Pigeons do sometimes lay eggs without mating if they can’t find a mate.
No chick will hatch from the egg as the egg will not be fertilized.
A Rare Case Of Asexual Reproduction (Parthenogenesis)
Parthenogenesis is what happens when the female reproduces asexually without a mate, this has happened in only one known isolated case amongst pigeons.
When a pigeon produces an egg without an egg it will be unfertilized and will not produce a chick.
Reasons A Pigeon May Lay An Egg Without Mating
The reasons a pigeon may produce an egg without mating are usually because of lack of males.
If for some reason there is an imbalance between the genders, fewer males are born or reach maturity, some females will be left without a mate.