Recent studies by the Max Planck Institute for Ornithology are now finding that not only do birds have a sense of smell but it can be as important to birds as it is to fish or even mammals.
The size of the olfactory bulb definitely is different across species.
The nostrils of the nocturnal Kiwi are at the tip of its beak so that when it is forging, smell rather than sight guides them.
Birds like vultures that rely on dead animals for food have a greater sense of smell to help find it.
In general, evolution has not enhanced the sense of smell for birds because they spend a lot of time high in trees where terrestrial odors get dispersed before reaching the heights birds reside at.
From the Cornell Lab of Ornithology
Do birds have a sense of smell?
Some birds, such as falcons and hawks, are known for their keen eyesight.
Owls have excellent hearing, used for locating prey at night.
But do any birds have a well-developed sense of smell?
The original question and subsequent answers can be found on Quora
Written by Mitch Rezman
Approved by Catherine Tobsing