Fall banding 2010: Week #2 in review

Warblers welcome!

Week #2 was abbreviated due to my participation on a state advisory panel. The modest totals for the week were 59 birds of 21 species, plus recaps and another batch of hummingbirds released unbanded. Returns of birds banded in previous years included a female American Robin from 2007, and a Gray Catbird from last fall.

The best part of early fall is the nice variety of warblers that start to come through. Later, we'll have higher numbers of some species, or more diversity of birds overall. But this early in the season there is a nice parade of often-subtle, but always pretty, warblers. Here are a few from this week:

Blackburnian Warbler.

Chestnut-sided Warbler. Am I the only person who thinks the green looks like the color you get when you use a yellow highlighter on newsprint?

Black-and-white Warbler.

Wilson's Warbler. Audubon called this species "Wilson's Flycatching Warbler" and you can tell they do some aerial flycatching by the "whiskers" around the bill, known as rictal bristles. They help trap small flying insects.

Tennessee Warbler. More of a gleaner, it lacks the long rictal bristles of the Wilson's Warbler and uses its sharp bill to probe leaves for insects.


One thing we note when we band Tennessee Warblers is the presence (and size) of a white spot on the outer tail feather. About 30% of adult and 20% of hatching-year birds have this spot at our site, and usually if it is present in hatching-year birds it is smaller than this.

Other highlights this week included our first Swainson's Thrush, one of my focal species in my study of use of resources during migratory stopover.

The biggest thing I got in the nets was a female Cooper's Hawk. This is only the third Coop we've caught at RRBO, since they are generally too large and heavy to stay in the nets; and the first female, which are larger than males.

I've been grabbed by little male Sharp-shinned Hawks, which are only about the size of a flicker, and they have needle-sharp talons than can hardly be felt going in...but can be a real problem when the bird starts tugging to get them out! This big female Coop had talons to be respected and very long legs. It's times like these I'm glad I always carry too many bird bags. I handed her a wad to grab onto until I could secure her legs. Really, you can never let go of the legs when handling a hawk, so banding one is much easier as a two-person job. As luck would have it I was working alone and nobody was even in the building to snap some photos. Everything went without mishap as she was quite calm and cooperative, but I wished I could have photographed her eyes -- she had the very green-gray eyes of a young bird (soon to turn yellow and eventually red). That and the fact that her back feathers had extensive rufous tips may indicate she was hatched locally and not a migrant from farther away.

With hawks you worry about the feet, with Rose-breasted Grosbeaks you worry about getting bitten. That bill is very strong and while I've never had one draw blood, they pinch so hard you get left with a divot on your finger that lasts for hours. Plus, they just have nasty dispositions. This adult female didn't nip me, since I've handled enough of them to know not to be careless and always put them in a distinctive colorful bird bag so I don't get surprised when I reach in.

The weather forecast for at least the beginning of next week sounds like a return to summer; not very conducive to migratory movement. We'll see what ends up in the nets.

A reminder that we are moving the RRBO web site in the next few days. Please use this URL to access the current/soon-to-be-replaced site, it will continue working: http://www.umd.umich.edu/dept/rouge_river and use my long University address (jcraves AT umd DOT umich DOT edu) or gmail address (jac DOT rrbo AT gmail DOT com) to contact me. Don't use the jac AT rrbo DOT org until further notice.

I'll be posting frequent updates here -- I'm very excited about the new site and can't wait to hear what you think!

Fall banding 2010: Week #1 in review

A week of scruffy birds

RRBO's 19th fall banding season got underway this week. First, a big thanks to local birder and RRBO volunteer Jim Fowler, who decided his songbird banding days are behind him, for donating his net poles to us. And to Robert Schubert, EIC student staffer, for cutting a whole batch more. We have a full set of straight poles to work with this season. Robert and Dana Wloch, one of my undergraduate research assistants, also helped out with getting the net lanes ready for banding. Many thanks!

The first week of banding usually starts slowly, as I tend to be putzing around pruning net lanes and putting up the final nets. This week there were 78 new birds banded, 4 recaptures, and 18 birds released unbanded (14 Ruby-throated Hummingbirds, the rest House Sparrows). This represented 25 species. Most were local breeders, but migrants included Least and Yellow-bellied Flycatchers; and Black-and-White, Nashville, Magnolia, and Chestnut-sided Warblers.

Most of the locally nesting species have one thing in common this time of year: they are in the midst of their fall molt. Once finished with nesting, adult birds replace all of their feathers. It occurs systematically, so they can still fly, but not quite as well. Thus a lot of adults tend to be a bit secretive.

Gray Catbirds are our #1 species. This adult female was originally banded in May 2008, and recaptured this week. What a mess.

Young birds (born this year and called "hatching year", HY for short) are also beginning to molt heavily now, replacing their juvenal* plumage with their first set of adult feathers. This HY catbird is actually one of the better looking individuals.

Most HY songbirds only molt body feathers, but some species also replace some flight feathers (wing or tail). Upon examination, it looked like this disheveled HY Song Sparrow lost its tail and was replacing it, versus a normal molt. The rest of the messy look was typical, though.

Indigo Buntings nest on campus, but I've never had a nest in the banding area until this season. This recently fledged bird was being tended by a male parent, or I might have had a hard time figuring out what species it was! When I catch a bird this young, I immediately run back to the banding lab, process the bird, and run back and return it where I found it. Once reunited with his offspring, the dad quit scolding me!

Up to about 5 or 6 years ago, Blue-gray Gnatcatchers didn't nest on campus. In fact, 20 years ago, I don't remember them nesting very frequently in the county. During the first Michigan Breeding Bird Atlas (1983-1988), breeding evidence was noted in only four quarter-townships in Wayne Co. Things have changed rather dramatically. During Michigan Breeding Bird Atlas II (2001-2007), 39 quarter-townships had breeding evidence, and for the last few years, three to five pairs have nested on campus. This HY bird, likely from a family that has been present this summer near the banding area, is only the 12th RRBO has banded since 1992, and only the second in fall.

Two interesting "abnormal" birds were banded this week.

This HY Eastern Kingbird, probably from a nest on campus, had fleshy tumors on the "shoulders" of both wings. The tumor on the left wing was small, but this one on the right wing was 14.2 mm. I see tumors of this sort from time to time. I suspect this was a feather cyst; a contributing factor for this condition may be malnutrition. This bird also had a prominent "fault bar" on the tail. This occurs when actively growing feathers stop growing for a period of time due to nutritional stress (lengthy discussion here). The bird flew well, but it's hard to say how much this will hamper it on its long fall migration.

American Goldfinches are abundant in one section of the banding area. They are just starting to fledge their young. This bird, however, was an adult male. Note that the first secondary feather on one wing was completely black on the underside, rather than having a white base. Usually when one sees birds with odd-colored feathers, the aberrant feather is white. Excessive dark plumage, or melanism, is less common, and I don't recall ever seeing single melanistic feathers or patches of melanistic feathers any birds, much less the many thousands of goldfinches I've handled.

This will be the fourth year of collecting fecal samples from Catharus thrushes to examine what kinds of fruit they are eating. It's the second year that Dana Wloch will be assisting by collecting and compiling samples from other bird species. This week resulted in 19 samples being "donated" by catbirds, American Robins, and a couple of Cedar Waxwings.

Welcome rain and the passage of a front this weekend should perk things up next week.

***

*"Juvenal" is the term for a bird's first plumage; "juvenile" is a generic term for a youngster. For more on plumages and molts, extremely useful in aiding in ageing and identification of birds, Plumage and Molt at Audubon Guides, and Molt and Plumage Lab at Biological Ramblings. An excellent new book on the topic for birders, Peterson Reference Guide to Molt in North American Birds was published this year. I recommend it.

Distinguished alumni

Many volunteer bird banders have passed through the ranks at RRBO, over a hundred last time I counted. They have been staff, faculty, and students from U of M-Dearborn and other colleges as well as community members, friends, and relatives. A number of couples have met while volunteering for RRBO (it even led one couple to marriage: I met my husband Darrin in 1995 when he volunteered for me!).

Here are just a few current and past RRBO banders that have careers in wildlife or environmental fields. I like to think that their experiences here have proved valuable in their current work. Only a few of them band birds as part of their jobs, but banding can help hone organizational skills and attention to detail, as well as teach patience, how to appreciate good shade-grown coffee, the finer points of political debate, and tolerance of mosquitoes and bird poop.

Bold indicates the volunteer was a U of M-Dearborn student (undergrad) during their RRBO tenure, italics indicates a U of M-Ann Arbor student (mostly graduate students).

Dea Armstong -- City Ornithologist, Ann Arbor Natural Areas Preservation Dept.

Mary Bohling -- Extension Educator, Michigan Sea Grant.

Tom Dietsch -- Assistant Researcher, Center for Tropical Research, University of California, Los Angeles. Tom is also a Research Associate at the Smithsonian Migratory Bird Center.

Kim Hall -- Climate Change Ecologist, The Nature Conservancy, Great Lakes Region (see a profile and interview here), Assistant Professor, Michigan State University.

Matt Kleitch -- Northern Lower Peninsula Project Director, The Nature Conservancy Michigan

Andrea Kreljevic -- Program Associate, Audubon International Alliances Program.

Greg Norwood -- Biological Technician, USFWS, Detroit River International Wildlife Refuge.

Sally Petrella -- Volunteer Monitoring Program Manager, Friends of the Rouge.

Beth Johnson -- Commissary Supervisor, Detroit Zoo (here's a great article on her!)

Julian Wood -- San Franciso Bay Program Manager, PRBO Conservation Science (formerly Point Reyes Bird Observatory), California.

Mark Dettling -- Terrestrial Ecologist, PRBO Conservation Science (formerly Point Reyes Bird Observatory), California.

Don Yee --Assistant Professor, Biological Sciences, University of Southern Mississippi

Mike Clipper -- Program Analyst, U.S. Environmental Protection Agency

Nancy Parachini -- Forest Legacy Program, U.S. Forest Service

If you're an RRBO banding alum that I have lost track of, feel free to drop me a line and catch up!

Cats eat bird eggs

One of the presentations I attended at an ornithological meeting earlier this year was "Cats and fat doves: resolving the urban nest predator paradox." The project is looking at nest predators in urban versus rural areas, and if and how they differ.

This particular study used Northern Mockingbirds in Florida as subjects. Mockingbirds are to Florida what American Robins are to Michigan as far as common nesting yard birds are concerned. The researchers located dozens of nests and put cameras on them. These cameras included the ability to monitor the nests at night.

Although Cooper's Hawks were present at all the urban sites, they are not major nest predators of mockingbirds in urban settings, but tend instead to eat abundant, profitable, and easy-to-catch prey -- usually doves and pigeons.

The main nest predator in urban/suburban areas, accounting for 70% of nest predation, was house cats (see this chart). This didn't surprise me, but just reinforced what we know about outdoor cats: they are extremely effective predators of birds and other small wildlife. Also not too surprising was that the surveillance showed that cats were very adept at climbing the trees and raiding the nests.

Yet two facets of the results were particularly interesting to me. When cats predated a mockingbird nest, 28.6% of the time it was to eat the eggs; the rest of the time it was the nestlings that were taken. Thus, the reproductive ability of the mockingbirds was destroyed.

The other aspect was that 94% of the cat predation took place at night.

So please, keep your cat indoors. This is especially critical during the breeding season and at night.

My cats Sophie and Juniper are strictly indoor cats. Everyone is happy: the cats, the birds, and us.

Update: Shortly after I wrote this, The Wildlife Society and the American Bird Conservancy put out a joint press release to remind people that this is a particularly critical time to keep cats indoors. You can read it here.

Spring 2010 migration in review

The spring 2010 survey season took place on 47 days between 1 April through 4 June. There were surveys on most mornings in April and nearly every day in May except during heavy rain. As in past years, each survey always included a 1.5-mile standard route in the natural area on campus. Many days, additional area was covered; distance, time, and birds counted on these legs were recorded separately but are discussed below in aggregate. On campus, 129 species were recorded (another 9 were recorded in Dearborn off-campus). This equals the previous 12-year mean. The peak calendar week was 16 through 22 May with 92 species. This is the same peak week as 2009, but last year 95 species were recorded that week. The peak day was 16 May (18 May last year) with 76 species (ten fewer than 2009). Weather The National Weather Service reported that 2010 had the warmest spring on record for Detroit, and the warmest spring since 1991 across most of the southern Michigan region. This was largely due to warm temperatures in March and April (both months in the top 20 warmest lists for southeast Michigan). The first week in April was particularly hot -- the warmest first week in April in climate history at Detroit, Flint, and Saginaw. However, there were below-average temperatures the second week in May. At Detroit much of the spring was dry, with precipitation well below average through the end of April. Rain in May helped boost precip levels up and much of the region was near-normal by the end of May. These weather patterns were guided by a jet stream that was generally south of our region up until May. General trends One inevitable result of warm weather early in the spring is that trees leaf out earlier, making detecting birds more difficult. While most spring birds are recorded by hearing them sing, this obviously doesn't work with silent birds, especially females. The understory here on campus is now dominated in most areas by non-native shrub genera that also tend to leaf out early: Lonicera (honeysuckles) and Rhamnus/Frangula (buckthorns). These hindrances to detectability may have played a role in overall low numbers of many species of migrants, and late season migrants in particular. Species that make up the caboose of spring migration here, such as both cuckoos and Blackpoll, Canada, and Mourning Warblers, were found only in very modest numbers over a period of just a few days. I hope that detectability, favorable weather promoting migration past our site, or some other benign factor was responsible for the lack of late-season migrants. We will probably never know if the burning of oil from the Deepwater Horizon catastrophe in the Gulf disoriented, sickened, or killed migrant songbirds. Whether it did or not, we can only wait and see how it effects southbound migrants, directly or indirectly. As of this writing, unknown thousands of barrels of oil are still belching from the sea floor. Right now, our minds are with the waterbirds, sea creatures, and humans that are being immediately and urgently impacted by these malignant plumes of oil. I'm sure we have yet to imagine the profound and far-reaching impacts this disaster will have on wildlife -- maybe even migrant songbirds -- in the years to come. Already troubling to me is the apparent decline in the number of individuals of some common species. Black-throated Blue Warbler, Black-and-white Warbler, American Redstart, and Ovenbird are good examples. The number of individuals of each of these species posted a greater than 30% decline over the average number counted the previous three years. This ranged from 33% fewer redstarts to 57% fewer Black-throated Blue Warblers. These numbers have not been adjusted for effort, but effort has been similar the past four years, hence the short time frame given. In a few more months, 17 years of daily spring surveys with effort data will be digitized and available for analysis, providing a much clearer picture. But even this back-of-the envelope calculation may be cause for alarm, as this suite of species has something in common: they all winter primarily in the West Indies. John Faaborg's excellent long-term winter banding project in Puerto Rico has noted very alarming declines in some of the most common wintering North American migrants on his study plot -- and both Black-and-white Warbler and Ovenbird have declined to less than 20% of their original abundances since 1973. Migrant birds have complex life histories, so it is hard to draw conclusions from one year and one place. If you are interested in the struggle to understand how to monitor and evaluate migratory songbirds, I recommend this excellent overview (PDF): Conserving migratory land birds in the New World: Do we know enough? Ecological Applications 20:398-418. You don't need a lot of technical chops in bird ecology to get the gist of what we are up against when you read this paper. You can help! There is power in large amounts of data. For this reason, I encourage all readers to consider contributing their past and future bird data to eBird. I believe this is our best hope for strong evidence to shape conservation of birds for decades to come. Back to spring 2010... Arrival dates Only a few species posted record early spring arrival dates this year. Blue-gray Gnatcatchers arrived on 8 April, four days earlier than the previous early date. On 15 April, a Blue-headed Vireo showed up, four days early. When they were recorded on 16 April, Chimney Swifts were two days early. I keep track of the arrival dates of over 40 species of conspicuous (easily detectable) migrant species. About half of these species arrived earlier this year than the previous 16-year mean (an average of 4 days earlier), while about half arrived later (average 3 days later). More interesting, perhaps, is comparing the 2010 arrival date with the mean for the first 7 years (for most species, 1993-1999). In 2010, 62% of species arrived earlier than they did during the early 1990s, an average of 5 days earlier. The 31% that arrived later did so on average of 3 days later. If we look at this group of species and compare the early period (for most species, 1993-1996) with the current period (2003-2010), the trend toward earlier arrivals is even more pronounced. Nearly 79% of species are arriving earlier (by an average of 4 days), while less than 17% are arriving later (3 days). This method uses arithmetic means, and more rigorous statistical testing over longer time periods will be done once digitization of all years of spring survey data is complete. Highlights Notable birds were rather few and far between this year. No outstanding rarities were recorded. A number of less common species were found on campus: Common Loon (flyover, 15 Apr), American Coot (7 Apr), Sandhill Crane (flyover, 5 May), Red-headed Woodpecker (5 May), White-eyed Vireo (25 and 30 May, probably the same bird), Hooded Warbler (6 and 21 May), Summer Tanager (14 and 19 May), and Orchard Oriole (1 May, and another bird that arrived on 23 May and was present through the end of May). Perhaps more notable were the birds not recorded. For the first time in 18 years, we did not record any Blue-winged Warblers, normally a common species. Other species that are annual here but were missed this year -- Philadelphia Vireo, Orange-crowned Warbler, and Connecticut Warbler -- can be difficult to find and have often been picked up during banding operations versus surveys. Because we do not currently have a spring research project that can be addressed by the capture of birds, we did not band birds again this spring and so did not record these species. Many thanks to Darrin O'Brien and Jerry Sadowski, who assisted with surveys this spring.