Effect of nest microclimate on effective endothermy in White Stork Ciconiaciconia nestlings

White Storks frequently carry fresh cattle dung to their nests between one week before and three weeks after egg hatching. Because a possible effect o f this on the thermoregulation of the chicks was suspected, we selected nes ts with a brood size of two to carry out several experiments. First, we com pared the body temperature of all individually isolated chick with one that remained in the nest. The isolated chick was kept in a wooden cage near th e nest tree. After a 20-minute period, the nestling that remained unbrooded ill the nest showed a higher body temperature than its sibling. Secondly, we rioted that when fresh dung was removed from some of the nests, body tem perature dropped more quickly than those from unmanipulated nests used as a control. We conclude that the microclimate of the nest influences nestling thermoregulation. This may help to advance their age of effective endother my.