Parental effects and the adaptive generation of helpers in a cooperative bird

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It is often said that one day, whether we like it or not, we will turn into one of our parents. Research in both laboratory animals and humans, suggests that this is not only because of our genetic similarities with our parents, but because our early life experiences shape the way we look and behave in adulthood. However, two major uncertainties exist in the development of these patterns. First, do we simply resemble our parents because we share the same environment? Second, do parents actually shape our development through varying their levels of investment in us, and if so, when does this happen and for whose benefit is it? To answer these questions we must use an animal in which we can ethically move offspring around in a natural setting at different stages of their development and then measure their behaviour in adulthood. I will use a 50g Australian bird that lives, like humans, in family groups in which offspring are reared by a variable number of helpers in addition to parents. I have been studying ~90 breeding groups of the chestnut-crowned babbler in the arid zone of south-eastern Australia for the last 8 years. This species is perfect for the aims of this project because mothers vary tremendously in their investment in offspring, varying the timing and amount of investment in eggs, as well as the number and sex of competitors with which offspring will be reared. Similarly, mothers, fathers and helpers vary significantly in how much food they provide to offspring after hatching, with some providing almost nothing and others contributing the majority of it. Finally, the success of a group depends on how many helpers it has: the survival of offspring increases until group size reaches 8, after which there are no further increases. Because helpers are almost always offspring from previous years, a small group of babblers should try to produce helpers, whereas a large group should try to produce dispersers that go off to start a new babbler group. By moving offspring between groups of different sizes and at different stages of their development, I will provide an answer to the following questions. (1) To what degree do mothers, fathers and helpers try to create helpful versus selfish offspring, and do they all agree when this should be? (2) Do offspring ignore this 'arrangement' or benefit from it, or are they being manipulated to behave in a way dictated by their up-bringing? (3) If one's upbringing influences the way they look and behave in adulthood, when is this effect generated, is it by the mum's before hatching, is it when they receive food in the nest, or is it determined after they leave the nest and begin to fend for themselves? The answers to these questions will shed new light on how the upbringing of animals and humans shapes the way we look and behave in adulthood and help answer the long-standing questions of what makes a good mother, father and helper and who is it good for? If, from these results, we are able to predict the cooperative versus selfish tendencies of offspring given their development, we can begin to direct future studies in humans to ask whether there is a sensitive period during child development that shapes our behaviour in adulthood? When is it and what types of experiences is it most sensitive to?