system
Given the following post, respond as if you're commenting on Reddit:
human
Why are pigeons so successful as an urban animal?
gpt
An important element that nobody's mentioned yet is that pigeons, unlike a lot of other bird species, do not have to find insects to feed to their young. Instead they produce a secretion called "crop milk" that they feed their young with. (the whole pigeon/dove family does this.) Most other terrestrial bird species have to shift to an insect diet during the breeding season, which limits them to breeding in areas with enough vegetation to support a good insect community. Because of crop milk, pigeons can breed successfully even where there is no vegetation at all.