Published December 1, 2021
State of the Birds
Audubon Begins a New Chapter in Avian Research and Conservation
By Todd McLeish
Audubon Director of Avian Research Charles Clarkson (right) discusses field data with Audubon Council of Advisors member Steve Reinert. Image by Deirdre Robinson.
Much has been reported in the news in the last two years about the tremendous decline in bird populations around North America. Scientists say that the continent has about 3 billion fewer breeding birds than it did in 1970, and every ecosystem has been affected. Even species we consider to be common, like the popular Dark-eyed Junco, has had an estimated loss of about 175 million individuals from its population.
These statistics signal a broad crisis occurring throughout the natural world. If birds are in trouble, then so are many other groups of wildlife. And Rhode Island is not immune.
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Click the image to enlarge.
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But the news is not all bad. The results of the Rhode Island Breeding Bird Atlas, a five-year project to document the breeding distribution of every bird species that nests in the Ocean State, confirmed that 150 species breed here, just slightly less than were found during a similar effort in the 1980s. Led by Dr. Charles Clarkson, Audubon’s newly-appointed director of avian research, and with the help of 240 volunteers, the atlas divided the state into 165 blocks, each 10 square miles in size, to search every nook and cranny of Rhode Island and document what bird species breed in the state and where. It also collected data on wintering and migrating bird populations.
Among the most notable results, several species were found to be breeding in Rhode Island that were not documented during the previous atlas, including the Bald Eagle, Common Raven, Kentucky Warbler and Yellow-bellied Sapsucker. In addition, a number of other species have expanded their distribution in Rhode Island dramatically. Red-bellied Woodpeckers, for instance, expanded from 4 blocks to 149, an increase of more than 3,600 percent. Carolina Wrens and Pileated Woodpeckers also experienced significant expansions of their breeding range in the state since the first atlas.
The data on fall migration confirmed that large numbers of birds funnel through Rhode Island every autumn, mostly through the forested regions of the western part of the state. It also concluded that migrants amass along the coast and quickly move on. The winter atlas similarly documented the large populations of birds that are dependent on local habitats during the colder months.
“The good news is that Rhode Island has a wealth of avian diversity still. For a small state with a high human population density, Audubon and other land trusts and conservation groups have done an exceptional job of conserving open space,” said Clarkson. “What’s wonderful about that is that it presents an opportunity to utilize the data from the atlas to effectively manage those populations.
“Now we know where the birds are, the habitats they prefer, roughly how many individuals are breeding, and which species are wintering here,” he added. “Now we can apply what we know in the most effective way possible. We can ask additional questions on some species and focus conservation and land management on other species that are not doing so well.”
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Among those that are not doing so well – both locally and nationally – are the aerial insectivores, those species like swallows and swifts that feed exclusively on insects that they catch while they are flying. Although some species of aerial insectivores remain common, they aren’t nearly as common as they used to be. Bank Swallows, for example, have declined about 3.7 percent per year in Rhode Island since 1966, when Breeding Bird Surveys began, and Barn Swallow numbers have dropped 1.4 percent per year.
“There’s lots of conjecture about what’s causing these declines,” said Clarkson. “It could be the large-scale applications of pesticides, and climate change is probably adding to the problem as well.”
The changing climate is raising the prospect of what scientists call a phenological mismatch, when birds arrive either before or after the food they depend on is available in the quantities they require. The impact of this mismatch is affecting birds differently, depending on how far they migrate.
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Click the image to learn why Red-eyed Vireos may be bucking the population-decline trend! Image by Jason Major.
Red-eyed Vireo by Jason Major
Not every species of bird in the region is experiencing population declines. Red-eyed Vireos, in particular, are bucking the trend, even though no one can say why.
“The Red-eyed Vireo is an insect-eating species, and while we’ve seen declines among the bulk of other insect-eating birds, its population trend is increasing across most of its range in eastern North America,” said Clarkson. “The question is why and we don’t know. It’s one of those species for which more data needs to be collected.”
Data from the national Breeding Bird Survey, collected every year since 1966, has found no change in their abundance. And the Rhode Island Breeding Bird Atlas indicates that densities of Red-eyed Vireos in the Ocean State are as high as 277 individuals per square kilometer, meaning the state’s population is greater than 188,000. The bird was confirmed breeding in 73 of 166 atlas blocks in the state, up from 39 blocks in the first atlas.
One potential explanation for why the vireos have not declined – even though most species that eat the same food and live in the same habitat are in trouble – has to do with mercury.
“Small songbirds that eat insects accumulate mercury in their tissues, and mercury has a detrimental effect on their physiology,” said Clarkson. “But Red-eyed Vireos haven’t experienced a change in their mercury levels over time. Rusty Blackbirds, for instance, had a 17-fold increase in mercury, but Red-eyed Vireos have had no change. That leads us to think that there must be some kind of relationship between mercury accumulation and overall decline.”
“If we experience warming earlier in a given year, the short-distance migrants are capable of detecting that signal and adjusting their arrival dates to coincide with the changes in the weather,” explained Clarkson. “But the long-distance migrants – the neotropical migrants like warblers, vireos and orioles – don’t recognize those changes and so are unable to adjust their arrival times, and they’re the ones that will experience the largest declines due to this phenological mismatch.”
Clarkson said that numerous studies have shown that the aerial insectivores are capable of beginning their migration early in response to the changing climate and arriving in the Northeast to initiate breeding earlier than usual. But that early arrival brings risks as well.
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Great Crested Flycatcher (GettyImages)
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“We’re also experiencing a more aberrant climate, with abnormal cold snaps early in the year, and even a single cold snap in spring can be enough to reduce the overall nesting success of a breeding swallow colony by a huge amount,” he said. “So, when the birds show up a little early, they’re more likely to experience a cold snap, which means that there will likely be no aerial insects available to them during those cold days. A single day without enough food to feed their nestlings is enough to have a dramatically negative effect on these birds.”
Clarkson also noted that bird species dependent on grassland habitat continue to face difficulties as that habitat declines. Grassland birds include such species as Bobolinks, meadowlarks, Savannah Sparrows and bob-whites, the latter of which appears to have been extirpated from Rhode Island as a breeding species. Early successional specialists – species that prefer shrubby areas with young trees before they mature into dense forest – are also threatened due to habitat loss. These species include Blue-winged and Prairie Warblers, Indigo Buntings, Eastern Towhees and Gray Catbirds.
“Just like has happened across most of eastern North America, declining agriculture tends to turn farm fields into mature forest.” said Clarkson. “The question is, do we manage lands for the creation and maintenance of grasslands and early successional habitats, or do we let them success into mature forest? We were a state that was nearly all forested prior to European settlement, and then much of Rhode Island was cleared for agriculture, and now it’s trending back toward forest again. While grassland and early successional species are in decline in Rhode Island, we need to also pay attention to what’s happening with them at a more regional scale.”
Clarkson will be conducting research and providing recommendations for managing habitat on Audubon’s properties – as well as other protected lands around the state - with a focus not just on Rhode Island birds but on the birds that are contributing to regional populations. In his new position at Audubon, he intends to also work with other birding and conservation groups around the Northeast to better understand how bird populations are trending throughout the region and focus efforts on supporting conservation efforts from a wider perspective.
“I also want to borrow an idea from Vermont Audubon that they call ‘responsibility birds,’” Clarkson said. “We need to acknowledge that some species of migrants have 90 percent of their global breeding population in the Northeast, and it’s our responsibility to ensure that conditions never get to the point where we have to be reactive in our conservation. We shouldn’t wait until things get bad before we start to work toward making things better for those species. We need to pay attention to what they need, where their hotspots of abundance are, and make sure the resources they depend on are available in perpetuity.”
The Great Crested Flycatcher is one example of a responsibility bird. It’s a long-distance migrant and the only member of its genus that breeds in the Northeast. Its population is currently stable, and it is considered a low conservation concern. But there are aspects of its biology that make it an ideal candidate for proactive management, including the fact that it nests in tree cavities.
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“Anything we can do now to ensure its continued success in Rhode Island is likely to require minimal conservation effort, whereas waiting until the species is in decline would likely result in large-scale conservation plans and lots of money and manpower,” said Clarkson.
“The key is to make sure that Audubon’s management and conservation efforts for all species are multi-faceted,” he added. “There’s no one thing you can do to help bird populations. Management plans have to be multi-disciplinary and spread across various realms of research. You have to understand habitats, biochemistry, hydrology, climate change and other factors. All must be taken into consideration for every single species to achieve successful conservation.”
