I’m a molecular/evolutionary biologist rather than a zoologist, and I was mocked recently for my ignorance in supposing that domestic egg-laying chickens might require the presence of a rooster. Evidently they do not - they usually produce an egg every day, even if there’s no rooster around. It seems that my understanding of reproduction in actual birds and bees is incomplete.
What happens with wild birds? Making a bird egg requires a huge energy expenditure, so surely it can’t be the case that unfertilized ova in wild birds routinely develop into fully-formed unfertilized eggs? Is this just a trait that we have bred into domestic chickens?