Springtime in Alaska has always brought with it the magical sight and sound of millions of shorebirds migrating north to mate and produce the next generation, before fading autumn daylight beckons them southbound to their winter homes.
In Cordova their annual arrival is celebrated in May with the Copper River Shorebird Festival, complete with workshops, guided birding trips, workshops and other educational events. On the Kenai Peninsula in the following week, hundreds also gather for the Kachemak Bay Shorebird Festival.
Prompted now by the impact of climate change, many ornithologists have begun to examine climate change impact on the timing of bird migration, trying to answer how even subtle shifts in migration patterns may negatively impact the health of migratory birds.
“Yes, it is likely that many species in your area (Alaska) will be arriving earlier over the coming decades, especially given the disproportionate warming likely in Arctic regions,” says Andrew Farnsworth, of the Cornell Lab of Ornithology in Ithica, N. Y. “So too the potential for birds to stay later will exist.”
“Shorebird migration is in part a different story, in that it is dominated by long flights and then staging, and severe weather can impact these species dramatically,” he said.
“For larger birds, like waterfowl, their movements may be more flexible to some extents than smaller songbirds. Geese in particular may be able to adapt to arrive and depart when food resources are still good, given their more flexible timing of movements associated in particular with below freezing temperatures, either departing just as these occur or just after warming has occurred,” he said.
Still Farnsworth said that none of the study areas included in a new research report published in the journal Nature Climate Change in mid-December cover as far north as Alaska, so right now they are extrapolating results on land birds for the Far North.
“We hope in the coming year or two to produce an analysis that adds Alaska radar data to our research,” he said.
Farnsworth collaborated with lead researcher Kyle Horton of Colorado State University and artificial intelligence researcher Dan Sheldon at the University of Massachusetts Amherst in the report, which analyzed 24 years of radar data from the National Oceanic and Atmospheric Administration for this study of nocturnal bird migration.
Their research answered key questions on birds and climate change. “Bird migration evolved largely as a response to changing climate,” Farnsworth said. “It’s a global phenomenon involving billions of birds annually. And it’s not a surprise that birds’ movements track changing climates. But how assemblages of bird populations respond in an era of such rapid and extreme changes in climate has been a black box. Capturing scales and magnitudes of migration in space and time has been impossible until recently.”
Horton speaks of their research, which observed nighttime migratory behaviors of hundreds of species representing billions of birds as “critically important” to understanding and learning more answers about shifting migration patterns. “To see changes in timing at continental scales is truly impressive, especially considering the diversity of behaviors and strategies used by the many species the radars capture,” Horton said.
Alaska ecologists like Erin Cooper, at the Cordova office of the U.S. Forest Service, are also working collaboratively with research wildlife biologists like Colleen Handel of the U.S. Geological Survey in Anchorage to track when various bird species arrive each year.
“Climate shifts in Alaska will probably play out differently than in other places, especially in coastal Alaska,” Cooper said. “Not all areas are affected by climate change in the same way. We have seen an increase in temperatures in coastal regions, but when you start talking about small changes every year, you need a longer data set.
“Warmer ocean temperatures make it harder for birds to find food. Seabirds are finding it more difficult to find food.” Bigger fish sought as prey by seabirds, for example, may dive deeper because the surface temperature of the ocean is too warm, she said.
There’s no single answer to the impact of changing climate on migrating birds, including changes in weather patterns. “In coastal areas there will be an increase in storms and that will influence populations sizes,” Cooper said. “That takes a huge toll on migrating species. They can use the wind to propel them north and south, but we may be seeing in the future increased storms and increased challenges for migratory birds.
“The biggest take home is we don’t know,” she said. “We are trying
to plan for the future.”
The good news for the Cordova area is that it has an intact ecosystem, which
makes that ecosystem more resilient to change, she said.
“By keeping our system here flowing there is more resiliency. There is no doubt that things are changing and will continue to change,” Cooper said. “The question is how much change can we adapt to and when can the species on our land no longer continue to adapt, and we don’t know where that breaking point is.”
“Many birds come to Alaska to breed and they come from far corners of the world,” said Handel, the USGS wildlife biologist. “Depending on how far they are coming they may use different cues to determine when they come. As daylight changes with the season the length of the day can trigger behavior in birds and other organisms,” she said. While changes in daylight times do not change from year to year, weather patterns may, and migrating birds don’t know what the weather will be when they arrive in Alaska.
“Some years have a warm spring; some years a colder spring,” she said.
“We try to understand what factors are influencing birds, but because things are changing so rapidly there is concern that birds might not be able to time their migration properly to arrive when the (food) resources) they need are at their peak.
“Some species that migrate from far away might have more difficulty with the timing (of their migration) than birds with shorter migration,” she said.
Unpredictable weather spells also may wreak havoc.
Some springs things get warmed up and then there is a cold snap, which creates an ecological trap, for example, for songbirds whose supply of insects for food may die off in the cold.
One thing these researchers all agree on is the need for continuous studies on the impacts of climate change on bird migration, particularly on the availability of food and other resources for the feathered travelers.
Under climate change, the timing of blooming vegetation or emergence of insects may be out of sync with the passage of migratory birds, Horton, Sheldon and Farnsworth noted in their report. Even subtle shifts could have a negative impact on the health of migratory birds.
In their future work, they said, they plan to expand their data analysis to include Alaska, where climate change is already having more serious impacts than in the lower 48 states.
