Sunday, September 29, 2013

Nashville Warbler

A Nashville Warbler on its way after picking up a band at our banding station—you can tell by its yellow throat, white eye-ring, and barely visible white belly. This month continues to be exceptionally poor at the banding nets. Has the weather just been too good this fall for migrants to make landfall in Northfield? Did the breeding season fail in the north woods? Are this year's birds just too smart to be caught in my nets? (My nets were open about equal hours in both years.)

Here is a quick, unofficial, comparison of small birds banded at Northfield and Dundas in September 2013 and September 2012. (Please excuse the list not being in taxonomic or alphabetical order.)

September 2013 (total= 41)          September 2012 (total=140)
2 Black-and-White Warbler          17 Yellow-rumped Warbler
8 Black-capped Chickadee            19 Nashville Warbler
1 American Goldfinch                  9 Tennessee Warbler
1 Tennessee Warbler                    3 American Redstart
2 Nashville Warbler                     9 Chestnut-sided Warbler
2 American Redstart                    1 American Redstart
1 Chestnut-sided Warbler             3 Red-breasted Nuthatch
1 Golden-winged Warbler            2 Black-throated Green Warbler
1 Wilson’s Warbler                     1 Wilson’s Warbler
1 Yellow-bellied Flycatcher         1 Philadelphia Vireo
1 Common Yellowthroat             1 Magnolia Warbler
2 House Wren                            12 Red-eyed Vireo
7 Swainson’s Thrush                   7 Ovenbird
1 Downy Woodpecker                 2 Blue-headed Vireo
1 Gray-cheeked Thrush               3 Bay-breasted Warbler
5 Northern Cardinal                    1 Wilson’s Warbler
2 Ovenbird                                 1 Black-throated Blue Warbler
1 Red-eyed Vireo                        4 Canada Warbler
1 Indigo Bunting                         1 Common Yellowthroat
                                                 3 Black-capped Chickadee
                                                 1 American Goldfinch
                                                 1 Black-and-White Warbler
                                                 1 Blackburnian Warbler
                                                 1 Golden-winged Warbler
                                                 1 Wood Thrush
                                                 4 Gray Catbird
                                                 5 Northern Cardinal
                                                 1 Scarlet Tanager
                                                 1 Gray-cheeked Thrush
                                                 9 Swainson’s Thrush
                                                 2 White-breasted Nuthatch
                                                 21 American Robin
                                                 1 Red-headed Woodpecker

Saturday, September 28, 2013

Caspian vs. Royal Tern

I find Caspian Terns (below) and Royal Terns (above) to be tricky to tell apart. One field mark is the bill color: orange-red in the Royal, dark red in the Caspian. The trouble is that the Caspian’s bill color can vary, especially with different lighting and depending on the bird’s age. Note the dark tip on the Caspian Tern’s bill. The crowns often distinguish the two. Royal crowns tend to be white with a narrow black band across the sides of the face. Even as juvenals, Caspian Terns do not have as much white in the crown. Breeding Royal Terns, however, have black crowns.
The situation is less confusing in North America's interior, where only Caspian Terns are normally encountered (either as breeding birds or as migrants). Royal Terns almost never stray inland, keeping instead to the coasts of the Atlantic, Gulf of Mexico, Gulf of California and southern California. The Royal Tern in this blog was photographed on Florida's Atlantic Coast; the Caspian was in costal Texas.

Friday, September 27, 2013

Ebony Jewelwing

This male Ebony Jewelwing is proclaiming his territory and trying to attract females (which have white spots on their fore-wings) by opening and closing his wings.  Males often also make courtship flights. Males guard the females with whom they have mated. Keeping track of their females may be difficult, because, according to Dubois, females are “blatantly promiscuous, mating up to five times a day and rarely with the same male."

Thursday, September 26, 2013

American Goldfinch and Black-headed Siskin

John Holden and I birded near the visitor center at Faribault's River Bend Nature Center on 25 September 2013. The morning was cloudless and 60 degrees F. A flock of American Goldfinches fed at a feeder and perched on the brick building. Other goldfinches flew up, some landing on the bricks; others appeared to try to displace the perched bird. 

This behavior seemed curious, since plenty of small trees and shrubbery stood nearby. The goldfinch does not appear to be in peak health—its eyes are partially closed and its plumage appears worn and fluffed out.  On the other hand, possibly this bird and the others were sunning, a feather-maintance behavior that I have described in a recent post about robins. When this bird finally flew, its flight appeared to be normal.

Years ago, as a teenager in Chiapas, Mexico, I witnessed similar perching behavior with a Black-headed Siskin. I searched my photo files, and found the fuzzy picture below. These siskins are in the same genus as goldfinches, and are common in Mexico south to Guatemala. I wonder if both the siskin and the goldfinch used the warm bricks to rid their feathers of various parasites.

Wednesday, September 25, 2013

Swainson’s Thrush

I have often blogged about this common migrant—the Swainson’s Thrush. A link to a few of these posts can be found here. None of my previous photos show this thrush’s mustaches quite so comically. This species winters from Mexico through northern South America. A bird I banded on 19 May 1985 in Aberdeen, South Dakota, was recovered in Guatemala on 11 April 1988.

Tuesday, September 24, 2013

Saffron-winged Meadowhawk

Saffron-winged Meadowhawks are among the last meadowhawks to appear, emerging from June through October. These photos show their ovipositing in tandem over shallow water in the Straight River at the River Bend Nature Center on 13 September 2013. To guard their mates from the attentions of others, the males attach themselves to the females' necks. As you can see in the lower photo, pairs often attract other couples, “until there can be quite a crowd” (King). The female repeatedly dips her abdomen into the water, sometimes a half-dozen times, before the pair move along the shore. (The algae-covered rocks in the lower photo are all under water.)

Males can be difficult to identify, but the female’s saffron veined wings “seem to glow in the right light" (Mead). Note the female’s yellow spots (stigma) at the end of her wings. Last year I posted closeup photos of both sexes of Saffron-winged Meadowhawks.

Monday, September 23, 2013

Cape May Warbler

Cape May Warblers breed in boreal coniferous forests across Canada, dipping down to northern Minnesota, Wisconsin, Michigan and northern-most New England. They winter in the West Indies and in Central America. Alexander Wilson described this species from a specimen taken in Cape May, New Jersey. The bird was not seen there again for more than 100 years (Baltz and Latta 1998).

Over the years, I have seen Cape May Warblers numerous times, but never with a camera in my hand. The exception is this female bird I found near the Missouri River in South Dakota. The breast streaks and the yellowish color surrounding the cheek patches are the keys to identification. I have banded several fall-plumaged birds at my home in Northfield, but inexplicably I never photographed them. Surely I won’t repeat this lapse if ever I catch one of the gaudy plumaged spring males.

One problem when searching for Cape May Warblers is that this bird is a spruce budworm specialist. This warbler’s numbers explode when budworms are numerous. Between budworm outbreaks, Cape May Warblers may become extremely rare or even absent. Baltz and Latta (1998) report that the Cape May "has has a larger average clutch size than most wood-warblers [—six eggs—] which may enable it to increase rapidly during such short-term resource bonanzas.”

Saturday, September 21, 2013

Wilson’s Warbler

Wilson’s Warblers, like the male I banded last week, are relatively easy to identify. Females are also fairly simple, although they are somewhat similar to a female Hooded Warbler. Female Wilson’s Warblers differ from Hoodeds in that the sides of Wilson’s faces are brighter and show more contrast with the rest of the head and Hooded Warblers show white in the tail, which is absent in the Wilson’s.

Some birders are not aware that many female Wilson’s Warblers sport black crowns. Only females in their first fall and winter lack any black in the crown. When present, the female’s black crown averages smaller than in the male. We banders measure the extent of the black crowns when we catch Wilson’s Warblers. Only birds with crowns longer than 15 mm can be safely sexed as males.

Friday, September 20, 2013

Dragonfly Eyes

The identity of this female meadowhawk eludes me. I suspect it is a White-faced, one of a trio of dragonfly species called “the troublesome three,” the females often being impossible to identify in the field (King). This photo shows dragonfly eyes.

The eyes are compound, consisting of some 28,000 photoreceptors, each with its own lens and nerve. Dragonflies can see in every direction at once, but see best where their receptors are densest. These clusters, called pseudo-pupils, are often dark. On their crowns, dragonflies also have several simple eyes that do not percieve images, but are sensitive to sudden changes in light or shadow (Taylor).

Scott King comments: "this is one place that Taylor got the facts wrong. The dorsal portion of the eye, a characteristic of many skimmers, and seen in your photograph as the maroon area on the top of the compound eye and more sensitive to short wavelengths of light, a specialization for locating prey against the blue sky. The pseudo-pupils has to do with the angle at which we are viewing the ommatidia, not their density."

Thursday, September 19, 2013

Dark-form White-faced Meadowhawk

I found this meadowhawk to be perplexing to identify. This dragonfly lacked the yellow legs of an Autumn Meadowhawk and the white face of a White-faced Meadowhawk. Nothing in my books matched. Turns out to be a dark-form, female White-faced Meadowhawk. I have seen several more in this phase since Scott King helped me with this identification.

Female White-faced Meadowhawks, then, are found in three forms. The “normal” one with which I was familiar is a yellowish dragonfly. This form is in the photo below, the lower animal in a wheel formation with a red male. (I have discussed dragonfly sex in a previous blog.) Female White-faced Meadowhawks also appear as andromorphs, pale versions of their males—I blogged about andromorphs last month. You would think selective pressure would produce a single version of the females so that the males might have little trouble with recognition. Looking somewhat like a male might have advantages if the females are often harassed by males. Looking dark and nondescript might help a female avoid predation.

Tuesday, September 17, 2013

Bird Quiz

John worried about exams at Tallman Bird University. I replied that I would give him a tuition break and no exams. Pop-quizes, however, like this bird we found in the banding net this morning, are another matter (and gave me time to consider my identification). John did well.

“First of all, it has a seed-eater’s bill,” reasoned John.

“Clearly its young,” he continued, already assuring himself a passing grade.

“Look at the faint breast streaking and the white throat,” he said, nailing the field marks of an immature (and probably female) Indigo Bunting.

This bird lacked any trace of blue. See my blogs of  24 June 2010 and 19 May 2011 for photos of adult males and some discussion of their biology.

Monday, September 16, 2013

Ruby Meadowhawk

During our search for Spotted Spreadwings on the St. Olaf Campus on Thursday, Scott King identified a second new dragonfly for me—this Ruby Meadowhawk. Of the red meadowhawks found in our area, several are difficult, sometimes impossible, to tell apart. The keys to identification here include the relatively dark mouth parts (unlike the white of the White-faced Meadowhawk or the red of the Cherry-faced Meadowhawk) and the relatively extensive amber color of the wings. Band-winged Meadowhawks’ bands are shorter and more distinct. This wing color occurs only in Iowa and Minnesota populations of Ruby Meadowhawks, and even here, is not always present. When present, the color makes identification somewhat easier. The bluish pruinescence on the underside of the abdomen indicates that this meadowhawk is a female.

Sunday, September 15, 2013

Cherry-faced Meadowhawk

Scott King writes that this meadowhawk is “one of the troublesome three.” Cherry-faced, Ruby, and White-faced meadowhawks can be difficult, if not impossible, to identify in the field—especially the females. Scott continues that these three give “meadowhawks a bad name, at least by those who demand to identify every last thing down to species.” Mature males, however, like this one, are another matter, and can usually be identified. Note this Cherry-faced Meadowhawk's dark red face and reddish wing veins.

Cherry-faced Meadowlarks are common, early emerging dragonflies (from mid-June through September). Mead reports that these dragonflies will occasionally lay their eggs on dry, mowed lawns, apparently in hope that such habitat will be later filled with water (Mead). Erika and I found several of these meadowhawks in the prairie at the River Bend Nature Center near Faribault on 13 September 2013.

Saturday, September 14, 2013

Spotted Spreadwing

Scott King pointed out to me Spotted Spreadwings at St. Olaf College. These lovely, dark, blue-eyed damselflies are perhaps the latest fliers of the year (at least among the spreadwings). They reach their peak abundance in September and sometimes last into October (DuBois).
Identification is cinched by noticing the two dark spots on the underside of the thorax (the main body of the spreadwing). The spots are evident in the bottom photograph. This species is found across northern North America, and further south on the West Coast and the Appalachian Mountains. Despite this spreadwing’s often being found in high densities, this observation was my first for the species.

Friday, September 13, 2013

Green-tailed Towhee

I have not blogged about Green-tailed Towhees. Along with a plethora of other Minnesota birders, in January 2007 I photographed this individual at Mountain Lake (Cottonwood County). Mine is not a very good photo of this bird, normally breeding in the western United States and wintering in Mexico. Colorado and Wyoming is about as close as you would expect to find this bird to Minnesota.

Other observers took much better photos, even, eventually, deciphering the band number. Turns out this bird was banded near Thunder Bay, Ontario on 10 June 2006 (see Ontario Field Ornithologists). Although Green-tailed Towhees do occasionally stray eastward, the species’ occurrence in Ontario is perhaps even more unlikely than its being found in Minnesota. The photo below is of a bird banded by me years ago within the bird’s normal range in southwestern Arizona.

Thursday, September 12, 2013

Western vs. Eastern Bluebird

Western Bluebirds are found across the western United States and central Mexico. Notice the blue throat and bluish belly on the male in the top photo. Contrast that with the brown throat and white belly of the Eastern Bluebird (below). Western Bluebirds often show brown on their backs or scapulars. I took this Western Bluebird’s photo in a park just outside of Missoula, Montana (and the Eastern Bluebird below is from a Christmas Bird Count at Frontenac State Park just south of Red Wing, Minnesota.)

Somebody, probably from the University of Montana, must be studying Western Bluebirds—look at the color bands on this bird’s legs. Research shows that Western Bluebirds are “socially” monogamous, but both sexes also mate outside their pair bond.  The result is that “offspring are not always related to the attendant male.” The pair also get help raising their young, often by adult male relatives or juveniles from previous broods (Guinan et al. 2008).

Unlike Eastern Bluebirds, Westerns prefer edge habitats, and do not favor large, open meadows. Clear-cutting, snag removal, and fire suppression all adversely affect Western Bluebirds.

Wednesday, September 11, 2013

Yellow-bellied Flycatcher

The 2013 banding season continues to be slow and late in Northfield. Yesterday, 9 September, I caught my first Yellow-bellied Flycatcher. These flycatchers have a short breeding season. In Minnesota, the first fall migrants can be seen in July. This year is not the first that I missed the early migrants—I banded my first fall Yellow-bellied Flycatcher in 2011 on 7 September. I find capturing the true colors of this bird to be most difficult. This photo comes closer than most, but is a tad brownish. The birds actually show a muted tropical greenish on their upperparts.

Tuesday, September 10, 2013

Golden-winged Warbler

On Sunday I banded this Golden-winged Warbler. This warbler is so beautiful that I can not resist sharing this image with you, despite having done so a few times in the past. Indeed, I took a very similar photograph last spring. Previously I have discussed the possibility that there is good reason that this warbler looks somewhat like a Black-capped Chickadee. I have also described the genetics of this species’ hybridization with Blue-winged Warblers.

Golden-winged Warblers have been declining for the last 40 years at a rate of 2.8% per year. The species no longer breeds in part or all of Georgia, South Carolina, Virginia, Massachusetts, Connecticut, Rhode Island, Vermont, New Hampshire, Indiana, Illinois, and Ohio; the species is listed as threatened in Canada and a “species of management concern” in the United States (Confer et al. 2001). On the bright side, Golden-winged Warblers are increasing and spreading northwest across Canada.

What’s happening? The secondary habitat in which they breed is disappearing in the East, where old fields are once again becoming forests and where people destroy wetlands. Loss of habitat in their wintering grounds may also work against the species. Golden-winged and Blue-winged warblers also hybridize. The hybrids apparently have reduced fitness, and they drop out of the populations within 50 years of initial contact; they are replaced by Blue-winged Warblers. Furthermore, Golden-winged Warblers may be particularly prone to parasitism by Brown-headed Cowbirds. Remedies suggested to combat this decline include burning nesting areas to keep fields in a state of early succession, planting aspen in the northern parts of the range, control of cowbirds, and even killing Blue-winged Warblers in areas of overlap (Handbook of Birds of the World Alive).

Sunday, September 8, 2013

American Golden-Plover

On Saturday noon I drove 40 miles south to Steele County, where state birding listservs reported a huge flock of American Golden-Plovers. After several miles’ searching, I found the promised field filled with a flock of about 800 birds. In this first photo, some plovers are loitering in front of the first pond, but about 100 more are feeding behind the water.
The next photo gives you an impression of the huge number of birds as the flock was spooked by a Northern Harrier and an over-flight by a Peregrine Falcon. I was not able to get all the flying birds into my photo frame.
A few birds flew closer to me. In the final photo, note that the under-wings are white, not black. These white axillars are one of the field marks of golden-plovers. These birds are browner above than the much grayer-backed Black-bellied Plover. Few retrain the black bellies of breeding golden-plovers, although a few are black speckled. Note the bird on the far left in the bottom photo.
Such a large flock like this one is uncommon in Minnesota in the fall. American Golden-Plovers have an elliptical migratory pattern. They usually fly off the Atlantic Coast, often nonstop from James Bay to South America (some go all the way to Tierra del Fuego). In the spring, they return through the central United States.

Some birds, especially juveniles and a few adults do make their fall migration through the Great Plains, while fewer still work their way down the Pacific Coast. The fall migration is lengthy—juveniles depart their arctic breeding grounds (along with unsuccessful breeders) much earlier than do breeding adults. In fact, the first birds arrive in South America long before the last birds leave the tundra (Johnson and Connors 2010).

Saturday, September 7, 2013

Tennessee Warbler

This portrait is of this season’s first Tennessee Warbler, an abundant migrant in our area. I have posted on the species many times before—search for these posts by entering “Tennessee Warbler” in the “Search this Blog” box on the right hand column of this blog.

I happened upon an Internet site that may be of interest to photographers and birders—Birding Across America. Although somewhat redundant to the Minnesota Ornithologists’ Union’s home page and to the rare species photographs on eBird (and to eBird, itself), this site, nevertheless, gives photographers another opportunity to post their work. Presumably the site also alerts birders to locations for searching for birds as well as species being seen across the country.

Friday, September 6, 2013

Northern Gannet

I thought I blogged about the Northern Gannets that Erika and I saw during our January 2004 Florida trip. Perhaps because I was on a rocking ferry from Cape Hatteras to the mainland of Virginia and the resultant somewhat blurry photos, I didn’t get around to the post.

Gannets are, nevertheless, wonderful birds. They only breed in 32 colonies on cliffs in northern Europe to Quebec and Newfoundland. Only six of these colonies are in North America. Our gannets winter off the Atlantic and Gulf coasts.

They make spectacular dives for the fish and squid. They plunge from heights of up to 40 meters, achieving speeds over 100 km/hr, before hitting the water, penetrating up to 5 meters, and sometimes swimming 15 meters further down. Often gannets feed in flocks of hundreds. When I taught ornithology, I always wished to share this sight with my students, but I never found anything on the Internet. Lately I located this video of a single gannet diving.

Gannets suffer “fishing accidents,” being tangled in nets, and persecution by fishermen. Despite their limited breeding locations and high adult mortality rates, Northern Gannet populations are increasing at a rate of about three percent each year (Mobray 2002).

Thursday, September 5, 2013

Differential Grasshopper

Assuming the salient field marks of this arthropod are the herringbone chevrons running up its hind legs, this must be a Differential Grasshopper. The species is common in southern Minnesota and most of the United States (except the East Coast and the Northwest.

Dave Bartkey and his family pointed this one out to me at the River Bend Nature Center near Faribault, Minnesota. As you can see, this critter was depositing egg pods containing dozens of eggs between the bricks at an outdoor viewing area. Each pod contains up to 200 eggs, which hatch in the late spring. The young nymphs become adults in a month or two. Usually one generation is hatched each year. The species is not migratory and overwinter in the egg stage in Minnesota.

These grasshoppers can be a significant crop pest. They eat most plants, but prefer grasses, ragweed, sunflowers and Prickly Lettuce. The young feed on grains, alfalfa and hay; adults consume corn, cotton, and fruit crops. Often large swarms attack fields (Wikipedia).

Wednesday, September 4, 2013

Midland Clubtail

Earlier this season, I took this photo of a Midland Clubtail devouring a hapless butterfly. This species is a strong flier, able to chase down other flying invertebrates, including other dragonflies. They breed in fast-moving, clean streams in the northeastern United States, north and west to southeastern Canada and Manitoba. This individual hunted in the Carleton College Arboretum. See also my post of 16 June 2013.

Tuesday, September 3, 2013

American Rubyspot

On Saturday, I found four American Rubyspot damselflies along the creek that feeds into Carleton College’s Lyman Lakes. Identity should be no problem here, although these damselflies, even the male above, were not as gorgeous as the first rubyspots I saw in 2011. Photographing a flying rubyspot proved to be difficult. The damselfly suddenly darted over the stream, but usually returning to its original perch. Notice that this male’s abdomen is wounded, perhaps from an encounter with a hungry bird. Purple Martins, other swallows, and flycatchers all find dragonflies to be tasty morsels.
I was so intent on catching the rubyspot in air, that I never saw the Eastern Forktail fly by in the upper right-hand corner of the center photo. Only when I got home behind my computer did I see the forktail. The male rubyspot’s red wing spots grow larger over time, and are largest on dominant males. Paulson suggests that these spots actually decrease the most dominant male’s hunting success.
The last picture is of a female American Rubyspot. These damselflies do not have courtship displays.  Dominant males simply seize approaching females (Paulson). Males may briefly guard their mates, but only copulate once with any individual female, who may mate with a second male.

Monday, September 2, 2013

Marsh Wren

Reviewing my blog, I am surprised to find no entries for Marsh Wrens. The species an abundant breeder in many cattail marshes across northern North America. They winter further south and into most of Mexico. They are usually easily brought forth by an observer who makes spishing or squeaking sounds.

The Marsh Wren’s song is described by Petersonas “reedy and gurgling, running into a guttural rattle.” Thayer Birding Softwarekindly allowed me to link you to this sound file. Erika and I have always compared this song to popcorn popping in the marsh. After extensive study, ornithologists discovered that Marsh Wrens learn up to 200 song types. They sing almost nonstop, day and night.

Why so many songs? Marsh Wrens are polygynous. In any given population of wrens, about half the males mate with two or more females. The males also build dummy nests—sometimes up to six besides the one actually used by one of their mates. They may be advertising their fitness by displaying their variety of songs and showing off their real estate. 

Birders noticed that eastern and western Marsh Wrens differ. Western birds sing up to four times the number of songs than do eastern ones. The songs of the western birds are less liquid than eastern birds, the western ones being harsher, more complex and variable. Western males are more likely to be polygynous than eastern wrens. Kroodsma and Verner (1997) predict that these two populations will be split by ornithologists into two species, the Eastern Marsh-Wren and the Western Marsh-Wren. The first photo in this blog is an eastern Marsh Wren banded in Aberdeen, South Dakota. The last photo is a western bird, taken in Olympia, Washington.

Sunday, September 1, 2013

Tule Bluet maintenance

With some help from Scott King, I believe these damselflies are Tule Bluets. The male below shows the typical field marks for the species—a small, black spot on top of the first abdominal segment coupled with most of the remaining segments showing more black than blue. Female Tule Bluets show fewer field marks, and may not be identifiable in the field. The female bluet in the upper photos, however, looks close enough to a Tule pattern to be that species—plus this damselfly was in the vicinity of the male below.

The female bluet showed intriguing behavior. As she perched on a dead branch, she wagged her abdomen up and down.  Then she lowered it, as seen in these first two photos. Apparently she used her hind legs to rub off a bit of irritating spider web.  Look carefully for the web strand connecting the tip of the damsels abdomen to the side of the twig. These photos were taken in August at Circle Lake in Rice County, Minnesota.