Friday, September 27, 2013

Update on fall banding and fruit research

We are a little more than halfway through our modified fall banding. This year, we are concentrating on obtaining as much data as possible on the diet of fall fruit-eating birds. Many bird species switch from a summer diet made up primarily of insects to a fall diet heavy in fruit. This abundant, easy-to-eat food source is particularly important to migratory birds.

After our research showed that migratory thrushes gain weight during stopover at our campus study site, the next step was to pinpoint what resources these birds were using while they were here. Fortunately, there is a reliable and low-tech way to find out: identify the seeds in their poop. (You can find more details by following the links above.) We began collecting samples from thrushes in 2007, and from all birds in 2009. As of the end of last year, we have collected samples from 1,208 birds of 16 species. That's nearly 8,000 individual seeds, of which fewer than a dozen have gone unidentified (see the post on our seed website for more information on how we identify seeds).

Although these seem like big numbers, we need to make sure we have large enough samples sizes from individual bird species during certain time periods to make sure we can do proper statistical analyses. This way, we hope to answer a number of questions, especially whether or not particular species prefers certain fruits and if some fruits help birds gain more weight than other fruits.

This fall, to maximize number of samples we have modified our usual banding routine. When we have done comprehensive migration monitoring, we begin banding very early in the morning, which is when we tend to catch the most birds. Typically, birds captured the first hour or so have not had time to eat much, so we did not obtain many samples from them. This year, we are starting later in the morning and staying open later in the day, providing more overlap with bird foraging. We'll also aim to spend more hours during peak migration/fruiting periods -- late September to mid-October. Overall, this means we will probably band fewer birds, but get more samples.

So far over the 16 days we have banded this fall, roughly a third of all birds have contributed a sample. If we only consider those species most likely to eat fruit -- the primary species are American Robin, Gray Catbird, Cedar Waxwing, and the thrushes, but there are others that eat fruit less often -- the percentage jumps to over 65%. We have collected over 500 individual seeds.

Fruit crops fluctuate from year to year. Last year, the very early spring warm weather and the summer-long severe drought devastated fruit crops.  This year much more normal rainfall and temperatures has resulted in bumper crops of fruit. Some are especially impressive: branches are sagging under the weight of crabapples (both wild and ornamental) and the wild grape crop is nothing short of phenomenal, the largest I have seen in over 25 years.

Not a vineyard! Wild grape crop.
Many factors go into fruit choice in birds: fat, sugar, protein, and micro-nutrient content; size and color; pulp-to-seed ratio; and abundance are just a few. Not surprisingly, the dominant seed in our samples this fall so far is grape, present in 65% of samples. As the crop is depleted and other fruits ripen, the proportion will decline, but no doubt it will be higher than any other year so far. In past years the percentage of grapes has ranged from 5 to 19%.

Grape seeds provided by an American Robin.
This winter we will be doing our first statistical analyses of our samples to see what our data looks like. Stay tuned!

Monday, August 5, 2013

Summer banding 2013

RRBO has done very little summer banding over the years, as we have not had any research projects that require banding during the breeding season for quite some time. This summer, however, our catbird project had us out in the field catching catbirds...and of course we banded whatever else we caught while doing so.

First, we successfully captured enough catbirds to carry all 26 of the geolocators obtained through Dr. Bowlin's grant. On campus, we did targeted netting in a location near Fairlane Lake by setting up a few nets in the midst of the territories of several pairs of catbirds. I also set up our usual fall banding area over a month earlier than usual and the bulk of the catbirds were banded there. In total, at UM-Dearborn we banded 21 catbirds: 7 adult males, 5 adult females, and 9 hatching-year birds. We also captured 5 catbirds (2 adult males, 2 adult females, and 1 hatching-year bird) at a remote site off-campus in Washtenaw County.

Aside from catbirds, we banded 72 other birds of 16 species. The highlight was two hatching-year Orchard Orioles caught in the same net on July 24. This doubles the number of Orchard Orioles banded on campus since 1992; the other two birds were adults caught in the spring. This is an uncommon but annual species here. This year, they seemed more numerous than usual, and apparently nested on campus or close by.

One of the young Orchard Orioles banded this summer.
An adult female American Redstart banded on July 17 was a surprise. There was no physical evidence that she had nested, but it was only our second July record.

We tend not to band many Yellow Warblers in the fall (our 21-year average is 3) because they start to move south quite early in the season. A total of 5 for our modest summer banding was a nice number.

My impression is that House Wrens are having a good year, and we banded a dozen. This is just under our fall seasonal average. We'll see how the fall numbers look.

Our fall banding season begins in mid-August. We will be concentrating on maximizing the data we obtain on the fall diets of migrant birds. We will be banding fewer but longer days, and focus on times of peak bird movement and wild fruit set. After last year's drought-induced fruit crop failure, most fruiting plants are loaded this year. Because we had prolonged cool weather this spring, ripening is a little late, but it should be a very interesting season.

Wednesday, July 24, 2013

Update on catbird research

In 2011, RRBO embarked on a collaborative research project with Dr. Melissa Bowlin, a member of the UM-Dearborn Natural Sciences faculty. Dr. Bowlin had a number of geolocator devices left over from a previous project. Geolocators are tiny devices that measure light levels. This data can be used to calculate latitude and longitude when compared with sunrise and sunset times and light levels at noon in different geographic locations. They can be placed on a bird, and if the bird can be recaptured the following year, the data can be downloaded and migration routes, pace, and destination can be determined. You can read a full explanation of how geolocators work and the goals of the project on the RRBO web site.

In 2011, we placed 11 geolocators on catbirds. In spring 2012, we resighted 3 birds with devices, and recaptured 2 of them.

We did get data from the 2 retrieved geolocators. As it turns out, the data was not high quality; not only do catbirds spend a fair amount of time in shaded areas, but the light-collecting stem on the devices we used was a little short and we suspect ended up being covered by feathers a good amount of the time. Without a good reading on the light, the data from one was deemed inaccurate. The other bird seems to have wintered in Florida -- which is unexpected as preliminary data from other researchers (based on banding and geolocators) indicates that Midwestern-nesting birds winter in Central America. We put the geolocator on this bird on September 29, 2011, it appears to have left Dearborn on October 12, arrived in Florida on the October 16, left the wintering grounds on March 30, 2012, and arrived back in Dearborn on May 8, 2012. We recaptured it May 17, 2012 (here's the story of its recapture).

In fall 2012, we put 2 more geolocators on birds, but did not see any birds with geolocators in spring 2013, despite a lot of patient observation of the catbirds on site.  Earlier this year, Dr. Bowlin received a grant to purchase 26 new geolocators with longer light-collecting stems better suited for catbird study. You can see the older device below in the top picture, and a newer one with the longer "stem" in the bottom photo. They both weigh the same, 1 gram including the harness.

During my spring bird surveys, I spent time locating territories of catbirds that I thought would be easiest to catch and re-find next year. Two of Dr. Bowlin's students, Kelli Gutmann and Quen Watkins, then staked out these birds to see where they tended to hang out so they could be captured with a minimum of fuss. I also set up our regular fall banding site, and began banding a month earlier than usual.

We have had good success so far this summer. We have put 14 geolocators on resident catbirds. Even more exciting, one of the birds I recaptured was a male with a geolocator from 2011! The batteries on the devices can last for 2 years, so if it is good quality we could conceivably get 2 years of data from it. 

We feel confident we can catch enough catbirds for all of our devices, and look forward to finding out what routes they use on migration; if the routes differ for males and females, or adults and young; where the birds stop during migration and how long they stay at each stopover; and where they spend the winter. Stay tuned for more updates!

Friday, July 19, 2013

Yellow-headed Blackbird in Dearborn

Last week, a local man, Ron Prowse, came in and spoke to a co-worker (I was off campus) regarding an unusual Blue Jay-sized bird he had seen at his bird feeders on June 12. He provided this photo.

Photo by Catherine Prowse. Not to be used without permission.
Based on the picture and the description he provided my co-worker, we conclude that this is a Yellow-headed Blackbird (Xanthocephalus xanthocephalus), a new species for the Dearborn bird list!

Yellow-headed Blackbirds are typically a more western species that nests in the grasslands and marshes of the Great Plains. They have nested regularly in Michigan in small numbers for at least 50 years. The most notable small breeding populations are in the Saginaw Bay area. The closest location they are typically found is at Pt. Mouillee State Game Area in Wayne/Monroe Cos.

Map of eBird sightings in the Lower Peninsula of Michigan
for the year 2013.
If I were expecting to see a Yellow-headed Blackbird in Dearborn (which I was not!), I would presume I'd see it during spring migration. A July date is quite interesting, as it would be at a point in their breeding cycle when young are leaving the nest. This wandering bird could be an adult whose nest failed elsewhere, or a non-breeding adult. The most recent sighting at Pt. Mouillee put in eBird was on July 13.

The observer's location not far from the TPC Golf Course along the Rouge River. This portion of the river is channelized, but there is a small wetland on TPC property adjacent to the channel that does have nesting Red-winged Blackbirds and waterfowl. Perhaps the bird was/is hanging around there. Yellow-headed Blackbirds are very tied to cattail marshes for nesting, so the habitat is probably inadequate for that, but it might be a good place to pass the summer.

View Larger Map

Hats off to the Prowse's for this great observation!

This is the 258th species documented for Dearborn. For an interesting historical perspective on Yellow-headed Blackbirds in the state, see Why are Yellow-headed Blackbirds rare in Michigan? by Richard Brewer.

Tuesday, April 30, 2013

Let's talk turkey

Turkey track found at the north end of Fairlane Lake
next to my notebook for scale.
(Update at end of post!)

On April 16, a Wild Turkey was reported on campus. It was seen twice at Fairlane Estate, once at the feeders behind the EIC, and I found a track at the north end of the lake (right). For one morning, this bird really got around!

Wayne County has had many turkey reports in the last few years, mostly from Sumpter Township and nearby areas in the southwestern part of the county. These probably originated from the successful re-introduction and restocking of turkeys by the Michigan Deptartment of Natural Resources in northern Monroe Co. Back when RRBO was working on the Michigan Breeding Bird Atlas, we obtained data on the relocation of nearly 150 turkeys from Barry, Cass, and Washtenaw counties to Monroe County (a few to St. Clair County) between 2002-2005.

Over the past winter, it seems like turkeys were on the move. Reports came from Belle Isle and near Willow Run airport. This spring, there more reports from Willow Run and environs, and on April 26, someone photographed a turkey on a fifth-floor window ledge near Ford Field in downtown Detroit! I suspect Detroit-area birds come from Canada, including from Fighting Island in the Detroit River, where a large flock has been released. And now Dearborn joins the list of Wayne County communities with a turkey sighting.

I did not include Wild Turkey in my book on Dearborn birds; they did occur here historically, but the book included only those species with specific documentation. Most long-time Dearborn residents are familiar with the pioneer memoir of William Nowlin, The Bark Covered House. Although Nowlin's circa 1840 homestead was just outside Dearborn city limits, it no doubt depicts the turkey situation in the region at the time.  In one passage the author notes,
"Sometimes I would rise early in the morning and go out of the door just at daylight. ... I would listen to see if I could hear the gobbling of the wild turkeys. I hardly ever failed to hear them, sometimes in different directions. I frequently could hear two or three at once."
Turkey poop in my Washtenaw Co. yard with the
toe of my boot for scale. Kind of like Mourning
Dove droppings, but lots bigger.
Alas, by the turn of the 20th century, Wild Turkeys were pretty much gone from Michigan, primarily from overhunting. In the 1950s, a program was initiated to reintroduce turkeys into Michigan. The state population is now around 200,000 birds. An interesting side note: occasionally, one sees grayish or whitish turkeys, which some people believe means wild turkeys have interbred with domestic turkeys. In fact, this is an uncommon genetically-linked color form that was brought to southern Michigan from turkeys relocated from Iowa in the 1980s.

Perhaps ironically, the MDNR is now moving turkeys from southern Michigan to northern Michigan to both bolster populations and to rid urban areas of "nuisance" turkeys. Admittedly, turkeys are very large birds that can do a bit of damage scratching in gardens. And their poop is pretty big, though not as voluminous and messy as goose poop, in my opinion. But despite periodic horror stories, Wild Turkeys are pretty wary and urban areas really don't provide adequate habitat for them.

Nonetheless, the situation reminds me of all the efforts to re-establish and foster populations of White-tailed Deer or Canada Geese, which are now over-abundant and troublesome in many urban areas. I wonder if stories like this will become more common, and what the fate of Wild Turkeys in populated areas will be if their populations flourish.


A (the?) hen turkey was seen again along Fairlane Drive near the old stone cottages on May 2, where Dr. David Susko took the photo at left. There was a very large outdoor event on campus that day, so she probably didn't hang around, but this seems to indicate that she may be hanging around the area.