Aldrich, John W.

English

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54 REVIEWS THE  BREEDING BIOLOGY OF  ROSS GOOSE  IN  THE  PERRY  RIVER  REGION, NORTHWEST  ERRITORIES. BY JOHN PEMBERTON RYDER. Canadian Wildlife Ser- vice Report Series, Number 3 .  Ottawa: De- partment of Indian Affairs and Northern Development, 1967. I 1  x 8% inches, 56 pages,  illustrated. $0.75. This second of the new series of Canadian Wildlife Service publications continues to emphasi,ze Canada’s most  vulnerable wild- life species and  the factors which control their  abundance. The tiny white Ross’ goose, the subject of the present study, has been considered a relatively rare  and possibly relict species deserving special management considerations. The distribution of Ross’ goose is limited during the breeding season,  as far as we know, to very restricted  areas  near the  Perry River in northeastern Mackenzie, where the present study was conducted, the west coast of Hudson Bay near the McConnell River, and the Boas River Delta of Southhampton Island. It winters in the interior valleys and along the coast further south in California. On its breeding gounds, it  overlaps the range of the larger lesser snow goose. The author found no evidence of competition between these species in the  Perry River area. Neither did he  mention  any  instance of interbreeding between these similar-appearing species, al- though I recall at least 10 individuals which were considered to  be “intermediates”  re- ported away from the breeding grounds by other observers. Mr. Ryder’s study was carried out during the summers of 1963 and 1964 at  Arlone Lake and  Perry River, Northwest  Territories. He  found  that reproductive activities of Ross’ goose are organized quite efficiently to fit into the short period when freedom from snow and ice permit  these birds to exist in the Arctic. Just  as the  tundra  habitat was becoming free of snow, the geese arrived on the nesting grounds  ready to lay  their al- ready fertilized eggs immediately. Islands in Arlone  Lake were chosen for nesting. These are relatively safe, being free of mammalian predators, particularly arctic foxes, after  the ice bridges have thawed. Highest density of nests was in edge areas of mixed dwarf birch, rock, and open mossy terrain. Fertility of  eggs was high and loss of eggs and goslings due to bird and mammal pre- dators  and  other causes was low. Neither mortality of young nor lack of food was thought to be a limiting factor  to  the popula- tion of Ross’ geese in the  area studied. After  the goslings were  able to travel, fam- ily groups dispersed over the  tundra between the nesting area and the coast,  although few actually  reached  the  shore. The  annual plum- age molts of both  adults  and young must be timed so that flight feathers grow back soon  enough to permit  migration  before freeze-up. Southward-migrating Ross’ geese concen- trate in southern Saskatchewan. Counts there of young in family groups in 1964 by Alex Dzubin (averaging 2.72 per family) showed very little  numerical difference from  the 2.88 young per family  group  determined  the  same year by the author and Harry Lumsden be- fore the geese left the Perry River breeding area. Counts made in January of that year and  reported by John Lynch  after the termi- nation of the hunting season in California, on the other hand, showed a drop to 1.65 young per  family  group. The  author dis- cusses a  number of complications in  making reliable counts of young birds. Despite these complications (which result in imprecision), he feels that the data indicate that  the great- est loss of first year birds, after they leave their nesting area, is on the southern leg of the  migration from  the  Canadian prairies and on the wintering grounds in the United States. It appears to the reviewer that the total loss of annual production by midwinter, after the chief hazards to inexperienced young are past, was similar to that of other species of geese in years favourable for re- production.  Forty-seven  per cent of the potential,  in  terms of  eggs laid (3.6 per pair), would seem to give a fair margin of safety, all else being favourable to survival. Data presented in this paper would appear to in- dicate that about half of the potential  annual production is lost on the breeding grounds and the other half in migration and on the wintering grounds. Although  predation was not  a  serious limiting factor in the present instance, there were indications that if most of the breeding colonies were not  insular,  this could be a serious cause of depletion. Furthermore, al- though the present studies were made under favourable  weather  conditions  and  produc- tion of Ross’ geese seemed to be satisfactory, the author cautioned that in such an unstable ecosystem as the arctic tundra, late seasons or excessive predation could cause drastic annual drops  in  production of geese. Ex- perience with other species of geese indicates that weather during the reproductive phase is probably the most important limiting fac- tor to annual production of arctic nesting birds, and  it is the  average  production  over  a number of years that is important in deter- mining the status of the species. Thus, continued surveillance of this  potentially vulnerable little waterfowl was wisely recom- mended. John W .  Aldrich 

The Breeding Biology of Ross' Goose in the Perry River Region, Northwest Territories, by John Pemberton Ryder

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The Breeding Biology of Ross' Goose in the Perry River Region, Northwest Territories, by John Pemberton Ryder

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