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Re: Bird mortality: North vs. South

At 05:15 PM 06/05/01 -0400, John Bois wrote:
Birds in the northern hemisphere generally live shorter lives than
southern birds.  They also have larger clutches and are more willing to
defend their brood. Why the latitudinal differences?  The paper doesn't
address this.

This is not a new idea. One hypothesis, which makes sense to me, is that most southern land birds live in quite mild climates (there being far less land at high latitudes, Antarctica excepted, in the southern hemisphere) and are less likely to be long-distance migrants. This greatly reduces a number of mortality factors affecting many northern species. The potential for longevity may be no different; it is the survival rate in the wild that differs.

Ronald I. Orenstein Phone: (905) 820-7886
International Wildlife Coalition Fax/Modem: (905) 569-0116
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