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In layer hen commercial production systems, chicks are not raised by hens and do therefore not receive any maternal care. In the wild, after hatching, chicks undergo filial imprinting where they create a social bond with a stimulus in their surrounding environment, usually the mother hen. Filial imprinting behaviors remain in chicks until adulthood. This bond and maternal care influence the emotional development of chicks. Here, I aimed to investigate short- and long-term effects of filial imprinting on a model hen, on the emotional state of White Leghorn chicks, hatched at Linköping University. To measure optimism, pessimism, and fear, a judgment bias test (JBT), an open field test (OFT), and a novel object test (NOT), was performed and replicated. Before the tests, half of the chicks were imprinted on a model hen, while the other half was not given such a model to imprint on. All chicks were weighed during the entire project. The hypotheses were that the imprinted chicks would be more optimistic in the JBT, show less fearful behavior in the OFT and NOT, and weigh more compared to the non-imprinted chicks. If these results would be found, imprinting could potentially be used to reduce stress in commercially hatched chicks, and thus improve their welfare. The results were inconsistent with all three hypotheses. This indicates that imprinting on a model hen, did not have a positive impact on the chicks’ emotional state. Further studies need to be performed to find methods to improve commercially hatched chicks’ emotional welfare.

The continuing increase in urbanization is changing the natural habitats of wild animals. Some wildlife have colonized urban areas and are exposed to new stimuli to which they respond differently: some species adapt whereas others thrive. Living in such an environment can lead to increased stress and elevated aggression. The purpose of this study was to examine the intraspecific aggression among mallards (Anas platyrhynchos) in two habitats with different degree of urbanization. Field observations were performed on groups of mallards in urban and rural environments. I predicted that there would be more aggressive behavior among mallards in urban than in rural habitats, based on the hypothesis that increased stress in an urban environment results in elevated aggression. Aggression was defined as the number of attacks, which was classified as chases, nips, and threats. I observed on average more than three times as many attacks (chases, nips and threats) in urban as in rural habitats. In addition, more females relative to males in the groups resulted in more attacks. Wild birds are important to flora, fauna, and man. Because high aggression can affect the fitness of wild urban animals negatively through, for example, physical injuries and increased disease transmission during fights, it is important that humans intervene to prevent this., Den fortsatta ökande urbaniseringen förändrar vilda djurs naturliga habitat. Vissa vilda djur har koloniserat urbana områden och utsätts för nya stimuli som de responderar olika på: somliga arter anpassar sig medan andra frodas. Att leva i en sådan miljö kan leda till ökad stress och förhöjd aggression. Syftet med denna studie var att undersöka den intraspecifika aggressionen mellan gräsänder (Anas platyrhynchos) i två habitat med olika nivå av urbanisering. Fältobservationer genomfördes på grupper av gräsänder i urbana och rurala miljöer. Jag förväntade mig att det skulle förekomma fler utdelade attacker bland gräsänder i urbana än i rurala habitat, baserat på hypotesen att ökad stress i en urban miljö resulterar i förhöjd aggressivitet. Aggression definierades som antalet utdelade attacker, vilket klassificerades till jagningar, nyp och hot. Jag observerade i medel mer än tre gånger så många attacker (jagningar, nyp och hot) i urbana som i rurala habitat. Utöver detta resulterade fler honor relativt hanar i grupperna i fler attacker. Vilda fåglar är viktiga för flora, fauna och människa. Eftersom hög aggression kan påverka vilda urbana djurs fitness negativt genom till exempel fysiska skador och ökad sjukdomsöverföring vid strid, är det viktigt att människan ingriper för att förhindra detta.