Good news! As of late 2005, all volumes in this authoritative series are back in print.
One of the most significant series in the natural sciences, which has produced some of the most influential ecological monographs.
From the publisher's announcement:
Monographs in Population Biology is a continuing series of books intended to examine important aspects of the ecology of plants and animals. Embracing both theoretical and empirical studies in a variety of subject areas, the series aims at well-written books that emphasize synthesis, fresh insights, and creative speculation. From the start (with MacArthur's and Wilson's Theory of Island Biogeography) the series has produced some minor classics, and has delineated new areas of research in population biology.