This column is the second of three summarizing the results of some of the recent Christmas Bird Counts in Maine. We’ll visit inland central Maine and two downeast coastal sites today.
I find it interesting to compare the counts from count circles that are geographically close. The Augusta and Waterville counts nearly overlap and were both held on December 14. Both counts had good diversity; Augusta counters found 53 species and Waterville counters found 61.
A Great Blue Heron was found on both counts. Raptor diversity was notable with each count yielding at least one Cooper’s Hawk, Sharp-shinned Hawk and Red-tailed Hawk. A highlight was a Peregrine Falcon in Waterville, flying south along the Kennebec River to the delight of the observers.
Both counts had the expected Common Goldeneyes and Waterville counters were able to pick out two Barrow’s Goldeneyes. A Ring-necked Duck was a nice find in Augusta as well as three Common Loons. An unfrozen outlet stream from China Lake yielded an American Coot for Waterville counters.
Both counts had multiple Red-bellied Woodpeckers, a species that was virtually unknown in New England 45 years ago. Their range expansion has been remarkable. Augusta also had a Yellow-bellied Sapsucker.
The two counts had similar counts for the more expected songbirds. Both counts had good number of White-throated Sparrows and Song Sparrows, two species that are often scarce in the winter. Counters in both circles tallied multiple Eastern Bluebirds, also unusual in winter in this part of the state.
Augusta had a Northern Shrike, a Carolina Wren and a Red-winged Blackbird. Waterville had a Snowy Owl, 30 Horned Larks, two Savannah Sparrows and five Evening Grosbeaks. An Eastern Screech-Owl was heard trilling twice in Waterville but unfortunately the bird could not be relocated and recorded or photographed.
Let’s head east to Bangor/Bucksport. The count on January 1 produced a nice count of 52 species. The proximity to the coast explains the five Bufflehead and eight Red-breasted Mergansers. All three species of accipiter hawks were tallied (Northern Goshawk is the toughest one to find). Two Snowy Owls added to the raptor list. A total of 27 songbirds were found with highlights being a Northern Shrike, two Carolina Wrens and a Hermit Thrush. Northern Cardinals continue to push northward in the state. The Bangor counters found 95 of these beauties, a new high for this count.
Continuing to the coast, we can compare two adjacent counts: the Mt. Desert Island count and the Schoodic Peninsula count. The MDI count was held on December 20 and yielded 64 species. Puddle duck diversity was great; a Gadwall, a Northern Pintail and two American Wigeons joined the expected Mallards (743) and American Black Ducks (519). Eight Ruddy Ducks were notable. No Red-throated Loons appeared this year but there were plenty of Common Loons. Both Double-crested Cormorant (7) and Great Cormorant (15) were found this year.
Twenty-three species of songbirds were counted. Good sightings included a Northern Shrike, eight Song Sparrows and 13 White-throated Sparrows. The best songbird records were for members of the blackbird family. MDI counters found three Red-winged Blackbirds, two Common Grackles and a Baltimore Oriole. I am sure these lingering birds are long gone now.
The counters on the Schoodic Peninsula count started the new year off well with a count of 51 species. It’s always a treat to see Harlequin Ducks and the Schoodic counters found six. Buffleheads, Common Eiders and Long-tailed Ducks were the most abundant waterfowl, represented by 1,116, 801 and 446 individuals, respectively. Three Red-throated Loons were nice to see. A lone Iceland Gull was discovered.
Songbird diversity was paltry with only 20 species found. Among those species, goodies included a Common Grackle, a Baltimore Oriole and a Yellow-rumped Warbler. Finches were hard to come by; 22 American Goldfinches and three House Finches were the only ones tallied.
[Originally published on February 1, 2015]
Categories: Christmas Count Summaries
This column is the first of three summarizing the results of some of the recent Christmas Bird Counts in Maine. We’ll cover some inland sites in today’s report.
The Lewiston-Auburn Count, held on December 20, yielded a count of 44 species. A singleton Green-winged Teal was found, always a good inland winter sighting. The 28 Lesser Scaup were noteworthy finds. The raptor diversity was decent with a dozen Bald Eagles, four Cooper’s Hawks, nine Red-tailed Hawks and one Rough-legged Hawk.
Nine Red-breasted Nuthatches were a nice total in a winter where this species is uncommon. Lingering species included five Eastern Bluebirds and a Hermit Thrush.
Finches were scarce with only four species found including 25 Purple Finches and four Pine Siskins.
A bit north, the Hartland Count held on December 27 produced a count of 35 species. A Northern Pintail was an excellent find. Three Bald Eagles and two Red-tailed Hawks were the only raptors tallied. Sixteen Red-breasted Nuthatches were notable.
A brave Great Blue Heron was found; some open water must have been present. Only two finch species were found (41 Pine Siskins and 75 American Goldfinches).
Counters on the Farmington Count, held on December 20, found only 30 species. The only aquatic birds of any stripe were three Common Loons. A lone Bald Eagle was the only bird of prey.
Seven Eastern Bluebirds were surprising discoveries as were the 79 American Robins. Both waxwings were present: 79 Cedar Waxwings and two Bohemian Waxwings.
We continue to build evidence that this winter is a poor one for irruptive finches. In Farmington, the only finches were 14 House Finches, 15 Pine Siskins and 93 American Goldfinches.
The Unity count was also held on December 20. This count was excellent with 49 species found, reflecting in part the army of 44 observers who participated. Unusual species included a Wood Duck, a Merlin, a Gray Catbird and a Savannah Sparrow.
Waldo Count has a strong Wild Turkey population, demonstrated by the 337 turkeys found on the count. Other game birds found were four Ruffed Grouse and a Ring-necked Pheasant.
Two owls were found: one Great Horned Owl and three Barred Owls. A Red-bellied Woodpecker was a pleasant surprise.
One Northern Shrike was a nice find for a winter where this irruptive species seems scarce so far this winter. Snow Buntings put on a good show with 103 tallied.
Six species of finches were found including a single Purple Finch, 14 Common Redpolls and two Evening Grosbeaks.
Reflecting the high degree of participation, record high counts were tallied for 18 of the 49 species.
We’ll move over to Sweden in Oxford County for a look at the results of their December 27 count. The participants found 44 species.
Five species of waterfowl were found along with five Common Loons. The loons represented excellent sightings for inland Maine in late December.
Four Bald Eagles and a Red-tailed Hawk were expected but not the lingering American Kestrel, a hardy bird indeed. A Snowy Owl and a Barred Owl rounded out the list of the birds of prey.
Red-breasted Nuthatches were well represented with 45 individuals found. Forty-five American Robins were notable.
Only two finch species were found: six Pine Siskins and 92 American Goldfinches. The highlight of the count was an eye-popping Rose-breasted Grosbeak. Most members of this species are in Central America or northern South America. A super sighting!
We’ll end with a stop in northern Somerset Count in the Misery Township. The tough winter weather here is inhospitable for many bird diversity is usually low. This year’s January 2 count was typical with 14 species found and 193 individuals. Three Gray Jays were delightful but expected in this part of the state. The only finches were five Common Redpolls.
[First published on January 18, 2015]
Categories: Christmas Count Summaries
We are finishing up the 115th National Audubon Christmas Bird Count. This year’s count period began on December 14 and continues until January 5. Each count occurs on a single day within a circle with a diameter of 15 miles (an area of 78 square miles). The data for all the counts are archived on-line by the National Audubon Society and are available for download by researchers and birders. I have published four papers that relied partly or wholly on Christmas Bird Count (CBC) data. This database is a remarkable resource for tracking changes in populations of wintering birds in North American and elsewhere.
The timing of CBCs is a bit early to sample winter populations. Depending on the severity of the late fall and early winter, some migratory birds may linger in the area. Great Blue Herons, Northern Harriers, Belted Kingfishers, Eastern Phoebes, Hermit Thrushes, Eastern Bluebirds, Gray Catbirds, various warblers and even Baltimore Orioles fall into this category. Virtually all of these lingering birds will be long gone by the first of February. On the other hand, the incursion of birds from the north can continue into January and February. The number of Bohemian Waxwings, Pine Grosbeaks, White-winged Crossbills, Evening Grosbeaks, Pine Siskins and Common Redpolls we see in late December may be dwarfed by numbers later in the winter. Wouldn’t it make more sense of have a continent-wide winter count in late January or early February? I think so. The initiation of the Great Backyard Bird Count over Presidents’ Day Weekend in February does provide deep-winter snapshots of winter bird abundance although the feeder-bird focus of this count fails to get a meaningful count of winter birds that don’t frequent feeders.
Why then was the decision made to conduct CBCs in late December? Historical constraints provide the answer. Around the turn of the 20th century, a popular activity in New England towns on Christmas Day was the “side hunt”. The men of the town would divide up into two sides and then comb the countryside and shore, shooting every bird (and mammal as well) they could. At the end of the day, each side would pile up all the animal carcasses they had collected. The team with the bigger pile was declared the winner. Most people today would regard such wanton killing as barbaric and unethical. Frank Chapman, an ornithologist at the American Museum of Natural History and a leader of the nascent National Audubon Society, thought so too and offered an alternative. Instead of shooting birds, people were encouraged to go out and count the birds they saw. The counts that people made were then published and served as a record of the bird abundance and distribution for particular areas. Thus was born the Christmas Bird Count.
The first censuses were held on Christmas Day, 1900. Twenty-five counts were held with modest participation. Most counts were in the northeastern United States but Toronto and Pacific Grove, California were covered as well. Collectively, these original counts produced a cumulative list of 90 species of birds. Now, nearly 2500 counts are conducted each year. Over 1800 are in the United States and more than 400 in Canada.. The remainder are held in Central and South America, Bermuda, various Caribbean islands and some Pacific Islands including Hawaii.
The CBC database is a testament to the power of citizen science, to the cooperative collection of data by many people with a singular purpose. The northward expansion of House Finches, Red-bellied Woodpeckers, Northern Mockingbirds and the decline of Harlequin Ducks in the east is evident in the CBC data. We’ve come quite a way since the time of the side hunts.
In the first three columns of every year, I discuss the highlights of many of the Maine CBC’s. You’ll see those columns soon.
[Originally published on January 4, 2015]
Categories: Bird Conservation · Christmas Count Summaries · History
It’s instructive to compare the feeding behavior of birds at our sunflower feeders. Some like House Finches, Purple Finches, Northern Cardinals and Evening Grosbeaks will sit on the feeder and crack seed after seed with their powerful, crushing bills. Others like Black-capped Chickadees, nuthatches and Tufted Titmice swoop in to grab a seed and then fly away with it.
Birds in the latter group have relatively small bills and can’t easily crush a sunflower seed to get to the nutritious kernel inside. Instead, one of these birds will take the seed to a more protected area, hold the seed firmly beneath its feet as it perches and chisels the sunflower seed apart with well-placed strikes at the suture line of the sunflower seed.
This process takes some time and focused vision so a chickadee’s guard is down. Chiseling a seed open in full view at a feeder is risky. Finches can crush a seed easily without having to use their eyes to accomplish the task. These birds can keep a watch for predators without having to retreat to a protected area to extract the kernels.
If you watch a chickadee after it flies away with a seed, you can often see the chickadee perch and hammer the seed open. Sometimes the chickadee will eat the kernel but at other times the chickadee will take the kernel and cache it behind a scale of conifer bark, in a crevice or among needle clusters of evergreens.
Many species of birds from diverse families hoard food. Usually the hoarded food is seeds although insects and other animal matter may be cached. One can consider voles or birds impaled on a barb by Northern Shrikes to be a type of hoarding behavior.
Hoarding makes good sense for resident birds. Food supplies always vacillate. Birds that are non-migratory have two choices: wander widely in search of patches of food or store food when it is abundant to use in times of food scarcity.
Hoarding has been well studied in Black-capped Chickadees. We’ll use this species as a case study in food hoarding.
Chickadees mostly cache food in the fall. October and November are the peak months and hoarding is only rare observed after December. During peak hoarding, a Black-capped Chickadee can store hundreds and even thousands of food items in a day. A study of a related species in Norway indicated 50,000-80,000 seeds were stored each autumn.
Chickadees store each seed in a separate location. This dispersed storage is called scatter hoarding as distinguished from larder formation where all the food is stored in a single place.
One might surmise that hoarding would be more important at higher latitudes where the winter is more severe. The available information supports this conjecture. Hoarding by Black-capped Chickadees is common in Ontario and New York but documented only once in southern Illinois.
Scatter hoarding is advantageous because a competitor cannot possibly find all the cached food items. However, hiding food singly demands a prodigious spatial memory. Chickadees are up to the task.
Work by David Sherry at the University of Toronto showed Black-capped Chickadees can accurately relocate caches 24 hours later. Subsequent work shows these spatial maps persist for as long as 28 days.
Chickadees spent more time in the vicinity of their caches than in areas where they had not hoarded seeds. Furthermore, chickadees allocate most of their time in the vicinity of caches where their most nutritious food has been hoarded.
Most food items are recovered between one and four days after hoarding. How can hoarding then be of value in the dead of winter? The answer seems to be that chickadees remove cached items and hide them again in a new place for a few days, moving them again and again until they are finally eaten.
[Originally published on December 21, 2014]
The irruption watch is on! Will Common Redpolls, Bohemian Waxwings, White-winged Crossbills, Snowy Owls and Pine Grosbeaks grace us with their presence this winter? Initial observations are promising as redpolls, Bohemian Waxwings and Snowy Owls have been reported widely in the state already.
These irruptive migrants are driven from their northerly breeding grounds by lack of food. Birds are remarkably tolerant of cold weather as long as they can find sufficient sustenance to keep their greedy furnaces stoked. When food on the Arctic tundra or the taiga becomes scarce, be it birch seeds, conifer seeds, lemmings or fruit, birds dependent on a particular food must move south or perish.
The Northern Shrike is another irruptive species. They are absent in Maine in some winters and occasionally common. At least a few Northern Shrikes have been seen in Maine. We’ll explore the biology of Northern Shrikes in today’s column.
The breeding distribution of Northern Shrikes spans the northern part of North American from Quebec to Alaska. When they withdraw from their breeding areas due to lack of food, they come farther south in the western United States, reaching southern Utah and Nevada. In the east, Northern Shrikes rarely occur south of Massachusetts and New York. This species also occurs in Eurasia where it is called the Great Grey Shrike.
Northern Shrikes are boldly marked birds, reminiscent of a bulky Northern Mockingbird. Northern Shrike adults have a gray back and crown with a narrow black mask through the eye. The wings are black with a prominent white patch. The tail is black with white outer tail feathers. The gray dorsal surface, white wing patches on black wings and white in the tail make it easy to dismiss a shrike as a mockingbird. The undersides are whitish-gray.
Immature Northern Shrikes look like washed out versions of adults. The upper parts are generally buff-colored; the mask is thinner and less darkly colored. The most distinctive feature is the prominent scaling on the breast and belly.
The similarity with mockingbirds ends when you check out the bill. The bill of a Northern Shrike is strongly hooked, used to kill small mammals, rodents and sometimes insects. A shrike is a hawk wannabe!
Northern Shrikes habitually perch at the top of a tall shrub or tree, appearing peaceful and docile. But when a potential prey is spotted, the shrike springs into action. A shrike usually captures insects or small mammals with its bill. Birds are pursued through the air and usually captured with the feet. Although the toes of shrike are not shaped like the talons of a hawk or owl, the feet are very strong. Friends of mine who band shrikes wear leather gloves when taking shrikes out of mistnets to avoid wounds from shrike feet clamping down on the banders’ hands.
Once a prey item has been secured, the shrike quickly kills it with a bite to the neck, severing the spinal cord at the level of the cervical vertebrate. The prey is typically impaled on thorns or barbed-wire, often left as a cache for later use. This macabre impaling behavior is the basis for the folk name of butcherbirds for shrikes.
While studying the effect of winter bird feeding on Black-capped Chickadees in a remote section of the North Woods east of Flagstaff Lake, I quickly learned when a Northern Shrike was in the neighborhood. The chickadees, woodpeckers and other birds frequenting the feeder would freeze. The cacophony of birds at the feeder halted; dead silence prevailed. Woodpeckers pressed themselves tightly against a tree trunk. The birds were perched stock-still in mortal feat. I never saw a shrike take a bird in this situation but they often captured a vole that made the unfortunate decision to emerge from the snow pack to grab a fallen sunflower seed.
[Originally published on December 7, 2014]
Categories: Migration · Species Accounts
Where did the summer go? The departure of most of our swallows and flycatchers indicates the fall migration has begun. Thr flood gates will soon be open as warblers, vireos and hummingbirds will leave us followed by sparrows and hawks. Today’s column is a potpourri of short items based on the theme of migration.
We delight in the spring arrival of migrating birds and claim them for our own. But when you think about it, the many species of birds that migrate from the tropics to nest in temperate North America spend only a minority of their time on our continent. A Ruby-throated Hummingbird nesting in Maine is here for only about three months. Migration to and from Costa Rica might require another two months or so. These hummingbirds are really Central American birds that grace us with their presence for a short time each year. The same can be said for Bobolinks in Argentina and Bolivia, Cliff Swallows throughout South America, Baltimore Orioles throughout Central America and numerous other migratory species.
Birding for songbirds during fall migration requires more effort than is needed during the spring migration. Fall migrants do not sing and have molted into their less conspicuous basic plumage. The phrase “confusing fall warblers” is so true.
Although most passerines do not migrate as a flock, migrants in a particular patch tend to gather in mixed-species flocks as they forage to fatten up for the next migratory leg. Fall birding in a forest is therefore hit-or-miss with often long periods of misses. A good trick is to find the chickadees. Migrant warblers and vireos often forage with the chickadees.
As an example, I was recently at West Quoddy State Park in Lubec with a couple of friends. We had walked over a mile with scarcely any birds. At the margin of the bog, I heard a couple of chickadees. I began pishing (saying the word pish quickly – if you don’t know the technique of pishing, do a YouTube search for pishing). As expected, the chickadees approached to investigate the source of the pishing but so did about 25 warblers. We were surrounded by Black-and-white Warblers, Black-throated Green Warblers, Yellow-rumped Warblers, a Common Yellowthroat and a Red-eyed Vireo for good measure.
We know that population numbers of many of these migratory songbirds are declining. One of the most important drivers in these declines is the cutting of tropical forests. A particular problem is cutting of timber on protected conservation land. These parks and preserves are difficult to police with limited staff and resources.
The monitoring of illegal timbering is done mainly with aerial or satellite images. Environmental managers may not get the photos for several days by which time the timber thieves have moved on.
Rainforest Connection, a start-up company in California, has developed a way to repurpose old smartphones to detect illegal timber activities quickly. A smartphone is covered in a water-proof case and powered with a solar battery. The phone is mounted high on a tree. A sensitive microphone is attached to the phone. The smartphone detects chain saw noises and gunshots. Each five minutes, the smartphone sends a packet of data to a central server. If the server detects the sound of chain saws, local enforcement officers, alerted by cell phone, can catch the ecocriminals in the act. Similarly, recordings of gunshots can aid in the capture of poachers.
Each phone can monitor an area of about one square mile. Cell phone coverage has penetrated deeply into equatorial forests throughout the world. The service plan costs for these phones are modest, only a few dollars a month in most tropical countries. Such a cost seems like a bargain in exchange for preventing the loss of thousands of dollars of wood or endangered animals. I suspect we will see the widespread use of this technology.
[Originally published on September 13, 2014]
Has anyone ever called you a bird brain? Maybe that term is not as nasty as intended. As we will see today, a bird’s brain is remarkably complex.
We know that birds and reptiles are each other’s closest relatives. Let’s compare a lizard brain and a bird brain.
The noses of land vertebrates are at the front of the body so it is no surprise that the olfactory lobes of vertebrates are the most anterior. The olfactory lobes of a reptile are larger than those of a bird. The sense of smell in a bird is pretty poor in most species. Exceptions occur like Turkey Vultures that locate carrion by smell and albatrosses and other tubenoses that smell the oils on the surface of the ocean released by groups of squid or small fish. Homing pigeons use smell for the final leg of a homing flight to find their roost. But smell is about the only function of the brain that is better developed in lizards.
The olfactory lobes make up a small portion of the forebrain; the cerebrum constitutes the majority of the cerebrum. The cerebral hemispheres are involved in complex behavioral instincts as well as learned intelligence. The cerebrum of a bird dwarfs the cerebrum of a lizard of similar size.
Parrots, corvids (crows and their relatives), woodpeckers and owls are regarded as the most intelligent birds. The particularly large size of their cerebrums is not surprising. Chickens and their relatives and pigeons have relatively small cerebrums.
Birds are very good at lab tests of intelligence, particularly the corvids. Birds can be taught to count to seven; researchers required 21,000 trials to teach monkeys to distinguish two from three.
In fairness to lizards, recent work at Duke University has shown that the Puerto Rican anole tested on a food-finding apparatus scored one for the reptile team. These anoles were able to solve problems as fast and sometimes faster than birds. But, the general rule is that birds are smarter than lizards.
The major part of the mid-brain of a bird or lizard is the cerebellum. The cerebellum plays a major role in muscular coordination. The demands of the complex body movements required for flight result in a well-developed cerebrum in birds. Aerial acrobats require complex control of movements to maintain equilibrium. The cerebellum of a land-restricted lizard is smaller.
The optic lobes of a bird or reptile are also part of the midbrain. Again, the optic lobes of a bird are much larger than the optic lobes of a lizard. We know that birds have the best vision of any vertebrates. The large optic lobes of a bird process the complex signals sent from the eye. Birds can certainly resolve colors much better than lizards (or humans), even seeing into the ultraviolet part of the spectrum that we humans cannot see at all. The resolution of images by birds is unrivalled. This stream of data requires a big computer for processing and the optic lobes function superbly in this regard.
The hindbrain of a vertebrate consists mostly of the medulla, the junction between the rest of the brain and the spinal cord. The hindbrain is also the site of the auditory lobes. We expect that the auditory lobes of a bird would be well developed because of the importance of vocal communication in birds. The auditory lobes are better developed in birds compared to lizards but are nowhere near the relative size of the cerebrum, cerebellum and optic lobes. Avian hearing and human hearing are pretty similar and we know that humans have a poor sense of hearing compared to most mammals.
If someone calls me a bird brain, I take that as a compliment: well-developed intelligence, the grace and control of a gymnast or ballet dancer, better vision than we humans can even contemplate and a pretty good sense of hearing. Thanks!
[First published on November 23, 2014]
In the last post, I embarked on an historical wild goose chase. I am tracing the development of our understanding of bird migration through the ages. The Barnacle Goose (this European vagrant was seen recently in Aroostook County) was the centerpiece of the last column. It’s name came from the medieval misconception that Barnacle Geese and barnacles are different stages of the same animal.
Humans did not really get a handle on bird migration until the 18th century, finally putting Greek myths about hibernation and transformations to rest. In 1749, Johannes Leche began recording the spring arrival dates of Finnish birds. As we will see, these types of records can be valuable in understanding migration.
The first published statement of bird migration appeared in Thomas Berwick’s A History of British Birds in 1798. Berwick disputed the prevalent notion that British swallows hibernated, writing “they leave us when this country can no longer furnish them with a supply of their proper and natural food …”.
From around 1900, local bird clubs have been collecting arrival and departure dates for migratory birds. By reading these local reports, an observer could determine that Ruby-throated Hummingbirds arrive in the Gulf Coast in early March, around April 10 in Virginia but not until early May in New England. The wave of migration of North American birds thus becomes evident through the shared observations.
We have come a long way since Lemche’s lonely records in Finland. Central depositories like ebird.org hold millions of records so the patterns of northward spread in the spring and southward withdrawal in autumn are clearly seen. If you haven’t tried the tools under the Explore Data link on ebird, give it a try.
Plotting the arrival and departures of migratory birds gives us insight into bird populations but not individuals. Do Ruby-throated Hummingbirds that cross the Gulf of Mexico and land in Louisiana continue their migration to the Midwest while those that land in Florida migrate up the Atlantic seaboard? We must track individuals to answer such questions.
Bird banding is just the tool we need to follow individuals. Audubon almost certainly banded the first birds in North America. In 1840, he tied a silver thread around the legs of several Eastern Phoebe nestlings on his farm near Philadelphia. Two of the phoebes came back the following year. Of course, he had no idea where the phoebes went to pass the winter but he clearly established the power of banding in following individual birds
The North American Bird Banding Program (NABBP), begun in 1920, facilitates the banding of birds in the United States and Canada. After extensive training, a person is provided with a Bander’s Permit and is given aluminum bands, each with a unique nine-digit number. Banders capture birds in nets or traps; identify the species, sex and age of each bird; take various body measurements; affix an aluminum band of the proper size to one of the legs of the bird; and release the bird.
If another bander captures the bird or if a banded bird is found dead, the finder contacts the biologists at the NABBP who provide the recovery data to the original bander and notifies the finder of the original date and site of the banding. Over the 94 years of the program, over 64 million birds have been banded and 3.5 million of them have been recovered. We have learned much about subpopulations of migratory species that maintain different migration routes, as well as information on fidelity to wintering and breeding sites over the years.
Even greater detail of migration routes can be gleaned from satellite transmitters mounted on birds’ backs or from small data loggers called geolocators that track a bird’s geographic position continuously. A geolocator has to be recovered to download the data, unlike a satellite transmitter. How cool is it to monitor an Osprey’s migration from your computer desktop?
[First published on November 9, 2014]
Categories: History · Migration
Some birders will argue that the fall migration beats the spring migration hands-down. Sure, spring songbirds are singing with full throat, dressed in their breeding season finery. But the spring migration is relatively brief.
The fall migration is much more protracted, spanning early August into December for different species. Post-breeding dispersal of many species leads to surprising records of vagrant birds. Storms may also displace migrants.
In recent years, Old World Geese visit New England in small numbers. A few Pink-footed Geese have graced us with their presence in cow pastures in Yarmouth. A Barnacle Goose or two visit northeastern North America each fall. The nearest breeding area for both of these species is Greenland.
We occasionally see a Greater White-fronted Goose. This widely spread species occurs mostly west of the Mississippi River in North America but also in the Old World, as far west as Greenland.
On October 13, Bill Sheehan hit the goose jackpot in central Aroostook County. He found six species of geese. Three species were not surprising: Canada Goose, Cackling Goose (a smaller version of Canada Goose, now recognized as a separate species) and Snow Goose. But he hit the trifecta of rare geese finding a Barnacle Goose, a Greater White-fronted Goose and a Pink-footed Goose. A great day!
But Barnacle Goose? It’s a peculiar name because these geese are vegetarians like other geese and rarely if ever eat intertidal animals. The explanation for the name provides a good opportunity to think about the methodology of science as we seek to better understand the natural world.
The path leading to our current understanding of bird migration is a circuitous one, with plenty of dead ends. Like most scientific inquiry, observers build on the observations of those that came before them. The notion of standing on the shoulders of earlier observers stems from at least the 12th century to a man known only as Bernard of Chartres. The metaphor is best known from Sir Isaac Newton’s quip, “If I have seen further it is by standing on the shoulders of giants.”
Humans have certainly been aware for millennia that bird abundance changes through the year. When you depend on birds as part of your diet, failure to pay attention to changes in bird numbers can influence survival. But where did the birds go?
The notion of migration is implicit in a verse of the Old Testament: “The stork in the heaven knoweth her appointed times; and the turtledove and the crane and the swallow observe the time of their coming.” In the eighth century BC, Homer wrote that cranes flee from the coming of winter.
A couple of centuries later, Aristotle wrote, “Some creatures can make provision against change without stirring from their ordinary haunts; others migrate as in the case of the crane.” He also wrote of the migration of pelicans. So far, so good. Observers surmised that some birds come and go in response to the changing of the seasons.
Unfortunately, Aristotle also wrote “certain birds (as the kite and swallow) decline the trouble of migration and hide themselves where they are.” He went to write that some birds hid themselves in hles in the ground, sometimes without their feathers. Some Greeks also believed in transformation. In Greece, the European Redstart is a common breeder, migrating to Africa each fall. The European Robin is a winter visitor to Greece. Aristotle claimed European Redstarts transformed into European Robins.
In the Middle Ages, Europeans used Aristotle’s mistaken observations to explain the arrival of Barnacle Geese each fall from their high Arctic breeding grounds as a transformation from the stalked, goose-neck barnacles found commonly on floating driftwood. We’ve come a long way since then but the history of this misstep is perpetuated in the Barnacle Goose’s name. We’ll continue our exploration of migration next time.
[Originally published on October 25, 2014]
Categories: History · Migration
October is a time when we can expect to see large flocks of Dark-eyed Juncos. The ivory-colored bill is a good field mark. Adult males have gray above, extending down onto the throat and upper breast. The gray contrasts with the white lower parts of the underside. Females are brown above with some muted gray feathering as well. In both sexes, the outer tail feathers are white, flashing a warning when a bird suddenly takes flight.
Although these sparrows can be found year-round in Maine, their numbers are bolstered in our state by passage migrants (migrants simply moving through Maine) in April en route to more northerly breeding grounds and in October en route to more southerly wintering areas.
Dark-eyed Juncos breed from northern York County northward throughout the rest of the state. Breeding densities are greatest in the spruce-fir forests of the northern half of Maine. Some juncos overwinter but their numbers vary from year to year.
The entire geographic range of Dark-eyed Juncos is huge, extending as far north as the tree line in Alaska and Canada and southward throughout most of the lower Forty-eight, excepting peninsular Florida. Some even winter in northern Mexico. A recent estimate placed the Dark-eyed Junco population at around 630 million birds.
This broad range means that most North Americans see juncos during some portion of the year. The confiding nature of these birds and their willing use of human-altered landscapes increase the likelihood of our encountering these birds. John James Audubon in 1831wrote that “there is not an individual in the Union who does not know the little Snow-bird”. Growing up in North Carolina, I heard these birds referred to as snowbirds as well. Their arrival in the South coincided with the onset of winter.
Junco is the genus of these birds as well as the common name. The name seems ill chosen because Junco is derived from Juncus, an emergent reed growing on the margins of lakes and ponds. Hardly the habitat of a junco.
Juncos feed primarily on the ground and from the leaf litter. Seeds as well as insects and other arthropods like spiders make up the bulk of the diet of Dark-eyed Juncos. They will occasionally take fruit. Diet studies show the juncos prefer small seeds. Important seeds taken include those from chickweed, pigweed, knotweed, sorrel and timothy grass.
Although juncos spend a lot of time on the ground, I often find male juncos singing their hearts out at the top of a tall spruce or fir. Their trilled song is easily confused with other trillers, particularly the Chipping Sparrow. The junco song is more musical and bell-like to my ear.
Males are strongly territorial during the breeding season, defending a territory of about three or four acres. In winter flocks, a strict hierarchy or pecking order is set up. Every junco knows her or his place in the power structure of the flock.
Dark-eyed Juncos have been the course of much debate among bird taxonomists. Until 1973, the currently recognized Dark-eyed Junco was split into five species, each with some distinctive feature on top of the generalized junco morphology. In the east, we had the Slate-colored Junco and the other species were White-winged Junco, Oregon Junco, Gray-headed Junco and Guadalupe Junco. Based on the joint possession of dark eyes and other anatomical considerations, the Check-list Committee of the American Ornithologist Union merged these five species into a single species. This decision is disputed by some bird systematists. Recent fieldwork shows that different junco forms at abutting geographic boundaries do not freely interbreed. This evidence may be sufficient to restore species status for some of these forms.
I remember the frustration of many competitive North American birders at the decision to lump the five species of juncos into one. These listers saw their life lists decrease by four species!
[Originally published on October 12, 2014]
Categories: Species Accounts