The Bluebird Diaries – Day 29 (April 18, 2012)

I thought we’d dive into some reproduction talk today. There will be no pictures, but the explanations to follow may not be appropriate for your children if they are looking over your shoulder as you read this. Here’s a nice picture to break up the text, so you can decide whether to scroll down to the meat of the column! 🙂

Bluebird Eggs

Bird mating is different from humans and other common mammals. You may already realize birds have only one opening, called the cloaca (pronounced klo as in “closed”, long a as in “rake”, kuh rhymes with “duh”. klo-a’-kuh with the emphasis on the a.) This opening serves many purposes, including elimination, egg laying, and yes, fertilization. Female birds have ovaries which produce eggs (actually they usually have only one), and male birds have testes which produce sperm, but neither have external genitalia. Instead the male bird presses his cloaca against the female’s cloaca, so that sperm may be transferred. This is sometimes called the cloacal kiss.

Egg production takes around 24 hours (hence an egg-a-day). The egg meets up with the sperm early in that period, and the shell grows around the egg after it has been fertilized. Egg laying can and will occur whether sperm are present or not, which is why some eggs are duds.

I think we’ll leave it at that, a nice simple and not-too-graphic introduction to bird reproduction! If nothing else, it explains why the mating process seems so quick, if you happen to see birds in the act. There’s really not much to it except a bit of well-placed contact.

We’ll be back tomorrow!

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