Pigeons aren’t just pets, they were also raised for food (and sacrifice). And wild ducks & geese have penises, not just the domesticated ones.
Guineafowl also don’t have penises.
Basically, that quote is a load of nonsense.
So, on the one hand we have the non-functional vestigial homologs.
On the other hand, we have numerous cases of pseudo-penis, including the weavers mentioned by Colibri, but not limited to birds.
One of the most fascinating cases is the female spotted hyena. Spotted hyenas have complex social structures in which females are dominant. Females are larger than males, with high testosterone levels. They have no external vaginal opening, and the clitoris is enlarged into a pseudo-penis as large as the male’s true penis, making the sexes hard to tell apart except by body size. Females with young cubs have distended mammary glands and an apparent penis, so they were once thought to be hermaphrodites. The females use the pseudopenis to urinate; the male penis must be inserted through the female pseudopenis in copulation, an awkward process; and they give birth through it.
Incidentally, spotted hyenas are wonderful animals - highly intelligent, curious, with complex social structure. Their negative reputation in both Western and African culture is undeserved. Even the notion that they are sneaky scavengers are wrong, they hunt at least half of their own food; and they are hardly cowardly, they will defend their kills against lion.
Can’t speak for pigeons, not having direct experience with them. Or canaries.
However parrots (and cockatoos, which are also parrots) are not domesticated. They are wild animals that are imprinted/tamed with each generation. It will take more time before they can be truly said to be domesticated. And they do not have penises.
Falcons are not domesticated, either. Falconry birds are caught from the wild and they aren’t pets. It’s more of a business relationship with a professional hunter. I have no idea if falcons and other raptors have penises, not having direct experience with them. I’m going to guess not just because most flying birds don’t have them.
There are plenty of penis lacking domestic birds, just check out a good pet store.
What you are referring to is livestock birds. The theory is that flight comes with a cost, meaning to drop weight everywhere you can to have the biggest advantage. One thing that went in many birds was the penis, but if you are still lugging around a wanker, your evolutionary path didn’t really concentrate in weight dropping, thus more meat, and perhaps easier to catch - thus more desirable for a dinner bird.
Yeah, I meant livestock. That was *not *a well-worded question.
There’s a paper here on the molecular genetic basis for the loss of penis in most birds, including background discussion of various evolutionary hypotheses.