Bicknell’s Thrush – II; The Warbler App

By in Field Guides, Identification, Software, Species Accounts, Vocalizations

This column continues the discussion of Bicknell’s Thrush, one of the most elusive breeding birds in Maine. By the time you read this column, most male Bicknell’s Thrushes will be done singing for the breeding season.

Bicknell’s Thrushes have an unusual mating system. Most of our songbirds are monogamous during the breeding season. A male pairs with a single female and the male defends the breeding territory against intrusions by other males.

Not so for Bicknell’s Thrushes. Their mating system is an open, communal system. Males do not maintain exclusive territories. Any of several males may sing from the same area in the same day.

Males and females both mate with multiple partners. Any given nest holds a genetic hodgepodge of offspring. The nest will have eggs laid by a single female but because of her multiple partners, some nestlings will be siblings and others will be half-siblings (due to different fathers). Males may have offspring in several different nests, corresponding to the multiple females they mate with. Thus, a nestling in one nest may have half-siblings (due to different mothers) in other nests. Now, that is a complicated family structure.

A male will bring food to more than one nest so the nestlings in any given nest may be fed by multiple males as well as by the mother.

Ornithologists refer to this mating system as polygamy. Nearly 95% of bird species show monogamy and most of the remainder display polygyny, in which one male may have multiple female partners but each female has only the one male partner. Red-winged Blackbirds are a local polygynous species. Polygamy is quite rare so it’s really neat to have a polygamous species in the Maine avifauna.

The entire population of Bicknell’s Thrushes is estimated to be around 125,000 individuals, making Bicknell’s Thrush a species of concern for environmental managers. These birds do nest at fairly high density (average of about 50 pairs per 100 acres) so habitat alteration of even a small area at high altitude can have serious repercussions for the species.

Conservationists worry about winter habitat degradation as well. The entire population winters mostly just a few islands in the Greater Antilles. Around 90% of Bicknell’s Thrushes overwinter on Hispaniola.

In terms of etymology, Bicknell’s Thrush was named after Eugene Bicknell, an amateur ornithologist. Bicknell discovered the species in the Catskill Mountains in the late 1800’s.

 

New birding app

A number of bird-related apps are available for smart phones and tablets. Some that I find particularly useful are BirdTunes, Merlin, National Aubudon’s Birds, iBird PRO and Sibley Birds.

The new Warbler App takes birding apps to a new level. This resource is a companion app to the marvelous field guide, The Warbler Guide, by Tom Stephenson and Scott Whittle that was published last year.

Like the apps above, the Warbler App provides vocalizations, photographs, line drawings and distribution maps for the birds covered. The Warbler App has full information on all of the 56 species of warblers that occur in the United States.

A skilled birder can identify a bird from five different views: above, below, side view (left or right), head-on and tail-on. Sometimes a head-on view is all you get or perhaps you get an obscured underside view through dense foliage. To clinch the identification, you really need to know all sides of the bird.

One beauty of the Warbler App is that you can see a warbler from any angle you want. Three-dimensional models of each species are provided. Using your finger, you can change the orientation to match the view you saw in the field.

The Warbler App has a great filter to allow you to quickly zoom in on an identification using morphological features as well as song features.

Take a look at this video to learn more: http://bit.ly/1KRbI61   The Warbler App is a game changer!

[First published on June 14, 2015]

Bicknell’s Thrush – I

By in Species Accounts

In birding as in life, the most satisfying accomplishments often require the most effort. Adding Bicknell’s Thrust to your life list is one of those high effort – high reward milestones.

Seven members of the thrush family nest in Maine. These species are Eastern Bluebird, American Robin and five species of thrushes with various amounts of spotting on their breast. These spot-breasted thrushes are among the finest of avian songsters. Their flute-like songs are ethereal, in part owing to the fact that these thrushes can control the left and right side of their syrinx, the organ that produces sound in birds. Thrushes can harmonize with themselves!

The Wood Thrush is more common to our south, but can reliably be found throughout the state. Veeries occur throughout the state. The Veery sings a song that spirals downward in pitch. The common name of this thrush comes from its characteristic call note, Veer. Swainson’s Thrush, whose song spirals upward rather than downward like the Veery’s song, is a bird of spruce-fir forests. This species is therefore scarce in the southern third of Maine. Hermit Thrushes are widely distributed in the state, nesting in bogs as well as conifer forests. The final species, Bicknell’s Thrush, is the least known of our thrushes and is restricted to high elevations.

Bicknell’s Thrush has only been recognized as a full species for the past two decades. It was formerly considered a subspecies of the widely distributed Gray-cheeked Thrush, which occurs from Alaska to Newfoundland in boreal habitats. Owing in large part to the work of the late Henri Ouellet, formerly of the Canadian Museum of Nature in Ottawa, the American Ornithologists Union elevated Bicknell’s Thrush to a new species.

Ouellet demonstrated that Bicknell’s Thrush is a valid species with several lines of evidence. He began by showing that Bicknell’s Thrushes differ subtly in the color of the upperparts, the tail feathers, the throat and the undersides from Gray-cheeked Thrushes. Bicknell’s are lightly smaller than Gray-cheeked’s.

To really make his case, Ouellet needed to demonstrate that the two forms are reproductively separate. He analyzed the songs of Gray-cheeked and Bicknell’s Thrushes, finding distinct differences. Furthermore, Bicknell’s Thrushes on their breeding grounds did not respond to playbacks of Gray-cheeked Thrushes. We see a similar situation with Alder Flycatcher and Willow Flycatcher. The two species are virtually dead ringers for each other but give distinctive songs. Females of one species do not respond to the songs of the other.

Ouellet’s final piece of evidence was a comparison of the DNA of the two forms. The analysis showed that the DNA differed by an amount similar to differences between other closely related species. The analysis suggested that the ancestral group split into Gray-cheeked Thrush and Bicknell’s Thrush about a million years ago.

The nesting range of Bicknell’s Thrush includes the Adirondack region of New York, and portions of Vermont, New Hampshire, Maine, Nova Scotia, New Brunswick and Quebec.

In northern New England, Bicknell’s Thrushes are generally found above 3000 feet in elevation. Bicknell’s Thrushes like stunted spruce-fir forest, particularly areas that have been disturbed by fir waves or rime ice accumulation during the winter. They may nest along the edge of ski trails. The thick re-growth of these disturbed areas is often nearly impenetrable, necessitating patience if you want to see one of these birds.

Male Bicknell’s Thrushes sing until the middle of June and then singing stops abruptly. Early morning is the peak singing time so camping out in proper habitat or hiking up before dawn is wise. You see what I mean by high effort! In short, if you want to see a Bicknell’s Thrush on its breeding habitat in Maine this year, you better plan a trip soon.

[First published on May 31, 2015]

Arrival Dates of Maine Migratory Birds: A Trans-century Comparison

By in Migration, Weather

Abundant evidence exists to show that the earth has been warming over the past century.  This evidence includes the melting of the polar ice caps with the consequent rise in sea level, earlier leaf-out dates for trees and bushes, earlier ice-out dates of lakes and the northern range expansion of various species.

The spring arrivals of migratory breeding birds are also sensitive to a warming world. With leaves emerging earlier, caterpillars become active earlier, providing earlier food for warblers and vireos. Nectar for hummingbirds should be available earlier.

A number of studies have documented earlier arrivals of migratory breeding birds. Bird clubs in the Worcester, Massachusetts area and in the Ithaca, New York area have been compiling first arrival-dates of migratory birds for over 100 years.  The data clearly show earlier arrivals in recent years for nearly all species of migratory birds frequenting those areas.

In 1994, I began a citizen-science project to monitor the arrival dates of over 100 species of Maine migratory breeding birds. Each volunteer is asked to note the first arrival of each species along with the location of the sighting.  This on-going project has taught us much about the nature of spring bird migration across the state.  We know have over 55,000 arrival dates in the dataset.  The collective contributions of so many volunteers have made this project possible.

We know over the period 1994 to 2014 that some bird species arrive a bit later in cold springs and a bit earlier in warm springs.  However, Maine does not have a continuous record of arrival dates to rival those of the Ithaca and Worcester bird clubs.

Maine however did have a bird organization, the Maine Ornithological Society, active around the turn of the 20th century.  This organization published the quarterly Journal of the Maine Ornithological Society (JMOS) from 1899-1911.  The journal regularly published arrival dates of Maine birds along with censuses of birds. Danny Kipervaser, Scott Lilley and I collated the arrival date data from the JMOS to compare to contemporary arrival dates.  Our expectation was that birds should be arriving earlier now compared to then.  Our predictions missed by a mile.

We only had sufficient data from the JMOS for 80 of the species I track in the current arrival date project.  Of those 80 species, only nine are now arriving earlier in modern years.  These included inland Common Loons, Great Blue Herons and Red-winged Blackbirds, all of which need open water in their lake or marsh habitats.  The other six species were American Woodcock, Ruby-throated Hummingbird,  Tennessee Warbler, White-throated Sparrow, Rose-breasted Grosbeak and Indigo Bunting. Most of these species arrive between four and eight days earlier now.

The most common result was to see no significant change in arrival dates across the time span.  Fifty-one species are arriving at the same schedule now as they did a century ago.  Quite a contrast with the Worcester and Ithaca records.

Remarkably, 20 species are now arriving significantly later than they did around the turn of the 20th century.  These species include seven aerial insectivores (swallows, nighthawks), three warblers, four sparrows and Bobolink.

What’s going on here?   I see two possible biases.  First, the amount of forests we have in Maine now is far greater than in 1900 when farmland was more extensive.  As a result, habitat for the sparrows and Bobolinks that seem to be arriving later were almost certainly more abundant then than they are now.  Thus, the chances of seeing an early arriving bird were higher a century ago.

Second, the JMOS birders were likely more in tune with nature than we are.  Outside on foot or on horse-drawn carriages, these observers would be less likely to miss a first arrival.  Despite our fine optics, the JMOS ornithologists might well have been keener observers than we are.

[Originally published on May 16, 2015]

The Sky Pointers

By in Behavior, Species Accounts

The sky pointers are back! Have you seen male Common Grackles walking or standing with their bills pointed up to the sky? This threat display is one of my favorite sights in the spring. I had to wait this spring; the arrival of Common Grackles was late this year but grackles are now abundant everywhere.

With a sleek, glossy blackish plumage and yellow eyes, the adult Common Grackle is a striking bird. The birds are about 12 inches long, including the long tail. It is not easy to tell males from females although males, in favorable light, have a glossy purple head and breast. The female is usually slightly smaller than the male. In flight, grackles hold their tails in a V, like the keel of a boat.

In northern New England, we have the subspecies of Common Grackle called the Bronzed Grackle. This form is named for the bronze cast to its feathers. Two more subspecies, nesting from southern New England to Florida, are collectively referred to as Purple Grackles. They lack the bronze undertones of our grackles and are mostly a deep purple. Some have a distinctive green “backpack”. The Bronzed Grackle and the Purple Grackle were once considered separate species.

Despite their sleek appearance, grackles will win no contests for the beauty of their songs. Both males and females sing the same harsh, squeaky song that some ornithologists interpret as “squ-eek”, “readle-eak” or “scuda-leek”. Some people think the song sounds like the opening of a gate with a rusty hinge. These birds also give a characteristic raspy “chack” call, often in flight.

Males sing more frequently than females and male song rates are highest early in the breeding season. Any individual sings a single song but there is a lot of variation among individuals. The songs therefore seem to be useful for individual identification.

This species is highly gregarious; if you see one, you will probably see ten. Except for females incubating eggs, grackles roost together at night in noisy roosts, sometimes more than 100 birds in one roost.

To attract a female, a male performs the song spread display. The male will raise the feathers around his neck, drop his wings and sing his song for a prospective mate.

Pairs form soon after the birds arrive so keep an eye out for the song spread behavior. The female builds the nest, usually well above the ground in a conifer. The male guards the female throughout the nest construction process. Once the nest is complete, the female will perform a wing quivering display, a signal that she is ready to mate.

The male aggressively keeps other males away from his mate. The sky pointing display is used to threaten other males. The vertical raising of the bill tells other males that they are not welcome. The display usually results in displacement of the intruding male.

Common Grackles may nest alone but more often in colonies of ten or more pairs in tall trees, especially evergreens. Sometimes, nests are made in freshwater marshes, old building and even the lower parts of Osprey nests. The nest is made of twigs and grass stems. Most nests contain 5-6 eggs, which the female incubates for about 14 days before hatching. The newly hatched birds are ready for their first flight in 14-16 days. Unlike their dark parents, juveniles are dark brown with brown eyes.

Some Common Grackles attain impressive ages. The oldest known Common Grackle was banded in Michigan and recaptured 20 years and 11 months later in Illinois! A Common Grackle in Minnesota lived to be at least 17 years old while a New Jersey bird lived to be at least 16 years and 1 month old. The average life span is likely much less than these extremes.

[Originally published on April 27, 2015]

The Tragedy of the Commons

By in Bird Conservation, Conservation

In 1960, the ecologist Garrett Hardin published an influential paper in the journal Science in which he developed the idea of the tragedy of the commons. The notion describes the conflict between self-interest and group-interest in the use of a shared resource. Typically, self-interest results in the overuse of the shared resource and everyone suffers for selfish behavior.

The cod fishery on the Grand Banks provides a compelling example. This region off the coast of Newfoundland seemed to have inexhaustible populations of cod. Cod had been harvested there in a sustainable fashion throughout the 1800’s and into the 1900’s. However, technological advances in locating and harvesting cod were developed in the 1960’s and the 1970’s. The efficiency of cod harvesting increased hugely and record landings of cod resulted. The cod populations began to diminish. Cod fishermen were forced to go further and further from land to find cod. By the time the cod population started to decline rapidly, the adoption of regulations on the cod fishery came too late. That fishery has collapsed, just at is has in the Gulf of Maine, and the cod populations have not recovered. The self-interest of each fishing boat to take many cod ruined the fishery for all.

The Passenger Pigeon provides another case in point. The staggeringly large populations of these birds seemed to provide a limitless resource of food. Efficient ways of killing large number of birds led to the carnage of thousands of birds. A highly social species, Passenger Pigeons ceased to reproduce when their populations fell. The demise of the Passenger was rapid and inexorable.

April 20 will be the 45th Earth Day. This day should remind us all to try to tread more lightly on the earth and redouble our efforts at conservation. Let’s think about a third resource that is being subjected to the tragedy of the commons: our atmosphere. I’ll focus particularly on the continuing rise of carbon dioxide in the atmosphere, stemming in large part from the burning of fossil fuels. The carbon dioxide concentration is now above 400 parts per million, well above the 350 ppm level that conservation biologists seek as the upper tolerable limit. We all know of the global warming, sea level rise, changes in the severity of weather and changes in the ranges and abundance of living organisms that this rise in carbon dioxide is causing and will continue to cause at ever accelerating rates. Our atmosphere is a shared resource and all humans, to different degrees, are treating the atmosphere selfishly. The tragedy of the commons strikes again.

To help reduce the rise of carbon dioxide, some birders are adopting the practice of green birding. To cut down on fossil fuel emissions, a green birder birds in local areas, requiring less auto fuel. Better yet, green birders simply walk or bike to birding locations.

The best green birding story from 2014 involved the Big Year undertaken by Dorian Anderson, a birder from Cambridge, Massachusetts. Traveling only by bicycle, kayak or foot, he managed to see 617 species of birds in the United States. He bicycled over 17,000 miles and visited 28 states (alas, ME was not on his itinerary). You can read about his Big Year at http://bikingforbirds.blogspot.com/

I think Dorian’s accomplishments are amazing considering that the all-time Big Year in North America produced 748 species. Neil Hayward drove nearly 52,000 miles, flew over 190,000 miles on 177 flights and sailed on 15 pelagic trips to set that record.

We all enjoy traveling to see birds. But to avert the tragedy of the commons for our atmosphere, we need to use a carbon offset calculator (many are on the web) to find ways we can contribute to forest plantings or other green activities to ameliorate our fuel consumption and carbon dioxide production. Otherwise, tragedy awaits.

[Originally published on April 13, 2015]

Purple Finch Winter Movments

By in Identification, Migration, Species Accounts

Purple Finches are regular if erratic visitors to our feeders.  The gorgeous males with their deep red breasts and heads can only be confused with male House Finches.  A male House Finch has brown streakings on the flanks with less extensive red (more reddish-orange) on its head.

Female Purple Finches are mostly brown and white.  The breast has dark streaks.  A bold white stripe lies just above the eye; this white supercilium is absent in female House Finches.

Have you noticed that male Purple Finches are usually outnumbered by females at your feeder?  Not so fast.  First-year males are dead ringers for female Purple Finches. You really have to have them in hand to tell them apart by examining the wear of the primary coverts and the shape of the tips of the outer tail feathers.  Some of those streaked Purple Finches at your feeder are first-year males.

Purple Finches belong to the suite of irruptive finches  popularly called the northern finches.  Purple Finches breed across the northern tier of the U.S. from Maine to Minnesota  and across the southern tier of the Canadian provinces.  A breeding population also occurs west of the Cascades and Sierra Nevada from California to British Columbia.

Strong southerly irruptions occur every other year in this species.  These biennial irruptions are thought to be driven by variation in the production of cone crops of the conifers on which the Purple Finches depend.

To gain some insight into these movements of Purple Finches, my wife Bets Brown and I analyzed all of the banding data on Purple Finches from the Bird Banding Laboratory over the period of 1921 until 2008.  Over 745,000 finches were banded over this period and almost 20,000 of those banded birds were subsequently recaptured (or in a few cases, found dead).

We were particularly interested in three questions.   During irruptions, do birds from one area like New England move straight south or do they spread across the continent (Purple Finches can be found throughout North America)? Do Purple Finches show fidelity to breeding sites?  Do Purple Finches show fidelity to wintering sites?

The analysis of banding data presents many challenges.  Banding effort is never constant either across space or time.  Most of the banding records come from the period 1960-1985.  Banding effort varies greatly among states and provinces.  Nevertheless, some general patterns can be discerned.

Birds banded in VT, NH and ME were re-encountered broadly but mostly in the eastern United States, curling eastward through the Gulf Coast states.  A few reached Texas and modest numbers occurred in MI, ONT, WI and MN.  A similar pattern emerged for birds originally banded in NY.

We also analyzed birds first banded in PA, NJ and NC.  These areas are south of the breeding range and were banded in the winter.  Re-encounters of these birds occurred mostly in the the New England and the eastern provinces.  The re-encounters are consistent with the data from birds originally banded in New England.

Moving to to the Midwest, birds originally banded in MI, WI and MN also were re-encountered broadly but most irruptions were due south.

Only 275 Purple Finches banded in the Pacific states or BC were re-encountered.  However, a consistent pattern was that those birds migrate west of the Cascades and Sierra Nevada.

We did find some evidence of breeding site fidelity across as many as five years.  Some wintering site fidelity was evident as well over periods of one to six years.  Uneven banding efforts prevent us from knowing how prevalent such fidelity is.

I’ll end with the most impressive distance between captures. A Purple Finch banded in Maine in 1966 was subsequently captured two years later in Texas, a distance of 1792 miles.

For a copy of our paper, visit http://bit.ly/1BntjMb

[Original published on March 29, 2015]

Flying Weasels; Changes in Backyard Winter Bird Communities

By in Behavior, Weather

Flying Weasels

I expect you have seen the amazing picture circulating on the internet of a weasel riding on top of a woodpecker. If not, here’s an article with several photos: http://slate.me/1FRvZFH

These photos are not the first documentation of a flying weasel. The author and wildlife artist Ernest Thompson Seton reported that someone shot an eagle and found the skull of a weasel attached to its throat. The best guess is that the eagle swooped down on the weasel, intending to make the weasel a meal. The would-be-prey must have latched onto the throat of the eagle and never let go. The eagle carried the reminder of that ill-considered weasel attack for the rest of its life.

This report is recounted in Annie Dillard’s lovely essay, Living Like Weasels. You can find the essay at: http://bit.ly/1gV7OIm.

 

Climate Change in our Backyards

The climate of North America has changed dramatically over the past 40 years with the greatest effects occurring during the winter. The winter climate has shifted to milder temperatures with less snow cover. Climate models predict more variable and intense precipitation, consistent with the snowy February we experienced. These models predict that the climate will continue to ameliorate over this century and that the most profound changes will occur in more northerly latitudes.

We expect that some species will expand their ranges northward as the climate warms. Such expansions are nicely documented by Christmas Bird Count data and Breeding Bird Survey data. Expanding species include Turkey Vultures, Tufted Titmice, Carolina Wrens, Northern Mockingbirds, Blue-winged Warblers and Northern Cardinals.

In a recent article in Global Change Biology, Karine Prince and Benjamin Zuckerberg have taken a broader approach to examine changing bird populations in th4 face of climate change. Rather than concentrating on single species, the authors take a community approach to examine the impacts of winter climate change. A community is simply all the species found in a given area.

Prince and Zuckerberg used Project Feeder Watch (hereafter, PFW) data for their analysis. PFW entails regular censuses of feeders from early November until late April. Observers report the birds visiting their feeders regularly over two-day periods. Over 10,000 PFW sites are sampled each year in the U.S. and Canada with each generating many checklists each year.

For their study, the authors confined their analysis to eastern North America south of the 50th parallel. They restricted their analysis to counts between December 1 to February 8. Their work was based on data from over 30,000 PFW sites over the period from the winter of 1989/1990 to the winter of 2010/2011.

The authors first used Christmas Bird Count to calculate the average minimum winter temperature of each species (Species Temperature Index or STI). This value was obtained by taking the average of the average minimum winter temperature within each Christmas Count circle where a species occurs. The result is a number that represents the minimum average temperature near the middle of the range of a species.

The authors then calculated a Community Temperature Index (CTI) by averaging the STIs for all species found in a particular PFW community. CTIs were calculated in two ways: by averaging the STIs of all species in the community and by weighting the CTI calculation by abundance of the species in the community.

The authors expected that CTI values would increase over the time period, reflecting the northern incursion of more southerly species with high STI values. In fact, that is the pattern that was found using both types of CTI measurements. The analysis shows winter bird communities in eastern North American are becoming dominated by species adapted to warmer climates. Many species are contributing to the changes in the CTIs with Chipping Sparrow and Yellow-rumped Warbler most important in the southeast and Eastern Bluebird and Carolina Wren in our part of the country.

[Originally published on March 15, 2015]

Storm Detection by Birds

By in Behavior, Migration, Physiology, Weather

We have certainly had no shortage of storms this winter. Perhaps you have wondered how birds can deal with the cold, the wind, and the snow to survive such challenging spells of bad weather.   The research done on birds’ ability to anticipate storms has provided some insights but much remains to be done. In today’s column, I’ll discuss the results of two recent papers that shed light on the effect of impending storms on bird behavior.

The first paper by Henry Streby of the University of California and colleagues was published earlier this year in the journal Current Biology. The researchers had 20 Golden-winged Warblers fitted with geo-locators in April of 2013. These small dataloggers continuously record light-levels and time. From the data, a researcher can track the longitude and latitude of a migrating bird. Birds must be captured so that the data from the geolocator can be read.

In April of 2014, Streby and colleagues tracked the arrival of nine of these marked birds back to their mountainous breeding territory in northeastern Tennessee from wintering areas in South America. The birds arrived in Tennessee between April 13 and April 27, 2014.

Between April 27 and April 30, a massive storm that spawned over 80 tornadoes developed over the middle of the United States. The eastern Tennessee Golden-winged Warblers were able to detect the impending storm well before it arrived. What did the birds do? All nine of the warblers vacated their breeding grounds. Five of them did return after their storm and their geolocators were resampled. All five of these birds took evasive action to avoid the storm.

On April 27, tornadoes were being generated from Kansas to Texas. By the following day, the storm was less than 100 miles from the Golden-winged Warblers’ breeding area. The storm was quite powerful when it arrived in northwestern Tennessee, generating winds of over 100 mph.

But the wind posed no problem for the five warblers. They had moved to Florida’s Gulf Coast, beyond the range of the storm. One of the birds even flew to Cuba.

How did the birds know the tornadoes were coming? The authors believe that the birds were detecting infrasound, sound whose frequency is far too low for humans to hear. Tornadoes generate infrasounds that are propagated through the ground.

Storms are usually associated with low-pressure systems so falling barometric pressure could be a cue that a storm is approaching. A recent paper by Creagh Breuner and colleagues examined this phenomenon. The paper was published in 2013 in the Journal of Experimental Biology.

When humans hear that a blizzard is approaching, we see a run on groceries, batteries and candles. Shouldn’t birds prepare for inclement weather as well? The Breuner team addressed this question by studying White-crowned Sparrows on the breeding grounds at high altitude in Montana. Spring snowstorms are frequent.

In particular, the researchers searched for a relationship between falling barometric pressure and behaviors that might help the birds weather the storm. The researchers predicted that falling barometric pressure should cause an increase in mass (due increased feeding rate_, an increase in the rate at which fat is deposited and hormonal changes associated with stress. They also did experiments on captive birds by artificially lowering the air pressure and looking for changes in behavior.

The results were mixed. The authors clearly showed that the sparrows could detect changes in barometric pressure in their lab experiments. In the field, falling barometric pressure did not result in an increase in mass or in stress hormone production. The researchers did find a significant relationship between fat deposition and barometric pressure but the effect was very slight. In the lab, birds sometimes increased their feeding rate as pressure dropped but again stress hormone levels did not change. We have much more to learn about these intriguing responses.

[Originally published on March 1, 2015]

Maine Christmas Bird Count Summary – III

By in Christmas Count Summaries

This column is the last of three reviewing the recent Christmas Bird Counts conducted in Maine.  We’ll concentrate on coastal counts from southern and mid-coast Maine in this column.  These counts traditionally have the greatest diversity and abundance of birds on Maine counts.  Such was the case again this year.

The York Count, held on December 15, yielded 94 species.  Waterfowl diversity was excellent with 19 species tallied.  The most unusual were three Wood Ducks, two Gadwall and a King Eider among the 984 Common Eiders.

The sharp-eyed York counters found three species of loons: 132 Common Loons, 13 Red-throated Loons and a rarity, a Pacific Loon.

Coastal York County has the mildest (or maybe I should say least harsh!) winter weather in the state.  We therefore expect a good smattering of lingering summer birds on the York County.  This year did not disappoint.  Counters found a Great Blue Heron, two Red-shouldered Hawks, three Belted Kingfishers, a Yellow-bellied Sapsucker, two Winter Wrens, a Marsh Wren, four Hermit Thrushes, an Orange-crowned Warblers, a Common Yellowthroat and an Eastern Meadowlark.  Whew!

The Biddeford-Kennebunkport Count was held on December 27 and produced a list of 89 species.  The 17 species of waterfowl included an American Wigeon, two Ring-necked Ducks along with the more regular species.

Raptors included two Northern Harriers, two Red-shouldered Hawks, a Merlin, two Snowy Owls and a Northern Saw-whet Owl.  Like the York County Count, this count produced a diverse collection of lingering species, including five Great Blue Herons, two Killdeer, three Belted Kingfishers, six Northern Flickers, two Tree Swallows, two American Pipits, an American Redstart (excellent!), a Western Tanager and 37 Red-winged Blackbirds.

Shorebirds were notable.  The observers found 23 Ruddy Turnstones, 13 Sanderlings, six Dunlin and a gross of Purple Sandpipers.

The Portland Count topped the century mark with 105 species.  The 21 species was spectacular, highlighted by a Gadwall, a Eurasian Wigeon, and 11 Ruddy Ducks.  The requisite lingering Great Blue Herons were found (12).

Two Northern Harriers were the most unusual hawks. Owl diversity was super with five species tallied: seven Great Horned Owls, two Snowy Owls and single Long-eared, Barred and Northern Saw-whet Owls.

Notable lingering species included three Belted Kingfishers, 13 Northern Flickers, 15 Hermit Thrushes, a Brown Thrasher (excellent find), a Common Yellowthroat, a Lark Sparrow, two Red-winged Blackbirds and a Common Grackle.

We’ll move north of Portland to the Bath-Phippsburg area. The count there on December 20 resulted in a fine total of 85 species.

One Snow Goose was found among the 1,1114 Canada Geese.  I thought the 74 Northern Pintails were a remarkable total.

Raptor diversity was excellent with seven species of diurnal raptors and two nocturnal raptors.  The former included two Northern Harriers, a Peregrine Falcon and a Merlin.  Two owl species were found, Snowy and Barred Owls.

The climate in the Bath area is a bit harsher than the climate in York County.  It is not surprising that fewer half-hardy birds were found lingering there.  Nevertheless, lingering birds included six Great Blue Herons, four Belted Kingfishers, two Hermit Thrushes, two Northern Mockingbirds, two Swamp Sparrows and a single Red-winged Blackbird and Common Grackle.

We’ll end our survey a bit further north along the mid-coast in the Thomaston-Rockland area.  Counters there on December 20 found 79 species.  Three species of Aythya ducks were found (two Ring-necked Ducks, eight Greater Scaup, two Lesser Scaup). American Coots were plentiful with 148 tallied.

One Thick-billed Murre and one Razorbill were found along with the more expected 22 Black Guillemots.

Lingering species included a Belted Kingfisher, two Northern Flickers, a Gray Catbird (excellent) and two Red-winged Blackbirds.  A Clay-colored Sparrow was a superb addition to the count.  Two northerly species that are uncommon this winter were found on the count: a Northern Shrike and three Evening Grosbeaks.

[Originally published on February 15, 2015]

Maine Christmas Bird Count Summary – II

By in Christmas Count Summaries

This column is the second of three summarizing the results of some of the recent Christmas Bird Counts in Maine. We’ll visit inland central Maine and two downeast coastal sites today.

I find it interesting to compare the counts from count circles that are geographically close. The Augusta and Waterville counts nearly overlap and were both held on December 14. Both counts had good diversity; Augusta counters found 53 species and Waterville counters found 61.

A Great Blue Heron was found on both counts. Raptor diversity was notable with each count yielding at least one Cooper’s Hawk, Sharp-shinned Hawk and Red-tailed Hawk. A highlight was a Peregrine Falcon in Waterville, flying south along the Kennebec River to the delight of the observers.

Both counts had the expected Common Goldeneyes and Waterville counters were able to pick out two Barrow’s Goldeneyes. A Ring-necked Duck was a nice find in Augusta as well as three Common Loons. An unfrozen outlet stream from China Lake yielded an American Coot for Waterville counters.

Both counts had multiple Red-bellied Woodpeckers, a species that was virtually unknown in New England 45 years ago. Their range expansion has been remarkable. Augusta also had a Yellow-bellied Sapsucker.

The two counts had similar counts for the more expected songbirds. Both counts had good number of White-throated Sparrows and Song Sparrows, two species that are often scarce in the winter. Counters in both circles tallied multiple Eastern Bluebirds, also unusual in winter in this part of the state.

Augusta had a Northern Shrike, a Carolina Wren and a Red-winged Blackbird. Waterville had a Snowy Owl, 30 Horned Larks, two Savannah Sparrows and five Evening Grosbeaks. An Eastern Screech-Owl was heard trilling twice in Waterville but unfortunately the bird could not be relocated and recorded or photographed.

Let’s head east to Bangor/Bucksport. The count on January 1 produced a nice count of 52 species. The proximity to the coast explains the five Bufflehead and eight Red-breasted Mergansers. All three species of accipiter hawks were tallied (Northern Goshawk is the toughest one to find). Two Snowy Owls added to the raptor list. A total of 27 songbirds were found with highlights being a Northern Shrike, two Carolina Wrens and a Hermit Thrush. Northern Cardinals continue to push northward in the state. The Bangor counters found 95 of these beauties, a new high for this count.

Continuing to the coast, we can compare two adjacent counts: the Mt. Desert Island count and the Schoodic Peninsula count. The MDI count was held on December 20 and yielded 64 species. Puddle duck diversity was great; a Gadwall, a Northern Pintail and two American Wigeons joined the expected Mallards (743) and American Black Ducks (519). Eight Ruddy Ducks were notable. No Red-throated Loons appeared this year but there were plenty of Common Loons. Both Double-crested Cormorant (7) and Great Cormorant (15) were found this year.

Twenty-three species of songbirds were counted. Good sightings included a Northern Shrike, eight Song Sparrows and 13 White-throated Sparrows. The best songbird records were for members of the blackbird family. MDI counters found three Red-winged Blackbirds, two Common Grackles and a Baltimore Oriole. I am sure these lingering birds are long gone now.

The counters on the Schoodic Peninsula count started the new year off well with a count of 51 species. It’s always a treat to see Harlequin Ducks and the Schoodic counters found six. Buffleheads, Common Eiders and Long-tailed Ducks were the most abundant waterfowl, represented by 1,116, 801 and 446 individuals, respectively. Three Red-throated Loons were nice to see. A lone Iceland Gull was discovered.

Songbird diversity was paltry with only 20 species found. Among those species, goodies included a Common Grackle, a Baltimore Oriole and a Yellow-rumped Warbler. Finches were hard to come by; 22 American Goldfinches and three House Finches were the only ones tallied.

[Originally published on February 1, 2015]

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