Irruptions

By 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

By 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

By 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 19th 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

By 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

By 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

By 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.

American Pipit Summit Lake Mt. Evans COHowever, 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

By 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

By 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]

Yellowleg Identification

By in Identification

Shorebird migration is peaking now in Maine as southbound birds head for warmer climes for the non-breeding season.  We get two cracks a year with these passage migants as they move through Maine each spring and late summer/fall.

Two species of yellowlegs, Lesser Yellowlegs and Greater Yellowlegs, are common migrants through Maine.  They are more likely to be seen on coastal mudflats but regularly appear in inland wetland areas as well.  The bright yellow legs make it easy to identify a large sandpiper as a yellowlegs but which one is it?  Separating the two is an identification challenge.

As befits the name, the Greater Yellowlegs is larger than the Lesser, weighing twice as much as its smaller relative.  Greater Yellowlegs are chunky, bulky birds compared to the slim, graceful shape of Lesser Yellowlegs. A Lesser is 10-11 inches long while a Greater is 14-15 inches long.  Nevertheless, it is difficult to accurately gauge the size of birds when there are not other known species around to provide a yardstick.  Fortunately, other characteristics can be used to distinguish the two species.

A somewhat subjective but useful feature is the facial appearance.  The face of a Lesser appears has a kind, gentle demeanor compared to a Greater’s harsher mien.

A Greater with its bulkier body has a relatively small head and thin neck.  The neck frequently has a kink in it, like a heron.  The breastbone is strongly angled and bulges from the chest.  The neck of a Lesser is relatively thick and shorter, rarely showing the kinked appearance.  The head does not seem small relative to the body.

The bill of a Greater is absolutely and relatively longer (relative to the head).  You can use the length of the head viewed from the side as a measuring stick.  The bill length of a Greater exceeds the length of the head.  Measurement of museum specimens indicates the bill averages about 1.3 times the length of the head.  A Lesser’s bill is pretty close to the length of the head.

The bill of a Greater Yellowlegs is slightly upturned compared to the straight bill of a Lesser.  Outside of the breeding season, the bill of a Greater Yellowlegs is broader at the base and usually two-toned (gray at the base and black at the tip).  The tip of the bill is somewhat blunted.  A Lesser has a straight, thin, needle-like bill with a sharp tip.  The bill is uniformly black along the length.

Your ears can provide the most convincing cues for a correct identification.  A Greater Yellowlegs gives a loud, piercing whistle that is often rendered as “tew tew tew”.  A Lesser Yellowlegs gives a softer, less strident call rendered as “tu”, that may be given as single notes or a couple of notes.  A great website to hear recordings of these two species is www.AllAboutBirds.org; just type in the species name of interest in the search box and press Enter.  On the species screen, you will see a tab called Sound.  Click on that tab and you will be taken to  links for a number of recordings.

The difference in the vigor of the calls is reflected in the foraging behavior. A Greater is a hyperkinetic forager, dashing back and forth along a mudflat.  A Lesser is a more sedate, less frenetic forager.

Most of the other large members of the sandpiper family that pass through Maine lack yellow legs and hence are not likely to be confused with one of the two yellowlegs.  However, Stilt Sandpipers can cause some confusion.  These birds have greenish-yellow legs and are about the size of a Lesser Yellowlegs.  In fact, they often forage with Lesser Yellowlegs.  Proportionally, the head of a Stilt Sandpiper seems large.  The bill is relatively heavy and shows a pronounced droop.

[First published on August 18, 2013]

Recent Ornithological Literature

By in Bird Conservation, Recent Ornithological Literature, Reproduction

In today’s column, I’ll provide a summary of some recent scientific articles on birds that occur in Maine.  All of these articles appeared in the most recent issue of the Wilson Journal of Ornithology.

Christina Masco describes research she did in Maine on Appledore Island on interactions among nesting Great-blacked Gulls.  These gulls nest at high density and a pair aggressively defends its small territory (about 350 square feet) throughout the breeding season.  Real estate on Appledore is hard to find so most territories abut several other territories.

If an intruding gull enters the territory of a gull, aggressive interactions ensue.  But some of these fights are avoided by the use of threat displays, warning another gull that it should leave or prepare for a fight.

One of these threat displays is a distinctive vocalization that sounds like “yeow”.  This call tells an adjacent bird that an attack is imminent.  Masco used play-back experiments to determine if Great Black-backed Gulls can recognize individuals based on their “yeow” calls.  She found that a territorial gull will hold alert postures longer in response to unfamiliar “yeows” compared to the “yeow” given by a mate or neighbor.

This finding is an example of the dear enemy phenomenon.  Animals get used to adjacent enemies and tend to respond less vigorously to them than to strangers.  In other words, it is better to deal with the devil you do know rather than the devil you don’t know.

The Eastern Wood-Pewee is a fairly common breeding bird throughout our state.  Felicity Newell and colleagues wrote an article describing surprising reproductive traits of this species in Ohio.

Before this research, ornithologists had presumed that Eastern Wood-Pewees were monogamous, with a pair-bond cementing one male and one female together.  Newell and colleagues present research that challenges this assumption of mate fidelity.  They color-banded 79 pewees with unique color combinations.  Much to their surprise, they found one male that was simultaneous feeding young at two different nests.  The same male was polygynous (mated to more than one female) the following year as well.

Polygyny is advantageous for a male because he can father twice as many young as a monogamous male.  Polygyny can be disadvantageous for females because their presumed faithful mate is devoting half of his time to a different family.

Aside from habitat destruction, bird mortality from bird-window collisions represent the greatest human-associated source of bird deaths.  Bird deaths from window collisions number in the billions.

Dan Klem of Muhlenberg College has been studying bird-window collisions for over 30 years.  Klem and Peter Saenger wrote an article in which they evaluate the effectiveness of selected visual signals to deter bird-window collisions.

Their work was based on a carefully controlled experiment where they placed wood-framed picture windows in an area of mowed pasture in Pennsylvania.  They placed a platform feeder 10 meters from each window.

Experimental treatments included using clear glass, reflective (mirrored) glass, ORNILUX Mikado glass, and Acopian bird savers (vertically hung parachute cords spaced three or four inches apart).  The ORNILUX glass reflects more ultraviolet light than other types of glass as well as the Acopian bird savers.  Unlike humans, birds can see a portion of the ultraviolet spectrum.

Klem and Saenger recorded the number of bird collisions (some of which were fatal) with the picture windows equipped with the three different types of glass.  They also tested the effectiveness of the Acopian bird savers.

In one experiment testing the three types of glass, no difference in total collisions was found.  However, fatalities were lowest at clear glass (10%) and highest at the ORNILUX glass (58%).  The ultraviolet-reflecting glass had the opposite effect expected.

A second experiment showed that parachute cords were very effective in preventing collisions, hung outside of either clear or reflecting glass.

Visit http://www.birdsavers.com/ to learn more about Acopian bird savers.

First published on August 4, 2013]

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