Bufflehead iridescence

 

Bufflehead Ducks might be seen throughout the year, but they become fairly common during cold months. In the past couple of weeks, buffleheads have been appearing around the area. They are our smallest duck: a black and white male and a brownish female with a white cheek patch.

The description of the male as being black and white is a tad deceptive for the black feathers on its head (although not elsewhere) can be strikingly iridescent. Five weeks ago, I showed similar magpie iridescence. The process with male buffleheads is the same: the duck’s iridescent feathers contain a basal melanin layer, which produces the black by absorption, but above that are reflecting platelets, which produce iridescent colours. The iridescence arises in a similar way as those in a slick of (burnt) oil on black pavement. Light reflected from the base of the slick interferes with that from the top of the slick to preferentially select various wavelengths. 

However, the effective spacing between the reflective layers depends upon the viewing angle so sometimes one colour is seen, sometimes another, and sometimes nothing but black. The trick is to have the proper geometry between the sun, the duck and the observer.

A group of male and female Bufflehead Ducks swim by. There is a hint of iridescence on the heads of the two males at the front. However, the bufflehead at the back (right) has his head turned and he shows no iridescence at all.

The male duck at the rear turns its head. Suddenly, a beautiful range of colours appears.

 

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Bighorny supplement

 

This is a supplemental story to that of the reluctant ewe, posted yesterday. Initially, there were actually four rams courting the ewe: the adult and three juveniles. However, the posting picked up the story after the adult ram had driven off the three juveniles (among Bighorn Sheep, dominance is largely just a matter of horn size).

Although these juvenile rams had also fancied the ewe, they were driven off, but remained horny.

So the ram at the back of the parade mounted the middle ram (while it was sniffing the ram in the front). Having been denied the comfort of a ewe, it took its pleasures with another ram.  

The second image is courtesy of Cynthia Fraser.

 

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The reluctant ewe

 

Bighorn Sheep mating seems to involve lopsided urges. My (admittedly casual) observations are that the only concession a female makes is to turn up to the rut. Beyond that, she seems uninterested in any ensuing activity.

A ram pursues an uninterested ewe. His tongue is out to sample her flank for a sign of oestrus.

The ewe tries to escape the ram’s amorous advances.

Ultimately she merely lies down and adopts a position where she cannot be mated (even when in oestrus, she remains passive). He sits nearby biding his time. I got bored and wandered away. 

 

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Mid-October

 

October is a month of transitions.

Katabatic winds flow out over the water and give rise to ephemeral sprites of steam fog. Curiously, despite the gentleness of the wind, a steam devil emerges.

The orangish colours of Western Larch have spread around the shore.

Bighorn Sheep have gathered in anticipation of the forthcoming rut.

 

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Grebe & fish

The Pied-billed Grebe gains its name from the dark band around its bill, seen only during the breeding season (2012/04/21).

 

Our four regular grebes all dive underwater to forage. The smallest of these is the Pied-billed Grebe. It mostly eats small fish and crustaceans, such as crayfish, which it captures and crushes with its stout bill and strong jaws before swallowing them.

After it surfaces with a prize, one has to be fast to see what has been caught, for the prey is swallowed in a trice.

A nearly five-year old picture, shows a Pied-billed Grebe downing a crayfish (2015/01/08).

Yesterday’s Pied-billed Grebe took only five seconds to down a small fish after surfacing.

 

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Scoter goes astray

 

Surf Scoters are really uncommon visitors to this region.

In the summer, Surf Scoters breed beside small boreal lakes, all of which are at least 800 km north of here. They winter along the Pacific coast, over 400 km to the west. Scoters have scant reason to pass this way during migration and so are rarely seen. However, now and then, storms drive them astray.

A male Surf Scoter visits.

 

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Soon to go

 

Warm-season insectivores leave the region in October as the supply of insects and spiders diminishes. Many head for the southern USA, Mexico, or Central America. Three of these soon-to-be departed species were seen on a walk in yesterday’s sunshine.

A Savannah Sparrow flies to another perch, but soon will fly far to the south.

Another Savannah Sparrow hunts a diminishing supply of insects from a branch.

A Chipping Sparrow hunts near the ground.

My favourite shot is of a female Common Yellowthroat. She, too, will fly south soon.

 

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September goulash

 

This September’s goulash is thin gruel: only two previously unposted images from a generally sparse month of postings.

There are two unusual features to this picture of a chipmunk. I usually see chipmunks in the mountains rather than at the bottom of valleys. Further, this little fellow has been spending a week raiding a bird feeder and is seen here working on one of its seeds. I am used to squirrels raiding bird feeders, but not chipmunks. This is all rather odd.

This is an immature Bald Eagle with wings spread to apparently dry them after fishing for Kokanee in the stream below. Whenever I see an eagle drying its wings in this way, they are not spread wide, but shaped in a delta. Possibly this is to make it easier for water to drip off them.

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Magpie iridescence

 

Magpies do not favour this region because it is highly forested. These birds prefer open habitats with occasional clumps of trees. Consequently, there are few opportunities to capture pictures of magpie iridescence.

The pigmentation of a magpie’s feathers produces a plumage that is strictly black or white. Yet in some lightings, the black feathers on the wings and tail produce brilliant colours, particularly blues and greens. These colours do not result from pigmentation, but iridescence.

Cells in the iridescent feathers contain a basal melanin layer, which produces the black by absorption. Above are stacked reflecting platelets, which produce the iridescent colours when light reflected from one layer interferes with that from another. The resulting colours are bright, pure and strongly directional. A bird can use this for flashing a signal in one direction, while remaining inconspicuous to a predator in another direction. 

Of the handful of pictures of the Black-billed Magpie I have taken, only a few of them show the blue-green iridescence of the wings. In this picture, taken two days ago, the tail just looks black.

However, contrast that black tail with the brightly iridescent tail of the same bird seen a half-minute later. Who knows what signal it is attempting to send?

 

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Pileated in training

 

It is not a regular sight to see two Pileated Woodpeckers jointly foraging on the same tree. On the two previous occasions the foragers were a male and female. As the Pileated Woodpecker is both monogamous and territorial, a foraging couple makes sense.

So yesterday, when I came upon two woodpeckers foraging on a utility pole, I just assumed that these two were also a male and female. Yet, the pictures revealed them to both be male.

The territoriality of Pileated Woodpeckers suggests that these two males are either rivals or family. The two of them seemed to work together and passed signals back and forth, so they probably are not rivals. But, is it a case of a father training a son? 

Cornell Lab of Ornithology notes: “Once fledgling Pileated Woodpeckers can fly well, they follow adults everywhere, depending on their parents for several months to provide and help find food. Come fall, young will separate from their parents and wander until spring, when they will attempt to acquire a mate and nest.” So, this pair is likely to be a parent and child and the pictures, below, are interpreted in the light of this assumed relationship.

Adults have yellowish eyes, while the chicks have brownish eyes. While the difference is not striking with these two, the father seems to be on the left and the chick on the right.

Signals are sent back and forth. Here, daddy tips his head back and emits a strange sort of cooing call, to which junior responds with spread wings.

It is unclear what message is being communicated here. 

However, the training seems to be successful as the chick does find some grubs. 

 

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