October 2006

For the Birds – Long-billed Bird Syndrome

A bird’s beak is a remarkable structure. The shape of the beak tells us much about the type of food a bird eats. It’s obvious that a hawk’s bill is adapted for tearing, that a heron’s bill is adapted for spearing and that a finch’s bill is adapted for crushing seeds.

The lower jaw or mandible of a bird is composed of a pair of dentary bones that fuse at the tip. The upper jaw or maxilla is made up of nasal bones near the base and premaxillary bones at the tip.

Unlike the upper jaws of mammals (including us) that are fused to the skull, the upper jaw of a bird attaches to the skull at a flexible hinge. When a bird opens its mouth, the lower jaw moves downward and the upper jaw moves upward relative to the skull. Birds can therefore open their mouths wider than a mammal.

The beak of a bird is covered by a sheath called the rhamphotheca. The sheath is made of keratin, the same material that makes your fingernails. In most birds, this sheath is hard but in waterfowl and shorebirds the sheath is soft and leathery.

As a bird feeds, abrasion causes the sheath to wear away at the tip. The skin overlying the bones of the maxilla and mandible continuously lays down new keratin to replace the lost material.

It’s interesting to note that the beak length of some birds changes from winter to summer. As an example, House Sparrow beaks are longer in the summer. During the summer, House Sparrows eat softer foods compared to the winter when hard seeds are the staple of the diet. Feeding on the hard seeds breaks down the sheath more quickly and the winter bill length therefore is slightly reduced.

Birds kept as pets often are not given hard enough foods to allow the birds to wear down the tips of their bill. That is why parakeet owners provide their birds with cuttlebone.

In the past ten years, a serious and even grotesque condition called long-billed bird syndrome has been documented. Bud Anderson, a hawk biologist at the Falcon Research Group in Bellingham, Washington noted a Red-tailed Hawk in 1996 with an overgrown beak. Since then, Anderson has recorded 86 hawks with deformed bills; all but nine were Red-tailed Hawks.

The condition is caused by hypergrowth of the sheath. The hypergrowth can take a number of forms but the end result is that the function of the bill is severely compromised. Examples can be seen at: http://www.frg.org/frg/lb_syndrome.html

The condition is lethal without intervention. Hawks with the condition are underweight because they cannot process prey with their bill. They are usually plagued with feather lice, presumably because their deformed bill does not allow them to preen.

Long-billed hawks are easily captured. They quickly come to a prey lure because they are desperately hungry. A rehabilitator can remove the excess sheath and release the bird after it recovers its weight.

The long-billed hawk syndrome has mostly been documented along the west coast of North America, from San Jose north to Richmond, British Columbia.

However, the long-billed syndrome is not restricted to hawks. Recently, a biologist near Anchorage, Alaska documented over a thousand Black-capped Chickadees with overgrown bills. Biologists in Montana have found the syndrome in Red-winged Blackbirds.

Julie Craves, a Michigan bird bander, and Colleen Handel, a biologist with the U. S. Geological Survey, have compiled records of the long-billed syndrome in North America. They found records of overgrown bills in over 110 species of birds, mostly songbirds. Records of this condition have been reported from places as far-flung as Florida, Baja California, Maine and several Canadian provinces.

At this point, the cause of the syndrome is not known. We do not know if the condition results from the same cause in all the species that have been reported to have these deformed bills.

For hawks, the condition is found in both young and adult birds. Blood tests of afflicted hawks show that white blood cell counts are normal; one would expect elevated counts if the birds harbored some of disease organism. Veterinarians tested affected birds for thyroid disorders and beak and feather disease, two diseases that cause deformed growth in parrot beaks. The tests for both diseases were negative.

Currently, veterinarians are looking for pathology of the cells that produce the keratin sheath in long-billed birds. Perhaps some clues to the cause of the syndrome will be forthcoming.

You can help by reporting any birds you see that have long bills to Bud Anderson at: [email protected]

[Originally published on September 17, 2006]

For the Birds -Report of Ivory-billed Woodpeckers in Florida

Ivory-billed Woodpeckers are back in the news again. Reports of Ivory-billed Woodpeckers (IBWO) from northwestern Florida have recently been published. However, definitive photographic or video evidence is lacking at this point.

Before discussing the details of the Florida evidence, let’s recap the history of the report of Ivory-billed Woodpeckers in Arkansas by a Cornell Laboratory of Ornithology (CLO) research team. The evidence presented in the spring of 2005 included several brief sightings by ornithologists, recordings of putative birds and a short, grainy video.

The data presented by the CLO team was met with skepticism by a number of ornithologists and birders. Reports of sighted birds without a photograph are generally not considered firm evidence. The sightings of claimed IBWO were brief. These sightings should be treated as suggestive but not definitive.

Acoustic evidence for IBWO comes in two flavors: a rapid double knock that the birds make when foraging and a characteristic “kent” note similar to the sound of a toy trumpet. Recordings of possible double knocks and kent notes were recorded on automated recorders by the CLO team. Their analysis of the sounds indicates a degree of uncertainty. No known recordings of double knocks exists, making it impossible to claim that double knocks were made by IBWO. Notes that sound like kent notes could be made by Blue Jays or White-breasted Nuthatches.

Finally, the video has been subjected to detailed analysis by the CLO team and by skeptical ornithologists. Although the CLO team vigorously defends their claim that the bird in the video is an IBWO, other analyses show that the video could be a Pileated Woodpecker. In my view, the video simply is not definitive evidence of IBWO.

The CLO team of 22 ornithologists as well as 112 short-term volunteer observers were unable to obtain photographic evidence during the 2005/2006 season. Three or four possible visual identifications identifications were reported.

Let’s stop here to acknowledge that even the most skeptical ornithologists and birders hope that the IBWO is still alive. All hope that convincing photographic or video evidence will be gathered. The skeptics will be glad to acknowledge the continued survival of the IBWO with more compelling evidence.

These differences of opinion beg the question of how the methodology of science works. The scientific method depends on trying to disprove an hypothesis, rather than confirming an hypothesis. A scientist develops an hypothesis and designs an experiment to test her hypothesis. If the experiment disproves the hypothesis, the scientist throws the hypothesis away and develops new hypotheses for her particular question. If the experiment supports the hypothesis, the scientist accepts her hypothesis as tentatively true but designs other experiments to try to knock the hypothesis down, to disprove it. A scientist begins to feel confident of her hypothesis only after a particular hypothesis has survived multiple tests to disprove it.

Scientists must be careful to avoid subconsciously supporting a pet hypothesis. One way to avoid this confirmation bias is to test two or more hypotheses at the same time. In the case of the CLO video, two hypotheses are: the bird is an IBWO and the bird is a Pileated Woodpecker. Because the video evidence in part supports each hypothesis, a scientist would revert to Occam’s razor. This useful principle simply says that when confronted with multiple possible explanations, choose the simplest one until more information is gathered. Occam’s razor favors the skeptics’ view that the woodpecker in the video is a common Pileated Woodpecker. Similarly, the kent notes could be given by IBWO, Blue Jays or White-breasted Nuthatches. Occam’s Razor tells us to reject the IBWO hypothesis on the basis of the present information.

Two weeks ago, a team of researchers based at Auburn University reported the possible presence of IBWO along the Choctawhatchee River in the panhandle of Florida. They published their evidence in an on-line ornithological journal, Avian Conservation and Ecology. You can download a copy of their paper at: http://www.ace-eco.org/vol1/iss3/art2/

The evidence consists of 14 sightings of one or two birds since May, 2005; hearing either the double knocks or kent notes of birds on 41 occasions; finding roost holes purportedly larger than those made by Pileated Woodpeckers; and finding evidence of foraging signs (neatly scaled bark from trees with tightly adhering bark). In addition, automated recorders recorded 99 possible double knocks and 210 possible kent notes. You can hear all of these recordings at: http://web2.uwindsor.ca/courses/biology/dmennill/IBWO/IBWOsounds.php

Two blogs with opposing views on the quality of the data and the plausibility of the claims for IBWO presence are Ivory Bill Skeptic (http://tomnelson.blogspot.com/) and Ivory Bills Live (http://ivorybills.blogspot.com/).

[Originally published on October 1, 2006]