Current research

Thanks for checking out my research page. I study animal behaviour from an evolutionary perspective. I have many research interests (see below) most of which revolve around insects and birds.

Research Interests

IMG_0575There are many ways of studying animal behaviour which range from understanding the mechanisms that lead to the expression of behaviour through to understanding the fitness benefits of expressing a behaviour. I am an evolutionary biologist who studies animal behaviour mainly from the mechanistic perspective. Therefore, my research concentrates on understanding the relationships between animals’ behaviour and their physiology and environment. I will briefly outline the main research areas in which I am currently active.

State-based behavioural strategies: the expression of certain behaviours may be energetically dependent. Therefore, understanding how animals regulate their energetic reserves may help us understand how they behave. I have studied avian foraging behaviour, dawn chorus display, and incubation behaviour from a state-based approach. I continue to study the links between animal energetic state, condition, behaviour, and animals’ wider phenotypic quality.

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This graph shows the number of mealworms that South Island robins cached at different times of the day (1 = dawn, 5 = dusk) in relation to differences in the ambient temperature. Early in the day, birds cached more mealworms whereas later in the day, they ate more as they gained mass for their nightly fast. They also cached fewer mealworms at cooler temperatures which reflects that their energy demands were higher at cooler temperatures. Taken from Barnett & Emura (2014). Emu–Austral Ornithology.

Animal communication: Animal communication is the transfer of information between a sender and receiver. Normally, when one animal (the sender) communicates with another animal (the receiver), it is attempting to manipulate the behaviour of the receiver. Some of the main reasons animals might try to manipulate others are when they are trying to find a mate, when they are fighting, and when they perceive danger. I have studied avian dawn chorus displays, singing behaviour, and aggressive displays. Currently, I am working on projects that examine the relation between parental alarm calling and offspring begging and the links between parental behaviour and offspring begging in birds.

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House wrens rates of singing (left) and wing quivering (right) significantly predict the likelihood of attack towards a territorial intruder. This shows that aggressive displays in house wrens are composed of multiple components that predict attack. Taken from Barnett et al. (2014). J. Field Ornithol.

The adaptive significance of personality: Animals are said to have personalities when individuals behave consistently in one way which may be different from other individuals. Animal personalities have now been documented in over 60 species of animals. This creates problems for the study of animal behaviour because personality traits reduce the amount of behavioural variability within individuals. Therefore, one of the main foci of current research is to establish how different animal personalities benefit animals. I have studied the relations between different behavioural traits (e.g., aggressiveness and boldness) and animals wider behavioural phenotype (e.g., parental care) in house wrens. I have also examined the links between behavioural types in North Island robins and their responses to unfamiliar people (listen to a short interview on this research here). I continue to work on the relations between various personality traits and and animals’ wider behavioural phenotypes in house wrens and Japanese great tits.

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A significant relationship between boldness and aggressiveness and boldness in male house wrens (top), which suggests that these traits are related to one another. While aggressiveness did relate significantly to male investment in parental care (middle), boldness did not (bottom). Taken from Barnett et al. (2012). Ethology.

The evolution of aposematism and the maintenance of cheating: A common defence strategy organisms use against predators is to incorporate toxins into their body tissues which they advertize with conspicuous signals (aposematism). Aposematic signals increase the speed at which predators learn to avoid chemically defended prey and also increase the memorability of the prey. Moreover, these aposematic traits were assumed to eventually lead to predators stopping their attacks on aposematic prey. However, some of my research has shown that educated birds eat aposematic prey and that the number of aposematic prey eaten increases when birds are energetically stressed.

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The mean masses (top) and numbers of defended and undefended prey eaten (bottom) by European starlings. Birds ate more chemically defended prey when they had lower energetic reserves. Taken from Barnett et al. (2007). Behav. Ecol.

Aposematic species are often copied by other species which gain the benefits of the conspicuous signal, but do not incur the cost of producing toxins. These mimics are thought to be increase predation on the models and therefore are considered parasites of the models because they reduce models’ fitness. I am presently working on theoretical and empirical approaches to solving the problem of how mimics may be able to persist in populations without incurring a fitness cost on their models. I am also interested in starting a project to examine the relation between aposematism and parasitoids in butterflies.

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The number of prey eaten by European starlings throughout daily sessions depending on the levels of variation in chemical defences that the prey had. Both prey types had the same mean level of defence, but had differences in the amounts of variation around the mean. These results showed that birds preferred prey which had less variation in their defences (fixed defence prey) around the mean which suggests that uncertainty of prey defence was an important factor in determining their preferences. Barnett et al. (2014). Biology Letters.

Life-history trade-offs: Animals gain resources from their environment and can use them for growth, maintenance, or reproduction. Animals cannot invest maximally all of their traits. If they could, they would grow without without cessation, reproduce without limit, and live forever (what we call a Darwinian demon). Therefore, when animals budget their resources they need to decide where they should expend them and what mix will maximise their fitness. For example, young animals might expend few resources on reproducing and maximise growth and maintenance. Conversely, old animals may expend most of their resources on reproduction and minimize expenditure on growth and maintenance. These age-dependent differences in strategies therefore are related to the probability of survival until the next breeding attempt. I have studied life history trade-offs in insects in relation to between immune responses (maintenance) and spermatophore production (reproduction) in crickets.Screen Shot 2013-12-11 at 2.14.06 PM

The trade-off between the change in lytic activity (a measure of immunity) and spermatophylax (a measure of reproductive investment) mass in decorated crickets. Males that invested a lot in immunity tended to have small spermatophylax mass. Taken from Gershman et al. (2010). J. Evol. Biol.

 Traditional models of evolutionary life-history trade-offs concentrate on the differences in investment among individuals or in the same individuals at different times of their lives. However, it is becoming increasingly clear that parents may also bias investment within reproductive events in favour of certain offspring. Part of my current research focusses on understanding the behavioural correlates with how parents might make these investment decisions. I am also interested in studying life-history trade-offs in invertebrates in relation to development and resource limitation and I am collaborating with other researchers working on incubation strategies in relation to environment.

OLYMPUS DIGITAL CAMERAThese two Japanese great tit nestlings came from the same nest. The difference in their size is likely the result of their mother starting to incubate the eggs having not completed the clutch. This means that earlier laid eggs would hatch earlier and so gain a head start on their brood mates and lead to a size hierarchy. This hierarchy remains throughout development and has many consequences for the birds as they become independent from their parents and recruit into the breeding population. Many explanations have been suggested for the mother initiating incubation before her clutch is complete. I am working on some exciting data I have gathered on this problem which I hope will increase our understanding the behavioural mechanisms that lead to size hierarchies within nests. Barnett & Suzuki. Unpublished data.

Behavioural endocrinology: Hormones are chemical messengers within organisms that are secreted by glandular organs in order to communicate with another part of the body. As such, hormones have a large part to play in mediating the behaviour of animals. One of my interests is understanding the relationships between different hormone systems and animal behaviour. Specifically, I am interested the effects of testosterone and stress hormones (corticosterone and cortisol) on animal behaviour and animal growth and development.

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Nestling house wrens that hatched from eggs that had been  supplemented with testosterone begged more unsupplemented nestlings at a young age (4-5 days old), but this effect was not significant when they were older (9-10 days old). This suggests that the amount of testosterone that is in the egg (from the mother) can affect the behaviour of nestlings, but only whilst they are young. As nestlings got older, they began producing their own testosterone and they generally begged less. Taken from Barnett et al. (2011). Anim. Behav.

Natural history: Most of my studies are informed by natural history and observations of animals living in their natural environments. Although most modern behavioural research is hypothesis driven and experimental, observations of animals in their natural environments are important because they may inform research and act as a natural starting point for the serious study of any organism. By taking this holistic approach, we can gain an understanding of how animals relate to one another and to their environments. Therefore, observing animals may be as important for biologists as reading scientific literature with regards to informing research and formulating ideas. I have published a number of short notes on various observations which are important for  researchers to build anecdotal evidence and knowledge.


Click the photo above to navigate to a webpage with a movie of a Japanese marten attacking the nest of a Japanese great tit. Such observations are interesting because they allow us to better understand how martens attack bird nest boxes and shows that martens are intelligent and persistent problem solvers. In future such observations may allow us to build nestboxes that are better able to withstand marten predation attempts. Taken from Barnett et al. (2013). Mamm. Study.

Kyoto bird diversity and abundance: The world is currently in the midst of great environmental change.  For example, the global climate is changing because of increased carbon entering the atmosphere which is generally warming the atmosphere and creating more volatile weather patterns. The effects that this and other environmental changes have on the biological community are poorly understood. Therefore, I began a project with one of my classes at Kyoto University in 2016 to examine the long-term changes in bird abundance and diversity.  It is anticipated that over time we can study the long-term changes in the Kyoto bird community whilst also increasing undergraduate student participation in research.


Here, two undergraduate students are collecting data simultaneously in a five-minute bird count.  We did this 22 times in total and examined these data for the inter individual reliability using an intraclass correlation (ICC).


The results from the analysis shows that the data were very reliable with an intraclass correlation of 0.81. On each axis is the number of individual birds counted by each observer. The size of the circle corresponds to the number of times the two observers made a particular count.  These data show that even observers with a small amount of training can collect useful ecological data. We also found a significant positive relationship between park size and bird abundance and diversity. Taken from Tsujimoto et al. (In preparation). Ornithol. Sci.

Future research directions

I am a concPICT0054ept driven researcher, who takes uses an integrative approach to study behaviour in many taxa. While I have many interests, there are a number of topics on which I would especially like to work in the future.

Conservation: I am interested in conservation and how behavioural ecology may enlighten conservation decision-making. One promising topic I would like to examine are the differences in how individual animal’s behaviours differ between large populations and smaller (endangered) populations.

Aposematism and cheating: I am interested in continuing to examine aposematism and cheating from a theoretical and empirical perspective. I am particularly interested in developing a selection experiment using public green spaces and using artificial prey. I am also interested in developing a research programme that examines aposematism whilst simultaneously integrating multiple selection pressures.

Chemical ecology: I am interested in developing projects in chemical ecology in birds and insects in collaboration with other researchers.

Environmental change: Humans have caused massive changes to the environments in which animals live. We have created completely novel environments such as urban areas. We have changed plant and animal communities which have dramatically modified other environments. We have moved species around the world to create completely new species assemblages. Finally, we are modifying the climate which affects all aspects of the environment worldwide. Some species cope with these changes well, whilst others are poor at dealing with these changes. I am interested in studying the behavioural and life history factors that might make some species good at dealing with change and others poor at dealing with change.

Check out my ResearchGate page (click button below).

email: optimalforager  ‘at’ hotmail ‘dot’ com

Last update: 28 March 2016.

Craig A Barnett

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