Saturday, September 22, 2007

Morgan Mail Facility covers windows

The windows at the Morgan mail facility at 28th Street and 10th Avenue in Manhattan were not really windows overlooking the park. However, the windows overlooking Chelsea Park on 28th Street reflected the trees in the park. Birds ran into those windows at a high rate. For birds it was one of the deadliest places in Manhattan. The rates are apparently greatest during the migration seasons. We speculate that that is because the birds in migration do not really know their surroundings.

New York City Audubon volunteers counted the fatalities, and the post office agreed to coat the windows. Now, those windows are not reflective. We thank the post office. The Times story was on the first page of the B section below the fold. We thank the Times for the coverage.

The glass was the exterior facade of the building, but the glass did not act as windows. No one was looking out. One thing this illustrates is the popularity of glass facades today. Another is that it is easier to coat the windows with a non-reflective, black, vinyl film when no one's vision or light is diminished.

From 2002 through 2006, the New York City Audubon volunteers, led by Nicole Delacretaz, had counted 862 collisions. The three most common species were dark-eyed junco (junco hyemalis -, white throated sparrows (onotrichia albicollis - and ruby-crowned kinglets (regulus calendula -, according to the Times story. In other words, most of the birds that fly into the windows of buildings are little birds.

Thursday, September 20, 2007

1979 review

Review of Avian Mortality Due to Manmade Structures, by Michael L. Avery.

Daniel Klem in 1979 estimated 80 million birds killed per year or about one per building in the US, even though some buildings kill many more than one bird. That year, R. C. Banks put the number at only 3.5 million birds per year.

We think Klem's number is too low, and in any event there are many more buildings exist in the US now than did in 1979. Klem's calculation came in his doctoral dissertation at Southern Illinois. He has devoted a great deal of time and research effort to the topic of bird collisions since then.

Klem's work suggested that bird kills from collisions with buildings happen at all seasons and involving both clear glass and reflective glass. All kinds of birds run into buildngs and die---young and old, many species.

In addition, many other kinds of structures kill birds, including antenna and broadcast towers (and their guys) and overhead power lines.

Daniel Klem is currently working on a study for New York City Audubon using the Project Safe Flight data tht the volunteers have collected.

For many years, the effects of manmade structures on birds have been known. It has taken a long time for humans to take notice of these effects on the natural world.

Sunday, September 16, 2007

Birds' eyes

It says:
"In man, binocular vision is about 140 degrees out of a total of about 180 degrees. In a pigeon though the binocular area is only 20-30 degrees out of a total field of vision of 300-340 degrees. In many raptors and owls the situation is different. In these birds, as in many insectivorous birds, binocular vision, important in making judgements of distance, is more necessary and so these birds have their eyes more towards the front of their heads. This is most evident in owls where the total field of view is reduced to about 110 degrees with a binocular vision of 70 degrees. This is why owls turn their heads to watch you walk past. An owl can turn its head through over 200 degrees but cannot move its eyes in its head at all."

Maybe the lack of binocular vision makes littler birds more likely to fail to see glass for what it is.