Exploring Kootenay Lake

Some birds seem to have their own version of a child’s game, king of the castle. I have watched gulls and geese (the latter only during the mating season) play a game which involves approaching a perched advisory from behind to displace it. (There are other species that seem happy to share a perch.) 

A few days ago, I noticed an interspecies version of the game.

A Belted Kingfisher was watching for fish from atop a piling.

Abruptly, it dived over the side.
  

It was quickly evident that the kingfisher’s departure was a result of a Northern Flicker approaching from behind. Here the ascending flicker is seen on the left while the displaced kingfisher is partly hidden by the piling.

“I am told that it is appropriate to wear a special bonnet today.”

From the moment I spotted the fresh carcass of a Canada Goose on the shore, I knew it would be worth watching. Now, what might take an interest in this?

The first visitor was a three-and-a-half year old eagle (note, the dark flecking on its crown).

This was followed by a succession of ravens,

And a dog that was only dissuaded from stealing the prize by its (human) pack leader.

The most photogenic scavenger was an adult Bald Eagle: “Love the giblets; Hate the feathers.”

Interestingly, this eagle was driven off by the persistent harassment of other geese. Were they merely mobbing a predator, or were they objecting to the desecration of a colleague?

Following this, a one-and-a-half year old eagle landed and tried to reach the carcass. It, too, was harassed by other geese that loudly blocked its path.

My favourite shot was of the adult bald having breakfast at sunrise.

March closes with a handful of birds that just did not make the cut to have a posting of their own.

The first local sightings of the Eurasian Collared Dove were made in 2008 after they had spread across the continent from a 1970s introduction in the Bahamas. The bird is now fairly common around the Creston Flats.
 

The Dark-eyed Junco is quite common in the spring as many move north to breed. This one was singing.

How does one lose a flock of swans? These were flying along the West Arm, but I couldn’t find their destination.

Had I not seen a Red-tailed Hawk fly to this tree, I would have never spotted it in the foliage.
 

On March 30^th, a Tree Swallow arrived at pilings it previously used for nesting, but there it found a flicker. Of a group of three cavities suitable for the swallow, two already held flickers and one is being explored by starlings. It will be interesting to see how this plays out.

Yesterday I watched insectivores hunting in a field: Mountain Bluebirds and Northern Shrikes.

Two weeks ago, the treat was the Western Bluebird, which sports an orange breast and shoulders. The breast of the Mountain Bluebird is powder blue (male) or grey (female).

A male (left) Mountain Bluebird and female (right) watch for insects from a fence.

From such a perch each will swoop down and capture a bug.

Unexpected was a sight of Mountain Bluebirds and a Shrike on adjacent fence posts. While they all hunt insects, the shrike will also take small birds. Indeed, the bluebirds seem to be eyeing the shrike warily. 

I managed to get close enough to get a couple of portraits. First the (male) Mountain Bluebird,

then the Northern Shrike.
    

While she gyrated, the male Mallard watched from the beach.

Yesterday, as I watched a flicker couple excavate yet-another cavity nest on the shore side of a piling, I speculated that there might be an interesting story to be told. 

Over the years I had casually been aware that the cavity nests that the Northern Flicker constructed in pilings around Kootenay Lake seemed to follow a pattern: They all seemed to face the shore. But, would my anecdotal observations hold up to the collection of a few more observations? And if they did, what might be motivating the flickers to do this?

Elsewhere, Northern Flickers build their nests in trees, and, as Karen Wiebe noted in a 2001 paper about the flickers at Riske Creek (southwest of Williams Lake, BC), flickers tend to orientate their cavities to the south—apparently to increase the incubation temperature. Yet, that pattern, seen in the Cariboo, did not seem to hold around here. 

This morning I did a casual survey of (some easily accessible) pilings around the West Arm of Kootenay Lake looking at shorelines oriented in various directions. Where the shoreline was west of the piling, the cavities faced west; when shoreline was north of the piling, the cavities faced north; when north east, they faced that way. It was the same for south and south east. There was no preferred compass direction, certainly none dictated by the Sun. The shoreline dictated orientation. 

At first, there appeared to be two puzzling exceptions to this pattern: pilings on either side of a narrows (a constriction in the Lake), and those adjacent to a floating drydock. In these cases, cavities appeared on each side of the pilings. Yet, these make sense. If the objective is to face the shore, then in a narrows, there is an ambiguity as to which shoreline is relevant. Some of the cavities on the pilings holding the drydock faced the shore, while others faced the dock. However, from the bird’s point of view, the dock was probably perceived as merely another shore.

Now comes the first speculation: The flicker’s concern is for a land predator. It is better to see one coming and be able to vacate than to have one attack from behind. (An aerial predator could come from any direction, so there is no preferred defence there.) 

A second speculation: When flicker chicks fledge, it is better to have them fly towards land than out over water.

But, why does the Kootenay Lake experience differ so much from that of Riske Creek. Possibly because on land, a predator can come from any side so optimization might as well be based merely upon incubation temperature, and a chick can fledge in any direction.

 Yesterday’s (female) Northern Flicker. She was building a nest on the north side—the shore side—of a piling.

This is a view of last year’s flicker couple checking out a shore-facing nest. In it, they later produced chicks.

The wooden pilings holding this floating drydock contain flicker cavities that face both the shore (to the lower right) and the dock. From the flicker’s point of view, the dock is probably just another shore.