Birds by the bay

Arriving at the peak of low tide the other evening gave us some great looks at a diversity of shorebirds foraging along the shore of Eloise Roemer bird sanctuary on Alameda Island in San Francisco Bay.

Lots of Dunlin, Willets, Curlews, Great Egrets, Pelicans, Cormorants, Avocets, — wow, what a shorebird mecca this tidal area is!

A couple of Long-billed Curlews resting on one leg…

A trio of Willets…

Double-crested Cormorants, White Pelicans, and kayakers enjoy the quiet water of this sheltered bay.

Low Cormorant on the totem pole gets the small rock, I guess.

Stilts and Yellowlegs hunting in the shallows.

Greater (i think) Yellowlegs have beautifully edged wing and back feathers when you can see them up close.

Black-necked Stilts have such delicate toes at the end of those long, pink legs.

and on the grassy side of the beach, a beautiful little Western Bluebird hunting for insects in the waning light.

“smoked” turkey?

It is often said that “variety is the spice of life”, and we recognize that almost all individuals of a single animal species exhibit some variation from one another. But sometimes that variation is markedly and drastically different — and we wonder how that variation came about and what the consequences of it are. For example, we came across a large flock of wild turkey hens at Sax-Zim bog, foraging along the side of a field, almost all of them identical to one another, except….

Notice anything different in this flock?

The turkey hen on the far right is a “smoke” color morph, a bird that lacks the normal expression of the rich browns and reds we usually see in turkey feathers.

Hen turkey in early winter exhibiting the rich spectrum of blacks, browns, grays, and reds we associate with wild turkey plumage.

The smoke morph of the wild turkey plumage is largely white with dark black and brown accents. Its lighter coloration makes it stand out in the flock, but it actually blends in better with the predominantly black and white coloration of the northern winter landscape.

How did this happen? Coloration of feathers in birds is a complex process, and can be completely different in males and females (leading to the basis for why males are so much “prettier” than females). A given stretch of genetic code for feather color in birds can be “alternatively spliced” as the pigment is being expressed in newly developing feathers, leading to wildly different outcomes between the two sexes and at different times of year in male birds or between juvenile and adult birds. But that isn’t the entire explanation for “smoke” color morphs in wild turkeys.

Normal plumage coloration of wild turkey hens includes that “smoke” look in some of their wing feathers. It would seem that the smoke morph has that type of pigment expression all over its body, instead of just in the wings.

Coloration of bird feathers is largely dependent on eumelanin pigments that produce brown, black, and gray colors and pheomelanin pigments that produce yellowish and reddish coloration. Combining amounts of these pigments like an artist does with a paint palette is what results in the variety of rich color in the plumage.

The “smoke” morph plumage lacks the full expression of a lot of browns and blacks, and it has virtually no red and yellow highlights in its plumage. The morph is very infrequently seen in the wild population, occurring in only about 1 in 100 birds on average, and thus, it is a recessive mutation of melanin expression, especially pheomelanin. More interesting is the fact that the “smoke” morph seems to occur only in females, which probably means it is a sex-linked recessive trait.

There aren’t enough of these birds in the wild population to determine whether the “smoke” morph is at a distinct disadvantage in the winter, or whether they are more or less attractive to breeding males in the spring. But this color morph has been seen by turkey hunters from Oregon to Tennessee, so the mutation must occur in most wild populations.

A different sort of Chickadee

Watching Black-capped Chickadees flitting about in the vegetation in the winter, you have to marvel at how successful they are at finding food and staying warm in such a challenging environment. I wrote a lot more about this in an earlier blog post: “Baby, it’s cold out there”.

It doesn’t matter whether it’s snowing or blowing, or 20 below, perky little Black-capped Chickadees will always be around to greet the day.

But there is another cousin of the Black-capped species that winters even farther north, in even more intemperate (in the winter) habitat: the Boreal Chickadee – named for the fact that it is a permanent resident of the coniferous boreal forests of Canada and Alaska.

They are brown-headed and rusty sided, but Boreal Chickadees have the same black chin patch as their Black-capped relatives. In the winter they usually are found in small family groups, but at the Sax-Zim bog, where Boreal Chickadees show up infrequently, the birds are often single individuals, found foraging on suet.

Boreal Chickadees spend most of their time in the spruce and balsam fir forests, where they forage for insects and spiders in the middle of the trees, rather than out on the tips of branches like the Black-capped species. When food is plentiful in the summer, Boreal Chickadees will cache food items in cracks in the bark of the underside of tree limbs where it is protected from winter snowfall, and then they secure them in place with their saliva. It is thought that these storage sites are communal property of the flock, so the birds don’t have to remember exactly where they cached individual stores. This food reserve is critical to their winter survival, in addition to seeds and hibernating insects they might find. Most of their European relatives, the titmice, and Mountain Chickadees have also been observed to use food caches as a winter food reserve.

At the Sax-Zim bog feeders, Boreal Chickadees go after the chunks of animal fat instead of the seed-rich suet cakes. Fat isn’t very nutritious but it provides them with a source of calories to metabolize overnight and keep warm.

Boreal Chickadees are a little smaller than the Black-capped species, which makes staying warm in frigid weather even more difficult.

Not much is known about the behavior and physiology of this lesser-known relative of our popular Black-capped Chickadee, especially their strategy for surviving in the intemperate environment of the boreal forest in winter. I guess not many researchers are willing to brave the conditions where Boreal Chickadees live in the winter — I certainly wouldn’t!

the long-winged mouse hunter

In the Minnesota boreal forest around Sax-Zim bog, we finally found and photographed the hawk counterpart of the Great Gray Owl (from the last post). Rough-legged Hawks are also mouse specialists, but use a completely different strategy to hunt their prey compared to the owls. Where the owls use auditory cues to localize mice under the snow, these particular hawks use visual ones, even honing in on urine trails of voles, which reflect UV light the hawks can detect. Then they perch, sit and wait, and pounce when movements in the snow indicate mouse (in this case, vole) activity.

We weren’t quite sure what we were seeing early in the morning along the roadside as we drove into the bog area. From a distance in the dim light, the hawk first resembled a juvenile Bald Eagle, then the black and white facial pattern resembled an Osprey, which would have been well out of its range for this time of year. Finally, up close we saw the typical mottled plumage of the Rough-legged Hawk.

Rough-legged Hawks are the most northerly breeding Buteo (broad-winged) hawks in North America, setting up breeding territories in the far northern Canadian and Alaskan tundra areas to prey almost exclusively on lemmings there. But they leave the tundra and migrate south to boreal areas of southern Canada and the northern U.S. that have lots of marsh and prairie expanse where they can hunt for voles and other mice where there is less snow cover.

Their name might imply that they have rough scales on their legs, but it is quite the opposite. They are one of three raptors with entirely feathered legs, like owls have — insulation that is invaluable for birds hunting in extreme cold climates like northern Minnesota. This bird, from the carolinabirds.org website (photographed by Dick Daniels) is a captive, tethered with falconry jesses, but its raised wings allow you to see the heavily feathered legs.

Rough-legged Hawks have very long wings for their body size (up to 60 inches in a large, 3.5 pound female) and they are adept at soaring effortlessly over long distances to hunt for mouse activity. Winter birds on a foraging territory in Idaho had home ranges of up to 200 square miles that they traversed over the course of several days of hunting. Researchers estimated that the bird could sustain itself in the winter on a diet of about 5 mice per day. On days when hunting success was limited, the hawks did much more perching than flying, conserving energy for the next day’s hunting attempts.

Long wings give the Rough-legged Hawk a great advantage in soaring, and just cruising over the landscape looking down for potential prey. Although their diet in the summer is largely small rodents, they might prey on rabbits or grouse when they find them in the winter. (Illustration from the Crossley ID Guide to Raptors, on Wikimedia Commons)

I won’t forget this bird — we’ve made four trips to Sax-Zim bog to see it, and finally found one right next to the road, rather than sitting a 1/2 mile away or flying hundreds of feet over our heads. Its striking plumage, feathered feet, and black and white wing patterns should make it easy to ID in the future.

to catch a mouse

The best way to catch a mouse is to be a Great Gray Owl, with hearing out of this world to localize the mouse under a foot of snow, a dive bomb attack force that can break through a crust of snow hard enough to support the weight of a 180 pound man, sharp talons to grab the mouse scurrying along under all that snow, and a crushing beak that can separate the mouse brain from its spinal cord.

Behold! The mighty mouser! Notice those two parabolic reflectors of specially arranged feathers surrounding the eyes — that’s what captures the sounds of voles scurrying along their tunnels beneath the snow. Asymmetrically placed ears on the side of the owl’s skull receive sound at different times and help the owl localize exactly where the sound is coming from.

On a one-day trip to Sax-Zim bog, we were lucky to find a champion mouser Great Gray Owl hunting right next to the road along one of the boundaries of the bog. It caught and ate an amazing four mice in under an hour. In fact, it was 100% successful in its mousing attempts!

I’ve put together a series of images into a very short video, accompanied by special “hunting” music so you can enjoy what I was able to see and photograph. If you’re looking at this post in your email, you might need to go to the Backyard Biology website to view the video (click on the title of the post in your email to get to the site). The video is best viewed in full screen (rectangular icon in the lower right corner of the video as it plays), then hit ESC to return to the blog post.

In the video sequence you see the owl take off, from a perch, fly quickly to a site and dive to the snow feet first, dip its head down to the feet to grab the mouse in its beak, fluff its wings above the snow level to take off, fly to a perch, spend some time looking around (not shown in the video), take the vole’s head into its mouth and crush it, transfer the vole to its feet and squeeze it some, then back to the mouth where it is swallowed.

Great Gray Owls look around continuously as they try to localize sounds they hear coming from beneath the snow. In this image, the owl was perched about 10 feet above the snow and stared down intently for several moments before making a dive, and coming up with a mouse.

Our Great Gray caught four voles in a very short span of time. But on average they may catch and eat up to seven voles a day while hunting in the early morning and late dusk hours during the coldest winter days.

Uff-da, it’s cold

That’s what we say in the MN northland, when the temperatures drop below 0F. The other day when I ventured out in the early morning, it was -17F (-27C). When I got back in the early afternoon, it had made it all the way up to -3F (-19C), which is just barely tolerable if the sun is out and there is no wind.

And the wildlife aren’t enjoying the cold temperatures any more than I am. Little birds don’t show up at the feeders until mid-morning, and the squirrels (both gray and red) are usually found huddled next to the tree trunk with tails curled over their backs, or basking along the trunk to soak up warmth in the early morning hours.

Sitting against a background of evergreen trees, you would never know the outside temperature was sub-zero, except for this gray squirrel’s curled up posture and hyper-fluffed tail.

Fluffing out his fur and tail makes this little red squirrel look pretty chunky, but that is the way it can maximize its insulation in extreme cold. This little guy was actively shivering, as his forearm paws and tail vibrated with each breath.

For those animals (and humans) that can afford to do so, the best solution to surviving cold temperature extremes is to fire up the metabolic furnace.  No one enjoys standing out in the cold shivering intensely, but that and the physical exertion of exercise are the first line of defense in staying warm.  The trick is to preserve the heat inside the body by improving insulation with a nice layer of subdermal fat, a thick fur coat, and minimizing the surface area exposed to the air.

Another strategy for staying warm in mammals (but rarely in birds) is metabolizing brown fat, which is a special kind of adipose tissue located along the vertebral column, heart, and kidneys. Brown fat is highly vascularized and contains lots of heat producing mitochondrial organelles. The heat produced by a process of non-shivering thermogenesis in the central core of the body can then be circulated to other parts of the body.

Newborn and hibernating mammals utilize brown fat thermogenesis to warm up. Other small mammals use the heat produced by brown fat as a supplement to shivering thermogenesis. Diagram from McMillan Higher Ed publications.

So, bundle up and think warm thoughts — the days are getting longer and the sun is getting higher in the sky each day. Winter won’t last too much longer.

Looking back at 2021

Another year of Covid prohibitions on activities, but not such a bad year for seeing new places and new species. The highlights month by month look like this:

January: a trip to Sax-Zim bog in north central Minnesota, and an exciting afternoon shooting Great Gray Owls diving for mice in the snow.

Great Gray Owls blend in so well with the tree stumps they are sitting on, you might drive right by them on the forest roads in north central MN.

February: Yes, the most memorable highlight of February was winning the vaccine lottery and getting my first vaccine shot — after waiting in line for almost 2 hours with 1000 other anxious people.

March: hiking with adventurous grandkids at frozen (well, mostly frozen) Minnehaha Falls in downtown Minneapolis. Caves behind the falls are fun to explore when you’re steady on your feet.

Also in March — Great Horned Owlets are growing up fast and almost ready to leave their nest hole to perch on tree branches.

April: the great Road Trip of April and May netted us over 160 species (many new and never seen before), after visiting over 40 parks and driving over 6800 miles). Some of my favorites were the ever-amazing hummingbirds, like this composite of a Broad-billed Hummer coming into a feeder in southeastern Arizona.

We visited many beautiful places on our long April-May adventure, but we keep coming back to this place deep in the Chiricahua mountains of southeastern Arizona — Cave Creek ranch, where exotic birds and gorgeous scenery captivate.

May: On the way back to Minnesota in May, we stopped at Antelope Island in Salt Lake City, where grazing bison and antelope are abundant and the mountain landscapes behind the city are spectacular.

June: another Road Trip — this time with the grandkids camping across the western U.S. on our way to the mountain cabin near Lake Tahoe.

My favorite bird highlight from June was this Western Tanager male in all his bright breeding finery — the jewel of the Sierra.

July: with almost all the grandkids and missing one son-in-law (who had to work), the rest of us gathered for the 4th of July at the cabin near Lake Tahoe.

August: surreal landscapes in the back country of Desolation Valley in the CA Sierras on our backpacking trip, as the Caldor Fire literally burst upon us one morning.

September: fall migration began with the arrival of a dozen or more warbler species, along with assorted vireos, flycatchers, finches, blackbirds, etc. Mr. Magnolia Warbler was not quite as beautiful as he was in the Spring, but nevertheless, is a handsome bird.

October: a trip to Alabama to see the birds of Mobile Bay and Dauphin Island and its pristine white quartz sand.

Fall color was unusually bright and long-lasting in October this year. A pleasant surprise after a somewhat hot, dry summer.

November: foxes and turkeys passed through the backyard frequently, but there was little snowfall this month. Very unusual.

December: at last it looks like winter, but a warm-ish spell right before Christmas melted all this lovely stuff.

The truth about Santa’s reindeer

Some misconceptions to the usual assumptions of what powers Santa’s sleigh need to be addressed:

Santa’s reindeer are all female (click on the link to read the article)

Fact #1: those antlered reindeer pulling Santa’s sleigh are all females. How do we know this? Fact #2: both male and female reindeer have antlers — although the males’ antlers are usually much bigger. And Fact #3: male reindeer shed their antlers in late fall, so that by December, they are antler-less. Ergo — the powerful ones pulling the sleigh are the girls.

Reindeer (i.e., caribou) at the Minnesota Zoo in the summer. It’s easy to pick out the male because of his size: bigger body and much larger antlers than the four females grazing with him.

And this leads inquiring minds to wonder — a) why do female reindeer have antlers at all? (other female members of the deer family do not), and b) why do they have them all winter, only to drop them after their calves are born in the spring?

It would seem to be a great advantage for females to keep those antlers over the winter as they gestate next year’s offspring. They need energy for reproduction, and the food is buried under the snow. Antlers would certainly be useful for removing snow so the reindeer can get to the forage. Larger-bodied males can withstand periods of low food availability better, and need to start re-growing antlers immediately in the spring so they will be ready to compete for mates in the summer and fall.

Now — about that red-nosed leader of Santa’s team. Rudolph, created by Robert May in 1939, is also pictured with antlers, so we must assume he is a she, as well as the rest of the team. But why make such a big deal about the red nose? Is there such a thing as a red-nosed reindeer?

Yes, indeed, reindeer have red-ish noses, and for a good reason, as explained in an article from Smithsonian magazine in 2012.

The rosy pink nose of reindeer in the winter is due to high blood flow to the nasal area, which warms the nasal cavity, and thus the warms up the frigid air reindeer breathe in before it goes to the lungs. In addition, flushing the nasal cavity and head with blood from the central core of the reindeer’s body helps keep the animal’s brain warm. I suspect if we did the same thing when eating a slushy drink (like Jamba juice), we wouldn’t get an ice-cream headache.

So, let your kids and grandkids in on the real power behind Santa’s trip around the world on Christmas eve — female reindeer!

the good morning fox

The backyard has been really quiet the past couple of weeks, as colder weather sets in and the daylight hours get shorter and shorter. Some days the birds don’t start visiting the feeders until after 9 a.m. Even the squirrels are quiescent, having long ago dug holes all over the backyard to store their walnuts.

But the red foxes make regular treks through the backyard early in the morning, looking for whatever they can find — which apparently isn’t much because they don’t stay more than a minute and then move on to the wetland area in back of the backyard.

There is rarely a pause in the action, unless they need a good scratching.

Nose to the ground, hoping to catch the scent of an unlucky squirrel, trotting through my backyard on their way to someone else’s. It’s just barely daylight, so the photos through the porch windows are not the greatest.

Success in the hunt! A few years ago, this was the scene that greeted me at breakfast early one morning.

Looking toward the light

Photographers usually try to shoot with the sun behind them, but occasionally the scene may be more dramatic when shooting directly into the light. That was the case the other day when I was walking in Reservoir Woods and came upon a field of Indian grass and Showy Goldenod seedheads that shimmered in the backlit afternoon light.

Here, the sun is just off to the right, and the golden seedheads stand out dramatically from the rest of the vegetation.

Here, I’m looking directly into the sun, which throws a glare of bright light into the center of the image.

Look at the difference in this scene when I turn around and shoot with the sun directly behind me. The seedheads of the grasses and goldenrod disappear into a monotonous expanse of yellow stems.

There’s an important lesson here — don’t always follow the rules because you might miss some of the drama in nature.