Thursday, November 15, 2012

Fall 2012 banding season review

Our 21st fall banding season took place on 38 days from 17 August to 25 October. An average of 17 nets (12 meter equivalent*) were open an average of 4.3 hours per day. This is the fewest number of days we have been open in a fall season, as we lost 14 whole days and curtailed many others due to rain, heat, or wind, including the last week or so of the season due to Superstorm Sandy and her winds (see below).

What we band in fall has a lot to do with weather in the preceding seasons, even those in years past. I'll leave aside the amazingly wet spring and very hot summer we had in 2011 -- not that they can't have lingering effects, but the weather in 2012 was unusual enough. 

We started the growing season well ahead of schedule, with an unprecedented March heat wave. I discussed possible effects in this blog post. Then came the extended hot, dry summer. It began with 11 days over 90 degrees by the end of June resulting in an average temperature for the first six months of the year being the warmest on record for Detroit. Record heat in July (13 more days over 90F) and precipitation well below normal created severe drought conditions (D2 on the U.S. Drought Monitor scale). 

Below is a map at roughly the end of the breeding season for many songbirds showing drought conditions throughout North America.

Click here for the original map in detail from the North American Drought Monitor.
Banding begins in mid-August, and while the month was still warmer and drier than average, most of the month's precipitation fell as we began the season. September was cooler (although still slightly above average) and remained drier than normal. October brought two episodes of high winds, one mid-month and the other at the end of the month as a result of Hurricane/superstorm Sandy. This ended our banding season.

We ended up banding just 616 new birds and handling 72 recaptures of 63 species (includes two species released unbanded, Ruby-throated Hummingbird and House Sparrow, and one species, Downy Woodpecker, in which we only had a recapture and no new individuals banded). A total of 725 birds were netted (which includes birds released unbanded). Our capture rate was 27.5 birds per 100 net-hours. Here is how this fall compared with the 20 previous autumn seasons:

Fall 2012 Previous
fall mean
Days open 38 51
New birds 616 1205
Total birds 725 1541
Capture rate 27.5 49.0
Species 63 70

Bold indicates the lowest numbers in our history for fall banding -- we'll give this some analysis in the trends section, below.

The top ten bird species banded this fall (new captures only) were:
  1. American Robin -- 107 (low; previous mean 188)
  2. Song Sparrow -- 37
  3. Blackpoll Warbler -- 36
  4. Gray Catbird -- 32 (new record low; previous mean 138)
  5. American Goldfinch -- 32
  6. Swainson's Thrush -- 30 (low)
  7. Magnolia Warbler -- 27
  8. Hermit Thrush and American Redstart -- 26
  9. White-crowned Sparrow -- 21
Our biggest day was on 16 October, when over 100 birds were banded -- 20% of the total that had been banded up to that point. The next day...just 8 birds! In fact, there were only 4 other days when more than 30 birds were banded.

Let's start out with good news. First, we had our first new species for the banding program in a long while. This handsome male American Kestrel was the first banded on campus by RRBO, and represented the 123rd species banded since 1992.

Connecticut Warblers are always a treat -- especially good-looking adult males like the one below, banded on 19 September.

What started out as a gruesome discovery on 28 September had a happy ending. We captured a Swainson's Thrush that had a piece of straw (hay) impaled through its eyelid and the skin past the ear hole. It was embedded at that point, the skin beginning to grow around it. This must have happened at least several days prior to our catching it, when the bird was foraging in some area with straw strewn about. Amazingly, the eye itself was unharmed, there was no infection, and the bird was in good condition.

Under magnification and in just a few minutes, I snipped off most of the exposed straw, severed it where is crossed the ear, extracted the portion between the ear and eye, and finally snipped it close to the point where it was embedded in the skin. I removed over 30 mm of straw! The bird flew off, hopefully to continue a successful migratory journey without the threat of the straw getting caught on something and ripping the skin or puncturing the eye.

Among the 21 White-crowned Sparrows banded this fall was this candidate that had the clear-lored look of the western "Gambel's" form. However, it has the bill shape and color that lean toward more typical eastern forms. This is the first adult of this type we've banded; for a full discussion and more photos see this page on the RRBO web site.

"Gambel's" White-crowned Sparrow?

The RRBO banding program has focused on bird community composition and various metrics relating to the condition of migrant birds at our site. Thus, overall numbers have not been a main theme for us. Limitations and biases inherent in migration banding cannot be overcome, and much has been published in the literature cautioning against the sole use of banding data to monitor bird population trends. However, it's always interesting to take a look at trends of some species, especially in a year like this with unusual climate events and very low numbers. We just need to take it with a grain of salt.

Of the 25 species of which RRBO has banded over 200 birds, five were banded in greater than average numbers and the rest were below average, when effort was considered*. A half-dozen of these species are among our most commonly banded, and all those were banded in numbers far below normal. Low numbers of a few of them (Hermit Thrush, Song Sparrow, American Goldfinch) could be attributed to the premature ending of the banding season, when I tend to band quite a few of these species. Let's look at the others.

Both Swainson's Thrushes and Gray Catbirds continued a long-term decline in our nets that I wrote about last year. Catbirds in particular I think may be responding to landscape-scale habitat changes being engineered by a burgeoning deer herd.

I'm not sure what to think of the -74% departure from normal of White-throated Sparrows. While they do persist longer in the season here than White-crowned Sparrows (many overwinter), they have been scarce at local feeders as well. This is the first fall season when White-crowns outnumbered White-throats, which are typically banded in three times the numbers. If I had to pick a reason, I would guess that White-throated Sparrows, since they most often feed on the ground, may have had trouble finding leaf-litter invertebrates due to dry conditions. This would be especially true during migration, but it could have impacted them on the nesting grounds as well.

Early in the banding season, I wrote about the lack of young birds being banded. This usually indicates low reproductive productivity. Typically, 81% of the birds we band in fall are young-of-the-year (or hatching-year, HY, birds). This year, just 72% were HY. A look at American Robins, our most commonly-banded species, is instructive.

We've banded nearly 4,000 robins in fall, and roughly three-quarters are HY. This year, the figure was just 46%.

I think this is likely attributable mostly to the drought, as robins rely heavily on leaf litter insects and soil invertebrates (such as worms) to feed their young.

Another interesting metric appeared late in the season. By mid-October, most robins have completed molting -- young birds will have lost their distinctive breast spots and adults will have completed molting their wing feathers. This year that was not the case.

Young robins with breast spots after 10 October:
1992-2011: 2.9%
 Fall 2012: 25%

Adult robins still molting primary feathers after 10 October:
1992-2011: 16.1%
Fall 2012: 25%

This indicates that many robins nested later this season. I expect this was due to re-nesting after lost broods (because of the drought), perhaps additionally influenced or initiated by the mid-August rains.

Finally, while I've already provided the caveat that our banding program is not designed to accurately monitor population trends, I have to look at the overall trend in our capture rate for the last eight fall seasons:

Prior to that, there were ups and downs but our effort and capture rate remained fairly stable. We have been banding in the same location all these years, and strive to keep the vegetation structure at its original stage of succession. This may be an indication that populations of the species we typically band in fall are truly declining, and/or that the landscape surrounding our banding area is changing through urbanization, fragmentation, the interactions of deer and canopy loss due to emerald ash borer, or a combination of these and other factors. The value of long-term data collection is having these trends to look at, even if we are not sure how to interpret them at this time.

Twenty-two individuals of 10 species of passage migrants (those which do not normally nest or winter in this area) were recaptured. Seventy-seven  percent of them maintained or gained mass.

The old man cardinal. More RRBO longevity records here.
We also recaptured 13 birds banded in previous years. The oldest was a male Northern Cardinal first captured as a second-year bird in April 2001, making it 12 years old.

Six Gray Catbirds from the past were recaptured; there were two from 2008 that were both originally captured as adults. A Downy Woodpecker first banded in 2006 as an adult at least three years old was also back again.

Finally, I’d like to thank this year’s banding crew: Shelley Martinez, Mike Sullivan, and Dana Wloch. RRBO couldn’t operate without you!

*In order to compare different locations or years that may operate the same number of hours but with more or fewer nets, capture rate is calculated by "net-hours." One net hour is one 12-meter net open one hour, or two 6-meter nets open one hour, etc. This rate is often expressed per 100 net-hours for more manageable numbers.

*Weather statistics from the National Weather Service.

Monday, October 22, 2012

Our online seed guide

As regular followers know, RRBO's primary research focus is the ecology of fall migrant birds in urban areas, and one of our main project is examining the fall diet of birds at our urban site.

To do this, we collect fecal samples from the birds that we band, and identify and catalog all the seeds we find. We initially compiled a book of photos of seeds from plants known to occur in the area, as well as a large reference series of seeds collected on campus and nearby.  This has enabled us to identify all but 9 out of nearly 6,500 seeds we have collected in fecal samples from 2007 through 2011.

Although our big binder of seeds and photos was handy, we found we also wanted to have other reference material in it. We also found there was a lot of interest in this project from other researchers as well as land managers and homeowners interested in what birds are eating. We conceived an online reference guide that would include all this information in the form of species accounts.

Thanks to support from the Jimmy F. New Foundation and the Michigan Audubon Society, our web site is coming together. You can take a look at the first set of species accounts: Fruit Seeds of Southern Michigan.

The guide provides accounts of plants that produce fleshy, bird-dispersed fruits, with special emphasis on the identification of seeds. It will focus on fall- and summer-fruiting plant species found in southern Michigan, but since many of these species are widespread in North America, it will be useful for a broader region. Both native and non-native species are covered.

The financial support has provided a stipend for UM-Dearborn graduate Dana Wloch to work on the site. As a student, Dana worked for several years collecting and compiling seeds from our banded birds under two independent research projects. As the "Number 2 of Number 2" she is uniquely qualified for this task, and I'm grateful for her help and work on the web site, as well as sorting through, identifying, and compiling all the seeds pooped out by every species except the Catharus thrushes for the fourth year in a row.

Take a look at our site. It's a work in progress, so there will be many more species added, revisions to the existing accounts, and the bibliography and resource pages will be completed.

Thursday, October 18, 2012

"Gambel's" White-crowned Sparrows

A western form White-crowned Sparrow (Zonotrichia leucophrys) was banded by the Rouge River Bird Observatory on 20 October 2006, described below and compared with typical eastern and “intergrade” forms. There is a very nice article on identifying subspecies, with range maps, in a 1995 issue of Birding (27:182-200). Two other web pages, Oiseaux Birds and David Sibley’s blog also have a nice set of comparative photos of some of the variations.

Adult White-crowned Sparrows of all subspecies have black and white head stripes, while juvenile birds have brown and tan head stripes. Here are some examples of juvenile White-crowned Sparrows banded at RRBO, concluding with the western “Gambels” type banded in 2006.

Above is a  typical eastern hatching-year White-crowned Sparrow (Z. l. leucophrys).  Characteristics include a deep-based, pinkish bill with a dark tip, a medium-brown crown stripe, and a dark line through the eye that connects to the crown stripe in front of the eye.

This White-crowned Sparrow, banded on 16 Oct 2006, shows traits of an intergrade between the eastern form and the western “Gambel’s” White-crowned Sparrow form. Bill shape and color and crown color are similar to the eastern form.  The lack of dark feathering between the eye and crown is more like the western forms.

This White-crowned Sparrow banded on 20 Oct 2006 is most like the western “Gambel’s” form (Z. l. gambelii).  It not only lacks dark feathering between the eye and crown, but has a thinner, orange bill which is yellowish at the tip (described as looking like “candy corn”), and a more rufous crown stripe coloring.

This adult White-crowned Sparrow banded on 22 Oct 2012 is also a good candidate for the western “Gambel’s” form. It obviously lacks dark feathering between the eye and crown, the bill shape is farily narrow, but the bill color is a little ambiguous

Wednesday, October 10, 2012

Banding update

We are well on our way to banding the fewest birds in any fall season in 20 years! The fewest new birds we have banded prior to this year was 739 in 1996. Our "slowest" year was actually 2008, when our capture rate (birds banded as a function of the number of nets we used and the number of hours we had them open) was 33.4 birds per 100 net hours. You can see our current numbers in the right sidebar. I'm pretty sure there is not enough time left in the season for this year not to come in dead last in both categories.

While a lack of birds is disappointing (and kind of alarming), these low numbers are providing valuable data.The weather this growing season is mostly responsible, in particular the drought.  In a previous post, I noted the low numbers of young birds we were banding. This has continued to be the case. American Robins in particular have exemplified the kind of season we are having.

The average number of robins we band in fall is 188, with 300 or so not being uncommon. Prior to today, we had banded only 15!! Today we had 17 more, bringing our total to 32, a remarkably low number.

Based on our 1992-2011 fall data, we can expect around 76% of the robins to be hatching-year birds. This year it is only 23%. This is an indication that robins failed to fledge a "typical" number of young. Since many of the robins we are catching now are migrants likely to have nested elsewhere, this suggests that nesting failure was not just a local problem. And indeed, the drought covered a very large part of the continent.

One interesting aspect is that nearly half young birds I have captured recently still had some spotting on their breasts; this is the plumage they have when leaving the nest. Typically, only about 3% of hatching-year birds have spots this late in the season, having already mostly completed their fall molt. Similarly, 61% of the adult robins are still completing their fall molt. In the past, only about 16% were still molting at this time of year. It looks like, then, that many robins nested late this year -- probably after losing an earlier brood.  It's possible that the skewed ratio of young to older birds may even out a bit in the next couple of weeks.

The prolonged and severe drought contributes to low reproductive success by diminishing food supplies, especially for birds like robins that utilize a lot of leaf-litter or soil invertebrates to feed their young. Besides just reducing the number of birds available, the dry weather contributes to our low capture rates by impacting the fruit crop. Our very early spring heat wave also compounded the failure of many types of wild fruit, as I discussed earlier in the season. Fruit is a vital food source for many species of migratory birds, and of course, a main topic of our research.

In short, many of our staple fruiting plants had small crops or did not fruit, or fruited later than usual. I noted that locally, fruit crops were better in areas adjacent to water. Our banding site is not (unlike many banding stations, which are located in some sort of coastal situation). So this year provided interesting insight into the impacts of growing season weather.

In a future post, I'll provide an update on the 2012 fruit crop and what we found birds were eating.

Tuesday, September 25, 2012

Silent Spring after 50 years

Have we learned our lesson?

Fifty years ago this month the important book Silent Spring by Rachel Carson was published. This book warned about the lethal and persistent effects of the pesticide DDT. This book, while in some ways outdated, remains a classic not only for its role in inspiring environmental stewardship, but also because although DDT has been banned in the United States, as a society we still enthusiastically embrace a whole suite of chemicals that end up in our air, water, and soil (and ultimately in animals and ourselves). And we still tend to trust that they are perfectly safe.

In fact, testing of pesticides and other chemicals is focused specifically on active ingredients used in certain amounts and circumstances. Many people use chemicals in ways not intended by the manufacturers, in amounts beyond recommended volumes, in combination with other chemicals, and when none are really needed in the first place. Aside from the risks of these types of applications, we further know very little about the components of this toxic soup interact with each other and the environment.

An excellent example is the American obsession with cosmetic lawn and garden chemicals. I don't want to get too soap-boxy here, but I can tell you two things. First, you can have a nice lawn (if you must) and garden without the use of any chemicals. I've done this my whole life. Second, one of the best things you can do for birds (your pets, the ecosystem, and yourself) in your area is to quit using all chemicals in your yard, because they do harm birds.

I see the effects of "safe" lawn chemicals every year on common birds. I have held emaciated robins in my hands as they had seizures and died, and looked up from their lifeless bodies to rest my gaze upon those little signs indicating an expanse of grass was sprayed with some concoction. Without direct toxicology tests, I can't honestly say lawn chemical exposure was the direct cause of these deaths. I do know that robins can't read to keep off the grass, that their symptoms are typical of exposure, and it is far too common an occurrence to not at least suspect that some combination of chemical exposure is to blame.

On this anniversary of the publication of Silent Spring, I encourage you to read or re-read this book and related material. We are in an age where enough data is available for us to be truly informed and where our actions can make a real difference. Unfortunately, we are also at a point where we are distrustful of science, and often bombarded with conflicting messages from special interest groups. I don't have a horse in this race, except my love for the natural world. Here are my recommendations:

An excellent overview of the context and impact of Silent Spring can be found at the Pop History Dig website: Power in the Pen: Silent Spring 1962. The New York Times Magazine also recently published How Silent Spring ignited the environmental movement.

The book itself, Silent Spring (Kindle edition here), as well as a new biography of Rachel Carson, On a Farther Shore: The Life and Legacy of Rachel Carson (Kindle here).

I also strongly recommend Our Stolen Future, which further explores synthetic chemicals in the environment.

There are many excellent sites on thee continued risk of chemicals many of us continue to use regularly. The non-profit Environmental and Human Health published a report very worth reading: Risks from Lawn Care Pesticides. The organization Beyond Pesticides has extensive information about pesticide issues, risks, and alternatives.

Friday, September 14, 2012

MIA: young birds

In our last update, I mentioned that I thought the hot, dry summer might have resulted in low productivity -- fewer young birds fledged. Fall banding is an excellent way to assess productivity, as the ratio of young to adult birds is easy to tally. Here at RRBO, about 81% of the birds we band in fall are young-of-the-year, known to banders as "hatch-year" birds. This is fairly typical, although coastal banding stations may see 90% or higher, since young songbirds often follow slightly different migration routes than adults, and seem to favor coastal routes.

So far this fall, the number of adult birds we are banding has been unusually high. Sometimes we see this in individual species, but it seems like it is across the board so far. I took a look at the first month of fall banding for all years prior to this year combined, and noted that 86% of the birds banded were hatch-year birds. Since we begin banding in August, we usually start out banding a lot of the recently-fledged resident birds, especially catbirds, so the slightly higher percentage compared to the overall fall average is expected. This year so far, only 68% of the birds have been hatch-year.

We will have to see how this plays out over the season. I am especially concerned at the overall low numbers of American Robins and Gray Catbirds, especially young birds. I will address these in a future post.

Let's look at a more cheerful graph -- the composition of warbler species banded so far this fall.

The "other" category are three species for which only single birds have been banded: Black-and-White, Cape May, and Palm Warbler.

Since it's so early in the season, it's hard to say whether or not some of these species will be banded in larger numbers than usual. Nashville Warblers are one our most frequently-banded species; they have a long migration period so this graph is not very revealing. My gut based on the last 20 years is that redstarts may end up being more numerous this year than usual. Right now they comprise 24% of the warbler species banded. The overall fall average is 12%.

It looks like the summer-like weather is gone for the next week, and a dramatic shift in the jet stream over the coming days is likely to bring in lots of birds. Stay tuned.

Friday, September 7, 2012

August banding

Fall banding 2012 started on August 17. As I suspected, things have been slow. The very hot, dry summer seems to have resulted in low reproductive productivity for our most common local breeding bird species, such as American Robins. It's just difficult for them to find ground-dwelling invertebrates to feed their young when it is so dry.

Rather than just summarize numbers this fall banding season, I'd like to focus more on one of our current research projects: the fall diet of birds. As regular followers know, RRBO's research focus is on the fall stopover ecology of migrant birds, in particular what kinds of fruit birds are eating in this urban forest patch. We do this by collecting seeds passed by the birds that we band when they poop in the bags we transport them in. This is the 6th year we have collected samples from Catharus thrushes (Swainson's, Gray-cheeked, and Hermit), and the 4th year we have done expanded sampling on all bird species.

Through 2011, we have collected samples from over 1,000 birds of 17 species. Of the nearly 6,400 individual seeds in these samples, only nine have gone unidentified (I'll describe in detail in a future post how we identify all the seeds). Twenty plant taxa are represented in the samples, and most seeds have been identified to species. Thus, we have a great picture of which species of fruit are being eaten by birds.

Pokeweed fruit.
In August, we collected samples from 18 birds. Pokeweed was the most common seed, showing up in 11 samples. We had our first ever sample of poison ivy from a catbird. Usually, this is consumed by woodpeckers or Yellow-rumped Warblers, and nearly always in October. Like quite a few plant species, poison ivy seems to have flowered (and thus set fruit) earlier this season. Other plants may have budded or flowered early (given the long stretch of hot weather in March), then failed to fruit either due to frost in April, or because of the long dry period in summer. We have virtually no crop of wild grapes or relatives such as woodbine/Virginia Creeper. A number of other shrubs that are staples in the diets of fall birds here are ripening late; some portion of shrubs did not set fruit at all.

Poison ivy flowers

Our data for this hot, dry growing season should be an interesting contrast to last year's exceptionally wet summer and add substantially to our picture of what birds eat during fall in an urban natural area.

Wednesday, August 29, 2012

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.


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)

Wednesday, June 27, 2012

Spring 2012 survey results

The spring 2012 survey season took place 3 April through 4 June. On campus, regular surveys were conducted on 58 of the 65 days; some coverage late in the season was truncated due to field work related to our catbird study. Because of the unusual weather (discussed below), surveys were also conducted on 21 days in March.

Excluding March, the campus surveys recorded 124 species (another 19 were recorded in Dearborn off-campus). This is lower than the previous ten-year average of 130 species. The peak day was 3 May with 79 species. This is a similar to our usual peak day total of 80 species, but usually the peak occurs much later in the month (around May 16-20). Both the low species totals and early peak are at least in part attributable to the extremely early leaf-out, which made visual detection of mid- and late-season migrants much more difficult.

This leaf-out -- in which leaf and flower phenology was some five weeks ahead of schedule by April -- was due to the unprecedented hot weather in March. The National Weather Service characterized March 2012 as the warmest on record and the most unusual month in Detroit's history. The average temperature for March was 50.7 F, an incredible 15.6 degrees above the 1874-2011 mean average of 35.1F! Fortunately, the weather did cool down, with April temps right at normal, but May was the 3rd warmest on record. Thus, spring 2012 finished the warmest in southeast Michigan history.

Generally, warm periods in spring that accelerate plant growth also prompt early emergence of insects. This can result in a mis-match between insect resources and the timing of bird migration, especially for birds that are coming from wintering grounds in the tropics. These birds are prompted to migrate by changes in day length, and do not "know" that spring is advanced in the north. The same weather systems that bring warmth to the north may push migrants which have already arrived in the United States northward a little faster. This year, long-distance migrants that had yet to arrive during the early part of the season arrived right about their usual time (see Arrival dates, below).

There were some real concerns that had the hot weather continued, things would have gotten seriously out-of-whack -- you can read my blog post What does summer in winter mean for birds? for a discussion of potential ramifications. Fortunately, cooler weather in April slowed phenology down a bit. While we did have freezing overnight temperatures after the March hot spell, they did not last for many hours in the Detroit area, so insect life was not seriously diminished and it appears that migrants were able to find adequate food resources.

Spring 2012 was also quite dry...especially when compared to last year! In 2011, the precipitation total for Detroit from March through May was over 14 inches. This spring, it was less than half of that, with both April and May having below-average moisture.

While migrants dodged a resource bullet, it seems this combination of advanced plant and insect phenology and dry conditions is likely to have had some impact on breeding birds. This probably depends on how reliant various birds are on particular stages or species of insects as well as the impact weather may have had on a very small landscape scale at locations where birds nested. Perhaps we will detect some changes in the ratio of young to adult birds during fall banding that may shed some light on this. Finally, because they flowered early and pollinators were out and about, many fruiting plants also set fruit early. Fruit is a critical part of the diet of many fall migrants; we'll see if there are any changes in what birds are eating this fall.

Many of the less-common migrants we have come to expect on a nearly annual basis were not recorded this year. This includes Golden-winged Warbler, Prothonotary Warbler, Kentucky Warbler, and Summer Tanager. Acadian and Olive-sided Flycatchers and Philadelphia Vireo were also missed. The most interesting highlight was the number of White-eyed Vireo sightings: five from mid-April to mid-May. Leaf-out was so advanced by mid-May, that many birds, especially non-singing females, may have gone undetected.

I'll add a lowlight on a species I follow and mention frequently: American Crow. Of the 61 days in April and May, crows were recorded in the entire city of Dearborn on only 15 days. Reports were always of one or two birds. Crows were seen more often in March, as observations include migrating birds. In March, crows were reported on 14 days, mostly in ones or twos, with a high number of 11 birds in a flock on 13 March.

Arrival dates
The March hot spell created a flood of reports of early migrants. Many of these are probably best viewed with caution (see my post Early Neotropical migrants for more discussion). Of the 43 migrant species for which we have adequate reliable arrival data, 31 did arrive earlier than the average date calculated through 2011. Both the median and the mode for the number of days early for these species was 2 days. Thirteen species arrived four or more days earlier than average. A few short-distance migrants had record-early dates for Dearborn:
  • Tree Swallow on 18 March, previous early date 22 March
  • Field Sparrow on 18 March, previous early 24 March
  • Chipping Sparrow on 26 March, previous early 30 March
Of the long-distance migrants, new records were:
  • Nashville Warbler on 16 April, previous early 20 April
  • Canada Warbler on 4 May, previous early 5 May
So, nothing particularly outstanding. Many thanks to Darrin O'Brien who assisted with surveys this spring.

Wednesday, June 20, 2012

Dickcissels in Dearborn

(Edited 25 Jun with new data)
There are at least a dozen Dickcissels (maybe more) in the wildflower fields at Ford Road and Mercury. This is the field marked "8" on our page of Ford fields. Note that the fields are marked "No trespassing," so if you visit, please scan from a roadside and be careful of traffic. I first heard these birds on 18 June. My husband Darrin O'Brien saw a bird carrying food later that day, indicating that they are probably nesting. Our survey on 24 June located at least 10 singing males and 2 females. There are also dozens of Savannah Sparrows in this field.

On 20 June, Jim Fowler and Dave Washington located two more Dickcissels in the fields on the south side of Lundy Parkway (field number "6"). Darrin had 9 there on 21 June, and we had eight on 24 June.

The two small wildflower fields ("1a" and "1b") have two birds. So, at least around two dozen Dickcissels in Dearborn!

The last Dickcissel record in Dearborn was from 1 July 1907! The only other confirmed record I could find when researching my book on Dearborn birds was a flock near the Rouge River from 30 July 1899. Three of these birds were collected, and I have examined the specimens in the University of Michigan Museum of Zoology in Ann Arbor. All of these records are attributed to "Springwells." Dearborn's present borders were established in 1929; prior to that portions were known as Fordson and/or Springwells. I believe the 1907 record was from somewhere near what is now Rotunda and Schaefer in Dearborn. The route of the Rouge River has also been altered since 1899, but I think that the 1899 specimens are also from Dearborn.

Long time, no see! The last Dickcissel record from Dearborn was in 1907.This male, 20 June 2012.
Photo by Cathy Carroll, used with permission, all rights reserved.

Female Dickcissel, Dearborn, 20 June 2012.
Photo by Cathy Carroll, used with permission, all rights reserved.

Dickcissels are specialist birds that depend on grasslands. They are known for their unpredictable, semi-nomadic movements, in particular outside of their core prairie habitat in the Great Plains. It's hard to know where they'll show up from year to year.  While they can be quite adaptable and will use non-prairie grassland habitats, the loss of native prairie has been a factor in dramatic population declines. These little birds winter far into South America, mostly in the grasslands of central Venezuela. They winter in huge flocks and can be considered pests on grain farms. They are hunted and poisoned regularly, which no doubt has contributed to declines in their numbers.

The wildflower fields the Dickcissels are using have a high diversity of herbaceous plants which are required by the birds for song perches and nesting substrate. In the great photos above, by Cathy Carroll, the birds are perched on Gray-headed Coneflowers  (Ratibida pinnata), a wonderful native wildflower. The wildflowers also provide for a wide diversity and abundance of insect prey, especially grasshoppers and butterfly and moth larvae, which are needed to raise their young.

Many of the fields planted by Ford Motor Company are sunflowers or hay fields. Those that have wildflowers are the least manipulated by mowing or disturbance and have the most interesting birds. Perhaps this will encourage Ford to convert more of the fields to wildflowers!

Monday, May 21, 2012

Catbird success!

One of our research projects at RRBO is a joint project with Dr. Melissa Bowlin, a faculty member here at UM-Dearborn. Last fall, we placed light-level geologgers (or geolocators) on a sample of Gray Catbirds on campus. Catbirds are one of our most frequently banded birds. These tiny devices measure light several times daily. If placed on a migrating bird, they will record data that can be used to calculate latitude and longitude when compared with sunrise and sunset times and light levels at noon in different geographic locations.

This data can give us a wealth of information on the pace and route of migration, and wintering areas. You can read all about how they are used on the RRBO web site. 

There is a catch (pun fully intended). In order to get the data, the bird must survive a full migration, return to the original banding location the next year, and be recaptured so the geolocator can be removed and the data downloaded. Last fall, we placed a colored leg band on each of the catbirds which also carried a geolocator, so we could more easily re-find any birds that returned this year.

Well, I couldn't have been happier to find one of our color-banded catbirds singing right behind the Environmental Interpretive Center (EIC). Once I was sure he was going to stay put, I set up three nets between two of his favorite singing perches. While I was setting the nets up, I caught a catbird I presumed might be his mate. It was banded, and turned out to be a bird we banded as a hatching-year bird in August 2008.
Nets set up on either side of the driveway to the rear of the
Environmental Interpretive Center. Hard to see? Good!
Very early the next morning it was time to try to catch "the" bird, and Dana Wloch and Darrin O'Brien joined me. Often, territorial male birds will investigate another singing individual of his own species. We placed an iPod playing a loop of a singing catbird behind one of the nets. Sometimes that's enough, but it usually helps to have a stuffed "singer" near the recording. I didn't have a stuffed catbird handy, but I did have a study skin of a European Starling.  He'd have to do.

Vulgaris the Starling Dummy. iPod playing a catbird song in the background.
Once we were set up, it was step back and wait. Our target catbird began singing, and he came in closer to the nets to investigate. Within minutes he swooped over one net, and over the next. Then again. And again. Uh-oh. These nets are kind of hard to see, but it looked like our bird had figured out our ploy and was avoiding them.

Dana and Darrin, dejected. We thought we were in for a long morning.
After about 10 minutes, the catbird flew from behind one net headed back to his usual singing spot and ventured a little too low. Bingo! In the net. We quickly retrieved him.


It didn't take long to take him into the banding lab, remove his geolocator and green band (so we didn't go after him again), and take some measurements so we could let him go.

Three happy catbird catchers, and the subject ready to be released.
This catbird, which was carrying geolocator #929, was the last catbird we put a device on last fall, on 29 September 2011. The bird had originally been banded as an adult on 10 August 2010.

The well-traveled geolocator.

Dr. Bowlin is out of state on another field study, and when she returns she will download the data from the device. Then, it will take some additional time to analyze. Sometimes due to weather or time spent in shaded spots by the birds, the data may difficult to interpret. Hopefully, we'll get good data from this bird, as well as any other catbirds that return that we recapture.

And we have already located the favorite singing perch of another color-banded catbird. I hate to report that we have tried catching this bird for several days and have come pretty close, but so far he seems to be on to us and prefers singing about 10 yards from the nets. We also have a tentative sighting of a third bird, and have some areas left to survey for catbird pairs. I'm optimistic we will be able to retrieve a few more geolocators this season.

About half of our catbirds were sponsored by donors last fall. Unfortunately #929 did not have a sponsor, so we didn't get to provide fun news to one of our supporters. If you are interested in sponsoring a catbird with a geolocator, I'll assign one to anybody making a gift of $300 or greater.

Wednesday, May 16, 2012

North American Migration Count 2012

The North American Migration Count takes place the second Saturday each May. It aims to take a "snapshot" of migration, and is compiled on a county basis. My husband Darrin is the coordinator for Wayne County, and as usual we covered the city of Dearborn together on May 12.

Spring migration this year got off to a great start the first week in May. We had very good numbers of early migrants the last week in April into the first week in May. There was a nice influx that included some mid-season migrants on May 3. Within a few days, however, things began to slow down. On migration count day, we tallied a disappointing 70 species on campus. Warblers in particular were very scarce, with only ten species. Yellow-rumped Warblers had been dwindling, but were absent on count day. Many people commented on the high numbers of White-crowned Sparrows this season, but on count day we had only a few, and no White-throated Sparrows. Our best bird on campus was a Gray-cheeked Thrush, the first of the season.

Darrin taking a quick break on campus during the count. Sometimes,
having too few birds is more tiring than having too many!
We added eight more species at other locations in Dearborn. The original Ford "sunflower field" at Hubbard and Southfield had a minimum of two dozen Bobolinks on May 7, but none stuck around for the count.

The Rouge River at Kingfisher Bluff behind Henry Ford
Community College.
Northern Rough-winged Swallows are nesting in the terra cotta
tubes poking out of the bank at Kingfisher Bluff behind Henry
Ford Community College.
The best bird of the day was an Orchard Oriole at Porath (Kielb) Park. This 11-acre property in a sparse residential area adjacent to railyards and an industrial border of Detroit was once a clay mine for bricks. In the 1940s, fill material from construction of I-94 was added. A federal brownfields grant was used to clean up contamination (still no digging allowed, according to warning signs) and it was turned into a park by the city in 2005. There are a variety of native plants there, but aside from a trail that is mowed through it, the park has not been maintained very well and it's becoming weedy and overgrown.

In addition to the oriole, Porath had two very good butterflies. One was a Common Checkered-Skipper (Pyrgus communis), a southern species that has been seen in southern Michigan with increasing frequency the last few years. Not only is this an uncommon species, this is a pretty early date to see them here. It's unlikely that the larvae (the stage in which they hibernate) can survive here overwinter, so the individuals we typically see are migrants from the south, or perhaps some progeny from these migrants which appear later in the season. Their host plants are in the mallow family, and I have seen them most commonly in vacant lots or neglected fields that are infested with velvet-leaf (Abutilon).

Here is my bad documentary photo of a Common Checkered-Skipper at
Porath Park. Click here for a much nicer shot of one in my Dearborn yard last fall.
We also saw another uncommon butterfly, an "Inornate" Common Ringlet (Coenonympha tullia inornata) When we found our first county record in 2003, it represented a substantial southern range expansion in the state (PDF of my note in the newsletter of the Michigan Entomological Society here). This species now shows up all over the place in southern Michigan, moving south here as it has in New England and Ontario in the last decade or so. I failed to get a photo, but here's one Darrin took last fall in Oakland County.

Both the skipper and the ringlet have been observed on the UM-Dearborn campus as well.

A table of results from the Wayne County North American Migration Count, with links to complete results, is available on the RRBO web site. Once we have data from all the other field participants, I'll put up the 2012 results at that location as well.

Monday, May 7, 2012

Chimney Swift tower!

Chimney Swifts are probably familiar to most people: twittering "flying cigars" in our summer skies, feeding on aerial insects. Like other species of swifts, Chimney Swifts spend most of their time in the air, even mating and bathing on the wing. Chimney Swifts breed across much of eastern North America, and winter in the Amazon basin of northwestern South America.

Patient observers might note individual birds disappearing into tall chimneys during the breeding season. Chimney Swifts make a small nest of twigs, held together and glued with saliva to the inside wall of a chimney-like structure. Only one pair will nest per chimney or structure, but there may also be a few non-breeding swifts, some of which (usually young from a past year) may "help" the breeding swifts feed the young in the nest. Chimney Swifts use chimneys and similar structures outside the breeding season, too. During migration, especially in fall, many hundreds of swifts might use large chimneys to roost in overnight.

Prior to European settlement of North America, Chimney Swifts used hollow trees, caves, and narrow chasms. Their populations probably increased with the availability of human structures for nesting and roosting. However, in recent years Chimney Swift populations have undergone a dramatic decrease. In the U.S., this decline has been about 2.4% per year since the early 1980s; in Michigan the rate has been -1.5% annually (based on Breeding Bird Survey data).
Several factors are probably at play. Most important is a decrease in aerial insect prey, likely due to pesticide use, habitat loss, and a changing climate. Other species of birds that rely on aerial insects, such as Common Nighthawks and swallows, are also on the decline. Add to this a special problem for Chimney Swifts: chimney design has changed in modern times, with many chimneys being too narrow, or covered or lined, for swifts to use.

This has led many organizations and individuals to create artificial Chimney Swift nesting structures. This spring, Stephen Lisius constructed and erected one of these excellent towers behind the Environmental Interpretive Center as his Eagle Scout project.

Stephen designed the tower according to plans similar to the graphic above, which is available in the Chimney Swift Nest Site Research Project Information Handout (PDF). The tower was constructed off-site, and then erected onto a sturdy foundation that had been put in place the week before. Here's the tower in place:

The outside of the tower will be finished soon with weatherization wrap and shingles. Stephen also plans to install a camera, so if/when swifts discover and use the tower, we can see what's going on. We may have to be very patient -- some towers go for years before they are used. I'll keep you posted!

If you are interested in learning more about these towers or even seeing if you'd like to make one yourself, the book Chimney Swift Towers: New Habitat for America's Mysterious Birds is the go-to guide.

Meanwhile, you might consider one of the swift monitoring projects. The program called Swift Night Out is done each fall in the U.S. Bird Studies Canada has initiated a citizen swift monitoring program as well.

Chimney Swift photo by D. Irving under a Creative Commons license. Tower photo by Sara Cole, used by permission.

Monday, April 30, 2012

Moth program results

Our moth program with field guide author Seabrooke Leckie was a great success! We were a bit worried about the cool weather, but Seabrooke explained that many moth species overwinter as adults (rather than eggs, caterpillars, or pupae/cocoons). These cold-hardy species will fly in temperatures cooler than we were experiencing (in the mid-50s).

Seabrooke arrived in late afternoon, and we set up several sheets with different types of light (black light, mercury vapor). Moths are attracted to the lights and land on the sheets.

One of the sheet/light set ups.

We also soaked some rope in a mixture of red wine and brown sugar, and hung them out to attract species that feed on nectar and sap (many adult moths, however, do not eat at all). This mix should really be allowed to ferment, so we didn't have luck with that.

Stinky, sticky wine rope hanging from wood shed.
Seabrooke started out with a short presentation focusing on moths in the environment.

Then our group of about 30 people made the rounds of the sheets and collected moths in clear pill bottles. These were brought back into the building where Seabrooke identified them.

Seabrooke also helped my husband Darrin identify some photographs he had taken the last few years.

Our friend Don Sherwood has been raising silkworm moths. He brought along this Luna Moth to show everybody. I think this is probably one of the most beautiful moths in the world!

Here is our list of moths that came to the lights, with links to the species or genus at BugGuide, a great online resource for insect identification. Some very tiny moths ("micromoths") were only identified to genus.
The Curve-toothed Geometer. We released
all the moths at the end of the night.
  1. Unicorn Prominent (Schizura unicornus)
  2. The Gem (Orthonama obstiptata)
  3. Celery Leaftier (Udea rubigalis)
  4. Palmerworm Moth (Dichomeris ligulella)
  5. Featherduster Agonopterix (Agonopterix pulvipennella)
  6. Confused Woodgrain (Morrisonia confusa)
  7. Acleris sp.
  8. Common Acleris (Acleris subnivana)
  9. The White-Speck/Armyworm (Mythimna unipuncta)
  10. Dusky Groundling (Condica vecors)
  11. Olive-and-black Carpet (Acasis viridata)
  12. Epinotia sp.
  13. Eupithica sp.
  14. Bent-line Carpet (Costaconvexa centrostrigaria)
  15. Curve-toothed Geometer (Eutrapela clemataria)
  16. Red-banded Leafroller (Argyrotaenia velutinana)
  17. Gray-banded Leafroller (Argyrotaenia mariana)
There were also a couple of "get-aways" and some that flew near the sheets that we didn't catch.

Thank you Seabrooke for an excellent evening!

Julie Craves and Seabrooke Leckie.