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The Nature Nut

Rosamund Pojar
Evening Grosbeak adult male (Hesperiphona vespertina). (Simon Pierre Barrette/Wikimedia Commons)

So far this season I have only seen winter resident birds — black-capped and mountain chickadees, red-breasted nuthatches, woodpeckers, and a few juncos — coming to my feeder.

Also, a brown creeper showed up looking for food in the bark of the trees near the feeder. I have been wondering if we will see any irruptions of winter finches such as evening grosbeaks, pine siskins, or common redpolls this year like we have in the past.

I remember many years ago (1990-91) we were inundated with evening grosbeaks and the feedstore kept running out of black oil sunflower seed. The following year the store put in a much larger order for the seed so that they were ready for the return of the hordes of evening grosbeaks, but the birds did not show up.

Why? Probably because the large number the previous year was what is called an ‘irruption’ which is loosely defined as ‘an irregular movement of birds’ often in huge numbers.

Irruptions tend to involve northern birds that are running out of food in the north where they normally hang out and so they take off to search for it further south. When they find a well-stocked feeder, they tend to stay for a while. The winter finches are seed eaters and often irrupt following the 2–3-year masting (seed or cone producing) cycle of conifers.

Back following the big irruption of evening grosbeaks in 1990-91 there was great concern as to where the birds went because they seemed to have disappeared altogether. They were already considered a bird of concern as their numbers were declining severely, but in the end, I think I remember them showing up in northern Oregon or Washington. Sometimes they can show up in B.C. one year and the Maritimes the following year.

Note: a few evening grosbeaks will stay here year-round, and they do breed here.

One year we had the highest number of pine siskins on the Christmas Bird count in all of Canada. Some years we see many common redpolls at feeders, other years not. The redpolls however may just be out in the bush as they are especially fond of birch seeds, which have a very high protein content.

Snowy Owls also have irruptions but often after a very successful breeding season. If there is an abundance of rodents on breeding territory the owls can raise lots of young. The problem happens when the snow comes and buries the rodents, and the inexperienced young birds cannot get enough food for themselves. So, they head south.

One year (2012) we had a rodent explosion in the Bulkley Valley, so many of the young snowy owls moving south stopped here to try their luck. Many died and autopsies revealed they had almost no breast muscles left and were on the edge of starvation when they got here.

Red-breasted nuthatches (not finches, but seed eaters) are also cyclical in their abundance and tend to follow a 2, 3 or 4-year cycle in abundance.