The tutor illuminates the fascinating relationship between the size of a species’ range and its density within it.

Ten to fifteen years ago I subscribed to The Economist. If it’s still the same, I highly recommend it. I stopped subscribing because, as a stay-at-home dad with kids aged two and four, I became too busy to read.

Though it’s called The Economist, the magazine (once again assuming it’s still the same format) covers virtually every facet of news that appeals to a world audience. I recall a very interesting article I read in it about populations. The idea it conveyed is that a species that enjoys a large range, is also proportionately more abundant within its range when compared to a species confined to a smaller range.

I forget whether the article gave an example, but I’ll give one. The America robin lives virtually everywhere in North America. There has been one (or more) in the yard my entire life, whether on the Atlantic or Pacific coast. Their range is tremendous, and robins are apparent when you’re outside.

The peregrine falcon does indeed live here, but I’ve never seen one. Its range, though large, is much smaller than the American robin’s. With a smaller range, biology predicts that it would also be less frequent within that range. Hence, you’d likely see it less than the robin, even living where both species reside.

There are several possible reasons for the relationship. Perhaps an obvious one is that a species that is more selective of the geography it inhabits, is logically more selective about its local address as well. On the other hand, a species that will inhabit virtually any geography, will likely accept the living conditions of any local habitat as well.

I’ll be further exploring the relationship between range and population density in future posts:)

Source:

wikipedia

Bull, John and John Farrand, Jr. Audubon Society Field Guide to North American Birds.
   New York: Alfred A. Knopf, 1977.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.