Outside My Window

Outside my office window in the afternoon, I see flocks of crows, robins and starlings heading for the roost.  Lately it occurred to me that I’m able to identify them at a glance, not by looking at the individual birds but by looking at the shape of the flock.  This skill was particularly useful at the robin roost on January 6 because it was too dark to see individual birds.  

As you can see in the pictures above, the flock shapes can be different even in birds of the same size.  From left to right are four flocks:  American robins, European starlings, double-crested cormorants and tundra swans.  (First two photos are by Tom Pawlesh, last two by Chuck Tague.)

Here are some flock shapes I can think of: 

• American robins: loose flock, widely spaced.  Each bird maintains the same relative position within the flock.
• Starlings and pigeons: tight flock, synchronicity. Every bird makes the same move at the same time.
• Double-crested cormorants:  J-shaped flock or a long line.  The flock looks scraggly.
• Geese and swans:  V, J or crescent-shaped flock.
• American crows:  A loose flock in which each bird has his own idea about where he wants to be.  Individuals show considerable positional movement within the flock.  The birds look like black rags flapping in the sky.
• Blue jays:  A loose flock so widely spaced that they sometimes look like they’re not traveling together.  Individuals maintain the same relative position within the flock.
• Cedar waxwings and American goldfinches:   The flock moves in unison but individual birds change position within the flock, mostly by moving up or down.  American goldfinches say “potato chip” as they fly.
• Small finches, common redpolls:  Fly fast in relatively tight flocks.  The flock moves in unison.  Individuals zip forward or slow down but maintain positional integrity. 
• Cowbirds: have a cool hopscotch pattern as they sweep across a field searching for food.  (comment from Chuck Tague)
• Brown pelicans: The flock travels in a long line, skimming the surface of the ocean.  They will even skim the surface of high rise buildings at the beach.  Each bird synchronizes wing movement with the flock:  first bird flaps downward, then second bird, then third, then fourth…
• On water American coots huddle close together in an extremely dense flock in the presence of a bald eagle.
• Turkey vultures:  Soaring birds.  Each bird goes his own way but they stay together.  They hate to flap.
• Cranes: Soaring birds who travel in flocks, sometimes in a loose V.
• Hawks and falcons:  no flock at all.

An animal-lover friend of mine began to feed the birds and was shocked when a coopers hawk killed a mourning dove at her feeder.  She does not eat meat and wanted to know if she could train the coopers not to eat meat either.  “If I put out more corn, will he eat the corn and not the doves?”

“No,” I said, “he will not eat corn.  He’s a carnivore.  That’s just how it is.”

Because humans are omnivores and we grow our own food, we find it hard to imagine the lives of creatures who must hunt to live.  If a coopers hawk is not an efficient hunter, if it does not kill birds, it will die.  It would be cruel to the hawk if it could not hunt. 

But what about the prey species?  Is it cruel to them that they are hunted? 

There is a beautiful poem by James Dickey in which he describes the heaven where wild animals go.  Called The Heaven of Animals he describes the predators in their heaven crouched on the limbs of trees and writes,

“And those that are hunted
Know this as their life,
Their reward: to walk

Under such trees in full knowledge
Of what is in glory above them,
And to feel no fear,
But acceptance, compliance.”

The universe is structured so that everything is eaten by something - in the grave, if not before. What an amazing cycle.

That’s just how it is.

As I write there’s a tremendous racket going on in my neighbor’s back yard. The blue jays are screaming and jumping around in the spruces, focused on a spot I cannot see.  Starlings are loafing nearby to see what happens.  Twelve nervous mourning doves are sitting in the black locust.  The juncoes have joined the fray in the spruces, even though they’re normally wary of jays. 

Everyone’s excited about a predator in the spruces.  I can only guess it’s an eastern screech-owl.

Blue jays are an excellent alarm system.  I often use their calls to find birds of prey.  Small birds are saved the surprise of being eaten when they hear the jays’ alarms.  Even though the rest of us benefit from them, the jays just view it as doing their part to make the world safe for blue jays.

At rush hour last night, a river of crows flew over Fifth Avenue and perched in the trees on Wilkins.  That event and last week’s robin roost prompted me to think about flocking behavior. 

We’ve all noticed that birds flock in winter.  It turns out that flocking is usually a trait of social species, such as crows and parrots, and species whose food sources are abundant: omnivores like gulls and starlings, seed-eaters like blackbirds and finches.  But why to they do it?

The first reason is defense.  It’s harder to be caught unawares if you’re in a flock with many watchers and it’s statistically quite safe.  At the robin roost we heard a pair of great-horned owls but each owl will catch only one bird per night, leaving an individual robin with a 0.002% chance of becoming an owl meal.

Another flock advantage are the many eyes searching for food.  If the food source is abundant - a seed field or a landfill - everyone gets a meal.  Obviously, flocking doesn’t work for birds like red-tailed hawks who catch their prey by stealth. 

Social species enjoy flocks.  Crows get smarter by being with each other.  As Candace Savage said in Crows: Encounters with the Wise Guys:  “Nothing is more intellectually challenging than living in a social group, surrounded by a bunch of other animals that are sharpening their wits on you.” 

The most spectacular flocks are made up of starlings who wheel in unison without an apparent leader.  Tom Pawlesh took this photo of a spectacular “cloud” of starlings.  Not all birds fly in a tight formation like this.  When it comes to flocking, starlings are the champs.

I mentioned this phenomenon on PABIRDS and got a huge response so I decided to go into more detail here.

On Sunday at Moraine State Park (Fine Weather For Ducks) I heard a frog-like sound coming from the area where the ducks were swimming.  Using Cornell Lab of Ornithology’s website I figured out the sound came from the hooded mergansers.  The male is pictured at left, the female at right, by Chuck Tague.

According to Cornell Lab, hooded mergansers are silent except in courtship when the male gives a deep rolling frog-like sound, recorded here at the end of the clip. 

Amy Taracido says their voice sounds like “merg merrrrrrrrg” - a perfect description and one that makes me laugh when I say it.

Besides the sheer amusement of hearing a bird make this noise, it’s curious that this is considered a courtship sound.  We generally assume birds don’t court in the winter, so from our perspective the hooded mergansers cannot possibly be courting on December 9th.  But why not?  Why does courtship have to be confined to spring? 

The flock was large and about 50/50 males and females.  On migration southward, the hooded mergs might be in “dating” mode, especially the young ducks who haven’t bred yet.  Flocks would be the perfect place to meet the opposite sex and decide on a mate.  Mergansers might even need some get-acquainted time before they make a choice.

So I guess Lake Arthur is The Bar Scene for ducks.

I am not a morning person, but I want to be, so I get up an hour before I need to, drink a mug of coffee, and I wait to wake up. 

Sometimes - even in cold weather - I sit on the front porch and watch the birds go by.  Their rush hour happens overhead.

In winter the first to fly over are the crows, northeast to southwest.  This morning the first flock numbered more than 300 and passed by before dawn.  Crow flocks continue at mid-altitude throughout bird rush hour.

The cardinals and song sparrows wake up next and exchange a few contact calls.  No flocking for them.  They just want to make sure their friends made it through the night.

Then mourning doves wake up and zoom by in small, fast groups. 

Next come the starlings and robins.  The starlings roost at the Birmingham Bridge and fan out in all directions at dawn, moving fast just above the rooftops.   The robins roost near the Bloomfield Bridge and fly in loose flocks at high altitude. 

Normally the birds manage to avoid congestion by picking different altitudes but this morning it was foggy.  A couple of starling flocks and robins had to divert to avoid the crows.  I could hear the robins commenting about it.  “Watch out there,” they seemed to be saying. 

And by then I was awake.  Time to join the human rush hour.  (That’s the Parkway East pictured above via my cell phone.)