ADF/Cofilin

continue to build very similar nests just as 'closed-ended' song learners that learn songs only in their first year of life do not subsequently change their songs. Where this is the case, one should expect nests of the same species to be very similar with as much variation within a bird as among birds. Although young weaver birds take longer and build less effective nests than do experienced birds, it is not clear whether experience continues to be accumulated once the birds are mature. It is not out of the question that birds learn about nest materials and construction while in the nest, just as they imprint on their siblings and parents so as to stick to mother while young and vulnerable, and to mate with the appropriate mate when sexually mature. This process has sufficient plasticity that young birds may imprint on any moving object, as was memorably demonstrated by Konrad Lorenz, whose hand-raised goslings both followed, and later attempted to mate with, his Wellington boots. Cross-fostering experiments would help to determine whether or not birds acquire information during early development in a way that is akin to imprinting. Alternatively, one would expect to see significant similarity between the nests built by parents and offspring. The most cognitively sophisticated scenario is one in which learning would underpin all, or nearly all, of the nest building process, from choice of suitable sites for placement and suitable materials to how to put those materials together. One would expect to see not only practice nests in young birds but continuing evidence for experience modifying nest manufacture and quality throughout adult life. Additionally, one might expect to see a bird, presented with a nest that has been experimentally damaged in an unusual way, repair it in the most direct and economic way, as if it had a concept of the completed structure. Such an experiment was conducted in the 1950s on a wild population of baya weavers (Ploceus phippipinus), but the results were very variable and difficult to interpret. Implications for models of complex cognition. The value of understanding complex cognition in birds has been long and amply demonstrated by the vast and increasingly sophisticated work on song learning. The mechanisms for understanding song may also be helpful in addressing the role of cognition in nest building. If nest building requires at least some kind of 'complex' cognition this may mean a fundamental …