Christmas Bird Count trends in the Sea to Sky corridor, 2003
Last week the Naturespeak article on Christmas Bird Counts noted that there are now six count circles (each 75 sq. km) within the Sea to Sky corridor. Our latest, Outer Howe Sound, joined the lineup in 2003 after several years of unofficial local counts on Bowen Island. However, the circle for the new riding encompasses the following: Lighthouse Park in West Vancouver to Cypress Bowl; Horseshoe Bay to Lions Bay; Pasley, Bowen, Bowyer, Keats and large portions of Gambier and Anvil Islands. Many islanders contributed to the count, including 19 from Gambier and 30 on Bowen – 62 field observers all told! It is a logistical challenge to pull it all together and Lewis Maingon on Gambier, the co-ordinator, did an admirable job. We thank him for collating their data used for comparative purposes in this review. Unfortunately he is leaving "Utopia" to reside in the Comox area.
For each of the six count areas the number of field observers/total species numbers/total birds counted (shown in brackets) are as follows: Outer Sound (62/97spp/10,346 birds), Squamish (26/72spp/13,681 birds), Whistler (19/56spp/6,611 birds), Pemberton-Mt. Currie (13/52spp/2,133 birds), D’Arcy-Devine (10/38spp/775 birds) and Lillooet (16/59spp/1,774 birds). Species totals include count week sightings.
The co-ordinator of the Lillooet count, Ken Wright, has found direct relationship between the number of species spotted and the number of observers, supported by the above, but it does not correlate with the total number of birds counted, as shown by the Squamish count in particular. An over abundance of one or two species can bulk up the total count, and for Squamish it was Bald Eagles (2,411) and Glaucous-winged gulls and related forms (6,861) that swelled the count.
For the Outer Sound the culprits were the Barrow’s golden eye duck (2,369) and Pine siskin (2,002), while Whistler’s record volume was fortified by yes, more Pine siskins (3,610) and yes again, Glaucous-winged gulls and allies (1,399). Subtraction of these numbers from the total yields a more reasonable blend with the trend of volume recorded for the other four counts.
The Sea to Sky corridor begins on the rich marine front in the Strait of Georgia; enters an outer Howe Sound of diverse habitats; narrows down in the inner fjord to terminate on salmon-endowed Squamish estuary; ascends to the summit divide of the Western Coast Mountains (the Pacific Ranges) at Whistler; descends to the broad Lillooet-Harrison valley floor (a mega fault zone) with intrusims of coastal climate that is the boundary to the Eastern Coast Mountains (the Lillooet ranges); ascends to a low summit divide on the latter at Gates Lake (near D’Arcy-Devine); then extends eastward to the leeward drier aspect on the mountains’ eastside to terminate on the edge of the Interior Plateau at the fault-bounded Fraser Canyon. Sage brush intrudes the scene at Lillooet, and continental climates prevail in this area.
Do the bird populations reflect this marine to non-marine, wet to dry, maritime to continental climatic trend, that along the way protrudes vertically into the alpine tundra? Are there any resident birds mutual to all count areas despite the diversity in climate and habitat? And how many species are exclusive to one area only in early winter?
The six counts of 2003 tallied 133 species in aggregate total, or less than a count at Nanaimo, Duncan, Victoria, or Ladner. The Outer Sound recorded 97 of the 133 but 19 of its species were found in all six count areas, our usual winter residents of no surprise, as follows: Bufflehead, Common merganser, Bald eagle, Glaucous-winged gull, Belted kingfisher, Downy and Pileated woodpeckers, Ruffed grouse, Northern flickers, Stellar’s jay, Common raven, Black-capped chickadee, Red-breasted nuthatch, American dipper, European starling, Spotted Fowhee, Song sparrow, Dark-eyed junco, and Pine siskin.
But there were 33 species counted at the Outer Sound, not seen elsewhere, and at least 13 of these (especially 4spp of alcids) will likely never be seen elsewhere, including Squamish.
The other 20, however, have been seen in previous Squamish counts, and at least eight should have been present this year if the weather had been only slightly co-operative (rain and spotting scopes are incompatible). The other 12, however, have been the infrequent accidental visitors at early winter, or the lingerers, which normally migrate through the entire corridor during other seasons.
Birds found exclusively at Squamish were the rare Yellow-billed loon, also seen at Nanaimo and Nanoose Bay in 2003, and Green heron --- the latter should have been in California or Mexico!
Found only at Whistler were Northern goshawk, White-tailed ptarmigan, Pine grosbeak, White-winged crossbill and Lincoln sparrow (new). All except the latter are sub alpine-alpine species and hence not readily seen elsewhere except at Whistler because of access difficulties.
Pemberton’s farm land setting, though saturated this year, yielded the only White-crowned and Golden-crowned sparrows plus a Western meadow lark. Pemberton observers found one of the very few spruce grouse in the province. These birds usually remain in dense foliage throughout the winter.
D’Arcy-Devine sighted an awesome 15 Hoary red polls, a northern species that sometimes drift south in cold winters. Some of the eastern or Interior elements of B.C.’s bird fauna were picked up at Lillooet, namely the Chukar, Black-billed magpie, Pygmy nuthatch and Cassin’s finch, but also seen were the only Kestrel, American goldfinch and Yellow-rumped warbler – all of the latter should have been in the Fraser Lowland or points farther south.
Continued next week
Monthly Bird Walk : The next bird walk will take place Saturday, March 6 th . Join Whistler experts in the monthly update of our feathered locals and migrants.
Written by: Karl Ricker