DIVE! DIVE! DIVE!
If you’re as old as me you might remember an old TV advertisement for bread. I can’t remember the brand that commissioned it but I do remember the advert, which must say something about the effectiveness of that particular campaign. It featured some young mothers and their children feeding ducks at their local pond. They were throwing bread to the ducks which we now know as bad for their digestion. I’d ask you all to feed them vegetables or seed instead but this advert was quite some time ago so we’ll let them plead ignorance, just this once.
In the advert, the first child threw some of the advertiser’s chosen bread to the ducks and they happily gobbled it up, quacking and squabbling in the way that hungry ducks do when supplied with free human-food. Then the second child tossed his chunks of bread to the same group of Mallards. He had not chosen the loaf from the people who had paid for the advert, so his product was obviously going to appear inferior to his little friends’. A duck greedily snarfed his offering… and promptly sank without trace, quacking in a bubblicious manner as it plummeted into the murky depths.
The morals of this story are twofold. One; never eat bread from a lesser baker as it will lie heavily in your stomach. The chosen loaf was obviously much lighter and by extension, better for you. Apparently. The second thing to take away from this advert is that you should never trust anything you see on your tellybox, however funny it might seem. Ducks don’t sink. Not accidentally anyhow. Some of them can even deliberately dive under the water but that’s through thousands of years of evolution, not related to which bakery product they have for breakfast.
Probably the most common diving ducks that you’ll encounter at Old Moor are Pochard, Goldeneye and, my favourites, the beautiful Tufted Duck. Watching them ‘swim’ in clear water, releasing a stream of bubbles as they hunt for food amongst the weeds, is one of life’s purest delights. No submarine commander ever directed his craft so perfectly.
Unlike most birds, many diving ducks have an almost total lack of air within their skull cavities and, to a lesser extent, around their bodies in general. This dramatically decreases their buoyancy, meaning that they can dive beneath the surface with relative ease. This lack of air around the brain also removes the problems associated with water pressure. All that up and down, change in density malarkey would cause you and me sickness, headaches and worse, but these little ducks revel in it. Each to their own, I guess, but I prefer my food to be hotter and drier than theirs.
All birds trap air within their feathers for warmth. This also acts as a floatation device if the bird in question is supposed to be at home in an aquatic environment. Even if it’s meant to spend all its life in the air and on land, just about every bird is able to swim short distances to safety in an emergency. Of course it will eventually become waterlogged (with unfortunately predictable results) unless it has some other kind of waterproofing mechanism and most water birds have developed just the thing.
If you want to be properly waterproof though you need a uropygial gland. This is a special gland at the base of a bird’s tail and is especially developed in waterbirds. It produces preening oil, the special secretion that they rub on their feathers to build up (among other things) their water-resistant properties. Look at the way that Swans rub their heads around their bodies for a great example of how birds spread this oil. I could do with some for my so-called waterproof jacket.
Cormorants and Shags are exceptions though. They have very little waterproof oils and so are at a very real threat of becoming waterlogged and drowning. This is why you often see them with their wings outstretched, ‘jazz hands’ style, drying out after every fishing session before they can even think about going below the surface again. You’d think that this would be a serious problem for a bird whose diet is made up almost exclusively of seafood but there is an upside to it. The lack of air in their feathers means that they can dive deeper and for longer, increasing their chances of snagging a juicy fish.
Isn’t it magnificent how every part of a successful creature has developed perfectly to perform the task for which it’s needed. And of course it’s an ongoing process. Many waterbirds’ digestive systems have become more resistant to the poisons that we humans have introduced into our waterways, especially in the last 200 years or so. A duck from before the Industrial Age wouldn’t be able to survive on the diet which our current birds take for granted. ‘Adapt or die’, is one way of looking at it. I prefer the phrase ‘Nature will find a way’. Water makes up around 71% of our planet and the RSPB and others are encouraging our governments and water companies to do what they can to make the wetter parts of our world as clean and habitable as possible. Let’s hope they succeed.
One of our older sloans at the RSPB is “Let’s Give Nature a Home”.
I hope that those lovely diving ducks have a clean home for generations to come.
Volunteer Shaun welcomes visitors to RSPB Old Moor. He also writes a weekly blog about life at the reserve titled, "View From the Shed". He usually wears a big hat.