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Ornithology, Evolution, and Philosophy 123

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182 4 Ornithologist <strong>and</strong> Zoogeographer<br />

connection on the basis of the percentages of the animals common to both. In<br />

this, he pays no attention whatsoever (except in the general introduction) to the<br />

fact, that these isl<strong>and</strong>s might be totally different in their ecology: If you compare<br />

a savanna-covered isl<strong>and</strong> with a completely wooded isl<strong>and</strong>, you may get only<br />

a slight agreement of the faunas, although the geological history of the two might<br />

easily be the same. On the other h<strong>and</strong>, Rensch makes very little allowance for the<br />

distribution across the open sea. My work on Polynesian isl<strong>and</strong>s <strong>and</strong> even such<br />

isl<strong>and</strong>s, like Rennell <strong>and</strong> Biak , has convinced me that the open sea is not always as<br />

much of a barrier as commonly supposed. As soon as two isl<strong>and</strong>s are fully settled<br />

such as Batanta <strong>and</strong> Salawati, there is only very little exchange of individuals, but<br />

as long as one isl<strong>and</strong> is full of open ecological niches, it will permit the settling<br />

down of immigrants. This point has been largely disregarded by Rensch. I believe<br />

you cannot make such definite statements as he does in many cases, neither do<br />

I believe that all of the isl<strong>and</strong> connections have existed as postulated by him” (25<br />

April 1939).<br />

The distribution of birds in the Philippines is influenced by three main factors<br />

(Delacour <strong>and</strong> Mayr 1946k): (1) Climate <strong>and</strong> vegetation, (2) former l<strong>and</strong> connection<br />

between isl<strong>and</strong>s, (3) proximity to neighboring areas. These factors jointly have<br />

contributedtothespecialbirdfaunasofthevariousisl<strong>and</strong>s<strong>and</strong>isl<strong>and</strong>groups.

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