SOCIAL-ORGANIZATION OF THE NUTHATCH SITTA-EUROPAEA-ASIATICA

An individually marked population of the Nuthatch Sitta europaea asiat ica was followed during 1986-1990 in the southern part of the Magadan region, Northeastern Siberia. As in European populations of the specie s, adult Nuthatches were strictly sedentary and lived their lives in p ermanent territories. Nuthatch territories in Siberia were much larger (averaging 30.2 ha) than those in Europe (about 2-10 ha). Pairs persi sted as long as both partners were alive. On average, 50.8% of the pai rs survived from one breeding season to the next, a figure very simila r to those given for European populations. Young Nuthatches dispersed widely after becoming independent and birds which were born in the stu dy plot were never found later. In contrast to Europe where juveniles always establish their own territories, juveniles in Siberia settled i nside the territories of old birds in autumn (usually 1-2 juveniles in the territory of an adult pair). Inside the adults' territory, the ju veniles lived in pairs or alone, but never in flocks. Their only chanc e to become bleeders was to replace an adult that died. The first-sett led juveniles had the best chance to obtain breeding status. Therefore , although the social organization of the European and Siberian subspe cies of S. europaea are similar in many ways, there is a dramatic diff erence in the way that juveniles establish their territories.