Maine Bird Tour – I

From June 16 to June 23, 2007, I led an eight-day whirlwind birding tour of Maine for six members of the Maryland Ornithological Society. Three of the group (Al Haury, Dottie Mumford and Bobbi Reichwein) were on the similar tour I led in 2003. Linda Baker, Mary Gruver-Byers and Brent Byers were new additions. Brent took the marvelous photographs that are inserted into the text. I’ll devote three columns to the highlights of the trip, sharing information on some of my favorite birding spots in the state.

After picking up the group at the Portland airport around noon on June 16, we drove to Capisic Pond for a picnic lunch. Both Orchard Orioles and Baltimore Orioles serenaded us as we ate. Other birds there were Warbling Vireos, Yellow Warblers, American Redstarts, a Green Heron and tons of Red-winged Blackbirds and Common Grackles. An Indigo Bunting sang from the top of a tree.

With our appetites sated, we headed for Evergreen Cemetery. This site is best during the spring migration but has much to offer at other seasons. We had good warbler diversity: Black-throated Green Warblers, Chestnut-sided Warblers and Common Yellowthroats being particularly common. A Rose-breasted Grosbeak first sang for us and then posed in full view. A Fish Crow gave its hoarse uh-uh call, making a nice addition to our trip list.

Next we headed to Scarborough Marsh. A quick stop at Dunstan’s Landing produced Glossy Ibis, Great Egret, Snowy Egret and Mallards. A Willet called its pill-will-willet cry, flashing the white patches on its wings as it flew across the marsh.

We made the short drive to Eastern Road in search of sharp-tailed sparrows. Scarborough Marsh is the perfect spot for these salt marsh sparrows because both the northern Nelson’s Sharp-tailed Sparrows and southern Saltmarsh Sharp-tailed Sparrows nest here. Occasionally, hybrids are seen.

On a calm June morning, males of both species will sing from the top of salt marsh grasses. However, we were at Eastern Road in the afternoon of a windy day. The sparrows could be heard singing but were reluctant to show themselves for more than a fleeting glimpse.

Our last stop of the day was Pine Point. At least 30 Bonaparte’s Gulls were present. The expected Common Terns were joined by a couple of Arctic Terns. The terns were flying close enough to allow us to see the uniformly gray upper wings of the Arctic Terns and distinctive black wedge near the tip of the wings of the Common Terns. A couple of Least Terns were present as well, distinguished by their small size, yellow bill and white forehead. As we were getting ready to call it a day, I saw a ghostly white tern fly by with a very long tail – a Roseate Tern!

After a nice meal at a Scarborough seafood restaurant, we drove to Sanford for the night. Our first stop in the morning was the Kennebunk Plains, the largest remnant of grassland in the state. Despite our fairly early start, we were not early enough for one of our target species, the Grasshopper Sparrow that breed in small numbers here. We did however have excellent views of the other specialties of the area. Upland Sandpipers gave their eerie whistles. Vesper Sparrows were in full voice and easy to see. Prairie Warblers sang from the short trees ringing the plains. Savannah Sparrows were abundant and a few Eastern Meadowlarks, a species of concern, were singing as well.

A female Northern Harrier was hunting over the grasslands along Maguire Road. At the power line cut, Eastern Towhees and a Yellow-breasted Chat were vocalizing.

The next stop was Laudholm Farm, a beautiful site with varied habitats. A Northern Mockingbird greeted us in the parking lot. The fields were full of Bobolinks. A walk through some of the woodlands produced a Red-eyed Vireo, one of whose songs was an excellent mimic of a Great Crested Flycatcher. A House Wren sang vigorously from scrubby vegetation.

A walk along the beach produced a number of Northern Gannets, some flying quite close to shore. Least Terns loafed on the beach. A highlight of the beach walk was a pair of Sanderlings in their reddish breeding plumage, quite a contrast to the pale winter plumage we normally see here.

Stops at Biddeford Pool and Eastern Point Sanctuary did not yield any surprises. We ended the day with a walk through the Saco Heath. The boardwalk provides easy access to this charming bog. Highlights were a Canada Warbler, singing Hermit Thrushes and a Blue-headed Vireo in the surrounding woods. Other people on the trail saw a moose but we had to be content with seeing only the tracks.

Yellow-bellied Sapsuckers

Today’s column is about a jazz drummer with a sweet tooth. No, we’re not talking about Gene Krupa. The drummer is one of our more unusual woodpeckers, the Yellow-bellied Sapsucker.

The sapsucker is named for its habit of creating shallow holes, called sap wells, in the bark of trees. The sap that oozes into the wells provides food for the sapsuckers. The sap is a fluid carried in phloem cells of the tree, just beneath the bark. This fluid is rich in organic nutrients, particularly the sucrose (table sugar). These compounds are created in the leaves of the tree by the process of photosynthesis and then carried through the phloem to all parts of the tree. The phloem is essentially a circulatory system for the plant, carrying sugar to parts of the tree that cannot photosynthesize and hence make their own food. In the summer, 25% of the phloem sap is sugar. That’s a sweet treat!

The sapsucker is a bit like a vampire, exposing the phloem cells and drinking the sucrose that oozes out. Unlike most woodpeckers, a sapsucker has a tongue that is brush-tipped, just the ticket for lapping up sap.

The sap wells in the phloem are usually rectangular in shape. I expect you have seen these sap wells before, arranged in neat rows parallel to the ground. A sapsucker tends the sap wells daily, making sure they to ooze sugar by enlarging the area of the well.

In the early spring before the trees have started to photosynthesize, the sapsuckers make holes in a different kind of circulatory system of the plants, the xylem. The main role of the xylem is to transport water from the roots to the aboveground parts of the tree but does contain a little sugar. The sugar in the xylem gets the sapsuckers through the latter part of the spring until the trees start to photosynthesize. The xylem wells are circular in shape and are not enlarged through time.

Over 1,000 species of trees may be used by sapsuckers across their geographic range. In Maine, sapsuckers are usually found in early-growth forests rather than mature, climax forests. Quaking Aspen, Paper Birch and Red Maple are commonly used for the creation of sap wells.

Sapsuckers will use apple trees for the creation of sap wells, causing orchard growers concern about the health of their trees. However, sapsuckers do not generally cause serious direct harm to trees, although the wells may encourage the arrival of insects that are harmful.

The dependence of sapsuckers on the phloem and xylem of birds requires sapsuckers to be migratory. Their breeding range spans the lower half of Canada, New England, Michigan, Wisconsin, Minnesota and North Dakota. The xylem and phloem of trees in these regions are frozen solid during the winter. So, the Yellow-bellied Sapsuckers withdraw to the southeastern and Gulf states into Central America for the winter. We see our first sapsuckers each spring about the middle of April.

Despite the efforts of a sapsucker to ward off other birds from its wells, many birds do take advantage of the sugar in the sap wells or the insects attracted to the sugar. Ruby-throated Hummingbirds seem to have a particularly close relationship. A female hummingbird often builds her nest close to sap wells and follows sapsuckers during the days, as they work their “trap lines”. Some ornithologists have noted that the migration of Ruby-throated Hummingbirds is closely linked to the migration of sapsuckers.

Sapsuckers do supplement their diet with insects. Foraging for insects is particularly important when parents are feeding nestlings. The young sapsuckers need protein to grow. A sugar diet alone is not sufficient for their proper development. Even so, adult sapsuckers have been seen to capture an insect and then dip it into a sap well before feeding the insect to a chick.

Most woodpeckers drum on resonating surfaces as a means of communication. Sapsuckers have an unusual, syncopated style to their drumming. A typical drum usually starts with several rapid strikes, often increasing in frequency, as an introductory roll. Then, after a brief pause, the sapsucker will strike in a slower, less regular cadence.

Like a jazz musician, sapsuckers improvise. No two drums are alike, even from the same bird.

The sapsuckers are particular about the type of tree they use for their drumming, using the trees that produce the loudest noises of the trees available. The trees chosen also yield the lowest sound frequencies. Lower-pitched sounds carry better in a closed forest habitat than higher-pitched sounds.

Most of the sapsucker drumming you hear comes from males although females also drum. Female drums are briefer and softer than the male drums.

[Originally published on June 2, 2007]

Maine Butterfly Survey

Rather than writing on birds in today’s column, I’ll devote this space to another group of winged creatures, the butterflies. In particular, I want to announce the start of a five-year project to produce an atlas of the butterflies of Maine. The project is called the Maine Butterfly Survey (MBS). See the website at http://mbs.umf.maine.edu/. The MBS will rely heavily on volunteers throughout the state.

Despite the fact that butterflies are conspicuous in our gardens and fields, our knowledge of the distribution of butterflies throughout the state is fragmentary. In preparation for this atlas project, Phillip deMaynadier, a wildlife biologist at Maine Inland Fisheries and Wildlife, and Reggie Webster, a Canadian expert on the taxonomy of butterflies, searched the literature, museums and private collections for records of Maine butterflies. They found nearly 9,000 records, providing a baseline for the atlas project.

Their report, available in pdf format at the MBS website, provides township-level maps for the 114 species of butterflies in the state as well as detailed information on rare species in the state. The map of the distribution of the Monarch butterfly, an easily identified species, shows how much of the state needs to be sampled.

The Maine Butterfly Survey (MBS) follows on the heels of other butterfly atlas projects in New England and maritime Canada. Connecticut, Massachusetts and New Brunswick have recently completed atlases and Vermont is in its final year of such a survey. The coordinators of the MBS are Phillip and Reggie as well as Ron Butler of the University of Maine-Farmington and me.

Butterflies are a worthy subject for study because they contribute a colorful and conspicuous component to our state’s biological diversity. Butterflies play an important role in terrestrial and wetland ecosystems by serving both as pollinators of many wildflowers and prey (both caterpillars and adults) to larger species ranging from dragonflies to birds. Butterflies are also widely recognized for their value as ecological indicators of ecosystem stress due to such factors as climate change, pollution, and habitat loss. Without thorough baseline knowledge of the distribution and relative abundance of butterflies, it is impossible to gauge the magnitude and direction of population changes in the future to a variety of environmental variables.

The MBS will use the townships as the sampling unit. There are 711 townships in the state of Maine, most of which are roughly the same size. To document the presence of a species in a township, a voucher must be submitted. The voucher can be a specimen that is collected with a net and then submitted as a preserved specimen to the MBS for confirmation of the species.

Although there is no evidence that collecting has every led to the demise of a butterfly population, some people are reluctant to kill a butterfly in the name of science. Two other types of vouchers are acceptable for the MBS that do not depend on the collection of butterflies. Close-up digital photographs or print photographs are acceptable as vouchers. Also, road-killed specimens collected from road shoulders are acceptable vouchers as well. The number of butterflies killed by automobiles is appallingly high.

Voucher specimens are needed for any butterfly atlas so that scientists can independently verify the identifications. Sight records may be wrong and cannot be independently verified after the fact. The taxonomy of butterflies is unsettled for some species. Future taxonomists may find great value in the vouchers provided by the MBS.

I hope that you will consider becoming a volunteer for the MBS. You can contribute as few or as many vouchers as your time allows. Sampling areas are not assigned so you can sample anywhere throughout the state.

We ask that every prospective volunteer attend one of our workshops to learn the details of voucher preparation, collecting techniques and preparation of the data forms that must accompany your vouchers. Every workshop participant (eighteen years of age or older) will be given a collecting net, a specimen jar and glassine envelopes for storage of your vouchers.

The next workshop will be held on Saturday, July 14 at the Delta Institute of Natural History in Bowdoin from 9:30 AM until 3:30 PM. You’ll hear a lecture on butterfly biology and identification from me as well as instructions on data collection and butterfly netting from Ron and Phillip. If the weather is fine, we will spend part of the afternoon in the field. Please contact me soon via email to reserve a spot at the workshop; the limit is 30 people. I hope to see you in Bowdoin.

[Originally published on May 19, 2007)

Comfort Behavior in Birds

As spring migration picks up the pace, all of us are excited about the return of Maine’s migratory breeding birds. Particularly during migration, birders eagerly try to see as many species as possible in a morning. It’s great fun to find that wayward Kentucky Warbler or Blue Grosbeak. However, I suggest that a closer, leisurely look at even the most common birds can be rewarding.

Like other animals, birds need to keep their skin clean and healthy. Feather maintenance is a priority as well. Most of these body-care behaviors are said to be stereotyped; that is, the birds do these same behaviors in the same way all of the time.

One of the most widely recognized stereotyped behaviors birds use to keep clean is bathing. A bird typically takes a bath by first immersing and then suddenly raising the head and then rapidly beating the wings. This bathing behavior is inborn. Young Northern Goshawks on the bare ground are induced to try to bathe when they see a brood-mate splashing in water.

In arid environments, birds take dust baths rather than water baths. It is thought that the dust removes some of the oils from the bird’s skin, which would otherwise cause matting of the feathers.

Usually, birds engage in preening after taking a bath. Preening involves the application of waxy oils to the feathers to preserve feather moisture and flexibility, waterproof the feathers and clean the feathers. The waxy oils are produced by the preen gland or uropygial gland, located on the rump at the base of the tail.

To preen, a bird rubs its bill against its preen gland to pick up some secretions from the preen gland and then uses its bill to apply the waxy oils to all the feathers of its body.

The preen glands of some birds also produce secretions that protect the feathers from feather-digesting bacteria and fungi. Other secretions may deter feather lice. In a group of birds called the hoopoes, the preen gland produces a foul-smelling substance that deters mammal predators. Hoopoes are the skunks of the bird world!

Birds spend a considerable amount of time preening. Many birds will preen their feathers once an hour. While preening, the wing and tail feathers are drawn through the bill to restore their shape. Feather parasites may be removed by preening as well.

Herons and egrets produce a peculiar type of feather called powder down. The powder down feathers are never molted but rather grow continuously. The claw of the middle toe of each foot has a comb-like undersurface that is used to crush the tips of the powder down feathers. The talcum-like powder down is spread over the feathers with the comb-claw. The powder down apparently has the same function as oil from the preen gland. The preen glands of herons are vestigial (like a human appendix) and therefore herons do not oil their feathers.

A less known form of feather and skin maintenance in songbirds is called anting in which a bird treats its feathers with ants or some other substitute material. Many ants give off pungent chemicals when they are disturbed. These chemicals serve to kill feather lice and other skin and feather parasites.

Some birds that engage in anting behavior do so passively. For instance, American Crows will spread its wings and sit down on an ant colony. The angry ants crawl through the crow’s feathers, reducing the number of parasites.

In active anting, a birds picks up one or more ants in its bill and then actively jabs them among its feathers. The bird usually ants more vigorously on the underside of its body, particularly under the wings and tail. Sometimes, an anting bird eats the ants after anting; at other times, the ants are released. Birds that practice active anting behavior include the orioles, jays and starlings.

Some songbirds don’t rely on ants for anting. Beetles, bugs, wasps, raw onion, vinegar, cigarette butts, walnut juice, lime fruit, orange peeling and mothballs may be picked up for use in anting.

Anting in Common Grackles has been observed a number of times with ants and substitute materials, including mothballs. Group anting by grackles has been described in Ohio. A woman had put out a large number of mothballs in her flower gardens to keep rabbits out. Grackles discovered the mothballs and began using them to ant. Up to two dozen grackles were seen anting at once!

Anting has been reported widely in the songbirds. Over 250 species from over 40 families have been reported to ant.

[This column originally published on May 5, 2007]

Threats to Birds and Bats by Wind Turbines

In the last column, I reviewed some of the talks I heard at the recent Wilson Ornithological Society meeting in Massachusetts. I’ll discuss one last talk that has particular relevance to Earth Day.

Everyone is aware that carbon dioxide levels have been steadily increasing for the past 150 years. Most of this increase is due to industrialized nations, burning fossil fuels in our automobiles and coal to generate heat and electricity.

Carbon dioxide acts as a so-called greenhouse gas, trapping heat that is radiated into the atmosphere from the earth’s surface. The recent report “Climate Change 2007” by the International Protocol on Climate Change (http://www.ipcc.ch/) and the release of the movie “An Inconvenient Truth” featuring Al Gore have won over many skeptics who formerly doubted that significant global warming is occurring.

Environmentalists are ardently seeking greener forms of generating electricity that release little or no carbon dioxide. Wind power, a headline topic over the past year in Maine, offers the promise of a clean, renewable resource.

As with any technology, reasonable people can disagree about the relative costs and benefits. Opponents of wind power cite the disruption of scenic views and the noise that some turbines make as they turn in the wind. In most areas, the wind does not blow constantly and consequently there are times when wind will be too weak to generate electricity. Hence, a wind farm will not allow less efficient generating plants to be removed from the electrical grid. Those plants will be needed to generate power when the wind is not strong enough. Wind farms in remote areas require significant lengths of roads to be built, fragmenting the landscape.

The bird and bat mortality at wind turbines is an effect that makes many question the environmental costs of wind farms. Like real estate, location of a wind farm is a critical factor in determining the number of birds and bats that are killed. Some birds may be killed by direct contact with the rotating turbines. Other birds may be disoriented at night by the lights required on all towers taller than 200 feet. The birds may fly into a tower or guy wire with lethal results.

Quantifying the number of birds and bats killed is challenging, particularly in forested landscapes. Some birds killed by turbines may fall and remain in the forest canopy. Scavengers like foxes, coyotes and burying beetles may remove killed birds before they can be found by researchers.

Wind farm proponents admit that some bird and bat mortality is inevitable. However, they argue that the reduction in carbon dioxide emissions by using the wind to generate power improves the planet for all organisms. Deciding whether it is better to approve or deny a wind farm proposal on these grounds is a question for an environmental economist. There are no easy answers.

At the Wilson Ornithological Society meeting, I looked forward to hearing Rhonda Millikin speak on her work on the response of nocturnal migrating birds to wind turbines. She has pioneered a radar-acoustic system to determine how birds and bats respond to spinning turbine blades.

She applied her technology at six wind farms in Alberta in agricultural landscapes and one wind farm in Ontario in a forested landscape. She tested the hypothesis that nocturnal bird and bat migrants could avoid the turbines.

Millikin measured the avoidance of turbines by looking for changes in flight behavior as birds and bats approached the blades. She found that birds were able to detect the turbines from a distance of at least 500 yards away by showing that the birds slowed their flight speed and increased their calling rate. They also flew a bit higher, rarely dipping below the height of a wind turbine. Millikin argued that birds may learn to avoid turbines.

Bats are a different story. As they approach a turbine, they climb to an altitude equal to the spinning blades and vary their flight direction. They respond quite late to the towers, often not trying to fly to safety until they are within 50 m of the turbine. Because of their erratic flight and slow responses, bats have a difficult time traversing a line of turbines. Millikin claimed that a bat is about five times as likely as a bird to be killed when flying in the vicinity of a turbine.

Millikin ended her talk by noting particular habitats where migrating birds are reluctant to change their course. These habitats are ridges, riparian habitats and ravines or gulches with steep sides. Migrating birds have a strong attraction for these areas as they migrate and hence are less likely to avoid turbines. Wind turbines in these types of habitats pose higher risks for birds and bats.

[First published on April 21, 2007]

Highlights from the 2007 Wilson Ornithological Society meeting

I recently attended the annual meeting of the Wilson Ornithological Society, held in the Boston area this year. In today’s column, I’ll describe some of the new research presented at the meeting.

The meeting began with a talk on Alexander Wilson, the father of American ornithology. The Wilson Ornithological Society is named in his honor. Wilson was born in Scotland in 1766. In his early adulthood, he was a weaver and peddler, a poet and a labor union organizer. He immigrated to Philadelphia in 1794, fearing he would be jailed in Scotland.

In In Delaware, he taught school and began drawing to alleviate his frequent depressions. He had the good fortune to meet William Bartram, the most famous and influential naturalist in North America.

In 1803, Wilson decided to describe and paint all of the birds of North America. Over seven years, he traveled over 10,000 miles studying birds. The first volume of the “American Ornithology” was published in 1808 with a second volume in 1810. Six volumes were published in 1813, the year that Wilson died. One last volume was published posthumously in 1814. All told, 264 species were covered in the nine volumes. Wilson’s volumes preceded John James Audubon’s by a decade, establishing Wilson as the father of American ornithology.

Wilson and Audubon had an amicable meeting in Louisville where Audubon was living at the time. Wilson asked Audubon to buy a subscription to “American Ornithology” and must have been embarrassed when Audubon showed him some of his own paintings of birds!

One of the highlights of this year’s meeting was a chance to see some of Wilson’s original paintings and the specimens on which they were based (including a Bald Eagle) at the Museum of Comparative Zoology at Harvard. Wilson’s paintings are accurate representations of the birds he saw but are not the artistic masterpieces that Audubon produced. It is not unfair to state that Wilson was an illustrator and Audubon was an artist.

Bob Curry and his students at Villanova University gave a talk on the hybrid zone between Black-capped Chickadees and Carolina Chickadees in southeastern Pennsylvania. They used DNA markers to determine if hybridization was occurred. Three sites were sampled: one southern site at Great Marsh where only Carolina Chickadees occur, an intermediate site in Nolde Forest where most individuals are hybrids and a northern site at Hawk Mountain with mostly Black-capped Chickadees but with some evidence of hybridization occurring.

Comparison to earlier studies indicates that the hybrid zone has shifted north about 15 miles over the past 15 years. The hybrid zone, now about 30 miles wide, seems to have broadened in recent years as well.

David Lahti from the University of Massachusetts gave a talk on the advantages of blue-green bird eggs. Most bird eggs are cryptically colored. Why would birds like American Robins lay blue-green eggs that should be easier to find for a predator than speckled or dark eggs?

Lahti suggests that the blue-green pigment in the eggs serves as a parasol for the developing eggs. In other words, the pigment may protect the developing embryo from the solar radiation in forest environments. He was able to show in the laboratory that the pigment keeps light rays from entering the egg, preventing the eggs from heating up.

Jim Chace from Salve Regina University in Rhode Island described research he and his students have been doing in Vermont on breeding Canada Warblers. Various sources of information, including the Breeding Bird Survey, indicate this species has been declining for the past 30 years. Yet, little is known of the characteristics of the habitat that males use when establishing territories. By comparing the vegetation within Canada Warbler territories with randomly chosen habitats, Chace and his students showed that males preferred habitat with denser shrubs and saplings and a greater ground cover of moss than randomly chosen sites within the large study area. This knowledge provides environmental managers with ways to improve habitat for Canada Warbler nesting.

Steven Reinert of the Block Island Banding Station in Rhode Island presented a talk on the bias of mist-net captures in monitoring landbird fall migration. Over the past 37 years, the Audubon Society of Rhode Island has hosted an annual Block Island Birding Weekend. Expert birders lead small groups of birders around this island, identifying and counting all birds during the middle of the fall migration season. Reinert used thee counts to compare to the relative abundances of landbirds he and his associates capture in their mist-nets over the same weekend. Over the 37-year period, 152 species were identified by sight and only 91 captured in nets. Most landbirds are absent or under-represented in mist-net captures.

[Originally published on April 7, 2007]

For the Birds – Red-winged Blackbirds

Con-ka-ree! The Red-winged Blackbirds have returned; spring must be on the way. The March arrival of these beautiful birds is a welcome sight as a Maine winter starts to give way to spring. The males are all black except for a brilliant red patch, edged in yellow on each wing. The smaller females are drab and inconspicuous, in their mottled brown and white plumage.

Red-winged Blackbird is one of the most abundant birds in North America. On some Kansas Christmas Birds Counts, over 6 million red-wings in massive flocks have been counted in a 175 square mile area! Abundant breeders throughout Maine, red-wings depart for more southerly climates during the winter. Their breeding range extends northward to southern Alaska and southward to Costa Rica. In North America, Red-winged Blackbirds nest in every one of the lower 48 states and all of the Canadian provinces.

Red-winged Blackbirds breed in marshes and other areas with dense, grassy vegetation. The males perch on shrubs and the tops of cat-tails. Red-wings are therefore easier to see than woodland birds. The abundance and high visibility of Red-winged Blackbirds make them good subjects for ornithological study. Not surprisingly, they are one of the most studied North American birds.

These birds are unusual among North American songbirds in that the males are polygamous, that is a male may have many mates. It is not uncommon for a male red-wing to have seven or more females in its territory and at least one male had 15 females in his harem. DNA analysis indicates that not all of the offspring produced by females on a male’s territory are sired by him. That means that females sometimes engage in “extra-marital affairs” with other males when their mate is not looking. In fact, these dalliances, referred to as extra-pair copulations by ornithologists, are the rule rather than the exception in most species of birds in which paternity has been tested by DNA analysis.

Red-winged Blackbird males arrive on the breeding grounds ahead of the females. The dominant males stake out territories that they proclaim as their own with songs and displays. One of the most common territorial displays is called the Song Spread. The male exposes the red patches on its wings and sings is metallic con-ka-ree song. Younger and weaker males are usually not able to establish a territory and breed.

The females arrive a week to several weeks later than the males. They then choose a mate based not on the characteristics of the male but rather on the quality of the territory. Usually, the healthiest and strongest males lay claim to the best territories. Only seven percent of second-year males are successful in establishing a territory and siring young. The percentage rises to 57% for males in their third year of life.

When you see a male Red-winged Blackbird at your feeder or in a marsh, you may not be able to see the red on the wings. Sometimes, even the yellow margin of the red patch is not visible. The red patches are called “coverable badges” by ornithologists. Coverable because they can be hidden and badges because they signify authority. When a dominant male is approached by another male attempting to drive the first male off of its territory, the territory owner will expose its badge. This aggressive display tells the intruder to back off. Subordinate males make sure they don’t uncover their badges in the presence of dominant males to avoid being attacked.

Similar behavior can be seen in schoolyard bullies. A 10-year bully adopts a swagger to try to intimidate smaller children, uncovering his behavior or “badge”. However, in the presence of a 13-year old bully, the 10-year old bully alters his behavior, covering his “badge”, so as not to offend the bigger bully.

Interestingly, the color red seems to signal a willingness to fight in other species of Maine birds. Male Ruby-crowned Kinglets expose the red on their crowns only as an aggressive behavior. Similarly, Eastern Kingbirds flash their red crown feathers as warnings to other kingbirds during the nesting season.

Outside of the nesting season, Red-winged Blackbirds are well known for forming large flocks that roost together. Sometimes, other species like Brown-headed Cowbirds, Common Grackles and European Starlings may roost with them. These flocks pose significant threats to agriculture. A large flock of red-wings can devastate crops of corn, sunflowers or rice. Farmers have invested large amounts of time and effort in ways to keep red-wings away from their crops. The result of these efforts is that humans now pose one of the most significant sources of mortality for Red-winged Blackbirds.

[Originally published on March 17, 2007]

For the Birds – Cold and Unfeathered Legs

In the last column, I described some of the ways that birds are able to survive the challenges of cold weather. I did not have enough space to describe how birds keep their unfeathered lower legs from freezing. Several readers inquired about this problem for birds in cold environments. I’ll tackle that problem this week, including a foray into some chemistry.

For most birds only a portion of the legs is unfeathered. The long bone you see without feathers is called the tarsometatarsus. This compound bone corresponds to the bones of your foot. The tibia (shin bones) and the femur are usually well feathered. So, it’s the elongated foot bones and toes of birds that have no insulation.

The unfeathered lower parts of birds’ legs have a very high surface area, just the ticket for losing heat to the cold winter air. To keep the legs as warm as the rest of the body, birds would have to pump a huge amount of heat-carrying blood to those exposed areas. Instead, birds allow the legs to cool, pumping a modest amount of blood into the extremities. In Herring Gulls, the upper part of the exposed leg may have a temperature of only 40 °F and the bottom of the foot is just barely above freezing!

Allowing the tissues of the lower leg to get so cold requires some fascinating modifications of the cells of those body tissues. Every living is covered with a membrane. This membrane is mostly made of molecules called phospholipids. Each phospholipid has two strings of carbon atoms, called fatty acids, pointing toward the center of the membrane. To function properly, the phospholipids of the membrane need to be able to move past each other. The membrane needs to be fluid enough to allow small molecules like oxygen to diffuse in and carbon dioxide to diffuse out. When a membrane is exposed to colder temperatures, the phospholipids pack in tightly. Oxygen cannot get into the cell; frostbite and often cell death occur.

Each carbon atom in the fatty acids of a phospholipid has four binding sites. Usually, two of the binding sites are used to bond to the two adjacent carbon atoms. The other two binding sites usually bind to a hydrogen atom. However, it is possible for two adjacent carbon atoms to each lose one of their hydrogen atoms and establish two bonds with each other. When these double bonds occur, they introduce a kink in the fatty acid.

You can see the effect of these types of bonds in your kitchen. Butter is made of fatty acids with no double bonds; it is a saturated fat. At room temperature, butter is a solid. Not the condition you would want for your membranes! Olive oil, liquid but viscous at room temperature, has one double bond in its fatty acids. In other words, it is a monounsaturated fat. Safflower oil is even thinner than olive oil because it has polyunsaturated fatty acids (two or more double bonds).

By adding double bonds to the fatty acids of the cell membranes in the leg, birds ensure that their membranes remain fluid in cold temperatures. The kinkiness caused by the double bonds keeps the fatty acids from packing too close. The membranes remain fluid.

Birds have a trick to keep their legs from losing too much heat. They arrange the arteries that bring blood to the leg and the veins that return blood to the heart as a counter-current system. You can see counter-current systems in many heating plants in large buildings. The furnace is situated at the center of the building. Cold air from outside is pumped into the furnace through a long pipe. The warmed exhaust air in the building is pumped out through a pipe parallel to the intake pipe. As the exhaust air moves toward the outside of the building, much of its heat is transferred to the colder intake air moving in the opposite direction. By the time the intake air reaches the furnace, the air has been warmed significantly by the exhaust air. Much of the heat of the exhaust air is recovered before the air is pumped outside. The counter-current arrangement of bird arteries and veins accomplishes the same energy savings.

Why do most birds not have feathered legs? The answer lies in the fact that a bird’s metabolism must be raised to provide the energy for flight. Excess heat is produced by this rise in metabolism and must be eliminated, even in the coldest weather, so a bird doesn‘t overheat. The unfeathered legs are the sites where that heat is lost.

[Originally published on March 3, 2007]

For the Birds – Adaptations to the Cold

Winter arrived with a vengeance over the past three weeks. From the warmth of our houses, many of us marvel at the ability of birds to survive the challenges of winter weather.

The body temperature of birds is normally between 104 and 109 °F; the fire of life (the rate of metabolism) burns hotter in birds than in any other animals. Birds must stoke their internal fires with more food than mammals of similar size whose body temperature may be only 100 °F or so. To say that someone “eats like a bird” really means that person is a ravenous glutton!

The rate at which heat is lost from a bird’s body in the winter depends on the difference in temperature between the bird’s body and the environment; a bird will lose more heat on very cold days than on mild days. Small birds have more of a disadvantage than larger birds. A bird loses heat based on its total surface area, the portion of the body that is in contact with the cold air or water. The heat produced by a bird is proportional to its total volume; every cell in the bird’s body is capable of producing heat. A result of simple geometry is that the ratio of the surface area to volume decreases as an object gets bigger. This geometric rule is cruel for small birds like Golden-crowned Kinglets because they have a relatively large surface area over which heat is lost and only a modest body volume to produce heat. A kinglet is living more on the edge than a jay or crow because of its large surface/volume ratio.

Birds can maintain their body temperatures in the face of severe cold in three basic ways. First, they can try to reduce the loss of heat. The plumage of birds in the winter is often twice as heavy as the weight of the summer feathers. In addition, the feathers of birds can be raised to create improved insulation. The erected feathers trap pockets of air. The insulating quality is improved by lowering the density of a material (light wool is a better insulator than dense metal, for instance). I am sure you have seen Mourning Doves and other birds at your feeder that are puffed up greatly to increase the insulating properties of their feathers.

At night, bird tend to roost in trees, often coniferous ones, close to the trunk. This choice of a bedroom has two benefits. First, the bird is protected from wind chill. Wind blowing across an animal’s body causes heat to be lost far more rapidly than when the air is still.

Second, trees absorb sunlight during the day and heat up. At night, they emit heat in the form of infrared radiation. Humans, houses and any other object emits infrared radiation. We cannot see this radiation but can sense it as heat. By staying close to the trunk, the birds absorb some of the infrared radiation the tree radiates and therefore gain some heat. You have probably seen rings around the bases of trees where the snow has melted, even though the air temperature has remained below freezing. This melting is caused by the snow absorbing the infrared radiation from the trees and heating to the melting point.

A second method of maintaining body temperature is to raise the heat of the internal furnace. When the air temperature falls below a certain critical level, a bird loses heat faster than it can be produced, even though it has puffed up its feathers to the greatest extent. Below this critical temperature, a bird must increase its metabolic rate to counteract the rapid loss of heat to the environment. Just as you do when you get very cold, a bird generates additional heat by shivering. It is not unusual for small birds like chickadees and goldfinches to spend the entire night shivering! The shivering requires additional energy which means that a bird must be even more gluttonous in the winter. No wonder birds flock to our feeders in the winter.

The last method of combating the cold is to simply allow the body temperature to fall. On cold nights, the body temperature of Black-capped Chickadees may allow its body temperature to fall by 10-18 °F. This decrease in body temperature lowers the difference between the bird’s temperature and the temperature of the cold environment, cutting down on heat loss. The bird is able to spend less energy keeping its internal furnace going. When the morning comes, the bird must raise its body temperature either by shivering or by warming in the sunlight.

[Originally published on February 17, 2007]

For the Birds: Maine Christmas Bird Count Highlights III

This column is the last of three on the results of the National Audubon Society Christmas Bird Counts (CBC’s, for short) conducted throughout the state of Maine. Each count could be conducted on any day between December 15 and January 5.

Let’s start with the three counts that experience the coldest winter weather of all the CBC’s in Maine. The Rangeley Count, held on December 17, produced a total of 34 species. Because of the unseasonably warm weather in November and December, ice had not formed over most bodies of water. The open water held six Common Loons and 59 Mallards.

Areas like Rangeley provide great habitat for boreal bird species. Those species did not disappoint this year as nine Boreal Chickadees were found along with 235 Black-capped Chickadees. Twenty-six Gray Jays made for an impressive total. Red-breasted Nuthatches tend to occur in coniferous forest while White-breasted Nuthatches are more often associated with deciduous or mixed forest. The conifers of the Rangeley area yielded 78 Red-breasted Nuthatches but only 3 White-breasteds.

The cone crops this year, particularly for red spruce, are heavy. Winter finches, which wander broadly in the winter abundant cones, put in a modest appearance with 65 White-winged Crossbills, 80 Pine Siskins and 87 Purple Finches.

Eight Northern Cardinals were counted, signifying the expanding range of this species into higher elevations in Maine. Seventeen American Robins were present.

The Misery CBC, centered in the town of Forks, was held on December 29. A total of 25 species was found. As at Rangeley, Northern Cardinals were found on the Misery CBC this year. Boreal species included five Gray Jays, 11 Boreal Chickadees, 48 Purple Finches, 17 Red Crossbills, 55 White-winged Crossbills and 70 Pine Siskins.

The Presque Isle CBC, held on December 30, produced at least 32 species (I don’t have the final totals yet). The highlight was an Eastern Towhee, the first ever recorded for this count. Towhees are quite rare in the northern half of the state at any time of the year. Two Black-backed Woodpeckers were nice finds. No doubt owing to the warm early winter weather, new high counts of Common Goldeneyes and Golden-crowned Kinglets were set.

It’s always interesting to compare the Orono-Old Town (December 16) and the Bangor CBC (December 30) because of their nearly overlapping locations. Counters on the Orono-Old Town CBC found 49 species. Notable birds included a Rough-legged Hawk, a Merlin, an Iceland Gull, two Northern Shrikes, four Bohemian Waxwings (very rare in the state so far this winter), three Red Crossbills, 20 White-winged Crossbills and 34 Pine Siskins. The 48 Tufted Titmice indicate that this species is continuing to expand its range northward in Maine. Lingering birds included a Belted Kingfisher, a Northern Flicker and 13 American Robins. A Carolina Wren was a nice find. The Bangor CBC yielded 50 species, with an interesting mix of birds of northern and southern affinity. Highlights were singleton Bonaparte’s and Iceland gulls, a Red-bellied Woodpecker, a Carolina Wren, a Northern Mockingbird, a new count record 101 Northern Cardinals, 10 Red Crossbills and 11 Common Redpolls. Seventy-one Tufted Titmice were impressive.

We’ll end with some more coastal CBC’s. The Machias Bay CBC, held on January 3, produced a list of 54 species. Thirteen species of waterfowl were found with a single Barrow’s Goldeneye being the most notable. Lingering birds included a Great Blue Heron, a Northern Flicker and 112 American Robins. Gray Jays occur predictably in the coastal spruce-fir forests of Maine from Mt. Desert Island eastward. Two Grays Jays were delightful but not unexpected. One Northern Cardinal was a noteworthy sighting. The only northern finch was a single Red Crossbill.

The North Penobscot Bay CBC held on December 30 had a total of 59 species. This portion of the coast is one of the most reliable in the state for Ruddy Ducks in the winter and the 107 tallied this year did not disappoint. The four Barrow’s Goldeneyes were expected but fewer than expected. A nice list of lingering birds included a Carolina Wren, five American Robins, five Northern Mockingbirds, two Swamp Sparrows and a Brown-headed Cowbird. A Yellow-breasted Chat was an extraordinary find. Six Red Crossbills were notable as well.
The Biddeford-Kennebunkport CBC held on December 30 yielded 93 species. Waterfowl diversity was extraordinary with 18 species found, including a Snow Goose, 13 Brant, two Gadwall and two Ruddy Ducks. Eight species of diurnal raptors included Merlin and Peregrine Falcon. A Dovekie was a highlight. Other noteworthy finds were singletons of the following species: Yellow-breasted Chat, Dickcissel and White-crowned Sparrow.

[Originally published on February 3, 2007]