What unique behavior do male pigeons demonstrate in comparison to many other bird species?

Male pigeons exhibit the unique behavior of producing a substance known as "pigeon milk," which is a secretion produced in their crops that serves as a nutritious food source for their young. This process occurs during the feeding of the chicks, typically when they are very young and require easily digestible nutrition. Both male and female pigeons participate in this feeding, but it is particularly notable that male pigeons, unlike many other bird species, take an active role in this aspect of chick-rearing.

This behavior sets pigeons apart from many other birds, where generally, it is the female that undertakes primary incubation and nurturing tasks without such a specialized form of nourishment. Thus, the production of pigeon milk is a distinctive characteristic of male pigeons that showcases their involvement in parental care, differentiating them from a variety of avian species that do not share this trait.