During a quiet mid-winter walk through Audubon’s Fisherville Brook Wildlife Refuge in Exeter, Scott Ruhren pointed out evidence that numerous creatures were still active despite the cold, evidence that would have been easy to miss if he hadn’t been paying close attention. A mouse had scampered across the trail and drew a straight line in the fresh snow as it dragged its tail. A deer had dug into the leaf litter beneath towering white pines in search of acorns or vegetation to nibble on. And a yellow-bellied sapsucker had recently drilled holes in the bark of a red pine, hoping for a meal of sap.
Ruhren, Audubon’s senior director of conservation, then noted a small group of chickadees calling in the distance, followed by the tapping sound made by a hairy woodpecker, and the distinctive nasal yank-yank call of a white-breasted nuthatch.
The nuthatch, a common backyard bird dressed mostly in gray-blue and white plumage, may no longer be so common in a few decades. In fact, it may even disappear from much of
Rhode Island during
the breeding season by the last quarter of this century. And the same is true
of the hairy woodpecker, which is already an uncommon species but one that
birdwatchers in Rhode Island can usually find in the state’s abundant forests. If
these species do disappear from the Ocean State in summer, the cause will likely
be climate change.
That’s the prediction made in a 2016 report by the National Audubon Society, which found that 314 bird species in North America – including 50 that call Rhode Island home for at least part of the year – will experience a shrinking and shifting of their breeding and wintering ranges, threatening nearly half of the country’s birds. Using data from hundreds of thousands of bird observations and a sophisticated climate model, the report predicted how bird populations will react to the changing climate. And the results were grim.
The white-breasted nuthatch, for instance, which is now found throughout most of the U.S. and Canada, is predicted to lose 79 percent of its summer range by 2080. It will no longer breed anywhere in the South and in few places in the Midwest and Mid-Atlantic States, except at high elevations in the Appalachian Mountains. The woodpecker is also expected to lose more than three-quarters of its breeding range. The reason, in both cases, is that the climatic conditions in which they prefer to breed – along with much of their preferred breeding habitat – will shift northward considerably as the Earth continues to warm. And that’s expected to be true for hundreds of other bird species as well, threatening many of them with extinction.
The changing climate, due largely to a build-up of carbon dioxide and other gases contained in industrial emissions, is expected to cause dramatic changes to the global environment. And it’s already happening. According to the National Oceanic and Atmospheric Administration, Rhode Island has already warmed more than 3 degrees Fahrenheit over the past century, and extreme precipitation events are on the rise. What’s more, sea level has already risen more than 9 inches since 1930, faster than the global average, and it is projected to increase another 1 to 4 feet by 2100.
These changes are certain to lead to considerable damage to the human built environment, as homes and businesses become flooded, destroyed by storms, or fall into the sea as the coastline erodes. The impact on wildlife, especially migratory birds, will be equally devastating.
Shifting and shrinking ranges aren’t the only impact that local bird populations will experience, however. According to ornithologist Charles Clarkson, who serves on the ASRI board of directors and coordinates the Rhode Island Breeding Bird Atlas, the changing climate is already causing what he calls a “phenological mismatch” between birds and the food they need to survive and reproduce.
“Birds go through an annual cycle of carefully timed events – when they breed, when they molt, when they migrate – which defines their phenology,” he explained. “The timing of these events is set by environmental cues that are now rapidly changing.”
Most birds feed on insects, he said. Because they are cold-blooded, insects emerge and become active each year based largely on the temperatures in the local environment. Birds, on the other hand, are warm-blooded and rely more on daylight length to trigger migration. But what happens when warming temperatures change the timing of the emergence of insects in Rhode Island and the birds wintering far to our south don’t get the message? Those birds may show up too late to take advantage of the insect abundance they need to fuel their breeding activities.
Clarkson said that short-distance migrants, like American robins and red-winged blackbirds, which mostly winter in the southern U.S., are probably able to fine tune the timing of their migration by picking up on local environmental cues. As a result, many of these species are arriving on their breeding grounds in Rhode Island earlier and earlier.
“They’ll be better able to acclimate to the more variable temperature regime, since they don’t move huge distances during the non-breeding season,” he said. “They’re able to shift the timing of migration so they’re not behind the curve on temperature and insect availability. They’re predicted to do better in the face of climate change.”
But long-distance migrants that winter in Central and South America will find that more difficult. They’re too far away to realize when Rhode Island is experiencing a warm winter or spring and shift the timing of their migration accordingly.
“If those birds are still en route to Rhode Island and miss the peak abundance of insects or fruiting and flowering plants, then they’ll be met with energetically expensive things like nest building, egg laying and feeding young but won’t have the energy to accomplish these things,” Clarkson said. “They’ll be out of step with the resources they rely on.”
He points to the cerulean warbler as a prime example. The population of this elegant Neotropical migrant is declining throughout its breeding range in the Great Plains, Midwest and
Northeast, and studies have shown that its reproductive success is tied to the
abundance of soft-bodied caterpillars.
“We know that the caterpillar bloom is coming earlier each year,” he said. “Knowing that they are so tightly tied to that resource, some of their population decline could be attributed to this phenological mismatch.”
Those bird species that succeed in avoiding the mismatch may actually benefit if they extend the length of their breeding season by a week or two by arriving earlier and departing later, providing them with greater opportunities to raise their broods.
A 2011 study by University of Rhode Island ornithologist Peter Paton, a member of the ASRI board of directors, found that some birds are already delaying their southbound migration in response to the changing climate. Based on data from birds captured between 1960 and 2007 at the Kingston Wildlife Research Station – which is owned by ASRI and operated by URI – he found that half of the short-distance migrants he analyzed and 38 percent of the long-distance migrants had delayed their migration by an average of 3 days per decade.
Beyond the warming temperatures and the concurrent shifts in bird ranges and migration timing, climate change is delivering other climate anomalies that are placing bird populations at additional risk. Melting glaciers and the thermal expansion of warming waters is causing sea levels to rise, for instance, reducing shoreline habitat and flooding salt marshes where numerous species have already been dwindling in number due to the loss of nesting habitat. (This topic will be examined in greater detail in the next issue of Audubon Report.) And the increasing severity of storms, particularly in the summer, has the potential to destroy a wide range of habitats and cause nesting failures from strong winds and heavy rains.
“Hurricanes come during biologically active periods of the year, so they have more of an impact because they happen during the breeding season and can wipe out entire nesting seasons,” explained Clarkson. “They can also destroy nesting habitat in one fell swoop that may be critical for the successful breeding of particular species. That habitat loss could be more damaging to a bird population than the failure of one nesting season.”
Back at Fisherville Brook, which protects the headwaters of the Queen River and encompasses an impressive variety of habitats, Scott Ruhren continued to point out signs of wildlife activity, like beaver dams, turkey tracks and the frozen vernal pools where wood frogs and spotted salamanders breed each spring. He also noted the numerous bird houses scattered around the property that provide nesting sites for bluebirds, tree swallows, purple martins, American kestrels and other species.
As he did so, he explained the important role that Fisherville and all of the other Audubon refuges play in mitigating climate change and supporting the needs of the region’s birds as they strive to adapt to the rapid changes.
“The most obvious thing we’re doing is managing the habitat where the birds live,” he said. “Without that habitat, there would be no birds.”
As a major landowner and land manager in the state, Audubon – through its refuges – helps to store carbon and other greenhouse gases by managing healthy forests and other ecosystems, reducing the buildup of the gases that are causing the climate to change. And the Society’s numerous wetlands not only protect biodiversity but also mitigate flooding during extreme storm events, which are expected to be more frequent in the years to come.
“Wetlands act like kidneys by taking in large quantities of water and then slowly releasing it,” he said. “During big storms, they may get flooded, but the water quickly recedes without causing damage. Wetlands also filter out contaminants that may accumulate from roadway run-off.”
Managing invasive species at Audubon refuges will also be increasingly important as the climate warms, particularly since few invasive plants and shrubs provide beneficial food or habitat for native birds.
“We know that poison ivy thrives in an enhanced CO2 environment and creates super poison ivy plants,” Ruhren said. “The same is true of other pest species. We’ll continue to work to reduce the impact that these species have on the environment and our bird life.
“Our eyes are also opening to what else to expect from climate change,” he added, “and we’re prepared to take whatever steps are necessary.”
Although it may feel that there is little an individual can do to reduce the effects of the changing climate, Charles Clarkson says there are steps that all of us can take to help birds manage the changes they are facing.
“Birds have three energetically expensive periods in their lives – molting, migrating and breeding,” he said. “Providing them with the resources to make any or all of those periods less costly is exceptionally important for a bird.”
Offering food to birds throughout the year helps them to have the necessary energy to molt and grow better feathers, which translates into a more efficient migration. Providing nest boxes, nesting materials, protection from predators and safe areas to raise their chicks reduces the energy they need during the demanding breeding season. In addition to maintaining bird feeders, Clarkson recommends planting native plants that provide food, cover and nesting materials; removing invasive species that compete with native plants and provide little value to wildlife; and managing your property for a diversity of habitat types.
“These are all things that will make the life of a bird easier,” he said. “Whether it translates into an easier breeding season or an easier molting period is irrelevant. If you can reduce their energy budget at any time in their lifecycle, you’re giving birds a leg up during these changing times and helping them be more successful.”
It’s the least we can do.
This article first appeared in Audubon Report in February 2017.