Bird Brains and Migration

A new study by Spanish scientists has found that non-migratory birds tend to have larger brains than migratory birds. Resident birds are more likely to find alternate sources of food and to try foraging techniques. Some European blackbirds have been observed using sticks to clear snow away from potential food sources. This provides an important advantage for resident birds during the colder months when food is scarce. Migration is an extremely stressful and hazardous journey so species that can adapt to the cold are better off staying put. There does seem to be some question about the cause and effect of the relationship between brain size and migration. Some seem to think that migratory birds are forced to migrate because they are not smart enough to adapt, while others argue that the small brain size is necessary to reduce the energy needed for the long migratory flight.

Birds and White-tailed Deer

The latest issue of Audubon magazine has an article on the problems caused by the white-tailed deer population boom. The problem has been apparent for years now; people who drive on rural roads (or even suburban roads in some places) are in constant risk of collision with a deer running across the road. The population is so large that deer are penetrating cities as well. There is a substantial herd in Rock Creek Park, including at least one gimpy individual. The deer in this herd have become relatively unafraid of humans.

The damage caused by large deer herds is not just a matter of traffic safety. As herds expand they begin to destroy the understory that other organisms need. This has a particularly heavy impact on birds:

In Warren, Pennsylvania, a 10-year study by the U.S. Forest Service determined that at more than 20 deer per square mile, there is complete loss of cerulean warblers (on the Audubon WatchList as a species of global concern), yellow-billed cuckoos, indigo buntings, eastern wood pewees, and least flycatchers. At 64 deer per square mile, eastern phoebes and even robins disappear. In heavily settled parts of Pennsylvania, where hunting pressure is light or nonexistent, it's not unusual to have more than 75 deer per square mile.

This situation is pretty grim. Many bird populations are in serious trouble even without extra pressure from the deer population. Forests and parks that have been heavily impacted by deer browsing are easily discernible once you know what to look for. In such places you can see long distance and the understory consists mainly of barberry bushes and other invasive species that can resist deer.

Hunting is still the most effective way to control the population. Contraception has apparently proved impractical and relocating deer simply moves the problem around without a real solution. But hunting is fraught with problems. First there is the safety issue. Deer overpopulation is most heavily felt in areas where deer and humans come into close contact, and these areas are frequently off-limits to hunting because of the human population density. There is too much likelihood of human casaulties.

Then there is the political opposition to using hunting as a way to control the deer population. The groups that are most visible in the opposition tend to be animal rights activists. But it is not the animal rights activists that have real clout on these issues. Oddly enough, the real political heavyweights are the hunters, especially in states where the fish and wildlife funding comes primarily from hunters. The experience in Pennsylvania is instructive: the program of increased hunting - and especially hunting does - was effective enough to make deer more afraid of humans, and thus harder to hunt, and the hunting lobby howled that there were no longer enough deer. Whether this really reflected a population decrease is questionable:

Data of a less anecdotal nature were collected last fall by the U.S. Army Corps of Engineers at its 22,000-acre property around Raystown Lake, in south-central Pennsylvania. Hunters were complaining bitterly that the deer had been shot out, but an infrared aerial survey revealed that the deer were merely doing what they do when they're hunted—evading hunters. One area contained 80 deer per square mile, and the average was 51—roughly three times what Alt and his management team had determined to be environmentally acceptable.

The author (and presumably the Audubon Society) proposes changing the funding structure in states like Pennsylvania to decrease the fiscal influence of the hunting lobby. Funds could come from a dedicated tax, as was done in Missouri and Arkansas, or from private donations. Whether this will happen is another story:

The hunters and the commission reject all outside funding proposals because they want to keep the power where it is. Mohr, for example, is quoted by the York Daily Record as saying: “The problem with listening to all the special-interest groups is that, once you compromise, they've already gotten into your fort. Once nonhunters are telling you what you're going to accept, our days are over.”

This strikes me as one obstacle to finding common cause between environmentalists and hunters - a strategy currently being hyped by some on the left. The Sierra Club and Kos have both presented such an alliance as critical to the future of the environmental movement. To a certain extent I agree with this position. There are areas where both can find common cause, especially when it comes to habitat preservation. But it seems to me that such an alliance will represent an uneasy truce more than a close partnership for the foreseeable future.

Mall Birds

This evening there was an osprey hunting over the reflecting pool in front of the U.S. Capitol. I have seen one there before so I imagine it was finding something, but I do not know what fish would survive in that pool. Perhaps people abandon goldfish there.

Blog Maintenance

I am adding an email address to the sidebar, but I am not going to give a mailto link to prevent automated spam crawlers from getting at it. Let's see if this works.

I have been adding links to the sidebar as well, and there are a few more that will probably go up within the next few days.

Trilling Calls

As I mentioned in a previous post, I am still learning the ins and outs of birding by ear. I have most of the basics down, and I am building a good aural library of the easier calls. But some calls still leave me stymied. One of the hardest groups for me to nail down is the group of trill songs. There are differences, to be sure, but these differences sound much less certain out in the field than they do on the CD. So when I hear one of these trill calls coming from a tree, I am left scratching my head and trying to figure out whether the call is "dry" or "musical." And of course, the bird making the call is nowhere to be found, despite much searching with binoculars. On a hot summer day in D.C., two trilling species can safely be eliminated - dark-eyed junco and swamp sparrow. Chipping sparrow tends to be the most common breeding species of the remaining possibilities, but pine warbler and worm-eating warbler cannot be dismissed out of hand, as they have bred here in the past. (In fact, there is a probable breeding worm-eating warbler in SE DC this summer.) In most of these situations, I try to find the bird for a while, and then move on, frustrated. This happened to me several times today. I could only confirm the chipping sparrow as the source of a song in the Asian Garden; I did not discover the sources of the calls I heard elsewhere in the arboretum.