In cooperatively breeding species, ‘helpers’ provide care for other individuals’ offspring. Research into cooperative breeding, which initially asked the deceptively simple question ‘why?’, has continued to provide insights in behavioural ecology thanks to the opportunities for adaptation and coevolution that are generated in these unusual societies. I explore some of these potential adaptations in detail, mainly through studying a population of riflemen Acanthisitta chloris, which are passerine birds endemic to New Zealand. Previous work showed that riflemen are kin-based, facultative cooperative breeders. Most help is provided by adult birds, who have dispersed from their natal territory, but commute short distances to provision at the nests of relatives. Help is associated with enhanced recruitment of related offspring, and thus considered likely to confer indirect fitness benefits. These conclusions are substantiated by my results. Provisioning by helpers is a special case of parental investment, and in Chapter 2 I characterise investment by rifleman carers. I find that sealed-bid and conditional cooperation models are inappropriate to describe investment in riflemen, and discuss possible reasons for this. I also demonstrate the validity of provisioning rate as a measure of food delivery in riflemen. In the following two chapters I test the hypothesis that helping drives adaptive sex allocation in cooperative breeders, first using data from riflemen, and then across 26 bird species. Surprisingly, the hypothesis is not supported in either case. In chapters 5 and 6 I consider how riflemen recognise their relatives in order to direct help to them. I identify candidate vocal and chemical kinship cues and test the responses of provisioning riflemen to olfactory manipulations and call playback. My findings have implications for measuring parental investment in birds; show interesting discrepancies with evolutionary theory, and illustrate opportunities and challenges in sensory ecology. These themes are discussed in the final chapter.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:720074 |
| Date | January 2017 |
| Creators | Khwaja, Nyil |
| Contributors | Hatchwell, Ben |
| Publisher | University of Sheffield |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://etheses.whiterose.ac.uk/17848/ |
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