I suspect that, like me, you made sure your bird feeders were well stocked before the blizzard that hit on February 8 and 9. Our feeders were pretty busy all through the blizzard. Clearly, birds readily accept our handouts.
Have you ever thought about the ethics of bird feeding? Is it OK if your bird feeder becomes empty for a while this winter? I get asked this last question quite a lot by people who plan to be away for part of the winter, depriving their local birds of a formerly constant source of food. Are we doing our feeder birds harm by giving them food and then taking it away? In other words, do our feeder birds become dependent on bird feeders?
To cut to the chase, local birds do not become dependent on feeders. One should not worry about a feeder becoming empty when high winds of a blizzard blow your feeder to the ground or when birds deplete the food while you are away.
We do know that feeding the birds increases winter survivorship. The best information for this effect concerns Black-capped Chickadees from studies conducted in Wisconsin, Pennsylvania and Ontario.
To investigate if birds do become dependent on handouts form humans, Stanley Temple and Margaret Brittingham performed an intriguing experiment. These two scientists extended their earlier work showing that winter bird feeding improved chickadee winter survival. Their next step was a study to compare winter survival of chickadees between two areas. In one area, chickadees had been given sunflower seeds continuously for several years. In the second area, no bird feeders were ever present. The authors took away the bird feeders from the first area where birds had been feeding on sunflower seeds for years and monitored winter survivorship.
If the population given sunflower seeds in previous years had a lower survivorship than the population with no bird feeders, one could claim that the birds in the first area had become dependent on the sunflower seeds. But there was no difference in survivorship for the two populations. The previously fed chickadees did as well in the following year feeding on natural food as the unfed chickadees did.
Similar studies have not been done for other North American species that frequent feeders but I expect that results would be similar. Depending on a single source of food is risky for any winter bird. Winter songbirds commonly range over areas of 10 to 25 acres. Much of this area is regularly patrolled and food is taken from a number of different parts of their winter area.
Bird feeding has a number of effects. It brings birds close to our homes where we can enjoy them from the comfort of our kitchen or living room. Bird feeding has strong effects on the birds as well. In addition to increasing survivorship, bird feeding has certainly facilitated the expansion of a number of birds. In the state of Maine, House Finches are rarely found far from feeders. Tufted Titmice have been steadily expanding their range northward over the past 20 years, undoubtedly aided by the provision of food during the winter at bird feeders. These birds regularly occur in central Maine now and I have even seen one in the winter at the north end of Flagstaff Lake. Mourning Doves, Northern Cardinals and Carolina Wrens fall in the same category of birds expanding their range northward.
We know that bird feeders can change the habitat preference of birds. For instance, American Goldfinches in the absence of bird feeders are equally likely to be found in areas dominated by coniferous forest, areas dominated by deciduous forest and areas we can classify as “edge” habitats (suburban areas, fields reverting to forest). However, the goldfinches will quickly forsake forest habitat for edge habitat if one puts up bird feeders in the edge habitat.
[First published on February 17, 2013]
Categories: Behavior · Bird Conservation
This post is the last of three in which I will describe some of the highlights of Maine Christmas Bird Counts (hereafter, CBC’s). We’ll travel along the coast this time.
The York CBC, held on December 20, is the southernmost of the Maine counts. This count produced 100 species. The species list is a nice list of expected birds, invaders from the north and half-hardy lingering species.
Fourteen species of waterfowl were counted. The York County shore is a stronghold for Harlequin Ducks in the state and the count of 121 was impressive. Six species of diurnal raptors were counted, including nine Cooper’s Hawks.
The alcid count was excellent. We expect Black Guillemots in the winter. Razorbills are hit-or-miss; 123 on this count were a big hit. Great finds for other members of the family were a single Atlantic Puffin and Common Murre. Both of these species tend to winter well offshore.
Irruptive species on this count included one Bohemian Waxwing, 32 Pine Grosbeaks, seven Red Crossbills, seven White-winged Crossbills, 40 Common Redpolls and 11 Pine Siskins.
The list and numbers of lingering birds was even more impressive. Counters found three Great Blue Herons, 15 Carolina Wrens, three Winter Wrens, a Marsh Wren, 106(!) Eastern Bluebirds, 543 American Robins, 31 Northern Mockingbirds, 11 American Pipits, two Yellow-breasted Chats, a Savannah Sparrow, two Red-winged Blackbirds and two Brown-headed Cowbirds. That is an impressive count!
You can see the value of the CBC. This diversity and abundance of lingering birds was unheard of 30 years ago. The data provide a compelling signal of the impacts of climate change as our winters ameliorate.
The Biddeford-Kennebunkport Count (December 30) resulted in a fine count of 89 species. Six species of diurnal raptors included a Red-shouldered Hawk and a Peregrine Falcon. The 182 Wild Turkeys were an all-time high count. Five irruptive finch species were found, including a single Evening Grosbeak.
Half-hardy species included six Belted Kingfishers, one Northern Flicker, five Carolina Wrens, one Winter Wren, five American Pipits, two Pine Warblers, one Palm Warbler, a Fox Sparrow, and two Common Grackles.
The Thomaston-Rockland CBC (December 22) ended with a total of 80 species, an excellent count for this part of the state. A Pacific Loon was a super find. Two species of falcons graced this count: a Merlin and two Peregrine Falcons.
American Coots assemble in this area in the fall until the lakes freeze. The relatively mild December resulted in a nice count of 129 lingering coots. Other lingering birds included 15 Ring-necked Ducks, three Great Blue Herons, a Yellow-bellied Sapsucker, four Carolina Wrens, four Eastern Bluebirds, two Savannah Sparrows, a Gray Catbird and a Red-winged Blackbird.
The North Penobscot Bay CBC (December 28) produced a list of 68 species. This area is reliable for Ruddy Ducks in the winter; 119 of these ducks cooperated. Oddly, a single cormorant (a Double-crested) appeared on this year’s count. The two waxwing species were equally represented: eight Cedars and eight Bohemians.
A Lark Sparrow was a genuine rarity, an excellent find. Other highlights were two Red-bellied Woodpeckers, a Northern Flicker, two Northern Shrikes, a Gray Catbird, two White-crowned Sparrows, and a Red-winged Blackbird. The counts of 331 Common Redpolls and 25 Evening Grosbeaks were impressive.
Fifty-seven species were found on the Deer Isle CBC (December 29). Highlights included six Red-bellied Woodpeckers, two Tufted Titmice and a courageous Hermit Thrush. The count of 208 Common Redpolls was impressive.
The Schoodic CBC (January 1) resulted in a count of 48 species. A highlight was a Black-bellied Plover. Only one American Tree Sparrow was recorded.
The Moose Island-Jonesport count (December 16) produced a tally of 57 species. Highlights were a Barrow’s Goldeneye, two Belted Kingfishers, a Yellow-bellied Sapsucker, and three Northern Shrikes. Irruptive finches were pretty scarce; Pine Grosbeaks, White-winged Crossbills, Common Redpolls and Pine Siskins collectively yielded 41 individuals.
[FIrst published on February 3, 2013]
Categories: Christmas Count Summaries
This post is the second of three in which I will describe some of the notable sightings of some of the Christmas Bird Counts (hereafter, CBC’s) conducted in Maine. We’ll take a tour around inland portions of the state this week. The last column will cover some of the coastal and off-shore counts.
The Lewiston-Auburn CBC on December 22 produced a nice mixture of lingering species and winter visitors from the north. Enough water was open to provide habitat for 80 Lesser Scaup, five Common Loons, a Pied-billed Grebe, two Horned Grebes, and a Great Cormorant. Half-hardy species included 16 Eastern Bluebirds, nine Northern Mockingbirds and 39 American Robins.
Winter visitors included a Peregrine Falcon, a Northern Shrike, 75 Bohemian Waxwings (along with 26 Cedar Waxwings), 20 Pine Grosbeaks and 296 Common Redpolls. The final species tally was 52.
The Unity CBC produced 44 species on December 15. Lingering birds included a Great Blue Heron and two American Pipits. A Rough-legged Hawk was a treat along with three Northern Goshawks.
Winter finches included 8 Pine Grosbeaks, 318 Common Redpolls, a single Pine Siskin, and nine Evening Grosbeaks.
The Bangor-Bucksport CBC on December 29 provided a marvelous mixture of rare birds, lingering birds and irruptive finches. A feeding station in Winterport produced a Townsend’s Warbler, a western species that appears sporadically in the winter in the east. As of this writing, this hardy and perhaps confused warbler is still present. Most Townsend’s Warblers winter in Mexico or further south in Central America.
A Pine Warbler was also found on the count; most winter in the southeastern and Gulf Coast states. A Common Grackle and a Baltimore Oriole were also unexpected lingering birds. One Common Loon was sighted.
A suite of birds have been expanding northward through Maine. Excellent counts of some of these species on this CBC indicate continued expansion of ranges. Bangor counters found three Red-bellied Woodpeckers, 99 Tufted Titmice, five Northern Mockingbirds, and 75 Northern Cardinals.
Our state bird seems to be doing well in this area; CBC participants counted 870 Black-capped Chickadees.
This count had its share of northern visitors as well: a Peregrine Falcon, two Northern Shrikes, 78 Bohemian Waxwings, 110 Pine Grosbeaks and 175 Common Redpolls.
Let’s head up to Aroostook Count for a couple of CBC’s. These counts had a distinctly northern flavor. The Presque Isle CBC yielded a nice list of 35 species. Two unexpected lingering birds were a Brown Thrasher and a Savannah Sparrow.
A common pattern in the northern part of our state is that Common Ravens outnumber American Crows. Final score on this count: ravens 192, crows 138. A Gray Jay was not unexpected but always a delight to see. The open fields of eastern Aroostook County are always good for ground-living passerines. The nice count of 242 Snow Buntings was expected.
Irruptive finches included four Red Crossbills, 615 Common Redpolls and 30 Evening Grosbeaks.
Further north, the Caribou CBC produced 30 species on December 29. No lingering birds were found here. Two Northern Cardinals were nice finds. Highlights were a Black-backed Woodpecker, a Northern Shrike, 935 Common Redpolls, one Hoary Redpoll, 68 Pine Grosbeaks, and 17 Evening Grosbeaks.
[First published on January 20, 2013]
Categories: Christmas Count Summaries
The 113th National Audubon Society Christmas Bird Count is now over. Between December 14, 2012 and January 5, birders picked a day to count as many birds as possible in a circular area, 15 miles in diameter. These count circles are visited each year, providing a valuable snapshot of changing bird populations.
This column is the first of three in which I will describe some of the notable sightings of the 30+ Christmas Bird Counts (hereafter, CBC’s) conducted in Maine this year.
The Christmas Bird Season really offers us a look at bird abundance in early winter; results would likely be different if the counts were conducted in mid-February.
When analyzing Christmas Bird Count results, I find it useful to divide birds into three groups. The first group includes the resident birds like Black-capped Chickadees and American Crows. Have there been any changes in their population size compared to previous counts?
Then there are lingering migrants, sometimes called half-hardy species. Most individuals will spend the winter well to our south but often stick around in Maine until deteriorating weather conditions or the freezing of lakes force them southward. With mostly open water through December, one might expect a good smattering of lingering waterbirds on this year’s counts.
Finally, there are winter visitors that migrate in some years from more northerly areas to spend a “balmy” winter in Maine. These birds include Great Gray Owls, Snowy Owls, Bohemian Waxwings, Northern Shrikes and the northern finches like Common Redpolls, Pine Siskins, Pine Grosbeaks, White-winged Crossbills and Red Crossbills. This year’s counts indicate the current winter is a good one for some of these occasional northern visitors.
The Greater Portland Count on December 15 produced a record-high 111 species.
Canada Geese were exceptionally abundant with 2,656 tallied. Five species of owls, including Snowy Owl and Long-eared Owl, were impressive. A Clay-colored Sparrow was a nice addition.
The count yielded a rich diversity of half-hardy species: one Ring-necked Duck, seven Great Blue Herons, five Black-crowned Night Herons, seven Turkey Vultures, one American Kestrel, two American Coots, three Belted Kingfishers, twelve Northern Flickers, six Carolina Wrens, one Marsh Wren, 30 Eastern Bluebirds, one Hermit Thrush, 30 Northern Mockingbirds, six Yellow-rumped Warblers, one Common Yellowthroat, one Yellow-breasted Chat, four Savannah Sparrows, one Swamp Sparrow, and four Red-winged Blackbirds.
The irruptive finches were well represented with two Red Crossbills, 17 White-winged Crossbills, 179 Common Redpolls and a near-record high 91 Pine Grosbeaks.
The Waterville Count was held on December 16 and produced a count of 60 species. A couple of immature Great Cormorants at Fort Halifax were nice finds. Lingering aquatic species included a male Northern Harrier, two Carolina Wrens, one Winter Wren, one Northern Mockingbird, a Common Grackle, and three Brown-headed Cowbirds. A White-crowned Sparrow was an unusual bird for this count.
For winter visitors, the counters found an Iceland Gull, 110 Bohemian Waxwings, 104 Pine Grosbeaks, 642 Common Redpolls, and two Pine Siskins.
[First published on January 6, 2013]
Categories: Christmas Count Summaries
Around the turn of the 20th century, a popular activity in New England towns on Christmas Day was the “side hunt”. The men of the town would divide up into two sides and then comb the countryside and shore, shooting every bird (and mammal as well) they could. At the end of the day, each side would pile up all the animal carcasses they had collected. The team with the bigger pile was declared the winner. If you are like me, you regard this practice as barbaric and senseless. Frank Chapman, an ornithologist at the American Museum of Natural History and a leader of the nascent National Audubon Society, thought so too and offered an alternative. Instead of shooting birds, people were encouraged to go out and count the birds they saw. The counts that people made were then published and served as a record of the bird abundance and distribution for particular areas. Thus was born the Christmas Bird Count.
The first censuses were held on Christmas Day, 1900. Twenty-five counts and 27 birders conducted those counts. Most were in the northeastern United States but Toronto and Pacific Grove, California were covered as well. Collectively, these original counts produced a cumulative list of 90 species of birds.
A standardized method for conducting Christmas Bird Counts (hereafter, CBC’s) was established to allow comparisons of counts between different areas. The unit of a CBC is the count circle, a circle with a radius of 7.5 miles from a fixed point. On one day during the national count period (mid-December to early January), observers spread out in a count circle and count all the birds they see or hear in one calendar day. The weather, number of observers and number of hours spent in the field are published on the National Audubon Society’s website (http://www.audubon.org/).
These counts provide a rich source of information on changing bird populations. For instance, the northward and southward expansion of the House Finch, introduced into the East in New York City, can be followed by looking at CBC’s over the years. Similarly, the northward expansion of Red-bellied Woodpeckers, Tufted Titmice, Carolina Wrens, and Northern Mockingbirds is well documented. Downward trends sound the alarm that particular species may be in trouble. For instance, Harlequin Ducks have been declining on CBC’s in eastern Canada and are now listed as an Endangered Species in Canada.
CBC’s have become very popular activities, with a particular increase in the number of counts occurring in the early 1970′s. For the 2011/2012 CBC (the 112th CBC), there were 2,248 individual counts, conducted by 63.227 observers. Of these counts, 2,149 were conducted in North America with the remainder in tropical areas including Central and South America, Bermuda, Hawaii and islands in the South Pacific. U. S. observers counted a total of 60,502,185 birds belonging to 666 species during the 2011/2012 CBC. We have come a long way from the days of side hunts.
In Maine, there were 32 CBC’s during the 2011/2012 count season. These counts ranged from Presque Isle in the north to York County in the south and from Eastport in the east to Sweden in the west.
You do not have to be an expert to participate in a CBC. Some CBC’s have already occurred this year, others are yet to take place. You can find a list of all Maine CBC’s and their coordinators at http://maineaudubon.org/wildlife-habitat/christmas-bird-count/ I encourage you to contact an organizer and take part in the fun. Usually the organizer will host a social gathering after the sun goes down for all the participants to have a warm drink, share the day’s memorable sightings, and compile the list.
In the first three columns of every year, I discuss the highlights of many of the Maine CBC’s. You’ll see those posts soon.
[First published on December 23, 2012]
Categories: History · Uncategorized
The morning chorus of bird song is a phenomenon we associate with summer. Male songbirds sing vigorously then to attract a mate and ward off other males. Of course, one of the joys of birding is learning to identify singing males by their species-specific songs.Outside of the breeding season, males typically don’t sing. However, most birds have distinctive call notes that are used to communicate with other members of their species. Birders can use these call notes to identify birds in the winter.
This winter is shaping up as a great winter for the irruptive winter finches. All of our finches call frequently. Their call notes are among the most difficult of our winter birds to learn but well worth the effort. Finches are very mobile, social birds. Flocks often pass over at fairly high heights, too high to permit identification through binoculars. Knowing the call notes can clinch an identification.
Our most familiar finch is the American Goldfinch. In flight, goldfinches give a call note that can be represented as “per-chick-o-ree” or “potato chip”. Goldfinches also give a rather whiny “chi ee” call as well. The scientific name of the goldfinch, Carduelis tristis, reflects the sound of this call; tristis is Latin for sad, an apt description of the call note.
The Pine Siskin, like the goldfinch, is a small finch with an absolutely distinctive call. It’s a buzzy note that screeches upward. Think of it as an upslurred “zreeee”.
A third small finch, the Common Redpoll, can be easily confused with the American Goldfinch by its calls. The typical flight call is a “chit chit” or “chit chit chit”. Redpolls also have a note that sounds like the sad, whiny note of the goldfinch.
Two medium-sized finches, the House Finch and the Purple Finch, occur regularly in our area. It’s easy to study the calls of House Finches as they are very common at feeders. Their call can be written as “cheet”. It is a sweet note, often repeated several times when a bird takes flight.
The Purple Finch has a much softer call note. Usually given in flight, the note can be described as a soft “pit”.
I devoted the last two columns to two species of grosbeaks that are currently widespread in Maine: the Evening Grosbeak and the Pine Grosbeak. Both call frequently in flight and often fly well above of the treetops. The Evening Grosbeak’s call is sometimes written as “cleer” or “cleep”. The note carries well. Words are not adequate to describe the distinctive sound of this call. Once heard, the call will become one of the most distinctive ones you will encounter birding.
The Pine Grosbeak has a softer call. Usually, these birds give a two- or three-note whistle with the second note having the highest pitch. This whistle is a beautiful call that evokes images of the snow-covered North Woods. In flight, a soft trill is often heard as well.
I will end with Brown Creepers, cryptic yet surprisingly common birds in Maine. Their mottled brown plumage on their upperparts makes them magically disappear as they forage on tree trunks. However, their presence is often revealed to an experienced birder by their high-pitched, buzzy “seet” note. One you learn to recognize this call note, you will be surprised how often you will detect the presence of a Brown Creeper. Seeing one is another matter.
Learning bird notes by reading descriptions of what they sound like is a challenge. It’s much better is to let the birds be your teachers. When you hear a call you don’t recognize, track the bird down and identify it by sight. There are lots of good commercial recordings of bird sounds. A wonderful website that provides multiple sound recordings for each species is can be found at: (http://www.allaboutbirds.org/).
[First published on December 9, 2012]
Categories: Behavior · Vocalizations
Perhaps this winter will be the winter of the grosbeaks. In the last column, I wrote about the irruption of evening grosbeaks into central and southern Maine. Sightings continue throughout the state. Many people are seeing evening grosbeaks at their feeders for the first time in a decade or more.
We seem to have a nice influx of pine grosbeaks into the state as well this fall. Pine grosbeaks do irrupt into central and southern Maine more regularly than evening grosbeaks, but they scarcely put in an appearance in some winters.
Both of these species are aptly named grosbeaks because their beaks are indeed large, impressive tools capable of generating significant force. Just ask any bird-bander who has extracted an evening grosbeak from a mist net. But the name grosbeak is really a descriptive term rather than a taxonomic unit. Pine grosbeaks and evening grosbeaks belong to the finch family while a summer favorite, the rose-breasted grosbeak, belongs to the cardinal family.
An adult male pine grosbeak is hard to misidentify. The head, breast, sides, back and rump are a bright carmine red. The wings are mostly blackish with two conspicuous white wing bars. The belly region is gray. A pine grosbeak is much larger than a house finch or purple finch.
Females are more subtle in their coloration, but strikingly beautiful as well.
Some females are mostly gray, again with the two prominent wing bars. However, some have russet feathers on their head and rumps. Some of these birds are females, but others may be first-winter males. It is not safe to identify the gender of a russet-colored pine grosbeak.
The beak of a pine grosbeak differs from that of an evening grosbeak. The pine grosbeak bill is shorter and curved. The overall shape is more rounded than the massive conical bill of an evening grosbeak.
As with most birds, the bill and the diet fit like a hand and glove. Rather than crushing large seeds for sustenance, a pine grosbeak feeds on a variety of buds (conifers, elms and maples among others) as well as small seeds like those of box elders and ashes. Pine grosbeaks will often feed on fruits during the winter; mountain ash berries are a favorite. Apples or cherries hanging on a tree are used by pine grosbeaks. The many ornamental cherry trees on the Colby College campus are a magnet for these birds.
Like most finches, pine grosbeaks are social during the winter. Tight-knit groups of five to 10 birds form a cohesive group during the winter, often mingling with other such groups. Ornithologists suspect that each of these small groups is a family unit that has migrated together.
Pine grosbeaks are usually detected by sound rather than sight. They give a distinctive three-note flight call, sometimes rendered as tee-tee-tew. This call is strongly reminiscent of the call of a greater yellowlegs, but with a much sweeter, less harsh tone.
Evening Grosbeaks Revisited
And now another installment from the small-world department. In the last column, I wrote about the cursory observations of evening grosbeaks by the geologist Major Joseph Delafield in 1823 that led to the ill-fitting common name of this finch species. I received an email from Joseph Delafield of South Portland, the great-great-grandson and namesake of Major Delafield. Joseph has a portrait of his great-great-grandfather in his house as well as the diary from which the quotation I used was taken!
Joseph filled me in on the details of Major Delafield’s career. He served as agent for the U.S. commission charged with determining the boundary between Canada and the United States. He recognized the potential mining value of rocks at the western end of Lake Superior (the Mesabi iron ore range) and negotiated the inclusion of that property as American soil.
[First published on November 27, 2012]
Categories: History · Species Accounts
Evening Grosbeaks, one of the most enigmatic and erratic of our winter finches, have been appearing across Maine this fall. We had a dozen of these beauties at our sunflower feeders in China a couple of weeks ago. Maybe these birds are harbingers of a much-anticipated irruption into New England.
These robust, colorful birds add welcome color to the muted fall and winter landscapes in Maine. The males with their yellow bodies, brown heads with yellow eyebrows and a large patch of white on each black wing, are stunning. The understated females, with tones of bluish-gray on their body and a large white patch on each black wing, have a beauty of their own. Evening Grosbeaks are conspicuous, usually announcing their presence with metallic “cleep” notes, reminiscent of a House Sparrow’s call. They love sunflower seeds so keep your feeders stocked.
The scientific name of this finch is Coccothraustes vespertinus. The genus name “Coccothraustes ” means “kernel breaker”, certainly appropriate for this bird with a stout, conical beak. The species name “vespertinus“ refers to “evening”, a puzzling claim since these birds are active all day long as anyone lucky enough to have them at a feeder can attest!
The evening reference comes from observations made by a Major Delafield, a United States boundary agent in 1823:
”At twilight, the bird which I had before heard to cry in a singular strain, and only at his hour, made its appearance close by my tent, and a flock of about half a dozen perched on the bushes in my encampment . . .. My inference was then, and is now, that this bird dwells in such dark retreats, and leaves them at the approach of night”.
Obviously, Delafield was not a very good field naturalist! We know that Evening Grosbeak go to roost around dusk like any self-respecting perching bird. Nevertheless, Delafield’s observations were taken seriously by subsequent scientists who dubbed Coccothraustes vespertinus the Evening Grosbeak. I think Evening Grosbeak is the most inaccurate common name of any North American bird, beating out Ring-necked Duck.
Evening Grosbeaks are relatively recent arrivals in Maine. The great Massachusetts ornithologist, Edward Forbush, claims that until the winter of 1889-1890, Evening Grosbeaks were virtually unknown east of Ohio. During that winter, an eastward invasion brought these birds into Massachusetts, nearly as far east as Boston.
A second large invasion came in 1910-1911, leading to the gradual establishment of Evening Grosbeaks as breeding birds in southeastern Canada and northeastern United States.
Some have suggested that the immigration of Evening Grosbeaks into the east was facilitated by the spread of box elder (Acer negundo) trees. The seeds and buds of box elders are highly favored by Evening Grosbeaks. The planting of these trees as ornamentals may have permitted the invasion of Evening Grosbeaks to Maine.
Evening Grosbeaks nest throughout the state of Maine, but their numbers vary erratically from year to year and from place to place. Winter numbers rise as individuals from more northerly populations come into Maine and further south in numbers that vary widely from year to year.
Highly gregarious outside of the breeding season, Evening Grosbeaks have a hierarchical social system where males (which are larger) are dominant to the smaller females. These interactions can be easily seen at a feeder. Research by David Prescott showed that female Evening Grosbeaks tend to migrate further south than the males. Prescott proposed two reasons to explain this differential migration. First, the subordinate females may be forced further south because of the dominant males. Alternatively, the larger males may better able to withstand cold temperatures. In any case, count the number of male and female Evening Grosbeaks this winter. If Prescott’s pattern holds true, you should see a predominance of gaudy males here in Maine.
[First published on November 11, 2012]
One of the great challenges for biologists is recognizing the limits of a species. Humans provide a nice example of a highly variable species. As a demonstration of this variability, I like to show my students a portrait of the basketball great, Wilt Chamberlain and the equally famous jockey, Willie Shoemaker. The dark-skinned Chamberlain towers more than two feet over the white-skinned Shoemaker. That’s variation! But we know that humans around the world are capable of producing fertile offspring, one definition of a species.
On the other hand, some species are morphologically nearly identical to other species. We call such similar forms sibling species. Traill’s Flycatcher is a case in point. A painting of this “species” appeared in Audubon’s Birds of America.
Field work in the 1950’s and 1960’s showed that some males consistently sang a sneezy “fitz-bew” song and others sang a “fee-be-o” song. Furthermore, females were only attracted to one of the two song types. Based on this research, the AOU Check-list Committee split Traill’s Flycatcher into Willow Flycatcher and Alder Flycatcher. Good luck distinguishing one from the other in the field if they are not singing.
A more recent example is the 2010 split of the Winter Wren into two species, the western Pacific Wren and our eastern form, still called Winter Wren. Research showed that the two species do not interbreed where their ranges overlap in the west.
Red Crossbills present an even more complicated and controversial situation. In 1988, Jeff Groth published an extensive monograph showing that ten types of Red Crossbills occur across North America. These types are best identified by their flight calls, but subtle morphological differences occur as well. Groth showed that different types have preferences for different types of conifer cones.
Matthew Young has recently produced a nice update of our knowledge of these crossbill types. He also has made recordings of the different flight calls. All can be downloaded at: http://ebird.org/content/ebird/news/red-crossbill-types
Click on “Add to Cart”. You will be taken to a Checkout page but the price is right: $0.00. Submit your order and you will get two pdf documents on Red Crossbills and 11 sound files of flight calls.
Much remains to be learned about the distribution of these 10 types of Red Crossbills. Types 1, 2 and 10 occur regularly in New England and New York and a couple more appear on occasion. Type 8 is found exclusively in Newfoundland.
What do we do with this information? Should we recognize ten species of Red Crossbills instead of recognizing a single species? I suspect that much more work will need to be done, particularly examining the ability of different types to interbreed, before the AOU Check-list Committee would be willing to split Red Crossbill into multiple species.
Nevertheless, it is fun to try to identify the type of Red Crossbill you hear when are birding in crossbill country. Downloading the sound files will give you the resources you need to train yourself to give type identification a try.
World Life Listing
Many birders enjoy competitive birding as they seek to build the largest year list, state list or list for any other area of interest. A milestone in world listing was recently passed by Tom Gullick, an expatriate Englishman living in Spain. Gullick is a seasoned world-traveler and bird tour leader.
Last summer at the age of 81, Gullick visited the remote Indonesian island of Yamdena where he saw Wallace’s Fruit Dove. That species represented his 9,000th bird! Gullick is the first birder to ever reach that milestone.
About 1,500 species remain in the world for Gullick to see but he indicates he does not have the 10,000 species milestone on his radar. I’m sure those remaining birds are either extraordinarily rare or highly restricted in distribution.
[First published on October 28, 2012]
Categories: Species Accounts
Last weekend, I took my Marine Ecology students on a trip to Cobscook Bay. One of our activities was a whale watch off Head Harbour on Campobello Island. Birds were abundant with lots of Northern Gannets, Sooty Shearwaters, a few Manx Shearwaters, Black-legged Kittiwakes, Common Loons, many Bonaparte’s Gulls and even a few Atlantic Puffins. And yes, we saw marine mammals. A couple of Minke Whales and groups of Harbor Porpoises tantalized us by breaking the surface of the water briefly.
Perhaps you feel a bit frustrated like me watching these marine vertebrates because a good bit of their lives is lived under the water out of our vision. Thanks to underwater cameras, small submersibles and SCUBA equipment, we do have some understanding of life under the water surface for marine birds and mammals.
It is not surprising that these animals have particular adaptations that permit them to make a living by diving underwater. Some of these adaptations are morphological and others are physiological. Let’s explore some of these adaptations using the Common Loon.
Common Loons are excellent divers, capable or reaching depths of about 200 feet. A loon can stay under water for as long as 15 minutes.
Loons swim underwater using only their feet. The wings of loons are relatively short and are held tightly against the body during a dive.
The legs of a loon are set far back on the body. The legs are splayed out laterally when the bird swims. When a loon is first diving from the surface, it breaks the surface by alternating strokes with the left and right leg. Once underwater, the legs beat synchronously.
The lateral placement of the legs makes for hydrodynamic efficiency. If the legs were close together, the turbulent eddies created by one leg would interfere with smooth movement through the water of the other leg. The lateral arrangement allows a loon to generate maximum thrust while minimizing hydrodynamic drag.
The feet of loons are large and webbed. The real power in swimming is generated by the rearward movement of those webbed feet against the water. When the loon moves its feet forward during the recovery stroke, the toes are brought together causing the web to collapse and minimizing the effort needed to get the foot ready for the next power stroke.
Loons have a peculiar yet elegantly adapted leg. Unlike most birds, the major lower bone (the tibiotarsus or the large drumstick bone on a chicken) of a loon has a prominent extension, called the cnemial crest, that extends well beyond the joint where the upper leg bone (the femur) joins. This cnemial crest provides a broad attachment for the large muscles of the upper leg. The massive thigh muscles generate the huge force that allows loons to dive so deeply and so quickly.
The long bones of birds are not hollow as seen in most species of birds. These heavier bones make it easier for a loon to dive. Just before a dive, a loon compresses its body, driving out the air trapped within its feathers. Air trapped in the feathers would increase the buoyancy of the loon and make it harder to dive.
On to a physiological adaptation. Loons, like other diving birds and marine mammals, have the ability to store large quantities of oxygen in their blood. Even so, staying underwater for 15 minutes is no easy task. During diving, a loon undergoes a physiological change called the diving reflex. Oxygen flow to most body parts is greatly reduced except to the heart and nervous system.
This reflex causes the heart rate to slow, decreasing the amount of oxygen used by the heart. Muscles and other parts of the body have to perform anaerobic (oxygen-free) metabolism until the bird surfaces.
[First published on October 14, 2012]
Categories: Morphology · Species Accounts