The biology of the New Zealand Falcon (Falco Novaeseelandlae Gmelin 1788)

This study was undertaken for two reasons. The first was that the New Zealand Falcon was largely unstudied, and research on its basic biology would provide a base-line for further work. The second was that the topic covered a number of disciplines which meant that, as an academic exercise, the scope was broad rather than narrowly specialised. The easiest projects to write up are those in which there are so many data that the figures almost speak for themselves or those in which there are so few data that one is free to speculate. Unfortunately most of the chapters in this study fall into a middle category in which the samples are small and statistical probabilities are marginal. Also, in trying to maintain a broad approach I have been compelled to sacrifice depth and so each chapter tends to reveal more questions than it answers. While writing, I have been acutely aware of the differences between potential readers. Overseas raptor specialists on the one hand may know little about New Zealand's avifauna and ecology, and New Zealand biologists, familiar with New Zealand, may know little about the ways of raptors. Therefore a short glossary of terms has been included. Briefly, the study has set out to answer a few straightforward questions such as 'Is the Falcon monotypic?', 'What is it related to?', 'Why are the females larger?', 'What do they eat?', 'How do they hunt?', 'How big is their range?', 'What is their breeding biology?', 'Will they breed in captivity?', 'What do they die of?', 'Where are they?', 'How many are there?'. Some of these questions, such as the diet, can be answered with some precision; others, such as the problem of sexual dimorphism, can only be answered in a general way. Because I was strongly advised at the start of this project that a study of the New Zealand Falcon was not feasible, I started a subsidiary project on the Australasian Harrier (Circus approximans). This was soon abandoned and although the results have been published (Fox 1977b) they have not been included in this thesis. Certain portions of this thesis, such as 'Rangle' (Chapter 5.15 -5.19), 'Diet values and food consumption' (5.8-5.11) and 'The shape of nesting territories' (8.9) have already been published or are in press, but for the sake of continuity have been kept as an integral part of the thesis. To a certain extent I have been handicapped by lack of raptor specialists in New Zealand with whom I could discuss my work. Another aspect of New Zealand's isolation is the difficulty in obtaining certain literature. Thus Chapter Four has suffered from my not having access to Noel Snyder's and James Wiley's recent monograph on Sexual Dimorphism. The compensation for this isolation has been the' privilege of working on such a magnificent, and unstudied, raptor