Global Warming

One of the arguments frequently used against global warming was that weather balloon data showed slight cooling in the troposphere (the lowest level of the atmosphere), especially in the tropics. Three new studies, appearing in Science, show that when errors in the data and calculations are taken into account, the weather balloon data actually shows a warming trend, in conformity with computer models.

“These papers should lay to rest once and for all the claims by John Christy and other global warming skeptics that a disagreement between tropospheric and surface temperature trends means that there are problems with surface temperature records or with climate models,” said Alan Robock, a meteorologist at Rutgers University.

The findings will be featured in a report on temperature trends in the lower atmosphere that is the first product to emerge from the Bush administration's 10-year program intended to resolve uncertainties in climate science.

While this vindicates global warming research, it remains unclear what practical effects it will have. The current administration seems as stubbornly committed as ever to ignoring the evidence of global warming, which has been public for more than a decade. Just this summer, aCongressional committee began harrassing some reasearchers, a move cheered by right-wing sycophants. As long as the political climate remains in its current state, I see little hope for any large-scale change on the global warming front.

Barred Owl

Much of the time, birding consists of looking over familiar species in familiar circumstances. But there are a few moments that make one say “Wow!” These moments are the reason why we bird. Coming face-to-face with a barred owl is one of those moments.

I have had the good fortune to have this happen twice during the last summer. Now before this summer I had never seen a barred owl before. On a couple field trips other people had seen or heard one, but it was always a matter of not recognizing the call before it stopped, or a bird flushing and then disappearing into the woods. Owls are among the most difficult birds to find; perhaps only rails are more elusive.

Those frustrating experiences changed this summer. When I was in Tennessee earlier in the summer, I had the opportunity to bird a small park near Nashville. Another birder headed in the opposite direction mentioned that there was an owl further up the trail. I expected to have to search carefully for this bird, but instead I saw a barred owl sitting out in the open a stone’s throw from the path. Now this park has very heavy foot traffic, and many people passed by the owl and stopped to look. Despite all the attention, the owl just sat there quietly, occasionally turning its head to look coolly at its admirers.

Last week’s sighting was a similar experience. I was at the Great Swamp in New Jersey with some family members when one found a barred owl sitting in a tree. It was trying to ignore the scolding robins that pestered it.We all stood very still while watching it at close range; it may have been closer than the bird in Tennessee. No binoculars were necessary at this range! When it finally flew to a more obscure perch, we left it alone.

The barred owl, which is native to eastern North America, occurs primarily in wooded swamps and river bottoms with dense thickets. It nests in hollow trees or on nests already built by other birds. It preys primarily on small mammals, and it may hunt either at night or during the day. It is common, if uncommonly seen, and it has been increasing its range in recent years.

The barred owl’s success has brought it into conflict with the endangered spotted owl, its close relative. Barred owls have expanded their breeding territory into western states, where they outcompete spotted owls. This has led some officials in California to consider shooting barred owls where the two species come into contact.

Barred owls have personality. Their call, which may be heard during night or day, is distinctive (“who-cooks-for-you, who-cooks-for-you-all?”). Their eye disks make them appear alternately somewhat clownish, somewhat friendy, or somewhat sleepy. The neck ruff looks like a scarf wound about the bird’s shoulders. The streaks on their belly give the appearance of a pinstriped suit. (See Owl Pages for pictures and a recording.) What really stands out, though, are the eyes. Unlike most birds, owls have both eyes facing forward, an adaptation to help it find prey. This facial feature makes it much easier to anthropomorphize owls than other birds. Looking into a barred owl's deep brown eyes, one can imagine seeing a person looking back.

It is easy to forget when looking at the barred owl that it is a carefully tuned killing machine. The feathers on the leading edge of its wings are adapted to make no sound in flight so that its prey will be caught unaware. Like all owls, it has asymmetrical ear openings to pinpoint the location of any sound. Its talons and bill are sharp and merciless. But in the presence of a barred owl, these adaptations are not on my mind. Perched on a branch a stone’s throw away, it stares back like one of us.

Mercury and the Wood Thrush

Biologists in New York state are netting wood thrushes in the Catskill Mountains and testing them for mercury levels. The study is meant to assess the future health of the New York City water supply. Mercury is already present to some degree within the reservoirs due to pollution drifting from coal-fired power plants in the midwest. (Thus the state warns against fish consumption from lakes and streams even in the Catskills.) There is danger that levels of mercury and other contaminants could increase if birds like the wood thrush decrease due to mercury poison. Thrushes are one of many species that keep the insect population under control; barring that control, the ability of forests to filter pollutants out of the watershed could be greatly reduced.

Some Washington Notes

* Last week, the Washington Post had an article on attempts to quantify the benefits of urban trees in monetary terms. The effect is most noticeable in weather as hot as we have had for the last few weeks; shade can lower air conditioning costs and reduce street-level temperatures. Trees also help filter pollutants out of the air. Currently 28.6 percent of Washington is shaded by trees, a decline from the 37 percent canopy measured in 1973.

* The Casey Trees Endowment Fund, one of the local groups publicizing such cost-benefit analysis, maintains a tree map that allows you to see how the trees on your block are faring. According to this map, my block has 7 healthy trees, 11 unhealthy trees, and 3 dead trees. Looking at the gingkos that line my street, I would agree with their assessment. Somehow they missed the tiny ailanthus growing out of the rooftop next to my window.

* The DC Sierra Club has notes on ten trees not to plant. If I could add an eleventh tree to that list it would be the gingko, which provides little shade, does not hold up well during storms, and drops foul fruit in autumn. Unfortunately quite a lot of our street trees in D.C. are gingkos, including most of the trees on my block; my hope is that as these die, they are replaced with better options.

* I found a page (with photographs) about Kenilworth Aquatic Gardens, one of my favorite birding spots in D.C. The page is part of the Birding America website, which includes trip reports from many other sites across the United States.

* Finally, one blogger is trying to emphasize the positive (and quirky) aspects of living in Washington with his DC-Streets blog.

Beginning Birding

Sophia Dembling outlines some of the frustrations that can beset a beginning birder in a Chicago Tribune article. Learning to see detail, catching good looks at fleeting shapes, and distinguishing among similar species are all difficult. But the important thing to remember is that birding should be fun, and if that means watching unnamed birds rather than identifying, there is no shame in that.