Breeding biology of red-throated loons in the Canadian Beaufort Sea region

Abstract

Gavia stellata densities ranged from 0.6 pairs.km-2 on the Yukon coast to 1.8 pairs.km-2 at Toker Point on the Tuktoyaktuk Peninsula. An average of 73% of the pairs on territory nested each year. Productivity averaged 0.63 young.nesting pair-1. The median date of egg laying ranged from 19-24 June in four years, but was 3 July in a year when spring thaw was late. The chicks fledged a mean of 47 d after hatch, the first clutch chicks leaving the nesting pond in late August to mid-September. In all but one year, the mortality rate was higher for eggs than chicks, with egg losses peaking in the second half of incubation. Most (83%) chick losses occurred within three weeks of hatch. Just 13% of ponds were occupied in all five years of the study, while 39% were used in only one year. At two of the study plots, ponds with pairs that successfully reared at least one chick had a greater tendency to be occupied the following year than did ponds with unsuccessful pairs. -from Author