Cognitive abilities and brain size in Red-backed Shrike Lanius Collurio

Cognitive processes, such as perception, learning, long-term memory, working memory, attention, and decision-making, determine many behaviors that affect the ecology and evolution of animals, such as nesting site selection, food choice, predator defense, or mate choice. The main goal of this project is to find out if cognition depends on brain size and if their variation at the intraspecific level is related to important processes that influence individuals’ fitness, such as habitat selection, prey selection, or being innovative in a changing environment. Although it has been shown before that cognition is closely related to brain size in many different species of birds and other taxa, including humans, studies on individual differences in brain size, cognition, and the fitness consequences of these differences are extremely rare. This is the first time that studies focus on such crucial behaviors as avoiding predation by choosing safer habitats, foraging on newly introduced but abundant and easy-to-get prey species, and using material newly introduced in the environment to strengthen nest construction. We would like to answer several questions concerning the relation of these cognitive aspects and brain size: Do birds with bigger brains choose safer habitats than small-brained birds? Do birds with bigger brains switch faster to more abundant, easy-to-catch prey than birds with smaller brains? Do birds with bigger brains show more innovation than small-brained birds? Thanks to studies on barn swallows, it is now known that there are interindividual differences in brain size and that brain mass is correlated with external head volume independently of overall body size. Similarly, head measurements as a proxy for brain size are commonly used in pediatrics because head circumference is correlated with brain mass and intracranial volume. Studies will be conducted on Red-backed Shrike (Lanius collurio), and they are based on the assumption that brain size is correlated with head dimensions, which was proved by Møller in 2010. All three hypotheses require conducting routine procedures in each part of the breeding season. After establishing territories by pairs of birds, we will start to search for nests in all potential locations. Individuals will be caught in mist nets, individually banded, and measured (mainly height, width, and length of the head). To test the first hypothesis, we will focus on predation rate and a few characteristics of the nesting site chosen by birds (structure of shrubs, nest exposition, nesting shrub species). Nests will be regularly controlled to determine breeding success and the cause of failure. Birds choosing safer habitats are the birds with better cognitive abilities; thus, they should have bigger brains. The second hypothesis will be tested using a simple method of introducing a new species of prey. After introducing mealworm larvae in birds’ territories, we will test if individuals of known head measurements differ in the time they need to start foraging on easy-to-catch, abundant, but unknown prey. Two-hour experiments will be recorded to obtain the best quality data. The third hypothesis will be tested by introducing new material – cotton strings that can be easily incorporated into nest construction. Next, we will analyze if birds that used new material are the birds with bigger brains. The results, to a large degree, will complete the understanding of topics on which our knowledge is still poor: the relation between individual differences in brain size, cognition, and their effect on individuals’ fitness. This project is the first one considering not only the relation between brain size and the probability of breeding failure caused by predation but also the process of habitat selection, including rarely studied nest site availability. It will be the first time that foraging strategies and their relation to brain size will be studied. Research on innovative behavior and brain size at the interindividual level has never been conducted before. Moreover, thus far, no experimental studies have been carried out. Most of the studies on brain size and cognition have been comparative studies. Comparative studies were under strong critique in the past. The project is based on hypotheses concerning the most important aspects that affect evolution and has never been tested before. Publication of results is planned in the pages of leading magazines from the group of ecology, evolution, and behavioral ecology. The results will form the master’s and bachelor’s theses of graduate and undergraduate students from the University of Life Sciences engaged in fieldwork on the project. We will also try to disseminate our results in popular science literature.