Whistler Naturalists

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Whistler’s autumn bird migration — How did it fare?



Autumn is the most interesting period to observe the birds if you are lucky enough to be on a busy migration route. The Sea to Sky corridor lies within the Pacific Flyway. Birds from the western Arctic islands, north coast of Yukon and Alaska, and the McKenzie Delta region, as well as those who spend their summer in the interior of this province and the Yukon, move north to south in this flyway to disperse again in the southern United States, Mexico, Central America, Caribbean and South America for the winter.


For some species the migration begins in late summer, whereas others, as I write, are the stragglers who pass through Whistler in December or even early January. This year, the straggling and/or departures have been prolonged because waterfowl in particular have been reluctant to leave an unseasonably warm interior. Another factor may be the extraordinary autumn sockeye salmon runs in the Fraser Basin which have provided an abundance food for some species.


The "Checklist of Whistler Birds" (175 species, published 1996) indicates the potential presence of 139 species in autumn, which includes migrants, visiting vagrants from the Pemberton and Squamish region, and the 42 known to inhabit Whistler over the winter. Since 1996 about 50 species have been added to Whistler’s list, some of which are autumn migrants who rarely use the Sea to Sky corridor. For the time being we will ignore the late summer migrants and the recent additions to the list and focus on the 139 species, of which 97 are migrants and casual visitors from nearby lowlands. How many species in all were seen in the autumn of 2002? We have reports and good sightings on 92, of which 35 are the winter residents, although the migrating Trumpeter Swan had yet to stop at Whistler this year for winter residence. They showed up on the first day of winter! So, the percentage recovery of sightings is an overall 66 per cent, or 83 per cent on the local residents, and 51 per cent on the 57 observed migrants and casual visitors.


And now the "ringers" in the computations: of the missing 40 migrants, 31 were last sighted and had apparently migrated out of Whistler in the period of late July to early September, "jumping the gun." So the 31 + 57 tally up to a 91 per cent recovery on the listed "autumn" migrants.


Since list preparation, however, several other species have been added to the inventory. Within this group we saw five species this year: Rough-legged Hawk, Yellow-billed Loon, Peregrine Falcon, California Gull and the Semi-palmalated Sandpiper, bringing up the tally to 93 species passing through. Finally, we saw two new autumn birds this year: American Black Duck and Blackpoll Warbler, which probably should have been on the Mississippi flyway but strayed off course. For that matter, some other new additions to the checklist seen over the summer were probably in the migration mode: Says Phoebe, Bluegray Gnatcatcher, Tennessee Warbler, Northern Waterthrush and Hutton’s Vireo. This brings the tally to 101 migrant species and casual visitors.


In the autumn period, however, the total species count for 2002 is the 92 of those shown on the checklist, plus the five on the amended additions (up to 2001) and the two new ones, or 99 in all, plus a possible Western Screech Owl if we ever receive a confirmation on where it was found.


What were the high and lowlights of the autumn period? The obvious were the persistent appearance of the Long-billed Dowitchers on the mud flats at the mouth of the River-of-Golden Dreams on Green Lake. Each day for several weeks, three or more could be seen probing the mud in sewing machine-like action. On one day there were 14 and on several days they were joined by a few Wilson’s Snipes (a.k.a. Common Snipe). A flock of rarely seen Western Meadowlark and two Townsend’s Solitaires also stopped-over on this delta.


Among the waterfowl, there were some oddities. Diving Ring-necked Ducks were seen almost exclusively on golf course ponds and Alta and Alpha Lakes, whereas dabbling American Widgeon preferred Green Lake.


It was a good season for loons: Yellow-billed and Pacific were spotted on several occasions, along with almost daily sightings of the Common on both of the large lakes.


An invasion of migrating Robins were with us for most of October, but other song birds were relatively few in number, and the colourful Varied Thrush has all but disappeared throughout southwestern B.C. with very few sightings anywhere.


A large flock of Western Bluebirds were actually seen in the alpine zone on Whistler for a first autumn record; they had not been seen at Whistler in any season for several years.


Other autumn absentees were Turkey Vultures, Redhead Duck, Willow or Rock Ptarmigan, several shorebird species, Bonaparte’s Gull, doves, two or three owl species, Cliff Swallow and the American Redstart. However, most of these are rare occurrences at the best of times, and our limited observation periods each day would not necessarily pick them up.


All in all, the migration season was successful, but limited in numbers for most species that use the Sea to Sky corridor. Undoubtedly, many migrants prefer to use the Lillooet-Harrison Lakes corridor. Overall the migration was slow for most species because of the prolonged warm season experienced in especially the interior of B.C. and the Yukon.


Written by: Karl Ricker


#Fauna

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