Does coping style predict optimization? An experimental test in a wild passerine bird

Abstract

A number of studies have suggested that avian brood size is individually optimized. Yet, optimal reproductive decisions likely vary owing to amongindividual differences in environmental sensitivity. Specifically, 'proactive' individuals who do not track environmental changes may be less able to produce optimal brood sizes than 'reactive' individuals who have more precise local environmental knowledge. To test this, we quantified exploratory behaviour (a proxy for proactivity) in a great tit (Parus major) population, manipulated brood sizes (reduced, control, enlarged) and evaluated whether individuals of dissimilar coping style differed in their level of optimization. If reactive females behaved optimally, any deviation from their original brood size should lower fitness, whereas this should not be the case for proactive females. Reactive females indeed performed best at their natural brood size, whereas proactive females performed best when raising an enlarged brood. These findings imply that proactive females produced sub-optimal brood sizes. We speculate that proactive females might (i) take decisions based on biased perception of their environment, (ii) face energetic constraints in offspring production and/or (iii) be more willing to invest into current reproduction when given the option. Our findings provide experimental evidence for coping style-related differences in optimal reproductive decisions and life-history strategies.

The relationship between personality and cognitionin the fowl, Gallus gallus

“…Interestingly, there are studies that use the term coping style, which have created a bimodal distribution by directional selection for extreme personality types (e.g. great tits, Verbeek et al 1994;Nicolaus et al 2015). It is not clear if a bimodal response in coping style tests is specific for rodents, and only present in other species after selection on extreme phenotypes.…”

“…For example, the tip of the beak is used for tactile discrimination (Gentle & Breward 1986), olfactory cues used to detect cues from predators (Zidar & Løvlie 2012), and sounds used to communicate with conspecifics (Gleich & Langermann 2011). As in many bird species, their sight is well developed and their primary sense (Nicol 2015). They can see and focus on objects that are close, such as food on the ground, and at the same time observe things at a distance, like predators high up in the air (Dawkins & Woodington 1997).…”

“…This is despite that avian brains are functionally similar to mammalian brains, and that both birds and mammals show cognitive complexity (Emery 2006;Butler 2008). Research in large deviates from the general perception of simple and dumb chickens, and instead reveals chickens to be cognitively, behaviourally and socially complex animals (Nicol 2015;Marino 2017). For example, chickens use referential communication with a specific sound for ground predators as opposed to aerial predators, which triggers different responses in the receivers (Evens et al 1993).…”

“…Despite strong selection for production traits (eggs and meat), the domestic fowl still resembles their wild relative in behaviour and cognition (Nicol 2015;Marino 2017). In the wild, red junglefowl populations are decreasing due to habitat loss, over-hunting and hybridisation with chickens (BirdLife International 2016).…”

“…Domestic chicks have been used widely in cognitive studies of for example lateralisation, early learning and memory (Bolhuis & Honey 1998;Rogers 1995). Chickens have also shown good spatial ability, making them suited for investigations of spatial learning (Tommasi & Vallortigara 2000;Nicol 2015).…”