Bird Behavior Inheritance and Imitation

We have now reached the stage when the broods of young birds, safely reared and fully fledged, have at last left the nest and are scattered about the surrounding herbage. What happens to the young from this time on, and what their relations are with the parent birds, depends largely on whether a second brood is to be reared. If a second brood is embarked upon, the hen bird often commences the construction of the second nest (unless she uses the same nest twice, which is rare), immediately the young from the first have left it, and in such cases, the further feeding of the first brood devolves upon the male, or possibly the young may be left to fend more or less for themselves. But if only one brood is reared, it is usual for the birds to keep together as a family party at least up to the time that the adult birds go into the summer months, and sometimes right through to the autumn. The period immediately following the quitting of the nest is the one most fraught with danger for the young birds, but it is also the one in which they have to acquire the majority of those accomplishments which do not come under the rather vague term of " instinctive actions." Thus whilst the ability to build a nest is an entirely instinctive accomplishment—since every bird can build its own specialized nest without ever being shown how to do so—certain other actions such as pecking-up food and ability to sing the normal song of the species, are not invariably accomplishments with which the young are born, and which do not need to be acquired. A great deal of the " education " of the young proceeds from a very strong instinct in young birds to follow their parents, and imitate their actions. The " following-instinct " has recently been shown to be associated in a very remarkable manner with the first living or moving object with which the young bird has visual contact after the moment of hatching, especially if that object is capable of making sounds similar to those normally used by the parent birds at hatching time. This remarkable fact which has been called " imprinting " (because, it seems, a visual pattern of the first living object seen by the newly hatched chick is strongly and indelibly imprinted on its consciousness), has been demonstrated in the following way. The eggs of a grey-lag goose were taken and hatched out in an incubator. At the moment when they were about to hatch, the scientist who was carrying out the experiment stood in front of the eggs, and remained there until all the chicks were hatched, and were able to see clearly the objects in the world around them. During this time he moved about and imitated the noises normally used by the hen goose as the young hatch. He found that from that moment onwards the young goslings regarded him completely as their parent ; they insisted on following him wherever he went, even so far as swimming in the river with him. Other adult geese, even those with broods, were completely ignored. This is no isolated case, for further experiments by others have demonstrated this remarkable facility on the part of young birds of indelibly registering the first being seen as the one to be regarded as parent, and hence to be associated with thereafter. Thus a South American bittern, bred in captivity in the Amsterdam Zoological gardens, adopted the man who was tending it as its natural parent, and for ever after so regarded him. Although this bittern, a male, grew up and actually mated naturally to a hen bittern, it would immediately leave the hen and come to the man, if he appeared, and even at times drive away the hen bird from its nest, and try to make the keeper assume her place upon it ! Similarly, a Muscovy drake which was hatched out by a grey lag goose and reared by that goose, always attempted to copulate with grey lag geese and not with Muscovy ducks, even after it had been separated from the grey lags for a considerable time. Associated with this imprinted image in the young bird's consciousness, is the urge to follow the object associated with that image, and to imitate in numerous ways its actions. Thus young chicks, especially those of nidifugous birds, follow their parents about and imitate their actions such as pecking up food, bathing in dust (partridges), diving under water (diving ducks and grebes) and so on.