Water is indispensable for all vital activities of any living organism, and its importance has been taken into consideration in the study of every physiological phenomenon in any organism (Willoughby, 1966 and 1969 ). Many structural modifications(Kent, 1973 and Jordan and Verma, 1986 ), and physiological ones (Azouz, 1966 and Viscor et al., 1985 ) were pointed out indicating the adaptability of such modifications for the flight nature of birds. The purpose of this study was to investigate to what extent the water content of tissues is significantly affected by the nature and pattern of flight. In order to ascertain such relationship the following species were studied : the flightless domestic chicken ( Arbor acre ), the soaring hovering flyer kestrel ( Falco tinnunculus ), and the flapping flyer palm dove ( Streptopelia senegalensis aegyptiaca ).