Vee Formations and Bird Migration

By in Behavior, Migration

Taking a walk around the neighborhood, I was treated to one of the great sounds of late fall, the honking of Canada Geese in flight. Looking up, I saw a small V of geese heading south. Have you ever wondered why these geese fly in V-shaped flocks? Such flight formations yield a significant savings of energy.

As a bird flies, eddies of air swirl off the tips of the wings. Some ornithologists began to wonder if trailing birds could take advantage of these upward eddies to gain lift. Using a computer model developed by aviation engineers, these ornithologists found that birds flying in V’s could realize an energy savings of 71%, compared to birds flying alone. The model showed that greatest benefit would result when a trailing bird has a wing overlap of about 5 inches with the next bird ahead. In other words, if a bird moved abreast to the next bird ahead of it, the wing of the trailing bird would overlap by five inches with the wing of the bird next in line. The model also showed that each bird except the leader should be between one and three yards behind the bird in front for greatest energy savings. Finally, the model shows that the birds in the flock should beat their wings in perfect synchrony.

Films of migrating Canada Geese were used see how well the positions of the geese agreed with the computer model. In many cases, the wing overlap was right around five inches, the most desirable position. Distance to the next bird and synchrony of flight were not always as predicted, probably because of turbulence in the air . Nevertheless, the performance of the geese suggested that an energy savings of 36% resulted from flying in V’s.

In a V of geese, the leader receives no benefit of the flight formation. Geese do switch positions so take turns as leader. The social status of the leader(s) has not been studied.

Canada Geese are not the only birds that fly in V-formations. Most geese species, including Snow Geese, fly in V’s. I’ve also seen Tundra Swans, White Pelicans, and Double-crested Cormorants flying in such formations.

Some ornithologists have begun to use microtechnology to better understand the behavior of birds flying in V’s. Henri Weimerkirsch fitted migrating pelicans with heart rate monitors. He found that pelicans toward the back of flight formations had lower heart rates, demonstrating the advantage of mooching lift off of birds flying ahead of you.

Stephen Portugal provides even more remarkable data. He fitted endangered Northern Bald Ibises with small data loggers that recorded the position of birds and their flapping rate several times a second. The data loggers have to be recovered to collect the data. The Northern Bald Ibises were the perfect species to overcome this challenge.

Portugal and others were trying to reintroduce this species into central Europe where they had been extirpated. Portugal’s team raised young birds and taught them the old migration route by leading them in a microlight airplane. At the end of each day’s migratory leg, the ibises were captured and their data loggers were read.

The data showed that the birds are bang on with theoretical predictions: the birds beat in synchrony and the distance behind and to the left or right of the next bird in the V conform to the predictions.

Some ibises prefer to be on the left side of the flock and others on the right. They do switch positions frequently and take turns being the leader.

When the migration was first begun, the ibises did not fly in a regular formation. No adults were present to teach them how to fly in a V. Nevertheless, they quickly discovered on their own the advantages of flying in a V.

[Originally published on November 11, 2015]

Common Eider

By in Reproduction, Species Accounts

The Common Eider is a common species of sea duck in northern coastal regions of North America, Europe and eastern Siberia. A common breeder in Maine, Common Eiders nest as far south as Massachusetts in New England. Common Eiders are important members of arctic breeding bird communities well to the north of us as well.

Common Eiders withdraw from their more northerly breeding areas after nesting and winter in coastal flocks. Winter aggregations may number in the thousands. In Maine, this species is present year-round.

Common Eiders are distinctive birds, often recognizable merely by their silhouette. The combination of a long, sloping bill (think ski jump), long neck and peaked head give them a distinctive look. At a length of two feet, Common Eiders are among our biggest ducks.

Adult drakes are subtly beautiful birds. The crown is black but the cheeks, neck and dorsal body are mostly white. A close look in favorable light reveals a light green wash on the posterior side of the face and nape. The mostly black wings contrast with the white sides when an eider is on the water. The bill is a dull yellow.

Like most ducks, the adult females are much less brightly marked. The body is barred with irregular dark and light brown stripes. The head is mostly brown.

First-year males are highly variable with brown heads like females but with splotches of white and brown on the dorsal surface. The breast is white.

Common Eider females make a nest on rocky islands, not far above the high tide mark. A female plucks down from her breast to line the nest. The down used to create soft, warm pillows, coats and sleeping bags often comes from eider down.

Harvesting eider down is typically done after the nesting season. A down collector simply gathers the down from the nest once the young eiders have hatched. However, synthetic insulating materials have been developed with comparable insulating properties to eider down. These synthetic products are relatively cheap to produce so an eider down-filled vest or coat will cost you a pretty penny compared to a product made from a synthetic material.

By the way, some down used for insulation comes from geese. That down has to be plucked directly from the geese. Goose down is inferior to eider down in insulating properties.

A hen eider may lay up to 14 eggs. When the ducklings hatch, they are covered with a down coat and leave the nest soon after hatching.

Once the ducklings have hatched, they aggregate into crèches of 100 birds or more. These eiders are watched over by the moms as well as non-breeding females.

The ducklings start to form their contour feathers in their second week and complete feather growth by seven weeks after hatching. They take their first flight nine or ten weeks after hatching.

Common Eiders dive in search of invertebrate food from the sea bottom. Mussels are one of the most common prey items taken although crabs and sea urchins are important components of their diet as well. An eider swallows a mussel whole, crushing the shell of the mussel in its powerful gizzard. For a crab, an eider removes the legs first and then swallows the de-legged crab for crushing in the gizzard.

The fondness of Common Eiders for mussels poses a challenge for mussel mariculture. Not surprisingly, the dense aggregation of mussels attracts eiders. Nets seem to be the only practical way to protect the mussels from the eiders and other sea ducks.

Common Eiders are doing well now with an estimated population of two million birds in North America and Europe. Our New England population was nearly decimated by market hunters by the end of the 19th century. Fortunately, the eiders have recovered.

[Originally published on October 18, 2015]

 

Navigational Cues during Bird Migration

By in Migration, Weather

Let’s consider the wonder of bird migration today starting with a shorebird. During the summer, Semipalmated Sandpipers breed on the arctic tundra all across North America. As precocial birds, the Semipalmated Sandpiper chicks hatch fully feathered and can find their own food soon after hatching. The parents provide some protection from predators for the young birds but the chicks largely feed themselves. In July before the chicks can even fly, the adults depart the tundra to work their way to their wintering areas near the mouth of the Amazon River in South America. Once the chicks learn to fly, they depart a few weeks later to fly to an area where they have never been.

Semipalmated Sandpipers and other shorebirds are not the only birds whose young find their way unaided to wintering areas. Young-of-the year Magnolia Warblers find their way to Central America, Kirtland’s Warblers to the Bahamas and Swainson’s Hawks to Argentina. Geese and cranes are among the minority of birds that lead their young to wintering grounds. Most birds have their migration genetically encoded.

These internal maps are often amazingly precise. It is not unusual for a songbird over the course of its lifetime to use the same breeding territory in Maine and spend the winter in the same wooded area in Mexico. Clearly, birds have marvelous navigational abilities. How do they do it?

The sun is an obvious guide for navigation. Captive European Starlings become restless as the time for migration approaches. These birds attempt to fly from the cage in a particular direction, corresponding to their known migration direction. On cloudy days when the sun is obscured, the birds do not orient in the proper direction.

Most songbirds migrate at night so the sun is not a visible cue during their migratory legs. However, some night-migrating songbirds use a sun-compass by judging the proper direction of migration as the sun is setting and then remembering that direction when they begin their migration in the darkness.

Some migrant birds navigate using the stars. Captive songbirds that are ready to migrate orient in the proper direction on cloudless nights but move randomly when clouds block out the brighter stars. Some interesting experiments have been conducted in a planetarium. Birds inside the planetarium orient in particular directions based on the patterns of the stars. When the map of the stars is rotated so that north and south are reversed, the birds orient in the right direction as indicated by the stars but the wrong direction as indicated by the earth’s magnetic field. Some of our local birds that are known to use the stars to guide their way are Black-billed Cuckoos, Rose-breasted Grosbeaks and Bobolinks.

The earth’s magnetic field can be used to navigate by some migrating birds. Early experiments with pigeons showed that placing small magnets on the pigeons’ necks interfered with their ability to orient properly. More sophisticated experiments have been recently done where birds are fitted with small helmets which reverse the direction of the magnetic field around the bird. The north pole of the experimental magnetic field around these birds is actually south and the apparent south pole is north. As expected, the experimental birds orient in exactly the opposite direction.

Some birds that migrate during the day use visible landmarks for navigation. Hawks and Hawk and eagles may follow mountain ridges. Some landbirds may follow the coastline.

Finally, some birds actually use their sense of smell to find their way. Homing pigeons with their nostrils plugged with cotton are not able to find their homes as well as pigeons without plugged nostrils. Some seabirds like the Leach’s Storm-Petrel locate their nest burrows by smell.

As many of our birds leave us until the spring, we can thankful these birds can navigate so well. We know we will see many of them again next spring.

[Originally published on October 4, 2015]

Bird Banding

By in Banding, Migration Tags:

We are in the middle of one of the great ornithological spectacles of the year, the fall migration. It’s fun to track the appearance and disappearance of migratory species as they traverse the continent. We can learn much by our collective observations of the pace and route of bird migration at the species level.

But ornithologists are also interested in populations (isolated groups of one species) of birds. As an example, do Black-throated Green Warblers breeding in Maine overwinter in the same tropical areas as the Black-throated Green Warblers nesting in Michigan or in the Great Smokies? And what are the migratory pathways for these populations starting from different longitudes? To answer these questions, individuals have to be identified. A tried and true method is bird banding.

The Bird Banding Lab (henceforth, BBL), a federal agency in the U. S. Geological Survey, coordinates banding activities of native North American birds. To band native birds, one must obtain a Master Bander Permit, possible only after extensive experience in assisting a licensed bander. The BBL provides banders with aluminum bands, each with a unique, nine-digit number. The bander captures birds either in mist-nets or traps and fits the bird with a numbered band using special banding pliers. The banding process can be done quite quickly, minimizing the stress to the captured bird.

The bander sends the BBL records for all birds banded, including age and sex. The banded bird thus provides a record that a particular bird was at a particular place at a particular time. But the real value of banding comes when a banded bird is recovered. Sometimes banded birds are found dead while others are captured by banders at a different banding station.

The re-encountered bird is reported to the BBL workers who close the loop, letting the finder know where the bird was banded and letting the original bander know where the bird was re-encountered.

The power of bird banding relies on the re-encounter of banded birds. As you might imagine, the odds of re-encountering many species of birds are pretty slim. As an example, 745,000 Purple Finches have been banded in the United States and Canada but only about 20,000 have ever been re-encountered (2.7%). As a scientific tool, banding requires that many individuals be banded.

The band numbers for most bands are too small to be read through binoculars (as if a bird would hold still for you to read its digits!) so most birds must be recaptured to determine their unique band number. However, the numbers of bands on large birds like swans can sometimes be read with a spotting scope, obviating recapture of the bird to discover its identity.

Here are a few of the ornithological discoveries that have been made possible by banding birds. Arctic Terns are known to migrate from pole to pole, twice a year. We have learned much about where different populations of birds winter. For instance, Palm Warblers do an interesting crisscross in migration. Populations breeding in the upper Midwest and Prairie Provinces migrate southeast to winter in Florida while our eastern Palm Warblers migrate southwestward to winter along the Gulf Coast.

Re-encountered birds provide us with information on the longevity of birds.  Recently, a Ring-billed Gull that had been banded 53 years earlier was found alive, blowing away the previous longevity record.

Some banding records can cause your jaw to drop. For instance, a Semipalmated Sandpiper banded in Nova Scotia was recaptured four days later at the mouth of the Amazon in South America. The bird had flown 2800 miles, non-stop, over the Atlantic Ocean in just 96 hours!

John James Audubon was the first bird bander in North America. He tied some aluminum wire to some nestling Eastern Phoebes in Pennsylvania and found that the birds returned the following year to nest.

[First published on September 20,2015]

Fruits from Invasive versus Native Plants: Which do Birds Prefer?

By in Foraging, Migration

The fall migration is well underway. Swallows are scarcer than hen’s teeth now in Maine. We will bid adieu to most warblers and vireos this month.

Migration is a tremendously expensive and arduous undertaking for a bird. As warm-blooded vertebrates, birds have a high metabolic rate. Smaller birds have a tougher time of it than larger birds. On a per gram basis, it is much more expensive to be a hummingbird than a robin.

To complete a migratory journey, birds require predictabl food all along the way. Many migratory songbirds rely on fruits to help meet their fueling requirements. Before Europeans settled in North America, migratory songbirds took advantage of fruits like winterberries, pin cherries, mountain ash fruits.

The relationship between the fruit-bearing plants and the fruit-eating birds benefits both parties. The birds disperse the seeds of the plants in return for a bit of nutritious fruit.

Human colonization has resulted in both the intentional and accidental introduction of exotic plants. I am writing this column in Lubec and I can look out the window and see large banks of the invasive Japanese knotweed across the way. Bittersweet, Japanese barberry, Tartarian honeysuckle, Morrow honeysuckle, autumn olives, multiflora rose and two species of buckthorns are other well-established invasive plants in our state.

Invasive plants often outcompete native plants. An invasive plant is usually free of herbivores and pathogens that it has to contend with in its native habitats. Such ecological release is a huge advantage in competing with native plants with their own herbivores and pathogens.

We know that invasive plants are causing reductions in the abundance of native fruit-bearing plants. What implications do these changes have for migratory birds?

Brie Drummond addressed this question for her Honor’s thesis at Colby College in 2003 and published her work in the Northeastern Naturalist in 2005. She studied two representative introduced plants, Tartarian honeysuckle and multiflora rose and two native plants, a viburnum species and silky dogwood.

She found that the fruits of the honeysuckle and dogwood degrade quickly. All were either eaten or rotted by the end of November. The rose and viburnum fruits persisted into the winter, offering wintering birds (primarily waxwings and American Robins) some sustenance.

Brie measured the energetic content of each of the four types of fruits using an instrument called a bomb calorimeter. The fruits of the two native species had higher caloric content than the two invasive species. However, choice experiments with the rose and viburnum fruits showed that birds did not show a preference between the two fruits. Perhaps, Brie thought, birds are selecting fruits based on carbohydrate or fat content rather than total energy content. Digestibility of the fruits may play a role as well.

Susan Smith and colleagues at the Rochester Institute of Technology did a more detailed analysis of fruit quality. They published their work in 2013 in the Northeastern Naturalist. These researchers examined five native plants: three species of dogwoods, arrowwood viburnum and spicebush. In addition to the invasive plants studied by Brie, the RIT team examined buckthorn fruits.

The researchers determined total energy content and fat content of each type of fruit. They found that the caloric content of native plants was slightly higher than the caloric content of the invasives. However, striking differences in fat content emerged. No invasive fruits had higher than 1% fat content while the fat content of native fruits ranged from 6% to 48%.

Migrating birds primarily use fat to fuel their migration. Fats are more energy-dense than carbohydrates or proteins so a gram of fat provides more energy to a migrating bird. One would predict that fall fruit-eating birds would prefer the native fruits.

Smith and colleagues measured preferences of fall migrants and found results that fit their predictions: fall frugivorous birds prefer native dogwood fruits to the fruits of the four invasive species.

[Originally published on September 6, 2015]

Breeding Bird Survey – II; Merlin App; Bald Eagle Longevity Record

By in Bird Conservation, Conservation, Software Tags:

In the last post, I wrote about the history of the Breeding Bird Survey on the occasion of its 60th year. The BBS has been a treasure trove of information for ecologists, ornithologists, conservation biologists and environmental managers interested in the changing populations of birds.

I recently did a search for “Breeding Bird Survey” using a database of scientific articles. The search yielded 523 papers!

Analyzing BBS data poses challenges because of the nature of the data collection. The surveys are done by thousands of observers with different degrees of skill in identifying birds by sight and sound.

Ideally, a particular BBS route is conducted by the same observer for decades. But a recent journal article describes a bias that may occur even in these ideal situations. Robert Farmer and colleagues analyzed BBS data as well as data from the Ontario Breeding Bird Atlas project and showed that older birders detected fewer birds by ear than younger birds. The effect was greatest for bird sounds with high-pitched frequencies but other species with lower-pitched calls and songs were missed more frequently by older observers.

You can see the potential bias for a route that has been conducted by the same individual for 30 years. A decrease in bird abundance in later years may indicate poor detection by the aging birder rather than a real decline in abundance.

I have done nearly 100 BBS counts over the past 25 years. This year, I have noticed decreased ability to hear Cedar Waxwings and other high-pitched species. Reluctantly but rightly, I will give up my BBS routes.

In Maine, 70 BBS routes have been established. Currently, only 36 of these routes are active. In contrast, all of the 23 BBS routes in New Hampshire are claimed and all but four of the 23 routes in Vermont are claimed.

We need better coverage of the Maine BBS routes. Some of the routes are in the northwestern part of the state, requiring considerable travel to be at the starting point before sunrise. But there are many vacant routes in southern and eastern Maine that may be convenient to your home.

You can see a map of the vacant routes at: https://www.pwrc.usgs.gov/bbS/RouteMap/Map.cfm If you feel confident in identification of Maine birds by sound and sight, I hope you will consider adopting a BBS route. For more information, please contact Maurry Mills at [email protected]

Maurry is based at the Moosehorn National Wildlife Refuge and is the Maine BBS coordinator.

 

Merlin App

The Cornell Institute of Ornithology is developing software called Merlin that identifies birds based on a digital photograph. The software is currently in beta testing and the developers are enlisting the help of birders. Go to: http://merlin.allaboutbirds.org/photo-id and then upload a photograph of a bird. You will be asked to provide the location where the bird was photographed as well as the date of the sighting. Then, you draw a box around the bird and indicate the bill tip, eye and tail tip with a mouse click. Hit Next and Merlin will provide possible matches.

I uploaded a photograph of a Greater Yellowlegs and Merlin nailed the identification. Currently, Merlin gives the correct identification 90% of time in its three top suggestions. Uploading photographs essentially trains Merlin to be even better with identification. Eventually, this recognition software will be available for tablets and smartphones but is currently only available through a browser.

 

Oldest Bald Eagle

In June, a banded Bald Eagle was killed in upstate New York by an automobile. The bird was banded in 1977 in Minnesota. The bird was translocated to New York state in 1981 as part of New York’s Bald Eagle restoration program.

This male bird nested around Hemlock Lake and fathered many eaglets over the years. Even though this bird died prematurely from the automobile collision, its 38 years of age shattered the former longevity record for Bald Eagles by five years.

[Originally published on August 23, 2015]

Breeding Bird Survey – I

By in Bird Conservation, Conservation Tags:

In 1966, the first Breeding Bird Surveys were conducted under the auspices of the United States Fish and Wildlife Service and the Canadian Wildlife Service. With the conclusion of surveys last month, the program has now contributed 60 years of data on the dynamics of the breeding birds of North America.

The idea for the survey was the brainchild of Chandler Robbins. You may recognize Chan’s name as the primary author of the 1966 Golden Guide, The Birds of North America.

The basic protocol of a Breeding Bird Survey (hereafter, BBS) involves conducting a bird census along 24.5 miles of secondary roads. Beginning about a half-hour before sunrise during the peak of the breeding season (May into early July depending upon latitude), an observer starts at the fixed first stop of the route. For three minutes, s/he counts all the birds heard or seen in three minutes. The observer then drives 0.5 mile to the next stop, counts for three minutes, continues to the next stop, counts and so on until 50 stops have been sampled. It generally requires about 4.5 hours to complete a route. The majority of birds recorded are heard and not seen.

The observer uploads the bird abundance at each station to the BBS website along with data on temperature, wind and cloud cover.

The following year, the observer repeats the route, stopping at precisely the same 50 stations each year. It’s easy to locate stops precisely with GPS devices now. Before GPS, stops had to be described like “50 feet before a large big-toothed aspen on the right side of the road”.

The routes are assigned by the USFWS or CWS. The roads chosen are generally on less traveled roads. As you can imagine, traffic noise makes it very hard to hear singing birds.

Of course, a single survey is of limited use in detecting population changes. The power of the BBS lies in the fact that thousands of surveys are run each year. Initially, 600 routes were established, all east of the Mississippi River. The program quickly expanded to western North America, reaching 2000 routes by 1968. The program continued to grow and now there are nearly 3700 routes in the United States and southern Canada.

Analyzing BBS data presents a challenge because of many confounding factors like differences among observers in identification skills, visual and auditory acuity and weather. Biologists do not claim the data can be used to determine actual abundances of each species but rather offer a way to compare abundances from year to year (relative abundances). The development of maps showing population changes is one of the strengths of the BBS (you can explore these maps at https://www.pwrc.usgs.gov/bbs/).

The BBS data are available to anyone and hundreds of ornithologists and conservation biologists have used the data as the basis of scientific papers. One landmark paper based on BBS data was authored by Chan Robbins and colleagues in the Proceedings of the National Academy of Sciences in 1989.

In this paper, the authors studied the changes in relative abundance of eastern breeding birds from 1966 until 1987. They showed that a striking decline in the abundance of North American breeding birds that overwinter in the New World tropics occurred from 1978 to 1987 after a period of stable populations from 1966 to 1977. Most permanent residents and short-distance migratory species did not show such declines. The data therefore strongly suggest that changes on the wintering grounds such as deforestation were driving these declines of long-distance migrants.

The BBS continues to be one of the most powerful tools we have to gauge changes in bird populations. But the BBS is not the singular accomplishment by Chan Robbins. He worked on impacts of DDT on birds, influencing Rachel Carson to write Silent Spring in 1964. He retired in 2005 after 60 years with the USFWS!

[Originally published on August 9, 2015]

Wyoming Trip – II

By in Trip Report

This post concludes the description of a trip my wife and I took to northwestern Wyoming in the first week of July.  Today, I’ll discuss our visits to two National Parks.

On July 2, we drove north from Jackson to the south entrance of Yellowstone National Park.  This national park, encompassing an area of over 3,400 square miles, was signed into law by President U.S. Grant in 1872.  Yellowstone is regarded as the first wildlife park ever created.

Bets and I had never visited Yellowstone before so we were anxious to broadly sample the amazing biological and geological wonders in the park. We drove north for about 20 miles to the Visitor Center at Grant Village. The rangers monitor the eruptions of Old Faithful and post information on the timing of the next eruption..  The next one was predicted around 11 AM. We had 45 minutes to drive the 17 miles to this famous geyser. We arrived about 10 minutes before Old Faithful erupted and it was a particularly large eruption.

Old Faithful is just one of 300 geysers in Yellowstone.  Hot springs, pools and ponds abound on the western side of park. We drove north from Old Faithful with steam rising all along the road between Old Faithful and Madison.

The density of geysers was dwarfed by the density of automobiles.  This stretch of Yellowstone attracts many tourists.  We quickly realized birding was going to be next to impossible along the busy road.

We did take a short loop, Firehole Lake Drive, that provided some opportunities for birding. We stopped at a hot spring with water actually boiling. We learned that trappers used to cook their meat or fish by simply immersing it into one of those boiling springs.

While we were admiring the spring, we heard a Red Crossbill giving its jip-jip flight call overhead. A little further down the road, we found Killdeer, Mountain Bluebirds and White-crowned Sparrows. We saw a raptor through the trees and ultimately got a nice look at an adult Golden Eagle.

We decided to head south in search of better birding opportunities. Along the way, a male bison was fairly close to the road, affording us great looks at this magnificent species.

Exiting Yellowstone and entering Grand Teton National Park, we stopped at the Oxbow Bend Turnout. The highlight for us was a great look at four White Pelicans. We also found 120 Canada Geese, a Mallard, three Common Mergansers and four Double-crested Cormorants. Many Violet-green Swallows were hawking insects above us.

Just a few miles south on Highway 89, we stopped at the Elk Ranch Flats Turnout. Several hundred bison were there with quite a few new-born calves. We also saw a dozen Pronghorns. Savannah Sparrows and Western Meadowlarks were singing. A nice way to end a great day with nature.

On July 3, we explored the southern portion of Grant Teton National Park. From Teton Village, we entered the park at the Granite Canyon entrance and drove northward toward the Visitors Center in Moose. This road is not heavily traveled and pull-outs are present so stopping for birds is possible.

New additions to our trip list included White-breasted Nuthatch, House Wren, Wilson’s Warbler and Common Yellowthroat.

We stopped at the new Visitors Center in Moose.  This center is fantastic.  We really enjoyed the informative 25-minute film on the biology, geology and history of the Teton range.

We continued our expedition to Jenny Lake. We took a shuttle boat across the lake to the trailhead for Hidden Falls. The half-mile trail involves a bit of effort and elevational gain but the beauty of the falls is worth the effort. The mist from the falls provided welcome cooling.

Our bird list included Osprey, Ruby-crowned Kinglet, Swainson’s Thrush, Cedar Waxwing, MacGillivray’s Warbler, Yellow-rumped Warbler, Western Tanager, Chipping Sparrow, Dark-eyed Junco and Cassin’s Finch.

[Originally published on July 26, 2015]

Wyoming Bird Trip – I

By in Trip Report

My wife and I recently had the pleasure of a short trip to the Jackson Hole area in northwestern Wyoming. The town of Jackson is the jumping-off point for two of the crown jewels of the National Park System: Yellowstone National Park and Grant Teton National Park.

Jackson Hole is the relatively flat valley between the Teton Mountains and the Snake River. Access to the valley requires descending fairly steep slopes, giving early trappers the sensation of entering a hole. Jackson Hole is about 6,000 feet above sea level.

Arriving late on June 30, we opted to explore the local area around Jackson on July 1. We began by driving east from our hotel in Teton Village to the Wilson area. Brewer’s Blackbirds were common. Violet-Green Swallows were the most abundant of the four swallows we saw, the others being Tree, Barn and Cliff Swallows. Black-billed Magpies were delightful to see.

Heading east on Fall Creek Road in Wilson, we saw several Ospreys, most nesting atop power poles. A Sandhill Crane was foraging in a marsh adjacent to Fish Creek. Wooded areas produced Northern Flickers (the red-shafted form), Western Wood-Pewees, Ruby-crowned Kinglets, abundant Yellow Warblers and White-crowned Sparrows. Fish Creek produced a Wood Duck, a pair of Green-winged Teal and a Bald Eagle.

We headed south on Route 22 to the Teton Pass at an elevation of 8,431 feet. A lovely trail right at the peak of the pass winds through some coniferous forest before opening up into an alpine meadow with a mosaic of colors. The flowers along the trail were truly stunning.

In the firs, Cassin Finches sang their Purple Finch-like songs. Dark-eyed Juncos were common and we saw a Chipping Sparrow as well. A couple of American Robins and quite a few Pine Siskins were present.

We heard a song that sounded like an Indigo Bunting. Perched in the top of a tree was a Lazuli Bunting, a species that gives the Indigo Bunting a run for its money in terms of beauty.

The abundance of Common Ravens fit the name with a few American Crows present as well. From the forest below, we heard the “quick three beers” call of an Olive-sided Flycatcher.

The trail crested at a small stand of spruce and fir with a few standing dead trees present. These trees had a pair of Mountain Bluebirds and a male Western Tanager. Rather than retracing our steps to the parking lot, we opted to follow a Forest Service road back to our car. Along the way, a Western Kingbird appeared. A Hermit Thrush favored us with its flute-like song and a Red-tailed Hawk screamed unseen.

We then drove north on Route 22 back toward Jackson. We stopped at a small pond (Skyline Pond) on the east side of the road. This marshy pond had Mallards, Gadwall, a Redhead and an American Coot with many chicks swimming around her. Marsh Wrens and Red-winged Blackbirds sang from the cattails.

After a lunch in Jackson, we drove north on Route 89. Just beyond the town proper, a pullout on the east side of the road affords an excellent view of the National Elk Refuge. In the fall, hundreds of elk descend from the mountains to this area to winter and feed on the grasses. No elk were present while we there but many birds were present in the marsh adjacent to the grassland. We found Gadwall, Ring-necked Ducks, Canada Geese and a pair of Trumpeter Swans. The presence of a Belted Kingfisher was given away by its loud rattle-like call. Yellow-headed Blackbirds were common.

We spent most of the rest of the afternoon exploring the sagebrush flats north of Jackson. Our list included American Kestrel, Mourning Dove, Eurasian Collared-Dove, Sage Thrasher, Vesper Sparrow, Brewer’s Sparrow and Green-tailed Towhee.

On to Yellowstone and Grand Teton National Parks in the next post.

[Originally published on July 12, 2015

Hybridization of Sparrows in Maine Salt Marshes

By in Hybrids, Reproduction

Hybridization is the process of crossing individuals from genetically distinctive groups. In most cases, those distinctive groups are considered separate species.

Hybridization occurs widely in the natural world and birds are no exception. Some authors claim that at least 10% of the world’s 11,000 species form hybrids with other closely related species.

In Maine, Mallards frequently mate with American Black Ducks. In fact, wildlife biologists are worried that the frequency of hybrids may eliminate the American Black Duck as we know it. Mallards are much more common than American Black Ducks. Hybrid pairings represent only a small fraction of all Mallard matings but a more significant fraction for the rare American Black Duck. This process, called genetic introgression, means that American Black Ducks are accumulating Mallard genetic material as time goes on.

Mallard-black duck hybrids are hardly the only duck hybrids. Ducks are notorious for hybridization, sometimes producing baffling individuals whose provenance is unclear. Hybrids I have had the pleasure to see in the wild include Barrow’s Goldeneye x Common Goldeneye, Greater Scaup x Tufted Duck, American Wigeon x Eurasian Wigeon and Mallard x Northern Pintail.

Some bird hybrids occur frequently enough that they have been given names. For some of these named hybrids, early ornithologists thought they were separate species and described them as such. Later work indicated they were actually hybrids of two related species. Thus, we have Brewster’s Warbler, a hybrid between a Blue-winged Warbler and Golden-winged Warbler along with the rarer Lawrence’s Warbler (one parent is usually a Brewster’s Warbler!).

Nelson’s Gull was originally described in 1884 as a new species. We now know that it is actually a hybrid between a Glaucous Gull and a Herring Gull.

Viable hybrids represent flies in the ointment as we try to understand species limits. Many biologists (and most members of the American Ornithologists Union Check-list Committee, the arbiter of the North American species list) subscribe to the biological species concept, first developed by Ernst Mayr in 1951. Mayr defined a species as a group of interbreeding individuals that are reproductively isolated from all other groups. In birds, reproductive isolation can occur by differences in plumage, differences in vocalization or differences in courtship behavior.

If Mallard and American Black Ducks can interbreed to produce fertile offspring, should they not be considered a single species? It’s a thorny issue but the upshot is that occasional hybridization is tolerated before two hybridizing species are considered one.

A recent paper by Jennifer Walsh and colleagues in the Auk explores an intriguing hybrid zone in salt marshes in Maine.  Field guides from 20 years ago or older had an entry for the Sharp-tailed Sparrow with a breeding range along the eastern seaboard from Virginia to Nova Scotia. In 1995, this species was split into two species: the more southerly Salt Marsh Sparrow and the more northerly Nelson’s Sparrow.  The two species can be distinguished morphologically.  The Salt Marsh Sparrow has more distinct dark streaking on the breast and flanks and has a bright orange cheek patch.  The Salt Marsh Sparrow is slightly bigger with a longer, thinner bill.

One of the birding attractions of Scarborough Marsh is that both of these sparrow species nest together.  We also know that hybrids of the two species occur here.

Walsh and colleagues sampled sparrows in 34 marshes from the North Shore of Massachusetts to Washington County, Maine.  At each site, they captured sparrows, took various measurements and drew a blood sample for DNA analysis.

Most of the Massachusetts marshes had only Salt Marsh Sparrows and the Penobscot Bay to Washington County sites had only Nelson’s Sparrows. In between however, hybrids occurred.  DNA comparisons showed that 52% of individuals in the hybrid zone had mixed ancestry.  However, because of the complicated crossing and backcrossing of individuals, pure and hybrid birds cannot be distinguished on the basis of morphology.  Hybrids are rampant but can only be discerned by genetic analysis.

 

[Originally published on June 28, 2015]

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