Since midsummer we’ve lost more than five hours of sunlight so there’s not much reason to sing.  The migrant songbirds have left and only our locals (chickadees and cardinals) and some winter visitors (dark-eyed juncoes) remain.  Most of them have nothing to say.

My only hope for birdsong is at dawn and the singer is the bird pictured here - the Carolina wren.

According to the range maps, Carolina wrens don’t migrate but I wonder if they change territories in the winter.  What explains the new scuffles and song duels they engaged in in October?  Why does each wren now sing briefly at dawn? 

I hear them pipe up one after the other.  “I’m here,” says the wren down the street.  “I’m here,” says another across the ballpark.  “I’m here,” says a third up the hill.  After this brief exchange of greetings they fall silent. 

You have to be out early to hear birdsong this month.

(photo by Marcy Cunkelman)

Dead trees are treasure troves for woodpeckers too, and in the bird world they wield the ax.  Though the leaves have fallen the weather is still warm, the larvae are still active inside the bark, and the woodpeckers can hear them.

This weekend I found a pileated woodpecker excavating a dead tree in Schenley Park.  Among birds, the pileated’s beak is about as close as you can come to an ax.  The bird itself is the size of a crow with a beak 1.5 to 2 inches long.  That may sound small but his beak hits the wood at 13-15 miles per hour so the woodpecker experiences 10G’s of force at each blow.  

It would kill you or me to slam our heads against trees but the woodpecker’s head is designed for the work.  His neck absorbs the impact and his brain is cushioned by a network of flexible cartilage and spongy air-filled bone.  His tongue is very long for probing the openings he creates – so long that it retracts inside to the back of his skull.  It’s the right equipment for chopping trees.

Keep a lookout this month for pileated woodpeckers.  November is the month for the ax.

(photo by Dick Martin)

The answer is a surprise.  It turns out that some yellow-billed cuckoos raise a second family in the thorn forests of western Mexico.  And so do orchard orioles, hooded orioles, yellow-breasted chats and Cassin’s vireos.

Called “migratory double breeding” the discovery was stunning.  Scientists knew of just two Old World species who did this on their journey north but no birds had been found to do it in the western hemisphere and none anywhere were known to double-breed on the southbound trip.

Gathering the evidence was truly detective work.  Scientists were in the thorn forests in July and August, expecting to study the molt cycles of migratory songbirds.  Instead they found males singing on territory, female birds with established brood patches and no young birds as they’d expect if the families had already bred in the forest.  The clincher was when they found the nests and eggs.

If five songbird species are double-breeding in the thorn forest, why did it take so long to discover it?  July and August are forbidding months in western Mexico.  It’s the monsoon season with temperatures at 100 degrees, humidity at 100% and lots of biting insects.  People have only recently begun to farm the region, leading to a decline in thorn forest habitat.  Interestingly, the habitat decline coupled with migratory double-breeding may explain the decline of yellow-billed cuckoos in the western U.S.

So like the story of a man who has two families half a continent apart, these birds must hurry to squeeze in a second family in western Mexico, then finish their migration to tropical Central and South America.  That’s what the rush is all about.

Read more about the discovery in this Science Daily article.

(photo by Chuck Tague)

Sometimes you can’t see a bird’s traits until they’re frozen in a photograph.

Look closely at this American goldfinch browsing on Sam Leinhardt’s zinnias.  Even though only the top of her head is visible you can see both of her eyes. 

Goldfinches are small birds about 4.5 inches long.  At this size they are easy prey for owls, cats and hawks so they have to be wary.  What better way to be prepared than to have peripheral vision above and behind so you can see danger coming, even when your head is down feeding on seeds. 

Many small birds have this trait, but how did they get it?  Indirectly, from the relentless pressure of predators.  Goldfinches who couldn’t see danger coming were easy prey while those with wide peripheral vision survived.  The survivors had “kids” with the same trait.

So, yes, she really does have eyes in the back of her head, just like all her relatives.

(photo by Sam Leinhardt)

I used to think blue jays didn’t migrate because their range map shows them as year round in North America.  Because I see them all year, I assumed I was observing the same individuals.

That was until one May morning at Lake Erie when I saw a long line of jays flying northeast along the shore.  Chuck Tague told me they were flying to Canada but the lake was a big barrier.

As we watched, the jays turned north over the lake and hit a wall of air none of us could see.   One by one they battled the invisible barrier.  Finally they broke formation and flew back over land where they regrouped and again proceeded in a line, following the shore.

Other than similar observations at migration hot spots, blue jay migration is subtle if it occurs at all.  Blue jays don’t have to leave home if they can store enough food for the winter.  When they do decide to migrate, they travel during the day in small groups of 10 to 30 birds.  It often doesn’t look like they’re migrating because the jays fly one at a time from tree to tree, a behavior that resembles foraging.

This fall blue jays are leaving Canada in droves because their winter food supply is low – too few acorns, beechnuts and hazelnuts.

I’m sure they’ll enjoy their time Pittsburgh.  We have a bumper crop of acorns.

(photo by Chuck Tague)

Yesterday morning I stepped out on the front porch just after 6:00am to check the weather.  It was my first morning home from Maine and I was a little surprised that I didn’t need a jacket and the sun hadn’t come up yet.  What was I thinking!  Maine is certainly colder and it’s so far east that the sun rises there 45 minutes earlier than it does in Pittsburgh.  I had nearly an hour to wait for dawn.

As I gazed at the waning moon I heard a sound like spring peepers coming from above.  I knew the distinct solo “peeps” were the nocturnal flight calls of migrating thrushes, but which ones?

The pre-dawn sky was clear with a light wind from the north.  The birds kept coming with hardly a pause.  I rushed indoors to get my binoculars but it was too dark to see the birds.  In my excitement I forgot to count the sounds so all I can tell you is that they passed by steadily for 20 minutes.  My guess is there were several hundred of them. 

Later indoors, I checked my birdsong CDs and the Internet for samples of nocturnal flight calls.  I couldn’t find any audio examples – only voice-prints – but I looked through descriptions of various thrushes’ calls and found this at eNature’s Sibley Guide for the Swainson’s thrush:  “Flight call a mostly clear, level, emphatic heep or queev reminiscent of Spring Peeper (treefrog) call.”

So that’s who they were. 

I heard Swainson’s thrushes migrating this morning, too.  I wish I could have seen them.

(photo by Chuck Tague)

I studied those pages many times but it was hopeless.  The birds in the pictures were females or juveniles.  Some had wing bars, some did not.  Much as I tried I couldn’t identify those tiny, olive-green and yellow birds. 

For many years I was cowed.  Finally I bought a field guide that didn’t have those pages and solved my problem by avoiding it.

Years later I’m able to identify many fall warblers and I didn’t do it by paying attention to them.  Instead I spent May after May looking at spring warblers.  I got used to identifying the adults, noticing their body shapes, bill sizes and whether they had eye stripes, wings bars or beady eyes. 

Eventually I realized that young warblers have the same traits.  A long, thin-bodied warbler is still long and thin-bodied whether it’s young or old.  An adult warbler who feeds by poking under bark will have babies who do the same.  A warbler with a beady black eye, like this female yellow warbler, has a beady black eye at every age.

I’m still confused by most fall warblers – and a couple of spring ones too – but I enjoy them more since I gave up trying so hard.

(photo of a female yellow warbler by Chuck Tague)

These prothonotary warblers were courting and planning a family when Kim Steininger snapped their picture in the Cuyahoga Valley in May.  Now they’ve finished breeding and are leaving for their wintering grounds somewhere between Veracruz and the coast of Venezuela.

So how short a time are prothonotary warblers here?  Their year is almost evenly divided into three-month periods of activity: 

• Northward migration from late February to early May,
• Breeding from May through July,
• Southward migration from August through October and
• On their wintering grounds from November through January. 

If there’s any variation in the schedule it’s an increased time spent migrating and a reduced breeding period.  Despite these time challenges prothonotary warblers in the southern U.S. raise two broods.

Now they’re on the move.  Their southward migration normally peaks in Ohio from August 10th to 20th.  By mid-September they’ll be in Veracruz, Mexico.  Who knows how much farther these two will have to travel to get home.

(photo by Kim Steininger)

If watching birds is called birding, what do you call watching flickers?

.

(photo by Cris Hamilton of a very splendid male northern flicker)

First, the flocks were made up of spring migrants who chittered and ate on the way to their final destination.

The second phase was courtship in which trios flew synchronously, chittered loudly and completely followed each others’ moves.  Eventually those trios became pairs as the females chose mates.

During the nesting phase the flock was cut in half because one adult of each pair was always in the chimney incubating, brooding or tending the young.  The smaller flock wasn’t nearly as noisy.  No need to shout, the courting is over.

And now the babies are fledging and the flock is double or triple in size and noise. 

It’s fun to watch the fledglings learn to eat on the wing.  They still expect their parents to feed them so they follow them closely and beg a lot but their parents don’t stop.  The adults lead them through clouds of insects and the babies, whose mouths are probably open to beg, are stunned to find insects pop into their mouths.  All they have to do is swallow.

Soon they are swerving and chasing insects on their own.  It won’t be long before they’re as skilled as their parents and become indistinguishable as members of the flock.

(photo by Chuck Tague of a rescued chimney swift just before it fledged)