June 7, 2011
On the weekends and whenever I can get away from the office, I like to putter in my garden. And keeping me company there are a host of catbirds, who seem to be whistling all manner of song-like calls while I work. The catbird is one of the more successful songbirds and according to the Smithsonian Migratory Bird Center the species has “adapted well to the widespread urban and suburban habitats created by people.” This weekend, while I was whistling along with my catbird friends, a visitor wandered by. Leah Culp, sporting a Smithsonian Institution baseball cap and carrying a clipboard and looking very field study in green hiking pants, is in the area on a fellowship this summer from her native Maine. She’s conducting research on the catbird and asked permission to check out my backyard friends.
The 8-inch tall gray song bird is easily recognized not only for the racket it makes beginning around O’dark thirty and lasting into the evening, but also for the dark gray cap it sports on his head. In my garden, the other day, I watched two males work out some dominance issues as they flew in aerial combat, swooping low over my head and weaving in and out of my trellis. Recently, the catbird (Conatella carolinesis) was the subject of a small Smithsonian study that made some big headlines when it was reported that neighborhood cats were the cause of high numbers of deaths to the catbird young, especially when the vulnerable fledglings leave the relative safety of their nest.
The study, which looked at three neighborhoods in the Washington, D.C. area reported a nearly 80 percent mortality rate for the birds caused by predators, of which nearly half could be attributed to cats. Previous studies had shown that native animals such as hawks, snakes and chipmunks were the sworn enemy of the hearty catbird—which always manages to somehow to raise up at least enough young to repopulate its numbers. But now, the evidence seemed to be saying even the catbird would not be able to hold its own against the large numbers of free-ranging cats. Cat lovers were dismayed and even called into question the study’s findings. A group called Alley Cat Allies started a Facebook page called “Breaking Down the Bogus Smithsonian Catbird Study.”
Culp’s boss, Peter Marra who headed up the earlier study responded with an op-ed piece in the Washington Post. “I love cats,” he wrote, and then laid down some pretty strident reasons for why we need to be a little more vigilant about where our cats go at night and what they do.
Marra, who is now at work confirming the results of the catbird study in a larger analysis, called me yesterday to fill me in on the details. “We have nearly 70 million to 120 million free ranging cats in the U.S.,” he said. “And these are ferocious predators. The animals here [the catbirds] didn’t evolve with them and so they have no defenses.”
Marra researches urban ecology issues for the Conservation Biology Institute at the National Zoo. And Culp is one of a dozen or so field study participants who have fanned out across ten neighborhoods in Virginia, D.C. and Maryland, to monitor 15 to 20 pairs of catbirds. Culp said I had the makings of a nest in my rhododendrum. “They love the rhododendrum,” she told me. I call that bush Aunt Rhody and it is a source of particular pride in my garden.
The team has located field cameras at various locations that are recording the nighttime actions of foxes, coyotes, raccoons, “and even kids,” jokes Marra. One cat named “Tigger,” he says was caught “red-handed” on the camera, not with a catbird, but with another predator, a chipmunk, in his mouth.
“We are trying to see if this really is a significant part of mortality. Is it crows, and raccoons,” Marra says, “or cats.”
I asked him why the catbird and Marra told me that the noisy little guy is robustly abundant and that it can step up to be a good indicator species for other more elusive songbird species. “We can get the sample sizes we need to ask the questions we want to ask,” he says, because the birds nest in urban and suburban areas and are “easy to find, easy to catch and you can put radio transmitters on the young.”
Marra says he’s even been able to draft some cat owners to provide data. They have allowed the researchers to strap cameras around the animals’ necks so that the team can monitor their actions.
And while many cat advocates would like to argue that cats are part of the ecosystem and should be allowed to roam free, Marra says that he and his team are working to better understand how “we can best maintain a diversity of wildlife within human dominated systems.”
The cat Marra says, is like any invasive species in the landscape, which does causes “considerable damage.”
“We need to quantify the damage they do and to know if it is significant,” he adds. “And then we need to figure out how to come up with solutions.”
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