Relative skull size as one of the factors limiting skull shape variation in passerines

Despite a considerable interest of researchers to the issue variation in skull shapes birds and factors influencing it, some drivers associated with design features an entire bird body, which are important for both successful terrestrial locomotion flight, overlooked. One such factors, our opinion, is relative size (skull length relation body mass), can affect position body's center gravity. We tested effects size, allometry (i.e. absolute size), diet on shape. The study was conducted 50 songbird species wide range mass (8.3g 570g) dietary preferences (granivores, insectivores/granivores, insectivores, omnivores). Skull shape analyzed using 2D geometric morphometrics. revealed that similar patterns occur among passerines different sizes diets. predicted extent pattern as size. In effect likely due biomechanical constraints related flight.