Boreal birds

The Boreal Forest (also known as the taiga) is a harsh place, dominated by snowy landscapes, primarily coniferous trees, extremely cold and long winters and short-lasting, cool summers, but it is the largest land biome circling the high northern latitudes of the globe. In North America that includes most of inland Canada and Alaska.

Boreal forests are dominated by conifers, and usually have an understory of moss or lichen. The coniferous forests of northern Minnesota aren’t really part of the boreal biome, being warmer year round and having many fruit- and seed-bearing plants in the understory. This is an important difference for boreal-dwelling birds.

Over 300 species of birds breed in the boreal biome during its short summers with almost continuous daylight and abundant supply of insects, but only about 30 bird species stay for the rest of the year. In years when food resources are scarce during the winter, some boreal-dwelling bird species “irrupt” and make short migrations south to the northern coniferous forests in Minnesota and other parts of the U.S. These irruptions are irregular both in timing and location, but we can usually find a few boreal species in the spruce-tamarack forest of Sax-Zim bog.

Boreal Chickadees are one of the species that may desert their boreal habitat in search of food in coniferous forests further south. Some years they are never seen during the winter at Sax-Zim bog in northcentral MN, and some years they can be found in abundance. This year, there seemed to be just one Boreal Chickadee hanging out at this particular feeder.
Boreal Chickadees look very similar to our familiar Black-capped Chickadees, but they have a brown cap, gray cheeks, and rustier sides, and their calls are distinctly different. Besides being geographically separated by occurring further north than the Black-caps, Boreal Chickadees prefer to spend their time at foraging at the top of spruce trees, while chickadees forage much lower and in a variety of conifer or deciduous trees. However, their ranges do overlap in the boreal forest, and there is at least one report of a hybrid produced by interbreeding of the two species.
Pine Grosbeaks breed in the farthest northern reaches of the boreal biome across northern Canada, but may retreat to the southern parts of the biome and northern coniferous forests in MN for the winter where they dine on a variety of seeds from feeders and from the understory vegetation of the forest.
These large-bodied, colorful finches are entirely vegetarian: they crush large seeds and fruits in their bills or may nip the tips of the needles off pines or firs. The birds vary in color and even in size throughout their range, which extends around the globe in the boreal biome. Males are pink to rosy red in color and the females have variable amounts of copper color on the head and breast.
Evening Grosbeaks are another large-bodied finch that breeds in the boreal region, and like Pine Grosbeaks, they retreat south during the winter, often in large flocks. Their irruptive movements during the winter are unpredictable and irregular, and they might be found as far south as Texas.
Evening Grosbeaks consume seed in the winter, but are ferocious consumers of insects in the summer, especially spruce budworm. Males in their bright black and yellow plumage really stand out in the gray winter landscape. Females sort of resemble the smaller Goldfinch females with their black and white wing feathers.
Canada Jays (well named because they are found almost entirely in just Canada, unlike the Canada Goose!) stay in their boreal homes year-round, tolerating whatever the climate throws at them. They are well-adapted to the cold, with dense plumage, short beaks, and even feathers that insulate their nostrils!
The best way for Canada Jays to survive the boreal climate is to eat whatever they can find: berries, insects, small mammals, nestlings of and sometimes adult small birds like chickadees, carrion, even fungi. Like some other coniferous forest residents, they store food year-round securing it under bark and in crevices with their sticky saliva. Canada Jays adapt to human presence easily, making use of their food stores (like a hanging deer carcass) and inspiring colloquial names like “camp-robber” and “whiskey-jack”. Do they really sample the alcohol?

Other notable “irruptive” species one might find in the northern coniferous forests of MN like the White-winged or Red Crossbills, Bohemian Waxwings, Red-breasted Nuthatches, Purple Finches, Common or Hoary Redpolls, Pine Siskins, as well as Snowy Owls and Great Gray Owls, all make winter excursions “up north” an exciting adventure in bird watching.

the Great Gray

A trip to the land of gray skies, little light, dense spruce and tamarack bogs, and chilly temperatures in north central Minnesota gave us an opportunity to see one of the most iconic animals of the northern Boreal forest, the Great Gray Owl, in action, doing what it does best — hunting mice under the snow.

[Note added after posting: if you’re interested, read the comments below the post for more information about the Great Gray Owl hunt]

A brief glimpse of the sun at sunrise was the only time we saw it during the entire time we were in this gray landscape, where the intensity of light in the dense overcast was about 1/50th of what it would be on a sunny day.
You have to look really carefully at every snag as you drive down the snowy roads of the black spruce forest where Great Grays like to hunt. The owls blend in so well with the conifer bark, they often go unnoticed.

Great Grays are the largest (by total body length, not weight) owl in North America. Their over-sized heads with huge facial disks are essential for hearing what is going on under the snow cover.

Great Gray Owls are mouse specialists, adept at crashing through crusty or powdery snow to depths of 18 inches to snare a vole in their talons.

The arrangement of facial feathers in two parabolas collects infra-sounds of mice running through their burrows under the snow cover and reflects it to their asymmetrically placed and shaped ears. The intensity and time difference of sound arriving at their two ears allows the owls to “focus” on the direction of the sound.

They scan the landscape under their perch by moving their head back and forth to hone in on the sounds of mice under the snow from up to 100 feet away, then quickly descend to the ground to trap their prey, completely silently. The mouse never knows the owl is coming.
Despite weighing only 2.5 pounds, these owls can break through snow crust strong enough to hold a human’s weight to get at the prey hiding below. Sharp talons snare the mouse, and the owl can quickly bring it up to its head and swallow it, head first.
Their hearing is so acute, they are able to successfully capture their prey about 60% of the time. In fact, they are more successful catching voles through snow than they are at catching gophers through loose dirt in the summer.
Great Gray Owls can hunt visually as well, and can cover hundreds of feet distance with a burst of wing flaps to grab a vole or mouse off the surface of the snow, and carry it off.

Tiny mobsters

Forest walk, Sax-Zim bog, Meadowlands MN

Forest walk, Sax-Zim bog, Meadowlands MN

We got a good demonstration of just how many tiny birds were present in the woods alongside roads in Sax-Zim bog, when our guide (Clinton Nienhaus, head naturalist at the bog) briefly played the call of a Screech Owl.  Within a couple of minutes, dozens of Black-capped Chickadees and Red-breasted Nuthatches appeared, calling continuously to sound the alert of a predator’s presence.

Red-breasted Nuthatch

Red-breasted Nuthatch, one of about a dozen, sounding the alert in response to a Screech Owl call.

Weighing in at a whopping 10 grams (less than a fast-food packet of ketchup), tiny Red-breasted Nuthatches are just a bit smaller than Chickadees, but even a small bird with that sharp-pointed beak could do some damage at close range.  In any case, the point of the mob action is to pester the would-be predator enough that it eventually flies away.  Mobs of small birds may also attract larger birds like jays and crows to help drive off the predator.

Red-breasted Nuthatches mobbing fake owl

Red-breasted Nuthatches and chickadees flit from branch to branch looking for the owl.  Since I have only ever seen a single or a pair of nuthatches at one time, this was a real treat to see so many of them in action.

Red-breasted Nuthatches prefer coniferous woods, like the black spruce and tamarack of the bog.  In the spring and summer, they are highly insectivorous, but like the chickadees, in the winter they love the peanuts and suet found at bird feeders.  Even though they are one of the smaller birds at the feeder, their feisty, aggressive behavior often drives bigger birds away.  Like their cousins, the White-breasted Nuthatch, they will store some of the feeder largesse in tree crevices for a snowy, cold day.

Red-breasted Nuthatch

Looking up, looking down….where is that owl?

Sax-Zim bog is one of the premier birding areas in Minnesota, attractive to a number of Canadian breeding species like the Great Gray Owls and Hawk Owls, as well as northern breeding finches during the winter.  The farm fields filled with hay bales seem to be filled with mice and voles, perfect for raptors, and the dense spruce-tamarack forest provides good cover.  The Friends of Sax-Zim bog have established a welcome center where one can get a map, advice on where to search for some of the more exotic species, and even guided field trips to help you spot those elusive birds.

Field trip Sax-Zim bog, Meadowlands MN

Field trip Sax-Zim bog, Meadowlands MN.  We stopped here to check on the presence of Redpolls and other small finches.  Alas, only one Redpoll appeared, and only very briefly and far away.

For more information about the bog, visit their website (link above) or check out the photos and commentary of one of the founders of the organization, Sparky Stensaas at The Photonaturalist.

…not a creature was stirring…

North of the Twin Cities of Minnesota about three hours drive is a vast boggy patchwork of black spruce-tamarack forest and open prairie/cropland that is the winter home of some of the raptors that breed in the Canadian tundra.  We visited there over the weekend hoping to see a few Snowly Owls and Rough-legged Hawks, the chief avian predators of the open fields between the swampy areas of Sax-Zim bog.

Birch-aspen forest in Sax-Zim bog, MN

We had high expectations of seeing our target species in these open fields on a frosty morning, when the thermometer hovered around 7 degreees F and the tips of the trees were covered in hoar frost.

Hoar frost

What little moisture is in this frigid winter air condenses into icy coatings on exposed branches when temperatures dip below the dew point at 7 degrees F.

Cropland in Sax-Zim bog, MN

Looking high in the trees for the hawks and low on the hay bales for the owls, we traversed the bog and crop lands searching for raptors. A Snowy Owl should be perched on one of the hay bales…

Cropland in Sax-Zim bog, MN

But not a creature was stirring. In fact, there were no birds of any sort flitting about. It was unnaturally still!  Rough-legged Hawks should be perched in one of the trees lining the open fields searching for mice…

Alas, a four-hour search turned up just one hawk, seen at a distance of about 1/4 mile, and no owls.  But there was a lot of photogenic scenery along the way (more on that next time…)

The next day we did find a Rough-legged Hawk perched right by the side of the road, overlooking a farm field of corn stubble, but the bird flew off as we drove up.  It would have been a nice photo op, something like this…

Rough-legged Hawk, Wikimedia Commons, photo by dfaulder

Rough-legged Hawk, (Wikimedia Commons, photo by dfaulder).

Heavily streaked with brown and sporting flashy white tail feathers and densely feathered legs to keep those toes warm in the frigid winter temperatures, these medium-sized hawks hunt for mice in the open fields.  But they will attack most any bird or mammal prey they find, including rabbits and weasels, snow buntings and tree sparrows, even other raptors from whom they may steal the food.  If live food is lacking, the hawks will feed on carrion.

Voles and lemmings make up the bulk of their diet, and there is some evidence that Rough-legged Hawks can actually see the scent marks left in the vole urine which is visible in the UV.  Imagine the hawk’s eyes following trails of blue fluorescing across the snow to where a mouse hides just under the crust.  Bam!  Dinner.

Closer and closer

We were driving the country roads through Sax-Zim bog on a foggy, misty morning in northern Minnesota looking for Great Gray Owls along the side of the road, when we finally thought we had spotted one.

barred owl

But one look at those dark eyes gave it away. This was a Barred Owl, the only species of North American owl with dark brown instead of golden yellow eyes.

I was sure the owl would fly away, so I took dozens of photos as it sat there, turning its back and forth to check on us now and then.  But we drove a little closer…

barred owl

And then a little closer…

barred owl

until finally we came up right next to the bird, and it completely filled the field of view in my telephoto lens.  How often does that happen?

barred owl

Enlarging just the owl’s head, it seemed like the bird’s inner eyelids were actually closed even though it seemed to be looking right at us. I’ve lightened up the bird’s head and its eye in this photo to show you what I mean.

barred owl showing partially closed inner eyelid

Many animals have a third eyelid (the nictitating membrane), which is transparent but protects and moistens/lubricates the eye as it is pulled across when the animal “blinks”. Being well adapated to hunt in the darkness, Barred Owls often perch in the daytime with the nictitating membrane pulled across their eyes, to dim the light. It’s kind of light wearing sunglasses for them, I guess.