Common Cuckoo

  I have already introduced a insect, a plant as a interesting specie although I was not sure if you guys were interested in them or not.  Anyway, because I want to share something interesting or mysterious with you guys, I'm going to write about that kind of thing again.  Today's theme is "Common Cuckoo"(Cuculus Canorus), which is a kind of birds.


  The cuckoo is seen in Eurasian Continent and Africa Continent.  Sometimes we can see it in Japan in May.  This bird is known for peaceful birds because their songs sound humorous, amiable, and cute.  However, as a matter of fact, they have a horrible custom.  The common cuckoo is a brood parasite, which lays its eggs in the nests of other bird species.  It means they make other birds bring up their child!!  The victims are mostly the Reed Warblers, which is also kind of birds, and much smaller than Cuckoo.  When the hen cuckoo flies down to the Reed Warblers' nest, she pushes one Reed Warbler egg out of the nest, and lays an egg and flies off.  The whole process takes only about 10 seconds.  She kills a Reed Warbler egg in order to make Reed Warbler bring up only her child.  Sometimes, the hen cuckoo fails to kill other eggs, and then the eggs safely hatch; however, when Cuckoo's egg hatches, the Cuckoo chick pushes other eggs out of the nest.  Eventually, if birds are invaded by Cuckoo, their own eggs can never survive.  At 14 days old, the Cuckoo chicks are about three times the size of the adult Reed Warblers.

  We wonder why Reed Warblers don't notice the fact the chick is actually a wrong bird.  The size of Cuckoo chicks is totally different from Reed Warblers' chicks. It's obvious!!  But, in fact, they know they are raising other birds' chicks.  They have known it since their own children are killed by the chick.  Even if Reed Warblers know the truth, they can't help raising the Cuckoo chick, which is only child remained in their nest.  This is kind of an instinct that animals have.  Although they are aware of something wrong, they keep feeding the chick until the chick is grown up and leaves the nest.


  Do you think Cuckoo is cruel?  Yes, for victims such as Reed Warblers, this custom is fairly terrible.  But why do Cuckoos do this?  Why don't they bring up their children by themselves?  Are they just lazy?  Actually, not.  They have a reason that they have to do that.  The reason is their body temperature is not enough high to warm eggs up.  Their body temperature is easy to change, so they can't warm their eggs up by themselves.  I think Cuckoos were thinking over about this serious problem, and they came up with being a brood parasite in order to survive.  When they get pregnant, they always have to find a suitable nest.  Even if they can find it, they have to say good bye to their eggs.  Their child can never see the true parent.  The chick thinks the bird who feed him is a parent, and the hen Cuckoo realize it.  Although she loves her child, she can't meet her child as a parent.  This is a tragedy not only for Reed Warblers, but also Cuckoos.