Birds' Bones Built for Flight but Still Produce Red Blood Cells -BYLN-

Article excerpt

Bird lovers, you might not realize it, but you belong to a very large club.

About 20 percent of Americans enjoy the sport of bird-watching, an easy, low-cost hobby that can start in your backyard and take you far across the globe in search of exotic species. More U.S. bird enthusiasts live in the South, but local websites like ilbirds.com and illinoisbirds.com point to a huge flock of bird enthusiasts residing in the Chicago area.

Streamlined for flight, birds have fewer bones than other vertebrates. Beaks are designed as a lightweight adaptation that replaces a heavier jaw structure, and wing bones are constructed sparingly to aid in flight. The major limb bones are hollow, decreasing overall weight, but built for strength.

"Like mammals, birds make red blood cells in their bone marrow, but not all the bones have the same amount of marrow," said veterinarian Julia K. Whittington, medical director of the Wildlife Medical Clinic at the University of Illinois College of Veterinary Medicine in Urbana.

"Pneumatic bones, those that are hollow and communicate with the bird's air sac system and respiratory tract, only have cancellous bone at the ends, or epiphyses. Cancellous bone is the site of blood cell production," Whittington said. …