|
|
RESPONDENT
|
|
Gilles Gauthier
|
|
|
SITE NAME
|
|
Bylot Island, Nunavut, Canada
|
|
| Contact details
(phone/fax//e-mail//address): |
| // Gilles.Gauthier@bio.ulaval.ca // Departement de biologie & Centre d'etudes nordiques, Universite de Laval, St. Foy, Quebec City, Quebec, G1K 7P4 Canada
|
|
PROJECT DETAILS |
|
Project name:
|
|
Population Study of Greater Snow Geese on Bylot Island (Nunavut) in 2006
|
|
|
Start of survey:
|
End
of survey: |
Team
size: |
|
|
|
|
|
WEATHER
CONDITIONS
|
| Season phenology: |
average
|
|
|
Weather conditions: |
| The spring of 2006 was characterized by a normal snowmelt at the Base-camp although the conditions during the critical period of goose arrival and egg-laying were quite variable. Air temperature averaged 0.17øC between 20 May and 20 June (0.30øC above normal) and was especially mild during the period of goose arrival and just before at the end of May. In contrast, the temperature turned cold during the normal period of egg-laying (average of 0.97øC during 1-15 June, 0.40øC below normal). Snow depth on 1 June was 29 cm compared to a long-term average of 31 cm. However, there was some indication that snow may have been deeper at the Camp-2 (i.e. in the goose colony) than at the Base-camp and thus that snow-melt may have been slightly delayed there compared to previous years. Precipitation was low in June (17.5 mm of rain), moderately high in July (64 mm) but mostly concentrated during the first 5 days (39.5 mm) and low in August (13 mm up to 21 August). Weather in most of July and August was exceptionally good with lots of sunshine and warm temperature.
|
|
|
|
|
|
|
|
| Date of ice-break on
rivers: |
|
|
| Date of final loss of
snow: |
|
|
BIOTIC
CONDITIONS
|
| Rodents abundance evaluation: |
low
|
|
|
Breeding conditions:
|
We found 10 new fox dens on the island in 2006, bringing the total to 120 known denning sites. Among the 115 dens that were visited this summer and found to be intact (a few denning sites are destroyed by erosion and collapse every year), we found signs of activity (fresh digging and/or footprints) at 33 of them, a relatively low number. The breeding activity of foxes was very low as we found only 2 different litters (2% of known denning sites) of Arctic Foxes and none of Red Foxes. Two Red Foxes were observed using a den but no young were seen. The level of den use was lower than last year (7% of dens used in 2005) and typical of the proportion of fox dens used in previous years of low lemming abundance (~2-3%). Minimum litter sizes were 1 and 5 pups. A total of 19 adult and 6 juvenile Arctic Foxes were captured during trapping sessions and marked with ear-tags. We also recaptured 5 adults that had been marked in previous years and we resighted 4 foxes that had been ear-tagged in previous years.
We found 17 nests of Glaucous Gulls, 6 nests of Long-tailed Skuas, 1 nest of Parasitic Skuas. Nesting success (proportion of nests successful in fledging at least one young) was moderate for gulls (38% vs 80% in 2005) but was very low for Skuas (0% vs 8% in 2005). Therefore, nesting success of all these species declined compared to 2005. Average clutch size was 2.1 eggs for gulls (vs 2.9 eggs in 2005); data was insufficient for Skuas. No Snowy Owls were found nesting in our study area in 2006.
The number of geese counted on the hills surrounding the Base-camp Valley (the first area used by geese upon arrival) increased from 165 pairs on 1 June to a peak of 580 pairs on 7 June. These values were about twice the number observed in 2005 and were actually among the highest values ever recorded. This indicates that geese arrived relatively early and in large numbers on Bylot Island this year.
Median egg-laying date was 14 June, which is later than the long-term average. Our field observations indicate that the nest density in the colony was lower than the year before and thus that the reproductive effort of geese was relatively low at the main colony (Camp-2). No nests were found at the Base-camp Valley (predominantly a brood-rearing area), a situation common in years when no Snowy Owls are nesting and lemming abundance is very low. Average clutch size was 3.68, which is very close to the long-term average. Nesting success (proportion of nests hatching at least one egg) was low this year (42%, a value below the long-term average). Activity of predators at goose nests, especially Arctic Foxes, was higher than in 2005. Peak hatch was on 10 July, which is slightly later than the long-term average.
The gosling:adult ratio among geese captured at banding (1.03:1) and mean brood size toward the end of brood-rearing (2.2 young, SD=1.11, n=144; counts conducted from 30 July to 3 August) were lower than the long-term averages. By combining information on brood size and young:adult ratio at banding, we estimated that 67% of the adults captured were accompanied by young, also a low value compared to the long-term average, which suggests a high mortality rate of young during the summer. Overall, these results are indicative of a relatively low production of young on Bylot Island by the end of the summer.
Although the phenology of migration appeared to be early in 2006 (i.e. geese arrived on the island in large numbers relatively early), they initiated laying relatively late and their reproductive effort (i.e. nest density) tended to be low. The cold temperature at the onset of egg-laying may be the main reason of the reduced nesting effort.
Egg predation was high this year and resulted in a low nesting success of the geese. Predation rate on goslings was also apparently high as shown by the small brood size (despite a normal clutch size to start with) and especially the large proportion of total brood loss. Predation is the most likely cause because weather conditions during brood-rearing were favourable and plant production was high. The combination of all these effects (i.e. low reproductive effort, late laying, high predation rate on eggs and goslings) lead to a low young:adult ratio at banding, which is indicative of a relatively poor production of young on Bylot Island this year.
The most abundant shorebirds were the White-rumped Sandpiper (20 nests) and the Baird's Sandpiper (33 nests). American Golden Plovers (6 nests), Pectoral Sandpipers (2 nests), Common Ringed Plovers (1 nest), Red Phalaropes (1 nest), Black-bellied Plovers, Purple and Buff-breasted sandpipers and Ruddy Turnstone were also observed on the island during the summer. Clutch size of all shorebird nests monitored was 4.0 eggs. Mean laying and hatching dates were between 11 and 15 June, and 4 and 13 July, respectively. Overall, American Golden Plovers had a nesting success similar to last year (20% compared to 19% in 2005) but White-rumped Sandpipers and Baird's Sandpipers had a very low nesting success (1% and 2%, respectively, compared to 11% and 25% in 2005).
In 2006, we found a record number of Lapland Bunting nests (n=89). Large annual variations in number of nests found in part reflect variations in sampling effort, which increased in the past 2 years. Egg-laying and hatching dates of buntings in 2006 were 18 June (n=39; long-term average: 18 June) and 6 July (n=15; long-term average: 3 July), respectively. No temporal trends were detected for both laying and hatching dates. The clutch size was 5.1 ñ 0.1 eggs (n=71), slightly below the long-term average (5.3) and no temporal trend was detected. Nesting success was very low (9%, n=79) and below the long-term average (48%).
|
|
|
Rodent dynamics:
|
| During our survey using snap traps, we accumulated 1100 trap-nights at our 2 trapping sites of the Base-camp Valley from 23 July to 1 August, and 550 trap-nights at the Camp-2 from 7 to 17 July. In the Base-camp sites, we caught 1 Greenland Lemmings (Dicrostonyx groenlandicus) in the mesic site and none in the wet meadow site, and no Brown lemmings (Lemmus sibiricus) were caught, which yielded a combined index of abundance of 0.09 lemmings/100 trap-nights, a very low value. In the Camp-2 site, 2 Greenland Lemmings were caught, for an index of 0.37 lemmings/100 trap-nights, also a low value. For the third year of our live-trapping survey, we captured 47 different lemmings (compared to 55 in 2005 and 180 in 2004), of which 25 were captured more than once. However, considering that the trapping effort was 44% higher than in previous years (i.e. 144 traps/grid vs 100 in previous years), the total number of lemmings captured alive was 41% lower in 2006 than in 2005. We captured 12 Brown Lemmings and 11 Greenland Lemmings in the mesic habitat, and 10 Greenland and 14 Brown ones in the wet habitat. Both indices of lemming trapping therefore suggest that lemmings continued to decline in 2006 in the Base-camp Valley and that lemmings were in the low phase of their cycle.
|
|
Rodent species recorded:
|
| Latin | Abundance |
|---|
| Lemmus sibiricus | rare |
| Dicrostonyx groenlandicus | rare |
|
|
|
Summary
of fauna studies: |
|
|
|