Densité, taille des territoires et production dans une population d’aigles pêcheurs Haliaetus vocifer (Daudin)

Résumé En

A very dense population of African Fish Eagles, Haliaetus vocifer (100 pairs within a 120 km2 area) has been studied in the Rwenzori National Park (South West Uganda) at the end of the breeding season (February-March 1976). Each territory covered an area of 20 to 50 hectares and had an average diameter of 200 to 900 meters All the coast line is fully occupied, several adult birds, even mated, being unable to secure a territory of their own. Only 37 % of the pairs produced fledged young (average of 1.13 per successful pair and 0.42 per established pair). The whole population was made of 70.2 % adults, 17.2 % juveniles, 6.9 % first and second years immatures and 5.7 % subadults (3rd and 4th years), giving an overall mortality rate of 80 % during the first two years, 17 % during the two last years of immature stage and a mean adult life expectancy of 25 years. Density and breeding success have been correlated with seve¬ ral territory features through a multivariate statistical analysis. Though a higher density reduces production of young, the most favorable habitat for a breeding pair includes a rather steep and well wooded slope, along shallow and calm coastal waters.