Breeding Biology of Red-throated Loons in the Canadian Beaufort Sea Region

Abstract

ABSTRACT. The breeding biology of the red-throated loon in the Canadian Beaufort Sea region was investigated from 1985 to 1989. Five study plots were established with a total area of 276 k m 2 and over 200 pairs of loons on territory each breeding season. Loon densities ranged from 0.6 pairs*km-2 on the Yukon coast to 1.8 paiwkm-2 at Toker Point on the Tuktoyaktuk Peninsula. An average of 73% of the pairs on territory nested each year. Productivity averaged 0.63 youngmesting pair-'. The median date of egg laying ranged from 19 to 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 (n = lo), 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 (82%) chick losses occurred within three weeks of hatch (n = 61).Just 13% of the 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. At the other three plots, reuse of ponds was independent of breeding success the previous year.

Smålommens Gavia stellata häckningsframgång i artens svenska kärnområde

“…The increasing tendency to abandon a tarn after a breeding failure is in accordance with previous results for Red-throated Divers in e.g. Canada and on Shetland (Gomersall 1986, Dickson 1993.…”

“…I flera fall var häckningstjärnen övergiven bara under något-några enstaka år, varefter den åter nyttjades av ett häckande smålomspar. Också på Shetlandsöarna och i tundraområden i Kanada har man funnit att smålommarna är benägna att överge en häckningstjärn efter ett misslyckande (Gomersall 1986, Dickson 1993.…”

Response of Pacific Loons (<i>Gavia Pacifica</i>) to Impoundments at Prudhoe Bay, Alaska

“…In northwest Canada, the glaucous gull was the only predator species seen taking the young of redthroated loons (Dickson, 1993). Predation on red-throated loon chicks was apparently limited to those less than 10 days old, and the greatest loss of young occurred in a year when there was a significantly large number of glaucous gulls in the study area (Dickson, 1993).…”

“…Strong (1990) concluded that habitat conditions for breeding common loons (Gavia immer) are reflected most accurately by reproductive output, and that the best measurement of reproduction may be a count of prefledged chicks 7 -10 weeks old. Dickson (1993) similarly indicated for redthroated loons (Gavia stellata) that reproductive success, as measured by young that survive to fledging, was a good indication of local habitat conditions. Andres (1993) suggested that local foraging behavior of Pacific loons should be determined before they are used as an indicator of freshwater habitat conditions.…”

Variable strength of predator‐mediated effects on species occurrence in an arctic terrestrial vertebrate community

“…2; Beardsell et al 2016). All these species can reuse the approximate nest location from year to year (Dickson 1993, Gauthier et al 2015, Beardsell et al 2016). For each species, we used a cluster analysis to define a number of nesting zones that had a species‐specific diameter and that can be used repeatedly (annually) for nesting (Supporting information for the detailed calculation of nesting zones).…”