just another way RRBO is making a contribution to a wider understanding of birds in North America. To learn more, check out these links:

Monday, September 22, 2008

Week # 6 in review

While the numbers in the nets continued to be low, there was no decrease in our capture rate although it is still far below average. On the bright side, diversity increased this week, with some of my favorite species being banded. Let's just jump right to a photo salon of the week's highlights.

This is likely the brightest young male Blackburnian Warbler I've ever banded in the fall. Usually they stay pretty high in the trees so I don't catch many of them. They are always a treat.

Last week I was catching female Black-throated Blue Warblers, but this week I had a few males. Beautiful!

I expect to see Philadelphia Vireos between 15 and 25 September...they are pretty prompt and have a tight migration window. I just couldn't capture how fresh and bright the yellow on this bird was, but it was a beauty.

I like the fiesty personality of vireos, and my favorite species is Blue-headed Vireo. I don't catch many of them either, so I was happy to see this one. Isn't it gorgeous?

Another infrequently banded species is Eastern Phoebe. This photo doesn't show the nice, subtle yellowish color of the breast. The picture also makes it look a little more rotund than usual. They say the camera always adds a few pounds...

I banded our second Connecticut Warbler of the fall, today, too, but the photos are still in the camera.

On Sunday, September 28, the Detroit Audubon Society is having a field trip here, and it's open to the public. It will include short walks on the trails, and a look at birds in the hand, should we have some to show. I'll be available to answer all your burning questions. This program is weather permitting: we'll not be banding if it is windy or raining, or threatening rain. Meet on the south patio of the Environmental Interpretive Center (EIC) at 8 AM. Directions to campus and a campus map are linked about halfway down this page on the RRBO web site.

Saturday, September 20, 2008

Week # 5 in review

We are officially off to the slowest start of any fall season in the past 16 years! While we focus on banding and not surveys in the fall, the few times someone has been out to walk the standard route not much has been found, so the shortage is not just limited to the banding area.

Connecticut Warbler (Oporornis agilis), hatching-year female

Connecticut Warblers are very sought-after birds, as they are not very common and notoriously hard to see. We band a fair number of them at RRBO, especially in fall. They are usually young birds, and the dull young females make you wonder what all the fuss is about. This bird was banded on 19 September; another individual bird was seen on a survey the previous day.

Indigo Buntings appeared in our nets this week. The bird above is probably the bluest female Indigo Bunting I have ever banded. This was an adult bird, and male-like coloration in old females is not too unusual -- I see it pretty often in Baltimore Orioles.

Female Black-throated Blue Warblers also don't compare to their gorgeous male counterparts. I don't band a ton of this species, but I did catch four this week -- and they were all females.

Sparrows begin moving through a little later than warblers. Our first Lincoln's Sparrows were banded this week. These are a commonly banded, but rarely seen, species at RRBO.

Savannah Sparrows are another handsome streaky-breasted species, but the streaks are wide and on a clean white breast, rather than fine streaks on a beige "vest."

Rose-breasted Grosbeak (Pheucticus ludovicianus)

One thing you learn early on as a bander: if you catch a grosbeak, give it something besides your fingers to bite! And there's a new face at RRBO who will learn this lesson soon...

I'd like to introduce the newest member of our banding crew, Dana Wloch (and her friend, a Nashville Warbler). Dana is a UMD student with a strong, lifelong interest in birds and wildlife. She tells us that the historical figure she'd most like to have dinner with is Charles Darwin, and the obsolete object she can't seem to part with is a dried up fish given to her as a gift. Dana is refreshingly enthusiastic and a fast learner...I hope she can put up with me us for years to come. Welcome to team RRBO, Dana!

Thursday, September 18, 2008

Bald birds


Joe's comment on my last post reminded me that it's that time of year to address the perennial bald bird issue. It is one of the most frequently asked questions about birds. Northern Cardinals (Cardinalis cardinalis), Blue Jays (Cyanocitta cristata), and Common Grackles (Quiscalus quiscula) are the most common victims of this disturbing-looking feather loss.

There's nothing wrong with most of these birds, despite how bad they look. All birds replace all of their feathers at least once a year, and fall is often the time that North American birds undergo this complete molt. Typically, this molt takes place over a few weeks. But some individuals, unfortunately, lose all the feathers on their head at the same time.

I've often read that ectoparasites such as feather mites are responsible for this condition. I have never found mites on bald birds that I've banded. All birds have some of these mites -- they feed on oils, fungi, and bits of skin, and don't cause feather loss. It would also be unlikely, if not impossible, that they would cause all the feathers in one area to fall out simultaneously. In fact, they typically move to tail and wing feathers -- cooler locations on the bird's body -- in warm weather such as is typical in fall.

There are a couple of other types of mites found on birds, but they have not been found on bald birds. My search for information on quill mites, for instance, didn't even turn up any evidence that they've been found on cardinals or jays. Nor does it make sense that these other mites would cause feather loss on the head but not elsewhere, since birds are not able to remove them easily from anywhere on their bodies via normal preening.

Although the role of mites in bird baldness has not been thoroughly studied, the seasonal and localized nature of the baldness and the fact that it is most common in a relatively limited number of bird species leads me to believe that their presence is coincidental and not causative. That this catastrophic molt is "normal" in at least some individual birds comes from Cornell staffer and former wildlife rehabber Laura Erickson. She was in charge of a Blue Jay in captivity that always lost all the feathers on its head simultaneously once a year -- for the 8 years she had it!

Sometimes bald birds are seen at other times of the year when they would not be expected to be molting. The reason for their feather loss may be different (running into a window, for instance, could cause at least a temporary loss).

Being bald is not harmful to birds, except perhaps in cold or wet weather. Within a few weeks, the feathers will grow back.

For more photos and information, see the Cornell web site. Top photo of a bald cardinal by Jimmy Smith.

Janet Hug from Commerce Twp., MI sends us this photo of an adult male cardinal at her feeder, on the road to refeathering, but still looking pretty shabby.