A Comparative Analysis of the Plumage Mass of the Demoiselle Crane (Anthropoides virgo L. 1758) and the Eurasian Crane (Grus grus L. 1758) (Aves, Gruiformes)

This is the first description of the distribution of the mass of the down and downy feathers along the pterylae of the Demoiselle Crane and the Eurasian Crane. The fundamental differences in the plumage structure of these closely related species, which live during the summer in different climatic zones, is shown. On the ventral side of the body of the Eurasian Crane, the proportion of down and downy feathers is significantly greater than on the dorsal side, whereas the proportion of the plumulaceous portion of the contour feather vane is lower by a factor of 1.5 to 2. The afterfeather commonly exceeds 2 cm. This distribution of fluff ensures effective thermoregulation in this cold-tolerant species, which is likewise tolerant of water. In the Demoiselle Crane, the abundance of down and downy feathers on the ventral side of the body is lower by a factor of three than on the dorsal side and by a factor of two than in the Eurasian Crane. On the dorsal side of the body, the proportion of fluff is almost 1.5 times greater than that of the Eurasian Crane. The proportion of the plumulaceous portion of the contour feather vane on feathers of different sizes on the dorsal and ventral sides is approximately the same. The contour feather contains predominantly umbilical down. Such a structure of the integument on the ventral side of the body allows the Demoiselle Crane, an inhabitant of hot climates, to ventilate better the thickness of the plumage and increase the heat transfer of the body to the environment. The large proportion of fluffy structures on the dorsal side prevents heat from penetrating the skin.