Camouflage and Concealment

If one wants to be a birder or bird photographer, one must spot birds in the wild. While it is easy to spot moving birds, it is harder to find sitting ones. The difficulty increases when the bird does not stand out -  on a bare branch, for example - but blends in with its surroundings.

One winter day in Purbachol I was looking for birds in a field covered with dry yellow grass. Among the grass were some weeds that grew waist-high. I saw the flicker of a tail in the weeds as a bird quickly dropped to the ground. I searched for it by scanning the ground in front and noticed a brief movement under the layers of grass. Then the movement stopped. I stared hard but discerned nothing and was beginning to think my eyes had tricked me. Then it moved again. Now I spotted it, a Bengal bush lark, with colours that matched the grass. It was only a few feet from me but very well-concealed.

For many birds and animals, colouration plays a large role in their quest for survival. It is useful in three ways. The first is concealment: colours can camouflage the creature so it avoids being seen by predators or by prey. The second is advertisement related to mating and breeding: colours attract the opposite sex. The third reason is disguise, for example, when a prey fools a predator by making it believe that the prey is something else (that the predator should avoid.)

Most people, at one time or another, had some encounter with concealed or camouflaged creatures: perhaps a grasshopper on grass, or a frog on the ground that suddenly comes to life when one comes close. For me the most frustrating experiences are camouflaged birds explode out of hiding when I get close, leaving no chance of a photograph. In particular, snipes in fields and bitterns in wetlands are master of this.

So how does concealment actually work? When an animal blends into its background and becomes virtually invisible, we tend to think that concealment is a result of its colours matching the background. However, it is more involved and a mechanism called countershading often comes into play. The colours of the animal actually counteract the effects of light and shadows, creating a flat appearance for the animal. So the top parts of the animal, where the light falls, are darker whereas the bottom is lighter. Hence the light belly colour of many birds and animals.

Another type of concealment is called disruptive colouration.  An example is the zebra whose bold pattern effectively breaks up its outline – particularly in a herd situation – to an attacking predator.

Some of the fundamental ideas of colouration and concealment were first articulated by Abbott Thayer, an American naturalist. Despite these contributions, Thayer got into trouble later in life when he argued that the pink colour of flamingos makes them invisible when flying into the sunrise or sunset, thus saving them from predators. While the colouration of animals is, like everything else in nature, a complex subject, Thayer tried to explain it with a grand theory that all colouration is for concealment.

Thayer's pronouncements irked (American president) Teddy Roosevelt – an avid naturalist and big game hunter - so much that he took time out from a presidential election to write a 100-page journal paper demolishing Thayer's theory. Animal camouflage and concealment remains a complex topic not easily explained by one theory.

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