ENVIRONMENT | Tracking Spring Migration in the Cariboo-Chilcotin

spring migration

An Arctic tern pair at the Eagle Lake nesting colony. Photo: Jim Sims

By Phil Ranson –

May 14 is International Migratory Bird Day, which I confess holds about as much significance for me as Red Tape Reduction Day, which, incidentally, was on March 2 and I missed it. Not that I don’t have a keen interest in migratory birds. In fact, much of my spring is devoted to the sheer joy of watching birds returning after a drab winter and noting their first arrival dates. I do, however, have a problem with the much overused proclamation of Days to draw attention to issues, which in the case of declining song bird populations, surely warrant greater than a day’s exposure.

Spring migration in the Cariboo-Chilcotin begins in late February when birds on the periphery of their range begin to move back north, and continues through to early June when the last of the neotropical migrants finally arrive on their breeding grounds. In between some 250–300 species will be arriving, many to set up territory and many more to continue on to the northern boreal forests, the alpine tundra, and the high Arctic with some even continuing across the Bering Sea to Siberia.

What is it about the first birds to return on the still cool southeast winds? Aspen trees are barely budding and patches of snow remain on the shady slopes when the first migrants arrive in the valley bottoms. The male Mountain bluebird, the colour of clear, unclouded sky seems much more vivid against a backdrop of lasting winter, and the song of the meadowlark so much sweeter without the competition that another month or two will bring.

I’ve been recording spring arrival dates of birds in the Cariboo since 1998 and I’m by no means the first to embark on this undertaking. Anna Roberts, who is a founding member of the Williams Lake Field Naturalists, has been keeping bird records since she came to the Cariboo in 1958 and found there was no one else in the area doing this. She used this information to produce the first Checklist of Cariboo Birds in 1976, with a second edition coming out in 1992, which was more detailed and had bar graphs for each species to show their dates of occurrence and relative abundance.

Checklists are generally out of date the moment they return from the printers with dates being extended and new species showing up almost on an annual basis (The 1976 checklist had 248 species. The current version has 323). In the late 90s, Anna was discussing a third edition with Jim Sims, also on the executive of the Field Naturalists, who at this time was familiarizing himself with writing programming software. And so the idea of an electronic checklist was conceived, and also the beginning of my involvement in tracking arrival and departure dates of Cariboo birds.

In the mid-90s there was a loose email connection between people with varied interest in local birds. I began compiling these emails and resubmitting them to a distribution list. This distribution list expanded and the compilations were going out anywhere from daily when things were busy to maybe once a week or less during the slower winter months. This went on until 2011 when, wanting to be relieved of the responsibility and also allow for greater involvement among the correspondents, we switched to Google groups.

With the aid of the previous checklists and email search functions, I began to track first-reported return dates going back to the mid-90s. I also attempted to log departure dates, but it’s much easier to track birds first seen than the last time birds were not seen, so I gave up on the end dates. There is now over 18 years worth of data all gleaned from email correspondence and personal observations throughout the region. This information has been absorbed into the electronic checklist, which, after many trials and tribulations, Jim has up and running. The e-checklist is now much more than a spreadsheet of graphs; it also has notes of local relevance for each species, photographs by area photographers, and sound files of bird calls and song. Perhaps its greatest advantage, through the e-version we have the ability to add any new information instantly and print off an up-to-date hard copy.

So what does this information tell us? Birds in general are arriving earlier and earlier, particularly the short distance migrants wintering within North America including northern Mexico. Birds wintering in the tropics and sub-tropics seem to be less affected and their migration clocks more ‘hard-wired’ and less dependent on regional weather patterns. Lacking in this data and probably more relevant would be the timing of the peak of species migration. Individual birds arriving at record early dates may well be indicative but I have no means to corroborate this. Some birds are clearly not consulting the checklist before they set out.

Aside from empirical data and some speculation, watching the spring migration unfold captures the fascination of nature and the thrill of discovery that keeps birders heading out to view this annual spectacle. Anyone who has stood on the grasslands of Becher’s Prairie in April and witnessed wave after wave, from horizon to horizon, of undulating strings of Sandhill cranes heading for the coastal plains of Alaska, or visited Eagle Lake in the Chilcotin to view the oddly disjunctive colony of Arctic terns, perhaps the most graceful of birds, said to be the world’s longest migrants with a round trip of over 80,000 km from Antarctic to Arctic, cannot but help be filled with awe at the wonders of the natural world.

 

Phil Ranson migrated to Canada from northwest England in 1972. He worked seasonally in the Cariboo for the BC Forest Service since 1986 but made Williams Lake home in 1993. Married with two daughters and three grandchildren, Phil has been a member of the Williams Lake Field Naturalists for 30 years and is the compiler for local Christmas Bird Counts. He was also the regional co-ordinator for the BC Breeding Bird Atlas which ran from 2008–2012 (http://www.birdatlas.bc.ca/). Now retired Phil, spends a sizable portion of his spare time birding in the area.

 

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