Eight key types of bird migration you need to know
Bird migration is a wonderful phenomenon of nature and, as summer comes to a close, we are on the cusp of a new wave of migrants from distant shores. Most birds migrate for two core reasons: to find a more suitable habitat due to rapid changes in their local climate (i.e. a drop or increase in temperature), or to seek out a more abundant source of food.
Underpinning these reasons are many varied types of migration, performed by most birds around the world. There are birds whose migratory patterns follow landmarks, some that utilise wind and differing climatic arrangements, and those that use astronomical signals, as well as, incredibly, fundamental principles of physics such as quantum mechanics (see www.wired.com/2011/01/quantum-birds) as a directional aid.
Below we take a look at eight of the key methods birds use around the world for moving from one place to another.
The most common, and therefore well-known, form of migration occurs between breeding patterns, which are affected by seasonality. Most people are acquainted with incoming migrants appearing prior to the beginning of spring and leaving in autumn.
Latitudinal migration is simply the process of moving from north to south, and vice versa; it is, in fact, the most common form of migratory pattern. The specific directions in which birds travel back and forth are influenced by geological factors such as mountainous regions, but essentially latitudinal migration is caused by northern wintering when birds migrate further south for warmer conditions.
This form of migration typically occurs between east and west, a common form of longitudinal migration for European birds. It’s easier to think of these birds as simply going across and back.
The Grey wagtail is an example of a bird that uses altitudinal migration, the process of moving between varying elevations i.e. from high up in a mountain to a lower point closer to the ground. This type of migration comes into effect if there is, for instance, a significant amount of snow at a high level; the bird, thus, is compelled to seek out a safer place lower down.
With loop migration, birds follow a circular path, which usually lasts for the whole year, dropping off at certain points throughout their yearly cyclical journey, ultimately ending back up at a starting point. It is a form of migration common among seabirds, and often coincides with seasonal wind patterns that aid travel.
This is a form of migration that occurs in sudden bursts and is often quite unpredictable. It’s a behaviour that can happen with Waxwings if local food and water sources are scarce. In fact, in early 2017, Britain experienced a sudden irruption of Waxwings due to harsh conditions in Scandinavia. Apparently, Waxwing irruptions occur on average every 6-7 years.
Moult migration coincides with the yearly moulting period that birds experience while shedding and re-growing feathers. Birds are often vulnerable during this time so, in order to avoid predators, birds migrate to a safer place until the moulting process in complete.
Drift migration is a rarity in nature, and is often caused by an unusually intense weather event such as a storm. Large flocks of birds can be affected by strong winds, and can sometimes “drift” far off their usual course. Many birders anticipate such events, as they may catch a glimpse of birds that wouldn’t ordinarily appear in certain locations.