MALE-BIASED DISPERSAL IN THE GREAT BUSTARD OTIS-TARDA

We studied dispersal and seasonal movements of Great Bustards marked as young in Villafafila, NW Spain, between 1983 and 1990. This study documented male-biased dispersal in a sexually dimorphic, lekking species; one of the very few documented examples outside the Anatidae. Females nested outside the display area after visiting leks for mating. Males abandoned breeding activities after mating and dispersed during summer to moult. Young stayed with hens until a new breeding cycle was initiated in the next spring. Males dispersed significantly earlier and further from natal sites than females. Home ranges of males were significantly larger during their first two years of life than later, and those of females were significantly smaller than those of males. Average age of first lek attendance was 2.7 yr for males and 1.9 yr for females. Females attended leks closer to natal sites than males, and adult males attended the same leks year after year. Age of first successful breeding was 4-5 yr in females. These results support the hypothesis that sex-biased dispersal is determined by the different value of philopatry for the two sexes.