Category Archives: Birds and Birding

The Saga of the “Robin Snipe”—An Artful Overview of an Atlantic Flyway Tragedy

The Red Knot (Calidris canutus) is a shorebird, roughly the size of an American Robin, and similarly colored in spring, with rusty red underparts and a ruddy brownish back sprinkled with black and calico. This species’ legacy has been punctuated by eras of superabundance, intense market hunting persecution, habitat disruption, and most recently anthropogenic events that have nearly brought the Atlantic flyway population to its knees. Favored sandy beaches on the South Shore of Cape Cod Bay and outer Cape Cod in Massachusetts have for many decades hosted great numbers of “Robin Snipes” (so-called by early market gunners) during their autumn migration en route to the far reaches of southern South America for the winter. And it was on these same Bay State beaches that the Atlantic population of knots was mercilessly persecuted from July-October during much of the 19th and early 20th century. 

Red Knot (Photo by A Grigorenko)

Fast forward to the last half of the 20th century when the ornithological community, initially in the Mid-Atlantic Coast region, began systematically registering measurable declines in the vast numbers of knots that once stopped on Massachusetts shores during autumn migration and on the shores of Delaware Bay in May. These early warnings presaged what was to become one of the most precipitous declines in modern shorebird history. The sad and well-documented chronicle of the near collapse of the eastern North American Red Knot population is one of the most dramatic sagas in modern-day bird conservation.

The pathos and intimate details of this ongoing conservation drama have recently been eloquently presented in Orion magazine by author and Audubon A awardee Deborah Cramer and artist Janet Essley. To explore the details of this fascinating story, follow this link >

Enjoying Nature From the Comfort of your Phone

While many of us are stuck at home, opportunities to explore nature are more limited.  However, there are many ways to engage with nature from your phone or computer, from sharpening your ID skills to submitting observations to a citizen science project. Below are five apps that will keep naturalists and non-naturalists engaged and excited.  

iNaturalist 

This app is like social media for nature sightings. The platform is designed to connect people to a community of wildlife and plant enthusiasts. Create a (free) account and upload photo (or audio) observations of living things. iNaturalist will give you its best guess based on your location and identifications of similar-looking species. Other users can comment on your observations and suggest an ID, which helps the program better identify future observations. Plus, iNaturalist observations can be scientifically useful: iNaturalist’s database has been used to redraw species range maps, and even describe new species.

Seek 

If you want to use iNaturalist’s identify tool without the rest of the app’s features, consider downloading Seek instead. This app has been described as “Shazam for nature” for its ability to ID a living thing by just pointing your camera.  

eBird  

This app is for bird-lovers and life-listers. Create “checklists” of any birds you see in a fixed location or on a walk. eBird tracks your distance and time and shows you a list of possible species based on your location. A half-moon orange circle notes uncommon species for the area and a red circle notes rare species.  

As with iNaturalist, eBird sightings become part of a database of millions of observations, helping scientists monitor large-scale patterns in bird populations.

Merlin Bird ID 

If you’re new to birding, consider downloading Merlin from the Cornell Lab of Ornithology. Browse a digital field guide of photos, bird sounds, and maps or answer five questions based on a bird you saw to have the app give you its best guess. 

Zooniverse 

Think of this app as digital volunteering. Instead of going out and monitoring nests, you can digitize historical nesting info (see below) that researchers at Cornell Lab of Ornithology will use for their database. Of course, this is only one of any citizen science projects on Zooniverse and topics range from nature to history and everything in between. The app will even track your progress, allowing you to see how much you’ve accomplished. 

Let us know if you decide to use any of these, have used them before, or have other recommendations for nature-based websites and apps you love! 

Looking for Love in All the Wrong Places: The Woodcocks of Alewife Reservation

American Woodcocks appear to be thriving at the Alewife Reservation in Cambridge, an urban wild sandwiched between office complexes and a subway garage. Despite the myriad dangers of city life, up to a dozen woodcocks perform their aerial mating displays over Alewife every March.

Resilience against the odds

Alewife is awash in threats to these hapless birds. Peregrine Falcons occasionally snag woodcocks in midair as they hunt along the clifflike walls of a brutalist-era parking garage. The expansive glass façade of the recently-expanded office park looms over the adjacent greenspace, causing fatal window collisions. Feral cats prowl around the urban wetland’s thickets. Heavy metals and pollutants from long ago still linger in the soil.

At Alewife, small patches of woodlands, wetlands, and fields persist amid urban infrastructure and new development.

And yet, at least a handful of woodcocks return here every year. In early spring, they give their explosive, nasal calls at dusk, leap into the sky, and twist and turn in midair to attract a mate. Once paired off, they nest and raise young in nearby woodlands.

Is it a trap?

It’s worth considering that this urban wild might be what’s known as an “population sink,” or “ecological trap.”

An ecological trap is any low-quality habitat where more birds die than can successfully reproduce, but which attracts birds even when there’s safer places for them nearby. Traps can appear to have a stable population of birds, when in fact most of those birds die before being replaced as more birds are lured in from safe areas.

A population sink, on the other hand, doesn’t necessarily attract birds more than areas with suitable habitat. Rather, birds end up there as “overflow,” when better territories are fully occupied or made inaccessible. Sinks don’t cause as steep declines, but do put a cap on the birds that can successfully reproduce in an area.

So, it’s entirely possible that Alewife isn’t doing the woodcock population any favors. No woodcock nests have been found in the area, but that doesn’t necessarily mean they’re failing to reproduce.

Brushy fields are all you need

Whether or not Alewife is a net plus or minus for its resident woodcocks, data from the rest of the country show that habitat availability is the main factor limiting woodcock abundance.

The strange, lumpy, long-billed form of an American Woodcock (Scolopax minor). Photo: Will Freedberg

Woodcocks love fields with low, woody brush, and adjacent mature forest. They display in springtime over open, grassy areas, but need some cover—ideally patches of shrubs or grass 2’-5’ high—for shelter. They use forest to forage during the rest of the year, especially when they’re raising young.

Without disturbance, either by fire, mowing, or agriculture, brushy fields revert to forest in a couple of decades. This is the story of woodcock habitat across Massachusetts: most ex-farmland has reverted to forest. Remaining fields are farmed more intensively, leaving less and less brushy patches and edge habitat, and fallow fields are becoming rarer.

Mass Audubon’s Foresters for the Birds program is emphasizing the value of young forest and shrubland habitat for birds. By educating foresters and landowners on bird-friendly forestry practices, we’re trying to create more habitat for woodcocks and other young forest specialists.

ACT Season 2 Wrap-up

The Avian Collision Team is a volunteer effort to monitor bird-window strikes in downtown Boston. This fall was the second season, running from early August to mid-October. Volunteers walked 7 survey routes from Saturday to Tuesday between 6 and 9 a.m., finding a total of 74 individuals. This makes 193 total strikes between the fall and spring seasons. 

The volunteer process

Birds that were alive but injured, which was about a quarter of the time, were taken to Tufts Cummings School of Veterinary Medicine to be rehabilitated and released. Those that were deceased were collected and donated to the Harvard Museum of Comparative Zoology’s Ornithology department to be used as study specimen. 

Note: Mass Audubon’s volunteers collect specimen with a permit from the Division of Fisheries and Wildlife. It is illegal to collect birds under the Migratory Bird Treaty Act.

A Commmon Yellowthroat outside of University Hall at UMass Boston

Table 1 shows a preliminary roundup of the window-strike species found by ACT volunteers. Locations and images can be found on iNaturalist, where other citizen scientists around the world are submitting similar window-strike data on a project called “Bird-window collisions”.  

Table 1: Number of individuals of each species found by ACT

White-throated Sparrow. . . 23 House Finch. . . . . . . . . . . . . . . . 3 Black-billed Cuckoo. . . . . . . . . 1
Ovenbird . . . . . . . . . . . . . . . 22 Northern Waterthrush. . . . . . . 3 Yellow-billed Cuckoo . . . . . . . 1
Common Yellowthroat . . . . 19 Blackpoll Warbler. . . . . . . . . . . 3 Red-eyed Vireo. . . . . . . . . . . . 1
Hermit Thrush . . . . . . . . . . . 7 Northern Flicker . . . . . . . . . . . . 2 Blue-headed Vireo . . . . . . . . . 1
Black-and-white Warbler. . 7 American Robin. . . . . . . . . . . . . 2 Blue Jay . . . . . . . . . . . . . . . . . . 1
Lincoln’s Sparrow . . . . . . . . 6 Song Sparrow. . . . . . . . . . . . . . 2 European Starling . . . . . . . . . . 1
Magnolia Warbler. . . . . . . . 5 Nashville Warbler. . . . . . . . . . . 2 Cedar Waxwing . . . . . . . . . . . 1
American Redstart . . . . . . . 5 Chestnut-sided Warbler. . . . . . 2 Veery . . . . . . . . . . . . . . . . . . . . 1
Brown Creeper . . . . . . . . . . 4 Black-throated Green Warbler 2 Chipping Sparrow. . . . . . . . . . 1
Golden-crowned Kinglet . . 4 Canada Warbler. . . . . . . . . . . . 2 Clay-colored Sparrow. . . . . .  . 1
Dark-eyed Junco . . . . . . . . . 4 Indigo Bunting. . . . . . . . . . . . . . 2 Swamp Sparrow . . . . . . . . . . . 1
Savannah Sparrow. . . . . . . 4 Virginia Rail. . . . . . . . . . . . . . . . 1 Pine Warbler. . . . . . . . . . . . . . 1
Northern Parula . . . . . . . . . 4 Belted Kingfisher. . . . . . . . . . . 1 Black-throated Blue Warbler 1
American Woodcock . . . . . 3 Yellow-bellied Sapsucker. . . . . 1 Palm Warbler. . . . . . . . . . .  . 1
Ruby-throated Hummingbird 3 Red-bellied Woodpecker . . . . 1 House Sparrow. . . . . . . . . . . 1
Mourning Dove . . . . . . . . . . . 3 Red-breasted Nuthatch. . . . . . 1 Brown-headed Cowbird . . . 1
Swainson’s Thrush . . . . . . . . . 3 White-breasted Nuthatch. . . . 1 Baltimore Oriole . . . . . . . . . 1

Note: This list is still being updated as we finalize our data

As evident in Table 1, window collisions in downtown Boston during the times in which we survey are primarily migratory species. Much like moths to a light bulb, migrating birds are drawn to city lights during their nighttime migratory journeys. They land in cities and in the early mornings when they re-orient themselves and look for food, they fly into glass windows. Learn more about this hazard and how you can do something about it on Mass Audubon’s website

A Lincoln’s Sparrow at the John Hancock Tower

ACT will start again during spring migration, running its third season from April 11 – June 2. Sign up to be a volunteer and direct questions to [email protected] 

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! 

Dial-a-Bird: A Tribute to the Voice of Audubon

Before the internet age, informational phone lines were widespread— providing everything from weather forecasts, time of day, or even local rare bird alerts.

Mass Audubon started the original bird hotline in 1954 with some help from a telecom executive, Henry Parker, who happened to be an avid birder.

In fact, the system that Parker developed for the Voice of Audubon came before the widespread use of phone hotlines. The Dictaphone-based system he gave Mass Audubon eventually became the basis for other users to pre-record airline schedules, theater showtimes, and other, more general-interest uses.

The rarities hotline, called “The Voice of Audubon” or VoA, reduced the need for staff to recite sightings to every birder who asked—making it as much a boon for Mass Audubon as for the hundreds of birders calling in each week.

Making the Papers

Shortly after its introduction, the Voice of Audubon was incorporated every week into a bird sightings column in the Boston Globe.

Initially, non-birder Globe interns had to transcribe the bulletin entirely by ear, leading to some amusing misspellings of bird names—such as “wobbling vireos” instead of “Warbling Vireos, “dowagers” instead of dowitchers,” “dick sizzles” instead of “Dickcissels,” and a “pair of green falcons” instead of a “Peregrine Falcon.” Eventually, a written transcript was made available to anyone interested in printing the week’s bird sightings.

A group of photographers respond to a report of a rarity, in this case a Great Gray Owl in southern New Hampshire. Always be respectful of vagrant birds– particularly owls and waterbirds– by not approaching them.

Changing Tastes

The Voice of Audubon became a wildly popular model, with similar call-in lines eventually cropping up in most US states. The nationwide rare bird alert even made it in the birding-centric Hollywood movie, The Big Year.

Email changed everything for birding hotlines. With the advent of the listserv, or email message board, call-ins to the Voice of Audubon began to decrease.

Listservs went out of vogue when eBird emerged on the scene, revolutionizing how birders reported their observations. Still, some preferred listservs for the opportunity to discuss sightings in addition to reporting them, for the way listserv conversations build community, and for the ease of reporting a sighting in text rather than via online form. These needs have also come to be addressed by Facebook groups for bird sightings, adding another medium vying for birders’ time and information.

Standing the Test of Time

Through it all, the Voice of Audubon has held firm as a resource for birders, even as it’s call-ins have declined since the heyday of the 1960s and 70s.

Continuing to publish the VoA serves a dual purpose. Firstly, it informs birders who don’t have access to a computer or who prefer the hotline format. Perhaps more importantly, its existence and regular publication in newspapers serves to raise the public profile of birdwatching among the general public.

Do you ever call the Voice of Audubon (781-259-8805), read it in the Sunday Globe, or check out the sightings on our website? Let us know in the comments!

Do Vagrant Birds Indicate a Changing Climate?

It’s been an incredible past few weeks for rare birds in Massachusetts. First, a Purple Gallinule showed up in Milton. Then a White-faced Ibis arrived in Sterling, and a Tropical Kingbird shocked birders in Belmont—the first ever to be seen in Middlesex County. Finally, the first Pacific-Slope Flycatcher seen anywhere in the state was spotted in Hadley, and a Western Kingbird and Rufous Hummingbird rounded out the glut of unusual visitors.

More than 2,000 miles from home, this boldly-colored Tropical Kingbird in Belmont made birding headlines.

It’s tempting to think that these out-of-range birds (or “vagrants”) are the result of climate change. Although climate change certainly affects species’ normal ranges, and may make vagrancy more common and extreme, it’s a reach to say that these “lost” birds themselves indicate any larger trends.

Instead, these birds are just as likely examples of species that only show in Massachusetts every several hundred years. This phenomenon of once-in-a-lifetime birds has plenty of precedent. Consider, for example, the first time a Masked Duck was seen in Massachusetts was in 1889—and the species hasn’t been reported in New England since. Similarly, the first and only record of a Brewer’s Sparrow was in 1873, and the first and only record of a White-tailed Kite was in 1910.

Vagrants: Unpredictable in Predictable Ways

As fall migration draws to a close, there’s almost always a spike in vagrant birds in Massachusetts. Birds from the interior southwest of the US ride winds blowing northeast, often making it as far as the coast.

Many bird populations contain a few individuals prone to wandering. In some cases, wanderers are biologically hard-wired to migrate differently than others of their species, and in other cases, the cause is unknown. These outliers aren’t unique to migratory species; even flightless penguins have been documented walking into the icy mountains of Antarctica, far from any food source.

Most vagrants either perish or (less often) make it back to their home ranges. Even if the vast majority of these birds don’t manage to reproduce on terra incognita, some scientists theorize that having a few exploratory or mis-oriented individuals gives the species an evolutionary advantage. This may allow a population to very occasionally colonize new, faraway areas that turn out to be hospitable, serving as a bulwark against sudden cataclysmic change across its entire normal range.

Climate Affects Vagrants, But Vagrants Aren’t Necessarily Climate Indicators

Fall isn’t the only time when wind patterns regularly bring Massachusetts a handful of unusual birds. Southern birds that overshoot their breeding grounds in spring are mostly the result of wind patterns that blow them far over the Atlantic, where they continue north until making landfall in New England. Even more noticeable are the hurricanes that have brought tropical seabirds like Sooty Terns and Red-billed Tropicbirds inland into Massachusetts.

As rising global temperatures create stronger storms and shift continental wind currents, it’s reasonable to think that new patterns in bird vagrancy will emerge. This doesn’t mean, however, that recent “firsts” (such as last month’s Pacific-slope Flycatcher or Tropical Kingbird) are indicators of climate change– especially with only 200 years of records and a long list of vagrants that showed up in the 18th century and never again.

Demonstrating an increase in vagrant birds (or changes in where they show up) is a tricky proposition, in part because there’s no good way to adjust for how many people are looking. Not only has the number of birders increased dramatically since the 19th century, but birders’ knowledge of how to predict vagrants has improved—and their interest in finding them has intensified. This complicates studying patterns in bird vagrancy, let alone linking them to long-term climate trends.

Fall is Social Season for Blue Jays

Fall holidays mean family gatherings – for people and for Blue Jays. Much like people, these highly social birds are more active in the fall, when the harvest is good and families are reuniting. This pattern is borne out by data on eBird, when observers’ Autumn checklists show a spike in sightings. Here are a few explanations for jays’ noisy behavior right now. 

Image: David Young

Predators on the move mean agitated birds 

When there is a predator nearby, many birds exhibit mobbing behavior to warn others of the threat. This means loud calling and erratic flight patterns. During migration, higher numbers of hawks, owls, and falcons may excite young jays and cause them to vocalize more frequently.  

Blue Jays have also been known to imitate hawk calls. Some researchers think this is a signal to their flock of a potential threat nearby. Others believe Blue Jays are cleverly trying to scare other birds away from their food source. Ross D. James, in a 2002 edition of Ontario Birds, theorizes that young birds learn raptor calls during periods of high stress and excitement and therefore will reproduce them under those same conditions.  

Acorns are plentiful  

Image: Peter Flood 

Every two to five years, Oak trees drop their acorns in much higher abundance than usual. These periods of higher acorn production are called “mast years” and greater Boston residents have taken notice. Fortunately for Blue Jays, who eat mostly seeds, this means lots and lots of food. They flock to areas with high densities of Oak trees, like many Massachusetts forests, and call out to their kin that they’ve hit the jackpot. 

Winter flocks are recruiting 

Blue Jays are winter residents in Massachusetts. Some individuals do migrate, but little is known about how or why they decide to do so. Families group together in large flocks starting in the fall. These flocks are constantly communicating potential threats and food sources since fledglings are still learning the ropes.  

One study of Blue Jays at Mass Audubon’s Wachusett Meadow Wildlife Sanctuary observed wintering jay groups of 14-49 individuals. These birds tended to stay in the same groups throughout the winter and in subsequent years.  

Image: Raina Aiello 

Have you noticed more Blue Jay activity lately? Let us know in the comments! 

Bird-a-thon and Southern Overshoots

Bird-a-thon, Mass Audubon’s annual competitive birding fundraiser, is fast approaching on May 10-11! Spring migration is heating up right on time for the big day– with a few surprises in the mix.

This year’s migration has been marked by an unusual number of southern species overshooting their breeding grounds and ending up in Massachusetts. These “southern overshoots” ride the winds to our state and only stay for a few days before returning to their normal ranges in the mid-Atlantic and southeast, but it’s fun to see them while they’re here!

The Slingshot Effect

Southern overshoots require more than just south winds over Massachusetts. Birds aiming for southerly climes only get a boost into our state when winds line up just right across the eastern seaboard in what’s called the “slingshot effect.”

This pattern starts with strong wind blowing birds offshore over Florida, the Gulf, or the Southeastern US. These birds normally return to land unless they meet a strong south-to-north air current over the ocean, which “slingshots” them northward until they meet the coast of New England. A heavy west wind over the entire mid-Atlantic region can also prevent them from returning to shore until they make landfall in our region.

Here are just a few of the species that rode “slingshot winds” up to Massachusetts in the past month, with maps comparing sightings from April 2018 with April 2019:

Summer Tanagers

Summer Tangers are birds of humid thickets in the southeastern US. Last April, none were reported in mainland Massachusetts. This year, two were seen in Plymouth, one on Plum Island, and a handful as far north as Maine!

Summer Tanager sightings – April 2018
Summer Tanager Sightings – April 2019

Hooded Warblers

Another bird prone to the “slingshot effect,” Hooded Warbler been unusually numerous this year, including late into the month. Here’s the same comparison between this and last April:

Hooded Warbler sightings – April 2018
Hooded Warbler sightings – April 2019

Blue Grosbeaks

Similarly, last April produced just two reports of Blue Grosbeak, a grassland bird of warmer climes. This April, there were no less than 12!

Blue Grosbeak sightings- April 2018
Blue Grosbeak sightings – April 2019

Sign up for Bird-A-Thon and Find Southern Wanderers!

Bird-a-thon is coming up on May 10t-11. Make sure to join a Bird-a-thon team if you haven’t yet! Then, find out which award you’re competing for, plan your strategy, and tell your friends who you’re raising money for!

If the current forecast for Bird-a-thon weekend holds, some overshoot species will no doubt be a key piece of the winning checklists. Southern overshoots get most attention from in-the-know birders in late April, mostly because it’s so striking to see them arrive even before our more common spring migrants show up. But conditions for overshoots can persist into early May, when southern birds show up at coastal thickets and migrant traps like Mass Audubon’s Marblehead Neck Wildlife Sanctuary and Mount Auburn Cemetery in Cambridge (psst– that’s a hint!)

If you’re joining us for Bird-a-thon, good luck, and may the best team win!

The Cardinal Chimaera: half male plumage, half female

Chimaera Northern Cardinal in Erie, PA (Photo by Shirley Caldwell)

Sometimes Nature offers up anomalies that seemingly defy credibility. Such was the case when a striking Northern Cardinal showed up recently at a backyard bird feeder in Erie, Pennsylvania. In appearance the cardinal appeared to have the typical red plumage of a male on its right side, and the light buffy-brown plumage of a female on the left side. So what’s the deal, you may ask?

This remarkable cardinal isn’t quite as unusual as you might suppose. It is actually a classic example of a chimaera—also known as a bilateral gynandromorph. So what does this mean in everyday-speak? A little review of Biology 101 reminds us that in humans, males have one copy of each sex chromosome (i.e. X and Y) while females have two copies of the X sex chromosome. In birds, this scheme is a little different in that in birds the sex chromosomes are referred to as Z and W, and it’s females that carry a single copy of the ZW chromosome, while males on the other hand have two of the ZZ chromosomes. Accordingly the cell nuclei of avian reproductive cells normally would possess only Z-carrying sperm cells in males, or Z or W-carrying egg cells in females.

Very rarely however, individuals occur where a female egg cell develops two nuclei — one with a Z sex chromosome and one with a W sex chromosome—and then gets fertilized twice by two Z-carrying male sperm cells. Clearly the odds of this happening are very low, but when it occurs, literally half of the double-fertilized product offspring will exhibit one set of gender characteristics while the other half will exhibit characteristics of the other gender. In the present instance, the right half of the Pennsylvania cardinal is exhibiting male features and the left side the features of a female. An ultramicroscopic examination of cells from the male half of this cardinal would reveal that it has a ZZ chromosome makeup, while cells from the female half would have a ZW makeup.

As if the circumstances described above are not improbable enough, the fact that the female (or left half) of the Pennsylvania cardinal has to be carrying both Z and W sex chromosomes, it’s actually possible that the bird could become fertilized since in birds, only the left ovary is functional! And the most exciting news of all is that the Erie cardinal is currently keeping company with a normal male Northern Cardinal, and local ornithologists are carefully tracking the chimera to see if it successfully breeds and lays eggs. So stay tuned for what could prove to be another chapter of this remarkable circumstance.

In conclusion it should be pointed out that such genetic reproductive anomalies may not actually be as infrequent as they might seem, since unless a species is strongly sexually dimorphic (i.e., males and females with highly different-looking plumages), bilateral gynandromorphism may not be as readily detectable as it is in cardinals. As an example, check out the “half-sider” images of a Rose-breasted Grosbeak that briefly attended a Newbury, MA feeder in 2015. For a full account of this individual, see Bird Observer (Vol. 43, No. 5, 2015).  Additionally, bilateral gynandromorphism is not uncommon in certain insects, fish, and even rarely in mammals. So if nothing else, not only have you possibly learned some new scrabble words, you may also now know to be particularly careful when you think you’re seeing double!

“Half-sider” Rose-breasted Grosbeak spotted in Newbury, MA in 2015 (Photo by Peter Brown)

Note: This post has been updated to remove an anachronism.