For the Birds Radio Program: Nighthawk Dissection
Today Laura gives the inside story of the Common Nighthawk. 3:09 (This MIGHT be the right script to go with the placeholder–it definitely was recorded for and aired on 7-1-94)
Last week when I taught a group of sixth and seventh grade girls a class about birds, we decided to dissect a nighthawk. We left Fred and Sneakers home that day so they wouldn’t witness the gruesome scene. This particular nighthawk was in perfect condition, except for being dead of course. It had been hit by a car last fall. Our autopsy revealed that its clavicle had been broken and one humerus bone was completely ripped off, tearing and piercing muscles so there was a lot of internal bleeding. We were glad that it had died almost immediately. Dissecting is sad enough without imagining how an animal suffered.
You can learn a lot from a dead animal. In this case, we weighed many of the internal organs. The two eyes each weighed more than the tiny brain, which the girls thought was a fine explanation for the disparaging term “bird brain.” The skull was very thin, to reduce its weight, but to give it strength, it had a spongy inner layer providing an air cushion to protect the brain.
The pectoral muscles and keel bone alone were 25 percent of this well-fattened migrant’s total weight, proof that it takes a lot of power to carry a nighthawk all the way to South America and back. The girls were fascinated with the tiny, flat lungs woven into its back ribs. I stuck a tube into the trachea and blew. Most of the air sacs on one side had been pierced in the accident, but they could see how a few of them expanded. Air sacs are thinner than the most stretched-out balloon, and as clear as water. They almost seem too fragile to be part of a living creature. Oddly, when a bird undergoes surgery, air sacs are often pierced and deflated, but somehow the bird usually doesn’t seem to suffer any ill effects.
My girls were already familiar with gizzards, but they hadn’t known that the gizzard is just the muscular section of a bird’s stomach. In the case of a nighthawk, it’s huge. Nighthawks pig out when bug-catching is good, and so can afford to lay low on rainy nights when insects are hiding out. A strong stomach is necessary to grind up hard beetles. Oddly, this nighthawk had a rough little stone in its stomach. Not one of the nighthawks I’ve ever cared for has been able to pick up items in its beak. In the wild, they get all their nutrition from flying into airborne insects, their capacious mouths wide open. There are at least a few records of stones in nighthawk stomachs, so now I want to find out just how the stones get in there. That’s the problem with dissecting. You always end up with more questions than you started out with.