Push and Pull

Push and Pull

(This post was actually finished two weeks ago, but due to a failing home computer I didn’t save it like I should and I had to reconstruct the whole thing.  Apologies for missing about a month-and-a-half.)

The study of geography talks about the reasons that people immigrate and emigrate (which by the way means to come into another country or leave one’s home country, respectively), the push and pull factors.  These include:

  • famine
  • war (unfortunately all too present right now)
  • debt
  • opportunity
  • running from the past

Animals have a more limited scope when they migrate.  And the strict definition for migrate includes the idea of a return.  Animals only permanently move out if habitat is destroyed or they are extirpated.

What you probably picture when you think of "migration."  (Courtesy Wikimedia Commons)

What you probably picture when you think of “migration.” (Courtesy Wikimedia Commons)

Here in Michigan we think of migration in primarily terms of north and south–Canada geese, mallard ducks, songbirds, sandhill cranes, and monarchs all head for sunnier climes beginning in September.  But migration can happen in an east to west (or vice versa) cycle, up and down mountains, and even vertical movement through the water column.

Photo courtesy Nature Next Door

Photo courtesy Nature Next Door

All kinds of animals migrate (heck, even mold migrates!) from zooplankton to blue whales.

 

Migration for them is an “adaptive response to seasonal or geographic variation of resources.”  Or sometimes to breed.  The daylight length, temperature, or food sources have changed and so animals move on.

Those triggers–light, hormones, water currents–all give the signal to “pack up and head out.”  Cooler temperatures signal birds to migrate, for instance.

So, how do they do it?  Migrate, I mean.  Animals use topography, polarized light patterns bouncing off of airborne particles (which happens even on cloudy days), the stars, and olfactory and magnetic cues.  Rivers and coastlines are particularly helpful.  The most southern point in Canada (well, nearby Pelee Island is officially the southernmost point) is a sandy peninsula known as Point Pelee.  This helps guide birds across Lake Erie.  Why wouldn’t it?  It’s a giant directional signal pointing south.

How can you not know what direction to go?

How can you not know what direction to go? Photo courtesy Brian Kirchner

 

 

 

Some animals forage along the way, while others have gorged themselves and built up fat stores (hyperphagia) much like those who stay and hibernate.

Southeast Michigan sees the beginning of migration in August and continues even to this present point as I witnessed a flock of Canada geese pass over me this morning.  The little brown bats we observe wheeling the evening summer sky move from their tree roosts to caves for the winter.  The trout and salmon are migrating for breeding purposes (though their numbers are limited in SE Michigan).  Hummingbirds, sandhill cranes, and all kinds of warblers have exited the confines of the state. Out west, the elk migrate, and in northern Michigan there is a herd or four, but I don’t know that they migrate.

Before finishing this article let me include some random migration facts:

  • Humpback whales complete the longest mammal migration of up to 8,500 km each way.
  • Monarch butterflies, of course, have the longest insect migration from Canada and the northern US to California and Mexico in the fall–up to 4,750 km.

    Photo courtesy Tamya Hall

    Photo courtesy Tamya Hall

  • Rattlesnakes(!) in Alberta, Canada migrate to find dens for hibernation just slightly south of their summer grounds

As annoying as the Canada goose has become, it’s still thrilling to hear the feathery thump when they fly in their characteristic V-shaped flocks closer to the earth on the way to wherever they stay.  Occasionally, the mallards in smaller groups beat their whistling wings to find food further south.  The great blue herons will stick around, surprisingly, as long as open water exists.

So what migrates from your neighborhood?  Or perhaps you live in a winter destination?  What “new” species are just showing up?  Get outside and look around.

 

 

Tree Rat, Acrobat

Some hunters might say that the white-tailed deer is autumn’s animal icon. Others, perhaps the Canada goose, maybe the bears that begin to gorge for a long winter’s nap, but I say the ubiquitous tree squirrel is the keystone of autumn.
Who else scurries around creating middens or caches of pine cones (red squirrel) or buries nuts of all kinds (gray squirrel, fox squirrel) around your yard, your neighbor’s yard, and someone else’s two blocks over?
The tree squirrel has to be one of those animals that are so common they become invisible—except when we’re swerving to avoid crushing them under our car tires. They are found all over the world though not in Australia, Madagascar, and Antarctica.
These rodents have earned the ire of people because of their mildly destructive habits in tearing up gardens, stripping tree bark, and raiding bird feeders, and in my case, chewing up my bike seat after a red squirrel was trapped in my shed for two days.
They’ve earned many names here in North America: tree rat, puck-o’-the-pines, fairy diddle, and bannertail among others. The Ojibwa people (who resided (still do actually) in Michigan called them kitchi-adjidamo meaning big squirrel. The genus Sciurus comes from Greek and it means shadow tail.
Here in the U.S. the biggest is the fox squirrel and the smallest is the southern flying squirrel. While Pakistan holds the record for the largest existing species: the woolly flying squirrel.
Michigan is home to three tree squirrel species, the fox Sciuris niger (photo courtesy of wikimedia commons), Sciurus_niger_(on_fence)the gray (which can also have black fur) S. carolinensis, 6576b69f35c2d7137efd49accc70-grandeand the smallest of the three, the red, Tamiasciuris hudsonicus.red-squirrel-2 In addition, we have the southern flying squirrel, and farther north, the northern flying squirrel, fortuitously enough.
Tree squirrels can see in color and have a very strong sense of smell, which scientists previously thought that meant they could locate sources of cached food, but that seems to not be the case.
There is more than one coloring pattern for all North American species which confused the early naturalists.
All tree squirrels (at least in North America) share the following characteristics:
• They have whiskers (referred to as vibrissae) used to help them in dark nests and tree cavities
• Their front feet have four digits and the rear five
• While observing squirrels climbing, pay attention to their rear paws; they can turn their ankles a cringe-inducing 180° to allow for hanging, eating, and speedy vertical descent from a tree.
• The characteristic bushy tail serves as shade, protection from the elements, balance, and communication
• Different squirrels have different diets, but all overlap somewhere in the following: nuts, acorns, pine cones, insects, buds, berries, fungi, nestling birds, bird eggs, and corn
Tree squirrels have an aesthetic appeal, but their newborns do not. Blind, hairless, and with ear flaps closed, they are rather ugly (yes, it’s a judgment) until the fur comes in. They are born in litters of one to five with two to four being the average. The gestation period is 44 days for gray squirrels and 44-45 for foxes.
Squirrel romance is limited to the brief conjugal encounter as there is no bonding between parents.
Tree squirrels tend to live about 4-5 years, but cars (as many of us can testify) tend to shorten that length considerably. Disease and starvation beat out automobiles as vehicles (heh!) for death. Severe cold weather is handy at culling, too.

Random squirrel facts
• They can run 16.7 mph on flat ground
• They can swim, dog-paddle style, for short distances
• They are “seed predators” (cue scary music).
• They don’t hibernate, if you hadn’t noticed
• They are diurnal. When was the last time you saw a squirrel traipsing around at night?

I have alternately loved and hated squirrels. I used to hand feed a red squirrel at my maternal grandparent’s island home in Canada as a child. I also remember being about 14 years old and sneaking up behind a squirrel next to a silver maple in the front yard of my childhood home and pulling its tail.
I also remember a few times of cartoonishly chasing squirrels off of my backyard bird feeder before I invested in a baffle.
So, go out in the brisk weather, observe these familiar rodents. Pay attention to the arched pattern the body and tail of the fox squirrel as it hops across your lawn. Can you spot the red squirrel scurry atop your power lines to a tree? Are there more black varieties of gray squirrels than gray around your home?
Go out, come back and report.

I used a couple of good resources for this post. North American Tree Squirrels by Michael A. Steele and John L. Koprowski wrote a more “sciencey” book, but it is still readable by the educated reader. Squirrels: A Wildlife Handbook by Kim Long is lighter on the science and covers much of the folklore about squirrels. Together, you would probably have all the knowledge you need about squirrels aside from your own observations.

To the wonder

IMG_1072I can’t make this month’s challenge any easier: Go outside and explore!
We’re on the cusp of a new season–the Autumnal Equinox occurs in the northern hemisphere on Sunday–it’s the perfect time to see the blurring of seasons.
Goldenrod is probably at peak blooming right now (honeybees have only a few weeks left to gather pollen and nectar), maples are hiking up their chlorophyllic pants, nuts are dropping making a mess of sidewalks, you get the idea.
My neighbor’s birch tree has about 20% of its foliage turned yellow. Apples are in season (finally!). I was surprised by mosquitoes today.
What does this fading summer and blossoming autumn look like in your neighborhood? Go out, look around, and report. Maybe I’ll even send a prize to the first person who reports something. Give me at least three sentences to be considered, however.

Challenge #4 Answered

Post-Halloween displayThe grey days of November are here in Michigan.  It’s been dry and cold for the most part, but we’re going way above average for a couple of days starting in December.  I was walking home from work about two weeks ago and smelled smoke, the sunlight was pale and cold, and that’s when I realized that that is the essence of November: cold, but with the promise of comfort and warmth from a fire somewhere.  Most of the birds around here now are the hardy year-round residents.  Insects can still be found, but only in ones and twos, and then only on days when the temperature rises above 50 degrees.  Squirrels are still active and deer can occasionally be spotted wandering the mean suburban streets, but late fall means a general slowdown of biodiversity.  Most of the trees are naked now, and most plants that are still green are invasive.

So aside from my own thoughts of quaint New England villages framed by flaming colors of hardwoods, November is quiet, introspective, and waiting patiently for the cleansing blanket of snow that might come during Advent or Christmas time.  November is seeing the last flocks of mallards and Canada geese flutter away.  November is crisp silence.

Challenge #4

Autumn is past mid-point here in the northern hemisphere and most of the color show is over in the Great Lakes; the grey days of November will be here to stay soon.  So, I’m going to shift the focus for this month instead of trying to identify species, though you should work to keep doing that, instead pay attention to the train of your thoughts when outside.  What does the crisp air make you think of or long for?  What feelings dominate you this time of year?  Go ahead and post any exciting species sightings, but also record thoughts and feelings that are native to you in November.  I trust you can think of more than turkey, pilgrims, and football.

Challenge #3: Trees

The past two challenges have involved things that moved from yard to yard; this month’s challenge is about less ambulatory organisms.  Not ents, but trees; it is autumn, after all.

So, I’ll make this even easier, you won’t have to leave your yard.  Simply identify the trees in your yard.  You can even throw in shrubs, but not bushes, mind you.

Take time to absorb the color changes happening now–at least for us folks in the northern US.  ID your tree(s) down to the species, but if you have none in your yard, post about your neighbor’s trees or those in your ‘hood.