Generally, levels of speciation and endemism of birds are low in deserts and the number of bird species largely confined to deserts is small (Wiens 1991). Even so, certain taxa contribute disproportionately to desert avifaunas, e.g. Burhinidae, Pteroclidae, Thinocoridae, Alaudidae, Ephthianuridae (four out of five species), some Glareolidae and Charadriidae, certain genera of Furnariidae, Tyrannidae, Mimidae and Turdidae (Maclean 1976c; Tables 2.1 and 2.2). Convergent evolution of birds of different taxa in the different deserts of the world is a phenomenon to which attention has been drawn from time to time (e.g. Maclean 1976c; Drozdov 1984); this is not surprising in view of the similarly harsh environmental selection pressures to which arid-zone birds are subjected. Such convergence is physiological, morphological and behavioural
KeywordsArid Zone Abundance Index Peregrine Falcon Arboreal Species Desert Scrub
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