Object manipulation without hands: kinematics and evolution of nest building by birds

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Crafting is a hallmark of human behaviour. For millions of years, hands have enabled humans to develop important innovations, including tools, shelter even in the extreme environments, and vehicles that can carry us anywhere on Earth and into space. Primate hands consist of five digits and a palm with detailed joints and muscle structure, which enable flexible manipulative actions. Amazingly, however, there are structures built by animals that are uncannily similar to human craftwork, such as fishhooks, woven knots and pottery, but that are built without hands. The builders of such structures are birds: such as crows processing a forked branch to make a hooked tool for extracting food, weaverbirds making knots from grass strips to make a nest, or swallows and ovenbirds using mud to make pot-like nests. How do these birds make such human-like structures without hands, simply using their bills? Answering this basic question would provide not only the important scientific insights into the evolutionary origin of this remarkable crafting ability, but could also provide inspirations and insights for the design of industrial robots and medical prosthetics for damaged or missing hands. To examine how birds build structures hands-free, I will use advanced tracking, lab and field experiments, along with comparative analyses to study the details of nest-building behaviour in birds. Nest building is an excellent model for object manipulation: most bird species build nests; and nests can be made from a wide range of materials including plants, animals and artificial objects. My methods consist of two complementary approaches: behavioural experiments to establish detailed motions used by birds while they handle nest material, and a large-scale computational model to investigate if bill shape and nest materials evolved together. To investigate interactions between a broad range of animals' body shape and nest material characteristics, I will use three bird species: white-browed sparrow weavers, zebra finches and barn swallows, as these species have different bill shapes and use different types of nest material. To determine how birds move their bills during nest building, I will carry out behavioural experiments in the UK, South Africa and Japan through my international partnerships with my host PI Prof Susan Healy and Collaborators Dr Andy Young at Univ Exeter, and Dr Masaru Hasegawa at SOKENDAI. To acquire and analyse the information on bird movements from video footage of the behavioural experiment, I will develop automatic tracking software, and analyse the data using machine learning, in collaboration with Prof Barbara Webb at Univ of Edinburgh. From the experiments and analysis, I will be able to tell what techniques birds use to handle different nest materials, and how the techniques change when a material changes its physical properties. In the latter part of the project, I will construct a global model to examine if bill shape evolved with nest material in a wide range of bird species, under the supervision of Collaborator Dr Sally Street at Durham University and Prof Kevin Laland and Dr Catherine Sheard at Univ of St Andrews. Using these two methods (behavioural experiments and evolutionary modelling) ranging from fine- to global-scale, I will identify the advantages and limitations of object manipulations by bills, ultimately providing insights into the truly unique characteristics of human hands.