Category Archives: Research and Monitoring

Radio-detecting Migrating Birds at Drumlin Farm

Anyone can view a list of radio-tagged migratory birds in transit over Drumlin Farm Wildlife Sanctuary in Lincoln— and follow their next stops in real time. 

An antenna installed at the sanctuary earlier this summer is part of an international network of receivers (the Motus project) that detect tagged birds as they pass by, helping researchers trace individual migrations across continents.  

Fly-by-night Visitors 

So far this fall, the antenna has picked up some interesting species that began their journeys from as far away as the northern Canadian Maritimes and ended up in Florida and South America. 

Most birds that migrate long distances travel at night and feed during the day, making just a handful of stops on thousand-plus mile journeys. As expected, none of the birds stopped near Drumlin, taking just a few minutes in the middle of the night to pass through the area in which the antenna detect birds (about nine miles east-to-west—from the skies over Stow and Sudbury to Watertown and Arlington).  

The Cast of Characters 

Swainson’s Thrush (Photo: Anne Greene)

Four Swainson’s Thrushes were among the birds detected, all of which came from a group of 42 tagged in New Brunswick this summer. One bird took a leisurely journey after passing near Drumlin Farm, stopping five days later at a large wildlife refuge between Baltimore and Washington DC, and island-hopping around the coast of South Carolina two weeks afterwards. While Swainson’s Thrushes are a somewhat uncommon sight for birders in the Metro West area, they’re one of the most abundant species detected by people listening for nocturnal flight calls, suggesting that they pass overhead in larger numbers. 

Bobolink (Photo: Phil Doyle)

Bobolink also passed by under cover of night in late September. While Bobolinks breed in the fields at Drumlin (which Mass Audubon manages specifically for them), this individual was from a radio-tagging project based in Maine. It was detected on the DelMarVa peninsula a few days later, but wasn’t picked up by any receivers further south—suggesting it may have made a beeline to South America straight over the west Atlantic, or possibly died. 

Red Knot (Photo: A. Grigorenko)

One Red Knot, a species known for marathon migrations, set the most ambitious pace of any of the detected birds, passing through the Metro West area before it was detected just two days later by antennae in Tampa and Sanibel, Florida. Tag data from earlier in the year shows this bird spent five days in May of 2021 refueling and moving around the South Carolina coast before rocketing up through Pennsylvania and Toronto over another nonstop two-day journey. Eventually, the signal was lost in central Ontario, with the bird appearing to be on its way to the species’ breeding grounds in Hudson Bay.  

Visualizing Migration, Naming Threats 

Following pieces of these birds’ routes is more than an interesting and fun window into their world— it provides valuable clues to why some species are declining.  

Take Red Knots, for example. Researchers are already using Motus data to show how Red Knots’ reproductive success on their Canadian breeding grounds depends on how much food they can find at stopover sites in the Chesapeake Bay—where their preferred diet, horseshoe crab eggs, is dwindling due to overharvesting. 

Other studies have shed light on what stopover sites are most critical for migratory birds, or examine the impact of extreme weather, the overuse of certain pesticides, or other threats. 

Meanwhile, Mass Audubon and MassWildlife received a grant together in 2020 to track American Kestrels to their wintering grounds and see if mortality there might be driving their decline (although the pandemic put this work on hold until 2022). We’re also tracking local Barn Swallows— another declining open-country bird— during the summer months, to understand if they forage more successfully over native grassland than farm fields.  

A New Tool For Identifying Threats to Migratory Birds: the Motus Network

Across the US, conservationists are expanding a network of radio towers that automatically record the positions of radio-tagged birds as they pass nearby.

Data from this initiative, called the Motus network, is helping scientists understand what factors influence bird declines and what it will take to stop them. In mid-2021, Mass Audubon will use the Motus network to identify where threatened American Kestrels faces the most risks and mortality after leaving Massachusetts.

Here are some other examples of recent studies that have used nanotags to change how we understand bird migration—and specifically, how birds’ health during migration influences their survival and breeding success.  

Pit Stops can Make or Break a Gray-cheeked Thrush’s Migration

A Gray-cheeked Thrush on its nesting grounds on Kodiak Island. Image: Dave Menke/US Fish and Wildlife Service

One study used Motus stations to link how much weight Gray-cheeked Thrushes put on at stopover sites in Colombia with their migratory schedule (and, indirectly, to their breeding success).

Gray-cheeked Thrushes stop along Colombia’s coast on their journey from their wintering range further south to their breeding grounds in boreal Canada.  Massachusetts birders know them as an uncommon migrant on the ground, although their flight call is fairly frequently heard from night-migrating birds overhead.

This trend lines up with the Colombian study’s first surprising finding: many of these thrushes make direct, continuous flights to Canada from stopover sites in Colombia, instead of hopscotching through the Caribbean and North America. One bird averaged 46 miles per hour as it covered the 2100 miles between Ontario and Colombia in less than two days!

But not all thrushes have enough fat reserves to power them through these marathon flights.

Researchers analyzed the amount of fat thrushes packed on at their stopover sites, as well as the amount of time spent refueling. They found that the longer birds spent feeding on the north coast of Colombia, the earlier they arrived on their Canadian breeding grounds—allowing for a longer window to breed and raise young successfully.

Most interestingly, the researchers found that most thrushes arrived in Colombia with similar levels of fat reserves—suggesting that food availability on their Amazonian wintering grounds had less of an impact on their migratory success than their ability to refuel during stopovers in Colombia. This suggests that Gray-cheeked Thrushes face a bottleneck specifically in Colombia, and that conservation efforts [JA1] on their breeding grounds or wintering grounds could be weakened if their stopover sites are degraded.

Horseshoe Crab Eggs are Critical Fuel for Red Knots

Red Knots feeding on horseshoe crab eggs in Delaware Bay. Photo: Gregory Breese/USFWS

Conservationists have long been concerned about horseshoe crab harvesting along the Atlantic Coast and its effect on Red Knots, a chunky shorebird that feeds on horseshoe crab eggs during migration.

New evidence from a study of nanotagged knots validates concerns that food availability at one key stopover site influences their eventual success on the breeding grounds.

Some Red Knots were fat, healthy, and well-muscled at the time they were fitted with nanotags in Delaware Bay, which hosts more migrating knots than any other East Coast estuary. Motus receivers detected these birds leaving Delaware Bay on nights with favorable winds, which the birds rode nonstop to their breeding grounds.

Birds that failed to find as much food in the bay, however, left sooner— whether or not they had to fight the wind the whole way. These birds could be cutting their losses and giving up on feeding in the bay, the study authors speculate. Alternately, and perhaps more likely, these birds are aware that they weren’t in good enough shape to make a non-stop flight—and so leave earlier in order to arrive on time.

But that decision (whether conscious or not) came with a trade-off: by flying in poor conditions, these birds eroded their fat reserves even further. Because these birds had to fight the wind, the effect of malnourishment on the East Coast was magnified by the time they reached the Arctic.

Ultimately, the birds that showed up in poor condition to their breeding grounds also returned south before the breeding season was over—suggesting they had not been able to successfully raise young.

Pesticides Disrupt White-crowned Sparrows’ Journeys

Motus stations can also help track how tagged birds fare on migration after they’ve been exposed to an environmental hazard.

One study used geolocators to follow White-crowned Sparrows that had been exposed to seeds contaminated with a neonicotinoid, a class of pesticide widely implicated in some bird declines.

They found that while unexposed birds moved on after less than one day, birds that ingested a non-lethal dose of neonicotinoids—less than 1/10 of the amount present in a fully-coated seed—stuck around for an average of 3.5 days.

More worryingly, the birds lost weight. Within just 6 hours of ingesting contaminated seeds, the sparrows lost an average of 6% of their body weight. The loss deepened to 17% for birds that were exposed to neonicotinoids for three days straight. While these birds wree shown to eventually recover, these losses jeopardize White-crowned Sparrows chances of arriving on the breeding grounds with enough time to hatch and raise young.

Collaboration Is Key to Raising Motus Towers

While tracking birds with radio tags is not new technology, the Motus network dramatically expands its reach. Receiving stations across the continent can now pick up birds that would have previously only been detectable locally, either by a human carrying an antenna or by a single-site, stationary receiver.

This isn’t possible without a huge range of partners on public and private land who can host Motus stations, which now number nearly 1,000 across 31 countries. Mass Audubon is proud to be offering a few sanctuaries as potential sites for towers, and to be participating in the Northeast Motus Collaborative.

Abundant Deer are Bad News for Understory Birds

Human activity has caused white-tailed deer numbers to swell beyond sustainable levels in the Northeast, which spells trouble for birds that nest in the forest understory. At certain Mass Audubon sanctuaries, staff scientists monitor deer density to keep tabs on their ecosystem impacts.

Deer eat some birds out of house and home

Deer are “ecosystem engineers,” capable of changing the physical characteristics of their habitat by eating plants that grow low to the ground (aka understory). While a few deer per square mile can help plant diversity by creating gaps in the understory, much higher densities—often caused by an absence of natural predators—can spell trouble for plants and wildlife.

It only takes eight deer per square mile begin to reduce the number wildflowers, like trilliums and lady’s slippers. With wildflowers devoured, deer shift their diet to plants with tougher leaves, like birches, blueberry, and greenbrier. As deer thin out the forest understory and eventually remove it entirely, birds that normally rely on this vegetation to cover nests and raise young, like Ovenbirds and Black-and-white Warblers, struggle to persist. Even species that nest in the mid-levels of the forest, like Indigo Buntings and Yellow-billed Cuckoos, are affected when deer reduce the number of tree saplings.

Studies of protected areas show that nearly a third of migratory forest birds are more likely to disappear from forests with overabundant deer populations. It’s not just birds: more than 20 deer per square mile are enough to have severe impacts on bird, amphibian, insect, and mammal species diversity.

Heavily deer-browsed understory. The forest floor is mostly bare, with few low, leafy plants. Growing saplings are limited to species that deer don’t eat, like white pine.
In forests with fewer grazers, the forest floor is almost totally obscured by shrubs, grasses, ferns, and saplings that will grow into the canopy as older trees die.

Certain kinds of human disturbance help deer

Deer may never have lived as densely in Massachusetts as they do now. Wolves and mountain lions kept deer numbers in balance with their ecosystem until humans exterminated large predators from Massachusetts in the mid-1800s.

In the pre-colonial past, subsistence hunting also helped keep deer numbers in balance with the ecosystem. Sport and commercial hunting had nearly eliminated deer from Massachusetts in the mid-20th century, but their numbers began to bounce back as hunting declined—even though deer’s key predators were never allowed to return to the state.

In the meantime, suburbanization has created a nearly ideal landscape for deer in the Northeast. Suburbs mimic the patchwork of fields and forests that deer love, with open areas for nighttime feeding, sheltered woods for raising young, and landscaped backyards providing a steady supply of ornamental plants that are replaced as deer eat them.

Deer impacts endure

Even if the deer population crashes due to lack of food, disease, or a tough winter, their browsing has long-term impacts. Since deer avoid eating hay-scented fern, a plant that acidifies the soil, the fern can dominate the understory making it inhospitable to other plants. In addition, deer browse gives an advantage aggressive invasive plants with spines or thorns that deter grazing.

In the long term, over-browsed forests go into “regeneration debt,” which is when there are more mature trees than young saplings growing to replace them. Without sapling growth, the forest thins as more mature trees die. And since deer avoid eating some unpalatable saplings, especially pines and conifers, this eventually reduces diversity among mature trees as well.

Black-and-white Warblers require intact forests with a thick understory layer to breed. Photo: Davey Walters

How densely do deer live on Mass Audubon sanctuaries?

For the past several years, Mass Audubon scientists have employed a variety of methods to estimate deer density. Since 2018, deer monitoring has involved pellet counts and browse surveys at 16 of our sanctuaries.

Pellet counts take place in February and early March, after deer pellets have accumulated through the winter on the forest floor. Pellets decompose slowly because of the cold temperatures, and there isn’t much vegetation that can fall and accumulate on top of it. Browse surveys involve looking for deer impacts on plants, like nibbled-down twigs, to establish if deer are reducing tree regeneration or plant diversity.

Data from the 2020 season (which was interrupted by the pandemic) yielded deer densities ranging from 19 deer/mi2 at Elm Hill in Brookfield, to 31 deer/mi2 at Moose Hill in Sharon, to as many as 66 deer/mi2 at Daniel Webster in Marshfield. Some sanctuaries in Central and Western Mass, like Rutland Brook (Petersham) and Canoe Meadows (Pittsfield) have deer populations closer to the goal of 6-18 deer/mi2 suggested by state biologists.

To ensure that our properties are providing habitat for as many plant and animals as possible, Mass Audubon has implemented controlled, selective hunting programs during hunting season at sites where deer populations are growing unsustainably. After evaluating a variety of options for reducing deer density, we concluded that carefully managed hunting program is the only feasible and effective approach. We will continue to work with conservation partners and the state wildlife agency to maintain deer at appropriate densities so that our forest ecosystems continue to thrive. 

Coming Soon: Tracking American Kestrels with New Technology

Tracking migratory birds is getting much easier, thanks to the expansion of a continent-wide network of antennas that automatically receive signals from radio-tagged birds. This network, called the MOTUS network, enables scientists to use much lighter transmitters called nanotags, and study the movements of birds that are too small for older transmitter technology.

By tracking birds during migration, MOTUS data can answer a host of questions about bird biology and conservation—like where birds face the highest mortality, which habitats they rely on most during migration, and what determines whether they successfully reproduce. 

These are some of the questions Mass Audubon is trying to answer for migratory American Kestrels, which weigh only 4 ounces and are too small to carry most tracking tags. Kestrels have declined steeply across the state even as habitat loss has slowed, leaving apparently good-quality habitat unoccupied. Beginning in 2021, Mass Audubon will track Massachusetts-breeding kestrels with nanotags (or similar LifeTags) to see what happens to these birds on migration.

American Kestrel. Photo by John Flagg.

How MOTUS Nanotags Work

All nanotags give off bursts of signal on the same frequency, so any MOTUS antenna can detect any tag. To differentiate one tagged bird from another, each tag has a “signature” with different burst lengths, pauses, and spacing—almost like Morse code. When a tagged bird flies within about 9 miles of an antenna, the antenna picks up its signature and records the bird’s position on a connected computer.

Older tracking technology presented many challenges for studying small birds. Tags that transmit GPS data to a satellite are too heavy for most small birds, and there’s still no clear way to make them smaller. Plus, such satellite transmitters are very expensive. For many years, the only tags small and light enough to use on most small birds were less accurate, and required the recapture of any tagged individual in order to download stored location data.

Building a Nationwide Network of Receivers

MOTUS antennas are an improvement over older technologies, but only in areas where there are enough of them to detect birds as they pass through. Now, the focus is on creating rows, or “fencelines,” of evenly-spaced antennas to intercept birds as they pass by on migration.

One of these rows of antennae crosses Pennsylvania and parts of New York State, and soon, there’ll be additional MOTUS “fencelines” across inland areas of New England. Mass Audubon has proposed placing antennae at some of our sanctuaries, although coordinators of the New England MOTUS Collaborative will ultimately determine which sites make the most sense in terms of monitoring migrating animals.

When a city shut down, White-crowned Sparrows sang quieter, more complex songs

You may have heard it or even said it. “Nature is healing” has become a common refrain during the COVID-19 crisis, perhaps as a way to look for a bright side of a tragedy.

And while some examples are simply wishful thinking, like false stories of dolphins’ return to the canals of Venice, there is real evidence that less human disturbance during the pandemic changed how Californian White-crowned Sparrows sing.

A Eastern White-crowned Sparrow– a different subspecies than on the West Coast—at Ipswich River Wildlife Sanctuary

Less Noise, More Song

Researchers conducting a long-term study on White-crowned Sparrow songs saw an opportunity in the lull of a lockdown. Before the pandemic, the San Francisco-based team had studied how increases in city noise changed birds’ singing behavior. But this April, traffic noise fell to its lowest level since 1954.

In normal years, the researchers had found that White-crowned Sparrows compete with city noise by singing louder, higher-pitched, and simpler songs.

While simpler, louder songs rise above the hum of traffic, they come at a cost: males can’t sing both loudly and well. That disadvantages the fittest male White-crowned Sparrows, which advertise themselves with more complex songs. For females, which pick mates based on song quality, a city full of males shouting a limited series of notes curtails their ability to choose a good partner.

But just days after a stay-at-home order went into effect, urban sparrows reverted to singing the soft, complex songs of their rural counterparts.

The researchers found that their calls carried twice as far as before, both because of the varied tones of the song and because of lower ambient noise. And according to the team, males fight less over territory when they can hear each other’s songs from further away.

This study shows how quickly birds can return to natural behaviors after human disturbance are removed. Of course, there are many other kinds of human pressures on ecosystems that leave long-lasting or permanent effects– just not in this case.

So, if you think you heard more birds this summer during the pandemic, you might be on to something. Regardless of whether local birds change their singing behavior, less noise pollution probably means that we hear more birdsong– a thin silver lining in itself.

Good News Update: Barn Swallows Successfully Nested at Conte National Wildlife Refuge

Barn Swallows nesting at the Silvio O. Conte National Fish and Wildlife Refuge have had a successful season in 2020 in the Fort River Boat House. The full final report is available here.

Season Summary

We estimate that 30 – 38 pairs of Barn Swallows nested in the Fort River Boat House in 2020.

Of 98 adult swallows banded at Fort River in 2019, 27 were recaptured in 2020 (28%). This number is probably lower than the actual number present due to fewer banding days conducted this year during the pandemic. This return rate is similar to rates found in other studies of Barn Swallows. While a 28% return rate may not seem particularly high, remember that swallows banded in 2019 made two long migrations to and from South America before returning to breed in Massachusetts in 2020. And, because returning Barn Swallows don’t show perfect site fidelity, some individuals may have simply chosen to nest elsewhere in the area.

Young Barn Swallows (Photo by Richard Kramer)

This Success Informs Future Conservation Actions

Aging barns occupied by Barn Swallows are a common feature in New England’s historical agricultural landscape, and sometimes these structures simply cannot be saved. Thanks to the help of collaborator Andy French, project leader at the Conte Refuge, we have learned important lessons about how to attract and relocate Barn Swallows into alternative structures where they can be protected in cases where occupied barns must be removed. Some of the steps that were taken included:

  1. Collection of some nests after the breeding season to use in attracting swallows the following year to a different, more secure nesting location. A majority of nests built in 2020 were built on top of “seed” nests that had been harvested in 2019.
  2. Placement of nesting structures, hung from the Boat House rafters, to provide nesting sites. Some of these structures also included defecation screens that prevented swallow droppings from raining down on equipment below—an important consideration for private landowners who often have to deal with bird damage to their tractors and other farm equipment.
  3. Playback of Barn Swallow vocalizations was used in 2019 to advertise the availability of the Boat House site to pairs that were nesting in the nearby Bri Mar Stable. In 2020, we decided not to play audio recordings because Barn Swallows had already begun to move into the Boat House in 2019.

Next Steps for Aerial Insectivore Conservation

Mass Audubon also hopes to continue to contribute to a developing US Fish and Wildlife Service initiative aimed at conserving aerial insectivores (e.g., Barn Swallows, Cliff Swallows, Chimney Swifts, bats, etc.), pollinators that feed in fields and field edges, and grassland-nesting species in the Connecticut River Valley. If we are successful in securing funds, we hope to collaborate with the Conte Refuge in 2021 to deploy VHF nanotags on breeding Barn Swallows to learn more about the locations of important feeding areas with presumably healthy insect populations. This work would also include education activities, working with private landowners to maximize the conservation benefits associated with their farms, as well as conducting inventories of declining birds and other taxa. We’ll post more information about these efforts in future blogs.

Support our efforts to conserve Barn Swallows and other birds >

Be on the Beaver Lookout

Mass Audubon and the Boston NASA DEVELOP National Program team are collaborating to learn more about how Massachusetts beavers impact the landscape using satellite imagery, and we need your help.

The NASA DEVELOP National Program addresses environmental and public policy issues through interdisciplinary research projects, applying NASA Earth observations to community concerns around the globe. Teams of DEVELOP participants partner with decision-makers to conduct 10-week rapid feasibility projects, highlighting relevant applications of NASA Earth observing missions, cultivating advanced skills, and increasing understanding and use of NASA Earth science data and technology. The DEVELOP Program conducts 55-65 projects annually across 11 national locations. This spring, the DEVELOP Boston team is partnering with Mass Audubon to explore how beavers influence the Massachusetts landscape.

Beaver © Allison Bell

A Conservation Success Story 

The beaver (Castor canadensis) is North America’s largest native rodent. They are adapted for aquatic environments and easily recognizable by their long, flat tail and sharp front teeth.

European colonists found beaver’s thick, waterproof fur highly desirable and decimated their populations across the U.S. Unregulated trapping, deforestation, and the destruction of wetlands led to the local extinction of beavers in Massachusetts by the end of the 18th century.

In one of the most successful conservation efforts in U.S. history, New York reintroduced approximately 20 beavers from Canada and Yellowstone in 1904. By 1915, the population exploded to about 15,000 individuals and began to disperse to surrounding states. In 1928, beavers were discovered in West Stockbridge, the first recorded occurrence in Massachusetts since 1750.

To support Massachusetts populations, Mass Audubon’s Pleasant Valley Wildlife Sanctuary reintroduced three additional beavers in 1932. Today, beavers have been restored to nearly their entire historic range throughout the state, found everywhere except Cape Cod.

Busy Beavers Build Habitat

Beavers are known as ecological engineers. They alter and create new habitats by building dams from sticks and mud to create still, deep ponds. These ponds provide beavers with access to food, protection from land predators, and shelter.

Beaver Pond © Allison Bell

By building dams and creating ponds, beavers restore lost wetlands, of which about half have disappeared in the lower 48 states since European settlement. Beaver ponds are home to rich biodiversity, including amphibians, reptiles, spawning fish, muskrats, bats, various birds, and a wide variety of plants.

Altering the hydrology helps control downstream flooding, improve water quality, trap silt, and resupply groundwater. When the dam is abandoned and the pond drains, nutrient-rich silt creates highly productive meadows. However, beaver dams may cause unwanted flooding to neighboring properties, but can be mitigated through various solutions.

Tracking Beavers from Space and on the Ground

The spring 2020 Boston NASA DEVELOP team is using NASA satellite imagery to find and track beaver flooding events across Massachusetts to see how their populations are impacting landscapes. The team will be corroborating potential beaver flooding using iNaturalist beaver observations. iNaturalist is an online citizen science platform, where users upload and identify species observations (images or audio recordings).

Map showing beaver flood events at Wachusett Meadow & Broadmoor Wildlife Sanctuaries © Dr. Valerie Pasquarella, Boston University

How You Can Help

Help Mass Audubon and the NASA DEVELOP team by reporting beaver signs, including dams, lodges, chewed logs, or beaver themselves using iNaturalist, either in our sanctuaries or anywhere across Massachusetts.

https://static.inaturalist.org/photos/60714452/large.jpeg?1580660129
Beaver chewed tree at Ipswich River Wildlife Sanctuary reported on iNaturalist © Jennifer Clifford

Written by Cameron Piper, TerraCorps Service Member

Drumlin Farm is banding Massachusetts’ smallest owl – the Northern Saw-whet

A team of researchers measure the wing feathers on a Saw-whet owl at Drumlin Farm’s banding center. Handling owls is only legal with a government permit, and only by researchers trained to handle them safely.

Each year, Mass Audubon sanctuaries across the state set up banding stations to track Saw-whet owl migration. Drumlin Farm in Lincoln, Moose Hill in Sharon, and Daniel Webster in Marshfield all have dedicated crews of Saw-whet owl banders. November is the best time to find these tiny predators, as large numbers are passing through Massachusetts on their migration route.  

Saw-whets were an under-studied species 

At 7-8 inches long and weighing 2-5 ounces, Saw-whet owls are about the size of an American Robin. Because of their small size, Saw-whets are difficult to find. Many birders used to consider them a rarity, but in 1994 a study at Daniel Webster Wildlife Sanctuary revealed that these birds are much more widespread than previously thought. In fact, they are found in higher numbers than any other owl species in Massachusetts in the fall. 

Saw-whets are migratory 

Not only were these birds mistakenly thought to be a rarity, but they were also thought to be permanent residents. With anecdotal evidence as well as increased banding efforts, researchers have discovered that most of them do migrate, and can travel as far south as the Mexican border. Their migration routes, however, are less consistent and more unpredictable than other migrants, making them a complicated species to study.

A scientist holds a Saw-whet Owl with a “bander’s grip,” securing it’s talons in a way that’s safe and comfortable for both the bird and the human.

Banding efforts in the US 

In 1994, Project Owlnet was initiated as a way to bring together data from across the country and recruit new banding stations. Participating organizations share research and best practices to better understand these birds. The map below shows a map of owl banding stations that are a part of Project Owlnet. 

Mass Audubon sanctuaries contribute to this dataset by banding, weighing, and measuring Saw-whets. They also identify each bird’s age, sex, and take feather samples for DNA research. 

Fun fact: Saw-whet age can be determined with UV light 

The fluorescent color in young owl feathers comes from a pigment called “porphyrin,” which causes the feathers to appear red under UV lights. This pigment breaks down over time and exposure to light, so researchers can use this technique to identify an owl’s age. The pictures above show a second-year Saw-whet because they have clear pink hues in their newer primary feathers and on their coverts.  

Findings 

The map below shows banding stations in Massachusetts (yellow dots), Saw-whet owls from Massachusetts that were recaptured elsewhere (red dots), and Saw-whet owls banded elsewhere that were recaptured in Massachusetts (blue dots). Owls have been banded along their migratory route from as far north as Ontario and as far south as Maryland. 

Interested in seeing these owls for yourself? Join Mass Audubon at one of many upcoming nocturnal events. Happy owling! 

29% of America’s Birds Are Gone. What Are We Doing About It?

“Species extinctions have defined the global biodiversity crisis, but extinction begins with loss in abundance of individuals” —Rosenberg et al., Decline of the North American Avifauna (2019)

So begins the first comprehensive review of bird population trends since the mid-20th century. Summaries of the study are available via the New York Times and NPR.

The results were unequivocal: 76% of all bird species in the US are declining, some precipitously. Compiling on-the ground data from Breeding Bird Atlases revealed that the total number of birds in the US has fallen by 29% since 1970. Some groups fared worse than other over the five decades in question: shorebirds were down 37%, warblers were down by 33%, and aerial insectivores were down by 32%. And the total volume of birds in the sky, as detected by the national weather radar, was down 14% in the last ten years alone.

Rusty Blackbirds, an inconspicuous, clear-eyed relative of the more common Red-winged, underwent a population crash of over 93% over the past several decades. They are now rare enough that monitoring them is difficult.

This is bad news. Really bad news. But it’s possible to fight, and it’s even reversible. Scientists and conservation professionals have time-tested and proven strategies for stemming the tide of ecological decline, and the only obstacles are funding, public interest, and political will.

Mass Audubon continues to take a multi-pronged, species-specific approach to mitigate the damage in our state. Here are a few of the solutions we’ve already mobilized:

Habitat protection

Birds simply can’t exist without bird habitat. We protect 36,000 acres of bird habitat in Massachusetts through direct ownership, and another 6,000 through “conservation restrictions” and other legal protections against development.

We’ve recorded 149 species of bird breeding & raising their young on our wildlife sanctuaries– over two thirds of the total species in the state.

Landowner Partnerships

Where we can’t protect land through direct purchase, we find ways to ensure that it’s being used in bird-friendly ways. Many grassland species have healthy populations on agricultural land, and agricultural practices can make or break their prospects for survival. The same goes for forest birds living on land actively managed for timber; birds and forestry can coexist where sustainable practices are applied.

Mass Audubon encourages bird-friendly agriculture through projects like the Bobolink Project, incentivizing landowners to delay mowing hayfields until after Bobolinks and other grassland birds have completed nesting. The project compensates landowners directly for any profits lost due to delayed mowing, and the compensation fund is 100% donor-supported. In 2018, we saved more than 1,000 Bobolink fledglings from going under the mower.

Similarly, our Foresters for the Birds program pushes a bird-friendly approach to forestry in Massachusetts. One of our sanctuaries even acts as a demonstration site for how sustainable forestry and bird habitat go hand in hand.

Direct Habitat Management

Mass Audubon is directly responsible for managing between 40-50% of Piping Plovers (a federally Endangered species) in Massachusetts, a state with 1/3 of the Atlantic Coast population. We also are responsible for 20% of the state’s American Oystercatchers, and 40% of its Least Terns.

Since 1986, Piping Plovers have rebounded from 135 pairs to 680 pairs.

While the Cornell study showed shorebirds declining on a continental scale, conservationists in Massachusetts have known that shorebirds were in trouble since the middle of the last century. That’s why Mass Audubon developed our Coastal Waterbird Program to protect shorebirds through management, conservation, policy development, and education.

Science-based Advocacy

In the past year alone, Mass Audubon petitioned for three species to receive special legal protections from the state: Eastern Meadowlarks, Saltmarsh Sparrows, and American Kestrels. These petitions were based on our own monitoring of these species’ populations, which are in particular trouble and require intervention, as well as growing consensus among ornithologists.

We also speak up when legal frameworks for protecting birds are under attack. The rollback of the Migratory Bird Treaty Act last year was a major setback for bird conservation, and we spoke up.

Fight the decline with your donation today >

Field Notes: Southern Breeding Birds Are Moving North

“Whe-peet!” Hearing the explosive, snappy squeak of an Acadian Flycatcher at a Mass Audubon sanctuary would have been a huge surprise, were it not for the species’ ongoing shift northward into Massachusetts. Stumbling on this denizen of the American South used to be a downright rare occurrence here, but the northern edge of its summer range has advanced in fits and starts since the early 2000s.

When this particular bird was observed defending a territory at a sanctuary in Central Mass this summer, it was the first time it had been recorded as a likely breeder at a Mass Audubon property. Yet breaking the news in the Bird Conservation Department’s offices elicited mild enthusiasm and a hint of fatalism, with reactions ranging from “Cool!” to, “yeah, they’re comin’.”

Along with a few dozen other species, it seems this once-scarce visitor is on track to become a regular summer resident in a growing part of the state.

As Climate Changes, So Do Bird Ranges

Data from Mass Audubon’s first and second Breeding Bird Atlases showed an increase in breeding records of Acadian Flycatcher between 1974–2011.

Acadian Flycatchers are a naturally inconspicuous species, but other birds have made more dramatic entrances into Massachusetts. Red-bellied Woodpeckers are a loud, gaudy species of wet southeastern forests that have become downright common throughout southern New England. Northern Cardinals delighted birders in the middle of the 20th century as their brilliant reds and muted oranges became common sights in suburban yards and city parks.

A Red-bellied Woodpecker at a backyard feeder—in the dead of winter! Photo by Christine McCormack.

All of these range shifts have been thoroughly documented by scientists as well as casual birders. The most comprehensive effort to document these changes is coordinated by the National Ecological Observatory Network (NEON). Mass Audubon is NEON’s partner for bird data in New England, and every summer, our staff contribute bird censuses to NEON from across the region.

NEON treats birds as one piece of a vast puzzle: by studying how long-term ecological trends line up with each other, the project aims to parse out the causes and consequences of environmental change. Read more about our work with NEON in this blog post!

The Role Of Ecological Monitoring

Range shifts represent more than a curiosity to ornithologists. Rather, they are part of larger ecological disruptions caused by a warming climate and other human-caused factors like agricultural intensification, urbanization, and invasive species.

While a few species adapt to these changes and even benefit from them, they do spell trouble in the grand scheme of things. Niches go unfilled as some species’ ranges shift away from habitats they were once well-adapted to, leaving their home ecosystems in flux.  Other species’ ranges are limited by physical factors like elevation, or by the distributions of their competitors or their food source. Birds with finely-tuned ecological roles struggle to adapt to changing conditions, most bird species’ populations decline.

This makes keeping tabs on bird populations critical.

Conservationists first establish which species are declining or adapting (and why, and how) in order to target habitats to create or manage and prioritize species for legal protection.

This leads to concrete action, like advocating for the state to list acutely declining species as Endangered, or creating young-forest habitat at wildlife sanctuaries– all pieces of planning for a future with brave new ecological realities.