Why do chickens have breasts but no nipples?

Chickens have breasts because of their muscle structure, specifically the pectoral muscles, which are responsible for flight and movement. However, they lack nipples because birds, including chickens, do not feed their young through nipples like mammals do. Instead, chicks obtain nourishment from the yolk sac at hatching and later eat solid food. This evolutionary adaptation reflects the different reproductive and feeding strategies of birds compared to mammals.