A Murder of Crows

In my downtown neighborhood of Sherman Hill, and in many areas around Des Moines, an annual phenomenon is in full swing; the roosting of the crows.

As dusk falls across the city, the sky begins to fill with streaks of black.  It starts off with just one or two birds, suddenly appearing as if by magic.  As time passes and the light begins to dim, you will notice more and more large black birds winging across the evening sky, and alighting on two or three trees in your neighborhood.

For the hour or so before dark, the crows will emit a cacophony of sound as they fly from tree to tree, squabbling amongst themselves and calling out to their neighbors as more birds join the flock.  By the time the sun is sinking below the horizon, their noise can drown out all other neighborhood sounds.  But at nightfall, as if by an unspoken signal, they settle down and gradually fall silent.

During the spring and summer months, breeding crows spread out across the countryside to raise their young.  They are fairly territorial during the breeding season, and will defend against all comers beyond their family group.  As the fledgling chicks leave the nest, and summer deepens into fall, the birds start to move in towards a centralized sleeping location, known as a roost.

There are several theories as to why crows like to roost in such large numbers during the colder months.  The most popular is the concept of "safety in numbers".  Owls love to prey on sleeping crows.  By roosting in large flocks, full of watchful eyes, they have a better chance of seeing their predators and avoiding their deadly talons.

Another idea is that there are some trees that are simply ideal for sleeping; five star bird hotels, if you will.  The crows don't mind sharing those trees with other birds if it means that they get a bed in the best tree in town.

Because crows are highly intelligent and good communicators, another theory has them sharing information at the nightly roost.  For example, a bird that has had a hard time finding food for a few days might pick out another bird that seems to be in good health, and follow them to their food sources for the next several days.

Roosts of crows are a natural and global phenomenon.  The largest recorded roost to date , located in Fort Cobb, Oklahoma, held over two million crows.  Take some time to observe and appreciate these large congregations of our wild neighbors.  Send in your photos and your observations!

Fair Weather Friends

A lot of the excitement goes out of my life at the end of each autumn.  You see, this is the time of year when the chipmunks retire to their winter dens.



Photo compliments of The Animal Diversity Web (online). Accessed November 17, 2011 at http://animaldiversity.org.

 During the warmer months of the year, there is nothing that gets me more worked up than the squeak and shuffle of a chipmunk navigating the edges of our yard.  They always announce that they are about to run the gauntlet from the oak tree in the front yard to the retaining wall at the back of the garden.  This noise could be interpreted as something akin to taking a deep breath before diving into a cold lake.  With a piercing "CHIP", they begin their frantic scurry along the fenceline, behind the rosebuses, and into the garden, with me hot on their heels.

Personally, I think they love the thrill of the chase.  I am not particularly dangerous to them, as I can never catch the quick little rodents.  They are just using me to add a little rush of adreneline to their days.

I will not meet the little striped rascals again until next spring.  Chipmunks are not true hibernators, but they do enter a period of winter torpor.  They stay in their dens, snug and protected from the elements, throughout the harsh winter months.  They sleep most of the time, only waking occasionally to munch on stored nuts and seeds.

Their relatives, the groundhogs (also known as woodchucks),  are true hibernators.  Woodchucks dig special wintering dens, well below the frostline, where temperatures are relatively warm and stable.  They eat frantically throughout late summer and fall, building up a layer of body fat that will sustain them throughout the upcoming winter months.  When the time comes, sometime in late fall, they snuggle into their dens and fall into a state of inactivity, characterized by lowered body temperatures, dramatically slowed breathing, and decreased metabolic activity.  They will remain "asleep" until the end of winter (which, of course, they can predict)!

Another group of amazing hibernators are the frogs, such as this tree frog.

The tree frog will overwinter in shallow mud, under bark, or hidden beneath rocks or logs.  Most of their bodily fluids will freeze solid over the cold season.  However, a special chemical produced by their livers, similar to antifreeze, keeps their internal organs from freezing and allows the frog to "thaw out" in the spring. 

So, along with the birds that fly south during our winter months, we also need to say a temporary goodbye to the animals that use techniques like hibernation and winter torpor to survive the cold.  We'll see them again in the spring.  In the meantime, I am glad I have a thick fur coat to keep me warm.  I can't wait for another season of playing in the snow!

What other Iowan animals seem to "disappear" during the winter?  Many of them are still out, enjoying the last bit of warm weather during this extended autumn.  Get out to our parks and try to get a last glimpse of chipmunks, groundhogs, skunks, bats, ground squirrels, and other animals that wait out winter in the security of their warm dens.  Send in your photos with your comments!

Overhead and Underfoot

One of my favorite things to do in the fall is to shuffle and snuffle through the great piles of leaves that have fallen to the ground.  The rich aroma of drying and decaying leaves brings to mind various autumnal associations; blustery chill winds, swirling flocks of migratory birds, the crackling of a cozy fall campfire complete with hot dogs... mmm, hot dogs!  But, I digress.

While crunching through the piles of leaves on the ground can be fun, it is the leaves that remain on the trees that offer the greatest entertainment value.  While many trees have already dropped their leaves in preparation for the cold winter ahead, our majestic native oaks are holding on to theirs, and displaying an amazing array of rich saffrons, bronzes, umbers, and mahoganies.

Few people realize that these beautiful fall colors are actually the true colors of the leaves.  The colors of fall are always present in the leaf, from the moment it erupts from its bud. 

The green color comes from chlorophyll, which the tree uses to convert solar energy into sugars to feed itself through the process known as photosynthesis.  The vibrant green color of chlorophyll covers the other pigments in the leaf throughout the summer months. 

However, as winter approaches and the days grow shorter, the tree stops the process of photosynthesis as it prepares to enters dormancy for the season.  At this time, the tree stops producing chlorophyll, and the green pigment fades away, revealing the true colors of the leaves beneath! 

Our deciduous trees, those that lose their leaves in the fall, actually do so as a means of water conservation.  Leaves are a liability throughout the dry, cold winter months.  Trees take up water through their roots, and lose water through their leaves.  In the winter, when the ground is frozen, there is no water to take up.  The trees drop their leaves in an effort to keep from withering up over the long winter months.

Just like the rest of us, our trees have to prepare themselves for the cold season ahead.  You should do the same!  Get out your winter outerwear, dust off your boots, and take an excursion out into the late autumnal woods to revel in the beauty of the oak trees.  Take some photos and send them in to the blog, along with your comments.

Winter is just around the corner, and it brings with it many new ways in which we can PLAY OUTSIDE!