Colorful Feathers

 Even the plainest bird brings fascination to a quiet view.

Warbling Vireo

Most birds go far beyond plain‒they are adorned in patterns important to their own purposes and exciting to us humans with our monochromatic skin tones, which we embellish with clothing and ornaments.

Rose-breasted Grosbeak

Birds achieve these arrays mostly through pigmentation, a process as familiar to us as putting paint on a canvas except that in their case it is through the grace of genes. 

Cape May Warbler

Pigments are variable substances independent of the structure of the feather. Depending on their molecular structure they absorb particular wavelengths of light. The wavelengths they reflect back to us give us sensations of specific colors.

The most common group of pigments are melanins that produce colors ranging from darkest black to reddish browns and pale yellows. The melanins we and many other animals incorporate determine the color of our hair and skin.

Brant

Melanin provides more than just coloration. Feathers that contain melanin are stronger and more resistant to wear than feathers without melanin. Feathers without any pigmentation are the weakest of all.

Northern Gannet

Many otherwise all white birds have black feathers on their wings or black wingtips. These flight feathers are the ones most subject to wear and tear. The melanin causing the tips to appear black also provides extra strength. *

Scarlet Tanager, male

Most reds and yellows come from a class of pigments called carotenoids. These are produced by plants, and are acquired by eating plants or by eating something that has eaten a plant. Carotenoids are responsible for the bright yellows seen in goldfinches and as well as the brilliant hues of the male Scarlet Tanager.

Scarlet Tanager, female

Carotenoids can interact with melanins to produce colors like the olive-green of the female Scarlet Tanager.

American Wigeon

Spectacular effects can also be produced in some birds by iridescence, a structural quality of the feather rather than a pigmentation.

Tree Swallow

Iridescence is the result of refraction of incident light from the microscopic structures of feather barbules. The coloration of Tree Swallows is not only beautiful but glowing when seen from the right angle.

Mallard

Refraction works like a prism, splitting the light into rich component colors. As the viewing perspective changes, the refracted light gives a shimmering display beyond hues.

European Starling

Iridescent feathers change color with different viewing angles. The effect is caused by exceedingly thin layers of protein in the structure of the feather barbules. From an aesthetic standpoint they give redemption to glittering individuals in the invasive hordes of European Starlings.

Indigo Bunting

Not all structural colors are iridescent. Tiny air pockets in the barbs of feathers can scatter incoming light, resulting in a specific, non-iridescent color. Blue colors in feathers are almost always produced in this manner. Examples include the blue feathers of bluebirds, Indigo Buntings, and Blue Jays. 

If you find one of their feathers you can see for yourself how this works. First, observe it in normal lighting conditions and you will see the expected blue color. Next, try back-lighting the feather. When light is transmitted through the feather it will look brown. The blues are lost because the light is no longer being reflected back and the brown shows up because of the melanin in the feathers.

Bay-breasted Warbler

Melanins have been harnessed into wonderful patterns like the Bay-breasted Warbler. Besides these and the carotenoids there is a third pigment group the porphyrins that are produced by modifying amino acids, mostly in the otherworldly plumage of tropical birds.

The feather structures of many species also reflect light in the ultraviolet range. Because many birds can discriminate a greater variety of colors than humans, including ultraviolet wavelengths, they can appear quite different to each other than they do to us. Presumably that is how crows can tell each other apart. 

Least Sandpiper

Certainly rainbow-hued plumage gratifies my eye. Then too, I'm thankful for even the most modestly colored birds. 

* Much of the technical information in this posting comes from an article "How Birds Make Colorful Feathers" on the website of the Cornell Lab Bird Academy, 2015.

At Low Tide

Twice a day gravitational forces bring the water level in Folly Cove down to a point where foraging birds have their best chance of finding food. Periodically this happens fairly early in the morning when their appetites are sharpest and just maybe luminous light will prevail. A perfect coincidence of these conditions is a photo naturalist's delight.

Spotted Sandpiper and Red-breasted Merganser

Avian hunters congregate in shallow water and on exposed rocks to look for easy prey.

Great Egret

Greater Yellowlegs

This Greater Yellowlegs, an outsized sandpiper that customarily stays in estuarial mudflats, happened upon the sandy area visible in the Cove at very low tide.

Spotted Sandpiper

Some of the Spotted Sandpipers ambled up into the intertidal zone looking for small crustaceans in the wrack and in moist crevices.

American Robin

Those prospects attracted not only shorebirds but upland opportunists like this robin.

American Goldfinches

Goldfinches also hunted for tiny invertebrates stranded by the receding waters.

Wild Turkey

A Wild Turkey emerged like a Jurassic creature from the wood line to see what the briny meadow might have to offer.

Common Eider pair

The possibility of plucking mollusks and crustaceans from the shoreline eddies appealed to these eiders that would otherwise have to work harder diving into the depths.

Female Long-tailed Duck

Another diving duck floated serenely further out in the Cove. It may already have satisfied its hunger in the shallow water. Most of its kind have long since departed for northern breeding grounds. The greatest variety of maritime bird sightings will have to wait until cold weather drives the migrants and their maturing progeny back to our coastal waters in the fall.

Evolution and a Sighting on the Quarry

Fairly early in the morning, with the angle of sunlight low and coming from behind it, I saw an unusual bird swimming on the quarry pond. It was chunky, low in the water, with a long, slim upturned bill. I thought I was looking at a loon.

To recreate that first impression, here's a photograph of it converted to black and white. Note particularly the silhouette, proportions, and high waterline indicating heaviness.

Juvenile Red-throated Loon

Compare it to this photograph of a loon that visited the quarry earlier in the year.

Female Common Merganser

My camera and I circled around the quarry rim to a position where over-the-shoulder sun gave a brighter portrait of the bird's plumage and, importantly, it's bill. We were looking at a merganser and not a loon.

Another view of the immature loon

Plumage aside, the telltale distinction between mergansers and loons is the bill. Both birds dive for fish. Loons accomplish this with a pointed, conically shaped bill. Merganser bills are serrated and hooked at the tip, for better gripping of their prey. 

In looking into these characteristics I was puzzled that mergansers are described in the 'duck section' of the field guide while loons are grouped with grebes in a different part of the book. At first glance mergansers and loons should be taxonomic siblings. And mergansers don't resemble those other members of the duck family Anatidae with wide flat bills. What places them in that genealogy? 

Wait! One defining characteristic of the Anatidae  is a hard 'nail' at the end of the bill and ridges or serrations along its sides. Dabbling ducks use variations of these features to harvest aquatic vegetation. Over time mergansers have evolved their own configuration to specialize in capturing fish. 

I turned to local naturalist Chris Leahy for help in understanding this. His response is worth including in its entirety and reading with care. "Welcome to the fascinating world of convergent evolution, the phenomenon in which species that are unrelated phylogenetically, evolve similar physical characteristics. A frequently cited example is auks and penguins; these families are not related but because they evolved under similar conditions, they developed a wide range of physical similarities, including appearance, behavioral habits such s diving; adaptations to cold climates and frigid waters, colonial breeding habits,. food preferences, etc., etc. 

"Your loon/merganser example is similar. That mergansers (as well as other diving ducks, e.g. scoters, eiders, etc.) evolved among the waterfowl at some distance from the loons and grebes is well established. The similarity you (rightly) perceive results from both groups evolving general body shapes, habitats, habits (diving for fish), etc. under similar ecological/climatic conditions. However on a closer inspection you would discover many anatomical distinctions, such as bill form and texture, form and location on the body of feet and legs, plumage textures, etc. that belie superficial similarities. When you think about the great diversity of aquatic habitats containing a wealth of food sources, it is not surprising that similar bird types evolved from different lineages."

During its stay here this merganser has taken comfort in the companionship of the preeminent local Anatidae representative, the Mallard.

Initially it stayed as far as possible from human visitors, especially admirers with cameras. By the third day it was following the mallards' preening pattern on an island close to passersby. It seemed to be an example of convergent interests and temperaments reaching back past divergent evolutionary paths. I've only seen loons preen while afloat.

Choristers

While a few birds such as Cardinals, Carolina Wrens, crows and gulls have been steady contributors to our sonic theater all through the winter, extraordinary singers are just now coming to prominence. Of course the luxury of their sound is spilling forth because it's procreation time.

Tufted Titmouse

The titmouse's insistent "Me, me, me" seems to oscillate with a come-hither "We, we, we." Its refrain of piercing hoots from within the tree canopy is a gateway to May.

Brown Thrasher

Certainly the most operatic voice belongs to the male Brown Thrasher. Normally a secretive bird of dense thickets, it ascends to high perches for broadcasting sweet soliloquies.

Observers have distinguished over 3,000 song types from a Thrasher. This is by far the largest repertoire of any North American bird species. It delivers these in a stream of non-sequitur couplets that strikes me as an endless experiment in questions and comments: Chr, chr. You too? Look at that. Whup, whup. I'll be darned. Jeremy, Jeremy....

Northern Mockingbird

Mockingbirds likewise pick promontories to recapitulate other birds' songs, cricket calls, dogs barking and mechanical noises like squeaky hinges and squealing tires.

Usually it repeats these sounds three to six or more times before switching to another 'song.' The reprise may go on experimentally for minutes on end.

Grey Catbird

Catbirds mutter modestly punctuated by catlike mews. Their rapid strings of syllables mostly swiped from other birds are sometimes disparaged as babble by listeners who value sharp elocution. I find them the most endearing of the local mimids.

Many is the time I have been drawn out of an absent-minded ramble on Halibut Point to smile at an in-breaking song from these other creatures' business.