Many birds can navigate their way to Africa and back. Many create intricate nests. They're obviously very very clever. Maybe! Read on ! Gulls, geese and other ground-nesting birds have a stereotyped response to an egg that has rolled out of a nest. They reach over and roll it back in with the underside of their bill. Tinbergen and his students showed that gulls will do this not just to their own eggs but to hen's eggs and even wooden cylinders or cocoa tins discarded by campers. Baby Herring Gulls get their food by begging from their parents, by pecking at the red spot on the parent's bill, stimulating the parent to regurgitate some fish from its bulging crop. Tinbergen and a colleague showed that crude cardboard dummies of a parent's head are very effective in provoking begging behaviour from the young. All that is really necessary is a red spot. As far as the baby gull is concerned, its parent is a red spot. It may well see the rest of its parent, but that doesn't seem to be important. Adult Black-headed Gulls are conspicuous because of their dark face masks. Tinbergen's student, Robert Mash, investigated the importance of this to other adults by painting wooden dummy gull heads. Each head was stuck on the end of a wooden rod attached to electric motors in a box so that by remote control, Mash could raise or lower the head and turn it left or right. He would bury the box near a gull's nest and leave it with the head safely out of sight beneath the sand. Then, day after day, he would visit a blind near the nest and watch the gull's reaction to the dummy head when it was raised and turned this way or that. The birds responded to the head and its turning just as though it were a real gull,yet it it was only a mock-up on the end of a wooden rod, without any body, without legs or wings or tail, silent and without movement apart from an unlifelike robotic rotating and lowering. To a Black-headed Gull, it seems, a threatening neighbour is little more than a disembodied black face. No body, no wings, or anything else seems to be necessary. Turkey mothers are fierce protectors of their young from marauders like Weasels or scavenging rats. The rule of thumb a Turkey mother uses to recognize nest robbers is a dismayingly brusque one: In he vicinity of your nest, attack anything that moves, unless it makes a noise like a baby Turkey. Another Turkey savagely killed all her babies, the reason being woefully simple. She was deaf. Predators, as far as the Turkey's nervous system is concerned, are defined as moving objects that don't emit a baby's cry. These baby Turkeys , though they looked like baby Turkeys, moved like baby Turkeys, and ran trustingly to their mother like baby Turkeys, they fell victim to the mother's restricted definition of a "predator." She was protecting her own children against themselves, and she massacred them all. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ All very sad, but it seems that many creatures have a rigid internal set of algorithms which, in certain circumstances, lead to unwanted and unfortunate "errors." But I assume that most of the time they "work." And that's the best they can do. Strangely, I can't find a single video of a " bird rolling an egg into the nest" ... or even just "rolling an egg." (!!) So ,instead, we'll have some music .... Zwei Fragen .....
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AuthorThat's the author up there ... I was young and sprightly then. Archives
October 2022
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