Chemical Clues Help Track Migratory Birds

Photo © Will Freedberg 2016

Where did this Scarlet Tanager spend the winter? A birder might correctly say “South America,” but where specifically? How can we know the country, the province, the latitude and longitude?

In fact, chemical signatures in feathers, blood, and muscle tissue tell the story of where a bird has been, and what it’s been eating. Over the past couple of decades, ornithologists and chemists have learned how to read into birds’ life histories by analyzing the isotopes that have built up in its body.

What’s An Isotope?

An isotope is just a lighter or heavier-than-normal atom of a given element (like hydrogen, carbon, or nitrogen).

Two kinds of particles contribute to an atom’s mass: protons and neutrons. Most atoms of any element have the same mass because they share the same number of protons and neutrons. While the number of protons in an atom define its identity and properties, adding a neutron to an atom rarely changes its behavior (other than its mass). For example, a bird will suffer no ill effects if a bird’s body contains an abnormal ratio of carbon 13 to carbon 12 (that is, “normal” carbon versus heaviercarbon with an extra neutron).

“You Are What You Eat”

Like any living beings, birds incorporate nutrients from their food into their bodies as they grow. The atoms in these nutrients, some of which will end up in a growing bird’s flesh and blood, exist in different isotopes depending on a variety of factors.  Some isotopes are more common at certain latitudes, or in certain groups of plants, or at a certain level of the food chain. So, a bird’s body will contain different proportions isotopes depending on its location and diet. By analyzing the ratio of one isotope to another in a bird’s body, scientists get an idea of where individual bird is from and what it’s been eating.

Advantages To Isotope Studies: Scale And Cost

Isotopes are particularly useful in long-term or large-scale studies. Isotope analysis ismuch cheaper and often less invasive than attaching geolocators to migratory birds, many of which are too small to carry a transmitter (meaning someone must recapture the bird to recover tracking data).

Studying isotope ratios in natural history museum specimens also provides unique historical perspective on how birds’ diets or ranges have changed over time.

In the next post, we’ll go over a few studies that have used isotopes to track long-term changes in bird diet or established where populations of breeding birds overwinter. Stay tuned!

 

 

 

 

In Pictures: A Time When Dead Birds Were High Fashion

After Mass Audubon’s founders curtailed the trend of decking out ladies’ hats with entire birds, many bird-adorned fashion items fell into disuse. Local activism made wearing plumes socially unacceptable, and many people donated their avian accessories to Mass Audubon. These donations quickly accrued into a large historical collection.

It’s sobering to imagine how these feathers and hat ornaments were harvested. Take egret plumes, for example, which make up the bulk of Mass Audubon’s collection of hat-related (or “millinery”) items. Because egrets only grow their most extravagant feathers (called “aigrettes”) during a short part of the breeding season, most were shot while on nests. The deaths of their chicks make the millinery trade in birds seem even more wasteful.

Although most activism around the feather trade focused on its impact on America’s avifauna, the Mass Audubon collection includes some surprising and uncommon birds from far-flung locales. For example, this Lesser Bird-of-Paradise head was collected in New Guinea before being attached to a hat, and eventually haphazardly removed:

This Magnificent Riflebird, also from New Guinea, met a similar fate. Only the lower beak and breast feathers remain.

Not everyone who took part in the bird ornament craze could afford the real thing, and many milliners cobbled together cheaper imitations of tropical birds from farmyard feathers- like this hat-topping “parrot” made of pheasant plumes.

Or this cap made from a mishmash of upland game birds:

Some items in the collection have nothing to do with hats. This “feather painting” depicts a parrot, using feathers from the real thing:

Wild bird feathers were also valuable for use as handwarmers, like this ornate muff made from grebe feathers.

For decades, this collection has been housed at Mass Audubon headquarters. It will soon be moved to a more state-of-the-art facility dedicated to housing historical objects and art, where it can be restored and used for research and public education.

You can learn more about Mass Audubon’s founders and the social history of bird conservation by downloading the article “Founding Mothers of Mass Audubon” here.

 

Partnerships for Plovers: Birdlife International and Mass Audubon

An endangered Piping Plover at one of Mass Audubon’s coastal sanctuaries. (Photo by Will Freedberg)

 

This year, Mass Audubon is partnering with BirdLife International to help coordinate migratory shorebird conservation across the hemisphere. By joining the Friends across the Flyway initiative, Mass Audubon can link up with conservation organizations along the Atlantic Flyway to protect species shared across borders.

 

Connectivity Counts

For birds whose ranges cross international borders, it’s crucial that regional conservation groups coordinate with each other. All threatened or endangered shorebirds in Massachusetts spend half the year in migration or at their wintering grounds. Every year, Piping Plovers, Red Knots, and Least Terns migrate to Mexico, the Bahamas, and even Argentina—and they depend on stopover habitats to feed and “refuel” along the way.

Removing just one link in this chain of habitats can spell the demise for an entire population. When making a conservation plan, biologists like to emphasize “habitat connectivity,” or keeping open routes between areas where a species lives. With New England’s shorebirds, this means more than preserving a physical link between protected areas—it means conserving breeding habitat in Massachusetts, wintering habitat in the Southern Hemisphere, and key stopover sites birds use while migrating in between.

 

How We Help In Massachusetts

Mass Audubon’s Coastal Waterbird Program approaches local shorebird conservation from all possible angles. Firstly, Mass Audubon puts boots on the ground—or rather, on the sand—to monitor shorebird populations and develop science-based conservation plans. Then, we work with local and state governments to put those plans into action. This includes setting goals for shorebird recovery, res-siting energy projects, and helping lawmakers identify beaches where shorebirds are threatened by offroad vehicles.

So far, the program has been a huge success! Piping Plover numbers have quintupled in Massachusetts since the program started in 1984.  American Oystercatchers, once a rare sight in our state, now number over 200 nesting pairs.

 

Partnerships Save Species

We’re excited that our Coastal Waterbird Program is linking up with BirdLife and its partners! This suite of organizations can pool resources to protect habitat and produce research on these shorebirds’ global needs. To learn more about Friends across the Flyway, check out BirdLife’s video on Rowan, the cute Red Knot.

Throwback Tuesday: Old And New Perspectives On Migration

Spring Migration: The Early Birders’ View

William Brewster, the famous 19th-century ornithologist and Cambridge resident, imagined that spring migrants preferred the rural countryside west of Boston to the woodlands near the city. But when he moved to Concord in 1892, he was surprised to find fewer migrants than he had become used to seeing in Cambridge.

Brewster’s student, Ludlow Griscom, hypothesized that this was the result of birds’ migratory routes. Brewster’s data, collected over decades, seemed to show that migrants did not move evenly across the state, but rather took routes based on the shape of the landscape.

Paraphrased, Griscom’s theory went like this: a big stream of birds passes up the mid-Atlantic coast, and two major contingents form in New York. One, with many inland migrants, would hit the Hudson river valley and follow it north, and the other would travel along the Connecticut coast. A small contingent of birds would then split off and follow the Housatonic River, and a major one would follow the Connecticut River Valley. The rest turn northeast just ahead of Narraganset Bay to avoid the pine barrens of southeastern Massachusetts and Cape Cod. These birds turn north near Boston Harbor, passing through Canton, Milton, Brookline and Cambridge, before continuing north into Essex County and along the New Hampshire coast.

Griscom and Brewster’s theory of migratory routes is roughly illustrated in this map:

Almost, But Not Quite

This particular set of routes has not been borne out by modern data gleaned from the radar. While some studies show that certain areas are regularly “birdier” than others during migration, (including sites along major river valleys), wind and weather patterns ultimately have more sway over bids’ trajectories than the topography of the landscape. Some expert birders still swear that migrating birds following “sight lines” or topographic features, but these observations remains anecdotal.

Even if migratory routes are not as fixed or as specific as Griscom imagined, radar does often show higher concentrations migrants in some areas than others. For example, in early May 2018, birds seemed to avoid southeastern Massachusetts and Boston, staying northwest of I-495. This is demonstrated on the radar maps below (note that the radar station is the white cross in the center of the circle, and that radar can detect birds equally in all directions- check out our blog series on reading radar images if you haven’t yet!)  Bear in mind that these are by no means typical nights—birds take very different migratory paths through Massachusetts every night, mostly depending on wind direction and time of year.

While the radar doesn’t show nocturnal migrants grouping together in narrow ribbons in the air, compiling images like these helps scientists observe patterns in bird migration. For example, this map by Kyle Horton of the Cornell Lab of Ornithology shows the direction in which birds are heading. The length of each bar shows how many birds are flying in that direction over the course of a season. The key takeaway: many birds fly over the ocean from Massachusetts, preferring to take the direct route over the Gulf of Maine rather than follow the coastline.

 

This map was recently featured in an awesome video by Jackson Childs, a local birder and friend of Mass Audubon. Check out Jackson’s video for more cool information about bird migration, including dawn flight, and some close-up footage of colorful warblers.

If you’ve found surprising patterns in spring migration, let us know in the comments!

 

 

 

 

 

 

 

 

 

 

 

Long Legs and Filmy Filigree: A Visit to Kettle Island

Colonial-nesting waterbirds are always fascinating, and because so many species nest on remote or hard-to-get-to islands, a visit to a colony typically represents an adventure.  And so it was when six intrepid staff members and volunteer bird counters visited Mass Audubon’s Kettle Island (a Massachusetts Important Bird Area) off the coast of Manchester-by-the-Sea last week.  A 17 acre uninhabited rocky island approximately a mile offshore, much of the island is vegetated with a dense cover of low trees, shrubs, thorns, and copious amounts of poison ivy. One can view the island’s birdlife from a boat, but landing is prohibited in order not to disturb this important colonial waterbird nesting site.

Kettle Island bird team ©Craig Gibson

The purpose of the island visit was to census and survey the breeding long-legged wading birds that have nested on the island for several decades.  The visit was part of a survey project initiated last year to assess the overall status and ecology of a number of islands off the Essex County coast, and also part of a greater coastal waterbird survey being jointly conducted by the U.S. Fish & Wildlife Service and Mass Wildlife.  One of the largest colonies in the Commonwealth, Kettle Island currently hosts Great Egrets (194 pairs), Snowy Egrets (99 pairs), Little Blue Herons (4 pairs), Black-crowned Night-Herons (30 pairs), and Glossy Ibises (9 pairs).  In addition, the island sanctuary is currently home to 2 pairs of American Oystercatchers, 51 pairs of Herring Gulls, and 79 pairs of Great Black-backed Gulls.

Little Blue Heron ©Craig Gibson

One of the magical aspects of visiting a breeding island at this season is seeing some of our most spectacular breeding species in their full breeding plumage—plumages that brought many species virtually to their knees in the heyday of the millinery trade during the late 1800s and early 1900s when their feathery filigree was central to the egregious fashion industry of the day.  Not only did the excesses of this worldwide feather lust bring the founding mothers of Mass Audubon to rise up in outrage in 1896, but it was this same excessive slaughter of egrets, herons, and other birds that ultimately led to the establishment of the Migratory Bird Treaty Act 100 years ago this year.

Great Egrets ©Craig Gibson

Thanks to these two historic conservation milestones, today bird watchers, photographers, artists, and everyone who enjoys beautiful living things is able to see these handsome species seasonally inhabiting the coastlines and salt marshes of Massachusetts when they are not nesting on their remote island colonies.

Great Egret chicks ©Craig Gibson

Please consider supporting our bird conservation work by making a donation today. Thank you!

Finding Your First Whip-poor-will

 

Photo by David Larson

A drab bird with a startling call, the Whip-poor-will’s perfect camouflage belies its incredible voice. This nocturnal hunter can broadcast its loud, rhythmic whistle as many as 10,000 times over the course of one night. Wherever Whip-poor-wills live, their sound is as much a part of a summer evening as the familiar chirp of crickets and the whirr of cicadas.

Where’d All The Whip-poor-wills Go?

“Whip-poor-will” is practically a household name. But far more people have heard of them than have actually heard their call. This is no accident—the species has been in trouble since the turn of the 20th century.

Whip-poor-wills’ decline has largely followed the decline of large moths, their favorite food. Recently, a landmark study showed that Whip-poor-wills and other insect-eating birds have been feeding on less and less nutritious prey, as their choices are diminished by pesticide use and habitat destruction.

The Key to Whip-poor-will Habitat

Whip-poor-wills have two main habitat requirements. Firstly, their preference for the largest insects means they require healthy ecosystems that can support Luna moths, Catocala moths, and big grasshoppers. Whip-poor-wills will avoid areas with urban or suburban development, or where pesticide spraying reduces the numbers of large insects. This does not mean that they are averse to open areas—Whip-poor-wills are often found in small agricultural fields, as long as there is little or no chemical disturbance.

Secondly, Whip-poor-wills avoid forests with thick understories and midstory vegetation. While they prefer habitats with some tree cover, they need an open midstory to snatch insects on the wing, and they need bare ground to perch. They are often found in open woodland like pine barrens, as well as small open areas near denser wooded ecosystems—but rarely, if ever, in large tracts of dense thickets.

Sites to Search for Whip-poor-wills

Most places in Massachusetts no longer fit the above criteria with the exceptions of the southeastern and central-west part of the state.

In Plymouth County, try driving the roads of Myles Standish State Forest just after dark.

On Cape Cod, the pine barrens of Wellfleet and Truro often have high densities of Whip-poor-wills; roads through pine barrens between route 6 and the Atlantic beaches are reliable, and even residential roads adjacent to pine barrens can be productive. Crane Wildlife Management Area on the upper cape is also great.

Closer to Boston, you’ll occasionally have luck in the Blue Hills Reservation and on ranger-led programs at Parker River National Wildlife Refuge on Plum Island (which closes at dusk).

Most places around Quabbin Reservoir and the wilder areas of the Connecticut River Valley are excellent for Whip-poor-wills, but few human observers look there at night. If you see a Whip-poor-will out there, report it on eBird, or let us know in the comments!

 

Predicting Spring Migration: Part 3

(This is the final installment in a series on birding by radar. Read the first and second post first so this one makes sense!)

On May 20, 2017, Bay-breasted Warblers seemed to drip from every tree at Mass Audubon’s Marblehead Neck Wildlife Sanctuary. Birders tallied dozens of this normally scarce migrant practically on arrival, alongside equally impressive numbers of Canada Warblers, Blackburnian Warblers, and other migrants. The air filled with high-pitched warbler songs so much that it was difficult to distinguish one from the next. Plum Island was equally loaded, with some observers tallying 123 species for the day. Was this a fallout, or just an excellent day for migration?

Fallout is one of the most exciting spectacles a birder can hope to experience in migration. Serious birders mistakenly use this term all the time to mean “a lot of migrants in one area,” but fallout refers to a very specific phenomenon: birds that cut short their migratory journey due to severe weather or exhaustion.

Birds will fall out along the coast if they are blown far off course over the ocean; they return to land hungry and tired, and large numbers feed at ground-level in coastal vegetation.  Fast-moving fronts of severe weather can also cause fallouts when they interrupt bands of migrating birds, and stationary fronts can stall migrants that land when they encounter it and build up along its edge.

On May 20th, 2017, birders who read the radar saw that northeastern Massachusetts experienced a borderline fallout; a storm had blown birds against the coast and over the ocean, but the weather cleared early enough that many grounded birds continued migrating afterwards. Regardless, the superb birding that day was undeniably predictable.

Reading the Radar on May 20, 2017

The radar for this night showed moderate migration, with a front of severe weather pushing birds south and east. The dense (green and red) precipitation is pictured up against a group of birds, represented by the blue line between the edge of the storm and the mass of birds in the center of the frame.

As the front moved east (see below), the density of migrants increased just to its south. The birds at the edge of the storm, pictured in blue above, appear to have been pushed into the main mass of birds, where they show up as a streak of green (higher-density) in the image below.

The velocity map below paints a slightly different picture. The black areas between the storm and the birds show that the storm is grounding birds. But the birds just away from the edge—that red spur in New Hampshire, for example—are not getting pushed south by it.

The red color (that is, increased relative velocity reading) of that patch of birds shows that they are either 1) continuing to fly east but increasing their speed or 2) flying north instead of east, as if to go around the storm, and maintaining their speed.  In either case, the fact that these birds are being detected further away from the station than the rest of the cluster indicates that they increased their flying altitude (recall that the further away birds are from the station, the higher they need to be to show up on the radar). It’s anybody’s guess why they would be doing this; the storm exists at a higher altitude than the birds, so flying up into it seems counterintuitive.

What Was Missing

Since the front passed fairly early in the evening, many migrants had a chance to pick themselves up and move along after the storm passed. It is not a reach to imagine that the birds that built up along the edge of the storm took off again after the storm passed, and moved northeast again, landing in similar areas along the Maine coast.

What Looked Promising

Storm or no storm, a forecast of west winds turning northwest at dawn is always a good sign for coastal sites. West winds blow inland migrants against the coast, where many prefer to land instead of flying over the water. Other birds overshoot the coast in strong winds, and when winds turn northwest at dawn, these ambitious flyers drop back in at coastal sites like Plum Island and Marblehead Neck.

The Results

A small but significant stream of birds poured off the ocean and onto the coast in the morning. Some experts say that this was strictly because they were pushed east by the storm, but some hold that these birds would have overshot the coast with the west wind anyway.  In either case, velocity readings from early (4:30-5:30) the next morning show many birds over the ocean colored in yellows, olives, and some blue: birds that are not moving directly away from or directly towards the radar station. In some areas, this means they were moving towards the coast.

Arrows on this map indicating bird direction were determined by drawing a line from the radar station (circled) out to a point with birds, and then drawing an arrow slightly over 90 degrees to this line for birds moving slightly away from the station (yellow).

Likewise, the arrow would be at exactly 90 degrees to the line for birds moving neither towards nor away from the station, slightly under 90 degrees to the line for birds moving slightly towards the station (light blues and greys) and in the direction (or close to it) of the line for birds moving strongly towards or away from the station (colored red or deep blue). If you didn’t follow this, don’t worry: the key is that birds over the water at dawn often means coastal fallout.

To sum it up, there were three elements of that evening’s radar that practically screamed “Go birding on the coast tomorrow”:

  1. Radar showing many birds moving more east than north, and some shooting over the coast at high speed
  2. A strong storm that could force migrants against the coast even more vigorously than the winds could, and might even ground many of them.
  3. Most importantly, birds coming in off the ocean early in the morning (4:30-5:30).

Lo and behold, it was an incredible day on the coast the following morning, even though arguments over how much the early-evening storm had to do with it remain unresolved.

This is just one example of how reading the radar can lead to better birding.  Try it for yourself this spring and see if you strike spring migrant gold!

Predicting Spring Migration: Part 2

Last week, we posted an article on predicting bird movements with radar.  Here’s what we went over:

—How birds show up on Doppler radar as solid, expanding circles of radar interference around radar stations, and why this happens

—How to tell these signals apart from precipitation or normal weather patterns

—How larger circles don’t necessarily mean more birds

This week, winds over Massachusetts are shifting. Steady southwest winds may bring a major influx of migrants as early as Tuesday night. So, here’s the rest of what you’ll need to know about watching birds on Doppler radar!

A Need For (Wind) Speed

it’s possible to see airborne objects’ speed relative to the ground using Doppler radar. Birds fly at about 10-15 knots, and know where they want to go. So, they’ll either be moving 10-15 knots faster than the wind if they’re flying in the same direction as the wind, or they’ll be moving in a different direction entirely. Other airborne objects, like insects or dust particles, will always move with the wind.

Here’s how to see the velocity for radar-detected objects online:

Go to the national website for radar data.

  1. In the top left, click on “0.5° Velocity”. (Selecting “reflectivity” will show you the density of the signal, but not the speed.  Velocity, on the other hand, won’t show you how thick the air is with birds—it will only show their speed).
  2. In the top right, go to the drop-down menu for “end time” to select the end time for the series of radar images you want to view. It’s in Universal Time, which is 4-5 hours ahead of Eastern Standard Time. Selecting “0500” is best if you want to look at last night’s migration, and selecting “most recent” is best if it’s the early nighttime and you want to see what birds are currently passing overhead.
  3. Go to the drop-down menu for “loop duration” and select 5 hours (or however long you want the series of radar images to be).
  4. Click on the letters “BOS” over Eastern Massachusetts to view radar images!

Image modified from the National Center for Atmospheric Research

In radar images, velocity is always measured relative to the radar station.  So, parts of a cluster of birds with “negative” velocity are moving towards the radar station, and parts of a cluster with positive velocity are moving away from it. The red areas in the image show movement away from the radar station (the dark dot drawn in the center of the image), from southwest to northeast. Blue areas show movement towards the radar station—also from southwest to northeast. Birds in the yellow, gray, and green areas are slower-moving relative to the station: as they pass by it, they are neither moving towards it nor away from it.

The wind was about 20kts (knots) from the southwest when this image was taken.  Since this radar signal shows objects moving NE around 35kts, it’s clear they aren’t just drifting with the wind.  These are bona fide birds!

To check wind speed and direction in your area (to compare to clusters of airborne objects on radar maps), try using Wind Map. Just click to zoom, and hover your cursor over Massachusetts to see the wind speed.

Where Will Airborne Migrants Land?

Velocity data can also tell us where birds are going to end up.  Birds usually migrate for between 5-7.5 hours a night, so multiplying their airspeed by around 6 gives us a very rough approximation of how far they’ll travel in one night. On most nights, this works out to be around 150-200 miles. This means that you can often get a general sense of how good the birding will be in Eastern MA based on early-evening images from Southern CT and New York.

For example, when there’s a big early-evening movement of birds over OKX (the radar station for Southern Connecticut and Long Island) and the radar velocity data show birds moving to the east or northeast, chances are that birding will be good in Eastern MA the following morning. If migrants are moving steadily due north, however, that can be a good sign to head further inland the next day.  Of course, it’s always best to check early-morning radar images as well—on some nights with north winds, migrants will pour in from the Atlantic Ocean right before dawn, making for great coastal birding.

In our next post, we’ll discuss radar images from the night before the best day of spring migration in 2017. It should serve as a case study in how watching the weather and radar can lead to encounters with incredible concentrations of migratory songbirds. Stay tuned!

Predicting Spring Migration: Part 1

If you ask birders what their favorite holiday is, a few will always smile and reply, “spring migration.” Protracted over several weeks, spring migration can indeed feel like a holiday, or at least an annual ritual: time off from work (to go birding), reconnecting with community (other birders), and seasonal gifts that nature drops off in our yards (in the form of colorful warblers).

For beginning birders, mornings in spring can feel as unpredictable as waking up on Christmas as a child to see what Santa brought. Migratory birds appear (or don’t) as if by magic, and the species differ from day to day. There’s no telling what a morning in May can bring. But birds are creatures of habit; with a few tricks, it’s easy to take the guesswork out of birding during spring migration.

Warblers Follow The Wind

West and Southwest winds bring us the greatest numbers of migrants, which would ordinarily move straight North from their Mid-Atlantic stopovers. In Westerly winds, warblers sometimes build up against the coast as they try to avoid being blown out over the water. When the wind is from the South, the Berkshires and Pioneer Valley hold more migrants.

Read the Radar

Doppler radar, mostly used by forecasters use to track weather patterns, also readily picks up signals from migrating birds. Radar works by emitting radio waves that are reflected back to the transmitting antenna by any objects in the way. It’s sensitive enough to detect droplets of water in the air, so it was no shock when ornithologists in the 1950s realized radar could pick up birds as well. Now, advanced birders as well as scientists rely on radar to understand birds’ mass movements at night.

A Brief Radar Primer

There are many ways of accessing radar data online, but the most beginner-friendly is Paul Hurtado’s bird radar website.  Just click on the date you want to see radar maps for and you’re good to go!

The most important part of reading the radar is distinguishing birds from weather patterns.  Rain or hail shows up as denser interference (represented on this map by green and yellow colors) in irregular, ragged shapes. Birds, on the other hand, appear on the map as distinct circles, and show up as lower-density (pictured on this map as blue and light blue). Hard to believe as it may be, most of what the radar is picking up in the image below are birds.

Visualization by Paul Hurtado; modified from www.pauljhurtado.com.

Why do these birds show up as clusters or circles around radar stations? Radar antennae point their beams up at an angle, creating a funnel-shaped zone of detection. Groups of migrating birds fly relatively low compared to rainclouds and so only pass through a circle-shaped cross-section of radar beams. Think of a cone-shaped searchlight- the lower down in the beam you go, the smaller its area is.

So, larger circles don’t mean more birds—they just mean birds flying higher up, where the radar beam is broader. (You can see in the image below that some of the blue circles have started to overlap). But more birds filling the sky will mean that more of the radar beam is reflected, creating a higher-density signal. Dense areas of migrating birds are represented by lighter blues and greens (see Texas and Maine on this map).

Stay Tuned For More

This is just the tip of the iceberg! There’s much more to learn. In a few days, we’ll follow up with a post on how radar can show birds’ speed and direction, and where they land after a long night migrating.  Subscribe to our blog to get part 2 in your inbox!

Why does the official Bird-a-thon checklist change over time?

In a word: Genetics. 

Bird names are not set in stone. Just ask the Rock Pigeon (formerly the Rock Dove). Depending on your birding experience, you may recognize other examples of species name changes: Thayer’s Gull to Iceland Gull, Rufous-sided Towhee to Eastern Towhee, and Northern Oriole to Baltimore Oriole.

Eastern Towhee used to be considered a subspecies of Rufous-sided. (Photo by Will Freedberg)

Some names change once, only to change again. For instance, the Black Scoter was formerly the Common Scoter, and the American Scoter before that. Perhaps the most complicated name changes come from the splitting of one species into two or three different species. Traill’s Flycatcher, for example, became Willow Flycatcher and Alder Flycatcher.

Just to make sure everyone is thoroughly confused, the ordering of species on avian lists is fluid as well: falcons used to be found with the hawks before they were evicted from the group, and Snow Buntings, which were once found near the finches, are now cozied up with the warblers.

The Rhyme and Reason

While these changes may seem arbitrary or like part of a nefarious arrangement between field guide publishers and the ornithological establishment, neither is the case. There are science-based reasons for periodic changes in bird names and in the ordering of species on avian checklists. Until the 1990s, birds were grouped and classified solely by the way they looked and behaved. Today, it is the genetic makeup, or genome, of a species that is considered more important in determining its origins and its relationship to other living birds.

As genetic relationships become more fully understood, it sometimes turns out that two different-looking “species” are not genetically distinct, or that populations of another “species” are in fact distantly related.  These revisions to bird classification are the most common reason for renaming. For instance, genetic (and other) research has determined that Eastern Towhees and Spotted Towhees represent a distinct pair of species, while the Solitary Vireo has actually been proven to represent three species masquerading as one (Blue-headed Vireo, Plumbeous Vireo, and Cassin’s Vireo)!

Behind the Curtain

Maintaining these changes is the responsibility of The American Ornithologists’ Union Committee on Classification and Nomenclature. The ornithologists comprising this checklist committee (the NACC) keep abreast of the classification and distribution of all the birds in North and Middle America in order to created standardized classification and nomenclature.

The NACC regularly produces supplemental changes to the latest edition of the Check-list of North American Birds. These are responsible for the periodic name and sequence changes Bird-a-thon birders will see on the event’s official checklist.

Thank you to our Bird-a-thon sponsors!

 

 

 

 

 

 

 

 

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