Monarch Butterfly Migration

By in Butterflies

In today’s column, the Monarch Butterfly will serve as an honorary bird. Certainly one of the most easily recognized butterflies, Monarchs occur broadly across the United States and southern Canada.

However, the chances are pretty good that you have seen very few Monarchs this year in Maine. The cool and wet weather may have been a contributing factor to their poor success this year. I recently surveyed volunteers in the Maine Butterfly Survey project. Not one of the 25 respondents reported seeing as many as ten Monarchs this year, although the season may be a bit delayed.

Other species of butterflies like Common Ringlets, Common Wood Nymphs and Silvery Blues that live their entire lives in Maine took a big hit this summer because of our inhospitable June and July weather. These species will likely take a few years to recover their former population sizes.

The Monarch, however, is a migrant. Poor reproduction in Maine will not necessarily translate into lower numbers of Monarchs next year.

The amazing southward migration of Monarchs has been appreciated for quite a while. We have long known that populations west of the Rocky Mountains moved south to winter in about 150 winter roost sites between San Francisco south to northern Baja California. These roost sites are usually within a couple of miles of the Pacific Ocean. Each site usually has between 10,000 and 40,000 butterflies. As you can well imagine, coastal development has threatened a number of these roost sites.

But, where do the eastern migrating Monarchs spend the winter? The answer was not known until 1975 when a researcher named Fred Urquhart announced a surprising discovery. Each fall all of the eastern Monarchs in Canada and the United States empty out, migrating to Oyamel fir forests in the mountains of central Mexico. The fall migration commences in August and continues into December. Urquhart amazed everyone with pictures of millions of Monarchs roosting in layers on trees, weighting down branches.

Ten overwintering sites are known in Mexico. All are within an area of about 500 square miles in a belt of volcanic mountains stretching across Mexico. Conservation biologists are working hard to preserve these habitats and ecotourism is flourishing at these sites. Nevertheless, logging pressure poses a major threat.

As winter gives way to spring, the Monarchs become more active and start to mate. After mating, northward migration begins. Once mated, the butterflies have only a month or so to live. Along the northward migration, the females lay eggs on milkweeds along the way. Milkweed leaves provide the nutrition for the caterpillars. The migrating butterflies continue north and east with some reaching the Gulf coast states before they die. Meanwhile, the eggs laid along the way have hatched and the gluttonous caterpillars grow rapidly. Nine to 14 days after hatching, the caterpillar enters the pupal or chrysalis stage. During the next eight to 11 days, the tissues of the caterpillar are transformed into the body of an adult butterfly.

These newly emerged Monarchs (the offspring of the overwintering generation) continue northward, laying eggs along the way and ultimately perishing. Each female can lay 500 eggs. Most are laid singly on a milkweed plant. In this leapfrog manner, all of the eastern United States and southern Canada are repopulated. The Monarchs that reach us may be the great-grandchildren of the overwintering population!

The Monarchs that will migrate back to central Mexico emerge in the fall. These butterflies do not become reproductive but rather go into reproductive diapause. They will not be able to mate until the following spring on the wintering grounds in Mexico. Unlike the other adults from other generations that have only a month or so to live, these overwintering Monarchs may live for seven months.

Perhaps the most remarkable aspect of this tale is the “hard-wiring” in the migrating Monarchs. Even though they have never made the journey to central Mexico, the migratory behavior and direction are genetically encoded.

Since 1990, Dick Walton and Lincoln Brower have been conducting a Monarch Monitoring Survey at Cape May, New Jersey. At times, more than 300 Monarchs per hour have streamed past the hawk watch platform at Cape May Point. You can see find year-by-year accounts of the Monarch migration there at: http://www.concord.org/~dick/mon.html Numbers for 2009 indicate average to above average counts, lightening the dismal season for Monarchs in northern New England.

I encourage anyone wishing to learn more about these remarkable butterflies to read Sue Halpern’s marvelous book, Four Wings and a Prayer. Her prose is lyrical and her accounts of field expeditions with established Monarch researchers are fascinating.

[First published October 3, 2009]

Birds and Window Collisions

By in Bird Conservation

Human-related activities account for a significant number of bird deaths. Habitat destruction is clearly the most important but the next most important factor is collisions with clear and reflective sheet glass. Such collisions account for at least a billion bird deaths each year in the United States. These deaths are spread over at least 225 species. Compare this mortality with deaths from other human-related factors: 120 million from hunting, 60 million from collisions with moving vehicles, 400,000 from wind turbines and potentially hundreds of millions by cats.

Dan Klem, a professor of biology at Muhlenberg College, has been studying bird kills from glass collisions for the past 35 years. Much of today’s column comes from Klem’s extensive research.

Why do so many birds die from flying into windows? There is little evidence to indicate that birds that hit windows have faulty eyesight. Reduced vision in fog and smoke also plays only a minor role in explaining window kills. The chief explanation seems to be that birds perceive clear windows as open space and attempt to fly through. The likelihood of window kills is increased if there are windows on both sides of a building, producing a see-through effect. Windows with reflective surfaces act as mirrors, fooling birds into thinking that flight is possible through the window.

Bird feeding increases window kills by attracting birds to buildings. The high concentrations of birds at feeders, particularly in the winter, attract bird predators like Sharp-shinned Hawks or Cooper’s Hawks. The appearance of such a predator, loud noises or sudden movements, may cause a panic flight of birds from a feeder with the possibility of fatal window strikes. A short flight of only one meter can produce a fatal collision.

Klem examined 300 fatalities and 31 survivors to determine the types of injury, causes of death, and recovery from collisions. Every fatality showed intracranial bleeding, suggesting that death was caused by ruptured blood vessels in the head and brain damage. Survivors often sustained intracranial bleeding as well and may have died later on from the injury. Bone fractures were relatively rare, indicating the surprising strength of the light bones of birds.

If you find a stunned bird after a window collision, place the bird in a protected enclosure (I use a paper bag), keep the enclosure warm, and provide the bird with food and water.

What can homeowners do to minimize window strikes by birds? The best solution, to eliminate windows altogether, is not acceptable. Covering windows with netting can be expensive and affects the aesthetics of a building. Making windows obvious as obstacles that should be avoided can reduce window kills. Spiders use this strategy to protect their webs. The webs of many spiders have thick, highly visible strands. Flying birds easily see these strands and avoid flying through the webs. Klem’s research has shown that placing vertical strips of tape on windows cuts down on window strikes dramatically, particularly if the strips are separated by four inches or less. Horizontal strips are less effective. The black silhouettes of hawks and falcons that can be purchased for placement on windows are not effective unless they are stacked closely together. These silhouettes do not provide enough contrast for birds to realize that windows are obstacles. In new or remodeled homes, architects are encouraged to install windows at a slight angle so that they reflect the ground rather than trees or the sky. Birds are not likely to try to fly into a reflection of the ground. In addition, birds are likely to hit an angled window at an angle and thus soften the force from the collision with the glass.

The placement of bird feeders can also curtail window kills. Klem’s studies have shown that placing feeders very close to a window reduces fatal window strikes during panic flights. Although birds may hit the window after they fly up in response to a loud noise or a predator, the birds will not be flying fast enough to suffer harm or death from the collision. An alternative solution is to place your feeders well away from the nearest window. So, the best advice is to either place your feeders within three feet of a window or at least 30 feet away from the window.

One of Klem’s recent publications involved the assistance of 30 trained volunteers from the New York City Audubon Society. The purpose of the study was to determine building and landscape characteristics associated with higher risk of collisions with migrating birds in an urban environment. The research was done in Manhattan. The volunteers monitored 73 facades of buildings throughout the island borough.

The team recorded 475 bird collisions in the fall of 2006 and 74 collisions were in the spring of 2007. Their analyses provide good advice for architectural and landscape designs to reduce collisions: reducing the number of reflective panes in windows, keeping trees away from walls, and reducing ground cover.

[First published September 19, 2009]

Birder Demography and AOU Check-list Updates

By in Birding and Birders

Who Are We?

The U. S. Fish and Wildlife Service has recently released their report, “Birding in the United States: A Demographic and Economic Analysis”. This document offers interesting insight into the popularity and demographics of birding.

Birder is defined rather broadly for the purposes of this report. A birder is someone who has driven at least a mile for the primary purpose of watching birds or someone who closely watches and tries to identify birds around the home. People who happen to see birds while mowing the lawn or kayaking do not qualify as birders.

The report indicates that 48 million of us, 16 years of age or older, are birders. That number translates to 21% of the North American adult population. Backyard birders include 42 million birders. Twenty million birders travel to see birds.

The average birder is 50 years old. Only 8% of citizens between 16 and 24 years of age and only 13% of citizens between 25 and 34 years old are birders. For citizens above 55, birding is more popular with 27% of this age group participating.

The data show a clear pattern of birding participation rate increasing with income level. Birding interest increases with education as well. Only 12% of citizens without a high school degree are birders while 28% of college graduates are birders. Female birders outnumber male birders, 54% to 46%.

Birding is primarily an activity of white people. Over 24% of white citizens classified themselves as birders, contrasting with 8% for Hispanics, 6% for African-Americans and 7% for Asians.

One might expect that people who live outside of major urban areas would be more likely to be birders. That expectation is borne out by the survey. Only 17% of citizens in major urban areas are birders compared to 27% of Americans who live in townships under a population size of 250,000.

The popularity of birding varies greatly among the 50 states. I am pleased to report that Maine with a 39% participation rate is second only to Montana with a 40% participation rate. Other high-ranking states are Vermont (38%), Minnesota (33%), Iowa (33%), South Dakota (32%) and New Hampshire (32%). Birding is least popular in Hawaii (10% participation rate). Four of our most bird-rich states (Florida, Arizona, California and Texas) are near the bottom of the list with participation rates of 17% or lower. Lots of out-of-state birders do visit these states.



Changes to North America bird names

The American Ornithologists Union (AOU) publishes the official Check-list of North American Birds. North America is defined broadly as all countries from Panama north. The Caribbean Islands, Bermuda and the Hawaiian Islands are included as well.

The most recent Check-list, the seventh edition, was published in 1998. Scientific and common names are given for each species along with a brief habitat description and a textual description of the geographic distribution.

The AOU has a Check-list Committee that is responsible for updating the Check-list. Bird distributions change. Ornithological research, especially the analyses of DNA, forces ornithologist to reassess the classification of birds at the genus, family and order level.

The most recent supplement to the Check-list was just published in the Auk, the journal of the AOU. Most of the changes pertain to Central American species. However, some changes are made to birds that occur in Maine. I will restrict my discussion of the changes to those birds. You may wish to update your field guide.

The scientific name of the Boreal Chickadee is changed from Poecile hudsonica to Poecile hudsonicus.

Recent DNA analyses have shown that some of the birds formerly classified as tanagers (family Thraupidae) are actually closer to the cardinals and their relatives (family Cardinalidae). The tanagers that occur in Maine are in this group. So now, Scarlet Tanager, Summer Tanager and Western Tanager should be reclassified into the cardinal family. The committee stopped short of changing the common names. Now we are left with the confusing situation that a Scarlet Tanager is not really a tanager.

In an earlier decision, the Check-list Committee split the old Sharp-tailed Sparrow into two species, the Saltmarsh Sharp-tailed Sparrow and Nelson’s Sharp-tailed Sparrow. Both nest in Maine. That decision is supported by subsequent research but the common names are a mouthful. The committee has changed the names to Saltmarsh Sparrow and Nelson’s Sparrow, respectively.

Lastly, the genus Carduelis contained a number of the small finches. That genus is now split into several genera. For Maine species, change Common Redpoll to Acanthis flammea, Hoary Redpoll to Acanthis hornemanni, Pine Siskin to Spinus pinus and American Goldfinch to Spinus tristis.

[First published September 9, 2009]

Etymology of Some Bird Names

By in Birding and Birders

Blackburnian Warbler, Wilson’s Storm-Petrel, Swainson’s Thrush, Lincoln’s Sparrow. The common names of all of these birds, common in Maine, are based on a person’s name. I’ll bet most of these people aren’t familiar to you. In today’s column, I will give you a little background on the people whose names are commemorated in the bird names.

The Blackburnian Warbler is one of our most striking warblers with its fiery orange throat and bold black plumage above. This warbler is named after either Anna Blackburne (1726-1793) or her brother, Ashton Blackburne (1730-1780). Anna was an English naturalist. She never visited the New World but did have a strong interest in the birds of the New World. She maintained a collection of North American birds in her natural history museum in Orford in the north of England. Ashton moved to North America and lived in Hempstead, New York. He collected birds in Connecticut, New York and New Jersey that he sent to his sister for her museum. Among the specimens Ashton collected was a Blackburnian Warbler. Thomas Pennant, a naturalist from Orford, saw the specimen in Anne’s collection and prepared the first scientific description of the species. He gave it the name of Blackburnian Warbler but it is not clear if Pennant named the warbler for Ashton or Anne.

The Wilson whose name is commemorated in Wilson’s Storm-Petrel, Wilson’s Plover, Wilson’s Phalarope, Wilson’s Warbler and Wilson’s Snipe is Alexander Wilson (1766-1813). Wilson played an important role in the development of North American ornithology.

Wilson was a Scot who immigrated to the United States in 1794. He taught school for seven years in the Philadelphia area and then decided to make a collection of the birds of eastern North America. From 1803 until his death in 1814, Wilson devoted himself to producing the first book on the birds of North America, which he called American Ornithology.

Wilson’s travels took from Philadelphia along the eastern seaboard to Savannah, Georgia and then north via boat to New York. Another trip took him from Philadelphia to the southeast through Ohio, Kentucky, Tennessee, Mississippi and Louisiana with another boat trip back to New York from New Orleans. His visit to Natchez provided one of the ornithological highlights of his life, the darkening of the skies for hours by millions and millions of Passenger Pigeons.

Wilson was a contemporary of Audubon and they met briefly. Wilson’s artistic skills were rudimentary compared to Audubon but Wilson’s keen eye and perseverance made him a better field ornithologist than Audubon. In addition to the bird species listed above, Wilson’s name is commemorated in the name of one of the major ornithological associations in North America, the Wilson Ornithological Society.

Swainson’s Thrush was named after the Englishman, William Swainson (1789-1855). He had an early interest in nature. His father secured a post for him in Italy in 1808, which gave him plenty of time to study animals, particularly fish and snails. Poor health forced him from the army in 1815 but by 1816, he felt well enough to travel to Brazil for a collecting expedition. He returned to England with 760 bird specimens and large numbers of other species.

Swainson developed skills as a wildlife artist, drawing the biological material he had collected. In fact, he was a far more prolific wildlife artist than Audubon. Based on specimens collected by William Bullock in northern Mexico, Swainson drew and described a number of birds common in the United States including Acorn Woodpecker, Black Phoebe, Violet-green Swallow and Western Bluebird.

Audubon visited Swainson and his family on a trip to England. Audubon asked Swainson to help write the Ornithological Biography, the text that would accompany Audubon’s volumes of prints, The Birds of North America. Swainson refused because Audubon would not give him co-authorship nor a sufficient fee.

Swainson’s name is commemorated in three species: the widespread western raptor, Swainson’s Hawk; the southeastern Swainson ‘s Warbler and our Swainson’s Thrush.

Lincoln’s Sparrow is a fairly common breeder in bogs and cleacuts in the northern half of Maine. The name commemorates a Mainer, Thomas Lincoln (1812-1883). Lincoln met John James Audubon in 1832 and accompanied Audubon on an expedition to Labrador in 1833. Their trip began in Eastport and included stops in Nova Scotia and Newfoundland. The only new species discovered on this expedition was a sparrow, which Audubon described and named after his companion.

After the trip was over, Lincoln returned to the family estate in Dennysville and never did much traveling after that. He studied briefly at Bowdoin College but left before receiving a degree. He and his brother managed the 10,000 acres of the family property. The Lincoln house still stands. It is now the Lincoln House Country Inn, the oldest house in Dennysville.

[First published August 8, 2009]

The Fall Migration of Semipalmated Sandpipers

By in Migration

Shorebird migration is well underway now. Most of these migrants we are seeing in Maine belong to species that nest on the arctic tundra. These birds only have time to produce one clutch of young in the brief arctic summer. The birds depart their breeding grounds as soon as possible after nesting. Interestingly, the adults leave before their young can even fly. Obviously, the migratory routes must be hard-wired in the brains of the young birds.

One of these species is a favorite of mine, the Semipalmated Sandpiper. I have written in a previous column about the arduous fall migration of these birds. Most Semipalmated Sandpipers wend their way to the upper Bay of Fundy in July and August. The birds fatten for a couple of weeks and then depart on a southeasterly track en route to Suriname and adjoining South American countries. This flight must be conducted non-stop over the ocean and requires between 48 and 96 hours of sustained flight. The trade winds do provide significant help for the birds once they go south of the 30th parallel of latitude.

In today’s column, I want to discuss some research that I did in Nova Scotia over the course of two summers. In particular, I will describe the intriguing relationship between the Semipalmated Sandpipers and their major prey in the upper Bay of Fundy mudflats.

The prey species is a small, shrimp-like crustacean called Corophium volutator. Reaching a length of 3/8 of an inch (10 millimeters), Corophium live in U-shaped burrows in the intertidal flats of the upper Bay of Fundy. During the summer, the densities of these crustaceans may exceed 100,000 per square meter.

Corophium have two generations each year. One generation is born in May and grows to reproductive size by the middle of July. These adults reproduce in July and August. Their offspring will grow during the fall and reproduce the following spring in May.

The females brood their eggs in a special brood pouch and ultimately release juveniles that make their own burrows as soon as they are released. The young are only about 1 mm long when they leave mom’s brood pouch to strike out on their own. Once reproduction has occurred, adults will live for a few weeks longer at the most.

The annual population cycle of Corophium therefore involves two generations that scarcely overlap: a three-month summer generation and a nine-month overwintering generation.

Migrating Semipalmated Sandpipers rely almost exclusively on Corophium while they are in the upper Bay of Fundy. The sandpipers are adept at detecting the Corophium in the sediment with their sensitive bills and extracting them. A successful peck by a Semipalmated Sandpiper is easily determined because the Corophium struggles in the bill of the sandpiper. By analyzing videotapes of feeding sandpipers, I was able to quantify the number of Corophium that a sandpiper takes per minute.

I did my research on the mudflat at Avonport in the Minas Basin of the Bay of Fundy. The tidal range there is huge: 35 to 50 feet between high and low tide depending on the stage of the moon. At low tide, a tremendous area of intertidal mud is exposed, giving the Semipalmated Sandpipers access to lots of Corophium.

Around 40,000 Semipalmated Sandpipers foraged on the Avonport flats. I found that each sandpiper ate an average of 17 Corophium per minute! The birds feed both during the day and night when the tide is out. Each sandpiper eats well over 10,000 Corophium per day. That is how the sandpipers can double their weight in just two weeks as they store the necessary fat to fuel their migration to South America.

We also know that Semipalmated Sandpipers choose the large Corophium to consume. As it turns out, I was able to show that Semipalmated Sandpipers are effectively managing their prey population.

When the Semipalmated Sandpipers arrive in July and August, the Corophium born in May are fully grown and are reproducing. Those are the prey the sandpipers go after. Because the adults live for a few weeks after reproducing, they compete with their offspring for food and space in the mudflat. By removing the large Corophium, the sandpipers improve the survivorship of the newly born Corophium. The large Corophium have mostly finished reproducing so their removal by the sandpipers does not affect the population to a great degree.

So, by preying on the large Corophium, the sandpipers increase the number of Corophium that will overwinter. Those Corophium will produce the summer generation in May that will provide food for the gluttonous sandpipers the following July and August.

[First published August 22, 2009]

Precocial versus Altricial Development

By in Reproduction

The development of birds can be classified into one of two main types: precocial and altricial. Precocial birds, like chickens, ducks and owls, hatch out with a warm covering of down feathers. A precocial chick can keep its body reasonably warm in the absence of heat from an incubating parent. Some precocial chicks can feed themselves soon after hatching. A Lesser Scaup duckling can swim, dive and catch fish only three days after hatching. Others, like gulls and terns, depend on their parents for food.

Precocial chicks are quite mobile on the ground or in the water soon after hatching. However, it takes a good bit of time, often a couple of months, before they are able to fly. Parents of precocial chicks must spend a fair amount of time watching out for predators looking to make a flightless chick into a meal.

After a period of time, a precocial chick learns to fly. The act of taking the first flight is called fledging. The amount of care given to precocial chicks before and after fledging varies. Sandpipers, like the Semipalmated Sandpiper, leave their flightless young on the arctic tundra and begin their migration southward. The young, with the abundant supply of insects on the tundra in the summer, can fend for themselves. Ultimately, the sandpiper chicks fledge and, guided by a remarkable navigational sense, follow on the heels of the parents two or three week later. Canada Geese tend their young throughout the nestling and fledging periods. The families migrate south together.

Altricial development, the other major developmental type in birds, is characteristic of all songbirds, woodpeckers, swifts, kingfishers, pigeons and hummingbirds. The young hatch as helpless, naked birds. Their eyes are not open and they are unable to even hold their heads up. The young hatchlings cannot maintain their body temperature by themselves for even a short period of time. As a result, one of the parents must incubate the young to keep them warm. This incubation, usually done by the mother, is made possible by the presence of a brood patch on the underside of the body. This brood patch has no feathers and has a rich supply of blood vessels to allow the quick transfer of heat from the parent to the young.

The young must be fed by the adults and rapidly begin to add weight and feathers. The incubation period in most songbirds lasts between eleven and fourteen days. The mother has to spend less and less time incubating the young as they grow as their feathers develop. By the time the nestling period is ending, the chicks have voracious appetites that often tax the abilities of the parents to provide food.

After the nestling period, the young are ready to fledge. The work of the parents is not over although the nest is abandoned once the young fledge. The fledglings follow their parents around are still fed by the parents. You can see the begging behavior of recently fledged young at your feeder. After a period of two or three weeks, the fledglings have become proficient fliers and good foragers so the family unit breaks down. The fledglings are now on their own.

So which is better, precocial or altricial development? Precocial development has the advantage of reducing the time spent in incubating the nestlings as the chicks are born with a covering of down. Precocial chicks can find much of their own food, freeing the parents from an additional energy drain. However, the time to fledging takes a long time. From hatching to fledging for a Ruffed Grouse takes over two months. Hawks and owl chicks may take three months or more to fledge. That’s a long time to avoid predators without the benefit of flying.

Altricial development presents a tremendous challenge for the parents. After hatching, the young have to be fed and incubated. However, the development is quite rapid. After hatching, the young can be fledged and independent in less than a month. In fact, some of our songbirds like House Wrens and Eastern Bluebirds will even have two broods of young in a single season.

The tradeoff then is for parents to work really hard for a relatively short period of time (altricial development) or invest less energy in tending the young on a daily basis but have young which are at risk from predators for a long time because they take so long to fledge (precocial development).

[First published July 25, 2009]

Review of Ghost Bird

By in Movie Reviews

Today’s column is a review of a movie that is premiering now in the United States as part of the Maine International Film Festival in Waterville. The movie is called Ghost Bird and details the controversy over the recent claims that the Ivory-billed Woodpecker still lives. The film was produced and directed by Scott Crocker, a Bowdoin College graduate.

April 28, 2005 was a great day for birders. The Cornell Laboratory of Ornithology held a press conference to announce the finding of an Ivory-billed Woodpecker in eastern Arkansas. Prior to this sighting, this largest of North American woodpeckers was last documented by photograph in 1941.

Over the years, Sightings of Ivory-billed Woodpeckers, some more credible than others, were reported regularly from Louisiana, Florida and more recently Arkansas. None of these observers managed to get a photograph or movie of the birds.

The chance of confusing a Pileated Woodpecker for an Ivory-billed Woodpecker is high, particularly if the sighting is brief. Nevertheless, a spate of sightings from the Cache River in eastern Arkansas was convincing enough for the Cornell Laboratory of Ornithology to mount a large expedition there in the fall of 2004.

Their best evidence for an Ivory-billed Woodpecker was a brief videotape, taken by David Luneau, a professor electronics at the University of Arkansas-Little Rock. Luneau kept his videocamera recording on the gunwale of his canoe and by luck captured a brief flight of a large woodpecker.

The Cornell team also had a series of automated recording devices throughout the Cache River swamp. Recordings were captured of the “kent” calls that Ivory-bills give as well as the double-tap knocks the birds use to communicate.

The elation of a number of ornithologists and birders flagged upon examination of the data. I think the words of Carl Sagan, the eminent astronomer and stalwart of the skeptic movement in the United States, are appropriate in this case: “Extraordinary claims require extraordinary evidence.”

A close examination of the Luneau video convinced some ornithologists that the bird was actually a Pileated Woodpecker rather than an Ivory-bill. The acoustic evidence was questioned because Blue Jays give a “kent” call, even in areas where Ivory-billed Woodpeckers never occurred. Pileated Woodpeckers will give double tap signals.

Ghost Bird explores the impact of the claimed Ivory-billed sightings on the town of Brinkley, Arkansas. According to one citizen, only one person in Brinkley even knew what an Ivory-billed Woodpecker was before the 2005 announcement. At least six businesses have sprung up in Brinkley, all capitalizing on the Ivory-billed Woodpecker. Where else can you get a woodpecker haircut for $25?

Crocker reviews the data used to support the claim of living Ivory-billed Woodpeckers, including multiple showings of the Luneau video. We see lots of footage of the Cache River swamps.

Two skeptical scientists are extensively interviewed. Dr. Jerry Jackson of the Florida Gulf Coast University is the eminent living authority on Ivory-billed Woodpeckers and has conducted searches for these birds. Dr. Rick Prum of Yale University provides his perspective as well.

David Sibley, the author of the best-selling field guide on North American birds, went to Arkansas after the initial announcement. He noted that earlier workers found that Ivory-billed Woodpeckers preferred to forage on Nuttall oaks. In eight days of dawn to dusk field work, Sibley found no evidence of woodpecker excavations or bark stripping on these oaks.

Crocker does a nice job of documenting the history of the decline of the Ivory-billed Woodpecker. Jim Tanner studied Ivory-billed Woodpeckers in the Singer Tract of Louisiana between 1937 and 1941 for his doctoral research at Cornell University. He and his wife Nancy saw and photographed Ivory-bills there for the last time in 1941. Nancy Tanner is still living, and, in the film, offered a fascinating glimpse into history.

The Cornell Laboratory of Ornithology continues to maintain that their evidence is sufficient to demonstrate that the Ivory-billed Woodpecker still survives. Unfortunately, the Lab would not allow any of their employees to be interviewed for this documentary.

The initial excitement over the re-discovery of the Ivory-billed Woodpecker led to changes in funding for conservation. The U. S. Fish and Wildlife Service provided an initial $10 million dollars to help conserve the Ivory-bill. These funds had to be provided by taking money from other projects designated for the protection of other endangered species. An additional $27 million was provided in 2007. A number of conservation biologists have questioned this re-allocation of limited funds.

[Originally published on July 7, 2009]

By in Uncategorized

For the Birds – Ruby-throated Hummingbird

The Ruby-throated Hummingbird has to be one of most eagerly anticipated birds among our migratory breeding birds. The acrobatic flight of hummingbirds, their iridescent colors and their small size endear hummingbirds to many people.

The hummingbird family is one of the largest of the birds with 328 recognized species. Hummingbirds are birds of the New World with the majority found in the tropics of Central and South America. In North America, only about 20 species occur regularly and only one, the Ruby-throated Hummingbird, breeds in eastern North America.

The Ruby-throated Hummingbird is one of the smaller hummingbirds. A typical one weighs a little more than 3 grams, about the weight of a penny. The smallest hummingbirds are the Bee Hummingbird from Cuba and the Reddish Hermit from Brazil and Guyana, which weigh only 2 grams. On the larger side, the South America sicklebills and the Sword-billed Hummingbird weigh 12-14 grams, a little more than a chickadee. The Sword-billed Hummingbird has the longest bill of any hummingbird at an astonishing five inches! The largest of all hummingbirds is the appropriately named Giant Hummingbird, which tops the scales at 21 g.

Ruby-throated Hummingbirds spend the winter between southern Mexico and western Panama. In migration, some individuals undertake a non-stop migration of 1000 miles across the Gulf of Mexico. The birds have to put on extra fat to fuel this expensive flight. Feeding on nectar and insects, a Ruby-throated Hummingbird will double its weight before it departs across the Gulf of Mexico.

Recent observations indicate that some Ruby-throated Hummingbirds prefer to migrate along the eastern coast of Mexico to reach the United States, a longer but perhaps less demanding migration.

To increase our understanding of Ruby-throated Hummingbird migration, an international volunteer project has begun called Operation RubyThroat. The project is designed primarily for K-12 teachers and their students in the countries of Central America and North America. You can find information on Operation RubyThroat at their web site: http://www.rubythroat.org/

Once in the United States, Ruby-throated Hummingbirds disperse widely. The breeding range extends from eastern Texas along the Gulf Coast to Florida and north in the east to Nova Scotia, New Brunswick and Labrador and west to Minnesota, then spreading westward in the Canadian prairie provinces, stopping just shy of British Columbia. Their breeding range is the largest of any hummingbird breeding in North America.

Hummingbirds are specialized to feed on nectar. A number of plants and hummingbirds have evolved mutualistic relationships. These plants produce sugar-rich nectar, which attracts hummingbirds. As the hummingbirds feed on the flower, pollen attaches to the hummingbird’s head and bill. When the hummingbird visits another flower, some of the pollen it is carried is transferred to the female part of the flower and fertilization is assured. Some plants therefore “pay” hummingbirds in nectar in return for pollination services.

One species that seems particularly adapted for pollination by Ruby-throated Hummingbirds is the trumpet creeper, a woodland vine. Studies have shown that Ruby-throated Hummingbirds deposited ten times as much pollen as other pollinators (bumblebees and honeybees).

Most long, tubular flowers are attractive to hummingbirds. Bee balm is particularly recommended. Of course, a hummingbird feeder is an easy way to attract hummingbirds as well. Choose a feeder with a wide mouth to make cleaning easy. You can buy so-called hummingbird food to dissolve in water. On the other hand, you can save some money and make your own. Just mix four parts of water to one part of table sugar and bring to a boil. When the sugar dissolves, cool and then fill your feeder. You can store the excess in your refrigerator for a couple of weeks.

Keep an eye on your feeder. Particularly in warmer weather, fungi grow in the feeder. You should wash your feeders regularly; easy to clean feeders will make this task a quick one.

Nest building in Ruby-throated Hummingbirds is done only by the female and takes between 6 and 9 days. The base of the nest is made of thistle and dandelion down. The base is saddled along a branch and is fastened with spider webs. The female stamps down the plant down to make a firm floor. White plant down and bud scales make up the side of the nest. The female uses a figure-8 motion to lace the plant material together. The outside of the nest is adorned with lichens, making a well-camouflaged nest.

Two eggs are laid and hatch 12-14 days later. The female does all the feeding of the young. The young are feed nectar at first with supplements of insects as they grow larger. The young fledge 18-20 days after hatching.

[Originally published on May 1, 2009]

By in Uncategorized

For the Birds – Earth Day

Wednesday is Earth Day. In today’s column, I will review a couple of major studies that have examined the impact of humans on bird populations. Both of these studies are based on citizen-science projects. Many of you will have contributed to the databases.

National Audubon scientists recently released the results of their study of the past 40 years of Audubon’s Christmas Bird Counts. The scientists analyzed the population changes of 305 bird species that occur widely in the winter in North America.

Of this total, 177 species have shifted their range northward. This northward shift is consistent with global warming. The average shift northward over the past 40 years is 35 miles for all 305 species, including those that do not show northward movements.

Of course, averages can mask more dramatic changes for some species. Boreal Chickadee, Purple Finch and Pine Siskin have retreated dramatically into Canada. The center of the ranges of these species has moved 211, 313 and 246 miles northward since 1968.

Species that rely on open water show pronounced shifts in their ranges as well. American Black Duck, Ring-necked Duck and Red-breasted Merganser show a northward shift of their ranges by 150 to 250 miles. These birds are able to winter further north because more open water is available in northern states and Canada.

Consider the increase in average number of the following species in Maine between 1968 and 2008: Mourning Dove (22.4 times increase), Red-bellied Woodpecker (5.5 times), Carolina Wren (5.0 times), Hermit Thrush (9.8 times) and White-throated Sparrow (2.8 times).

What’s the big deal you may ask? Don’t the birds just shift their ranges northward with no overall change in abundance?

Actually, this expansion of ranges toward the poles should give great concern. Consider a typical map of the world using a Mercator projection. On such a map, Greenland looks to be about the same size as Africa. In fact, Africa has 14 times the area of Greenland. A Mercator map distorts the area of land near the poles.

Instead, think about a globe of the earth with lines of longitude on it. Follow two adjacent lines of longitude from the equator to the North Pole, noting how the lines get closer and closer as you move from the equator.

By forcing birds northward, we are funneling them into smaller and smaller areas. Sooner or later, the birds will run out of habitat.

A second major report, The State of the Birds: United States of America, was recently published by a partnership of a dozen government and non-government organizations, including the Cornell Lab of Ornithology, the National Audubon Society and the U.S. Fish and Wildlife Service.

The report used three sources of data on bird population changes: the Christmas Bird Count, the Breeding Bird Survey and the Waterfowl Breeding Population and Habitat Survey.

The report is a balanced report, noting species that are declining and increasing. Environmental threats are thoroughly discussed and reasons for hope are covered as well. The report is mainly organized by general habitat, such as grasslands, arid lands, forests and wetlands.

Let’s consider forests as a representative habitat. The report tells us that North American forests harbor more than 300 species of breeding birds. Although some species are doing well, fully a third of these bird species are declining. The threats are familiar ones: unplanned, urban sprawl; unsustainable logging practices; intense wildfires caused by decades of fire suppression; impact of tree insects and tree diseases driven in part by climate change.

Examining eastern forests, the authors found that 25 species found exclusively in forests have declined in abundance by 25% in the past 40 years. Species of particular concern from eastern forests are Eastern Wood-Pewee, Wood Thrush, Blackpoll Warbler, Cape May Warbler, Pine Siskin, Evening Grosbeak and White-winged Crossbill.

To halt the declines, the authors suggest better planning of human development, green logging practices and doing all we can to slow the rate of carbon dioxide emissions to at least slow down the rate of global warming.

Space does not permit consideration of all the habitats covered in this thoughtful report. Copies are available for download at http://www.stateofthebirds.org/ I encourage you to read the document ; it will be well worth your time.

Finally, here are some suggestions for ways we can combat climate change. Visit http://www.birdsandclimate.org to sign the petition urging lawmakers to take steps to slow global warming. Determine your energy profile and carbon footprint. A number of carbon footprint calculators are available on-line. Become a locavore; buy locally grown produce and other food as often as you can. Plant more trees. Happy Earth Day!

[Originally published on April 18, 2009]

Bird Nests

By in Reproduction

A characteristic feature of all bird species is a nest in which eggs are laid. Nests range from small depressions in the forest floor to massive structures weighing more than a ton. In today’s column, I will provide an overview of the diversity of bird nests.

The simplest nests are scrapes on the forest floor, fields or beaches. The nest of aKilldeer is a good local example. The female lays four eggs in a nest scrape just big enough to contain the eggs. As you would expect, the eggs are well camouflaged. In the woods, American Woodcocks and Whip-poor-wills create nest scrapes for their eggs. For most species that create nest scrapes, little effort is made to line the nests with soft material. Birds that make nest scrapes spend very little energy in making a place to lay eggs and raise their young.

Most birds construct a bowl-shaped nest just large enough to fit an adult’s body. Let’s use an American Robin nest as a typical example of a bowl-shaped nest. Robins are not great architects but still have a remarkably complex nest. The outer part of the nest is formed of twigs, coarse grass and sometimes pieces of cloth, string or other human-made products. This outer layer gives the nest strength. Within this outer layer, robins place a smooth layer of mud. Finally, a layer of fine grasses is laid down to surround the eggs and aid in insulation. Once the outer part of the nest is built, the female sits in the middle of the nest for the rest of the construction. A snug fit is therefore guaranteed for the incubating mother. The nest is usually in a tree between three and 25 feet high.

Other species use specific materials for the inner lining of their nests. Palm Warblers, a ground-nesting species in bogs, often place Ruffed Grouse feathers in their nests. Tree Swallows line their nests with feathers, particularly white ones. Ruby-throated Hummingbirds create tiny nests to hold their two eggs. The nest is made of down and small pieces of plant material bound together with spider webs. The outer part of the bowl is covered with bits of lichens to aid camouflage. Black-capped Chickadees make their nests in a tree cavity. The outer part of the nest is made of moss and the inner part of spider webs, soft grasses and plant down.

Waterbirds typically create bowl-shaped nests on the margins of lakes or ponds or even on floating vegetation. In most cases, the outer layer of the nest is made primarily of vegetation. If water levels rise, waterbirds will quickly add additional vegetation to keep the inner part of the nest dry. The inner lining is made in part of down feathers that the female pulls from her breast. These down feathers create a wonderfully warm place for the eggs. You take advantage of the excellent insulating qualities of duck down if you own a down coat or sleeping bag.

The largest nests in Maine are made by birds of prey. An Osprey nest may be five feet across. The outer portion is made of sticks and miscellaneous debris. The inner lining is made of smaller twigs, grasses and other soft material. Both the male and female participate in nest building. The male tends to bring material to the nest site and the female incorporates the material into the nest.

The largest nests in Maine are made by Bald Eagles. Some nests may be eight feet in diameter and 12 feet high. The weight may exceed one ton! Like Ospreys, Bald Eagles use the same nests year after year, adding material to the nest each spring. Great Horned Owls will readily adopt an abandoned Osprey or eagle nest.

Some of our birds place domes over the tops of their nests. Such nests are characteristic of many of our wrens. The family name for the wrens, the Troglodytidae, comes from the Greek for cave dweller, reflecting the shape of the nest. One of our most common warblers, the Ovenbird, builds a domed nest on the forest floor. The shape of the nest suggests a Dutch oven. By the way, there is an unrelated group of tropical birds called ovenbirds that create clay-shaped, domed nests which look just like a brick oven.

Distinctive nests are made by Baltimore Orioles. Their nests are made of grasses, vines, and hair. The nest is a deep pouch, bound to the forks of a branch at the rim. Two sprites of the Maine woods, the Ruby-crowned Kinglet and Golden-crowned Kinglet also create hanging nests that are much smaller and more difficult to see than oriole nests.

[Originally published on June 27, 2009]

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