For the Birds Radio Program: Gall Bladders
Do birds have a gall bladder? 3:40 (recast from 9-14-90) Date confirmed.
The summer of 1990 marked the end of an era for me. I’d spent a fair amount of the previous 38 years eating breakfasts, lunches, and dinners and then digesting them without much thinking about it. I’d never considered the possibility that I actually might have something called a gall bladder. I got through biology and physiology classes without taking anything personally.
But that age of innocence came to a close when my own personal gall bladder mutinied. Its misbehavior was corrected by a grossly unpleasant routine medical technique mysteriously called a cholecystectomy. I would have chosen the more accurate title, “Surgical procedure from hell.”
Once I realized that I actually had a gall bladder somewhere inside me, and even more ominously that I was about to lose it, I naturally had to do some high level research into the important issue of whether or not birds have gall bladders, and what the heck a gall bladder is for in the first place.
It seems the gall bladder is a little sac that collects bile from the liver and delivers it as needed into the small intestine to aid in the breakdown of fat. Bile doesn’t actually digest fat—it emulsifies it like a detergent acting on grease. When the gall bladder is removed, the bile made in the liver drips continuously into the small intestine. No wonder I tuned my physiology professor out. I might have paid more attention if someone had mentioned that a bad-tempered or cross person is called “bilious” because he acts as if there were something wrong with his bile. I doubt if a bilious person becomes sweeter natured after a masked stranger armed with a scalpel gets through slicing into him.
Like people, most birds have gall bladders. For their size, penguins have enormous ones. It makes sense when you think about it. A male emperor penguin pigs out on fatty fish during part of his annual cycle, and then spends months fasting as he incubates his egg and chick. Without a gall bladder, the bile manufactured during incubation would be wasted, and there would be a shortage of bile when the penguin really needed it.
Hummingbirds, which eat nectar and small insects, don’t digest much fat, and do their best never to go hungry. As you might guess, hummers have no need for a gall bladder. Pigeons don’t have one either. Pigeons tend to glut out every morning and night, and then fast in between, but they’re actually digesting food pretty much continuously. Their large meals are stored in the crop, a large offshoot of the esophagus, to be released into the stomach a little at a time.
The Bohemian Waxwing, which eats fruits and insects, also lacks a gall bladder, though its close relative the Cedar Waxwing apparently has one. Ostriches and parakeets live out their lives without a gall bladder. And for some reason I haven’t been able to figure out, Peregrine Falcons are also missing one.
In a few species of mergansers, cuckoos, and cranes, some individuals have a gall bladder and some don’t. Probably this is due to natural anatomical variation, but I prefer to think that the ones without a gall bladder are survivors of an encounter with a tiny scalpel-wielding surgeon—maybe Dr. Killdeer himself.