Bird species from across the globe have physical features that are a result of adaptation over time to suit their environment and the available food sources, and as protection against predators. Birds are among the most adaptable wildlife on the planet and they can travel incredible distances to find suitable habitat. Many of the adaptations or changes are physical including bill shape, behavioural changes and changes to their song.
Phenotypic plasticity is the ability of a creature to adapt to changes in its environment rather than by natural selection, which may cause a species to die out if it is unable to adapt to environmental changes. The changing environment induces the individual adaptive mechanisms. This is different from a long-term calibration caused by natural selection, which favours earlier-breeding birds. Plasticity generally occurs more rapidly than does natural selection.
Changes in Basic Metabolic Rate
In the January 2010 issue of the "Proceedings of the Royal Society," Andrew E. McKechnie et al reported that the basal metabolic rate of bird species in captivity and in the wild undergo reversible adjustments. Captive bird species exhibited different basal metabolic rates as the same species in the wild, meaning that birds could adapt metabolically to their environment when it changed.
Adapting to Global Warming
Since the 1970s, there has been a steady increase in the temperatures of the habitat of the Parus major, which is a colourful songbird, also known as the great tit, and found in the United Kingdom and Europe. Ornithologists from the University of Oxford have completed a study of the adaptation of these birds to global warming. The earlier onset of spring has caused the early hatching of a particular moth caterpillar, a favourite source of food for the great tits. The birds have adjusted to this early hatching by laying their own eggs about 2 weeks earlier, to coincide with the early moth hatching.
Adaptation to Urban Settings
Studies of great tits living in ten European cities, comparing them with great tits living in nearby forests, have uncovered a noticeable difference in the vocal repertoire of these songbirds. The great tits in the cities have increased the pitch and frequency of their song to make allowance for the low frequency sound of a bustling city. As these birds rely on their song to attract mates, it is important that they are heard above the noise of the city. The great tits living in nearby forests linger on the first note of their song because the forest air turbulence is less, allowing them to be heard more easily by other birds.