The Sense of Smell and Bird Noses

Whether birds have a sense of smell or not has been a much debated question by ornithologists. Modern data based on experiments and anatomy of both the nasal cavities and the olfactory lobes of the brain suggest that most birds have practically no sense of smell. The exceptions are Kiwis which have poor eyesight and hunt worms using their sense of smell. Several species of tubenoses which can detect the smells of fish oils floating on the surface of the sea, allowing them to find schools of fish or anchovies because their messy feeding causes an oily scum to form on the surface of the sea. The third group of birds definitely known to use smell to locate food are the vultures - both old world and new world species have been shown to find carcasses by smell to varying degrees. Other groups of birds with well developed olfactory lobes, but for which the actual evidence of the use of smell to locate prey is lacking, include various waders, many water birds, nightjars and swifts.

Reference: http://www.earthlife.net/birds/smell.html