Sunday, December 27, 2009

Rockwood CBC: Lots of Refuge properties

Dawn at Humbug, looking from Jefferson Avenue toward the Trenton Channel Power Plant.
Since 2004, RRBO has been participating in the Rockwood Christmas Bird Count (CBC) by surveying the Humbug unit of the Detroit River International Wildlife Refuge (DRIWR). Last year I gave a little background on this count and our coverage of Humbug. This year, my husband and I once again counted at Humbug, but we also made whirlwind stops at five other units of the DRIWR that are within the Rockwood count circle. Several are fairly new units that are under restoration and the USFWS wanted to see if waterfowl were using them. Since the units are not open to the public and we have a special use permit for various projects, we offered to give them a look. Although it rained on Christmas Day, the next day most standing water had refrozen, limiting waterfowl use. That was probably not a bad thing. If the water had been open, we'd still be counting. As it was, this was more of a reconnaissance mission. Now we know the logistics, and can make recommendations on how the units should be covered in the future. We ended up walking over ten miles, but only tallied 44 species, owing to our quick work at most of the units and drive time between them. It was nice to see a total of 10 Bald Eagles at 4 of the 6 units. A Killdeer at the Humbug unit was probably our best bird. Great Blue Herons are always found in good numbers at Humbug, since there is always some open shallow water there due to discharge from the Trenton power plant just north of the property. We had 49 herons at Humbug, close to our record of 53 in 2004. We had another 19 roosting around the old quarry pond at the Gibraltar Bay unit on Grosse Ile (more on the units below). Sparrows in general seemed sparse, although we had two Fox Sparrows at the Brancheau unit. All of our 148 American Robins were at Humbug, feeding on Common Buckthorn, honeysuckle, and perhaps some rose hips. We completely missed any blackbirds, Carolina Wren, Cedar Waxwing (also missed by all other teams on the American portion of the count), and, sadly, American Crow. Very few crows were found on the count; this species does not seem to be recovering from West Nile Virus. Here is a run-down of the units. 
  • The Humbug Marsh unit is in Gibraltar and Trenton. At least half of the northernmost section was rehabilitated over the summer, and was either unvegetated or iced over, making that part quick work. I've attached a number of photos to this route, so hover over the map, and click on the first icon on the right to go into slideshow mode. We had 29 species here.
  • The Gibraltar Wetlands unit is very near Humbug, behind the high school at Jefferson and Woodruff Road in Gibraltar. Since it was frozen and we only had a few birds there, I did not include this in EveryTrail.
  • The Gibraltar Bay unit is the former Grosse Ile Nature Area (and a one-time Nike missile site) at the south end of Grosse Ile. We mostly went for waterfowl. 22 species.
  • The Fix unit was the furthest south we traveled, and is adjacent to the Fermi nuclear power plant in Monroe Co. These old farm fields have been planted with prairie and grassland vegetation, but were unvegetated this winter. We had 15 species here, including our only Winter Wren. More info here.
  • Walking a muddy dike at the Fix unit, with the cooling towers of the Fermi nuclear plant as a backdrop.
  • The Brancheau unit is north of Fix, on the other side of Swan Creek. These fields will also be planted for wildlife. A pump system has been installed to bring in water from Lake Erie so the fields can be managed for waterfowl or shorebirds. 17 species.
  • The Strong unit is just south of Pointe Mouille State Game Area. It also has old farm fields, and a large wetland bordered by dikes. The main dike is tall and grassy, with fields and woods on one side, and the wetland on the other. In many places Phragmites makes it hard to see into the wetland. We had our Fox Sparrows here, along with most of our American Tree Sparrows. We also had a Sharp-shinned Hawk, less common than Cooper's Hawks here in winter. 24 species.
The final dike walk of the day, this one at the Strong unit.
Realistically, covering all these units effectively takes more than one group of people. In the future, we will probably continue at Humbug and then concentrate on Gibraltar Wetlands and Gibraltar Bay.

Sunday, December 6, 2009

House Sparrow madness

The annual Christmas Bird Count (CBC) season is nearly upon us. The count in which I have participated the longest is the Detroit River MI/ON CBC, because the city of Dearborn is within the count circle. In 1995, RRBO started coordinating the Dearborn portion of the count, so there is intensive coverage in the city, and I keep a separate tally of the numbers in Dearborn before they are added into the count totals.

The CBC issue of American Birds, published by National Audubon, contains summary information and various analyses of CBC data. One standard article is the summary of highest counts of individuals for the U.S. Last year, the Detroit River count had a highest number of House Sparrows -- 4537 -- of any of the 1673 counts held in the U.S.

A quick look at my numbers showed that 77% of those House Sparrows were counted in Dearborn, and 3255 of them (72%) were counted in the various sunflower/wildflower fields planted by Ford -- 2400 in a single field, as I noted in my blog post last year. The Detroit River count also had the highest number of House Sparrows in the 2006-2007 count (5168), of which 57% were from Dearborn.

Does this mean that Dearborn, or the metro Detroit area, has the highest concentration of House Sparrows in the country? Hardly. Over the years, I've given some thought to the accuracy of counts of very common species considered "trash" by most birders, particularly House Sparrows, European Starlings, and Rock Pigeons. Let's face it: most people participate in CBCs and other bird counts in order to see what "goodies" might be found, not to spend the time it takes to get accurate counts of House Sparrows. I usually see numbers of mundane species coming into compilations as ballparked figures, especially in urban areas where counting these species can be tedious.

There is great value in being meticulous about counting very common species of birds. For nearly 20 years, I've conducted a Winter Bird Population Survey. I'm sure glad I took the time to count American Crows the first ten years or so (and there were often hundreds), because since West Nile virus hit town, numbers plummeted and have not recovered.

Despite whether you care about or like House Sparrows or other common birds, take the time to get reliable numbers on the various counts you participate in. These citizen science projects are some of the best sources of long-term population data we have, and their integrity may be jeopardized by "garbage in, garbage out."

In 2003, I co-authored a paper published in Ontario Birds summarizing the first 25 years of the Detroit River CBC. You can download a PDF copy here.

Thanks to Diane Newbery for publishing this House Sparrow photo under a Creative Commons license.

Thursday, December 3, 2009

RRBO bird banding video

This video was produced in 2001. Although I enjoy having people see me so much younger and thinner, it could use an update as it was shot on film and the digital conversion isn't very high resolution. Nonetheless, it gives you an idea of how and why we band birds. We use this to introduce students, program participants, and visitors to the banding process.

Banding at RRBO from Julie Craves on Vimeo.

Monday, November 23, 2009

"Look what the cat dragged in"

Only about 1% of banded small songbirds are ever recovered away from the place they were banded (much of the value of focused banding studies is in initial captures and within-season recaptures). So when a bander receives notice that one of their banded birds has been found somewhere else, it's a pretty notable event. Especially remarkable is when a migrant bird is banded on its wintering grounds and recovered where it breeds (or vice versa).

Thus it was astounding to learn that a Bobolink banded in Bolivia by the Vermont Center for Ecostudies was recovered three years later in Vermont, just miles from the bander's home, 4300 miles away! This was the first time a Bobolink banded on its wintering grounds had been recovered on its breeding grounds (or vice versa).

Tempering that news was the fact that this bird, having managed to have survived at least three migratory journeys totaling 35,000 miles in flight, was delivered dead to a homeowner by a house cat.

Often, banders do not know the exact cause of death of a reported bird...usually the report is only coded "found dead." Sometimes the person who finds the bird is more specific. Out of the last 40 or so birds we have banded here at RRBO for which we have received reports, only around 30% were found alive. The majority of those found dead did not specify a reason. Of those that did, nearly 40% were coded "caught by or due to cat." They included these birds:
  • A White-throated Sparrow banded on 26 October 1992 "caught by or due to cat" 5 May 1993 in Columbus, OH.
  • A Song Sparrow banded on 3 April 1995 "caught by or due to cat" 17 Jun 1995 just south of North Bay, Ontario.
  • An American Goldfinch banded on 10 May 2001 "caught by or due to cat" 12 May 2002 in Berea, KY.
(You can view a map and list of our out-of-state recoveries of banded birds here.)

The huge problem to birds and wildlife posed by outdoor cats is one that sparks a great deal of emotion. In fact, the blog post about the Bobolink pussy-footed around the issue to avoid the controversy. The bander pointed out that the fact that a cat brought home a dead bird is not concrete evidence that it killed the bird. However, it is generally believed that items brought home by cats are indeed prey killed by that cat, and numerous peer-reviewed scientific studies have used this behaviorial trait of cats to determine composition of prey items (see Barratt 1998, Churcher and Lawton 1987, and Woods et al. 2003 and the scores of references therein).

Don't get me wrong -- I love cats! I have two of my own, but they never go outdoors. Please, if you own a cat, keep it indoors. It is better for wildlife, and it is better for your cat.

For more information, you can see RRBO's keep cats indoors page, or visit the American Bird Conservancy's Cats Indoors! campaign web site.

Barratt, D. G. 1998. Predation by house cats, Felis catus (L.) in Canberra, Australia. I. Prey composition and preference, Wildl. Res. 24:263–277.

Churcher, P. B., and J.H. Lawton 1987. Predation by domestic cats in an English village, J. Zool. (London) 212:439–455.

Woods, M., R.A. McDonald, and S. Harris. 2003. Predation of wildlife by domestic cats Felis catus in Great Britain, Mammal Rev. 33:174–188.

Friday, November 13, 2009

Fall 2009 banding summary

I've posted a summary of the fall 2009 banding season at the RRBO web site. You'll find all the summary stats, a weather summary, top ten species banded, some commentary on deviations in numbers from previous averages, and notable within-season and between-year recaptures. There is also a brief explanation of how we calculate our capture rate, and our weather policy.

I've also updated our lists of the most commonly banded species. For the first time in RRBO history, American Robin unseated Gray Catbird at the top of the list.

Coming up, some results from our diet study.