Today I’ll wrap up the wing’s flight feathers, parts two and three, secondaries and tertials.

Like the primaries we learned about last week, secondaries and tertials are remiges.  The secondaries run from the wrist to the elbow and hang from a bone called the ulna.  They’re marked here in pink.  Tertials, marked in yellow, run from elbow to armpit and hang from the humerus.  If humans had wings our secondaries and tertials would hang like the sleeve fringe on a buckskin jacket.

The number of secondary feathers varies depending on species, from six in small birds to 40 for an albatross.  Tertials are always few and usually hard to see in flight, especially on songbirds who have 9-10 primaries, 6 secondaries and only 3 tertials.

Tertial feathers are rarely mentioned except in shorebird identification.  That’s because shorebird wing structure is so different that their tertials nearly cover their primaries when their wings are folded.  In fact, when at rest, their tertials lay on top of their tails instead of over their backs.  If I was good at shorebird identification I would be able to look at the tertials and come up with the correct species.  I’d even be able to age the bird.

And finally, even jets have movable secondaries and tertials – or so I like to think.  When birds land they cup their wings and drop their secondaries and tertials to create drag and slow down.  When a jet lands, it lowers two sets of flaps on its wings to do the same thing.

Watch a pigeon land, then watch a jet and you’ll see what I mean.

(photo of a juvenile bald eagle by Chuck Tague, modified to show the secondaries and tertials)

If you’ve been birding for a while you’ve probably heard, even used, the word “primaries” but the word remiges could be new to you. It was to me.

Let’s tackle these two terms in reverse order since remiges are a more general term.

Remiges (pronounced REH.midg.iz) are the flight feathers on a bird’s wing, outlined in red in this picture.

Remiges include all the flight feathers – primaries, secondaries and tertials – and make up the entire trailing edge of the wing.

So what are the primaries?

Answer:  David Sibley describes them as “flight feathers growing from the “hand” bones and forming the lower border of the folded wing.”

The snow goose is an easy example, a white bird with black primaries.  I’ve circled his primaries in green above.

A quick way to think of primary feathers is that they’re where the bird’s fingers would be.  The difference is that there are 9 to 11 of them, sometimes more depending on the species, so they extend around the lower edge of the wing.  If you had 10 fingers on each hand, where would you put them?  Probably where the bird puts his.

Primaries are easy to see on large birds in flight.  Watch soaring red-tailed hawks and you’ll see that they spread their primaries and tip them up to reduce wingtip vortex.   Aircraft engineers design upturned wingtips on airplanes for the same reason.

So… the primaries are feathers where the birds fingers would be, and all primaries are remiges (wing flight feathers) but not all remiges are primaries.

(photo of snow geese from Wikipedia)

Winter is lousy for field work but it’s a good time to curl up with a book and learn something, so in that spirit I’ve decided to (finally!) learn more about bird anatomy. 

Yes, I’ve watched birds for decades but that doesn’t mean I know the scientific names for the parts of a bird.  During research on various blogs I’ve encountered many technical names, but what do they mean? 

Maybe the names stump you, too.  Why not make this a group project?  So here’s the first in a weekly series on bird anatomy. 

What is a culmen?  It sounds vaguely like… ummmm…. “culminate,” a related word. 

Answer:  It’s “the dorsal ridge of the bird’s bill.”  For us laypeople, it’s the top of the beak from the head to the tip, as shown by the green line. 

I encountered “culmen” when I looked for the length of the pileated woodpecker’s beak.  The answer was “the male’s culmen is 43-56 mm” so I had to look up two things:  the meaning of culmen and the conversion from millimeters to inches.

The shape of the culmen is a useful field mark for identifying birds.  Some bills (culmen) curve up as on American avocets, some are straight, and some curve down as on the long-billed curlew.

So now you know.

(photo by Chuck Tague with graphics added by Kate St. John)