Ecology of the Long-Tailed Jaeger at Lake Hazen, Ellesmere Island

ABSTRACT. Breeding density, timing, chick growth and food habits of a high population of long-tailed jaeger were studied in 1966. Breeding density fluctuated from O to 2 pairs per square mile (259 hectares) from 1961 to 1966; peak years were 1962 and 1966. Breeding success was 12 to 13 per cent of eggs laid in 1966, and only 1 of 7 nests in 4 low years was successful. Published evidence suggests breeding success in peak years is usually high. Egg-laying dates vary widely between years and within populations. Occurrence of food items in 242 fresh and 710 old regurgitated pellets was, respectively, 90.1 and 94.0 per cent lemming remains. Occurrence of other vertebrate prey (mostly birds) was 18.6 and 8.0 per cent. Snow buntings were the most frequent bird (79.5 and 72.5 per cent), and shorebirds the next most frequent group (9.1 and 21.6 per cent). The percentage of juveniles among passerine birds was 83 and 79.4 and among shorebirds was 75 and 91. Insects occurred in 30 per cent of new pellets. RÉSUMÉ. Écologie du Labbe d longue queue du lac Hazen, île d’Ellesmere. On a étudié en 1966 la densité de reproduction, la distribution chronologique, la crois