Why bats are nocturnal animals (082)

Did you know that a long long time ago the flying space for birds was restricted because of the sky being very close to the earth? The birds’ combined efforts enabled them to change this. But this process did not go smoothly and the bats played an important though hardly nice role in this venture. As you can imagine, there were consequences which you can read about in this old tale.

When the earth was still fairly new, the birds had very little space to fly about in. The sky hung only about a hundred metres above the earth and in that narrow airstrip between heaven and earth it was always extremely busy. The large birds of prey were forced to fly on the same level as the sparrows, for instance, which resulted in the high and low flyers continually getting in each other’s way. The vulture, in particular, was more than just fed: he kept on banging his head against the underside of the sky which over time resulted in his having a bald head.
He filed his complaint with the eagle, the king of the birds. “If the sky were a bit higher up,” as the vulture put it, “we would all have more space to fly around in. Large birds can then fly higher and small ones will also enjoy more flying space. I’m not just thinking about my own best interests,” he said, pointing to his bald head.
“Ask the opinion of the geese, godwits, curlews and all the other migratory birds. Do you have any idea how many traffic accident victims there are every day as a result of this chaotic air traffic?”
“The council will consider the matter in due course,” responded the eagle majestically.
“Aha. Yes, I can imagine.,” commented the vulture sarcastically. “Meanwhile I have already thought up a plan myself: what if all the birds in the world were to fly up together at the same time and push the sky up a bit higher? There are millions and millions of us, it must be possible? As our king, you can oblige everyone to join in.”
King Eagle took due note of this, summoned the representatives of the different birds and revealed “his” plan to them. It was the first time the birds had put their heads together to discuss a problem. Large and small alike, they quickly came to a joint conclusion: “We would never have thought of that!,” was a commonly heard exclamation.
And that is why one day people were shocked and amazed to see how the sun was completely eclipsed by an enormous swarm of birds which flew up as one body and began to push the sky upwards with all their might. Only to drop back down again a quarter of an hour later, exhausted and disappointed. The sky had actually moved slightly, but in the end it hadn’t shifted a millimetre upwards. A few days later there was a new attempt. And another. After the third failed attempt the large, broad-winged eagle circled above the battlefield of exhausted birds. He could not figure out why the plan would not work. Is everyone actually doing their bit, he wondered and scanned the dejected group of birds with his sharp eyes. Suddenly his voice thundered: “Where are the bats? I’m missing the bats!”
All the birds looked around and, indeed, there wasn’t a bat in sight! They were all resting half asleep in the warm sunshine. Widespread outrage. All the bats were forced to join in in a new attempt. And yes, the millions of bats provided just that extra bit of force that was needed. Creaking, the sky broke free of its clamps and shot several kilometres upwards.
For days on end the exhausted birds remained in a state of collapse in the fields and trees, recovering from their exertion. They were thrilled though that they had finally done it. However, they were still furious with those lazy bats whose assistance first time round would have meant immediate success.
When everybody had recovered, King Eagle summoned the bats and roared at them: “It was already clear to me that you never truly felt involved with us birds. But we have pushed ourselves to the limit to enable you to enjoy more air space. A bit of solidarity was the least we could expect! But no, on our first, second and third attempt you failed to do your duty. You lazy anti-social so-and-sos! From now on you will be nocturnal creatures, so that we, the real birds, never have to set eyes on you again.”
And so it came to be – to this very day.

Because the sky had shot several kilometres upwards, the different types of birds got their own area in the airspace: chickens close to the ground; ducks, robins and blackbirds ten metres or thereabouts above them; the magpies, crows and thrushes above that; and ever since this shift birds of prey and seagulls have been able to observe the world from great heights. And what about bats? They still fly round at the same height as then, the height of houses and trees, and only come out after dark.

How high do birds fly? Lower than you think. Generally, most birds do not go much above 150m and the small ones like robins and blackbirds generally fly no higher than 30 metres. Birds of prey fly higher, as they need the overview. During their spring and autumn migration birds fly higher to make use of the thermals. Others prefer to fly in cooler air segments to reduce the loss of body fluids. Vogelbescherming Nederland, the Dutch Bird Protection Society, has carried out a survey: when migrating geese fly at a height of 6,5 km.; dunlins and redknots at 7 km.; godwits and curlews at 6 km.; thrushes at 3 km.; common kestrels and wood pigeons at 2100 metres; swifts and peewits at 1800 metres. Most songbirds migrate at heights of up to 1500 km.

The bat is a flying mammal. The largest species in our area is the greater mouse-eared bat with a wingspan of approximately 40 cm. The common pipistrelle bat, the most commonly found species here, is half the size and weighs as much as three sugar lumps. Bats can live to be 20 years old; the oldest recorded bat is one of 41-years-old.
A bat has wings on both sides wings, from its fingers to its tail and feet included. The wings are to fly with and also act as a net to catch insects with during flight. Daubenton’s bats use their feet to snatch insects out of the water. Being nocturnal, the bat “lives” by using its ears for echo location. This enables the bat to identify its surroundings and prey through the deflection of signals.
Bats prefer to rest in the daytime in cavity walls, the attics of buildings or in hollow trees. In one single night they eat two-thirds of their body weight; about 3,000 insects per night! Because more and more houses and buildings are better insulated, many breeding and resting places have disappeared and the bat population is decreasing so that more insects are surviving. That is true of our region, even if it is less of a problem in Belgium than in The Netherlands because there are many spaces in the rocks of the Ardennes. Meanwhile in the US bat boxes are being put up in orchards specially to encourage bats to hunt insects.

Post Author
Els Baars