Bird Claws and Evolution

One of the interesting questions in bird evolution is whether early bird ancestors were primarily ground-based or tree-based. That is, did birds start on the ground and move up, or start in trees and move down?

A new paper in Current Biology proposes to answer the question by looking at the shape of birds' feet. The researchers first classed 249 bird species from seven orders according to their feeding behavior. Birds in group GB - such as herons, rails, and pheasants - feed on the ground and fly only to roost or escape predators. The other extreme, group V, contains vertical climbers like woodpeckers that forage only in trees. The middle groups - comprised of pigeons and cuckoos - have species that show both behaviors.

They then measured the claw angle on each bird's middle toe. The shape of a bird claw conforms to a circular arc. "Claw angle" refers to the angle between the radii extending from the center of this arc to the base and tip of the claw. What they found was that birds with a greater claw angle spent more of their time in trees than on the ground. This was true even within the pigeons and cuckoos.

The study suggests that claw angle can be a predictor of behavior in early birds and bird-like dinosaurs in addition to modern birds. Measuring the claw angle for extinct species presents challenges because of incomplete preservation. In those species where it can be measured or estimated from fossil remains, ancestral birds show greater similarity to modern ground-dwelling birds.

According to this indicator, early bird ancestors probably spent most of their time on the ground. Specializations for life in trees would have come later.

(Via Evolving Thoughts)

Election Day

The open space ballot issue that I mentioned on Monday passed, 536,581 to 457,237, along with an amendment to remove the phrase "idiot or insane person" from the state constitution.

Two other ballot issues failed - one on property tax relief and the other a bond issue for stem cell research. Both were targeted by anti-tax activists. The Asbury Park Press attributes the two defeats to "a cranky electorate." Apparently this is the first time in 17 years that a ballot issue was defeated in New Jersey.

Open Space Ballot Issue

Tomorrow is Election Day, and one of New Jersey's ballot issues for 2007 concerns funding for open space programs (pdf):

GREEN ACRES, FARMLAND, BLUE ACRES, AND HISTORIC PRESERVATION BOND ACT OF 2007
Shall the “Green Acres, Farmland, Blue Acres, and Historic Preservation Bond Act of 2007,” which authorizes the State to issue bonds in the amount of $200 million to provide moneys for (1) the acquisition and development of lands for recreation and conservation purposes, (2) the preservation of farmland for agricultural or horticultural use and production, (3) the acquisition, for recreation and conservation purposes, of properties in the floodways of the Delaware River, Passaic River, and Raritan River, and their tributaries, that are prone to or have incurred flood or storm damage, and (4) funding historic preservation projects; and providing the ways and means to pay the interest on the debt and also to pay and discharge the principal thereof, be approved?

INTERPRETIVE STATEMENT
Approval of this act would authorize $200 million in funding for Green Acres, farmland, Blue Acres, and historic preservation projects through the sale of State general obligation bonds. The Green Acres program preserves open space, including parks, fish and wildlife habitat, flood prone or affected areas, and lands that protect water supplies. It also funds park improvements and facilities. Of the total sum authorized: (1) $109 million will be used for Green Acres; (2) $73 million will be used for farmland preservation purposes; (3) $12 million will be used to fund a new “Blue Acres” program by which the State may purchase from willing sellers, for open space preservation purposes, properties in the Delaware River, Passaic River, and Raritan River basin floodways that are prone to or have incurred flood or storm damage; and (4) $6 million will be used for historic preservation purposes.

Along other benefits, the Green Acres program helps to preserve bird habitat. With so much former agricultural land being turned over to suburban development, the state needs to maintain open space where it continues to exist.

Local Birds

The pictures above and below come from Donaldson Park, which is close to my home. The brant have been sighted sporadically for about a week. The snow goose was new today. Both species are unusual at the site. On most days a few hundred Canada geese are the only anserines to be seen.

Goose Control

Border collies scare geese.

Wooden cutouts - not so much.