Wednesday, January 21, 2009

European Goldfinch: established in the U.S.?

Important note: Although RRBO has ceased operations, I am still collecting data. Please see this page for the latest update. 

In the fall of 2002, Ford Motor Company planted sunflowers on a 20-acre lot they owned at Hubbard and the Southfield Freeway (M-39) service drive, near their world headquarters. Ford has continued to plant sunflowers, sorghum, and/or a wildflower mix on up to 10 properties scattered across Dearborn. 

The fields have always attracted a lot of birds -- I wrote about the numbers seen on this year's Christmas Bird Count. The very first winter the original field hosted an unusual bird: a European Goldfinch (Carduelis carduelis), a bird not native to North America. European Goldfinches are common in the pet trade, and it's not too unusual to hear about sightings of escaped or released pets. Unlike members of the parrot family, European Goldfinches are very hardy and can survive northern winters. The sighting occurred during a time when I had been hearing more and more reports of European Goldfinch sightings, especially in the Chicago area. Curious, I posted a page on the RRBO web site requesting sightings from the upper Midwest. I also kept my eyes on the various Internet birding lists and regional publications.

That there were a lot of European Goldfinches out there readily became apparent. I compiled over 400 reports, of which 298 were from Illinois, Wisconsin, Indiana, and Michigan. There was a clear concentration in southern Wisconsin and northern Illinois, a pattern of radiation from the "epicenter" that was more pronounced north than south, and a smattering of reports over the rest of the four states.

It is believed that the bulk of these European Goldfinches -- as well as a handful of other European cage bird species that were reported in the same areas -- originated with a bird importer in the greater Chicago area. From a number of independent reports I received, this importer had apparently deliberately released these species on more than one occasion over time. Believe it or not, as long as the birds are legally imported, there is no federal law prohibiting their release, even if they are not native.

Since 2003, there have been reports of nesting European Goldfinches in northern Illinois. They may also be nesting in southern Wisconsin. Great Tits (Parus major), another one of the species involved in the alleged releases, have also nested in southern Wisconsin and northern Illinois! European Goldfinches nest earlier in the year than American Goldfinches and appear to be ecologically benign, although non-native species frequently end up having unanticipated impacts on ecosystems. Whether the breeding population will grow and persist is not known. In the early part of the 20th century, there were a couple of established colonies in New York, founded by deliberate releases. They eventually died out. However, the proliferation of non-native plant species -- many of which are the natural foods of European Goldfinch -- may prove to be a boon for the species this time around.

I don't believe the majority of the Michigan sightings (or the many Ontario reports I've gotten) of European Goldfinches are attributable to same source. The geographic and chronological patterns do not seem to fit. Some are likely just escaped pets. Many others may be deliberately released birds. Some pockets of reports came from areas with higher populations of people that practice eastern religions, which sometimes advocate setting birds free to accrue merit in the afterlife. Employees at my own local pet store, which often carry European Goldfinches for sale, reported to me that these and other cage birds are sometimes purchased by people of various ethnic backgrounds with the intention of releasing them. I presume this is the source of the Dearborn European Goldfinch.

I ended up writing a detailed account of the reports I received, including background on the ecology and history of European Goldfinches in the U.S. and additional information on their future, in a paper that was just published in North American Birds; you can click on the link to download a PDF copy:

Craves, J. A. 2008. Current status of European Goldfinch (Carduelis carduelis) in the western Great Lakes region. North American Birds 62:2-5.


List of updates on this post:

  • June 2009: Nesting European Goldfinch in Illinois.
  • July 2009: Nesting European Goldfinch in Wisconsin.

Photo of European Goldfinch in France by Daniel (ParaScubaSailor) at Flickr under a Creative Commons license.

Tuesday, January 6, 2009

Dearborn CBC

RRBO has been coordinating the Dearborn portion of the Detroit River Christmas Bird Count (CBC) since 1995. The count is held each year on New Year's Day. This year, the 53 species found in Dearborn on count day tied our previous high total. A Wood Duck at the Ford Rouge Plant was a new species for the Dearborn portion of this count. The big news this winter has been the push of White-winged Crossbills into our region. Unfortunately, none were found on count day, but they were found in several locations in the days following the count, so they are added as "count week" birds. This is also a new species, bringing the cumulative species total to 85. Here's a photo of a male crossbill taken by my husband Darrin O'Brien in our east Dearborn back yard on 3 Jan. We were lucky enough to have a flock of 26 crossbills, and a few Pine Siskins, visit the spruce trees.

One of the annual challenges is counting the hoards of birds that hang out at the nine or so sunflower/wildflower fields planted by Ford Motor Company around Dearborn. After trying several strategies, we now devote a single team (usually Darrin and I) to spend most of the day concentrating on getting accurate counts of birds in the fields. This helps prevent double-counting if the birds move from field to field, and allows a team to spend the necessary time to make good estimates on what are sometimes very sizable flocks of sparrows or finches.

This year was made a bit easier, as the largest field, on the south side of Hubbard at Southfield, was not planted this year. Another, at Southfield and Rotunda, was plowed under in fall. Still, we had our work cut out for us. The photo below is the field on the north side of Hubbard at Southfield. I've underlined myself in red! This field had the most birds this year. It took us a long time, but we feel comfortable with our count of over 2400 House Sparrows here. These fields have a lot of benefit to wildlife, but the downside is that they have certainly helped boost the House Sparrow population, which has skyrocketed in the last few years. Our final total of nearly 3500 House Sparrows set a new high record.


Another group of birds that has begun to overwinter in these fields are blackbirds. Last year the Rotunda and Southfield fields had a staggering 1300 Brown-headed Cowbirds. This year the blackbird flock was more modest. Here's about half of them. Most were Red-winged Blackbirds, along with some cowbirds and a single Common Grackle. Raptors have taken advantage of all the small birds in these fields, and once again we have a wintering Merlin here. We had plenty of opportunities to watch it hunt!

If we have time in the afternoon after going through the sunflower fields, Darrin and I hit a few other spots. We had this female American Kestrel dining on a mouse near Miller Road and Wyoming.

It's always nice to have a hot cup of coffee when adding up the numbers back at the EIC on campus. Here I am with Jerry Sadowski (in the Crocs that match the rest of his outfit!), Greg Norwood (in ball cap), and Gary Hutman, all veterans of the Dearborn count. Jerry and Greg are in charge of counting on campus, and Gary covers Rouge Park (in Detroit, but within the larger count circle).
The final story is the continuing saga of the lack of crows since West Nile Virus wiped them out in this area. Up to 2003, it wasn't unusual to count well over 200. That year, we counted 18. Since then, we haven't had more than 8 in any year. Blue Jay numbers, however, have remained pretty constant.

You can view the results of all past Dearborn CBCs on the RRBO web page.

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 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. 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!