Which sense is least developed in most birds?

The story behind the answer

Smell is the least developed sense in most birds because their survival depends far more on superb vision and acute hearing. Many species have relatively small olfactory bulbs in the brain, while their eyes and ears are specialized for flight, foraging, and communication—think raptors spotting prey at great distances and owls pinpointing mice by sound. Taste is limited too (fewer taste buds than mammals), but smell is typically weaker across most groups.

There are notable exceptions: turkey vultures can sniff out carrion from afar, kiwis probe the forest floor by scent, and seabirds like albatrosses and petrels follow odor plumes across oceans; pigeons even use smell to help navigate. Memory tip: “See to fly, hear to sing—smell’s the weakest thing.”