Author Archives: William Freedberg

About William Freedberg

Studies indicate that Will Freedberg occupies the ecological niche of a semi-nocturnal generalist. His habits change seasonally, doing fieldwork and bird surveys in the summer, but also blogging, coordinating volunteers, taking photos, and doing background research. Life history traits include growing up in Boston and reluctantly graduating from Yale College. Behavioral research shows that William occasionally migrates to the tropics to seek out Hoatzins, pangolins, and sloths, but mostly socializes with his age cohort in urbanized areas of eastern North America. He is short-sighted, slow to react, and a poor swimmer.

Help Us Learn About Bird-Window Strikes Downtown

Calling all citizen scientists near Boston!

Mass Audubon needs your help monitoring an underappreciated threat to migratory birds: window collisions. We’re looking for volunteers to collect data on bird-building collisions and rescue birds that survive a strike.

A Black-throated Green Warbler that died on migration from a window collision.

The Problem

Window collisions are a surprisingly significant source of bird mortality in the US, causing several hundred million casualties annually.

Birds struggle to distinguish reflections from reality, and often strike glass windows that reflect the sky or nearby greenery. City lights also confuse night-migrating birds, which use the stars to navigate, and which often land near sources of light pollution. Many window strikes occur as birds try to re-orient in the morning, after being drawn in to an unfamiliar concrete jungle.

How to Help

The Avian Collision Team (ACT) is a new volunteer initiative to get as much data as we can about building strikes in Boston. We want to understand the scale of the problem in Boston, where the trouble spots are, and which species are most affected.

The program runs from April 13–June 4. Volunteers need to sign up for 1-4 weekly shifts, Saturday–Tuesday, from 8 am to around 9 am.

We are looking for two kinds of volunteers:

1. Monitoring volunteers who will walk predetermined routes to collect deceased specimens, fill out data sheets, and occasionally rescue live birds.

2. Transport volunteers who can pick up specimens from monitors and bring them to a collection site at Harvard. Drivers will also bring occasional injured, live birds to Tufts Wildlife Clinic in Westborough as needed.

Similar programs have shown that in parts of some cities, there are practically no casualties. In others, certain buildings can kill a dozen birds a day during peak migration. Scientists have developed guidelines for what makes buildings especially dangerous to migrating birds, but they’re still pretty rough. The best way to know where and to what extent there’s a problem in Boston… is to check! 

If this sounds interesting, sign up here!

Birders’ Meeting 2019: Coming Up on 3/3!

While past iterations of the annual Massachusetts Birders’ Meeting have centered on specific groups of birds, habitats, or conservation issues, this year’s theme is a little more abstract: the beauty of birds. All of this year’s presentations address some aspect of what avian beauty means to us and to birds themselves.

Headlining this year’s meeting is Dr. Richard Prum, an evolutionary ornithologist working at Yale. Prum received a Pulitzer Prize nomination for his most recent book, The Evolution of Beauty: How Darwin’s Forgotten Theory of Mate Choice Shapes the Animal World—And Us.

Nathan Pieplow, a scholar of birdsong and author of the Peterson Field Guide to Bird Sounds, will share and discuss some remarkable audio from nature’s strangest-sounding birds. MIT professor Dr. Lorna Gibson will speak on the structure of feathers, from the microscopic forms that give them iridescent colors, to how feathers make owls silent and ducks waterproof.

Artists and humanists will also be among those speaking on avian beauty: Susan Edwards Richmond will give us a tour of bird-inspired poetry from the first known verse spoken in Hindi, to Shakespeare’s writings, and contemporary work by Mary Oliver and Gary Snyder. Mass Audubon’s Chris Leahy and Amy Montague will speak about birds’ many roles in visual art through the ages.

Additionally Joan Walsh, Mass Audubon Bertrand Chair of Natural History and Field Ornithology, will discuss how the fashion of the mid-1800s, namely bird plumes on hats, gave rise to the conservation movement.

Of course, there will be a number of other draws in addition to speakers. We’ll have a vendors’ area staffed by nature tour agencies, booksellers, and local bird-related companies. A number of raffle items will include field guides, bird feeders, and other birding goodies. Most importantly, there’s the chance to meet new community members, catch up with old friends, and stay up to date on news in the Massachusetts birding world.

Whether you come out to learn, socialize, or both, we hope you’ll join us this year!

This year’s meeting will take place on Sunday, March 3rd from 8am-4:30pm, at College of the Holy Cross in Worcester.

Rising Seas are Flooding Saltmarsh Sparrow Nests. Can They Adapt?

A recent study showed that Saltmarsh Sparrows choose nest sites based on past experiences. If a pair’s nest floods, for example, they’ll build their next on higher ground.

While this behavior might seem to show resilience to rising seas and climate change, the authors note that populations have still declined by over 75% since the 1980s.

In fact, nesting further away from the water a risky proposition for Saltmarsh Sparrows, and flooding is not the only threat to their nests. As with any species threatened by climate change, what appears to be a successful adaptation to environmental change often turns out to have unforeseen repercussions for the species.

A Saltmarsh Sparrow in the cordgrass (Spartina sp.) of a New England Marsh. Photo by Shawn Carey.

Caught Between a Fox and a Hard Place

Nesting further from the high-tide mark comes with trade-offs. Nests over drier ground are most vulnerable to predators, which are the second-greatest cause of nest failure in Saltmarsh Sparrows aside from flooding. Small carnivores like raccoons, foxes, and even snakes have been spotted feeding on Saltmarsh Sparrow chicks in nests far from the water’s edge.

Ticks, isopods, and other parasites also prefer drier nests. Some tidal flooding deters invertebrate pests, and may actually contribute to nestling survival as long as the nest isn’t completely inundated.

Nests are most likely to be successful in a narrow band near the high-tide mark where they are safe from predators, parasites, and flooding. Researchers found that Saltmarsh Sparrows that lost their nests to predators would re-nest closer to the waters’ edge, just as birds with flooded nests would move to higher ground. But as increasingly severe storms now regularly push spring tides past their normal height, they wash over what was once the “sweet spot” between safety from predators and safety from flooding.

So, even though Saltmarsh Sparrows adjust their behavior to manage risks, they’re still only resilient to mild disruptions like steady and gradual sea level rise. Regularly-occurring extreme floods, coupled with

Saltmarsh Sparrows are in Trouble

Climate threats to Saltmarsh Sparrows are borne out by the data. Their population is currently around 30,000 birds– half of what it was in 2010, and a shadow of the original population of 250,000. They continue to decline at around 9% annually nationwide, but in Massachusetts, careful management of saltmarshes has kept their numbers comparatively stable. 

Climate change is not the only issue facing Saltmarsh Sparrows. Over 1/3 of Massachusetts’ coastal wetlands have been developed. Dikes, railways, and other infrastructure disrupts the drainage of many remaining saltmarshes, raising the threshold for flooding but causing them to retain floodwaters for longer periods.

Mass Audubon continues to monitor Saltmarsh Sparrows in Massachusetts and advocate for the species, including submitting a proposal to list them as an Endangered species at the state level in 2017.

For tips on combating climate change, find out how to reduce your carbon footprint. For more information on Saltmarsh Sparrows, feel free to ask us a question in the comments!


A Birder’s First Christmas Bird Count

This is a guest post by Nick Tepper. A recent graduate from the University of Vermont, Nick is an up-and-coming expert on New England birds, a lifelong naturalist, and is currently fulfilling an AmeriCorps service year with Mass Audubon.

It was 5:30am on a frigid causeway in the middle of Lake Champlain– technically Colchester, VT, but we may as well have been in the Bering Sea given the arctic wind and cold. I remember stepping out of the car at our first site and walking the first steps of a two-mile icy bike path into the freshwater ocean. This was the inauspicious start to my first-ever Christmas Bird Count (CBC), in the winter of 2017. We could barely see, perhaps because the sun had not yet risen, or perhaps because of the 20mph winds that froze our eyelids shut. I spent the next hour or so shivering and trying to figure out what we were doing out there!  Why torture ourselves? Had we no self-respect?

Finally, the sun rose over the trees, and somehow in the –12-degree weather, it was warm. Looking towards the sunrise, we saw birds begin to appear in the dawn. A Snowy Owl was the first species we saw, glowing orange in the early light. What a moment to behold… its yellow eyes opening for seconds at a time to scan the lake for ducks, just as we did with our binoculars. That bird kept us warm all day. We ended up tallying 48 species, and I learned more about birding than I had in all my younger years memorizing plumage patterns, molts, and call notes.

A distant Snowy Owl perched on a block of ice in a watery, frozen marsh. Photo by William Freedberg.

Birding as defined by my first CBC was not a hobby, a job, or a passion— it was a mindset. More importantly, it is a mindset that people could share. If you participate in a CBC, you will inevitably make acquaintances, connections, and very likely some lifelong friends. For me, the best part of the CBC is that you do not need to be a seasoned birder to participate, you need only have an interest in birds and a pair of binoculars.

CBCs, Formerly Known As Christmas Bird Hunts

The Christmas Bird Count, now a grand tradition understood as an all-hands-on-deck census, was borne out of a more grisly 19th-century rite. CBCs were developed by conservation-minded ornithologists as replacements for a tradition known as the Christmas “Side Hunt.” Hunters would celebrate the season by taking “sides” after Christmas Day and filling the sky with bullets, with the goal of (quite literally) stacking up as many species as possible.

During the holiday season of 1900, noted ornithologist Frank M. Chapman piloted the idea for a Christmas Bird Census instead of a competitive hunt. On Christmas Day 1900, Chapman and 26 other counters pioneered 25 counts, counting 90 species. The count has since grown. Last year, 76,987 counters completed 2,585 counts internationally, tallying a total of 2,673 species! Even so, the CBC can always use more counters, and the birding community would love to have you along for the jolliest day of the year. 

Join Your Local Bird Count!

While some CBCs have already taken place, there are plenty more in Massachusetts before the year is up. Try getting in on one of the following:

  • The Concord CBC will take place on Sunday, December 30, and includes the towns of Concord,Lincoln, Acton, Maynard, Sudbury, and others.
  •  The Marshfield CBC is scheduled for Sunday, December 30 on the South Shore, and includes Marshfield, Duxbury, Hanover, and Pembroke.
  • The Newburyport CBC will take place next weekend on Sunday, December 23, and includes an abundance of saltmarsh habitats including Salisbury State Reservation, the famed Plum Island, and several towns on the North Shore.

Evening Grosbeaks Used To Be Common In MA. This year, They’re Back.

Just as ornithologists predicted, 2018 is shaping up to be a banner winter for a number of nomadic finches in the Northeast, especially Evening Grosbeaks. Having steadily declined as winter visitors since the 1970s, these predictably unpredictable birds are a welcome sight this year.

Evening Grosbeak (Creative Commons)

Irruption Years: Boom And Bust

Evening Grosbeaks, like several species of “winter finch”, rely on conifer seeds and berries whose yield in the wild (or “crop”) varies intensely from year to year. When cone and berry crops in certain areas of the boreal forest are strong, winter finches stay close to their breeding areas year-round. When cone and berry crops fail, winter finches become nomadic, sometimes moving hundreds of miles to the south and to lower elevations.

Even within the season, these birds move around a ton. After an historic number of Evening Grosbeak sightings this mid-November, things seem to have quieted down a bit. EBird records suggest that as many birds may have moved on from or even “overshot” Massachusetts and landed deeper into the mid-Atlantic.  This is unlikely to last though—new pulses of irruptive species will continue into the winter and there is still plenty of finch forage left in the trees.

Shifting Distributions

Misconceptions abound regarding Evening Grosbeaks’ status in Massachusetts, in part because this species’ distribution is in almost constant flux.

The last Breeding Bird Atlas showed these grosbeaks breeding in small but growing numbers in the western highlands of Massachusetts, despite a precipitous decline in winter observations statewide. Climate change is shifting the general range of this species northwards, and the prognosis for breeding grosbeaks in Massachusetts–which rely on climate-sensitive and declining conifer species– is grim. Indeed, eBird data suggest they may have already declined since the last atlas.

Birders who were around in the 1960s and 70s often fondly remember the times when Evening Grosbeaks were abundant every couple of winters. It’s a popular misconception that this species was naturally abundant in Massachusetts, and that climate change alone is responsible for their shifting status.

In fact, breeding Evening Grosbeaks were historically restricted to northwestern North America. Their population slowly advanced south and east during the latter half of the 19th century until a significant irruption brought them into the northeast in 1890. The 1890 irruption carried them as far east as Revere Beach, and in subsequent winters, the birds returned in larger and larger numbers. Nearly 14,000 Evening Grosbeaks were recorded in the 1972 Christmas Bird Count, but in the 1990s and 2000s, their winter range shifted away from Massachusetts dramatically– despite a modest increase in local breeders.

This Year’s Conditions

Winter finch irruptions do not only reflect a snapshot of food availability in the current year, but are affected by longer-term trends. For example, 2017 was an excellent year for cone crops in Manitoba, Ontario and Quebec, leading to increased reproductive success for seed-eating birds. This year, winter finch numbers are high as a result– in a year when food happens to be scarce.

This makes it a particularly good year to put out black-oil sunflower seeds, Evening Grosbeaks’ birdseed-of-choice. While many Evening Grosbeaks have been reported eating crabapples and ornamental tree fruits this winter, they’ve also been showing up in strong numbers at feeders.

Check out Your Great Outdoors for more information on this year’s winter finch irruption! 

Bald Eagle via USFWS

Rat Poison Is Killing Birds Of Prey, And People Are Finally Paying Attention

Note: this post contains an image of a dead Bald Eagle that some readers may find graphic.

Most rat poisons kill more than rats—they also pose a fatal threat to birds of prey. This topic recently made the news after a Bald Eagle on Cape Cod died of what appears to be rodenticide poisoning. The tragic story was picked up by several newspapers, and went locally viral on facebook.

This issue should not only get attention when a culturally iconic species like a Bald Eagle dies. Nearly every raptor species is vulnerable to rodenticide poisoning, from Eastern Screech-Owls to Red-tailed Hawks.

In fact, rodenticide poisoning is shockingly widespread. In one study, 86% of all raptors at a Massachusetts wildlife hospital tested positive for exposure to rat poison.

Second-generation rodenticides: the worst of a bad bunch

The EPA recently banned a class of rat poisons called second-generation anticoagulants from the consumer market, but licensed exterminators are still allowed to deploy them. The ban came about because of the 10,000 children annually admitted to emergency rooms for rat poison exposure. The ban certainly helps limit accidental ingestion by humans, but unfortunately doesn’t do much to prevent birds from eating poisoned rodents.

Second-generation anticoagulants don’t kill rodents immediately. While these rodenticides can kill rats with a single dose (which is why many consumers prefer them), poisoned rats can still live for a few days and continue eating poisoned bait. This delay means that rats can ingest enough poison to kill a much larger animal by the time they finally succumb. While any rodenticide can kill a raptor, second-generation anticoagulants are the most dangerous.

The aforementioned Bald Eagle on Cape Cod likely fell victim to this class of rodenticide. While vets at the Cape Wildlife Center are still waiting for test results to come back, the eagle was bleeding heavily, and its blood failed to form scabs or clots—a nearly sure sign of anticoagulant poisoning.

This Bald Eagle was admitted to Cape Wildlife Center, but sadly didn’t make it. Photo courtesy of Cape Wildlife Center.

Rats are a human-made problem

Native to Eurasia, brown rats have colonized much of the globe and become the most common urban rodent worldwide. These rats were among the first human-assisted invasive species, living aboard ships and rapidly spreading to other continents as early as the 15th century, much to the detriment of countless sensitive ecosystems. Rats and other rodents especially wreak havoc on species found only on small islands, and have driven several seabird species to extinction.

Rat populations are on the rise, and towns are struggling to keep up (the town of Belmont even had to close a city park over a recent rat infestation). Rodent control is sometimes critical to the health of a city or an ecosystem—so what are some poison-free ways to prevent or control rodent problems?

(Don’t) pick your poison

  • Prevention is the best cure for rodent problems. Rodent infestations only occur when there’s an easy source of food. Make sure your trash cans are scavenger-proof, cover vegetable gardens with net or wire, attach tree guards to the trunks of fruit trees.
  • Limit access to shelter and hiding places that appeal to rodents. Seal up holes in your attic, basement, crawl spaces, and shed, and remove tree limbs within three feet of your roof.
  • Consider alternatives to poison. The Tufts Wildlife Clininc points out, “People often believe poisons are more humane than snap traps, but an animal bleeding to death is neither quick nor especially humane.”
  • If a rodent problem has gotten out of hand and you choose to use an exterminator, try to pick one that practices “integrated pest management”— a multi-pronged approach that avoids chemical control methods.
  • Finally, call your town or city hall and ask how the local government addresses rodent control. Suggest eliminating rat poison if it hasn’t been done already!

 

Join Us In Costa Rica!

A Fiery-throated Hummingbird in central Costa Rica’s Talamanca Highlands. Photo by Will Freedberg.

This March, our Director of Conservation Science, Jeff Collins, is leading a group trip to Costa Rica. In addition to supporting Costa Rican ecotourism ventures, proceeds from the trip will go towards bird conservation projects at Mass Audubon.

Bird diversity in Costa Rica is higher than anywhere north of the Andes, but that’s not the country’s only draw. Read on for details on what makes Costa Rica such a unique destination for birders.

Costa Rica’s Conservation Legacy

Costa Rica’s commitment to conservation is one of the strongest of any country in the Americas, rivaling (and in many ways outdoing) that of the US and Canada.

In the 1980s, the government decided to bet on making conservation at least as much a priority as agriculture, extraction and development. The country invested in protected areas, sustainable livelihoods for rural communities, and reforestation programs that increased forest cover from 21% to 50% in a few decades.

Ecotourism is certainly the most-often cited economic benefit to come from these decisions, and indeed nearly 15% of the country’s GDP comes from tourism (and about half of that from ecotourism). But another major boon was the emergence of Costa Rica as a hub for tropical biology studies. The country’s high index of human development paired with its intact ecosystems have both attracted researchers and engaged the international community as well as developed Costa Rica’s now-booming national academe.

It’s no surprise, therefore, that some of the best birding areas that travelers will visit on this trip are famous research sites.

For example, La Selva Biological Station, the most prolific research site in the Americas, has yielded as many as 8 papers describing new species per week.  Carara National Park, which in addition to hosting over 430 bird species in just 20 square miles, also hosts important studies on tropical forest birds’ response to roads and development near protected areas.

The Birding

While the basic rhythm of forest birding is similar much of the world over, a few phenomena give birding the neotropics a very different “feel” than, say, New England.

Mixed-species foraging flocks feature prominently on most birding days. While mixed-species flocking is a global phenomenon, these aggregations reach epic proportions in Costa Rica. A quiet patch of forest turns into a birding bonanza when two dozen species of birds pass through over the course of a few minutes, each feeding according to their niche—tanagers plucking berries, warblers gleaning insects off leaves, and woodcreepers probing moss and debris on tree trunks.

Army ants often serve as the nucleus of a more specialized foraging flock: as the ants maraud across the forest floor searching for prey, they scare up insects, which in revealing themselves make easy prey for a host of understory birds. Finding an “antswarm” and an attendant cohort of skulking antbirds, antpittas, and flycatchers—all with a specific niche they fill in the feeding aggregation—can be a spectacular sight.

Leks, or cooperative mating displays, are another phenomenon rarely seen in the US (outside of the lekking grouse of the interior west). These are more predictable than feeding flocks—most leks have a fixed location in the forest where it’s easy to watch moonwalking Red-capped Manakins or the popcorn-like snapping displays of White-collared Manakins.

The Landscape

Costa Rica also stands apart from many other countries for packing in five major biogeographic regions within a couple hours’ drive of the capital:

  • The cloud forests of the high central cordillera, home to quetzals and most of the country’s endemics,
  • The dry northwest, low on bird diversity but famous for waterbirds at its seasonal wetlands,
  • The Caribbean foothills, famous for massive mixed-species flocks and some of the most enigmatic species in the country, like Snowcaps and Black-crowned Gnatpittas,
  • The rainy and humid Caribbean lowlands, where species richness peaks for birds, and charismatic species like Keel-billed Toucans and Great Green Macaws are easy finds,
  • The equally wet South Pacific lowlands, Costa Rica’s most unique biome with a completely different suite of rainforest species from the Caribbean, including incomparable Turquoise Cotingas and Scarlet Macaws.

Our upcoming short trip focuses on the latter three ecoregions. There is simply too much ground to cover in Costa Rica without spending several weeks there!

If you have any questions about the trip, get in touch with our travel office, or register here.

 

 

November Is Western Vagrants Month: 6 Species To Watch For

Every November, most migratory birds of the American West are on their way south, but a handful always end up in New England. While it might seem surprising to find a Western Kingbird along the chilly Massachusetts coastline, it can be fairly easy to predict which weather conditions will bring a small wave of western vagrants into the Northeast.

Fronts and storms are key, especially those bringing winds from the southwest. After the breeding season, some migratory species disperse in seemingly random, weather-dependent ways before continuing to the tropics. Additionally, most populations of migratory birds include a few individuals born without their cohort’s navigational abilities. These birds with “reversed compasses” often migrate irregularly during their first year of life.

These vagrants can show up anywhere, but there are a few tricks to looking for them. Watch the weather, and go birding a few days to a week after strong southwesterly winds. Seek out edge habitats, bodies of water, and potential sources of food— like thickets of late-season berries, or low and sheltered areas near coastlines where flying insects persist later into the fall.

The past few weeks have been a promising lead-up to western rarity season, with Cave Swallows already appearing on the South Shore, and a Say’s Phoebe seen in Barre in mid-October.

Right now, conditions look fairly promising—winds over the dry interior of the US are blowing strongly from the northwest, but they connect with two large cyclonic storms moving northeast. Following that, forecasters call for strong southwest winds. It will be interesting to see whether or not the upcoming storm system leaves any vagrants in its wake, and in all likelihood, it will.

 

 

Here are some species to stay on the lookout for:

  1. Cave Swallow: These small birds of the south-central US and Caribbean have begun to show up like clockwork. They arrive almost exclusively at coastal sites after strong pulses of southwest winds, and in recent years, there have been numerous annual sightings several birds at once. The phenomenon of Cave Swallows showing up in the Northeast is fairly new. Cave Swallows were extremely rare in Massachusetts before the last decade or so.
  1. Ash-throated Flycatcher: These also used to be much less frequent, but in recent years, have been showing up every 1-2 years at coastal sites. A couple have been seen a few miles inland at open, brushy sites like Drumlin Farm in Lincoln and Danehy Park in Cambridge, but with less regularity.
  1. Western Tanager: Roughly the same patterns as Ash-throated Flycatcher, but with more inland records.
  1. MacGillivray’s Warbler: One or several show up about every other year. They are mostly detected in farm fields and suburban thickets . Most sightings are from November, though a few exist from the Cape and South Coast regions in the early fall or late winter.
  1. Mountain Bluebird. These only show up every 3-5 years, having been most recently seen in MA at Turner’s Falls Airport from November 13-16, 2016.
  1. Townsend’s Solitaire: Almost annually, some solitaires arrive in November and linger until at least midwinter. In Massachusetts, most records are from Cape Ann and Cape Cod, although there are many inland records from Connecticut, Vermont and New Hampshire.

There are plenty of other species that show up well outside of their range in November, from the annual Western Kingbird to the exceptionally rare Common Ground-Dove. Will you be the next Massachusetts birder to find one?

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Studying Forest Structure At Elm Hill

Our bird conservation staff spent the past week collecting data at Elm Hill Wildlife Sanctuary, our demonstration site for Foresters for the Birds. Since we’re using this site to show how responsible forest management can enrich bird habitat, we need before-and-after data to compare changes in vegetation and bird diversity.

Birds See Forests For The Trees

The physical structure of a forest directly affects which birds are found there. The amount of vegetation near the forest floor (or “understory”) changes whether or not the forest can host a whole suite species that nest near the ground, like Ovenbirds and Black-throated Blue Warblers. Forests with open midstories (the layer of vegetation between 5–50 feet off the ground) attract flycatching birds like Eastern Wood-Pewees, but dense midstories appeal to Wood Thrushes and Canada Warblers.

The goal of our work at Elm Hill is to demonstrate how every forest species has its own habitat preferences, and how thoughtful land management can create habitat for declining species. Since three quarters of Massachusetts’ forests are in private hands, it’s critical to make these lands as hospitable as possible to wildlife.

Collecting Vegetation Data

A data sheet we use for recording information about trees and forest structure at Elm Hill.

Before we alter any habitat at Elm Hill, we’re recording these factors at sites where we’ve previously done bird surveys:

  • Total woody biomass (i.e., the average size and number of trees in a given area)
  • Tree species makeup (i.e., which trees are there, and how many of each)
  • Canopy density (i.e., the amount of cover provided by leaves in the treetops)
  • Sapling density (i.e., the number of young trees from around 1–6 feet tall)
  • Coarse woody debris (i.e., the number of logs and slash piles on the ground)

We outline a 400-square-meter plot with ropes at every site to make sure we collect data from the same area of land each time. This works pretty well until somebody tangles the ropes:

Jeff tangled the ropes. It definitely was not me.

While measuring trees, logs, and saplings is straightforward, you might wonder how researchers measure canopy density— and the instrument for this is quite cool. A spherical densiometer (pictured below) condenses a wide view of the canopy into a small image (much like a fisheye camera lens) with a grid over it. By estimating the percentage of each grid square occupied by leaves or trunks (and adding them up, and taking readings in each cardinal direction), we have a standardized and simple way of measuring canopy density. This also works as a proxy for determining how much light reaches the forest floor.

A spherical densiometer, used for measuring the amount of leaves in the treetops.

Long-term Goals

After foresters have cleared the woods of invasive species and created a variety of spatial habitat types, we’ll be able to show what changes this brings to Elm Hill’s bird species.

Elm Hill contains mostly 70–90-year-old forest, like much of Massachusetts. We’ll manage parts of the sanctuary for birds that prefer young forest, which are in trouble statewide, and in other part’s we’ll try to mimic old-growth forest conditions, which would take over a century to emerge naturally. Hopefully, we can then use this site as a physical example of how foresters and landowners can improve bird habitat on the properties they manage.

 

 

Cities Need Bird-Friendly Buildings

Between 100 million and 1 billion birds die annually from collisions with windows. Glass windowpanes can reflect nearby trees, shrubs, and sky. Birds’ eyes aren’t able to distinguish clear reflections from the real thing, so they sometimes aim for a reflection and fly smack into a pane of glass.

Earlier this year, Mass Audubon’s advocacy team expressed concern about a plan to install an all-glass façade on a building facing Post Office Square in Boston. An island of green in downtown’s sea of concrete, Post Office Square is a locally important stopover site for migratory birds. A few plantings in the middle of a nearly treeless part of the city attracts a surprising diversity of species, and adding a wall of glass panels across from one side of the park increases the risk of collisions . The well-meaning developer wanted to add a perimeter garden and a green roof to the site, which ironically would increase window strikes by attracting birds to reflections of the greenery.

Luckily, when told about the risk the project posed for birds, this developer was willing to make the site safer. They are in the process of installing glass with non-reflective stripes, which will break up reflections of what’s outside and steer birds away from the windows. Many similar technologies exist to make windows visible obstacles to birds without interfering with peoples’ view—from glass incorporating ultraviolet patterns that only birds can see, to entire panes made of non-reflective material.

Post Office Square, an urban stopover site for migrating birds (Photo by Will Freedberg)

You Can Help!

Skyscrapers account for disproportionate numbers of bird deaths, but the number of single-story buildings in the US make them an equally important front for reducing window strikes. Every homeowner interested in conservation can take steps to make their homes safer for birds:

  1. Keeping window screens on year-round. This is a great option because it provides a visual barrier as well as soft, springy physical barrier to incoming birds.
  2. Purchase and apply a one-way, see-through film to your windows, which both cuts reflections for birds and blocks the view into your home from outside.
  3. Finally, any birdfeeders close to your house (within 15 feet) should be even closer to windows (less than 1.5 feet away). While this sounds weird, birds do slow down before perching, so any window collisions as a bird comes in to land at your feeder is unlikely to injure the bird.

 

 

 

 

 

 

 

References: Daniel Klem, 1990: Collisions Between Birds And Windows: Mortality And Prevention