January 19, 2014

Review of Maine Christmas Bird Counts – I

January 19, 2014 By Herb Wilson in Christmas Count Summaries

The National Audubon Christmas Bird Count season has begun. This column is the first of three in which I will describe some of the notable sightings of some of the Christmas Bird Counts (hereafter, CBC’s) conducted in Maine.

In a recent column, I wrote about the phenomenon of irruptions of northerly birds into Maine. From the first CBC data, this winter does not appear to be an irruption year. Perhaps I may change my tune by the end of the CBC season on January 5.

Saturday, December 14 was a bitterly cold but clear day. Intrepid birders braved the weather, encountering a nice diversity of birds. We’ll look at the highlights of three counts conducted on that day.

The Lewiston-Auburn CBC yielded a count of 47 species. The cold weather over the past week caused most open water to freeze with only the Androscoggin River and the middle of Lake Auburn available to waterbirds. Despite the reduced open water habitat, three Common Loons were found. Five species of ducks were found with the 479 Mallards far outnumbering the Common Mergansers, Hooded Mergansers and Common Goldeneyes.

Seven species of birds of prey were pretty impressive, headlined by a Snowy Owl and three Peregrine Falcons.

Lingering birds included two Carolina Wrens, six Eastern Bluebirds, an Eastern Towhee and two Field Sparrows.

The only waxwings were 4 Cedar Waxwings. The only finches were 33 House Finches and 81 American Goldfinches.

A quick glance at the totals of any CBC reminds one of the impact that humans have on bird diversity and abundance. The two most common birds on this count were introduced birds: 875 European Starlings and 825 Rock Pigeons. The 765 American Crows were the most common native birds.

The Augusta CBC produced a total of 46 species. Waterfowl were hard to come by with 40 Mallards and American Black Ducks the most common. A single Common Goldeneye, three Common Mergansers and 27 Hooded Mergansers rounded out the list.

Four species of finches were found with a lone Pine Siskin and nine Purple Finches joining the more common American Goldfinch and House Finches.

Lingering birds, soon to depart I am sure with the arrival of snow and extended cold, included Belted Kingfisher, a Northern Flicker, five Eastern Bluebirds (spectacular against the snow), two Hermit Thrushes, and two Northern Mockingbirds.

The Greater Portland CBC usually takes pride of place with the most species of any CBC in Maine. This year, 46 counters found 92 species. The seabird counts were a bit low, in large part because of the sea smoke that limited visibility over the ocean water.

Twenty-two species of waterfowl were found. Highlights included a pair of American Wigeon, three Northern Pintail, two Ring-necked Ducks, six Barrow’s Goldeneye, and a singleton Ruddy Duck.

Grebe and loon numbers were on the low side: six Red-throated Loons, 118 Common Loons, 31 Horned Grebe, and 30 Red-necked Grebe.

Lingering birds included three Double-crested Cormorants, six Turkey Vultures, three Northern Harriers, an American Coot, a Killdeer, six Belted Kingfishers, three Yellow-bellied Sapsuckers, 11 Northern Flickers, eight Carolina Wrens (all-time high for this count), a Ruby-crowned Kinglet, 40(!) Eastern Bluebirds, five Hermit Thrushes, two Gray Catbirds, five Yellow-rumped Warblers, four Savannah Sparrows, a Lincoln’s Sparrow, and a White-crowned Sparrow. Whew! That is a remarkable list of birds, most of which are surely struggling to survive in Maine while other members of their species are in much more equitable climates.

The eight Snowy Owls were a high total for this count. Three Peregrine Falcons were nice to see.

Six species of gulls were found with only one Bonaparte’s Gull found. Both species of white-winged gulls were found: two Iceland Gulls and seven Glaucous Gulls.

No irruptive finches were found; American Goldfinches and House Finches were the only finches tallied.

[First published on December 29, 2013]

Black-capped Chickadees and Feeder Visits

January 19, 2014 By Herb Wilson in Banding, Behavior, Species Accounts

Today, let’s think about chickadees. These endearing birds are regulars at any feeding station. Sometimes, ten or more may be seen at a feeder at once. However, the total number of individuals visiting your feeder is far more than that. I’ll describe some of my own research to demonstrate that point.

During the winter, Black-capped Chickadees form season-long flocks. The flock is made up of a local pair of adults joined by usually between eight and twelve juvenile birds (none of whom are the kids of the adult pair). Often this cohesive flock is joined by one or two White-breasted Nuthatches, Red-breasted Nuthatches, Tufted Titmice, Golden-crowned Kinglets or Downy Woodpeckers.

The flock defends a large territory (10-25 acres) against incursions by neighboring flocks. A flock makes sure it has exclusive access to the food in its winter territory.

But what happens when we put out well-stocked bird feeders through the winter? Ecologists know that territorial behavior is only seen when the benefit of having sole access to resources is greater than the cost of defending those resources. If food is essentially unlimited, what is the benefit of defending a territory? Shouldn’t there be enough food for all?

To explore these questions, I set up a number of feeding stations in the spruce-fir forest on the eastern bank of Flagstaff Lake. Few people live along the upper part of Long Falls Dam Road in the winter so I knew that the chickadees there would not have access to other feeding stations.

At each feeding station, I captured chickadees with a mist-net. Each bird was fitted with a numbered, aluminum band and two plastic color bands. I used a number of different colors of bands and each bird was given a unique combination of bands. Therefore, I could recognize individuals at the feeders without having to recapture them to read the band number.

Over the course of the winter, I conducted four 30-minute observations each week at each of the four feeding stations. For each half-hour, I recorded each visit to the feeders by chickadees, identifying the color-band combination of banded birds and identifying other birds as unbanded.

These censuses got manic at times. Once I had 374 visits in a half-hour! I could only keep up by recording the data into a hand-held recorder with my other hand holding by binoculars to determine the color-combinations of visitors.

At the end of each weekly census, I refilled the feeders. The feeders had sunflower seeds continuously from late October until the end of March.

At the end of the study, I used a technique called mark-recapture analysis to determine the total number of chickadees visiting each feeder. I knew how many banded birds I had at each station (15-20) but I had to use the mark-recapture technique to estimate how many unbanded chickadees were taking advantage of my sunflower handouts.

Mark-recapture is a straightforward technique. One marks some individuals of a population (the color-banded chickadees in my case). Future sampling should yield a mix of marked and unmarked individuals. If most of the individuals subsequently sampled are marked, one can infer that the unmarked individuals are relatively few in number.

In my case, feeder visits by unmarked birds greatly exceeded visits by banded birds. The mark-recapture software I used indicated that between 80 and 120 chickadees were visiting my feeders each week! However, the birds still maintained their flock integrity so I rarely would have more than a dozen birds present at any time. Territories broke down when food became unlimited.

[First published on December on December 22, 2013]

Irruptions

January 19, 2014 By Herb Wilson in Migration

What will the winter bring? Birders frequently ask this question each fall. We know we can count on seeing our resident birds this winter like Black-capped Chickadees, American Crows and Hairy Woodpeckers. We also know that most species of migratory breeding birds are gone now but will be back next summer. You can count on seeing Eastern Phoebes, House Wrens and Yellow Warblers come the summer. Passage migrants (birds which breed to our north and winter to our south) seldom linger in Maine for the winter. Snow Geese and Semipalmated Sandpipers are two examples of Maine passage migrants.

The last category of birds, winter migrants, inspires excitement in birders. These birds breed to our north, some as far north as the arctic tundra. Some of our winter migrants like American Tree Sparrows are expected every year. But many winter migrants are unpredictable; in some years, they may be common and in other years scarcer than hen’s teeth. These birds include Snowy Owls, Bohemian Waxwings and a suite of finches commonly called the northern finches.

Why the variability? The answer is quite simply food availability. Snowy Owls are perfectly capable of making it through a winter on the arctic tundra if the lemming population is sufficient to provide food. Similarly, Common Redpolls can survive an arctic winter given sufficient birch seeds.

However, lemming abundance, birch and conifer seed production, and soft fruit production vary from year to year. When the requisite food is scarce, birds must migrate south to find food. The result is an influx of northern birds. Who is not thrilled by flocks of Common Redpolls at our feeders or Bohemian Waxwings in our fruit trees?

Ecologists refer to these incursions of birds as irruptions. An irruption is movement into a particular place, just the opposite of movement out in an eruption. We can think of Common Redpolls erupting from northerly areas when food is not available and irrupting into Maine where birch seeds may be more plentiful.

This winter is shaping up to be an irruption year for Snowy Owls. Over 20 of these magnificent raptors have been sighted in Maine already this winter, mostly along the coast. On December 1, two birders in Newfoundland saw 138 on an all-day birding trip. Keep those eyes peeled!

A couple of flocks of Bohemian Waxwing were seen in the past week. Look for these fruit-eaters at apple orchards or in stands of fruit-bearing trees or shrubs.

The irruptive finches show weak correlations in their abundances because they rely on different types of tree seeds for their sustenance. Ron Pittaway prepares predictions of irruptions each fall based on the production of various species of trees in the vast stretches of boreal forest to our north.

Pittaway reports that mountain ash produced an abundant berry crop to the north of us this fall. Therefore, we are not likely to see very many Pine Grosbeaks (fruit-eating finches) this year.

Birch and alder seeds are abundant in boreal forests to our north. We should not expect a major irruption of Common Redpolls.

Red Crossbills prefer to extract seeds from the cones of Red Pine and White Pine. Red Pine cone production is fair to good this year and White Pine production is poor. Look for occasional Red Crossbills in Maine where ornamental conifers or pines are laden with cones.

White-winged Crossbills prefer spruce cones. Good to excellent spruce production is seen in the boreal forest, extending down into northern New England and the Adirondacks. These crossbills are likely to be broadly dispersed so we should not expect high populations this winter.

Pine Siskins with their small bills rely heavily on hemlock and spruce cones. Fair numbers of siskins are expected in northern New England this winter.

[First published on December 10, 2013]

White versus Dark Muscles in Birds

January 19, 2014 By Herb Wilson in Physiology

White meat or dark? This question will be asked thousands of times as families and friends gather around the Thanksgiving turkey.

But why are there two kinds of muscles? We’ll need to explore some muscle physiology to answer the question. Muscles are made of many elongate cells called muscle fibers. Each fiber is capable of contracting, causing the muscle to shorten. The muscles are attached to bones via a piece of connective tissue called tendons. When all the fibers of a muscle contract, the muscle is capable of remarkable force, causing movement in the part of the body to which the muscle inserts.

All muscles contain a mixture of two types of fibers: white and dark (or red). They differ in their metabolism and their contractile properties. Dark fibers are sometimes referred to as slow-twitch muscles or aerobic muscles. As the name implies, aerobic fibers require a constant supply of oxygen to continue to function. This oxygen supply is enabled by the myoglobin molecules in the muscle fibers.

Like the related hemoglobin in the blood, myoglobin is a molecule that readily binds to oxygen. Oxygenated blood courses through muscles and oxygen is transferred from the hemoglobin in the red blood cells to the myoglobin molecules in the muscle fibers. The more myoglobin within the muscle fibers of a muscle, the darker the muscle appears.

Dark fibers are great for activities involving endurance. Walking and running are generally powered by the contraction of aerobic fibers.

White fibers, also called fast-twitch fibers or anaerobic fibers, are used for rapid, short-term activities like fleeing from danger. These fast-twitch muscles are able to contract more quickly than the dark, slow-twitch muscles. However, they fatigue very quickly. These fibers operate in an anaerobic mode, a mode not requiring the continuous input of oxygen. To fuel their contraction, white fibers take up the starch glygogen, stored in the muscle fibers. The glycogen stores are quickly depleted so the rapid contraction of the white fibers is necessarily limited in duration.

In life, muscles made mostly of white fibers appear translucent and glossy. When cooked, the proteins in the muscle fibers denature and coagulate, resulting in the white, opaque appearance we associate with a chicken or turkey breast.

The myoglobin in the dark muscles also breaks down during cooking, imparting the brownish color to the meat. The breakdown of myoglobin also makes a steak brown when it is cooked.

Birds that migrate long distances have breast muscles made mostly of dark muscle fibers to enable long bouts of strenuous flight. Ducks and geese have breast muscles made of aerobic fibers and are dark when cooked. Wild Turkeys do not fly for great distances. These birds have breast muscles that contain fewer dark fibers than a duck but more dark fibers than a domesticated turkey.

Domesticated turkeys have far larger breast muscles than Wild Turkeys. Selective breeding by turkey farmers has led to the increase in these muscles. The breast muscles of a male turkey are so massive that the tom turkeys are incapable of getting close enough to a hen turkey to mate. Domesticated turkeys are produced by artificial insemination.

In a cooked turkey or chicken, you can see two distinct muscles in the breast: the smaller supracoracoideus (closer to the base of the breastbone) and the much larger pectoralis muscle. Both attach to the upper wing bone, the humerus. The pectoralis pulls the wing down, providing the power for flight. The supracoracoideus muscle pulls the wing back up in preparation for the next power stroke.

How does a muscle below the wing raise the wing? The supracoracoideus runs through a canal between the humerus, the scapula and the coracoid bone to attach on the upper side of the humerus. With a downward tug, the wing is raised.

[First published on November 26, 2013]

Herring Gulls

January 19, 2014 By Herb Wilson in Identification, Species Accounts

The Herring Gull is the most common and the most familiar gull in Maine. They are typically associated with the shorelines of the ocean, lakes and large rivers. These birds have readily adapted to human-altered landscapes so small flocks may hang out in parking lots, cadging French fries or other morsels from fast-food restaurant customers. Hundreds and even thousands of these gulls may be seen at open landfills.

In North America, Herring Gulls breed across most of Canada and in the northern tier of states from Minnesota to Maine. Many of those breeding Herring Gulls will migrate south for the winter, either along the Pacific Coast from southeastern Alaska to Baja Mexico or to southern states from Texas east to North Carolina. Some even migrate to Caribbean islands. Some Herring Gulls breeding along the coast from Massachusetts to North Carolina are year-round residents.

Although we think of Herring Gulls as abundant members of our avifauna, this species was nearly extirpated from North America in the 19^th century by plumage hunters and egg collectors. Thanks to protection afforded by laws, Herring Gull populations have rebounded. Populations in New England have been reasonably stable since 1970. Some ornithologists believe that Herring Gulls may be more abundant now than they were historically before the egg and plumage collectors began to take a major toll on the populations.

Adult Herring Gulls are fairly easy to identify. Look for the pink legs to start with. The head, neck and undersides are white, often speckled with black in the winter (as seen in the photograph). The upper wings and the upper back (the mantle) are light gray. The wing tips are black with white spots (called mirrors). The eye is yellow. The massive bill is yellow to light orange with a red spot near the tip on either side.

Herring Gulls require four years to attain sexual maturity and therefore their adult plumage. The immature plumages of Herring Gulls are a bit trickier to master and separate from other large gulls but a little effort can be quite rewarding. The timing of the molts varies greatly among individuals of the same age and an incomplete molt leading from winter (basic) to summer (alternate) plumage adds to the challenge of ageing a Herring Gull.

Take a look at your favorite field guide and you will see that the plumage of Herring Gulls gets lighter as they age. First-year gulls are mostly brown; their bills are dark. Second-year gulls are usually a bit lighter than first-years, particularly showing some white on the head and some gray feathers on the mantle. Their bills are black at the tip but are yellow at the base. Third-year birds still show some brown streaking on the head. Such a bird appears to be wearing a gray backpack, contrasting with the browner feathers on the outer part of the wing. The bill shows a bit of black at the tip.

The third-year plumage is the least frequently encountered plumage. Can you figure out why? To answer the question, let’s follow four cohorts of gulls over four consecutive years. Let’s say that 100 Herring Gulls are hatched each year and that 10% of them will die within a year. After those four years, we will then have 100 first-year gulls, 90- second-year gulls, 80 third-year gulls and 70 fourth-year gulls. But those fourth-year gulls are now in the adult or definitive plumage and will join the multiple-year class of adult birds. Herring Gulls typically live to be 15-20 years old, with some exceeding 30 years old. With this piling up of birds of many ages wearing the same clothes, It’s not surprising that the adult plumage is the most commonly encountered, followed by first-year birds, then second-year birds, and finally the third-year birds.

[First published on November 12, 2013]

Learning in Birds

January 19, 2014 By Herb Wilson in Behavior

I’ve been busy grading mid-term exams so learning is on my mind. A lot of learning goes on in the bird world too.

The ability to sing has a strong component of learning in most birds. Although a bird raised in isolation will attempt to sing, its song will be a poor rendition of the song that its father sang to attract its mother.

A number of birds are able mimics. A parrot can be taught to say “Polly, want a cracker” and any number of other phrases. A Northern Mockingbird can mimic as many as 30 other species of coexisting birds. The Marsh Warbler in Britain mimics 99 European species and 133 African species that it coexists with on its wintering grounds. A Lyrebird in Australia over 19 years learned to imitate barnyard sounds including pig squeals, a chain rattling, a cross-cut saw, and a howling dog, along with most calls and songs of the local birds! A Crested Lark in Germany learned the whistled commands given to sheepdogs (“Run ahead”, “Fast”, “Halt” and “Come here”). When taped and played back to sheep dogs, these calls were obeyed by the dogs.

Birds learn to solve complex problems more readily than many mammals in laboratory experiments. One experiment involved a four-feet long board with a narrow slit in the middle. A test animal was placed on one side of the board. Two bowls were placed on the other side of the slit, visible to the test animal. One bowl had food and the other was empty. The test animal watched as one bowl was moved to the far left and one to the far right, both out of sight of the test animal. The animal was then allowed to walk around to try to find the food. Dogs and crows quickly learn to go around the side nearest the food. Cats, rabbits and chickens never learn to solve the problem.

Learning to count is difficult for most mammals. It took 21,000 trials to get a monkey to learn to tell the difference between a two-note sound and a three-note sound. Rats never learned to distinguish the two sounds. Birds easily learn to tell the difference. Parakeets and ravens can be taught to count to seven.

Birds engage in insight learning, a complex mode of learning. A bird is able to learn by observation and imitation of others. Blue Jays can learn to tell edible from inedible caterpillars by watching the reaction of other Blue Jays when they attempt to eat a caterpillar.

Another nice example is described for Great Tits (a relative of our chickadees) in England. In the 1950’s, Great Tits learned to tear the cardboard caps of milk bottles so they could drink the cream. This innovative behavior was quickly passed on to other members of the species. Milk companies had to replace the cardboard caps with stronger metal caps to keep the Great Tits out.

Young birds must learn how to capture food. Young terns, pelicans and herons miss the fish they are pursuing far more frequently than adults. In North Carolina, I have observed a number of young Northern Gannets (but no adults) dead on the beach. One possible explanation is that these young birds were diving into shallow water and breaking their necks. A tough lesson to learn!

Some birds have devised ways to use tools to feed. The Woodpecker Finch of the Galapagos Islands uses a stick or cactus spine held in its bill to pry insects from crevices. Egyptian Vultures have learned to crack ostrich eggs using stones. Green Herons are clever fishers, using pieces of bread as fishing bait. A Green Heron will drop bread into still water and wait for fish to gather which it then captures by spearing with its bill. If currents carry off the bait, the heron will retrieve the bait and use it again.

[First published on October 29, 2013]

White-crowned Sparrows

January 19, 2014 By Herb Wilson in Migration, Species Accounts

The fall migration of birds continues in high gear. Most of the leaf-gleaning insectivores like warblers, vireos, and tanagers have departed for warmer climes although a few Yellow-rumped Warblers and Palm Warblers will linger for a few more weeks.

Seed-eating migratory birds can be more leisurely about their migration. Until snow accumulates, these seed-eaters (or granivores) can find sufficient food. Sparrows are common granivores and are the main songbird migrants passing through Maine in October. Many of these birds are passage migrants, breeding to our north and passing through Maine on their southward seasonal journey.

Dark-eyed Juncos have increased in numbers in the past couple of weeks. Chipping Sparrow numbers have passed their peak. Diligent searching of sparrow flocks will often reward a birder with a view of a Lincoln’s Sparrow among the more common Song Sparrows and White-throated Sparrows. Swamp Sparrows are pretty common now too although you may have to flush them out of fields or marshes to see them well.

A treat this time of year is to see White-crowned Sparrows. These large sparrows belong to the genus Zonotrichia, the same genus to which White-throated Sparrows belong. Both of these Zonotrichia species have prominent black streaks on the head alternating with white or tan stripes. Both species have gray breasts without streaking (except for the streaked juveniles of both species). As the names suggest, the White-throated Sparrow has a brilliant white throat, bordered with a thin dark stripe on the lower side. The White-crowned Sparrow has a throat that is lighter in color than the gray breast but never light enough to be called white. There is no black border to the throat in the White-crowned either. One other feature that can be used to distinguish these two species is the color of the lores, the small feathers between the base of the bill and the eye. In the White-throated Sparrow, the lores are yellow. The lores are dark in the White-crowned Sparrow.

In both species, the light head stripes may be either white or tan. Birds of either species in their first-winter plumage (the plumage that replaces the juvenile plumage in the fall of the first year) show tan stripes. Adult White-crowned Sparrows always have white stripes on their crowns. White-throated Sparrows may have either tan or white stripes on the crown as adults. So, it’s a snap to age a White-crowned Sparrow by the color of the head stripes.

All White-crowned Sparrows migrating through Maine are passage migrants. In other words, they winter to our south and breed to our north and do not breed in our state. The only time we see them is when they move through on their spring and fall migrations.

In eastern North America, the closest breeding populations are in northwestern Newfoundland and the northern portions of New Brunswick and Newfoundland. The breeding distribution is wider in western North America, extending south from Canada into the United States in the Rocky Mountains and along the immediate Pacific coast all the way to southern California.

Some ornithologists claim that the White-crowned Sparrow is the best-studied songbird in North America. The species is suitable for as a research subject because of its abundance, its wide geographic distribution and its fearless behavior as ornithologists make observations.

The song type of White-crowned Sparrows varies markedly across its breeding range. Studies on its vocalization have contributed much to our understanding of song learning in songbirds.

Other studies on White-crowned Sparrows have demonstrated the remarkable navigation abilities of birds. Birds wintering in the San Jose region of California were captured and carried via airplane to Maryland and Louisiana. The birds were then released. The displaced birds found their back to their Alaska breeding grounds in the summer and reappeared at their San Jose wintering areas the following winter!

[First published on October 13, 2013]

American Pipits

January 19, 2014 By Herb Wilson in Species Accounts

The fall is the best time to see one of Maine’s rarest breeding birds, the American Pipit. The only place in Maine where these ground-dwelling birds nest is on the Tablelands leading up to Baxter Peak on Mt. Katahdin. Seeing these unusual breeders on a hike up Mt. Katahdin is a welcome bonus to a hiker with a birding interest.

However, American Pipits do have a broad breeding distribution across North America, mostly in areas that are inhospitable for these insect-feeders in the winter. They nest across the North American tundra, in most parts of Alaska and along the crests of the Rocky Mountains and Cascade Mountains, nesting as far south as Arizona. They nest broadly in Newfoundland as well. Migrating American Pipits pass through Maine in significant numbers.

American Pipits belong to the bird family called the Motacillidae, a family that also includes the wagtails (much more common in the Eastern Hemisphere). All motacillids spend most of their time on the ground, foraging for insects, spiders and even freshwater snails and crustaceans.

The Motacillidae includes about 65 species of birds. Forty of these species are classified as pipits. Pipits are more cosmopolitan than their wagtail relatives. Most pipits are found in the Old World but also occur in North America, New Zealand and other oceanic islands.

Pipits are generally inconspicuous birds whose brown, buff and gray plumage provides great camouflage against stony ground. The bill is pointed as one expects for an insect-eater but not as fine as the bill of a New World warbler. The breast of of most species is streaked, affording yet more camouflage.

The American Pipit can be distinguished from other ground-dwelling songbirds by its habit of bobbing its tail as it walks. The outer tail feathers are white and are conspicuous in flight. The call of a pipit, often given in flight, is (you guessed it) a two-noted sound described as “pip-it”. Here is a link with sound files: http://tinyurl.com/m4ssm6a

Prior to 1989, North American field guides gave the name of our pipit as Water Pipit. Water Pipits showed a broad distribution throughout North America and Eurasia. However, the American Ornithologists Union Check-list Committee split the North American forms from the Eurasian forms, elevating our birds to a separate species, the American Pipit, restricted to the New World.

So how do you see an American Pipit short of hiking Katahdin or visiting the Arctic tundra in the summer? Migrating American Pipits often occur along beaches so areas like Reid State Park can be productive. They also occur in agricultural fields, particularly in those where farmers spread manure. As their former name suggests, American Pipits often forage in wet fields and near freshwater water bodies. American Pipits will wade into shallow water after aquatic invertebrates.

American Pipits are social creatures during migration so seeing a solitary individual is unusual. Scanning fields for pipits will often yield Horned Larks and Lapland Longspurs, two other passage migrants that are mainly ground-dwelling birds.

If you get a close look at an American Pipit, take a look at the claws on its toes. Those claws are exceptionally long, particularly the one on the hind toe. This characteristic of long toenails occurs convergently in other groups of birds that spend a lot of time walking on the ground. Horned Larks show similar long toenails.

The long claws may aid American Pipits in walking on snow. However, deep snow cover will usually push these birds south as the weather in northern areas deteriorates. American Pipits winter along the southern tier of states from California to Florida. Along the east coast, some pipits will winter as far north as coastal Virginia. The Mediterranean climate of the west coast of North America permits American Pipits to overwinter as far north as western Washington and even southwestern British Columbia.

[First published on September 29, 2013]

Red-necked Phalaropes in the Bay of Fundy

January 19, 2014 By Herb Wilson in Migration, Species Accounts

One of the best-known quotations from the Greek philosopher Heraclitus is translated as “Everything flows, nothing stands still”. We always expect change. Of course, the certainty of change applies to birds.

Bird populations inevitably vary. Sometimes birds increase locally because particularly favorable conditions occur. For instance, a gypsy moth outbreak provides lots of food for insect-eating birds and the nesting success of such birds is higher than normal. Other events like the 1998 ice storm can wreak havoc on local bird populations.

Bird populations can also change on much larger geographic scales. A widespread outbreak of avian conjunctivitis in the early 1990’s resulted in the death of many House Finches in the eastern United States. The clearing of bottomland forest in the Deep South certainly was a major contributor to the extinction of Bachman’s Warbler. Global warming is causing significant shifts in the range and population size of most North American birds.

For migratory birds, changes in population sizes can be difficult to understand. According to data from the Breeding Bird Survey, Wood Thrushes show a steep decline in the three northern New England states over the past 40 years. Why? Could it be events happening in New England during the breeding season? Could it be destruction or degradation of wintering habitat in Central America? Could it be events happening during migration? Change may be certain but understanding why change occurs is often hard to understand.

One of most spectacular changes in abundance of a Maine bird concerns a shorebird called the Red-necked Phalarope. Red-necked Phalaropes breed at high latitudes on the tundra in both the New World and Old World. On the breeding ground, phalaropes largely feed on mosquito larvae and other aquatic insects in thaw ponds on the tundra. The phalaropes feed in an unusual manner by swimming rapidly in a small circle, drawing prey items to the surface of the water.

To capture the small prey, phalaropes take advantage of the high surface tension of water. By rapidly opening its upper and lower bills with the tips in the water, a phalarope causes water to flow up the bill, following a surface tension gradient right into the back of the mouth. The unsuspecting prey items are drawn into the mouth with the water become lunch. A personal conveyor belt!

Red-necked Phalaropes can be found on inland bodies of water during migration. Thousands can be found on saline lakes in western North America on their way to wintering grounds. These hardy birds winter at sea where they feed on zooplankton, the collection of small crustaceans and other invertebrates found near the surface of the ocean feeding in turn on single-celled algae (phytoplankton). Phalaropes are well adapted to feed on the plankton with their long, thin bill.

Forty years ago, millions of Red-necked Phalaropes stopped in the lower Bay of Fundy during their fall migration. The most spectacular concentrations were in the vicinity of Lubec and Eastport, Maine. In particular, the phalaropes were found in the roiling waters between Campobello Island, N.B., Deer Island, N.B. and Eastport. These oceanographic conditions produce the Old Sow, the largest whirlpool in the Western Hemisphere.

In late August of 1976 and 1977, two million phalaropes were estimated to be feeding in this small area. What a spectacular site that must have been! In 1983, 300,000 phalaropes were counted. But thereafter, the phalaropes disappeared. We don’t know where the phalaropes went.

In recent years, phalaropes have been seen in the Eastport-Deer Isle region although in much smaller numbers than the heydays of the 1970’s. The phalaropes seem to occur where large numbers of their favored prey, a small crustacean called Calanus finmarchicus, are abundant. It is possible that the Calanus population crashed in the area in the early 1980’s, forcing the phalaropes elsewhere. On a global scale, Red-necked Phalaropes seem to have a stable population.

[First published on September 15, 2013]

Recent AOU Checklist Changes

January 19, 2014 By Herb Wilson in Field Guides, Taxonomy

Recognizing the limits of species is one of the great challenges of biology. Some species are remarkably variable; humans with our ranges of skin color provide a nice example. On the other hand, some separate species can scarcely be separated based on their morphology. The Willow Flycatcher and Alder Flycatcher are dead ringers for each other yet the distinctive songs of the males ensure that only Willow females will mate with Willow males and Alder females with Alder males.

A branch of biology called sytematics is devoted to identifying the limits of species and to understanding the relationship among the species. We still follow the basic classification scheme erected by Charles Linnaeus nearly 300 years ago. Closely related species are placed in the same genus. Closely related genera are placed in the same family and so on upward in the scheme to orders, classes and phyla.

Systematic classifications were initially based on the structure of organisms. Over the years, systematists have used other traits to help understand species limits and interrelationships. Behavior can be an informative trait. The ability to interbreed is used by some systematists as an indication of a “good” species. In the past few decades, comparisons of DNA has greatly clarified and refined our understanding of the relatedness of various groups of organisms.

Like any scientist, a systematist regards her understanding of the relationships of a particular group of organisms (like the shorebirds, for instance) as a working hypothesis. The hypothesis is provisionally regarded as true but needs continued testing. As our knowledge grows, hypotheses have to be rejected. Like any science, systematics is a dynamic field.

A nice example of our changing understanding is the Yellow-rumped Warbler. Western birds have yellow throats while eastern birds have white throats. These birds were initially treated as separate species. The Black-fronted Warbler in Mexico and Goldman’s Warbler in Guatemala, similar to Myrtle Warbler and Audubon Warbler, also were described as distinct species. However, all of these four species based on additional systematics work were combined into the Yellow-rumped Warbler in 1973. It’s possible that some or all of these forms will be split back into separate species in the future.

To keep track of these taxonomic changes for birds, the American Ornithologists Union erected a Check-list Committee. This committee is charged with producing the Check-list of North American birds, the official source on the taxonomic classification of birds of North and Middle America. The current version is the seventh, published in 1998. You can see the check-list on line at http://www.aou.org/checklist/north/print.php

The committee monitors the publications on bird systematics and revises the check-list if necessary. The committee usually publishes a supplement in the ornithological journal, the Auk, every July to describe any changes to official Check-list.

Most of the changes in the 2013 supplement pertain to birds of Middle America so I will not cover them here. The supplement does describe some taxonomic changes to some shorebirds: Surfbird, Buff-breasted Sandpiper, Spoon-billed Sandpiper, Broad-billed Sandpiper. The Buff-breasted is a regular passage migrant in Maine and Ruff is an occasional vagrant. Each of these species was formerly placed in its own unique genus. Recent systematics work has shown these species are not sufficiently different from other shorebirds to merit their own genus. Each of these five genera has now been eliminated and all five species are now placed in the genus Calidris, the genus that includes a number of shorebirds including Sanderling, Semipalmated Sandpiper, Red Knot and Dunlin. If you are a stickler for the scientific names of birds, make those changes in your field guide.

The other change may affect your life list if you have birded in the West. The Sage Sparrow has been split into the northern Sagebrush Sparrow and the southern, Californian Bell’s Sparrow.

[First published on September 1, 2013]