Weather radar data shows that many North American species are changing their spring migration by two days every decade due to the effects of climate change.
What is the difference between a flock of birds and a storm?
It sounds like a dad joke, but it's a serious question for biologists. Scientists have recently devised a new way to track migratory birds using climate technology.
And they are discovering that climate change may be affecting the movements of billions of birds each year.
A study published in the journal Nature Climate Change suggests that rising temperatures are causing birds to migrate a little earlier each spring. He finds that the journey home is progressing a little less than two days every decade.
That would not be all, the surprising thing about the results is that they apply to hundreds of migratory species throughout the country. In other words, climate change is causing a remarkable, albeit gradual, change in one of nature's greatest natural phenomena.
The researchers, led by Kyle Horton of Colorado State University, analyzed millions of radar scans collected between 1995 and 2018. They used a high-tech method to differentiate between migratory birds and weather systems, a special type of artificial intelligence known as a neural network. Neural networks are based on complex sets of algorithms and can be trained to recognize patterns in data.
In this case, the researchers trained their neural network to classify biological patterns, that is, flocks of birds, from patterns of precipitation in climate scans. They also examined climate data from across the country.
The results revealed that spring migration is changing earlier, and appears to be driven by rising temperatures. The researchers also observed some changes in the fall migration, although the relationship with temperature was much weaker.
Previous studies have suggested that some types of birds may be altering their migration patterns in response to climate change. But the new study looks at the problem on a much larger scale. The results reflect the behavior of hundreds of species, from the east coast to the west.
While rising temperatures appear to be the overall driving force, its exact effects on bird behavior can vary from species to species. Bird migrations are believed to be influenced by a variety of factors, such as the growth of new plants or the availability of food.
These relationships are important to investigate in the context of a changing climate, the authors suggest. Other studies suggest that global warming may also be affecting the timing of flowering of spring vegetation or the abundance of insects and other food sources, factors that can strongly affect the survival of migratory birds.
Some scientists worry that changes in migration patterns are not necessarily kept in sync with these other consequences of global warming and that some species of birds may suffer as a result.
Meanwhile, the timing of migration is not the only indicator that global warming is affecting migratory birds. Earlier this month, a study of 52 species published in Ecology Letters found that bird bodies get smaller over time as their wingspan lengthen, apparently in response to rising temperatures.
The smaller size may allow animals to lose body heat faster as the weather warms up, the researchers suggest.