It’s evident that our pets have personalities, but have you ever thought if animals living in the wild have their own personalities? It has been recently suggested that city life is changing the personalities of wildlife. One studied species you are probably familiar with is blackbirds. Blackbirds are a constant pest in an urbanized setting. During an experiment, researchers presented a variety of objects in front of blackbirds found in urbanized settings and those found in forests. The urbanized blackbirds were very hesitant towards unknown objects. In general, the term used to best describe their personality is cautious (Society, 2013). The isolation of blackbirds in cities from their species has created a whole new subspecies: the urban blackbird. This subspecies exemplifies how the structural barriers humans have made can affect evolution. There are a few different ways that a new species can arise. In the case of the urban black bird, parapatric speciation occurred. Parapatric speciation occurs when a smaller population is isolated, usually at the periphery of a larger group, and becomes differentiated to the point of becoming a new species. While the bobcats above were separated, they populations did not diverge enough to create a new species; the west-sided population just developed the ability to resist mange. If these genetic changes are different enough from the original species, this can create a new species of the animal all together. This has been evident in black birds and mosquitos. Prior to the urbanization, black birds were very shy, isolated animals. The birds were fearful of humans and remained solitary organisms. The birds had long, thin beaks that allowed them to peck and pierce at their food. Similar to other species of bird, black birds would migrate south for the winter and return north once spring arrived. Once cities began to rise in Germany and Italy, the blackbirds had to evolve to fit this new environment. The cities provided warmth, an ample supply of food, and a brand-new place to create shelter. The cities also brought a variety of different threats such as vehicles, human interaction and electrical wires. The specific populations of birds found within city limits began to adjust to new life. The birds were less frightened by humans and they began to co-exist. Their long thin beaks were no longer advantageous as their diet shifted from insects buried deep in the mud to garbage left out in the street and food found in trash cans. Since a long thin beak was no longer needed, the beaks shifted towards short and stubby. Birds also have an innate stress response that varies from species to species. These stress responses alter the physiology of the bird and can help predict the ability of the bird to survive in an environment. In addition to a change in beak, the birds have a much different stress response. The environment and stressors the black birds perceived within the cities was much different than those they would encounter in the wild. The Urban-dwelling black birds lived within cities and they had to create new nests. Their nests were found scattered throughout the city, but because the nests were near city life, birds discovered that they were able to stay much warmer. As the cities radiated increased levels of heat, the population of black birds no longer had the need to migrate. Since their winters were much warmer and the food supply was proficient, the urban-dwelling black birds stayed where they were during the cold winters. With the lack of migration, the Urban-dwelling black birds developed different mating habits. The birds shifted and began their mating much earlier in the year (Palumbi, 2001). This isolated the urban-dwelling birds to interbreed with just their secluded population. Because the characteristics of this new black bird isolated the population from breeding with their ancestral black bird species, this allowed a whole new species to form. The genetic traits of the Urban-dwelling black bird are so much different than that of the common black bird that the two populations are now being considered different species (Palumbi, 2001). While the two species were not completely isolated from each other, the different environments that the birds relied on changed the physiology of the birds to the extent where they would no longer interbreed. This is a prime example of how the structural barrier humans set up have shaped the evolution of animals.