The mighty migration that hundreds of bird species pull off every year is no simple feat. In some cases migration requires flying thousands of kilometres to reach another location in order to wait out the harsh winter months. Essentially, when the conditions of a habitat are no longer ideal for feeding, breeding and raising their young, it is time for birds to get on the move.
There are about 4,000 species of birds that migrate – that makes up 40% of the total number of birds in the entire world! Because of this, there are many, many different migration patterns that exist depending on the species of bird and their starting location. Most migrations travel from northern areas to southern areas, where birds will find warmer wintering grounds. Owing to the sheer difficulty of making this journey, over time birds have developed the perfect morphology and physiology to help them. Birds require certain features that help them fly fast (such as a lightweight skeleton) and fly for long periods of time (like a very high stamina).
Impressively, the red knot migrates farther distances than any other species of bird. The red knot breeds in Siberia, and winters on the west coast of Africa – that means red knots must travel approximately 16,000 kilometres, not once, but TWICE a year! How miraculous!
But how do birds know where to fly?! Good question! Bird migration is still not even fully understood, but there are some theories! For instance, it’s thought that during the day, birds are able to guide themselves based on the position of the sun, and at night they follow the stars. Additionally, some species of birds may be able to detect polarized light and the geomagnetic field – now that’s complicated stuff!
Unfortunately there are many obstacles that birds must overcome to make their great migration; if migrating wasn’t hard enough already, humans have only made it harder! Large cities full of tall skyscrapers often pose a major issue for our bird pals. Not only do their bright lights cause confusion and disorient birds along their route at night, but many birds crash into windows or try to fly against them until they fall from exhaustion. Urban development is one of the main reasons some bird species, such as the red-eyed vireo, ovenbird and the Swainson’s thrush, are facing population decline.
Want to help out our bird buds?! Check out the For the Birds Mission on the Earth Rangers App to learn more about what you can do to help out your local bird population.