How Does Global Warming Impact Bird Migration? 10 Surprising Facts
The global geographical scale of bird migration is not just impressive, but it also baffles scientists around the globe. How do birds know when to up and leave, and how can they cover such long distances? What we do know, however, is that climate change alters the fundamental effects of migration on ecological processes and biodiversity.
Global warming is partly to blame for the fact that birds seem to migrate earlier and earlier with every passing year, say scientists. The Icelandic black-tailed godwits are just one of the instances when the migration period has advanced by two weeks over the past two decades. So what is to be done?
Why Bird Migration Is Crucial
Earth’s ecosystems are like parts of a very detailed and well-oiled machine, and movement is an integral part of that. Many animals and birds have it in their blood. When migration patterns get altered, it also affects biodiversity at local and global scales. There’s no doubt that migratory birds play an important in many ecosystem processes.
Due to problems we will soon discuss, many birds not only suffer changes in their migrating phenology, but also stop their migratory behavior altogether. Birds and animals alike have adapted to live in sedentary populations as a result of man-made changes to their environment.
Scientists have discovered that the lack of migratory behavior also influences the incidence of infectious diseases. When individuals periodically leave contaminated habitats through migration, they can reduce the incidence of disease. During migration periods, members of a species are more separated from each other; at the same time, infected individuals rarely survive are long-distance movement.
Environmental Cues & Migration
Animals and birds schedule their migration after climate cues and predictable environmental changes. Weather also helps them to navigate, which is why a change in these cues has dire effects on the extent and phenology of migration. Global warming strongly affects the arrival date and hatching date of migrating birds, which messes up the entire ecosystem.
One of the largest effects of climate change is higher temperatures. The insect prey of hatchling birds make an earlier appearance in warmer climates, which, in turn, puts pressure on earlier bird breeding. It is crucial that the hatchling process coincides with peak prey abundance.
At the same time, scientists have observed some Palearctic migratory birds already experience earlier departure from the non-breeding lands in Africa. Consequently, climate change alters migratory bird movement due to the necessary global shift in departure and arrival times.
Climate Change & Bird Migration
There are many ways in which climate change already affects migratory birds. More heavy storms, higher drought frequency, sea level rises and habitat shifts which result from global warming can all dramatically impact the patterns of migratory birds. Here are some of the climate consequences scientists have already started to observe.
- The loss of habitats – The main problem with loss of habitats on the migratory route is that birds have no fuel to sustain them during their long flyway. The habitats migratory birds depend upon are either changing or even in danger of disappearing. Increasing temperatures, desertification, and flooding are just some of the causes that completely change the face of coastal wetlands where migrating birds used to nest, rest, and forage.
- Climate change affects patterns of migration – With global warming, migratory journeys are starting to get cancelled. The birds’ annual migration rhythm has changed drastically due to changing temperatures. A lot of migratory birds shorten, change or completely cancel their routes.
- Climate change causes food shortages – The saying “The early bird catches the worm” may be true, but what happens when the warm spring temperatures lead to the earlier arrival of too many birds? As we already discussed, changes in migration patterns alter a well-oiled machine; unfortunately, the shifts in arrival, departure, and breeding are not in line with each other.
- Climate change represents a global threat – The Earth’s climate constantly changes throughout time, leaving some bird species unable to adapt and becoming extinct. While previous warming periods may have been natural, the climate change we experience today is different. Man-made actions accelerate the speed of change, leaving more and more bird species unable to cope with the results.
Surprising Bird Migration Facts
- Scientists awarded the Arctic Tern as the bird with the longest known migration route. It travels about 22,000 miles annually, flying between the breeding land in the high Arctic and the winter grounds in the Antarctic.
- Migrating birds travel at various speeds, ranging from 15 to 50 miles per hour. The speed of flight depends on the species, prevailing winds, and flight patterns.
- About 40 percent of the total number of birds in the world are regular migrants – which amount to at least 4,000 species bird species. Scientists expect this number to increase as we discover more about the migratory habits of tropical birds.
- Even though migration is at its finest during spring and fall, birds migrate all throughout the year. The actual dates of when birds begin their migration depend on various factors, including bird species, travel speed, route, migration distance, weather changes, and more.
- Migrating birds use the stars and sun to navigate on their route. Wind patterns and landforms are also useful, helping them arrive at the precise same locations every year.
Migration: Nature’s Miracle
- A single bird completes a one-way migration in a few days, a couple of weeks or up to four months. The duration of the flight depends on the total distance, flight speed, stopovers, and overall route difficulty.
- Birds that migrate across an ocean – also known as transoceanic migrants – may fly up to 100 hours at a single time before they reach any land. In conditions of extreme weather, these birds seek safety by landing on ships at sea to get some rest.
- Migrating birds have it rough along their journeys; they face window collisions, hunting, confusing lights that disrupt navigation, predators, and habitat loss. Juvenile birds with no experience are at greater risk.
- Before starting to migrate, many birds enter a state called hyperphagia, where hormone levels encourage them to store fat in body weight for more traveling energy. Some bird species are known to double their body weight in the weeks before migration.
- Larger birds with proportionally larger wings fly faster than smaller birds. If the flock stays in the air for 10 hours a day, it can fly about 400 miles each day!
Many long-distance migrant bird populations are currently on a very fast decline rate. Identifying the ways climate change affects these populations is surely one of the keys in understanding the causes of these declines.