For the Birds Radio Program: The Dr. Ruth of Ornithology explains the birds and the bees (UDY)
Why is Laura called the Dr. Ruth of Ornithology?
I recently got into a discussion about the origins of the term, “the birds and the bees,” since birds are lacking much of the equipment that would make it easy to explain to children about…well, the birds and the bees. One thing led to another, and suddenly I was asked to explain just how birds do go about creating new little birds.
Okay. Male birds have two testes, both internal (so avian sperm must be able to survive at very high temperatures, and they don’t need to worry about their fertility if they jump on a bicycle now and then). Sperm from the testes are sent through two tubes called the vas deferens to a chamber called the cloaca. The cloaca is sort of the vestibule entry into the whole house, with those two hallways to the testes, the ureters leading to the kidneys, and the large intestine. So it’s very important for birds to poop before having sex, to clear out the vestibule before company arrives, so to speak, but since birds can poop at the drop of a hat (meaning on your head the moment your hat falls off) this does not represent any hardship.
Female birds have only one functional ovary (if they had two, and managed to ovulate through both, they’d end up with scrambled eggs inside), which is connected to the cloaca via the oviduct. The ovary looks quite a bit like a teeny tiny cluster of grapes, only a couple of grapes are double the size of the rest, and one is HUGE. That is actually the whole yolk of the next egg to be ovulated. During the nesting season, female birds usually ovulate once a day.
So the birds are feeling romantic–maybe they’re cranes and have been singin’ and dancin’ in the rain, maybe they’re red red robins who’ve been bob-bob-bobbin’ along–and now the moment arrives! He flutters his wings in eager anticipation, and this time she doesn’t flitter off saying she has a headache–she actually flutters her wings back at him! So he hops aboard her back, and she’s twisted her tail a bit to get the bottom to face the side, and he twists his tail to get the bottom to face the side, and their two cloacas meet in what ornithologists romantically call the “cloacal kiss.” And a packet of sperm from him passes over into her cloaca. Then he flies off, she remains sitting where she is a while, and they each pull out a tiny little cigarette.
The sperm swim, as sperm are wont to do, headed up her oviduct. Meanwhile, back at the ranch, she’s ovulated one yolk that morning, which is in the high reaches of the oviduct. One lucky sperm wins the race, and the rest go over into the pool hall and shoot a few rounds, hoping they’ll have better luck in coming days, and some of them do, because as I noted, they can survive warm body temperatures.
As the fertilized egg works its way down the oviduct, the cells secrete the proteins that make up the albumen, and then secrete the calcium that will form the shell. And eventually, usually by early the next morning, the egg has reached the vestibule, which makes the female bird very uncomfortable and she heads for a nest (if her own isn’t built, she’ll take any port in a storm) and dumps the egg out. And eventually it hatches into another bird who will one day ask his parents where he came from, and they’ll say “the stork brought you,” or “Toledo,” depending on how much of a sense of humor they have.