Range and patterns of Great Bustard (Otis tarda) movements in Villafáfila, NW Spain

The range of juvenile dispersal and adult seasonal rnovcments tn the Grcat Bostard (Otis tnrda) population of VillafAfila Reserve, N W Spain, is studied using data from censuses and individual marking between 1983 and 1994.

Abstract

S U M M A R Y . R ~ ~ I ~ ~ and putterns of Greur Bustord (Otis tarda) 1nol:etnenls in Villofijlu. N W Spnin. We studied the range of juvenile dispersal and adult seasonal rnovcments tn the Grcat Bostard (Otis tnrda) population of VillafAfila Reserve, N W Spain, using data from censuses and individual marking between 1983 and 1994. Thirty birds (22 m a l e 8 females) of those marked as young were seen during their juvenile dispersal outside the Reserve, at distances of up to 63 km, preferentially nor~heastwards, over an area of ca. 2800 km2. All males and 40 % oi females abandoned the Reserve during their juvenile dispersal. About hall [he males born in the Reserve never returned to it as breeding adults, while all females returned. With respect to seasonal movemcnts of adults, aboul 40 % of females wintcring in the Rcserve abandoned it during thespring-summer to nest, most of them returning in Octobcr. A 20-30% or the males present at the display arenas ilr early spring only entered the Reserve during the cxhibition and copulatory phase. About half the males present at that time abandoned thc Reserve once the peak copufation period was over, remaining at up to 20 k m of the display arenas during thc summer. The observed dispersal patterns are discussed in relation to currcnt conservation policy of thc species in the reBon of study.