Source: The Slater Museum of Natural History

The Snowy Owls (Bubo scandiacus) that came down to Washington this winter, which I have written about before, finally contributed some pellets to the cause of science.

Of course, you know what owl pellets are. Birds of prey, and actually quite a few other birds, eat a lot of stuff that doesn't make it through their digestive tract. Hair and feathers are difficult to digest, as are bones and mollusk shells. So even if they are broken into smaller pieces when eaten and crushed by heavily muscled gizzards, even the smaller pieces can't pass through the hindgut very well. Rather than sharp-pointed bones coming up one by one, they are coated in hair or feathers and barfed, urped, hurled, vomited and/or regurgitated back into the environment.

It's not easy to find these pellets unless you know right where the bird has been roosting. After they are produced, they get covered up by detritus, even blown around, and eventually decay into pieces. But they hold together for a while, and ornithologists have long used them to get a handle on the diet of birds such as hawks and, especially, owls. Snowy Owl pellets look like fuzzy three-inch cigars. It's been said there is nothing like a good cigar, but I personally prefer owl pellets.

Paul Bannick, well-known bird photographer and author of The Owl and the Woodpecker, recently sent me three pellets he picked up from one spot at Ocean Shores. At the museum, we soaked them in water and stirred them up until the feathers floated and the bones sank. We recovered a surprising amount of bones, arranged them by type, and identified them by comparing with our skeleton collection.

I had a pretty good idea what birds were out there, and it wasn't difficult to identify the majority of the bones as sandpiper bones. The only confusion would have been between Sanderling and Dunlin, both common birds in Grays Harbor. Sanderlings were common right where the owls were roosting, so I favored them. Sure enough, there were several lower mandibles present, and they clearly belonged to Sanderlings.

In total, at least five Sanderlings were present in these pellets, as indicated by counts of tibiae and tarsometatarsi, long, slender bones that were well represented because birds of prey tend to swallow legs of smaller birds whole. In addition to all the sandpiper bones, there were quite a number of larger bones. Many of them were broken up, but a few were intact, and two coracoids and a femur allowed identification as a Horned Grebe. Probably all the bones, including many vertebrae, were from the same bird.

I also examined single pellets from Sandy Point, near Bellingham, furnished by Isa Werny and Andrea Warner. They were mostly feathers, but one of them contained a few Horned Grebe bones, the other a few Bufflehead bones. The second pellet was found at the foot of a utility pole along with parts of a dead Bufflehead, making the identification easier. Both of these species are known Snowy Owl prey.

Snowy Owls are well known to subsist largely on water birds in the winter on our coast, and there wasn't a trace of a mammal in these five pellets. By now you may have figured out that ornithophagous = bird eating.

Dennis Paulson

Source: Scientific American

Mathematicians take their cues from owl wings to design quieter, less obtrusive planes

By Francie Diep and TechNewsDaily.

An owl glides by on silent wings. Many holiday travelers probably wish airplanes could do the same. 

"On airplanes, the back edge of the wing is where you get most of the noise," Justin Jaworski, a mathematician at the University of Cambridge in the United Kingdom, told TechNewsDaily. "My work is looking at developing theoretical models to explain trailing-edge noise."

Most recently, he and his colleague Nigel Peake showed, mathematically, that the noise from airplane wings could be reduced tenfold if their designers took a few cues from the feathers that fringe the trailing edge of an owl's wings. 

In their latest research, Jaworski and Peake found that owl wings are especially quiet in part because their trailing-edge feathers are flexible and porous, allowing some air through. Plane wings, of course, are hard and solid. But the pair found that if the edge of a plane's wings were perforated in a particular way, "the theory says you should be able to reduce noise as if there were not an edge there at all," Jaworski said.

Makers of real planes might have a difficult time taking that suggestion. Holes in the wings might reduce a plane's aerodynamics too much for the companies' liking, Jaworski said. Also, flexible trailing edges might flap in the wind, which would also reduce aerodynamics. These are issues that other engineers would work out in later stages of research, Jaworski said. He collaborates with experimental researchers to uncover the engineering trade-offs in his ideas.

In any case, the findings are still in their earliest stages, and it might take two or three years before the ideas for a quieter airplane wing are tested with a small model in a wind tunnel, Jaworski said. After wind tunnel tests, even more research would go into seeing whether the ideas would be cost-effective in real planes.

Meanwhile, the Cambridge researchers continue to refine their model and study owl wings for further secrets into their quiet flight, Jaworski said. 

On the theory side, the next step is to study other features of owl wings that are not common to noisier flapping birds such as pigeons. "We're really excited about looking at this downy material on top," Jaworski said, referring to a unique, soft covering owl wings have. He said the down covering is difficult to model mathematically, no one has studied it before, and it may be especially important to quiet flight.

Jaworski presented his and Peake's research Nov. 18 in San Diego at a conference hosted by the American Physical Society.