after the young woodpecker's three sisters reached the outside world, the father and mother were kept busy hunting food for them, and they were alone much of the time. it was not long before they knew their parents' voices, although, once in a while, before they got their eyes open, they mistook the call of the tree frog below for that of the woodpeckers. and this was not strange, for each says, "ker-r-ruck!