Outside My Window

Why is this bird in such a hurry to migrate south in mid-summer after raising only one brood in North America? 

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)

November is prime time for duck migration so despite the fact that the weather has been too nice for them I’m going to go look for ducks today.

Too good for ducks?  Yes, it’s been gorgeous.  Warm days, sunny skies and a south wind.  Ducks are forced to migrate when the lakes freeze (no chance of that this week!) and like all fall migrants they prefer a tail wind from the north. 

So I’m not expecting much but I still want to know…  Are the ducks here yet? 

(photo by Brian Herman)

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…Later… after visiting Yellow Creek State Park:  As I suspected it was not great for ducks but I found American coots, ruddy ducks, and pied-billed grebes, plus two mallards, one female ring-necked duck and four gadwall.  It was a better day for hiking than for ducks – but warm!

Tundra swans are on the move.

Last Sunday at the Allegheny Front we heard three flocks whoo-ing overhead before we saw them very high above us, heading southeast to the Chesapeake.  That night I heard another flock pass over my house though I couldn’t see them in the dark.  As their voices faded in the distance I heard a lone swan following them.  He had fallen behind.

Swans and geese fly in V formation because it cuts down on wind resistance.  The lead bird takes the brunt of the wind and expends the most energy.  The birds who follow fly just above the wing of the bird ahead of them and ride a cushion of air created by the previous bird’s wing.  Eventually the lead bird tires, falls back in the flock and lets another bird take the point position.  In this way the entire flock shares the burden and is able to fly further without becoming exhausted.

A lone bird gets no benefit from the V formation and, if he’s trying to rejoin the flock, he must fly faster than they do.  If they don’t slow down, how can he ever catch up?

Tundra swans travel in family groups and pause more often during fall migration so their young can regain energy and keep up with the flock.  Juvenile swans are especially vulnerable if they fall behind because they don’t know the migration route.  They learn it from their elders on their first trip south.   If a juvenile becomes separated from the flock, he’s lost.

It’s poignant to see a lone juvenile tundra swan in November.  When I do I always hope another flock will come along to take him in.

(photo by Steve Gosser)

(p.s.  How to recognize juvenile tundra swans:  In this picture there are three adults and four juveniles.  The adults have bright white heads, the juveniles have grey heads that gradually lighten to white on their necks.  Sometimes the juveniles have pink on their bills.)

Since I missed the Allegheny Front Hawk Watch last weekend I’m itching to go out there today – but I can’t, I have to work.  To compensate for this I spent time last evening looking through the hawk watch records at Hawkcount.org.  The statistics are fascinating and they support a hunch I started to develop last year.

Every fall I attend two hawk watches 775 miles apart.  In early September I visit the Cadillac Mountain Hawk Watch in Maine and see mostly American kestrels and sharp-shinned hawks, approximately one kestrel for every two sharpies.  Then in October/November I visit the Allegheny Front where the most common hawks are sharp-shins and red-tails in nearly equal numbers.  The kestrel count there is low, sometimes insignificant. 

I used to think my experience at Cadillac Mountain was normal for September and that I missed seeing kestrels at The Front because I visited it too late in the fall.  (That’s how I miss broad-winged hawk migration.)  But I had a hunch I’d got it backwards.  Perhaps, I thought, kestrels are scarce and my experience at Cadillac is unusual.

The numbers at Hawkcount.org bear that out.  Compared to the number of sharp-shinned hawks, kestrels are 40-60% as numerous at Cadillac but are only 4-10% as numerous in Pennsylvania.

Kestrels really aren’t a big item at most hawk watches and my experience isn’t “normal.”  I prefer to think of it as special.  Special, like the kestrels themselves who are one of the most beautiful raptors on earth.

(photo of a male American Kestrel by Brian Herman)

Canada Geese have been moving south for several weeks now.  Yesterday morning I saw hundreds of them resting near Millers Ponds at Pymatuning.  These geese are true migrants, probably just arrived from their breeding grounds in the southern James Bay region of Canada.

I mention them as migrants because in Pennsylvania we have plenty of resident geese.  It seems hard to believe but the subspecies Branta canadensis maxima (Giant Canada Goose) was nearly extinct in 1900 due to overhunting and habitat change.  Many states conducted reintroduction programs to help the geese along.  The birds so did well that there are now nearly 290,000 resident maxima Canada geese in Pennsylvania and their population keeps growing despite a special hunting season instituted in 1992.

Why don’t our resident Canada geese migrate? 

Geese travel in family groups which collect at staging areas to join larger flocks.  The young geese learn their migratory paths from their parents.  If their parents don’t migrate the whole family stays put.  I’ll bet the geese that were reintroduced had no one to teach them to migrate so they and their descendants became residents.

Not so with the geese at Pymantuning.  By 5:00pm when I left Linesville all the migrant geese were gone.

(photo by Cris Hamilton)

This year is different. 

We usually don’t see huge flocks of grackles in Pittsburgh until late October but this year they showed up in the third week of September. I first noticed them in large groups in Schenley Park, gathering in the treetops at dusk.  Since then they’re most noticable on rainy days when they graze on neighborhood lawns and fly low over the road.

Common grackles are diurnal migrants who tend to move in mixed flocks with blackbirds and starlings.  Within the flocks you can pick out the grackles because they have long tails and make a low “chuck” sound as they fly.  Though I’ve looked for other birds among them, the recent flocks are nearly 100% grackles.  When they gather at dusk their “rusty gate” voices are very loud.  Then they take off in unison – an impressive sight. 

I wonder why the grackles are early this year.  Is there less food up north than usual?  Is winter coming early?  Do they know something we don’t know?  Probably.

(photo of a flock of brown-headed cowbirds by Chuck Tague.  Are there any grackles mixed in?  Look at their tails.)

Are you seeing a lot of blue jays lately?  I am. 

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)

If you’re in WQED’s viewing area at 10:30pm on Thursday September 3 don’t miss On The Wing, a half-hour video about the swifts who roost in Chapman Elementary School’s chimney in Portland, Oregon during fall migration.

Not your typical nature movie, On The Wing is as much about Portland and the people who watch the swifts as it is about the tens of thousands of Vaux’s swifts who come to roost.  The swifts circle and swirl around the chimney, a few hawks and peregrines come in for an easy meal, and hundreds of people show up to watch.  It’s a huge event.

The phenomenon became so famous and well-loved that it changed Chapman School.  The swifts huddle in Chapman’s chimney to stay warm on cold September nights and the kids were huddling in the school by day to avoid killing the swifts by turning on the boiler.  Eventually Chapman replaced its heating system so that the chimney is now used only by the swifts.

As soon as you see this movie you’ll wish you were in Portland, Oregon to watch the birds but you don’t have to travel that far.  Eastern cities have chimney swifts, very similar to Vaux’s swift, and we have chimneys.  We can’t offer the community event that happens at Chapman (you will have to go to Portland for that) but you can watch our swifts go to roost. 

In Pittsburgh there are many chimneys to choose from.  Look for tall stand-alone chimneys, usually made of brick, and you may find a roost near home.  Here are some of the roosts I’ve seen:

• At South St. Clair Street, across the street from 5802 Baum Boulevard, look at the chimney across the parking lot.  Three Rivers Birding Club usually visits this chimney at least one evening during migration… and then we go to The Sharp Edge for beer. 
• In Oakland on Clyde Street near Central Catholic High School, watch the tall chimney on an apartment building on the left.
• In Dormont, start at the corner of West Liberty Ave and Edgehill Ave.  Walk up the right side of Edgehill Ave to the second telephone pole that has a sign on it saying Weight Limit 9 Tons.  Stop and look across the street & you’ll see the chimney.
• In Squirrel Hill at the corner of Murray and Forward Avenues there are lots of chimneys.  I’m not sure they’re used by swifts but it’s worth a look. Stand on Pocusset.
• Check out the closed public schools: the former Schenley High School, former Gladstone Middle School, etc.  I bet you’ll find swifts.

Meanwhile, watch a preview of the movie!

(photo from Dan Viens, creator of On the Wing)

The amazing thing about warblers is how short a time they’re with us. 

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)