Hidden truth: the mystery of the median secondary coverts

I learned something new about birds while watching a bird drawing instructional video by John Muir Laws (here).

I'll do some research and present it below. But the gist is that the overlapping feathers of the wing--where the feathers closer to the back overlap the next, then the next, and so on, all the way down to the outer primary--doesn't always apply to the median secondary coverts.

Perhaps you would only care about this when drawing the wing feathers. This particular video was about suggesting the wing feathers, rather than drawing everything you know. Feather edges tend to blend smoothly on a bird's body. Wing feathers are stiffer and more individually obvious. As Laws says, however, if you draw every feather individually you'll end up with a bird that looks like a pine cone.

Here, take a look at the wing feathers on this Vermilion Flycatcher (magnified, so there is some pixelation to the photograph).

Notice that the feathers labeled 1, 2, 3 are overlapping from top down on the folded wing? One is on top, it overlaps 2, which overlaps 3. Those are the three inner secondaries, often called tertials when obviously different from the rest of the secondaries. This pattern of overlap is repeated on the primaries and the greater secondary coverts. Watch the above referenced video to easily learn these and additional wing feathers (hidden from view in this photo).

If the greater and median secondary coverts are broadly tipped with white we call them wing bars. Wing bars are only hinted at on this Vermilion Flycatcher. Notice that the greater secondary coverts repeat the overlapping pattern of the primaries and secondaries (top down or left to right in this view). But what's going on with the median secondary coverts? They overlap from the opposite direction (right to left in this view)! Apparently this is the norm for flycatchers, but not(?) other perching birds. Laws also mentioned that the secondary coverts on hawks are more complicated.

I had no idea!

Now I need to go research this.

Where to look?

Reversed covert feathers is not discussed in my ornithology text book, Ornithology in Laboratory and Field, fourth edition, 1970, Olin Sewall Pettingill, Jr. And it's not in Molt in North American Birds, 2010, Steve N. G. Howell. Nor, is it in my go-to reference, The Audubon Society Encyclopedia of North American Birds, 1980, John K. Terres. Therefore, this information is not in any book in my personal birding library. Reversed covert feathers is not a topic in Wikipedia ("covert feathers"). If it's not in the de facto "Encyclopedia Galactica," then where is this secret knowledge kept? Time to search the index of all knowledge--accurate or not--Google.

"flycatcher median secondary coverts"

"median secondary covert variation"

"median secondary covert overlap"

Nope, it's no good. But I did see reversed median secondary coverts on a Song Thrush and Lincoln's Sparrow photo. That goes against what I heard in the above video. So now I'm confused and interested. I guess I'll be looking closely at bird photographs for a while... even if I am the only one.

I'm going to start at the Slater Museum of Natural History Wing & Tail Image Collection.

After looking at several families and orders of birds it appears that perching birds may all have reversed median secondary coverts, pigeons seemed to have matching order, and ducks appear to have some with the overlap as expected with a mid-wing change to reversed. It is very difficult to tell on many of the wing specimens--some are slightly messed up, others are fluffy so that it is hard to see the edges. I don't know, on some specimens it appears that all the median, lesser, and marginal coverts are reversed.

...

I had this post written in late December and saved to publish about the first of January. Since then, however, my copy of The Laws Guide to Nature Drawing and Journaling (John Muir Laws, 2016) arrived. On page 12 I found his mention of this mystery in the 1886 Proceedings of the Zoological Society of London in the article: "Observations on the Disposition of the Cubical Coverts in Birds" by J. G. Goodchild. Is this 130-year-old scientific journal article really the most-recent discussion of this anatomical structure in literature? ["Cubical coverts?" That term has zero Google references. But it will when this post is published and indexed!]

Again, unless you are a bird artist striving for super-detailed accuracy--or an avian systematicist, you may never need to know this. But that doesn't mean this phenomenon doesn't exist!

Comparison of two breeding cormorants

At La Jolla Cove the cormorants were nesting on the cliffs right below the walkway. Several people were taking photos and many more were stopping to watch the antics. One particular nest was receiving a lot of attention as the just-hatched chicks were peeking out from under the parent.

Brandt's Cormorant and chick. La Jolla, California. May 1, 2016. Greg Gillson.

Brant's Cormorants have a pale patch of feathers on the throat. In the spring the featherless throat pouch turns a brilliant blue. The breeding display consists of flipping the head backwards over its back and ululating with fluttering throat pouch displayed to the sky.

A couple of Double-crested Cormorants were also on the cliffs. They have a yellow-orange throat pouch throughout the year. As you can see by the photo below, the high breeding plumage brings a tuft of white feathers back from the eye. These are the "crests" mentioned in the name. Interestingly, these crests are white in Western birds, but black and larger in other populations across North America. Double-crested Cormorants are found in marine and fresh water across the continent, while other cormorants in North America are primarily restricted to salt water habitats. Notice that the eye is circled by blue--it's actually the eyelids in breeding plumage!

Double-crested Cormorant. La Jolla, California. May 1, 2016. Greg Gillson.

I love the coppery pattern on the back and wing coverts that birds, such as the one above, show in fresh plumage. As the feathers wear they lose their shine and appear dull blackish-brown.

An eponymous Ring-necked Duck

Like the orange crown on the Orange-crowned Warbler, or the sharp shins on the Sharp-shinned Hawk, the neck ring on the Ring-necked Duck is usually not obvious to birders in the field.

That's what happens when the person that officially names the bird is the often curator of a distant museum where the dead birds were shipped for cataloging, and not the person who observed the bird in life. And, because of the rules of priority*, we cannot go back and rename the bird to something that makes sense.

* Well, actually, this only applies to the scientific name. Amateur zoologist, Edward Donovan found this duck in a local meat market in London (where this North American bird is accidental). He described the bird to science in 1809 in the journal British Birds. He named it Aythya collaris, which literally means "collared seabird (duck)" or "neck-banded duck." So, Ring-necked Duck is an appropriate English match for the scientific name.

This photo shows how the drake often looks in the winter...

Ring-necked Duck. Lake Dixon, Escondido, California. April 15, 2016. Greg Gillson.

The copper neck ring between the purplish head and the black breast is seen in this recent photo where the neck is stretched in an alert posture...

Ring-necked Duck showing copper neck ring. Kit Carson Park, Escondido, California. April 10, 2016. Greg Gillson.

The Duck Test

Many non-birders look at the coot and think: "If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck."

American Coot. Dixon Lake, Escondido, California. April 15, 2016. Greg Gillson.

A closer look however, reveals several characters that do not match a duck.

First, note the white chicken-like pointed bill with the frontal shield up the forehead. That is not at all like the spatulate bill found on most ducks.

And "quack"? Nope. The loud grating call could not really be called a quack.

It does swim. And it may appear to swim like a duck above the water. But below the surface are some "not duck" toes! Ducks have webbed feet--webbing between the front toes, but coot have individually flattened toes.

American Coot. Kit Carson Park, Escondido, California. April 10, 2016. Greg Gillson.

Coot toes.

Conclusion: NOT a duck.

Western Sandpiper at Mission Bay

Western Sandpiper showing semipalmated toes. Mission Bay, San Diego, California. February 16, 2015. Greg Gillson.

On the East Coast, one of the most abundant little shorebirds of the beaches and tidal flats in migration is the Semipalmated Sandpiper. This species is decidedly rare on the West Coast, though annual in small numbers.

Instead, we on the West Coast have two similar small shorebirds. The Least Sandpiper is the smallest of the "peeps" (so named for their peeping calls). The Western Sandpiper is larger, but only 6-1/2 inches long from bill tip to tail tip.

As you might guess from the name, Semipalmated Sandpiper has something called semipalmations. What are those? Partial webs between the toes. It is similar to the flap of skin between your thumb and forefinger.

However, the Western Sandpiper also has semipalmated toes, as you can see in the photo above. Many other shorebirds do too. Scientists who name birds aren't always the most original.

Who's bigger?

Short-billed Dowitcher (left) and Black-bellied Plover (right). Mission Bay, California. February 16, 2015. Greg Gillson.

If you look in a field guide you will see that the length of the Short-billed Dowitcher is 11 inches, while the Black-bellied Plover is 11.5 inches long--very close to the same. That's measured from bill tip to tail tip. Obviously the plover is a much larger bird than the dowitcher. But unless I see them together I never realize how large the plover is in comparison!

Even the long legs of the dowitcher--used to wade out belly-deep into the water--seems stumpy compared to the legs of the plover. However, the plover spends most of its time up on the beach, rather than wading. So they aren't often seen together like this for direct comparison.

The dowitcher is twice as long as the Least Sandpiper, and usually looks big compared to the other small shorebirds around it at water's edge.

Flexible bills

Yawning Dunlin. Crown Point Park, Mission Bay, San Diego, California. February 16, 2015. Greg Gillson.

The bill of most birds is covered with a hard outer material. That would make sense for woodpeckers to drill dead branches, sparrows to chew the husk of seeds, and eagles to tear apart prey.

However, as you can see above, the Dunlin can bend its upper mandible slightly upward, opposite from its normally slightly down-curved bill angle.

I don't find a lot of information on flexible bills. In North America, other shorebirds such as snipe and woodcocks have notably flexible bills. The bills are able to feel below ground or water for worms and crustaceans that they eat.

The one bird in the world most noted for a flexible bill is the Kiwi, of New Zealand.

Here is the same bird a few moments later showing the typical bill shape.

Dunlin were also known in the past as Red-backed Sandpipers, as they have rusty backs in breeding plumage and most of the belly is covered with a large black patch.

A flock of Dunlin is evidently called a "fling." (Also a "flight" or "trip" of Dunlin.)

Come flop down on the beach with Black Skimmers!

A very relaxed Black Skimmer. Crown Point Park, Mission Bay, California. February 16, 2015. Greg Gillson.

There is nothing wrong with the Black Skimmer pictured above. They often rest with their heads on the beach like that! In fact, the Sibley Guide to Birds depicts one of the the birds exactly like this.

They are in an order of birds (Charadriiformes) that also includes the families of plovers, sandpipers, gulls, terns, skuas, and auks, among many other similar birds around the world. They all share skull similarities, webbed feet, and vocal structures.

But even though they are like these other birds, they are also different. Skimmers are just weird. They are very unusual--in many ways.

The lower mandible is much longer than the upper. They skim the water--and even the sand--with their bill as they fly slowly along with deep wing strokes primarily above the horizontal and head held down. As the bill contacts fish or crustaceans the head pulls back and then up as the bird swallows the food and then the head is dipped down again.

The eye of the skimmer has 5 times more rods than cones--enabling it to see well in low light conditions. Not surprisingly, they often feed at dusk/dawn, even at night, during low tides. However, since they often rest on bright sandy beaches in the sun, their pupils constrict greatly. Again, unique, their pupils contract in vertical slits like cats, and are not round as in other birds.

You may notice a metal band on the leg of the bird above. I think they are Mexican bird bands--they start with the word "Aves" (rather than "USGS"), and have some numbers, but I can't see the entire band to read it all.

A more respectable resting posture?

Is it my imagination, or do these look like horizontal penguins with Candy-Corn bills?

Short legs with webbed toes, but they rarely swim. Skimmers are just weird.

What's up with the nostril down on the side of the upper mandible rather than on top?

Additional photos from a post in December 2013 are here: Black Skimmers at Mission Bay