Today is two months after the winter solstice (Dec 21), and we now have two more hours of daylight each day (almost 11 hours). More importantly, the sun rises each day 13 degrees higher than it did on the winter solstice (35 vs 22 degrees above the horizon), and it is now more than half way to its maximum altitude in our summer sky on June 21 (68 degrees).
What does this mean for us winter-weary Minnesotans — spring is ever near! Cardinals and Chickadees are singing up a storm on sunny mornings when the radiant heat of the sun can actually be felt through the chilly (20 F) air. The polar vortex is history, and it’s time to get out and enjoy the end of winter, — like taking a morning walk along the Sucker Lake creek.
We have been in the grip of a prolonged vortex of cold air from our northern neighbors since February 4 with daytime highs in the negative digits (F) and nighttime lows dipping well below -10 F (e.g. last night was -21 F). Just for something to inspire me mentally (?), I added up the last 10 nights of low temperatures and came up with a grand total sum of -95 degrees. Now that’s arctic! Needless to say it’s difficult for my fingers to work camera buttons at these temperatures, let alone get outdoors for a walk in the backyard.
But, in the spirit of Valentine’s Day and to commemorate a time when I was braver about venturing out in -15F weather, here are a few photos of the Trumpeter Swans on the Mississippi River at Monticello, MN, engaging in courtship displays to cement their pair bond — love is in the air for these swans, most of which mate for life.
Thinking of warmer days ahead, I wish you a Happy Valentine’s Day, 2021.
It wouldn’t be winter in Minnesota without a week or two of sub-zero (in F degrees) weather (-2F this morning and that’s -19 degrees C). And the little birds have been hitting the feeders pretty hard lately, especially the peanuts.
Now here’s the problem with being a small bird trying to survive in this winter climate. Heat will be lost from a body surface when the body is warmer than the environment, and in the case of the chickadee, whose body temperature is normally about 107 F, that is a 109 degree difference between its internal core and the air temperature hitting its feathers this morning.
In addition to this huge thermal gradient for heat loss, small birds like Chickadees have a very high ratio of surface area to their heat-producing body volume — thus accelerating the rate of heat loss. [If you’re interested in why this is, we can talk about the mathematical basis of surface to volume ratios in the comments…]
Chickadees are metabolic marvels, being able to harvest enough energy from their foraging efforts all day to last them overnight and part way into the next morning, before they can visit their stash of seeds or a bird feeder. BUT…they are economical with their overnight energy expenditures (because you never know what the next morning’s weather will be like), and they make their fat reserves last by lowering their body temperature as much as 20 degrees F (from daytime highs of 107 F to night-time lows of 86 F).*
Hypothermia makes it possible for Black-capped Chickadees and most other titmice members of the Paridae family to survive winter cold in northern latitudes. Not all birds can or do utilize this strategy. Some species, like Common Redpolls, eat a more fat-rich diet to have a larger overnight energy reserve. Some species, like the Common Bushtits that weigh half as much as a Chickadee, share body heat with each other by roosting together communally, packed tightly side by side on a branch. And some species, like Eastern Bluebirds do a little of both the Chickadee and the Bushtit strategy to make ends meet energetically.
Multiple birds in the same box together would be ideal for conserving some body heat on a cold day, in the same way we use the shelters at the bus stop and (used to) stand close to friends and family to retain heat.
Groups of six to eight Eastern Bluebirds in Indiana were observed to roost together in a nest box overnight, forming a circle with their heads toward the center of the box and pointed downward below their bodies so the heat from their exhaled breaths was directed toward the other birds.** It’s possible they might be using this heat conservation strategy during the daytime as well here in Minnesota, when multiple birds enter the same box.
In addition, Eastern Bluebirds forage in small flocks during the winter, using the strategy of more eyes to find food. And when they take a break from foraging intensively, they often huddle tightly together on a branch close to the trunk of a large tree that provides some protection from heat loss from the wind.
It must be tough to be an Eastern Bluebird that depends on a fruit and insect diet to find enough to sustain itself overnight in Minnesota’s subzero climate. What do they do if they can’t find sufficient food to last them overnight? Bluebirds in Indiana were lethargic and immobile when researchers opened the nest box after a cold night; it’s possible they might also be lowering their body temperatures overnight to conserve energy like the Chickadees do. But there are no published data on this — at least that I can find.
*The data on hypothermia in Chickadees overnight was part of my Ph.D. thesis at Cornell University in 1973. **The data on communal roosts of Eastern Bluebirds in Indiana was published by Frazier and Nolan in 1959 in Bird Banding.
As in blue sky (for a change) and Bluebirds (that shouldn’t be here at this time of year) on a sunny day with an unseasonably high temperature hovering near freezing (30 F). For a change of pace I went walking on the local golf course, curious to see whether I could find the reputed Mountain Bluebird that has taken up residence here along with aforementioned Eastern Bluebirds.
But I found only the eastern cousins, near two Bluebird boxes, which the birds were sitting on and inside of during the middle of the day.
Although Eastern Bluebirds breed here in the summer, they usually retreat south in the winter to places that have less snow cover and milder temperatures where they feed on a wide variety of shrub and tree berries and mealworms provided by friendly birdwatchers. What a treat to see their cheerful bright blue and rusty brown colors on a landscape that is mostly white, gray, and brown this time of year.
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.
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.
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.
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]
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.
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.
Preparations for the Christmas holiday delayed my final post of the November-December journey to the west coast and back. But in moving photos from one computer to another, I rediscovered our final wildlife encounter of the trip back to Minnesota at Bosque del Apache in south-central New Mexico. From there it was an arduous two-day long drive back home, so this was a final chance to get out and enjoy the spectacular wildlife and scenery.
Tall cottonwood trees line the banks of the river channels, providing cover for a variety of songbirds that migrate through this area. It is this riparian forest that gives the area its name, “forest of the Apaches”, a site where the local Apache Indians gathered to hunt the wildlife during peak times of migration. However, the area was initially settled more than 700 years ago by Pueblo-building Piro Indians that farmed the fertile, flooded regions around the Rio Grande. They were eventually driven out of the area by Apache raiding parties and Spanish explorers/colonists.
We have seen many more Sandhill Cranes here in mid-January, so perhaps the bulk of the migrants from northern-most parts of North America have not arrived yet, or perhaps some cranes that might stop here prefer to overwinter further south in Mexico. (Click here to see a video of the cranes coming in to roost on the river at Bosque del Apache in January.)
The Cranes probably won’t stop here on their way north again in the spring, but will congregate in huge numbers in March and April in Grand Island, Nebraska on the Platte River — and that is a sight to behold!
Collective nouns for groups of animals are sometimes descriptive (herd of deer, flock of birds, colony of bats, pack of wolves, or school of fish), or sometimes pertinent to particular behaviors of animals, like a crash of rhinos, swarm of bees, caravan of camels, tower of giraffes, or pandemonium of parrots. But often the terms for a particular animal group are just fanciful, like dazzle of zebra, implausibility of gnus, charm of hummingbirds, or a siege of herons. It’s important, you know, to recognize these groups of wildlife by their proper title.
Walking around the sloughs at Don Edwards SF Bay National wildlife refuge the other day, I came across the following scene:
Like so many other collective nouns for animals, the term for a bunch of Kildeer seems to have no relationship to the bird itself — they are called a “season” of Kildeer. Which makes me wonder if we only see an assemblage (congregation) of this many Kildeer at certain times (season) of the year.
You might wonder how this practice of naming groups of animals got started? It turns out that these collective nouns are part of a hunting language that included terms for humans as well as animals, developed in England and France in the 1400s. They were compiled into The Book of St. Albans, published in 1486, and apparently the terms have stuck with us today, especially those describing groups of various bird and mammal species.
We were 3 miles from our destination at Cave Creek Ranch in the Chiricahua Mountains of extreme southeastern Arizona when a rear tire on our Highlander went flat (note to self: avoid driving on gravel roads!). And although this was a major inconvenience for my husband who had to drive 60 miles to the nearest Walmart to get a new tire, it meant we could stay at the ranch an extra day.
The Chiricahua Mountains rise 6,000 feet above the desert floor that surrounds them, making them an “island in a sea of desert”. A variety of life zones occur along the gradient from hot dry, desert to cool pine forest at peak elevation, and this means these montane islands are a hot spot of biodiversity. And like animals on oceanic islands, Sky Island animals are restricted to their mountain environment, and may become locally endemic, not mixing or interbreeding with the rest of their parent species.
Such”sky islands” occur in a number of locations in North America, but this one in the Chiricahuas is particularly interesting because it attracts more southern-distributed Mexican and Central American species like Trogons, Mexican Jays, coatis (raccoon relatives), Jaguars, Mexican wolves, javelinas, and some endemic races of white-tailed deer and wild turkeys.
Quite a diverse place, those Sky Islands of Arizona!