Climate change is profoundly affecting bird populations across the world. This is not surprising as previous studies have shown that species that depend on high-elevation forest habitat, long-distance migrants, and coastal breeders are most at risk from climate change. Shifting seasons, warming temperatures, changing precipitation, and rising sea levels are already disrupting their behavior and the ecosystems that support them.
Birds Face Threat of Extinction
The climate crisis has alarmingly affected all species of birds. In the State of the Birds Report by Mass Audobon, 43% (61 species) of 143 bird species evaluated are highly vulnerable to the effects of climate change, 15% (22 species) are likely vulnerable, and 42% (60 species) are least vulnerable. Studies have also shown that nearly three billion birds have disappeared from the US and Canada in the past half a century. If left unaddressed, there’s a huge possibility that many bird species will be extinct in the next few years.
The 2019 annual report by the National Audubon Society, a nonprofit dedicated to protecting birds and their habitat, was particularly startling. The researchers found out that more than two-thirds of North America’s bird species will be vulnerable to extinction due to range loss by 2100 if Earth continues to warm. “Birds, because of their relatively greater capacity to disperse and migrate, serve as a conservative baseline for other taxa facing the threats posed by climate change,” the report said.
The researchers from the National Audubon Society were able to assess the danger that climate change poses to 604 of North America’s bird species using more than 140 million records from recreational birdwatching databases, long-term surveys, and scientific studies. Each species’ current distribution was used to create models then used projections about future climate and vegetation conditions in forecasting how these variables might affect each bird species’ range.
The Audubon report was released after a study published by the Science journal found out that North America’s bird population has plummeted by 2.9 billion breeding adults since 1970. Kenneth V. Rosenberg, a conservation scientist at Cornell University and the American Bird Conservancy, stated that the reports are complementary. “We've been documenting loss that's occurred over the last 50 years. Using some of the same data, the Audubon study makes predictions about what might happen projecting forward,” he said.
According to CNN, an American news-based pay television channel owned by AT&T's WarnerMedia, the extinction could happen if birds run out of places to live and food to eat. The researchers found out that common loon could lose nearly 97% of the range it can occupy in the lower 48 states, the Great gray owl could lose more than 97% of the places where it can survive, and the piping plover could lose 87% of its habitable area in the summers.
“Birds are going to have to move even further to stay within the conditions that they’ve evolved to inhabit,” Brooke Bateman, the Audubon report’s primary author, said.
How Climate Change Can Impact Nightingales
Unfortunately, one of the many bird species that will be heavily affected by climate change is the nightingale. A recent study conducted by researchers from the American Ornithological Society Publications Office found that nightingales' average wing length relative to their body size has decreased over the past two decades due to climate change. And as Earth gets hotter and drier, the migrating songbird's wings will only get shorter and shorter.
According to The Guardian, a British daily newspaper, the researchers examined the wing sizes of two nightingale populations in central Spain. Usually, nightingales travel from sub-Saharan Africa to breed in Europe each summer. However, the findings showed that it would become a lot difficult for them to return if their wingspans are stunted. "There is much evidence that climate change is having an effect on migratory birds, changing their arrival and laying dates and their physical features over the last few decades," lead author Carolina Remacha said in a statement.
The team also found that the spring season in Spain has shifted to later in the year and droughts over the summer have become longer and more intense. This means that nightingales will only have a shorter time to raise their young. This change could lead to nightingales laying smaller clutches of eggs, with fewer young to feed. Unfortunately, this may simultaneously push nightingales away from all of the linked traits in the "migratory gene package."
According to Science Daily, an American website that aggregates press releases and publishes lightly edited press releases about science, the "migratory gene package" hypothesis predicts that a number of features that help nightingales survive their migration all interact with each other. These features include a long wingspan, higher resting metabolic rate, larger clutch size, and a shorter lifespan. Since these are all connected, if one is negatively affected, all the others can be weakened too.
"If we are to fully understand how bird populations adapt to new environments in order to help them tackle the challenges of a rapidly changing world, it is important to call attention to the potential problems of maladaptive change,” Remacha said.
The findings of the study add to a growing body of research that shows how climate change has been shrinking birds’ sizes. A 2019 study revealed that North American migratory birds have been getting smaller over the past four decades due to warming climate. The researchers used 70,716 dead birds representing 52 species for this research. Of those species, 49 saw statistically significant declines in body size. For instance, the length of the tarsus or lower leg bone shrank by 2.4%.
"We had good reason to expect that increasing temperatures would lead to reductions in body size, based on previous studies," lead author Brian Weeks, an assistant professor at the University of Michigan School for Environment and Sustainability, said.
The team suggested that the shrinking body sizes are a response to climate warming. They found that the temperatures at the birds' summer breeding grounds north of Chicago have increased by roughly 1 degree Celsius (1.8 degrees Fahrenheit) over the course of the study.
Also, the shrinking of body size can also happen to other animal species, taking after Bergmann's rule, where individuals tend to be smaller in warmer parts of their range.