Irruptive meets invasive

 

The Common Redpoll is an irruptive species: an arctic species that may or may not turn up locally in search of food in any particular year. This winter, they are here. They travel in flocks which descend on seeds. Locally, they seem to be partial to the common tansy, an invasive species.

The name, redpoll, refers to the red cap they sport — poll being an old word for head, as in “take a poll” (count heads), or a “poll tax” (a tax on each head). 

Flocks of the Common Redpoll are visiting the Lake this year. They fly frenetically between feeding on one bush of the (gone to seed) Common Tansy to the next.

While they are named for the red cap on their crowns, they also have distinctive black patterns on their faces that look like the ionizing radiation hazard trefoil with the bird’s bill poking through the centre. Here a redpoll is feasting on tansy seeds.

“I’m off to check out the seeds I see over there.”

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Hoodie eats

 

The Hooded Merganser has been featured of late. First came a posting about hoodie courting, then the bird played a bit part in birds eat. The latter posting showed that, lacking teeth and any way to tear apart prey, most birds swallow their food whole. That posting merely showed a hoodie with a fish in its bill, as if that was all there was to it. Yet, as the following sequence shows, feeding is not quite that simple for a Hooded Merganser.

First, the hoodie must catch a fish. Fish don’t like being caught, so success is infrequent. This hoodie is diving after a fish, but usually upon resurfacing, nothing has been caught.

Following the struggle to capture a fish comes the struggle to retain it as other hoodies try to steal the meal. The chase is on and both birds start planing, propelling themselves with great speed across the water powered by pushing feet and rowing wings. The fish can be seen athwart the bill of the bird being targeted.

The chase continues across the water with the pursuer sometimes planing along the surface and sometimes swimming underwater, both being faster means of water travel than swimming in displacement mode on the surface.

Eventually, the pursuer tired and broke off the chase. Our hoodie’s problems are not over: The fish (a largescale sucker) is still athwart the bill, and so cannot be swallowed from this position.

Various techniques are used to try to align the fish with the bill. Often the (now dead) fish is dropped in the water and the bird swims around to its head and tries to pick it up again. Here, the bird is trying to turn the fish around by pulling on a fin. 

Once aligned, the fish is grabbed head first in the bill, but further help is needed before it can be moved down the gullet.

To swallow the fish, the hoodie must tip its head back to get the assistance of gravity.

I don’t know how long this meal will last before the hoodie must go fishing again.

Posted in birds, fish | 4 Comments

Birds eat

 

Birds do not chew their food.

Indeed, only a few birds (mainly raptors) can even tear their food into smaller chunks before swallowing it. Certainly, a few birds will pick at fruit on a tree and gulls will pick at dead fish on a beach. However, most birds just swallow whole whatever they eat. This places constraints on the size of things most birds can eat. A kingfisher does not even bother looking for a fish that a heron would happily swallow.

I reflected on this when last week I was watching two birds feeding: a Snow Bunting that was picking off grass seeds and swallowing them; a Hooded Merganser that had caught and swallowed a small fish. These are the final two pictures. The first five pictures are older and are chosen to illustrate the issue.

A raptor can grip its prey and tear it apart with its hooked bill. This allows it to eat prey much larger than it could swallow whole. This is a Merlin feasting on a Mallard (2017 April 13).

Most birds swallow their prey whole and this constrains what they can eat. A robin can easily swallow a worm or moth (2016 May 19).

Dippers mainly swallow insects and fish eggs. A fry is perhaps the largest fish it can swallow whole (2012 Dec. 10).

This is a large fish for a Common Merganser to swallow whole (2016 August 30).

However, the merganser would not have been able to handle the rather large Kokanee being swallowed by this Great Blue Heron (2015 August 25). 

A Snow Bunting picked off grass seeds and then swallowed each whole.

A Hooded Mergansers dived and then surfaced with a small fish. The event was interesting not just because the fish was swallowed whole. Unexpectedly, the catch is a member of the sunfish family, a black crappie or a pumpkinseed, both of which are native to eastern North America. They seem to have turned up in Kootenay Lake only within the last decade and neither is to be welcomed. Unfortunately, sunfish prey on small indigenous fish and have the potential to alter the local aquatic food chain. The only thing we have in our favour is that the coolness of the Lake may prevent them from becoming a nuisance.

Posted in birds, fish | 5 Comments

Hoodie courting

 

It is November and the Hooded Mergansers are courting. This may seem a tad early for such an activity, but hoodies form their pair bonds in the late fall or early winter.

First, we need a base-line look for the pair when it is not courting. The male is on the front right and the female on the back left. The feathers on their heads lie flat. This picture was actually taken when the pair bond seems to have been established, three days after the following shots.

Two males were circling and competing for the female. Each male has erected the crest on his head to show his interest in her. This is probably also a show of aggression towards the other male. Here, the female has not responded by erecting her crest, but she does so after a while. 

Hoodie males show even greater enthusiasm by doing head pumping whereby each silently extends and shortens his neck. Typically, the bird does not face the object of its desire, but presents her with the more enticing side view.

Occasionally the male will rise high in the water.

However, in the most elaborate of the male courtship displays, he keeps his crest erect, throws his head right back, and calls. How could she possibly resist?

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Kingfisher behaviour

 

I see the Belted Kingfisher perhaps once a week. It is usually just foraging and, after a brief pause, it moves on to a different location to hunt.

Yet, over time one builds up a repertoire of kingfisher behaviour. The first five pictures are old; the last three are from yesterday.

The kingfisher is often seen watching for small fish while perched (2013 Oct. 10).

Or it might be flying (2017 Jul. 30).

Occasionally, the kingfisher is seen to hover over prey (2013 May 26).

Often enough, it manages to catch and consume a small fish (2016 July 25).

Now and then it is seen to squabble with another kingfisher (2016 July 16).

By way of contrast to squabbling, sometimes one can see two of them mate (2017 May 6).

It is not that I doubted that kingfishers pooped, but yesterday was the first observation.

What was unexpected was the sight of a kingfisher casting a pallet (burping up fish bones).

However, the best kingfisher shot of the day was this one.

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Snow Buntings

 

One does not get to see Snow Buntings every year. Indeed, when you do see them around the Lake, it is likely to be for a short time in the fall. Even then, they are seen from a distance.

Snow Buntings breed in the high Arctic and seem to spend the winter well to the south of us. That they pass through our region now and then is a delight. The last time I saw them was four years ago. Curiously at that time, they were within metres of where they appeared in the last two days.

Snow Buntings forage on the surface for grass and seeds.

They do not forage alone, but in groups.

They foray in flocks of a dozen or more and frequently fly to check adjacent locations.

Not only do they forage in groups, they fly in groups. 

Here they go again. We may see them again in a few years.

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Fall to winter

 

Today, winter swept to the valley bottom. It seems that fall is not yet ready to concede defeat.

Snow blankets the mountainside, but western larches proclaim its arrival is premature.

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Pacific Loon

 

Following upon the first observation of a Gray-crowned Rosy Finch at Kokanee Creek Provincial Park, I saw a Pacific Loon at the same location. Well, truth in advertising, I only saw it because Paul Prappas alerted me to its presence. Yet, his observation ranks as a first for the Park.

There is more than one species of loon. We normally see the Common Loon, but today’s sighting was of a species of loon rarely seen in British Columbia outside of Pacific Coastal waters.

A Pacific Loon (still in breeding plumage) graces the waters of Kokanee Creek Provincial Park.

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Gray-crowned Rosy Finches

 

Grey: In Canada, the spelling should be Grey-crowned Rosy Finch. It is named for the colour, grey, not a person named Gray.

This was an unusual observation: A flock of about six dozen Gray-crowned Rosy Finches flew around Kokanee Creek Provincial Park. Ebird.org records no earlier observations of these birds at the Park and says that the last time they were observed anywhere along the West Arm of Kootenay Lake was four years ago in Nelson.

Gray-crowned Rosy Finches summer to our north and winter to our south, but they are rarely seen passing through the area around the Lake. It was fun to see them in the Park two days ago.

This is a portion of the flock of Gray-crowned Rosy Finches.

The birds did not alight, so the only pictures managed were of them flying. 

These finches have a delightful flying style called flap-bounding flight. (See, flap-bounding redpolls.) Here three birds are bounding, that is, they are coasting with folded wings. 

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Muskrat vs mallard

 

A muskrat is primarily a vegetarian, but occasionally it will eat other small mammals: snails, mussels, crustaceans, and small birds. But, would it tackle a large bird? The literature is unclear.

There is a pond where a few of us have watched interesting wildlife: turtles, various species of water birds, and, of course, muskrats. A few days ago, Shirley Smith sent me comments and pictures about a muskrat doing something rather odd there: It was harassing a mallard.

Two days later, I stopped by the pond and watched. Both animals were still at it. The muskrat would swim after the mallard. As the muskrat could swim slightly faster, it would close in on the mallard. When within a metre, the muskrat dived towards the mallard. Simultaneously, the mallard took to the air, flew perhaps a half-dozen metres and then alighted on the pond again. At this point the muskrat would start after the mallard again. Over and over the sequence repeated, and did so for as long as I was willing to watch.

Why was the muskrat doing this? Time and time again, it proved unable to catch the mallard. And why did the mallard always alight nearby and so invite another bothersome attack?

There is silliness to these behaviours.

Typically, a muskrat tries for a mouthful of salad (25 October 1916). But not this week.

A muskrat swam towards a male mallard. When close, the muskrat dived towards it and the mallard flew, but the mallard alighted nearby. At this point, the muskrat started after it again.

This time the muskrat is chasing the mallard towards the shore.

When within a metre, the muskrat again dived (the splash on the left) towards the mallard. Once more, the mallard took to the air. At first, I was confused by why the muskrat would dive upon approaching the mallard. Then it struck me. The speed of travelling over a water surface is effectively limited by what is known as the hull speed, a consequence of the waves the swimmer creates. However, the constraints of the hull speed do not apply underwater where an animal can travel much faster. So, by diving, the muskrat is doing the equivalent of a land-based predator that lunges towards its prey. The dive is thus evidence of the muskrat’s intent to attack. The mallard, knowing that the dive was the attacking lunge, took to the air to escape.

Strangely, the mallard would never fly far, but would alight nearby, thus inviting a repeat of the chasing game. Both animals seem remarkably slow learners. Advice to the obsessive-compulsive muskrat: Give it up and have some salad. Advice to slow-witted mallard: Just fly to the next pond; Do you think you can walk on water?

Posted in birds, mammals | 4 Comments