Why do Cormorants spread their wings?

Have you ever wondered why Cormorants spread their wings wide with a crucifixion-like posture , according of course a delight to watch with enough photography opportunities?

Well ! The most obvious reason of course is to dry their feathers after a swim or dive to catch their prey. However, there are some more explanations, with differing views and observations from experts. Number of theories have been propounded.

These include casting a shadow on the water to have a better vision to spot their next target, have a better balance on land, absorb heat to digest their food by exposing their bellies to the glow of the sun, to signal to other cormorants the availability of food or merely to rejoice their success in catching their target.

However, Dr Robin Sellers, a professional engineer and amateur ornithologist, having observed this posture of birds for years have negated most of these theories concluding that this posture is all about adapting to the wind to dry their feathers.

According to his findings published in published his findings in the journal Ardea, when the wind was up to, or more than, a strong breeze on the Beaufort scale (4 or more), cormorants spent, on average, 2.5 minutes standing like crucifixes. With hardly a flutter in the air (0 to 1 on the scale) they stood with their wings out for nearly five minutes and generally extended them further. The birds also faced the wind - more than half of them orienting within one compass point of its direction when conditions were virtually still, but more than 80 per cent when a good breeze got up. According to him, Cormorants tend to hold their wings out for longer in lower temperatures and when they had been under water for longer. Light rain reduced their fervour and heavy rain put a stop to any spreading at all.

If wing-spreading signalled feeding success, the birds would not do it when diving proved unsuccessful. And the theory of casting a shadow on the water only helps birds that adopt a stand-and-wait strategy - like herons - rather than those that dive as much as 10 metres down in murky water.

Dr Sellers calculated that between 30 and 90 grams of water have to be expelled from a cormorant's plumage after an average dive. It would need up to 222 kilojoules of body heat to evaporate it, an amount that could be sacrificed providing enough fish were caught to make up for the loss.

On the other hand, Dr David Gremillet of Neumunster Zoo in Germany says that wing- spreading may, after all, be a digestive aid. He found that cormorants that feed on cold fish held their wings out, often for 20 minutes and when fed on pre-warmed to cormorant body temperature hardly bothered to make a wing movement. His conclusion is that cormorants expose their bellies to absorb the sun's heat, a warm glow that aids the digestion.

Dr Chris Mead of the British Trust for Ornithology acknowledges that wing-drying and digestion aids may jointly explain the cormorant's striking stance. He says the heating up their food is the most important reason. Why else would cormorants be all black if it wasn't to absorb heat through their plumage?

Whatever may be the reason for their postures, Cormorant diving in the water, catching the fish and spreading their wings wide open with their black glistening bodies are a delight to watch.

The pictures are those of Little Cormorant were clicked in Thapli, Haryana, India during September, 2018