Dipper smarts

Posted on December 30, 2017 by Alistair

 

Dot: This is the second of two postings about the behaviour of a dipper, dubbed Dot, owing to a white spot on its back.

Once thought to be a uniquely human characteristic, the use of tools is considered a sign of intelligence. Only a handful of animals have been credited with employing tools.

A tool is defined as any physical item that can be used to achieve a goal, especially one that is not consumed in the process. For example, sea otters use stones as tools to crack open mollusc shells so as to eat the abalone inside.

Interestingly, dippers face a problem similar to that of sea otters, but with caddisfly larvae. The larvae are encased in found materials (sand, wood) that prevent easy access to the grub inside. A solution sometimes employed by a dipper is to shake off the casing. That, of course, does not represent using a tool, which would necessitate using of an external physical object for the task.

However on this occasion, a dipper does seem to make use of a tool.

A dipper surfaces from a dive with a caddisfly larva encased in found material. Dot is standing in shallow water atop anchor ice.

To remove the casing, Dot swishes it through the water. The water has become the tool that is used to remove the casing, much as a rock is used to remove a shell by a sea otter.

The casing having been removed, the grub is exposed.

Five seconds after the first picture, the larva has been consumed.
Can we really credit this dipper with having employed a tool to gain access to the grub?

Posted in birds, bugs | 5 Comments

Dipper amidst ice

Posted on December 29, 2017 by Alistair

 

This will be a two-part posting about Dot, the dipper.

It is not unusual for a dipper to be featured on this blog. Although, not a common bird, I happen to live near dipper central and manage to watch this strange aquatic songbird now and then. Two days ago, as the temperature dropped, I was curious about how dippers might be handling their creek’s border ice and anchor ice. After all, dippers feed primarily on the stream bed, and either form of ice can block a dipper’s access to their delectables.

I wrote about dippers and ice in one of my longer essays. In it I explored how dippers deal with a creek’s ice, and even speculated that it was ice formation that influenced their preference for turbulent waters.

This time I was able to watch something new, indeed, two somethings new. The first, considered here, is a minor wrinkle. The second, treated in the next posting, is a more interesting behaviour. Both postings treat the same bird, one with a white spot on its back, and so dubbed, Dot.

The problem faced by dippers when the temperature drops is that a creek freezes. Border ice forms in the calmer waters along the stream edges and so squeezes access from the surface. Indeed, in tranquil streams, border ice spreads across the stream and blocks all access to the stream bed. While this is minimal on fast flowing streams, it is there that anchor ice forms on the stream bed. Sometimes a creek has a goldilocks zone where the flow is not gentle enough for border ice to cover it all, but not turbulent enough for anchor ice to spread over the bed. On this occasion, I did see one dipper hunting in such a zone. However, Dot opted to hunt amidst the chaos, finding access to the stream bed in the smallish gaps between both forms of ice.

This is general area in which Dot was hunting. The border ice is atop the water, while the anchor ice is the patchy greenish ice on the stream bed. The dipper must find gaps between both.

Dot would watch while standing in the water atop the anchor ice covering a weir.

From this perch, Dot would dive into the waters below to search between patches of anchor ice.

After one of its dives, Dot surfaced with a quickly downed fertilized egg of a Kokanee. The white spot that gives this bird its name is visible on its right side.

Posted in birds, fish | 7 Comments

Wearing red

Posted on December 25, 2017 by Alistair

 

“It is my understanding that this is a good day to eat well and wear a red cap.”

Posted in birds | 8 Comments

Whither tundras?

Posted on December 13, 2017 by Alistair

 

Seeing seven swans yesterday was both a pleasure and a disappointment. It was a pleasure to be able to watch these magnificent Trumpeter Swans; Yet, it was a disappointment that once again, they were Trumpeters rather than Tundras. 

Two species of swans migrate through this region — indeed through all of the southern interior of the Province: Trumpeter Swans and Tundra Swans. If we go back three decades, most of the migrating swans were Tundras. At that time, one yearned to see a few Trumpeters. Now most of the migrants are Trumpeters, and now one yearns to see a few Tundras. 

What has brought about the transition? I do not know. But, it remains: I now fervently watch for Tundra Swans.

Three (of seven swans seen were) magnificent Trumpeter Swans swim across the water.

One left the group and then flew past me.

After it alighted, it realized it was being watched, and barked its displeasure.

It then drifted away across the water.

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Irruptive winter?

Posted on December 4, 2017 by Alistair

 

Irruptive species of birds are ones that don’t migrate to a particular region every winter. Rather, they do so some winters, but not others. This year is shaping up to be a good year for seeing irruptive species around the Lake. Here are three seen a few days ago.

Redpolls have already been mentioned this year, but there are many around.

Bohemian Waxwings are back in good numbers.

So far, I haven’t seen many Pine Grosbeaks, but a few females were enjoying rowan berries.

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Otter visit

Posted on December 2, 2017 by Alistair

 

Three River Otters visited early in this morning’s cerulean twilight.

The otters promptly went through their usual routine of shaking water off of their fur, and then marking the dock as now belonging to them. Rather than illustrating those activities, I emphasize their curiosity, in particular, their curiosity about being watched by a distant human on the shore.

Three otters climbed onto a dock and looked around.

Two of them sat up to get a better look at me.

The third dived into the water and swam towards me for an even closer view.

Posted in mammals | 7 Comments

Dipper hunts eggs

Posted on December 1, 2017 by Alistair

 

The dipper is an unusual songbird. It dives in cold, swift mountain streams for delectables that are usually found on the stream bed. What it eats depends somewhat on the season: often aquatic arthropods in the summer, fish eggs in the fall and winter, and maybe the odd fry when anchor ice might coat the stream bed.

This is the season where a dipper goes after fish eggs, and in Kokanee Creek, this usually means the eggs of the Kokanee salmon. After diving for eggs on the stream bed, a dipper surfaces and usually doesn’t swallow them until perched on a rock, the shore, or border ice.

Kokanee eggs come in two different colours: clear when unfertilized; somewhat golden when fertilized. 

A dipper surfaces with an unfertilized egg of a Kokanee salmon.

A dipper surfaces with two eggs of a Kokanee salmon, one of which may be fertilized.

Although there might be only a few dippers working the same creek, each is remarkably territorial and will aggressively chase rivals. This dipper is doing the chasing.

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Iron-rich mud

Posted on November 26, 2017 by Alistair

 

Swans have white plumage — eh?

The Trumpeter Swan near the mouth of Kokanee Creek is still there. Yestermorn, it was close enough to the shore for a detailed view. 

A striking feature of our subject is that its head and neck are covered with blotchy rusty stains. What has happened to a swan’s canonical snow-white plumage? 

The answer lies in the iron-rich waters and mud that were ingested during foraging at the Arctic breeding grounds. It is oxidized iron that gives some feathers their rusty hue.

Our visiting Trumpeter Swan has been foraging in iron-rich mud.

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On the rocks

Posted on November 25, 2017 by Alistair

 

On the surface of it, on the rocks, has to be a dumb theme for a posting.

On the rocks: The phrase has its origin in coastal ship wrecks. From there it took on the metaphorical meaning of a state of ruin, disrepair, or destitution. (One wonders about the message when used to describe the adding of ice, the rocks, to whisky.)

What might the phrase have to do with local nature? Metaphors aside, after watching wildlife for years, one comes to realize that some animals regularly hang out around rocks, and others avoid them. This realization was prompted by the last two, recent, pictures. Other pictures shown are are somewhat older. 

Most megafauna avoid rocks. The exception being the mountain goat, and to a lesser extent, the bighorn sheep. The appeal is the cliff-sustaining ability of rock, where the sure-footed mountain goat can avoid predators such as the cougar. Here a mountain goat stands on a ledge only wide enough to place one foot in front of another (2014 Oct. 2).

Rocks in water serve as a convenient place for some semi-aquatic mammals to snack — as this beaver is doing (2012 Apr. 28).

Similarly, an otter will choose rocks for a feast (2015 Aug. 8).

A few birds that hunt fish by waiting and watching choose rocks poking out of the lake as a perch. Here are two young herons (2015 July 18).

A kingfisher usually prefers a higher lookout, but sometimes watches from rocks (2009 Aug. 17).

Prompting these thoughts was a dipper, a bird that frequently watches the waters from a rock.

What about this muskrat sitting on a rock? Neither hunting nor eating, it might be lollygagging.

Posted in birds, fish, mammals | 5 Comments

Swan returns

Posted on November 21, 2017 by Alistair

 

A migrating Trumpeter Swan is off the mouth of Kokanee Creek. Others have seen one at the Park for a few weeks, but this is my first sighting, albeit it far out on the Lake.

A Mallard couple has promptly taken advantage of the swan’s presence. With its long neck the trumpeter can feed in deeper water than can a dabbling Mallard. But, when the swan stirs up edibles from the bottom, the Mallards can feed in deeper waters. 

Posted in birds | 3 Comments