European Goldfinch: established in the U.S.?

Update: This paper has been published! It's open access so you can read online or download the PDF; click on title below -

Craves, J.A., and N.M. Anich. 2023. ­­­Status and distribution of an introduced population of European Goldfinches (Carduelis carduelis) in the western Great Lakes region of North America. Neobiota 81:129-155. doi: 10.3897/neobiota.81.97736

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.

Update on European Goldfinches

Update: This paper has been published! It's open access so you can read online or download the PDF; click on title below -

Craves, J.A., and N.M. Anich. 2023. ­­­Status and distribution of an introduced population of European Goldfinches (Carduelis carduelis) in the western Great Lakes region of North America. Neobiota 81:129-155. doi: 10.3897/neobiota.81.97736

--

People continue to leave me comments on my previous posts about European Goldfinches in the U.S. (see list of posts below). I am still keeping track, especially of breeding records. In addition to accumulating reports from proactive observers, I also periodically look through birding listservs and eBird records. Unfortunately, any Illinois records put in eBird are filtered out of public view, but the state reviewer is working on changing this. Even so, I still have over 50 records of well over 100 birds from the past few years just in southern Wisconsin and northern Illinois alone.

Here's a map from a previous post, showing the Wisconsin and Illinois counties highlighted in red where the bulk of reports of European Goldfinch come from.

In a previous post, I documented nesting in Waukegan, Illinois, which is in Lake County. Later, I found a report online of a family of European Goldfinches at Waukegan Beach on 13 August 2009, consisting of five birds: two adults, and two juveniles, with the fifth bird likely also a juvenile. The observer posted this photo on Flickr. The day before the photo was taken, another observer saw a minimum of 13 European Goldfinches foraging in a weedy area in what appeared to be two to four family groups in an area just adjacent to Waukegan Beach.

In 2011, European Goldfinches were reported nest-building at Waukegan Beach. A report in April 2012, just a couple weeks ago, also mentioned them gathering nest material. So it seems a breeding population is well-established in the Waukegan area.

These may not be the first European Goldfinches to have nested in Illinois, as there was also a report of birds nest building at Montrose Point in Chicago, Cook County as early as 2003.

In Wisconsin, the breeding population seems centered in the Racine area of Racine County. That is around 25 miles north of Waukegan. My previous post documented a juvenile in 2009 in the Racine suburb of Mt. Pleasant. Subsequently, I received a report in late July 2009: the Scheefs in suburban Racine reported on a juvenile showing up at their feeders shown in this post.

I also heard from Sarah Anspaugh of Racine, who took the photo below of a European Goldfinch family. A pair showed up at her feeder on 13 May 2009, appeared periodically through June, and on 8 July 8 there were 2 juveniles with them.


Jane Scheef of Racine contacted me again in 2010. The pair in her neighborhood arrived at her feeder on 29 June with 5 young in tow, shown in the photo below.



I think that an eBird report of six to eight coming to a feeder in Racine in late winter 2011 may be the same residence. The largest flock I have heard about was that of 30 on 4 December 2011, also in Racine (I think this checklist is the exact location).

Finally, in between Waukegan, IL and Racine, WI is Kenosha, WI, where a correspondent named Donna has had at least one pair of European Goldfinches at her feeders. In June 2011, she photographed them with three young. She recently wrote me that a pair is currently coming to her feeders.

Unlike American Goldfinches, European Goldfinches typically nest in May and June, so be on the lookout and keep sending those reports.

Here are my other posts:

• European Goldfinch: Established in the U.S.? -- 1/21/2009, includes link to my paper in North American Birds
• European Goldfinch update -- 6/24/2009 -- includes photos of juvenile birds that nested in Waukegan, IL
• More European Goldfinches -- 7/23/2009 -- more young'uns, these in Racine Co., WI

European Goldfinch update

Update: This paper has been published! It's open access so you can read online or download the PDF; click on title below -

Craves, J.A., and N.M. Anich. 2023. ­­­Status and distribution of an introduced population of European Goldfinches (Carduelis carduelis) in the western Great Lakes region of North America. Neobiota 81:129-155. doi: 10.3897/neobiota.81.97736

Earlier this year, I posted about a paper I wrote summarizing sightings of European Goldfinches (Carduelis carduelis) in the Midwest. A population is apparently established in northeastern Illinois and southeastern Wisconsin.

I just received a report from a resident of Waukegan, IL, about 10 miles from the Wisconsin border. She hosted four adult European Goldfinches last year, and up to eight this spring. On 20 June, she reported an adult with two youngsters in her yard. On 22 June, she saw four young with two adults, and sent these photos.

I've had a handful of reports of nesting European Goldfinches from Illinois or Wisconsin since 2003, but only two with photo documentation. This Waukegan report is the most detailed and the first definitive report away from the "epicenter" of sightings in McHenry Co., IL, which is about 40 miles west of Waukegan.

As they do in their native range, European Goldfinch nest in May and June, which is earlier than American Goldfinch. However, in Europe and Asia, they raise two broods, sometimes three, so nesting in the two species here in North America could overlap.


As you can see, the juveniles are superficially like dull or female American Goldfinch, but any good look will reveal the jet black wings with large yellow wing patches. Young European Goldfinch lack the red on the face and the head pattern of the adults. The Waukegan host will be watching to see when the young birds acquire the red faces of adults, (should they continue to come to her feeders) which I expect to happen sometime in the fall.

I welcome further reports of nesting European Goldfinches!

See also this update from July 2009.

Photos copyright E. Powell. Used with permission.

European Goldfinches: 20 year data summary underway

Update: This paper has been published! It's open access so you can read online or download the PDF; click on title below -

Craves, J.A., and N.M. Anich. 2023. ­­­Status and distribution of an introduced population of European Goldfinches (Carduelis carduelis) in the western Great Lakes region of North America. Neobiota 81:129-155. doi: 10.3897/neobiota.81.97736

 ---

European Goldfinches have now been nesting in northern Illinois and southern Wisconsin for over 15 years. With the completion of the latest Wisconsin Breeding Bird Atlas, it's time to summarize the distribution and breeding information on this species.  

As of December 2021, I am working on a paper that will briefly cover the history of this species in North America with more detail of the status over the past 20 years; where this species is currently found and where it has nested recently; a focus on the origins, spread, and distribution in the Great Lakes states; breeding phenology and ecology in this region; and as much as can be gleaned about the ecology and potential impacts of the establishment of European Goldfinches in North America.
Nick Anich, coordinator of the Wisconsin Breeding Bird Atlas, and I are collaborating on this part of the project. We've met with several other researchers who are interested in looking at population genetics and morphology of European Goldfinches across the continent.

Around 2001-2004, a number of other European bird species were reported from the western Great Lakes area (scroll down on this page for details). Of those, Great Tit (Parus major) is still nesting in Wisconsin. I believe a couple of other species may still be present and reproducing, but they are much more difficult to quickly identify and a status update on them will have to be a future project, although I still collect records.

The initial task with the goldfinch project is just to attempt to compile a database of sightings for the past 20 years or so and cull important information from this. This data is coming from multiple sources, including hundreds of sightings provided directly to me from people responding to posts on these pages and the former Rouge River Bird Observatory web site. I'm indebted to these people, because they provide the backbone of early sightings that were never reported elsewhere. 

The majority of more recent records come from eBird, but because European Goldfinches are non-native and therefore not "countable" on birders' lists, they have not been adequately reported. This has been further compounded by differential treatment of non-native species in each state. We are working with all reports that have been submitted to eBird (including those not showing in the public maps and output), but believe there is a substantial amount of data that, unfortunately, is lost to history. The eBird data we do have is challenging to work with -- for example, of the 6300+ eBird records we have, many are duplicates of the same bird, sometimes the same day or multiple days at one location (which may be recorded in different ways by different observers).

I am no longer actively collecting data. However, if you have any sightings in North America from 1999-2021 that have not been entered into eBird, please do so. Even if they do not appear in the public output, we will see them when we access the eBird database, or they will be available to future researchers. If you have further questions or information, or information on other European bird species (list below) you can contact me via the form near the bottom of the right sidebar --> 

You can read a great deal of background on the European Birds in the Midwest page. I've included this post at the beginning of that page as many people land there first, so scroll down a bit for the earlier information.

Other posts on Net Results about European Goldfinches:

European Goldfinch: Established in the U.S.? -- Jan 2009
European Goldfinch update -- nesting in Illinois, Jun 2009
More European Goldfinches -- nesting in Wisconsin, Jul 2009
Update on European Goldfinches -- Apr 2012

More European Goldfinches

Update: This paper has been published! It's open access so you can read online or download the PDF; click on title below -

Craves, J.A., and N.M. Anich. 2023. ­­­Status and distribution of an introduced population of European Goldfinches (Carduelis carduelis) in the western Great Lakes region of North America. Neobiota 81:129-155. doi: 10.3897/neobiota.81.97736

On the heels of my recent posting on a report of a family of European Goldfinches in Waukegan, Illinois comes another report with photo documentation of a juvenile "EUGO". This one is from a the Racine, Wisconsin suburb of Mt. Pleasant, about 25 miles north of Waukegan.

An adult was first seen at the observer's feeder in June, although neighbors had seen multiple EUGOs at their feeder (and I have many reports from the Racine area). On 9 and 22 July, a young bird showed up, at times with an adult, and these were among the photos obtained:

Juvenile European Goldfinch, Mt. Pleasant, WI.

Left, adult European Goldfinch. On the right, the juvenile European Goldfinch on the left side of the sock, and an American Goldfinch on the right side.

Here is a map of the southern end of Lake Michigan; the counties reporting the most European Goldfinches are outlined in red. McHenry County in northern Illinois is the suspected point of release of many of the birds.


Keep those reports coming.

Photos copyright J. Scheef. Used with permission.

European Goldfinch paper: preprint available

Update: This paper has been published! It's open access so you can read online or download the PDF; click on title below -

Craves, J.A., and N.M. Anich. 2023. ­­­Status and distribution of an introduced population of European Goldfinches (Carduelis carduelis) in the western Great Lakes region of North America. Neobiota 81:129-155. doi: 10.3897/neobiota.81.97736

 

At long last, the paper on the population of European Goldfinches in the western Great Lakes region is complete, and has been submitted to the journal NeoBiota. In the paper, my collaborator Nick Anich of the Wisconsin Department of Natural Resources and I covered a brief history of the times and places where this species has been introduced around the world, and their distribution in North America over the past 20 years. Focusing on the western Great Lakes region, we describe where they are successfully nesting, where they may have come from (both countries of origin and domestic importers), and some additional information on nesting ecology, natural foods, potential impacts, and suggestions for future monitoring.

The manuscript still has to go through peer-review, but the preprint is available at the publisher's website. Here is the abstract:

Monitoring introduced species is important because of possible effects on native species and ecosystems. Here, we report on European Goldfinch observations from North America between 2001–2021, focusing on a population in the western Great Lakes region. We compiled over 7000 records of European Goldfinches from multiple sources for this time period. Over 3300 records were from the western Great Lakes region. We believe the primary founding event of this population to be release or escape from a cage bird importer in northern Illinois.  European Goldfinches were initially reported widely in the region, but over time birds were most consistently reported between Milwaukee, Wisconsin and Chicago, Illinois. They have been breeding in this area continuously since 2003, are currently present in numbers that have established them as part of the local avifauna, and show evidence of a recent increase in numbers.  More study is needed on this population of European Goldfinches, including their ecology, their potentially increasing range and population, and an evaluation of the potential for impacts on native ecosystems.

Craves J, Anich N (2022) ­­­Status and distribution of an introduced population of European Goldfinches (Carduelis carduelis) in the western Great Lakes region of North America. ARPHA Preprints. https://doi.org/10.3897/arphapreprints.e90813

We acknowledge the many people who contributed or reported observations of European Goldfinches over the years -- thank you!

Fall banding: Week #5 in review

This past week things picked up nicely, bringing us what we expect at this point in migration, a nice diversity and good numbers of birds. We missed a day and a half to rain, but banded 183 new birds and handled 31 recaptures, one of which was a Gray Catbird first banded in 2005. There were 37 species, including 15 species of warblers. We are already at or above our fall season average for Black-throated Blue, Blackpoll, Magnolia, and Nashville Warblers, and American Redstart. The most special warbler of the week was this great young male Hooded Warbler. It is the third ever banded for RRBO, and only the second fall record for Dearborn.

We banded two other unusual birds this week. The first was this dark, heavily marked form of the Veery, matching descriptions of the Newfoundland race.

The other surprise was this European Goldfinch. RRBO has done a lot of research on this species. While not a first for Dearborn, it was interesting nonetheless. This individual was not a wild vagrant from Europe, but an escaped or released cage bird.

We banded four species of vireos this week: Warbling, Red-eyed (we're already at our fall average), Philadelphia, and Blue-headed. I think Warbling Vireos look angry, while Philadelphia Vireos, like the one below, look "cute."

Blue-headed Vireos are one of my favorite species. We don't catch a lot of them, and they are just so handsome.


Actually, photographing any vireo is a challenge. They are all fuss and squirm. My general rule is that I only take a few quick shots of any bird I handle. If I can't get a good one, my loss. I don't have a lot of great vireo portraits because they are so uncooperative, most pictures end up like the next two.

We've been getting a lot of great samples for our study of what fruits birds eat in the fall at our site. This is the fourth year I've collected droppings from Catharus thrushes. I often find (in addition to the seeds, pulp, and berry skins I'm looking for) small hard parts of insects. Most often it is sections of millipedes, parts of beetles, and, frequently, ant heads. I guess thrushes aren't particular about the type of Hymenoptera they eat -- this head of an Eastern Yellowjacket (Vespula maculifrons) stared out at me from a sample provided by a Gray-cheeked Thrush.

Dana Wloch, one of my undergraduate research associates, is in charge of identifying and categorizing the samples from all other bird species. This is mostly robins and catbirds, but this week we've gotten samples from Rose-breasted Grosbeak and Red-eyed Vireos. Seems like yellowjackets are on the menu, as this head and a couple legs came from one of the vireos.

I've been asked how birds manage to eat bees and wasps without getting stung. Usually, they wipe the insect on a branch or the ground and get rid of the stinger. A more lengthy answer can be found in my February 2007 column in Birder's World magazine.

And another new bander has joined the team. Welcome to Sara Cole, a senior at Wayne State University. Here is Dana showing Sara how to age and sex her first bird, a Common Grackle.

It was a fun week. More birds coming up.

Dearborn Passenger Pigeons: Then and Now

I recently became aware of an interesting website: Project Passenger Pigeon.  Since 2014 marks the 100-year anniversary of the extinction of Passenger Pigeons, a group based out of the Chicago Academy of Science is using its story as an opportunity to educate people about extinction, habitat preservation, and species conservation.

The web site is very extensive. Among many other topics, it provides a great deal of information on Passenger Pigeons in various states, including a good account of the bird's history in Michigan. I'd like to add to this historical account because Dearborn figures in Michigan's Passenger Pigeon history, as I found out when I was researching my book, "The Birds of Dearborn: An Annotated Checklist."

On September 14, 1898, a Passenger Pigeon, one of three birds observed, was collected by Frank Clements. The first authoritative book on Michigan ornithology was Michigan Bird Life by W. B. Barrows, published in 1912. That book reports the location of these pigeons as "Delray" which is an area in southwest Detroit. Further digging has revealed that this location is not correct.

In a note published in the short-lived Bulletin of the Michigan Ornithological Club, Philip Moody -- who was with Clements at the time of collection -- identified the location as "Chestnut Ridge." My previous research indicated that this was a large woodlot owned by the Chestnut Ridge Land Co., also marked on some maps as Private Claim 31, on the southwest side of the Rouge River near what is now Rotunda Drive. Several years later, J. C. Wood, another prolific collector of birds in Wayne County, clarified with Moody the precise location: Private Claim 660, Dearborn Township.

Thanks to modern technology, we can look at the 1876 historic map of Dearborn Township overlaid with today's Google Maps (you can zoom and adjust transparency) and see that PC660 stretched from the Rouge River southwest to just past the intersection of Rotunda and Pelham; most of the area is now Greenfield Village. At the time of Wood's 1910 note, the specimen was in Toronto in the collection of James Fleming, a well-known Canadian ornithologist. This specimen is currently at the Royal Ontario Museum in Toronto, and the locality is listed (incorrectly) as "Delray, Detroit."

The Dearborn/Delray bird is often cited as being the last collected in the state, although a search of the ORNIS database reveals a specimen housed in the Yale University Peabody Museum from Bay County in January 1906. Fleming's careful research as well as many other references fail to mention this bird or other wild birds in our region past 1900 or so; perhaps this one was a captive bird. Thus, the Dearborn bird is generally considered the last wild Passenger Pigeon collected in Michigan, and one of the last in the region.

The Project Passenger Pigeon web site also lists all the known specimens of this species, and includes 11 locations in Michigan. I will add one more: right here in the University of Michigan-Dearborn's Environmental Interpretive Center.

The pigeon is in a large vintage Edwardian-type glass case, with an unlikely assortment of stuffed specimens of many other birds.

The case was given to the former director of the EIC, Orin Gelderloos, well over 20 years ago. It is not on public display, but is still housed here in the EIC.

The Passenger Pigeon is on the bottom of the case. A Blue Jay perched above it gives some idea of the size of this large bird.

Details on the age of the case -- which if not Victorian-era is certainly of that style -- or the origin of the birds in the case are not indicated on the case and remain a bit of a mystery. The bird species in the case are all native to Michigan with the exception of the European Goldfinch in the upper center (although this species was released in the Dearborn area by Henry Ford a hundred years ago, that flock did not persist).

Whatever its provenance, the Passenger Pigeon in the case reminds us of Dearborn's place in the sad history of this species.

References:

Barrows, W.B. 1912. Michigan Bird Life. Michigan Agricultural College, Lansing.

Fleming, J. H. 1907. On the disappearance of the Passenger Pigeon. Ottawa Naturalist 20: 236-237.

Moody, P. E. 1903. A recent record of the wild pigeon. Bulletin of the Michigan Ornithological Club 4:81.

Wood, J. C. 1910. The last passenger pigeons in Wayne County, Michigan. Auk 27:208. (PDF here)

Winter Bird Population Survey 2016-2017

The 25th year of RRBO's Winter Bird Population Survey was completed in February.

It was another mild winter. It began rather snowy with temperatures close to average, but January and February saw less snow and temperatures well above normal. Surveys were conducted on 16 days (previous mean 14) with 26.5 hours total (mean is 27.7). For the third year, I was unable to survey anywhere along the Rouge River from Fair Lane Estate south due to it being fenced off for riverbank restoration.

A total of 41 species was two above the previous 24-year mean. Two new species for the survey were recorded: Field Sparrow and the female Pileated Woodpecker that has been present on campus since fall. These bring the cumulative total for the survey to 79 species.

Fruit-eating birds were scarce again. Robins were in low numbers. No Hermit Thrushes, Cedar Waxwings, or Yellow-rumped Warblers were recorded. These latter 3 species have become more and more scarce the last 5 or so years. Because they typically occur in fairly low numbers, I have not yet worked with their data. But the trends with robins might shed some light (see below).

Now that we are at the 25 year mark, I thought I would provide a little summary data and analysis.

Twenty species have been found every year: Canada Goose, Mallard, Red-tailed Hawk, Mourning Dove, Red-bellied Woodpecker, Downy Woodpecker, Hairy Woodpecker, Blue Jay, American Crow, Black-capped Chickadee, White-breasted Nuthatch, Brown Creeper, American Robin, European Starling, American Tree Sparrow, Dark-eyed Junco, Northern Cardinal, House Finch, American Goldfinch, and House Sparrow. Five more were found on 24 counts: Cooper's Hawk,  Ring-billed Gull, Tufted Titmouse, Carolina Wren, and Song Sparrow. These 25 species can be considered our core winter residents.

About a third of the species have only been recorded one or two years, and can be considered rarities in winter. Some of the more interesting ones include Northern Shrike (winter 1995-96), Long-eared Owl (2009-10), Rough-legged Hawk (1994-95), and White-winged Crossbill (2008-09).

Population trends take a little more time to work through, so I just did some quick calculations on common species to see if anything popped out. Not much obvious was apparent for most species using the limited analysis* performed. Perhaps the most interesting were the trends for the two most abundant fruit eaters, American Robin and European Starling.

Both species for many years were more or less stable, with increases starting around ten years ago. I suspect this would correlate with increasing average winter temperatures and decreasing snow cover, but I have not yet incorporated weather data into my analyses. Around 2010 (vertical line on graph) both species being to show declines. This was approximately the time when large-scale removal of invasive fruiting tree and shrubs began, which both bird species heavily utilize in winter. This may indicate a pitfall of removing an important food source without concurrent restoration. Indeed, an examination of robin fecal samples from 2009 through 2017 shows a 52% decrease in the proportion of samples containing non-native Common Buckthorn (Rhamnus cathartica) seeds, the first primary target of the eradication effort. A closer look at the fecal samples reveals another unfortunate result of removing a food source without replacing it with something more desirable.

Non-native Callery or Bradford Pear (Pyrus calleryana) and Border Privet (Ligustrum obtusifolium) have become naturalized on campus. Their seeds did not appear in fecal samples until 2013, but have been increasing every year since. These species are generally not favored by birds -- pear fruits are fairly large and mealy, while privets are dry and have large seeds and little pulp. These percentages are modest, but bear in mind that the vast majority of plant species are found in less than 3% of samples; samples are dominated by buckthorn, non-native crabapples, and non-native honeysuckles. The third species in the chart is non-native Oriental Bittersweet (Celastrus orbiculatus). While there is some native American Bittersweet (Celastrus scandens) here, Oriental Bittersweet is far more common. Birds seem to favor Oriental Bittersweet, perhaps because it has slightly smaller fruit and smaller seeds. Seeds of bittersweet have have greatly increased. Robins, at least, appear to be turning to alternative fruits, those that are less desirable or not as common as what has been removed. This creates an undesirable feedback loop: increased consumption will also lead to increased dispersal of these species.

One other bird species appeared to respond to the habitat changes that started in 2010.

Mourning Doves may be increasing due to the substantial clearing of the understory.

Over the past 25 years, two other events had an influence on bird population. One was the arrival of West Nile Virus in 2001 (vertical line in graph below). I have shown the dramatic decline in American Crows before, and they have yet to recover.

Blue Jays are related and also known to have been impacted by the virus. Their populations appear to have rebounded nicely.

Finally, the Emerald Ash Borer was detected here around 2002, and all our ash trees died within a few years.

While the modest increases might be due to extra food for woodpeckers in dead and dying trees, I don't think the data here indicate that the beetles had much of an effect on woodpecker populations. It might be due to methodology, but since "housing" is often the limiting factor for cavity nesters and the ash trees tended to fall over shortly after death and therefore did not supply more cavities, I think the overall impact on woodpecker numbers was modest.

---

*Notes on methods: I looked at species seen every year that had an average of 5 or more individuals seen per survey day; I excluded waterfowl and added American Crow and Red-bellied Woodpecker. I used birds per survey day rather than raw numbers or hours because for most species that provided the strongest correlation. To smooth out data I used a 3-year moving average, which is why the graphs begin in 1996 rather than 1993. When I work on a full analysis, I will be more thorough and provide more details on methods, but for the purposes of this post, these methods should suffice.

Winter Bird Population Survey 2011-2012

The 20th year of RRBO's Winter Bird Population Survey has been completed. Over the 20 December to 20 February survey period, 39 species were tallied. The previous annual average number of species is 38. We added two species this year. The first was Gray Catbird. I had two on the first count day, 20 December 2011. I was standing and looking at one while I heard another calling. We have only one previous winter record of catbird in Dearborn, and none from campus, so this was quite notable. Single catbirds were reported by other observers several times over the winter. The final observation was by me on 27 January 2012 -- and the bird I saw that day was banded. The bird I was looking at on 20 December was not, and other observers didn't look for bands.

The other new species was a Pine Warbler was visiting the EIC suet feeders on 26 December. This was the second Dearborn and first campus winter record. This brings our cumulative total over the years to 72 species. It's amazing that after 20 years, new species can still be added to this count, but in fact we have added at least one new species every year except 2006-2007. Here is a quick-and-dirty graph of the accumulation of species.

 

I always check all the tangles along my route, and this year was rewarded twice with a Northern Saw-whet Owl. This may have been one or two birds, as the spots were different. I suspect it (they?) was just passing through, as I looked in the same spots every time, but it was only present in late January.

As for misses, Cedar Waxwing was not seen this year, only the fourth year it has been missed over 20 years. Although Pine Siskins and Common Redpolls were recorded several times over the period elsewhere in Dearborn, we did not have any sightings on campus.

American Crow in this immediate area continues to be nearly absent. You can look at last year's post for the story of the precipitous decline and lack of recovery since West Nile Virus (WNV) entered our region. This year I had a single crow fly over on three occasions, all in February when they begin to move around a bit. 

There have been 21 species that have been recorded all 20 years on the WBPS, listed below. Those in italics have also been recorded on over 95% of the 278 individual surveys completed over those years: 

Canada Goose, Mallard, Red-tailed Hawk, Mourning Dove, Red-bellied Woodpecker, Downy Woodpecker, Hairy Woodpecker, Northern Flicker, Blue Jay, American Crow, Black-capped Chickadee (missed on only a single survey in 20 years), White-breasted Nuthatch, Brown Creeper, American Robin, European Starling, American Tree Sparrow, Dark-eyed Junco, Northern Cardinal, House Finch, American Goldfinch, and House Sparrow.

Let's return to the American Crow again. Although Crows were recorded every year, prior to West Nile Virus, they were recorded on nearly every survey -- in the years 1993-2002, they were present on 97.4% of the surveys. In the years 2003-2012, they have been present on only 24.8% of the surveys. A couple of years, I only recorded them on one day.

This tidbit shows the value of this type of long-term data set for monitoring resident birds. It's critical to have programs like this in place, ready to provide "before" data when some unanticipated natural event occurs, including disease, or to see how bird populations respond to more gradual environmental changes.

So while the crow situation is very sad, it has provided me with motivation to get out there and count. One thing you need to know...I hate being out in cold weather. Of these 278 surveys, probably 270 were awfully routine. But the analyzed results will be worth even more than the sum of all the parts, and I'll be working on a complete summary of the Winter Bird Population Survey now that 20 years have been completed.