Although bird migrations have been observed for thousands of years, it was not until the early nineteenth century that migration was accepted as an explanation for the winter disappearance of birds from northern climes (Lincoln 1979). Bird migration has been studied using a variety of techniques, of which ringing is the oldest. Color marking, use of radar, satellite tracking, and stable Hydrogen and Strontium isotopes are some of the other techniques being used today to study the migration of birds (Font et al. 2007). To identify migration intensity, one contemporary approach makes use of upward pointing microphones to record the contact calls of overflying flocks; these calls are then analyzed in a laboratory to measure time, frequency, and species (Farnsworth et al. 2004).
What is migration? Migration refers to directed, regular, or systematic movement of a group of objects, organisms, people, or animals. There are two type of migration such as immigration and emigration. Bird migration is one of the most fascinating views for bird watchers and it is refers to magnificent regular journeys to and from a given area undertaken by all or part of a bird population. The bird migration happens to temperate reagent birds but it also occurs in tropic birds. It is also known as nomadism, invasion, dispersal or irruption. Since migration takes a lot of time and energy, they must have really good explanations to do so. These also will increase the chance of survive and reproduce again so that they not become extinct.
Migration is marked by its annual seasonality and bird movements include those made in response to changes in food availability, habitat or weather. Instead of difficulties to find foods and weather changes such as cold temperature, it’s been shown that at least in some birds there are also indicator such as environmental cue. The changes in day length cause pituitary gland (an endocrine gland that controls the release of hormonal stimuli) in...