Family Conflicts over Parental Care in the Blue Tit, Cyanistes caerleus.

Dickens, Megan (2006) Family Conflicts over Parental Care in the Blue Tit, Cyanistes caerleus. PhD thesis, Lancaster University.

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Abstract

Current research into parental investment has focused on the influence of conflicts of interest between family members. This thesis examines how these conflicts affect parental investment into individual offspring within broods of blue tits, Cyanistes caeruleus. Experimental work mid-way through the nestling period investigates how nestlings solicit parental care through begging, and the food allocation rules of male and female parents. Nestling begging was found to relate to short-term hunger, but contrary to expectation, small nestlings did not beg more than their larger siblings (Chapter 3). Begging behaviour was also context dependent, as it was influenced by the sex of the provisioning adult and the reliability of the stimulus to beg (Chapters 3 & 4). Chapter 5 shows that parents allocate food to offspring in response to a composite of nestling begging and nestling position, and although this resulted in them allocating more food to hungry offspring, they also gave more food items to the largest nestlings in the brood. However, female parents allocated food in a more complex way than males, controlling for nestling size when responding to the position of nestlings in the nest cup. This may help to prevent the largest nestlings from completely controlling food distribution. Parents did not appear to be flexible in their provisioning rules, as even when they were provided with extra food they continued to allocate more food to larger offspring (Chapter 6). This may be to the parent's advantage, however, as it maintains size differences between offspring, allowing adaptive brood reduction should environmental conditions decline during the breeding attempt.