Naturespeak 

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.

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