Exploring Kootenay Lake

Four species seen during a walk.

Usually found flitting about bushes, the Grey Catbird is named for its cat-like call.

This is a robin. The speckled breast reveals it to be a juvenile.

Two male Barrow’s Goldeneye Ducks seem to synchronize the examination of an intruder.

The Red-naped Sapsucker is a woodpecker that carves horizontal lines of holes in the bark of trees. Later, it returns to collect the sap and insects attracted to it. Earlier holes can be seen as a line of scars on the tree trunk.

This is the season to see chicks. This is also the season to notice a rather odd behavioural difference between birds that show sexual dimorphism and those that don’t.

A species with sexual dimorphism exhibits different characteristics beyond the differences in their sexual organs. Indeed, the male and female often look markedly different. In a species with sexual monomorphism the male and female are difficult to distinguish.

Some birds are monomorphic; some are dimorphic. Among dimorphic species, it is usually the male that has the brighter and fancier plumage, but now and then it is the other way around (kingfisher). Sexual differences in appearance seem to have evolved as a result of the mate selection by females.

Curiously, the visual difference is accompanied by a behaviour difference in parenting:

The lesser the similarity in appearance, the lesser the involvement in breeding duties by the more colourful bird (usually, but not always, the male). The greater the similarity in appearance, the greater the equality in breeding duties.

I was reminded of this yesterday while watching an impressive group of Wood Duck chicks and someone in the group wondered why the chicks weren’t accompanied by both parents. The short answer is the Wood Duck is sexually dimorphic.

The first picture shows the female (left) and male (right) Wood Duck (appropriately) perched in a tree. They are strikingly different in appearance (March 28, 2016).

Consequently, during yesterday’s observation of thirteen Wood Duck chicks, we expect to see only the mother with them. (The most Wood Duck chicks I had previously seen were three.)

Similarly, the (sexually dimorphic) Common Mergansers seen five days ago only shows mommy with the chicks.

Contrastingly, Canada Geese parents look much the same, and both tend chicks (May 31, 2011).

The similarity of Osprey parents implies that both have parental duties (July 19, 2013).

Canada gets only four hummingbirds. Around the Lake, we get three, and occasionally all four.

Earlier, I posted images of the Calliope and Rufous. Today’s picture shows the third: a Black-chinned Hummingbird. It has been hanging around for a few days, but today, I managed a picture.

A Black-chinned Hummingbird shows purple iridescence at the base of its gorget.

A standing person who faints, falls over. Maintaining one’s balance requires constant muscular adjustments. Maintaining one’s balance while standing on one leg is even more difficult.

Consequently, many people have marvelled at the sight of a heron napping as it stands on one foot. Insights into such feats were recently supplied by a study of flamingoes. The authors found that balance aids built into the bird’s basic anatomy allow for a one-legged stance that demands little muscular effort. This stance is so stable that a bird sways less to keep itself upright when it appears to be dozing than when it’s alert with eyes open. Indeed, even a dead bird can be prompted to balance on one foot, when it cannot be made to balance on two.

It appears that some birds have a mechanism humans lack for stably balancing on a single leg.

A week ago, a heron on a piling was standing on one leg. It is a common sight and, until the recent paper on the subject, seemed inexplicable (2017/05/18).

Normally when a heron is hunting, it is positioned on two feet (2013/07/19).

A heron in a tree during really cold weather, is seen to balance on one foot (2012/11/20).

However, the frequent sight of a heron posed on a single leg always seems odd (2013/12/02).

It has been seen so frequently that it must be a stable position for the bird (2006/10/14).

Indeed, even this view of (what appears to be a contortionist) must be normal (2009/10/15).