06 December 2009

Habitat Utilization

Obviously, different-sized birds will prefer different sized foods, with competition having little to with it. If so, then curves showing habitat utilization should be random. But most studies do show uniform distribution of curves, with some overlap between each species. A limited amount of niche overlap can be tolerated. Two Princeton mathematicians, Macarthur and May, said that the competitive exclusion principle would kick in when, looking at a graph of competing species, the distance between the mean untilization of a contested resource by each species equalled the standard deviation of either species. I found this to be the case among antbirds in Ecuador.

Hutchinson found consistent size differences in competing bird bills. Remson found that a 1.2 size difference seems to be required for kingfishers to occupy same stream--prey sizes correspond to difference of bill size.

Diffuse competition is competition from unclosely related animals, like lizards, frogs, ants, rodents. For example, the Takahe, a large, moorhen-like bird in New Zealand, competes with Red Deer for grass: the deer takes more types of grass and hence is more common. Indeed, Takahe are near extinction.

Belted Kingfisher

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