Black Swans

- posted by Rosey Pounsett

Some fun facts about Black Swans:

A group of swans on the ground is called a bank.

A group of swans in the air is called a wedge.

The Latin name for the Black Swan - Cygnus atratus - translated equates to "swan clothed in black"

The Black Swan figures largely in Aboriginal mythology, and you can read about some of them on the internet.

In 1697 when Europeans first heard reports that Dutch sailors had seen black swans, they could not believe it. Every swan that had ever been seen previously had been white, so they assumed all swans were white. When later explorers confirmed the reports, they were forced to admit that their assumption was wrong. Modern philosophers have used this as an historic example of the dangers of induction.

It is normal for swans to swim with one leg tucked onto their back. It has been suggested that this behaviour may play a part in helping to regulate the body temperature of the bird. The legs and feet are the only part of the swan not to have feathers, so the blood vessels are in closer contact with the air. The large surface area of the webbed foot makes it easier for heat to be transferred from  the body to the air, cooling the swan. This heat exchange could also work the other way, with the feet absorbing heat from the air to warm the bird.

Basic Information:

Description - An adult Black Swan is almost entirely black, with the exception of the broad white wing tips which are visible in flight. The bill is a deep orange-red, paler at the tip with a distinct white band near the end.The young cygnets are a fluffy grey, and they keep the grey colour as they grow. Males are larger than females, but otherwise they look they same.

Feeding - The Black Swan is a vegetarian. Their food consists of algae and weeds, which the bird obtains by plunging its long neck into the water up to 1 metre deep. Occasionally birds will graze on land, but they are clumsy walkers.

Breeding - Birds normally pair for life, with both adults raising one brood per season. The eggs are laid in a nest made of reeds and grasses either on a small island or floating in deeper water. The chicks are able to swim and feed themselves as soon as they hatch. The average clutch is five or six eggs, and as with most waterbirds, many of these are taken by predators such as rats, ravens, gulls, and Swamp Harriers. After breeding, most, though not all, Black Swans undergo a moult, during which they lose all their flight feathers and therefore cannot fly for a time. This often coincides with the period before the cygnets are fledged and when they are therefore wholly dependant on their parents - a convenient arrangement for both.

Handfeeding Black Swans - The practice of feeding bread and other food scraps does these birds more harm than good. Swans may become dependant on humans to feed them and lose their natural instincts to forage for food. Adult birds may fail to teach juveniles how to find natural foods. Birds that are conditioned to being fed by humans have a decreased wariness of predators and this potentially makes them more vulnerable to dogs, cats and foxes. The birds are also more likely to become aggressive towards humans, and may become a danger to children especially.

References:

The Waterbirds of Australia

www.rspb.org.uk

www.dpaw.wa.gov.au (Black Swan Fact Sheet)

 

 

Comments

Post a Comment

Captcha Image