and threatened vertebrate species, showed differing patterns for bird, mammal and amphibian species, which has consequences for hotspot-based conservation strategies. Other studies by Rasmussen and her international colleagues looked at the importance of energy availability, and a 2007 paper showed that global patterns of spatial turnover are driven principally by widespread species rather than restricted ones. This complements other work, and helps to establish a unified model of how terrestrial biodiversity varies both within and between the Earth's major land masses. Paleo ornithology A fossil site at a borrow pit in near Cheswold, Delaware created during highway construction unearthed 11 specimens of fragmentary and unassociated avian fossils, which were identified by Rasmussen as including a small loon, a small gull-like species and five specimens of a gannet-like seabird, probably Morus loxostylus, a common species in the Miocene. All of these forms were already known from a site in Chesapeake Bay, Maryland. The finds suggests that the Delaware site was the near-shore area of a large bay at the time of deposition. Rasmussen was also involved in a review of fossil birds from Miocene and Pliocene deposits in North Carolina. Finds included an early Miocene loon Colymboides minutus, various ducks, a crested tern closely resembling the modern royal tern Sterna maxima, and a member of the crow genus, one of the few fossil passerine birds from that period. The review found that fossil birds from this period generally closely resemble a modern species or genus, and those that do not can usually be placed in a modern family with a fair degree of confidence. Birds of South Asia In 1992, Rasmussen took the position of assistant to S. Dillon Ripley, the former secretary of the Smithsonian, who was planning to produce a definitive guide to the birds of South Asia. When he became ill shortly after beginning the project, Rasmussen took over the project, and with artist John C. Anderton, produced Birds of South Asia: The Ripley Guide, a two-volume bird guide for the Indian subcontinent which was the first field guide for the area to include sonograms. Volume 1 contains the field guide with over 3400 illustrations in 180 plates, and more than 1450 colour maps. Volume 2 (Attributes and Status) gives specimen measurements, data about identification, status, distribution and habits. Vocalizations are described from recordings, and there are over 1000 sonograms. 1508 species that have occurred in India, Bangladesh,