Fall 2009: Week #5 in review

It was another quiet week. There was an influx of migrants on Sep 15, and some obvious large movements of American Robins and Blue Jays beginning on Sep 17. Some new species were recorded this week. Philadelphia Vireos have a very tight fall migration window right around September 15. We saw our first on Sep 12, and banded two on the 15th.

The 16th saw our first White-throated Sparrow of the season, and more were around on Sep 20. Sep 19 we had our first Gray-cheeked Thrush. Cape May Warblers seem to have had a good year. We banded two nice-looking hatching-year males, one of which is shown at the top of the post.
Two older birds were also recaptured this week. The first was a female Northern Cardinal first banded as an adult on April 13, 2003, making her at least 7 years old. We had recaptured her a number of times in 2003 and 2004, but this was the first recapture since then.

Next was a Gray Catbird that had been banded as an adult, in its second year, on May 17, 2005, making this bird at least five years old. We have captured it several times each year, often in breeding condition -- this was a male.
And here's my ID tip of the week (don't get your hopes up that I'll have one weekly!). The bird above is a Chestnut-sided Warbler. Like many (most that I see) individuals of this species in the fall, there isn't any chestnut on the sides. However, the color of the back and top of the head are very distinctive. To me, it's just like the color you get when you use a fluorescent yellow highlighter on newsprint. What do you think?

How do we know what thrushes are eating?

Last fall, I described the focus of my research: the autumn stopover ecology of migrant thrushes. My paper summarizing weight and fat changes in Hermit, Gray-cheeked (shown above), and Swainson's Thrushes was published earlier this year. This is the third year of building on those results by looking at the specific resources thrushes use here in the fall. Because most migrant birds, including those that typically eat insects, also incorporate fruit into their fall migratory diet, the thrushes make great surrogates for a whole suite of migrant species.

There are lots of fruiting trees, shrubs, and plants on campus. Our banding area, for instance, is located in an area with a high density of Gray Dogwood (Cornus racemosa, below), a native shrub with plentiful white berries.

However, like most urban areas, many of the dominant fruiting plants are from non-native species, such as the Glossy Buckthorn (Frangula alnus) shown below.

As I mentioned previously, some of the questions I seek to answer include which fruiting plants and shrubs commonly found in urban areas -- both native and introduced -- are most important to migratory birds? What is their relative availability? If highly invaded urban natural areas are to undergo restoration efforts, which introduced plants should be left to provide resources for migrant birds while native plants become established?

To find out what the thrushes are eating, we simply collect the droppings they leave in the bags we use to transport the birds from the nets to the banding station. Because fruit passes through birds so quickly (and it is thought that many birds, especially migrants, choose fruit that can be processed quickly and efficiently), we know that whatever they poop out has been eaten on-site. We collect each sample in a plastic bag, labeled with the bird's information.

Later, I sort through and identify all the seeds. I have assembled samples of nearly all the seeds found in fruits growing in the campus natural area (certainly all the common ones). I've also put together a reference book, made up of magnified photos of seeds of dozens of species; these photos are available at the excellent USDA PLANTS database web site. It's actually pretty straightforward. I've had very few seeds I have not been able to identify. I think a lot of them are just malformed seeds of common species. So far, I've collected over 200 seeds from 100 samples from 79 birds (some are from multiple samples from the same bird captured more than once).

In order to determine if resident birds are competing with migrants for the same fruits, or depleting certain fruiting species before migrants arrive, I've started collecting samples from all species of birds, concentrating on American Robins and Gray Catbirds. As we catch WAY more robins and catbirds than thrushes, we will end up with a lot of samples. A UM-D undergraduate and bander, Dana Wloch, will be assisting with the sorting, identification, and compiling of the seed samples as an independent research project this fall. Her time will go to waste, so to speak (sorry, I couldn't resist).

Interested in what I have discovered so far? I'll be presenting an overview of my research and some preliminary seed sampling results at presentations at several bird groups over the winter. The first two are November 2 for Macomb Audubon Society, and November 16 for Grosse Pointe Audubon Society. Check their web sites for locations and times. I'll announce January program dates in a couple months.

Fall 2009: Week #4 in review

I don't have much to say about this week. It was pretty boring. We've had some nice groups of warblers, usually consisting of a dozen species, right behind the EIC. Not many have materialized in the banding nets, however. I think this may be the slowest start to a fall season ever. I've updated the stats in the sidebar, and leave you with a photo of a pair of Black-throated Blue Warblers banded this week. We need some good weather fronts to get things moving, but nothing looks promising over the next 5 days or so.

Fall 2009: Week #3 in review

In contrast to last week, this week was gorgeous. A high pressure system remained stalled over the region, creating beautiful weather but a doldrum of sorts for migrants. Last weekend saw some movement, and early in the week, which meant we had our first observations of Cape May Warbler, Magnolia Warbler, Black-and-white Warbler, Chestnut-sided Warbler, and Blackburnian Warbler. We banded several other new arrivals, including Nashville Warbler, Tennessee Warbler, Ovenbird, and Wilson's Warbler. As the week progressed, things just petered out.

Ovenbirds are a personal favorite.

The air is filled with the (obnoxious, if you ask me) begging calls of young American Goldfinch, a species that is among our latest nesters. We've started catching families. The adults are just now beginning their fall molt, and their old feathers are extremely worn.

The white wing bars on this adult male goldfinch have worn nearly completely off. Dark pigments make feathers stronger, and the pale areas often wear away first.

I've also netted a lot of hummingbirds this year; one day this week I released eleven. I presume many are the same individuals, but between mulitple birds in the nets at the same time and plumage differences, I know there were at least seven different ones out there one day. Hummingbirds require special bands and permits, so I just release the birds when I catch them.

A molting adult male hummingbird ready to zip off. Only a few of the 40 I've caught so far have been adult males or this one!).

The most disappointing news of the week was finding out that the massive construction project next door at Henry Ford Community College will not be complete for at least another month. This loud, dusty project is directly adjacent to my site, and the bulldozers, piledrivers, and other big noisy machinery get going just after sunrise. I believe this is having a negative impact on my banding activities. The resident birds seem to be used to the commotion, but when the hubbub gets vigorous, the migrants seem to move away from it all. Although the very large underground retention basin, capped with a parking lot, is supposed to be complete by October 15, this is a three year project and will continue the next two summers. Arrgg!

The big dig next door. If this view isn't enough, for the next couple of months, you can have the excitement of following along on a web cam.

Fall 2009: Week #2 in review

This week was largely a washout. Even during dry periods, the generally damp weather has really encouraged the mosquitoes, which are worse this year than I can ever remember them being. Yuck!

The first boreal-nesting migrant was banded this week, a young female Canada Warbler on 25 August. A couple more Baltimore Orioles were in the nets, thus breaking our previous fall record of 14 banded; we now stand at 16. I've banded five Yellow-shafted Flickers so far, which is above-average. They are fairly heavy and so do not "stick" in the nets very well. But they seem to love digging around in the new wood chips, so I expect we may set a record for this species this year as well.

Young (hatching-year) female Canada Warblers can be pretty dull.

Most notable bird banded this week, in my opinion, was an adult Red-eyed Vireo netted on 25 August. It was a recapture, and had originally been banded, also as an adult, in August 2003. This means this bird is at least 7 years old. We've had returns of other Red-eyed Vireos before, but prior to this bird the longest period between recaptures was less than 5 years. You can take a look at RRBO's age records on this page. It lists a variety of species with at least two years between captures. According to the Bird Banding Lab's longevity records, the oldest Red-eyed Vireo is estimated at 10 years, 2 months old.

What makes this particularly remarkable is that Red-eyed Vireos winter in South America, making the minimum distance traveled between Dearborn and the northern coast of Colombia about 2200 miles one-way.


Range map for Red-eyed Vireo, from Cornell's All About Birds, a recommended resource.

This bird, then, has flown at least 36,000 miles on migratory flights!

Looks like the weather will be much improved next week. With reports of migrants in the region already trickling in, things should start to get interesting soon.