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Birds are not concerned with the odors of their immediate environment. To a chicken, a starling or a cowbird, the odors of its environment are of little or no con-sequence. I am not saying that birds do not have the apparatus for olfaction, nor am I saying that no bird can smell. The kiwi of New Zealand is almost totally blind and does sniff. They do have "nostrils" on the tip of the bill. However, they are an unusual exception. If we place highly odoriferous material under one of two food choices and present them to domestic chickens or starlings, their choice behavior is not affected. Surgical ablation of the olfactory lobes in the domestic fowl does not alter its food preference behavior. The point here is that in most birds, odor is of little or no behavioral significance.
Birds have an interesting sense of taste. They have taste receptors like other animals, and their general structure is essentially the same as that in other vertebrates. The starling and chicken have a few dozen taste buds as compared to 25000 for the cow. The chicken has all the taste buds at the back of the tongue with the front half of the tongue highly cornified. In the chicken, the taste buds are so far back that it would appear that by the time it can taste something, it is too late to change its mind about swallowing it. Most birds do not respond to what we describe as sweet. The parrot and some of the fruit-eating birds do, but the domestic and song birds do not respond to sugar as do humans. Blackbirds on an adequate diet do not appear to respond to sugars, certainly they do not avidly select dextrose, maltose or sucrose in water in a choice situation. They do, however, reject xylose which can cause an eye condition.