RESEARCH INTERESTS

I could best be described as a behavioural ecologist. My emphasis is on fieldexperiments, typically on biparental and cooperatively-breeding birds, althoughI work quite a bit on other taxa and on theory as well. A common theme in muchof my research is the evolution of cooperative behaviours within the context ofindividual conflicts of interest, and how these are resolved via suchmechanisms as honest signalling or behavioural negotiation. Major avenues ofinterest include:

Cooperative dynamics in parental care (Refs 3-13, 16-17, 21-27, 30-31,41-43, 51, 58)

Evolutionary game theorypredicts that in mutualistic interactions collaborators will incompletelycompensate for each others' shortfall in effort. We have confirmed thisexperimentally by handicapping one member of a pair of parents provisioningyoung, by enhancing the effort of key members in cooperatively-breeding groups,and by detailing the effects of variation in both brood size and number ofcollaborators. Incomplete compensation lowers collective fitness and thus actsto dissuade collaborators from “cheating” and withdrawing effort. Socialmonogamy in the majority of bird species and many group cooperative behaviours maytherefore be maintained via this subtle bargaining mechanism. We havedemonstrated that these compensation reactions persist within sex-specificroles in chick-feeding and predator mobbing, and elsewhere in cooperative anti-predatorsentinel behaviour. Some of my current experimental work in this areainvestigates the dynamics of biparental incubation and brooding schedules.

Cooperativeeffort also depends upon kin selection and the benefits arising from thegenetic relatedness between collaborators. I have been involved in experimentsand theoretical developments concerning certainty of paternity and parentalcare, as well as the effect of relatedness on collaborative effort withincooperative groups of birds.

Central place foraging and beyond (Refs 3-6, 7-10,15-18, 21-24, 26-27, 30, 34, 40, 53)

Manipulating parentalprovisioning effort requires detailed consideration of optimality, energetics,nutritional currencies and variance sensitivity within central place foragingstrategies. As a result, I have been involved in some detailed foragingexperiments on parent birds, and have also applied these ideas to ants colonies(i.e. viewed as ‘superorganisms'). One current extension here involves lifehistory trade-off between self- vs chick-feeding in short-term parental caredecisions, within which we have initiated the first exploration of diurnalvariation in parental body mass in birds using both stochastic dynamic modelsand field experiments.

Altruism as a signal & the evolution of cooperation (Refs21, 23-25, 28, 30-33, 41-43, 49, 53, 55-57)

This novel extension ofZahavi's handicap principle has received much recent theoretical attention inthe form of indirect reciprocity, competitive altruism and social prestige. However,there have been few empirical tests of altruism as a signal outside my ownwork. Having successfully investigated this idea in a range of cooperativebehaviours in Arabian babblers, we are now in a position to perform criticaltests regarding helping as a signal in mate choice in the cooperativelybreeding bell miner in Australia. Signalling using altruism also plays a partin my collaborative work on recruitment to food sources within raven roosts,and predator inspection behaviour in fish and the evolution of ‘personalities'.This project has involved various recent theoretical developments in thisfield, involving reproductive skew in cooperative breeding, handicap signallingand hopefully some negotiation models of cooperation.

Begging as an honest signal (Refs 5, 14, 19, 24, 29-30, 37-39, 44, 46-48)

Interest in begging as themechanism behind cooperative nestling care was increased in the early 1990s byhandicap models of begging as an honest signal, which provide a signallingresolution to parent-offspring conflict. Our experimental manipulations ofchick nutrition and sibling competition confirmed general predictions fromthese models, but little evidence exists for the expected substantial energeticor predation costs of begging. Recent studies suggest that excessive beggingeffort results in restricted growth, hinting at some hidden physiological costto begging. I am working on the idea that this cost lies in the reduction ofdigestive efficiency, probably as a result of begging necessitating a shift ofblood flow away from the gut towards the muscles and the brain. Our recent dataconcerning temporal patterns in begging effort are consistent with thissuggestion, and we are now working to confirm this trade-off using controlledassessments of nestling digestive efficiency whilst manipulating begging effortand frequency.

This recentextension of my research into the digestive physiology of growing nestlings hasintroduced a series of new and interesting problems. Developing nestlings caninvest their resources into growing a more efficient gut (to get more out offuture food), investing in somatic growth (and so fitness upon fledging), orput more effort into competitive begging (thereby increasing future foodintake). The optimum developmental trajectory will involve age-specifictrade-offs between these forms of investment in order to maximise fitness uponfledging. Modelling this problem using multiple state-dependent stochasticdynamic models should provide links with our recent experimental work intorelated issues concerning learning by individual nestlings based upon theircompetitive experience, the timing and limitation of skeletal growth, andpre-fledging requirements regarding mass recession and wing growth.

Localised population declines and effects of global warming in piedflycatchers (Refs 58)

Thisnew project quantifies and attempts to explain dramatic recent population declinesrecorded in pied flycatcher nestbox studies across Europe, probably due toreduced recruitment of first year birds. Recent advancements in the peak offood availability during offspring rearing have been caused by global warming, anddifferent populations appear to respond to differing degrees by advancinglay-dates. We think that these population differences in response to globalwarming may explain these UK-wide and Europe-wide changes in the density anddistribution, and perhaps link these changes to population differences inmigration and over-wintering sites.