Winter Bird Irruption

Many species of birds, including raptors, warblers, waterfowl, shorebirds and sparrows migrate twice each year, south in fall, north in spring. Not all birds migrate to the same places each year though. Some birds that breed in the boreal forests of the north come as far south as the Mid-Atlantic states only occasionally, after an absence of several winters. These irregular southward migrations are known as irruptions. Unusually large numbers of several of these “irruptive” species have reached Virginia this winter, including such beautiful birds as purple finches, red-breasted nuthatches, and evening grosbeaks.

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Purple Finch

Other irruptive species include boreal finches, like pine siskin, red and white-winged crossbills, common and hoary redpolls, and pine grosbeaks, as well as certain species of owls and raptors, such as rough-legged hawk, northern goshawk, and snowy owl. Black-capped chickadees also irrupt. These northern species rarely all come south in the same years, but it is not uncommon to have years when multiple species have large coordinated movements.

Irruptive birds move south when there is not enough food to support their populations in the north. The finches, red-breasted nuthatches and black-capped chickadees fly south because of bad conifer cone crops in the boreal forest. Snowy owls, on the other hand, seem to irrupt in years when their prey, lemmings, are particularly abundant. While these irruption triggers appear contradictory, they really are not. In both cases, relative scarcity of prey to predators causes a food shortage. The snowy owl population explodes from the plentiful food to the extent that the lemming population can no longer support them all come winter, so they come south in search of food.

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Pine Siskin. Photo by Drew Chaney.

Irruption is closely tied to a cyclical fluctuation in the seed crops of trees the birds depend on as winter food sources. Birches, alders and conifers in the boreal forests— all important food sources for irruptive songbirds — do not bear equal seed crops every year. “Mast” years when lots of seeds are produced are followed by several years of poor seed production. This appears to be an evolutionary strategy to limit the populations of creatures that eat the trees’ seeds to ensure the maximum possible number of seeds survive. In good seed crop years, seed eaters do well, and their population expands. When the next year’s crop is poor, there’s even less food for each animal than there would have been if the population hadn’t grown the year before, and the population falls. Then, when the next good year comes, there are not enough animals to fully capitalize on the seed crop, and some seeds escape. Oaks, hickories, and beeches in the deciduous forests of the East have similar cyclical fluctuations in seed production.

The winter of 2018-2019 is an irruption year for many species of boreal birds. Red-breasted nuthatches started moving south into Virginia as early as August. I saw my first of the season on August 19th in Sussex County. By September they were abundant throughout the state, with several migrating individuals being observed each day at the Rockfish Gap Hawk-watch in Augusta County. Starting in September and October, the nuthatches were joined by large numbers of purple finches and pine siskins. Numbers of these three species dropped significantly by December, but they remained present throughout the state. Many evening grosbeaks and even a couple of common redpolls have also been found in Virginia this year.

Few of the irruptive finches are as beautifully colored or as interesting as the evening grosbeak. Evening grosbeaks were fairly rare in eastern Canada over 100 years ago. Their population exploded about 60 years ago, which corresponded to a major outbreak of their preferred summer food — the spruce budworm. During the mid to late 20th century, they irrupted in huge numbers, sometimes with hundreds in Virginia at once. Since then, their population in the East has crashed, possibly due to habitat reduction from logging in the boreal forest, increased diseases, or decreased spruce budworm populations. As the evening grosbeak population has declined, they’ve irrupted in smaller numbers. So far, this winter has been relatively great for them though, with many having been seen at feeders around the state.

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Evening Grosbeak

Bird feeders are a particularly good way to see some of the beautiful finches that will be visiting our region this winter. Almost all of them like black-oil sunflower seeds. Pine siskins and redpolls — if we should be lucky enough to have more of them this winter in Virginia — particularly like nyjer or thistle seed. My brother and I recently put up a large platform feeder full of black-oil sunflower seeds in hopes of attracting an evening grosbeak, as they apparently prefer platform feeders to tube feeders. In all probability, we won’t see one on our feeder this winter, but you never know!

Sources

Pittaway R. (2014, September 20). Winter Finch Basics. Retrieved from http://www.jeaniron.ca/2012/winterfinches.htm

Pittaway R. (2018, September 20). Winter Finch Forecast 2018 – 2019. Retrieved from http://jeaniron.ca/2018/wff18.htm

Ehrlich P. R., Dobkin D. S., & Wheye D. (1988). Irruptions. Retrieved from https://web.stanford.edu/group/stanfordbirds/text/essays/Irruptions.html

Shaw D. W. Bird Irruption: A Sudden Surge of Birds. Retrieved from http://www.birdsandblooms.com/birding/birding-basics/bird-irruption-surge/

Cornell Lab of Ornithology. Evening Grosbeak Life History. Retrieved from https://www.allaboutbirds.org/guide/Evening_Grosbeak/lifehistory

Mortensen R. (2012, November 7). Birders Can Contribute to Evening Grosbeak Science Right Now! Retrieved from http://blog.aba.org/2012/11/birders-can-contribute-to-evening-grosbeak-science-right-now.html

Devokaitis M. (2018, November 6). This Could be the Winter You Get Evening Grosbeaks at Your Feeder. Retrieved from https://www.allaboutbirds.org/this-could-be-the-winter-you-get-evening-grosbeaks-at-your-feeder/

The Great Ptarmigan Hunt

Since I began researching birding in Glacier National Park nearly a year ago, one of the birds that I most wanted to see was the White-tailed Ptarmigan.  I liked that Ptarmigans are unusual — rare, range -restricted, cute quail-like birds.  Ptarmigans live in harsh, alpine environments far above the tree line.  Getting up to their snow-covered habitat in late June, when we were going to the park, could be a challenge.   They have thickly feathered feet and even feathers around their nostrils to help them deal with the cold.  Every winter, they molt out of their speckled brown breeding plumage into a beautiful snow white plumage for camouflage against the snow.  These specialized adaptations have helped ptarmigans survive the cold, northern winters for millennia, but in a rapidly warming climate, they could be fatal.

When I was researching Glacier, I bought a bird finding guide called “Glacier is For the Birds” by ranger and biologist David Benson, who studies the effects of climate change on White-tailed Ptarmigans in the park.  The book was very useful in learning what birds we could expect to see on the different trails, and more generally, some basic ecology of the park.  While we were at Glacier, we had the opportunity to go on a bird walk with Dr. Benson.  We had already seen all the common birds in the area of the walk, but we went for the chance to pick his brain about ptarmigans and couple of other target birds.  He told us that the best place to see White-tailed Ptarmigans in the park was Logan Pass, but that this was a difficult time of year, since the Going-to-the-Sun Road (the only way to get to Logan Pass) was closed to all vehicles due to snow.  Also, the ptarmigans don’t have chicks or flock this early in the year, so if we saw one, it would likely be by itself.  He didn’t sound very encouraging. When we pressed him about our chances, he kind of raised his eyebrows and said,  “Well, you can try ….” He said to scan every patch of exposed rock downslope from the Hidden Lake Nature Trail, and if we didn’t find ptarmigans there, to walk up and scan the higher rocky patches.

Dr. Benson also pointed out that, unfortunately, there were less White-tailed Ptarmigans at Logan now than there used to be, probably because of declining moisture levels due to climate change.  At this point he thought there were only about 16 breeding adults left there, less than half the number that had been there 50 years ago.  Ptarmigans get stressed by temperatures over seventy degrees, and need snow or snowmelt to cool themselves down.  Less snow and earlier snowmelt makes it harder and harder for them to cool themselves down sufficiently.

Three days previously, we had attempted to find Ptarmigans at Piegan Pass, a high pass through the mountains separating the center of the park from Many Glacier where we were staying.  According to Dr. Benson’s book, a small number of Ptarmigans could be found along the barren, rocky top of the ridge line at the pass.  The five mile hike to Piegan Pass from Jackson Glacier Overlook where we left our car was almost deserted.  Flocks of Pine Siskins and Cassin’s Finches foraged on the clean white snow beneath the stunted forest of Sub-alpine Fir.  The mountain felt pristine and peaceful, exactly how I had always dreamed of mountainous coniferous forests.  I saw the blur of a wing out of the corner of my eye.  Turning I caught a Boreal Chickadee slipping into a fir.  Soon we were surrounded by Boreal and Mountain Chickadees, and Red-breasted Nuthatches.

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Boreal Chickadee (Poecile hudsonicus)

It wasn’t long before the poorly traveled trail completely disappeared into the snow.  We wandered towards the wall of mountain peaks up ahead, trying to find a footprint that might show where the trail went.  The first people we met were two cross-country skiers, apparently miffed that a family of hikers was attempting to get to the pass.  They told us that they wouldn’t recommend traveling the trail without “trekking boots” or skis.  They emphatically gestured to the snow covered treeless peaks and said the Piegan Pass trail crossed “dangerous snow fields.”  We hoped they were exaggerating.  As we continued to flounder about, trying to find the trail, we heard a loud, raucous noise from the dark sky above us.  Looking up, we saw two large, gray birds with black wings swooping between  tall spruce trees.  We felt cheered by the Clark’s Nutcrackers, another life bird to keep us going.

Upon emerging from the trees, we were surrounded by steep slopes of flaky red and brown rocks, and the occasional stunted fir that managed to survive the harsh conditions.  We could see the trail crossing the peaks in front of us – a thin, straight line, mid way up the steep slopes.  Once we had climbed up to the trail, we could see the whole valley below us, and in the distance, Siyeh Bend in the closed portion of Going-to-the-Sun Road.  Periodically, thick bands of icy snow crossed the path, from the exposed peaks down to the trees far below.   The only birds we saw were two Mountain Bluebirds huddling near the tree line.  As we crossed one of the snowfields, our shoes barely digging into the steep, slippery surface, a man carrying a large backpack came around the bend.  He was extremely exuberant and cheerful about the difficult hiking conditions, in stark contrast to the skiers we had met earlier.  He told me and my brother that the “funnest thing to do in the park” if we had snow pants and an ice axe, was to slide down the snowfields all the way to tree line and meet up with our parents at the bottom of the valley.

Continuing along the path, we stumbled and slid over three more ice sheets with the wind roaring up from the valley and pushing us against the mountain wall.  We almost made it to the pass, stopping periodically and scanning the hillside on either side of us for Ptarmigans.  We knew they might blend in perfectly with the surrounding rocks and didn’t want to miss one in plain sight.  Right before we got to the pass, a steeper ice sheet stopped us.  We were so close, but still just too far to clearly see the rocks there with our binoculars.  How infuriating!

The thought of traveling back over the exposed, icy snowfields with the wind whipping up the valley harder than ever and back down through the snow-covered forest sounded hellish.  Alas, we did not have snow-pants and an ice-axe to slide all the way down!  Still, when we peered down to the road with our binoculars it looked like if we bush-whacked straight down we would encounter a lot less snow.  Once we came out on the road at Siyeh Bend, we could walk back to our car.  We followed the trail back only until it wasn’t too steep to go straight down the mountain.  As we made our way down the rocky slope, my brother suddenly called from ahead that he saw a Gray-crownd Rosy-Finch.  I nearly broke my ankle trying to get to him before it flew away.  It was the first time I had ever seen a Rosy Finch, and I was extremely happy about it.  Several hours later, we emerged on the road, having had an adventure, but not having seen a Ptarmigan.

Earlier in the week, a ranger told us that we could hike four miles from the road closure up to Logan Pass along the Going-to-the-Sun road on weekends, but not on any other days (due to work crews on the roads).  Since we were flying home on Sunday, this meant that if we wanted to go to Logan Pass, Saturday was our last chance.  We got to the Jackson Glacier Parking lot before almost everybody else Saturday morning.

Starting out on foot, the road was wet with dew and early morning rain.  Suddenly, I heard something rustle in the brush to the side of the road.  I drew back as a mother Grizzly Bear and her cub walked across the road.  I was so intent on watching them that I forgot to reach for my camera until it was nearly too late.  I did manage one good shot of the cub as they disappeared into the trees on the other side of the road.

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Grizzly Bear Cub

We enjoyed the views of the many valleys, mountains, streams and glaciers as we walked.  The only people we saw were a few bikers.  The four miles went by surprisingly quickly, and we soon found ourselves at the Logan Pass Visitor Center, which was closed.  The mountain air was clean and sharp.  The 8 foot high Sub-alpine Firs that had been growing over the last half mile of the road finally stopped, giving way to pure, white snow.  A four foot snow pack covered the ground, running from the visitor center all the way up and over the giant mountains in the background.  Every so often, a small patch of rocky alpine vegetation poked out of the snow.  The White-tailed Ptarmigans live in these patches, apparently very rarely walking on the snow or in vegetation taller than themselves (thank goodness!).  We followed the rough location of the Hidden Lake Nature Trail by walking on top of the snow, which was frozen enough to hold us up.  With excitement mounting, we began to search the lower patches for Ptarmigans.  White-crowned Sparrows and Slate-Colored Fox Sparrows foraged in the melting snow on the edges of the rocky patches, along with American Pipits, Cassin’s Finches, and Gray-crowned Rosy Finches, which finally let me get them in good lighting for photos.

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Gray-crowned Rosy-Finch (Leucosticte tephrocotis)

After thoroughly scanning the lower patches, we headed up the trail toward the towering peaks and large alpine slopes.  After having searched for over an hour and not having had any luck, I was beginning to get discouraged.  Climbing over the snow up the mountain was hard work.  The sun had come out, and it was getting hot, and since we were on snow, it was also getting extremely, glaringly, bright.  I decided that if we were going to search thoroughly, somebody should really go up above the rocks and check them from the top.  Climbing the mile or so it took to get there was probably the hardest hike in my life.  My boots dug into the slippery snow down to a good six inches and it got steep.  There would be an extremely steep segment and then it would level out again for awhile, before getting even steeper.  I was hiking over four feet of snow in a short-sleeve shirt.  As I got closer to the rocky patches, I could see the little dots that were my family far below me.  Looking out over the snow plain below me from 7,250 ft above sea level, I could see far beyond the Logan Pass visitor center and into the valley beyond it.

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Logan Pass Photo Credit: Galen Staengl

I began scanning every rocky patch for Ptarmigans and working my way back along the ridge toward the pass.  Soon, I had thoroughly seen every bit of four of the rock piles, so I started making my way toward the fifth, a small cliff like face further out in the sea of snow.  My dad, who had been scanning through our spotting scope, suddenly yelled, “I see one!” I began skidding down the mountain toward my family faster than I ever would have without such incentive.  When I got to the scope a few minutes later the Ptarmigan hadn’t moved (of course it hadn’t, it was sitting in a little indent in the cliff face and nonchalantly pecking at the dirt in front of it).  As I looked at the cute little bird, I felt that I could finally let our trip be a success. We had seen our three most important targets, Gray-crowned Rosy-Finch, Boreal Chickadee, and White-tailed Ptarmigan.  We had also seen many other beautiful new birds and endless gorgeous scenery.  I wasn’t able to get a very good photo at that distance, but my brother got some decent ones.

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White-tailed Ptarmigan (Lagopus leucura) Photo Credit: Theo Staengl

We watched the bird for a half-hour, and then headed back toward the road to get to Kalispell so we could get a good night’s sleep before our 5:30am flight home the next day.