I and the Bird #46

Corey of lovely dark and deep, a blog about birding in upstate New York, is hosting the latest I and the Bird. Visit him for I and the Bird #46: Birders Become Birdered.

A study of common scops owls established that owls use the pitch of their hoots to advertise their body weight.

The authors have analyzed several hundreds of hoots recorded from 17 territorial males and demonstrated that the pitch of the vocalization reflects the body weight of the male: the heavier the male, the lower the pitch of his hoots. In order to see whether this information is actually used by male owls during territorial interactions, the authors conducted a series of playback experiments (commonly used in studies of animal communication in order to assess the function of vocal signals), monitoring the reaction of subjects to the broadcast of vocalizations.

To do this they modified the pitch of several hoots, creating stimuli that mimicked the hoots given by males from a range of body weights. They then played back these recordings to males with established territories, and observed and quantified their response (a combination of approaches and vocal responses). The results show that male owls respond more strongly to the high-pitched calls that simulate lighter individuals, confirming that territorial males attend to pitch information advertising body weight in the calls of their competitors. The authors also found that the territory owners give slightly lower pitched hoots in response to calls mimicking heavier males, probably indicating that they attempted to sound heavier when challenged by more threatening individuals.

"The fact that owls are essentially active during the night puts a strong emphasis on acoustic communication as a means of assessment, both during male competition and during mate choice," says Loïc Hardouin who recently completed a PhD on acoustic communication and territoriality in owls. "The next step is to see whether females use these quality cues when they choose their mating partner."

You can find the abstract here.

News and Notes

These are a few stories that showed up after my last Loose Feathers post.

Alewives and blueback herring are able to spawn in the upper reaches of Rock Creek again. Habitat mitigation money from the Beltway bridge project made it possible to design and build ways for fish to swim around artificial obstacles blocking the stream. The most serious obstacle was the dam at Peirce Mill, which is now bypassed by a fish ladder. Biologists from DC Fisheries and Wildlife have found some alewives upstream from the Peirce Mill dam already, but most fish have not caught on yet.

Last Saturday, there was a cleanup along the Anacostia River watershed. The cleanup was sponsored by several organizations, including the National Wildlife Federation and the Earth Conservation Corps. It removed 20,000 pounds of garbage from the river banks and tributaries. Volunteers uprooted many invasive plants as well.

The X Prize Foundation is offering a $10 million prize for someone who can build a car that gets 100 miles per gallon. Given that American vehicles currently average about 20 miles per gallon, and even the best top out at about twice that, such an improvement would be remarkable. One of the requirements of the competition is that the winning vehicle be commericially viable since the goal is to produce designs that will lead to more efficient vehicles being sold.

A California condor has laid an egg in Mexico for the first time since the 1930s. The egg is about 45-50 days old, meaning that a chick should hatch soon. The nest is located on the Baja peninsula.

On Sunday, someone reported a goosprey from Huntley Meadows.

Supreme Court Rules on Greenhouse Gases

The Supreme Court issued its decision on whether the EPA can and should regulate greenhouse gas emissions as pollutants. The court ruled against the administration and asked the EPA to reconsider its opposition to regulating carbon dioxide.

The court had three questions before it.

--Do states have the right to sue the EPA to challenge its decision?

--Does the Clean Air Act give EPA the authority to regulate tailpipe emissions of greenhouse gases?

--Does EPA have the discretion not to regulate those emissions?

The court said yes to the first two questions. On the third, it ordered EPA to re-evaluate its contention it has the discretion not to regulate tailpipe emissions. The court said the agency has so far provided a "laundry list" of reasons that include foreign policy considerations.

The majority said the agency must tie its rationale more closely to the Clean Air Act.

"EPA has offered no reasoned explanation for its refusal to decide whether greenhouse gases cause or contribute to climate change," Stevens said. He was joined by his liberal colleagues, Justices Stephen Breyer, Ruth Bader Ginsburg and David Souter, and the court's swing voter, Justice Anthony Kennedy.

Update: See Gristmill's take: What does the Massachusetts case mean?

Early Spring Birding at Kenilworth

This morning I birded at Kenilworth Aquatic Gardens for the first time in a while. The gardens were quiet as usual. Except for the walk to and from the Deanwood Metro station, and the occasional low-flying helicopter, I would hardly know I was in a city while I was there. Today was overcast and cold, so the birds seemed a bit less active than yesterday.

The area around the lily ponds was mostly quiet, but the activity picked up near the boardwalks. I spotted a bald eagle as it landed in some trees on the other side of the marsh. Near the boardwalk junction, two eastern phoebes were gathering nesting material. It looked like they were building a nest under the boardwalk, but I cannot be sure. Also near the junction, I was surprised by a beaver, which was swimming and slapping its tail on the water close to the boardwalk.

Out in the marsh, a couple ospreys called and wheeled overhead. Swallows also have returned to the marsh. I saw more northern rough-winged than tree swallows. A few northern rough-winged swallows flew so close to the boardwalk that my binoculars couldn't focus on them. Wood ducks were busy flying back and forth. A few jet-black double-crested cormorants were perched on a log.

As I started down the river trail, a small flock of northern pintails flew overhead. (This was the first time I have ever seen pintails in D.C.) On either side of the trail there were singing sparrows - mainly white-throated, song, and swamp. Carolina chickadees were singing, and even a winter wren broke into song. Close to the end of the trail, a hermit thrush sang, but weakly, and I saw the largest group of yellow-rumped warblers that I have seen in the District all year.

Sure enough, northern flickers were abundant, though I did not see as many as I saw yesterday at the Arboretum.

SPECIES SEEN: 40

Double-crested Cormorant
Great Blue Heron
Canada Goose
Wood Duck
Mallard
Northern Pintail
Osprey
Bald Eagle
Red-tailed Hawk
Killdeer
Ring-billed Gull
Rock Pigeon
Mourning Dove
Yellow-bellied Sapsucker
Downy Woodpecker
Northern Flicker
Eastern Phoebe
Tree Swallow
Northern Rough-winged Swallow
Carolina Wren
Winter Wren
Northern Mockingbird
Eastern Bluebird
Hermit Thrush
American Robin
Carolina Chickadee
Blue Jay
Fish Crow
European Starling
House Sparrow
Yellow-rumped Warbler
Chipping Sparrow
Song Sparrow
Swamp Sparrow
White-throated Sparrow
Dark-eyed Junco
Northern Cardinal
Red-winged Blackbird
Common Grackle
Brown-headed Cowbird