Molt migrants

Today RRBO banded its first fall migrant, a Tennessee Warbler (Vermivora peregrina). While the majority of migrant songbirds undergo their autumn (prebasic) molt on the breeding grounds before proceeding south, Tennessee Warblers have a different strategy. Adults travel south from nesting areas in northern boreal forests, then stop part-way, and undergo or finish their prebasic molt. About 4% of the Tennessee Warblers banded in fall at RRBO are molt migrants.

This molt is a complete prebasic molt, and includes not just body feathers but also all the flight feathers. As you can see, this bird is pretty pathetic looking.


It was molting 4 of its 9 primaries (outer wing feathers), a few secondaries (the inner wing feathers), and all of its rectrices (tail feathers). Yes, it could still fly quite well!

At RRBO, we record the extent of molt on every bird. The number of body feathers being molted are scored on a 3-point scale, and we note the number of each molting flight feather. Over time, this gives us a great idea of the local annual timing of molt for the bird species we band.

Molt migration is common in waterfowl, and more common in songbirds in the western U.S. The other common molt migrant here is Swainson's Thrush (Catharus ustulatus); about 2% of RRBO's fall birds are molt migrants.

A little more information:

• An overview of bird molt -- Cornell's All About Birds
  
• Tennessee Warbler, featured bird -- Smithsonian Migratory Bird Center
  
• Tennessee Warblers are a classic example of a North American migrant that winters on shade coffee plantations -- Coffee & Conservation

Opening day

Today was the first day of RRBO's 16th fall banding season. Unfortunately, it was pretty breezy this morning, so I was only able to open a handful of our most protected nets. We have a strict weather policy that guides us as to when it's safe to open the nets. Young birds are especially vulnerable to getting wing sprains if they are caught in a net that is moving around a lot in a breeze.

And young birds are always the first order of business the opening days of a fall season. Today was no exception. Of the 18 birds that were captured this morning, only one, a robin, was an adult. The rest were youngsters, including 15 Gray Catbirds. This is our #1 species, with over 3200 banded since 1992 (nearly 40% are recaptured, many multiple times).

This is how it will go the rest of the week. I'll open different nets in various sections, and catch many of the resident birds. Then things will quiet down until migration begins in earnest.

Meanwhile, it's time to enjoy the catbirds!

Getting ready for fall banding

Many people don't realize how much work goes into just getting ready to start a banding season. I've been using one main site for banding for 16 years, but every season requires a lot of preparation of the net lanes. Weeds under and near the nets have to be eliminated and vines and shrubs that have started to reach closer to nets have to be removed. In order to keep the site as static as possible, woody growth is cut back in our old field portion of the site so that succession doesn't turn it into secondary forest. If the habitat changes too much, it would be difficult or invalid to compare current banding results with those of past years.

We do have a grounds department at the campus, of course, but apart from being busy keeping the more visible parts of campus looking nice and respectable, they do require payment for special work that they might do for other departments. Because RRBO is funded via grants and donations, I do this type of work by myself and with the help of volunteers.

All the rain here earlier this summer made growth particularly lush. I'll admit to being pretty depressed when I saw how much work had to be done before I could open the nets. It's not as if much of it can be done too far ahead of time! Starting early this week, it took me about 25 hours of my time, plus another 12 hours of help to get things shaped up. Many thanks to Rick Simek, Darrin O'Brien, and Mike O'Leary for their labor!

I wish I'd taken some "before" photos, but here are a couple of shots from the final efforts over the weekend. Here is some of our gear...you'll notice that we rarely use any power tools.

Here is a stretch that is in pretty good shape. You can see the furled up nets.

Another regular task is to make sure that the deer fencing which now surrounds the entire banding area is checked for holes and downed trees and repaired. The deer herd has grown so much in recent years that we've had to exclude them from the area. Each net costs over $100, and the deer were running through them or getting caught on the nets on a routine basis, destroying them. The deer on campus are quite fearless. Here are two on the other side of our fence (draped with grape vines). In the lower right corner, you can see the fine mesh of one of our open nets.
We hit one final snag as we were finishing the pruning. Darrin and I were cutting back a lot of overhanging grape vines, when he exposed a chest-high Bald-faced Hornet nets. He got stung on the chin, and we both fled as unhappy hornets chased us down the trail.

Much as I loathe it, I'll have to get rid of the nest before I can finish up and start banding. We'll be ready to open this week!

Small Canada Geese

In 2004, the 45th Supplement to the American Ornithologists’ Union Check-list of North American Birds split Canada Goose into two separate species: the larger forms remain Canada Goose (Branta canadensis) while most of the smaller forms are now Cackling Goose (Branta hutchinsii).  The Cackling Goose form most likely to be seen in Michigan is the former Canada Goose race B. c. hutchinsii, or Richardson’s Goose. The other small former Canada Geese are western birds that would be considered very rare in the east.  An excellent report on this is on the Ontario Field Ornithologists’ web site.  David Sibley’s website also provides great information.  In particular, read the information on neck size and voice, which from his discussion appear not to be as conclusive as some have been implying. There’s also a nice map indicating which races breed where.  The Ocean Wanderers web page, by Angus Wilson, includes photos, links to specific individuals being debated, and extensive literature citations.

What follows is some information on the identification of Canada Geese found in Dearborn, focusing on an interesting case of a “runt” Canada Goose from Canada.

The most common subspecies of Canada Goose in Dearborn is the Giant Canada Goose, or B.c. maxima.  This largest of the races was extinct in much of eastern North America, and in Michigan, at the turn of the 20th century, wiped out by hunting and habitat destruction.  Aggressive reintroduction campaigns resulted in the surplus of these big, non-migratory geese we see today.  This is the subspecies that nests in Dearborn.

During spring and (especially) fall migration, Giants are joined by the slightly smaller, somewhat darker-breasted migrant race B.c. interior.  Around the UM-Dearborn campus, many geese wearing orange neck collars can be found in the fall.  These birds have been banded on Akimiski Island, Nunavut, in James Bay (while closest to Ontario, all islands in James Bay belong to Nunavut, formerly Northwest Territories).  One neck-collared goose was seen by us in the fall of 1995 and again in the fall of 1998.  It was originally banded in 1990 on Akimiski.

There are other even smaller races of Canada Goose than  B.c. interior. An example is this goose, photographed by Jim Fowler, Jr. at Greenfield Village on 25 Oct 93.  Notice the pale breast, and small size compared to the nearby Giants.  This was probably B.c. hutchinsii (a.k.a. “Richardson’s Goose”), the smallest of the pale-breasted races.  They nest in the northern portion of Hudson Bay.

Next, look at this little dingy-breasted goose below, shown in these two pictures with one of  her two B.c. interior buddies that she hung around with from late September until early October 1998 on the UM-Dearborn campus.  This goose had a regular leg band and a colored leg band.  As it turns out, she was banded as a young female not yet able to fly on 15 Jul 98 on…Akimiski Island!  Since none of the small, dark-breasted races are known to nest in this part of Canada, I contacted the person who bands on Akimiski, Jim Leafloor of the Ontario Ministry of Natural Resources, for more information.

Dr. Leafloor explained to me that all the geese breeding on the island are considered B.c. interior.  This goose was banded on the north shore of the island, where the geese are smaller than other interiors due to low food availability.  The habitat has been degraded over the last two decades by high densities of nesting Canadas (seven times higher than on the nearby mainland and up to 300 times higher on the north coast of the island), use by migrant Brants (another type of goose), and especially increasing numbers of migrant and nesting Snow Geese.  Eggs of these birds when raised in captivity grow to “normal” size like their mainland counterparts.  Therefore, one should use caution assigning subspecies to varying sizes of Canada Goose seen in this region.

For more information on this very interesting phenomena, please see a paper Leafloor and his colleagues  published in the  journal The Auk:

Leafloor, J.O., C.D. Ankey, and D.H. Rusch.  1998. Environmental effects on body size of Canada Geese. Auk 115:26-33.

UPDATE: David Sibley has a post and photos on his site regarding recent research and evidence of hybridization between small (Cackling) Geese and larger Canada Geese. Please see Cackling-ish Geese; here is the paper he refers to:

Leafloor, J.O., J.A. Moore and K.T. Scribner. 2013. A hybrid zone between Canada Geese (Branta canadensis) and Cackling Geese (B. hutchinsii). Auk 130: 487-500.

Ruby-crowned Kinglet from Toronto

A (but not the) Ruby-crowned Kinglet
banded by RRBO

On 22 April 2005, I captured a banded Ruby-crowned Kinglet.  I was amazed to see that it was not a bird that I had previously banded.  The rule of thumb is that fewer than 1% of small songbirds are ever encountered away from the place they are banded.  And kinglets are one of the smallest songbirds, weighing in at around 6 or 7 grams, or the same weight as an American nickel and a dime.  They are so tiny, in fact, that properly-sized bands have only been made since 1993.  Prior to that time, the smallest band size had to be modified to fit them, and many banders released kinglets without banding them at all.

On 2 May, I received acknowledgment from the U.S. Bird Banding Lab that this kinglet was originally banded as a hatching-year bird (born the same year it was banded) on 10 Oct 2003 outside of Toronto, about 216 miles east-northeast of Dearborn.

In The Canadian Atlas of Bird Banding, I looked up the number of encounters of Ruby-crowned Kinglets, an encounter being a subsequent observation of a banded bird, dead or alive.  Between 1921 and 1995, with over 48,000 banded in Canada between 1955-1995 alone, the number of Ruby-crowned Kinglets encountered was only ten.  The Atlas noted this is one of the lowest encounter rates of any species.  While the U.S. has no similar publication, they do provide  simple tallies of numbers banded and encountered.  Although 127 Ruby-crowned Kinglets sounded more substantial, the encounter rate was actually only 0.03%.  What a special event this was!

The only other foreign encounters I’ve had here at RRBO were an American Goldfinch and a Sharp-shinned Hawk. Both were originally banded within 25 miles of here, and were caught by me within four months of the banding date.  Figuring this kinglet, too, was from nearby, I contacted other regional banders, but nobody could claim this diminutive traveler. Finally, I tracked down the original bander.

The location was Tommy Thompson Park (a.k.a. Leslie Street Spit),  man-made peninsula constructed from dredge and fill which juts out 3 miles into Lake Ontario from the Toronto shoreline. The kinglet was banded by the Tommy Thompson Park Bird Research Station (TTPBRS), a partnership between Toronto and Region Conservation and the Toronto Bird Observatory. The station began operation in 2003. Here is a great map showing the location of the station.

Kinglets, especially Ruby-crowned, are a  bread-and-butter bird for TTPBRS, making up 30% of all birds banded over fall 2003-2004.  This is not surprising. Other lower Great Lakes banding sites located along the shores of Lakes Erie and Ontario also band hundreds or thousands of kinglets: Long Point Bird Observatory, Prince Edward Point Bird Observatory, Braddock Bay Bird Observatory, and Haldimand Bird Observatory, for example.  At our inland site, we don’t even SEE as many kinglets as these stations band in a typical fall season. This seems to provide evidence that these little mites prefer to travel along shorelines rather than over water during their journeys between their nesting areas in northern spruce-fir forests and their wintering areas in the southern U.S., Mexico, and Central America.

The capture of this one bird provides only a single data point, and while it is a notably rare event, in itself it doesn’t deliver a big scientific wallop.  But this encounter is valuable in other ways.  Ruby-crowned Kinglet number 2310-75634  has provided a special connection between two bird research stations studying urban bird ecology — an underappreciated focus that often struggles for acknowledgment and recognition.  And it provides an opportunity for us all to marvel at the resilience of such a small creature, and how much we still don’t know about this common bird that flits among us, just passing by.