Bird irrupted

For bird watchers, surprising increasxes in bird population break the same-old, same-old

SOUTH NEWFANE — Watching birds can do lots of good things for you, including expanding your vocabulary. Or at least, it has expanded my vocabulary.

Until I had the time to pay attention to seasonal changes and movements of birds, I did not have the word “irruption” in my working vocabulary. I knew “eruption,” which involves something bursting out, like lava from a volcano. Irruption refers to something bursting in, or surging up.

It is the word used by ecologists to describe a sudden, rapid, and irregular increase in an animal population. It typically involves some kind of change in the natural ecological checks and balances.

In the bird-watching world, irruptions are hoped-for events, especially as winter imposes its grip. Winter birding can be rather monotonous - the same-old, same-old - unless one or more irruptions occur.

The Great Backyard Bird Count, the website of National Audubon and Cornell Lab of Ornithology, puts it this way: “Every winter, bird watchers across North America anxiously await the possible incursion of birds that don't normally winter in their areas. These periodic bird irruptions add a dramatic level of excitement to winter birding.”

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Last winter (2011-12) was an irruptive year for Snowy Owls. These large arctic predators were reported in record numbers across the northern states, often in places where they have rarely, or never, been reported. Sightings extended deep into the Great Plains and even as far south as Texas.

The Snowy Owl irruption was driven by a crash in the population of the lemming - the owls' principal food source - in the Arctic.

When a Snowy Owl was reported in mid-December, 2011, in the corn field behind the Marina in Brattleboro, the word spread quickly through the birding community. Within an hour of the first report, a dozen birders were focusing their scopes on the white object among the corn stalks. More observers followed in a steady stream.

Finch species that inhabit the northern forests are the most common irruptive birds, and this winter has been a banner year in our area.

During October, large flocks of Pine Siskins (closely related to the American Goldfinch) moved through New England and the mid-Atlantic states. The flocks that visited my bird feeders numbered more than 200; they put a serious strain on my birdseed budget.

The siskin flocks moved on, to be followed by the Common Redpolls (also closely related to goldfinches). Throughout December and January, and on into February, there have been breathless reports about the sudden appearance of these small finches.

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What makes the winter irruptions both exciting, and frustrating, is their unpredictability. As the birds irrupt into New England, they do so in flocks - often large and typically very nomadic.

So you hear about all of these redpolls being seen, and you are frustrated because you have not seen a single one.

And then you are snowshoeing through an old hill farm, or walking along a frozen lane, or sitting in your kitchen watching your bird feeders, and suddenly you have a surfeit of redpolls scratching the snow, squabbling over seed, and taking hurried flights into the hedges.

Winter finches are notorious for quickly exhausting a food source and then moving on. The epitome of this practice is exhibited by the Evening Grosbeak.

Longtime bird feeders describe the Evening Grosbeaks's winter presence with ambiguity. They are delighted to have these large, colorful, and handsome finches at their feeders, but they cannot avoid the additional use of adjectives such as “voracious” and “greedy” to describe their presence. This winter, Evening Grosbeaks seem to have taken their blitzkrieg feeding habits farther south; I have seen few winter reports from our area.

The winter finches that are typically more common in our area have been hard to find this year. In addition to the siskins and grosbeaks, which have moved on, Purple Finches and goldfinches are scarce.

But then there are the frustrating reports of other winter finches - frustrating, because you would love to see them, but they do not make it easy.

For a couple of weeks in December, a flock of Pine Grosbeaks fed on the yew berries in front of Centre Congregational Church in Brattleboro. There were females and young males. (The adult males apparently stayed home to defend their territory through the winter.)

When the berries were exhausted, the flock moved on.

On the Christmas Bird Count, we came across several Pine Grosbeaks getting grit and salt on a road in Dummerston. If you have not seen the Pine Grosbeak, you might still have the opportunity. Be alert, because they could be anywhere.

But if you miss the Pine Grosbeak this winter, I am sorry to tell you that you might not have another opportunity for several years. But, that's bird watching.

On the New England coast, this has been a good winter for Red Crossbills and White-winged Crossbills. I made a trip to Salisbury Beach on the New Hampshire coast and had my best crossbill day ever.

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Winter irruptions are driven by conditions in the northern forests. Scientists and naturalists in Ontario and the Maritime Provinces have been studying the preferred food sources of various species for years. Based on their collected data, fairly accurate predictions are possible about which species will irrupt.

When these scientists document the shortage of a food that a particular species prefers, they predict an irruption. Winter survival depends upon getting enough food. When local food sources are scarce, the birds go elsewhere.

Finches are the most common irruptive species during winter. It is easy for us to miss an irruption of the Red-breasted Nuthatch, since this species also nests in the higher elevations of our area and might be seen year-round.

Harder to miss when you come across them are the Bohemian Waxwings. When you find Bohemians among the flock of their cousins, the Cedar Waxwings, then you have counted a coup among bird watchers.

And when you meet a waxwing flock dominated by Bohemians, you have certainly encountered evidence of an irruption. And you will be breathless.

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For any of these winter irruptions, I have two pieces of advice if you are not a hardcore birder.

First, I am sorry to say, don't hold your breath. The winter flocks are nomadic and erratic. Hardcore birders sometimes spend days trying to chase them down, not always successfully.

Second, when you do stumble on one of these flocks, or when one of these flocks stumble on you, don't forget to breathe!

Good birding!

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