Pardon the irruption

Nature bummin’ with Kirk Gentalen

Common Redpoll

As if winter weren’t “cool” enough, there’ a sweet migration pattern that can supply any winter season with a unique make-up of avian species and associated population dynamics. Instead of a regular, yearly movement that many species follow (spring-and-fall songbird migration for example), the key to this flavor of migration is that it’s not repeated annually. Instead of decreasing day length and hormones inspiring an exodus, the motivating factor in these non-annual cases is a crash in food availability. A substantial drop in resources to the north can result in a southern invasion of huge numbers of any affected bird species. When occurring, this pattern is (lovingly) referred to as an “irruption,” and irruptive species in these cases can be either predators or seed-eaters.

Snowy Owl

Raptor species such as Rough-legged Hawks and Snowy Owls irrupt on somewhat regular cycles that are connected to population cycles of grassland/field rodents (four-to-five-year cycles) and snowshoe hares (10-year cycles). These are the irruptions you can count on, and are much appreciated accordingly.

On the other hand (or wing), seed-eating songbirds that feast all winter on conifer cones, catkins and fruit will all irrupt on an irregular and unpredictable basis depending on seed crop failures. “Winter finches” (Common and Hoary Redpoll, Evening and Pine Grosbeak, American Goldfinch, Pine Siskin and White-winged and Red Crossbills) are a group that irrupts under these circumstances and may show up in big numbers that light up forests and feeder stations with energy and color.

Evening Grosbeaks

The McConochie feeder system off the Turkey Cove Road in Tenants Harbor recently played host to about 50-plus Evening Grosbeaks! About the size of a robin, Evening Grosbeaks bring a striking pattern of bold yellows and black-with-white wing patches with a honkin’ seed crackin’ bill to boot! The McConochies report that they’d never seen Evening Grosbeaks on their property before and that after a week of gradually diminishing numbers the birds finally cleared out, taking their irruptive ways to new grounds.

And Evenings were not the only grosbeaks that found their way to St. George after the cold stretches and snows in the last third of autumn. Small numbers of Pine Grosbeak have been sprinkled throughout peninsula forests as well, and their calls add an alternative to the sound of a cold breeze! American Goldfinch, Common Redpoll, Red Crossbill and Pine Siskin have also been observed on the peninsula as of late, providing views of some seriously hardcore song birds (ones that regularly overwinter well north of mid-coast Maine). It’s also a glimpse into what can be assumed is a winter food shortage further north. Minor giddypation for the rest of our finchy winter and whatever else may work their way down the peninsula. But with the irregularity of it all, technically this could be it already for the winter finches. Only time will tell, and winter’s only starting today!

Pine Siskin

Another winter-fruit-reliant species with irruptive tendencies observed recently on the peninsula is the Bohemian Waxwing. While Cedar Waxwings are a common species and sight in St. George during the summer months, their northerly cousins tend to stay at upper latitudes unless encouraged (prodded) south by a lack of food. Keep an eye on local plants that hold berries and fruit into the winter, or may even be leaking tree sap for these medium-sized songbirds to feast on. Bohemians will even join Cedar Waxwing flocks that may be overwintering in neighborhoods. Picking apart a flock of Waxwings often turns up a Bohemian treasure or two this season!

When these irruptive songbirds invade an area in numbers, it’s not surprising that predator species may irrupt as well and follow the songbirds south. The Northern Shrike is a predatory songbird that makes occasional irruptions depending on both songbird and small-mammal population abundance to the north. These killers–nicknamed “butcher birds” for their habit of impaling prey on thorns and barbed wire–can send winter finches darting for their lives with fast chases and aerial pursuits. It’s a predator/prey relationship that migrates, part of a northern ecosystem that sometime visits us for the winter!

It’s good not to take things in life for granted. With the size of some winter irruptions and the associated unpredictable timing pattern they follow, it’s almost impossible to “ho-hum” these species when they arrive at your feeding station or in your neighborhood.
The season is starting off somewhat irruptive already. Let’s keep our eyes and ears open and enjoy it while we’ve got it, because with these species—who knows when we’ll see them again?

PHOTOS: Common Redpoll, Kristen Lindquist; Evening Grosbeaks, John McConochie; Snowy Owl & Pine Siskin, Kirk Gentalen

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