Ardea
Official journal of the Netherlands Ornithologists' Union

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Kahl M.P. (1972) Comparative ethology of the Ciciniidae. Part 2. The adjutant storks, Leptoptilos dubius (Gmelin) and L. javanicus (Horsfield). ARDEA 60 (1-2): 97-111
This paper reports on some aspects of the behaviour of Leptoptilos dubius and L. javanicus. as observed in wild and captive birds. The behaviour of these two Asian species is compared with that previously reported for L. crumeniferus in Africa. In locomotion, foraging behaviour, and comfort movements all three species of Leptoptilos show many similarities. My observations tend to confirm reports that javanicus is less of a scavenger than dubius. Most social display patterns seen in dubius and javanicus were quite similar to homologous patterns in crumeniferus. In the Up-Down greeting display, dubius and javanicus were similar to each other but differed from crumeniferus: the two former species clatter with the bill pointed upward, whereas the latter species clatters with the bill pointed downward. The Balancing Posture of javanicus contains a bill-clattering component, lacking in this display in crumeniferus and, apparently, in dubius. Based on the observed behavioural and morphological evidence, I consider dubius to be most closely related to crumeniferus. However, because of their distinct differences in the Up-Down display, they should be maintained as separate species within a superspecies. In areas where dubius and javanicus nest together in mixed colonies, hybridization may be prevented by morphological differences and by differences in the form of the Balancing Posture, a courtship display shown by females.


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