A comparative study of postnatal growth and organ development in some species of birds.

An hypothesis has been formulated stating that the rate at which postnatal growth proceeds is at least partly determined by the distribution of growth between different organs. In order to test the hypothesis a series of studies of organ growth has been undertaken in some birds with widely varying growth rate capacities (geese, quail, turkeys, fieldfares and jackdaws). With regard to nidifugous birds the data show that the growth pattern of the goose, a species which has a high growth rate capacity, is characterized by a rapid early development of the digestive organs and the liver whereas that of the quail and the turkey, species which have low growth rate capacities, is characterized by a rapid early development of the pectorals and the feathers. The growth pattern of the nidicolous species, the fieldfare and the jackdaw which also show high growth rate capacities, is similar to that of the goose. These results are in close agreement with the hypothesis.