Highlights of Maine Christmas Bird Counts – 2018/19 – II

By in Christmas Count Summaries

This post is the second of three reporting highlights of some of the Maine Christmas Bird Counts. We’ll take a tour along the coast in this account.

Let’s begin with the York County count, conducted on December 17. This region has the most moderate climate in the state so we always expect a diversity of lingering breeding birds and migrants. This year did not disappoint.

Eastern Bluebirds have become dependable birds in December along the southern Maine coast. This year, 110 were found on this count. Other lingering species included two Great Blue Herons, three Northern Harriers, five Belted Kingfishers, four Northern Flickers, eight Carolina Wrens, a Ruby-crowned Kinglet, four Gray Catbirds, 23 Northern Mockingbirds and a Chipping Sparrow.

Fourteen species of waterfowl were present with Mallards being most abundant with 1109 observed. A Northern Pintail was a nice find.

Grebes were hard to come by. Only two Red-necked Grebes and a dozen Horned Grebes were seen. Twenty-nine Great Cormorants represents a fine total.

Other highlights along the shore were 118 Sanderlings, five Dunlin, ten Black-legged Kittiwakes, a Dovekie and 17 Razorbills.

Three Merlins, a Peregrine Falcon and two Northern Shrikes (uncommon this winter) were no doubt terrorizing smaller birds.

The Biddeford/Kennebunkport count yielded 80 species on December 29. Highlights of the fine total of 18 waterfowl species were a Eurasian Wigeon, seven Harlequin Ducks and a Barrow’s Goldeneye. Ten Northern Gannets were detected just offshore.

Three Dunlin were nice finds in the Maine winter. A Peregrine Falcon was found as well.

Eastern Bluebirds put in a good appearance with 132 seen. Other lingering birds included a Great Blue Heron, an American Woodcock, a Northern Flicker, two Carolina Wrens, 18 Northern Mockingbirds, a Yellow-rumped Warbler, two Fox Sparrows, a Savannah Sparrow and a Common Grackle.

Finches were scarce with the highlight being 18 Evening Grosbeaks.

The North Penobscot Bay Count in the Belfast area resulted in a tally of 61 species on December 29. Two Wood Ducks were the only unexpected finds among 13 species of waterfowl.

Five Razorbills were a delightful surprise as was a Peregrine Falcon. Two Northern Shrikes were notable.

Lingering birds included a Belted Kingfisher, two Northern Flickers and a hardy Carolina Wren.

Among the finches, the 68 Pine Grosbeaks and 23 Evening Grosbeaks were stand-outs.

The Mt. Desert Island count on December 15 produced a list of 57 species. Twelve species of waterfowl were tallied. This area is usually good for Common Eiders in the winter and the 1502 on the count confirmed the pattern. A Barrow’s Goldeneye was present.

Four Great Cormorants were unsurprising but the two Double-crested Cormorants were for this time of year.

A single Bonaparte’s Gull added a fourth gull species to the count along with the more common Herring Gulls, Ring-billed Gulls and Great Black-backed Gulls.

The highlight had to be a rare Red-headed Woodpecker. Lingering species were few and far between with a Belted Kingfisher being most notable.

Northern finches were represented by 40 Purple Finches, a White-winged Crossbill and 19 Pine Siskins.

Just a bit to the north and east, the Schoodic Count on New Year’s Day, produced a list of 62 species in the rain and snow. Fourteen species of waterfowl were highlighted by 54 Harlequin Ducks.

The count of 93 Red-necked Grebes was a fine total. The highlight of the count was the discovery of four species of alcids. In addition to the expected Black Guillemots, the Schoodic teams found 55 Razorbills, three Thick-billed Murres and, best of all, three Dovekies.

The gull count included 113 Black-legged Kittiwakes and two Iceland Gulls (uncommon this winter in Maine).

A Northern Harrier, a Red-winged Blackbird and a Common Grackle were hardy lingerers. Winter visitors from the north included a Northern Shrike and 22 Pine Grosbeaks.

Highlights of Maine Christmas Bird Counts – 2018/19 – I

By in Christmas Count Summaries

This column is the first of three reviewing the highlights of some of Maine Christmas Bird Counts. This count season spanned December 15 through January 5.

The Greater Portland count was held on December 15. The count yielded 102 species. The highlight of the count was Great Black Hawk, still present on count day in the Deering Oaks Park area in downtown Portland. This record represents not only a first for the count and for Maine CBCs but for the United States!

Nineteen species of waterfowl were found. Uncommon ducks for this time of year included a Wood Duck, an American Wigeon, six Gadwall, three Northern Pintail and a Barrow’s Goldeneye. Sixty-three Horned Grebes and 36 Red-necked Grebes were normal counts. Both of our expected loons were present: five Red-throated Loons and 224 Common Loons.

Shorebirds included a single Killdeer, a single Sanderling and 57 Purple Sandpipers. A single Dovekie and 32 Razorbills along with 15 Black Guillemots made for a nice alcid count.

Lingering breeding birds are always of interest. This year’s count produced a rich diversity of such hardy (or foolhardy!) birds: 10 Great Blue Herons, a Turkey Vulture, four Northern Harriers, a Red-shouldered Hawk, 10 Belted Kingfishers, 10 Northern Flickers, three Winter Wrens, 19 Hermit Thrushes, 10 Gray Catbirds, two Brown Thrashers, four Savannah Sparrows, a Lincoln’s Sparrow, three Swamp Sparrows, a Baltimore Oriole and five Red-winged Blackbirds. Amazing!

Northern finches were mostly absent with a Pine Grosbeak and 15 Pine Siskins present.  Bohemian Waxwings and Snow Buntings, present in other parts of the state, were no-shows.

The Augusta Count was also held on December 15, yielding 52 species. Still and moving water was mostly frozen so the modest waterfowl count was expected. Six species were found with Mallards (152) being the most common.

The expected winter gulls (Ring-billed Gull, Herring Gull, Great Black-backed Gull) were joined by one Lesser Black-backed Gull and one Iceland Gull.

A lone Northern Shrike was a nice sighting of this erratic winter visitor. A whopping 308 Bohemian Waxwings were tallied for an excellent early winter total. Their cousin, the Cedar Waxwing, was represented by 38 individuals. Irruptive finches were sparse with 11 Pine Grosbeaks and 13 Pine Siskins present.

Lingering birds from the fall included three Belted Kingfishers, 16 Eastern Bluebirds, a Chipping Sparrow and a Fox Sparrow. A single White-crowned Sparrow was a surprise; these birds don’t breed in Maine and usually pass through in migration by early November.

The Unity CBC was also held on December 15, producing a list 47 species. With most water frozen, waterfowl were hard to find and only five species were tallied: five Canada Geese, 10 Mallards, four American Black Ducks, one Hooded Merganser and two Common Mergansers. A Glaucous Gull among the 503 Herring Gulls was a nice find.

The Unity counters put in some nocturnal birding time and found a Great Horned Owl and four Barred Owls.

Lingering migrants were absent, a striking contrast to the earlier counts in this column. Bohemian Waxwings were common with 184 showing off their beautiful plumage.

In what will I think become a common refrain, northern finches were present but not in the numbers we saw in November. In Unity, 70 Pine Grosbeaks, five Pine Siskins and 17 Evening Grosbeaks were present.

The Moose Island-Jonesport count was also conducted on December 15. That count produced a list of 65 species.

Sixteen species of waterfowl included 21 Harlequin Ducks and a Barrow’s Goldeneye among the more common coastal ducks. A single Red-throated Loon was found. Alcids included a Thick-billed Murre and three Razorbills.

A Snowy Owl was a treat. One Northern Shrike was found, no doubt terrorizing small songbirds and mammals.

Three Belted Kingfishers were late for this area. Irruptive finches included 17 Purple Finches, 11 Red Crossbills and 6 Pine Siskins.

Audubon Christmas Bird Count Data and Ornithological Research

By in Foraging, Migration

The 119th Audubon Christmas Bird Count is now underway, continuing until January 5. I’ll report on the highlights of Maine counts in the next few posts.

The Christmas Bird Count (CBC) was conceived by Frank Chapman, an ornithologist at the American Museum of Natural History, shortly before the turn of the 20th century. In the magazine Bird Lore (now Audubon magazine), Chapman proposed an alternative to the barbaric side hunts that we common in the late 1800s. In a side hunt, villagers divided up into teams and then scoured the countryside, shooting any bird seen. The carcasses would be piled up and the team with the most birds killed would be declared the winner of the side hunt. You can imagine the carnage.

Chapman suggested people might better put their energy into counting rather than killing birds. Some Bird Lore readers agreed and 27 people conducted the first CBCs in 1900. The CBC program took off and continues to grow.

A count is standardized. A group counts all the birds seen on one day between the middle of December and early January within a circle 15 miles in diameter. The number of observers is recorded so that the counts can be adjusted for effort.

Over 70,000 counters participate now in nearly 3000 count circles. Counts are done in a number of countries around the world. The standardized protocol means that counts can be meaningfully compared among count circles as well as between years.

The CBC has become a valuable tool to track changes in the distribution and abundance of the birds of North America and beyond. The National Audubon Society makes the data available to researchers. Dozens of scientific articles have been published based on this rich database. I’ll describe three of my own papers as examples of the value of CBC data.

The practice of bird feeding has been on the increase since 1970. We know that bird feeding can facilitate range expansions and alter habitat preferences. Some have argued that the increase in bird feeders is allowing irruptive finches to overwinter at higher latitudes if supplemental food is available, courtesy of humans. I used CBC data to test for this short-stopping effect.

I analyzed the CBC data from eastern North America between 1970 and 1994. Although I found that the southern extent of irruptions for six species of northern finches was further early in the study period, I was unable to show an increase in the number of birds wintering at higher latitudes as the short-stopping hypothesis requires. My analysis indicates that short-stopping is a weak effect at best.

Using CBC data from 1960 until 2014, my wife Bets Brown and I, analyzed the abundance data for Red-breasted Nuthatch to examine the irruptions of this species on both geographic and temporal scales. We found that this widely distributed species showed broad synchrony in irruptions across North America. Irruptions west of the Rocky Mountains were generally accompanied by irruptions in the Midwest and along the eastern seaboard. At finer geographic scales, we found great variability. Abundance might be high in one state or even CBC circle but low in an adjacent state or CBC circle. Their winter abundance is a patchwork of high and low densities.

We compared the nuthatch pattern to that of three irruptive finches: Purple Finch, Pine Siskin and Common Redpoll. We found no relationship between Red-breasted Nuthatch irruptions and the irruptions of the three finches.

One of my students, Paul Dougherty, and I used CBC data to test for synchrony of the irruptions of northern finches. We know that Common Redpolls commonly show a biennial pattern to their irruptions. We found that American Goldfinches in the northern parts show a biennial pattern opposite that of the redpolls. In the north, redpolls and goldfinches alternate their irruptions.

If interested, you can download copies of these papers at: http://web.colby.edu/whwilson/publications/

Red-breasted Nuthatch Irruptions and Foraging Behavior

By in Foraging, Species Accounts

The big birding news in Maine is the reappearance of the Great Black Hawk in Deering Oaks Park in Portland starting on November 29 and still present as of December 28. Hundreds of birders have come to see this rarity. The story has made the national news.

This hawk is the first record of this species in the United States. This bird is apparently the same one that appeared in Texas in April and Biddeford in August.

The northern finch irruptions continue. Lots of people are seeing Evening Grosbeaks at their feeders, sometimes 40 birds or more. Pine Siskins are widespread. Common Redpolls have not staged a massive incursion yet (fingers crossed) nor have Pine Grosbeaks.

An invasion by irruptive species requires two elements. First, the food resources on the breeding grounds have to be poor, forcing birds to come south for the winter. We know that condition is met. The second element is that the birds have to wander to southern parts where food is plenteous. But, we might have excellent food availability but the irruptive birds don’t venture our way.

In Maine, we are lucky to have the diminutive Red-breasted Nuthatch along with its larger cousin, the White-breasted Nuthatch. The latter is more abundant overall. The Red-breasted Nuthatch is a denizen of coniferous forests and is subject to the same year-to-year fluctuations in food that influence finches. Red-breasted Nuthatches are therefore an irruptive species.

In the southern half of Maine, Red-breasted Nuthatches may be scarce in some years and common in others. To our south beyond their breeding range, Red-breasteds are a winter treat. This winter is a major invasion year for Red-breasted Nuthatches. A quick search of eBird records indicates these nuthatches have made it as far down as Florida, the Gulf States with even a few into Mexico.

Red-breasted Nuthatches in the winter tend to be alone or sometimes in small flocks. One or two may join a Black-capped Chickadee winter flock along with Downy Woodpeckers, Tufted Titmice and Golden-crowned Kinglets.

Insectivorous in the summer, Red-breasted Nuthatches rely heavily on conifer seeds the rest of the year. These birds are readily attracted to feeding stations. Black oil sunflower seeds, safflower seeds and peanuts are favorite foods.

Watch for hoarding behavior at your feeder if you have the pleasure of a Red-breasted Nuthatch or two. A nuthatch will come in to grab a seed and then fly away and cache seed in the bark of a tree. Sometimes the larder is close by but may be quite distant.

About 20 years ago, I conducted a research project to examine the impact of supplemental food (sunflower seeds) on Black-capped Chickadees during the winter. I did the research at the northern end of Long Falls Dam Road on the east side of Flagstaff Lake.  I chose this region because the winters at that altitude are severe and virtually no humans in that area during the winter. Therefore, I knew I was the only person feeding the birds there.

I placed color bands in unique combinations on over 100 chickadees for the project. I also caught 10 Red-breasted Nuthatches and provided them with colored leg bracelets as well.

Since I could tell banded individuals apart by their color-band combinations, I could count the number of visits each bird made to the feeders. I found a seven-fold difference in feeding rate for those ten Red-breasted Nuthatches. Some used the feeders frequently while others, perhaps more adept at finding natural food, were more circumspect about visiting the feeders.

All ten of the Red-breasted Nuthatches survived the winter. Each was seen at least once during very week of the study, indicating high fidelity to the feeders. If you are fortunate enough to get Red-breasted Nuthatches at your feeders, chances are good they will stick around for a while, particularly in the winter.

Recent Research on Tufted Titmice

By in Behavior, Species Accounts

In the last post, I discussed the hopeful prediction that this winter will bring irruptive finches into Maine based on seed production to our north.  So far, those prognosticators are looking good. Pine Siskins are common across the state now. Evening Grosbeaks are putting on a better show than they have in many years. Pine Grosbeaks have been reported from scattered locations. I know of several Common Redpoll reports, including some from York County. Bring ‘em on!

I’ll devote today’s column to some recent research on Tufted Titmice published in the Wilson Journal of Ornithology this year. This species has been expanding northward in the state, starting in the 1970s.  Titmice are pretty well established in the southern half of the state now. Double-digit counts of the species are common on Christmas Bird Counts as far north as Skowhegan, Bangor and Orono.

The expansion into Maine is a continuation of the northward expansion into southern New England that started around 1940. Prof. Sylvia Halkin and John Correia at Central Connecticut State University recently published a paper in which they explored the interactions between Black-capped Chickadees and Tufted Titmice. Both are members of the family Paridae and have similar diets and foraging styles. One might rightly expect the two species would compete. Has the arrival of titmice altered the behavior of the chickadees?

The researchers studied the two species in three forest tracts and at one feeding station. In the forested sites, they recorded the portions of trees where individuals of each species foraged. Chickadees spent more time in the outer, upper portion of the canopy than the titmice. Other portions of trees were equally attractive to the titmice.

Chickadees spent more time foraging in bushes than the titmice. On the other hand, titmice spent much of their time foraging on the ground; chickadees rarely spent time there.

A titmouse is twice as heavy as a chickadee. Perhaps, titmioce have a harder time foraging on the thin branches of the outer upper canopy. The larger size of the titmice may make it easier for them to feed on the bigger branches of the canopy. At any rate, the two species seem to be partitioning food resources by feeding in different sub-habitats.

At the feeding station, the titmice were clearly dominant. Both species visited the feeder, took a single seed and then left. When a bird was at the feeder, an approaching bird had the choice of waiting or challenging the bird at the feeder. Chickadees waited for both other chickadees and titmice more often than they challenged them. Titmice usually waited for other titmice but tried to displace chickadees. The titmice were always successful in challenging chickadees and usually won challenges against other titmice.

The birds had the choice of safflower seeds, black oil sunflower seeds with the shell intact and black oil sunflower seeds with the shell removed. All three types of food were taken but titmice preferred the safflower seeds and the chickadees preferred the shelled sunflower seeds.

The study results indicate that differences in foraging sites and food preference may mitigate competition between the two species. The authors point out that competition might be more severe in more northerly areas like Maine where our colder winters require greater food consumption.

Wieteke Holthuijzen reports on eavesdropping by Veeries on Tufted Titmice in New York. Veeries are active participants in the dusk chorus. Their songs and calls can attract predators in the twilight.

Tufted Titmouse give a distinct alarm call (the seet call). Holthuijzen tested the notion that Veeries might use titmice alarm calls to modify their vocalization rate at dusk. By playing recordings of the titmouse alarm, she found that Veeries did not change their song output but did increase their own call notes, acting as secondary informants to other Veeries about danger in the vicinity.

Irruptive Finch Prognosis for the 2018/2019 Winter

By in Migration, Weather

Common Redpolls are among my favorite birds. To have dozens of these delightful sprites fighting over the nyger seed (marketed as thistle seed) at our feeder is always a joy. But, alas, redpolls do not visit us every winter.  Every November, I start to wonder if the coming winter will be filled with redpolls here in Maine.

Common Redpolls belong to a group of finches called the northern finches or the irruptive finches. This group of birds includes the Common Redpoll along with the less common Hoary Redpoll, Pine Siskins, Pine Grosbeaks, Evening Grosbeaks, Red Crossbills and White-winged Crossbills. Most individuals of these species nest north of us. In some years, these birds will spend the winter on their breeding grounds but in other years move south to places like Maine or even further south. The birds erupt from their northerly breeding grounds and irrupt or move into more areas to the south with more moderate winters.

It’s not the cold per se that drives these irruptions. Rather it is the availability of food. If sufficient food is available, Common Redpolls can pass the winter above the Arctic Circle. Those metabolic challenges cannot be met when birds cannot acquire enough food to stoke their internal furnaces.

In the case of the irruptive finches, the food required is seeds. Redpolls are fond of birch seeds, Pine Siskins and Purple Finches use the seeds from conifers with smaller cones (spruce, firs, hemlocks, larch) while Evening Grosbeaks and the crossbills can handle the large cones of pines. Pine Grosbeaks are a bit unusual in that they depend on fruits.

We know that seed production varies greatly from year to year. Trees of a particular species are synchronized in their reproduction. So, over broad swaths of forest, Red Spruce may produce prodigious amounts of cones in one year followed by several years of modest to low production. A year of plenty is called a mast year.

This variability of seed production is thought to be an adaptation against seed predators (insects, birds, squirrels). Low seed production keeps the seed predator populations low and then a mast year overwhelms the capacity of the seed predators, giving many of the seeds a chance to germinate.

During mast years for the tree of choice, northern finches do not need to migrate south for the winter. In years of moderate production, some finches will irrupt. It is only when seed production is poor that we see massive influxes of northern finches.

What will the winter of 2018/2019 bring for northern finch abundance? Ron Pittaway, a birder in Ontario, offers a prognostication every fall for the strength of the irruption of northern finches. He bases his predictions on reports of cone and seed production. Although his predictions are specifically geared to Ontario, the patterns he describes are applicable to northern New England and the Maritime Provinces.

Ron reports that birch and cone crops are poor to low in most of Ontario and northeastern North America with the exception of Newfoundland, which has a bounteous spruce crop. We can expect an irruption of winter finches into southern Ontario, southern Quebec, the Maritime Provinces, upstate New York and New England. Yippee!

The first Common Redpolls should be arriving soon in your neighborhood if they are not already here. Look for them in weedy fields. Once they discover nyger seeds at people’s feeders, feeding frenzies can ensue. Let the chaos begin.

Pine Siskins are on the move already and some may continue farther south or west. The same pattern may occur in Purple Finches.

Evening Grosbeaks are expected to stage a moderate flight south this year. I have already heard of over thirty sighting of these gluttonous beauties at feeding stations in Maine.

Mountain Ash berries are scarce to the north of us so the dearth of food should push Pine Grosbeaks into Maine this winter.

USFWS Survey on Wildlife-Associated Recreation

By in Birding and Birders

In 2016, the U.S. Fish and Wildlife Service conducted a National Survey of Fishing, Hunting and Wildlife-Associated Recreation. A report of the analysis of the data from that survey was published earlier this year.

In today’s column, we will take a look at the demographic and economic factors that influence birding and other wildlife-watching activities.

The survey indicated that a third of U.S. citizens 16 years and older engaged in wildlife watching in 2016. Wildlife watching was broadly defined as observing, feeding and photographing wildlife, visiting parks and natural areas because of wildlife, and maintaining plantings and natural areas to benefit wildlife.  Wildlife watching was categorized as either close to home (within one mile of the residence) or away from home (more than a mile away).

About 45 million people observed birds around home on trips in 2016. Most of these people (86 percent) watched birds at or near their homes. Thirty-six percent also took trips away from home to see birds. Birders spent 105 days birding close to home and 16 days on more distant trips.

Wildlife watchers contributed $75.9 billion dollars to the economy in 2016, an average of $1,193 per person. Nearly three-quarters of those expenditures were for binoculars, cameras and other equipment. About 15% of the expenditures were for travel (food, lodging, transportation). The remainder went to miscellaneous items like land purchases, bird seed, field guides, plantings and membership dues.

For around-the-home wildlife watchers, 70% fed the birds in 2016, 38% photographed birds and 10% made plantings to improve the habitat for birds and other wildlife.

Although birds were the wildlife most commonly observed around home (88% of observers), other wildlife drew interest as well. In decreasing order, these were mammals, insects and spiders, reptiles and amphibians, and fish.

Nation-wide, 32% of people observed wildlife at home.  The most enthusiastic watchers are in New England; 36% of us watch birds and other wildlife in our yards and gardens. The least avid watchers are in the Rocky Mountain West, Texas, Oklahoma, Arkansas and Louisiana (26-27%).

Wildlife watching around home is greater for males than females; 58% of such watchers are male. Wildlife watching increases with age. Only 16-18% of 16-24 year-olds watch wildlife. Participation increases to 38% for 45-54 year-olds and peaks at 48% for 55-64 year-olds.

For away from home watching, 28% of wildlife watchers took trips to observe or photograph wildlife. About 69% only took trips within their state of residence, 10% took trips both inside and outside their state with the remaining 21% only taking trips beyond their state borders.

Birds were the focus of the majority of these trips. The most popular types of birds sought were waterfowl and birds of prey with songbirds close behind.

Nationally, 9% of wildlife watchers made trips away from home. We are a little more active in New England with12% of watchers venturing on trips to enjoy wildlife.

The gender bias for trips away from home is more biased than the bias for at home watchers. Two-thirds of wildlife watchers taking trips to see wildlife are male. Age does not vary greatly in terms of trip participation. Observers between 55 and 64 years old are most likely to take a trip (13%) but youngsters 16-18 are nearly as active (11%).

Household income does not have a strong effect on the proportion of observers taking wildlife trips. Three income classes are tied for highest proportion (13%) of observers going on trips: $20,000-$25,000, $35,000-$40,000 and $100,000-$150,000.

Only 4% of watchers with less than 12 years of education took wildlife trips away from home, while 12% of college graduates and 20% of people with more than four years of college went afield to see wildlife.

Participation rates by race showed great variation. Eleven percent of whites took trips to see wildlife but only 2% of African-Americans and 1% of Asians.

Fall Departure Project; Nature Moment Videos

By in Migration, Species Accounts

Last spring, I wrote a column summarizing the citizen-science project I conducted over the past 24 years to monitor the spring arrivals of Maine migratory breeding birds. With the aid of several hundred birders who contributed first arrival dates, we have learned much about the regional and year-to-year patterns of spring bird migration in our state. Here is a webtool to explore the data: https://hobbes.colby.edu/arrival/

When I launched the project in 1994, I simultaneously launched a project to monitor the fall departures of those same Maine migratory birds. That project never took flight, mainly because of the time commitment involved. It’s easy for observers to record their first sighting of an Eastern Phoebe or Yellow Warbler in the spring. Determining the last data of sighting in the fall requires continuous record keeping.

With the advent of eBird in 2002, many data on the occurrence of bird species in Maine became available to researchers. Although most of the records in eBird date from 2002 onward, some birders and researchers have uploaded older data into the eBird database. I used this treasure trove of information to determine the fall departure dates of our migratory breeding birds and to examine differences in departure among regions in the state on the north-south axis.

To make this study comparable to the spring arrival project, I only used eBird fall occurrence data from 1994 through 2017.

You can download a copy of the paper at: https://bit.ly/2RyVCIs

For the analysis, I defined the beginning of fall as the Last Safe Date provided by the Maine Breeding Bird Atlas Project. The Last Safe Date is the latest date for a species when nesting is expected. For instance, the Last Safe Date for Barn Swallow is July 21 but the Last Safe Date for Eastern Bluebird is August 21. I defined the end of the fall migration as December 31 although the vast majority of fall migrants departed well before then.

I divided the state into three bands of equal latitude. The North Region extended south to 45.7 °N, the South Region extended from 42.6 °N south and the Central Region was in between. I analyzed the data for each region separately.

For the occurrence dates between the Last Safe Date and December 31 for a particular species, I examined the latest half of the records, the latest 10 percent of the records and latest 5 percent of the records. For each set, I calculated the mid-point (median) of the arrival dates.  Using only the latest 5% of the records provides a better measure of the last departure date but at the expense of small sample sizes.

Space limitations prevent the listing of the departure dates here so download the paper to see those dates.

As an overview, one would expect that birds would depart from Aroostook County and other North Region areas first. Occurrence records in the South Region should be the latest.

These expectations were met for most of the species analyzed. Median departure dates from the North Region were a few days to several weeks earlier than departures from the South Region with departures in the Central Region being intermediate.

A few species (Cliff Swallows, Canada Warblers, White-throated Sparrows) unexpectedly showed latest departures from the Central Region rather than the Southern Region. I suspect the Central Region provides more favorable staging areas for these species, causing them to linger, and then pass quickly through the Southern Region where they are less likely to be detected.

Nature Videos

Nat Wheelwright, recently retired Professor of Biology at Bowdoin College, has just completed his weekly video series, Nature Moments, on the natural history of the common plants and animals of eastern North America. You can visit at: https://research.bowdoin.edu/nature-moments/

The site is a great resource for naturalists and educators. Don’t miss the video called The Sound of Extinction.

The Changing Tools of Birding

By in Birding and Birders, Migration

A couple of recent re-sightings of birds got me to thinking about the state of birding in 2018. Before we get to those birds, I would like to muse on the changes in birding in my nearly 60 years as a birder.

As a kid growing up in the 1950’s, the best tool we birders had was either Roger Tory Peterson’s or Chan Robbins’ field guide. Binoculars were inexpensive and the quality of the optics matched the price.

Spotting scopes were not a part of my birding experience until 1975. Does anyone remember the Balscope? I bought my first scope, a Bushnell Spacemaster around 1978. What a difference that made, particularly with groups like shorebirds and ducks at a distance. Spotting scopes became a lucrative market for optics companies and current scopes provide astoundingly clear images. Scopes are now standard birding gear.

In the early 1970s, I discovered the LP record set, “Eastern Bird Songs”, based on recordings housed at the Cornell Laboratory of Ornithology. These recordings helped  many improve their aural identification of birds. The recordings did not capture the variability and diversity of the calls and songs of many birds.

Twenty years later, improved resources like the Birding by Ear series, sets of recordings by Lang Elliot, John Feith, Donald and Lillian Stokes, and others provided rich resources for improving our birding by ear. Now, most birding apps for your smartphone or tablet have multiple recordings of each species.

In my first two decades of birding, I saw few birders with cameras. Telephoto lenses were beyond the budget of many birders and the manual single-lens reflex (SLR) cameras of the day were less versatile than current models. Photographers shot either slide or print film so had to be economical in what pictures to shoot.

The arrival of digital point-and-shoot cameras was a game-changer. With optical zoom lenses able to zoom to 24 times or more, birders could take pretty decent pictures of birds with a tool that was reasonably affordable.

But to me, one of the greatest changes in birding over the past 25 years has been the arrival and continued improvement of digital SLR cameras. The shutter speed can be set fast enough to stop a bird in flight while lowering the aperture as much as possible to produce decent depth of field. The memory card can hold thousands of photos.

Many birders now go afield with a digital SLR and a 400-mm lens around their necks. With the auto-focus feature of digital SLRs, anyone can produce stunning photographs of birds.  We can shoot at a high enough resolution that even a bird occupying only a small part of a frame can be cropped to yield a crisp image.

Documentation of birds is so much easier now. It’s quite common to see many eBird reports now with embedded images to support the identification of unusual and even common birds.

Now to the re-sightings. In early August, a Great Black Hawk was sighted in Maine for a few days. A first record for Maine, the was photographed by many. A Great Black Hawk had been reported from south Texas in late April, where it too was extensively photographed.

Comparisons of the complex underwing feathers indicate a perfect match. The Texas bird and the Maine bird were one in the same.

The Roseate Spoonbill seen recently for over two weeks in Dover-Foxcroft finally departed. Photographs of the bird showed a puncture hole in the upper bill, likely courtesy of an egret or heron when the spoonbill was a nestling. Guess what, a Roseate Spoonbill appeared in coastal Connecticut on September 19. It has a puncture hole in the same place as our bird, another reoccurrence made possible by digital photography. Furthermore, the same bird was seen in early August in Walkill, New York.

Flying Ants and Aerial Insectivores

By in Foraging

I have been enjoying predictable but fascinating bird behavior in mid-August on the shores of Cobscook Bay in Lubec. Particularly in late afternoon, flocks of Bonaparte’s Gulls fly in large circles over the land adjacent to the water at heights of 50 to 100 feet or so. They are joined by Tree Swallows, Cliff Swallows and Barn Swallows.

The birds are in a feeding frenzy. But what are the birds eating? There are some dragonflies in the air, suitable for the gulls but not the smaller swallows. The food morsels of interest are flying ants.

Most ants in a colony are not reproductive. At times of the year, reproductive males (called drones) and reproductive females (queens) hatch with wings. They take to the air on nuptial flights, hoping to mate while airborne. If they do not become a meal for a bird, the queens will come back to earth, drop their wings and start a new colony or join an existing one.

The flight season for ants is short but provides largesse for birds that prey on flying insects. At a length of ¾ inch, a flying carpenter ant is a significant tidbit.

Swallows and other flying insectivores spend a good bit of their day in the air. This life style requires efficient flight.

Physics-savvy ornithologists have developed models to predict efficient flying speeds of birds. Field observations largely agree with the models.

The enemy of efficient flight is friction (drag in the parlance of physicists). Minimizing the friction of air or water passing over a moving object is important for race cars, Olympic swimmers and downhill skiers. This type of friction is called profile drag. It becomes increasingly costly the faster an object or person moves.

A less appreciated type of drag is called induced drag. For birds and airplanes, the shape of wings creates the upward force called lift that enables flight. However, air moving across the wing, particularly at the tips, becomes turbulent rather than smooth. These turbulent eddies increase friction and hence decrease flight efficiency. Unlike profile drag, induced drag decreases as flight speed increases.

Back to the swallows. These flying birds are on the horns of a dilemma. Flying fast minimizes induced drag but greatly increases profile drag. Flying slowly makes induced drag stronger but reduces profile drag.

What are birds to do? The flight models predict two solutions. One is to fly at a speed that maximizes the distance flown. This strategy is used by many migrating birds. The other viable solution is to fly at a speed that maximizes the time that can be spent aloft (fuel efficiency). This speed occurs where the sum of the induced drag and the profile drag are the smallest. That is what swallows and other flying insectivores do.

Our flying insectivores (nightjars, swifts, flycatchers, swallows) are the first of our breeding birds to depart in the fall. They need to leave before flying insect abundance declines as cool temperatures begin.

Sometimes, spectacular flocks of these birds can be seen. I’ve seen Tree Swallow flocks in the thousands in August. But a couple of memorable events for me involve Common Nighthawks. One August, I looked out our kitchen window in South China to see at least 500 migrating Common Nighthawks foraging over a hayfield. I had seen such a flock over 40 years ago in Baltimore at an Orioles game. I’m sure the lights of Memorial Stadium attracted flying insects that in turn provided food for the migrating nightjars.

We know more about Common Nighthawk migration now thanks to six GPS-fitted birds tracked by Peter Marra. The birds were tagged in western Canada, flew to Florida, then Cuba and on to Brazil for the winter. Their return flight did not follow the same route as the fall migration.

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