REED WARBLER
efforts to obtain the food. We may then almost say that the whole process is a mechanical one; the parents know not, neither could they possibly recognise that one individual is stronger and thus would demand more food than another, still less could they possibly comprehend the difference being a sexual one, if indeed it were so. Their behaviour is solely determined by the organic response of the young. It is not necessary for them to consider—nor do I believe that they would be capable of doing so—a matter so abstruse as supplying food in rotation; it is not even necessary for them to remember to which individual they delivered the last supply of food, although it is not improbable that they sometimes do so. After watching the routine of different pairs under similar conditions, I can see no reason to believe that they in any way profit by experience. How far their whole behaviour may be congenital, or how far traditional, it is difficult to say. We cannot assume that a young male and a young female never mate together, for if we consider the proportion of young birds to old, we can see that cases must frequently arise in which a pair are compelled to build a nest and rear young antecedent to experience. In some of the cases which I have from time to time studied, there is a strong probability that the actors have been performing for the first time; and, if so, they have taken their part in this complex piece of machinery as skilfully as the adults. It is true that we could place their whole behaviour on a level with our own; we could discern a motive in their supplying one individual more than another with food, could regard the removal of the fæces as an act of conscious deliberation, could indeed see all their actions in the highest light possible and thus attribute to them reasoning powers similar to our own; but of what use would such a method be? Conclusions thus reached would retard rather than facilitate our knowledge of their subjective states, and it might truthfully be said that they would never even enter the domain of science.
I have in the case of this species also carried out a series
51
