Exploring Kootenay Lake

Unusual birds have been visiting Kokanee Creek Park: the White-winged Crossbill. Our area is on the southern edge of its range. I have seen it around here a few times, but never in the same place.

The bird is named for its crossed bill: its two mandibles do not meet at a point, although more of the birds have the lower mandible crossing to the right than the left.  When born their beak isn’t crossed but becomes crossed about the time they fledge.

This odd adaptation results from how it extracts its favourite food: the seeds from conifer cones. This search for cone seeds, in turn, causes it to roam widely over the northern woods. It seems to not have a regular nesting place or time. It has been seen to nest any time in the year where there is a good supply of food.

This is either an adult female or a juvenile male. Photo by Cynthia Fraser.

The adult male’s body is red but black wings have two white bars. Photo by Cynthia Fraser.

Mobbing in birds is an anti-predator activity in which smaller prey mob a larger predator by cooperatively attacking or harassing it. It is usually done to protect offspring. Behaviour includes flying about the predator, dive bombing, loud squawking and defecating on it. The smaller prey are usually quicker and more manoeuvrable than the larger predator, making it difficult for the mobbing bird to be captured. 

My blog postings are usually preceded by taking a picture of the event. Not on this occasion; I did not recently see any mobbing. Rather this posting was prompted by Bob McDonald’s C.B.C. programme, “Quirks and Quarks“. Mr. McDonald interviewed Madeleine Scott, an Oregon scientist, about mobbing of the Northern Pygmy Owl, and she observed that these mobbing events were more likely to happen during the spring and summer seasons, when food becomes more abundant for the songbirds.

Now, I have seen many Pygmy Owls but have never seen them mobbed. But I only see this owl during the winter in the valleys, apparently not the time when they are mobbed. During the breeding season around here, this owl heads high in the mountains. Apparently Ms. Scott conducted her experiments on the broad eastern Oregon plains where there was no opportunity of altitudinal migration. Presumably, the mobbing happens around here in the mountains.

Nevertheless, it seems a good time to give mobbing a brief, backward look.

This is a local Northern Pygmy Owl seen recently. OK it is not being mobbed but I do note that the first owl I ever saw in the wild was revealed by it being mobbed. 

A Tree Swallow is mobbing a Great Blue Heron who has chosen to park close to the swallow’s nest. Repeated fly-bys of the swallow and its partner finally drove the heron off. 

A Crow goes after a juvenile Bald Eagle. There was often more than one mobbing bird, but only one is usually caught in a picture.

A Tree Swallow harasses a juvenile Bald Eagle.

And again.

I don’t know if this standoff between the Black-billed Magpie and Bald Eagle is mobbing or not.

A raven goes after a Red-tailed Hawk.

Two Steller’s Jays harass a Red-tailed Hawk.

This Northern Goshawk was being actively harassed by some ravens. It was perhaps the only reason I was able to get close to it.

It has been an unusually good year for Trumpeter Swans (but a poor year for irruptives). As a result, the opportunity has arisen to catch the trumpeters in less common situations. In this case, it was face-on activities. 

Some of the Trumpeter Swans before they took to the air.

The trumpeter is the heaviest bird in North America. So unlike some lighter waterfowl, it cannot just spring into the air to start flying. It must run for 90 metres or more across the water to pick up speed. Here can be seen the separate splashes made by the alternate feet pushing against the water as it runs.

Two photographs in sequence show a Trumpeter Swan running across the water straight towards the photographer.

When flying, the feet are tucked up out of the airstream.

But when coming in for a landing the feet are lowered to provide drag to slow the bird.

At the last moment, the feet are rotated to provide a break on the water.

One of the most spectacular things to see a swan do, is for it to stand up in the water and spread its wings. They don’t seem to do this very often, but I wondered what triggered the activity. I think I have figured it out.

Here is the object of the exercise. While normally in the water, the wings are tight by the swan’s side, now they are spread as if flying. But a swan does this only for a short time, maybe once (or a couple of times) a day. Why?

Early one morning, I then went and spent a long time quietly watching a group of about 18 swans. It gave strong credence to my suspicion.

The day began with feeding in the shallows. This went on for some time.

Next began a session of preening. This is where the swans repair their feathers. Among other things, the swan uses its bill to interlock feather barbules that have become separated. I speculated that although feathers might now be repaired, many could still be misaligned, one feather to the next. This is where the spread wing comes in.

This swan is part way through its wing spread. It will take a few more flaps to straighten all the feathers.

Not all spread-wing sightings were made by a solo swan (or in presence of a partner). A number were made in a small crowd. Juveniles also spread wings.

In the end, one of the greatest tests that the spread-wing was just a part of preening is the numbers. There were about 18 swans in this group and about the same number subsequently stood and flapped their wings. 

But, it is a grand conclusion to feeding and preening.

We have two indigenous species of swans here: Tundra and Trumpeter. But, neither species lives here permanently because they winter to the south and breed to the north. We see them frequently as they pass through, for they are both large and are highly visible on the open waters of lake and stream. Ten to twenty years ago, the most common swan seen around here was the Tundra; for some time recently, it has been the Trumpeter.

Distinguishing between the two of them can prove difficult. Although they are different in  size and breed in different places, when seen in isolation, they look very similar. David Sibley has written a web page on Distinguishing Trumpeter and Tundra Swans <https://www.sibleyguides.com/2006/02/distinguishing-trumpeter-and-tundra-swans/> which has guided some of the observations below. But, all the illustrations are from recent Trumpeter Swans. This has been a good year for Trumpeters, so much so, that these features will be spread over two postings.

After the age of two or three, most adult swans travel in pairs. They usually mate for life. 

The swan’s plumage is all white… well, not always. The orange/brown staining on the head and neck is from the iron-rich water that they feed in. Both Tundra and Trumpeter Swans can experience this.

Swans sleep on water or land usually at night. These two are napping during the day. 

A careful look at these five swans, shows four grey ones and one white one. The juvenile grey would have vanished about two months earlier in Tundra Swans. By mid-January virtually all Tundra Swans have acquired some white scapulars, while Trumpeters are still in full juvenile plumage. This picture was taken on February 10. These are Trumpeters.

A juvenile Trumpeter with mottled plumage flies behind an all-white adult.

And they fly off. 

Swans do not make their home here. They live to our south in the winter, and to our north in the summer, but they pass through this region twice a year in transit. Indeed, as they come through in dribs and drabs, a few might appear at the Lake at almost any time during the cold months. 

Today there were a dozen trumpeters in the shallows off Kokanee Park. Here are two.

Now is the time to see the Northern Pygmy Owl. Well, we have it year round, so why select now to see this daytime hunter? Well, for most seasons, it hangs out at higher elevations, a mountainous area that has a low population of humans. But come winter time, the Pygmy Owl often comes to the valley bottoms and hunts small birds such as irruptives.  

I found the Pygmy Owl on the North Shore of Kootenay Lake on Sunday, but it was perched high in distant trees, so I returned the next day. It was now hunting close to the ground beside the road. One thing about these owls is that not only do they hunt in daytime, but they are not particularly sensitive to humans. So park beside one and take its picture.