Thursday, September 29, 2011

Black-throated Green Warbler

On 27 September 2011, I banded this Black-throated Green Warbler. This species stands out for me as one of the most beautiful of North American birds (even if Erika often comments that is what I say about every bird I just saw). I have previously blogged about this warbler on 25 August 2010.


The Black-throated Green Warbler is a very common inhabitant of northeastern coniferous forests, and it ranges south through the Appalachian Mountains into deciduous woodlands. Despite its wide range, little is known about its breeding biology and migration patterns. This warbler inhabits forest interiors, and thus is vulnerable to forest fragmentation, specially in its Central American winter range. Recent hemlock and fir die-offs along the East Coast also threaten this species (Morse and Poole 2005).

Wednesday, September 28, 2011

Swainson's Thrush

I banded two Swainson's Thrushes on 27 September 2011. In September 2010, I blogged about this thrush's nomenclature and systematics and, in April 2010, I wrote about identifying and aging this species. The Swainson's Thrush is "one of the most common birds of northern spruce-fir forests" (Mack and Yong 2000). Across their range, however, populations have been declining. I have banded fewer Swainson's Thrushes each of the past three years (although this trend may not be statistically significant).  In any case, ornithologists do not understand the causes of the continent-wide decline. Hypotheses include habitat destruction in both the breeding and wintering ranges and cowbird predation.

Tuesday, September 27, 2011

Dragonfly Book Review


For me, 2011 has been The Year of the Odonata. Everyone sees dragonflies and damselflies, but only since fall 2010 have I tried my hand at identification. I have been fortunate to have a patient and willing expert to take me by the hand. Recently I discovered Dennis Paulson's Dragonflies and Damselflies of the West, published in 2009. This guide will aide anyone interested in pursuing these fascinating, gorgeous, and often overlooked creatures.

What is it about these insects that has so caught my imagination? Unlike summer birds, dragon- and damselflies come in a parade, some emerging from their ponds early, others late, still others in between. They come in a myriad of patterns and colors. Their reproductive cycles are intriguing. To date, I have photographed over 40 species, and each has been a thrill to discover. Chasing Odonata has been like birdwatching on a new continent.  What a thrill to discover different species, even if they prove to be common! Moreover, much less is known about ondonate distribution than is known in ornithology. One of my first damselflies, a Great Spreadwing, was a new record for Minnesota. Perhaps less possible for us neophytes is the remote possibility of discovering undescribed species!

This book, described as "verging on definitive" by my dragonfly expert, covers all 348 species found in western North America. Minnesota lies just east of this area--the text's eastern limit being the Dakotas. Nevertheless, Minnesota is included in many of the range maps and most of the species I have seen are included in this book. All of North America sports 453 dragon and damselflies--only about a quarter of this number are not covered in western guide. I eagerly await the publication of an Eastern volume, due out this fall (see my recommendations on the right side of this blog to place a prepublication order). Minnesotans will want both volumes. I suspect they may be the only books on Odonata that most of us will need.


This volume's contents are lavishly illustrated with color photographs and include "information on size, distribution, flight season, similar species, habitat, and natural history..." The "introduction provides an essential primer on the biology, natural history, and conservation of [dragonflies]...along with helpful tips on how to observe and photograph them." (The quotes are from an Amazon.com review, viewable from the link at the top of this post.) At under $20, the price is exceptionally reasonable.


All books can be criticized. The photographs are a tad small and lack the handy arrows present in Peterson field guides for birds and in Dragonflies of the North Woods. Paulson's book does not help the reader begin the identification process by keying out the various groups of dragonflies--a key to genera and families would be most useful. (Keys can be found on the Internet, some even written by Paulson.) Finally, dragon- and damselflies are very difficult to identify.  Paulson cautions, "anyone who needs positive identification should strongly consider capturing the individuals in question." Dragonflies are variable and often require structural study. Despite these caveats, I can't wait for next season's Odonata and for future road-trips across the country!

This damselfly is an Ebony Jewelwing taken near Northfield on 21 July 2011. Dragonflies and Damselflies of the West includes this eastern species because this jewelwing ranges into Nebraska and Oklahoma. If you are interested in becoming a odonate enthusiast, click on the button at the top of this review.

Monday, September 26, 2011

Hermit Thrush

The Fall 2011 migration continues to be very slow. The only bird banded on Monday morning was the season's first Hermit Thrush. Last year I wrote on how to tell the age of this species.  Hermit Thrushes are "among the most widely distributed forest-nesting birds in North America." They are found in most of North America's boreal and montane forests. These thrushes winter from Central America north into the southern United States. Despite being common, relatively little is known about their life span, breeding biology, and range of individual birds (Jones and Donovan 1996).

Sunday, September 25, 2011

Variable Darner

Variable Darners are common, ranging from Alaska across Canada, south into much of the United States.  This species can regulate its body temperature, resulting in both its northern range and its ability to feed during the evening and night. This dragonfly preys on insects even when darkness prohibits humans from seeing them (Digital Atlas of Idaho). My bird nets pose a hazard to this darner, as it flies over the forest clearing of our backyard. Earlier this year, I also found a Variable Darner in Carleton College's arboretum prairie. The darner perched vertically from the prairie forbs on the edge of a walking path. Note this species thin thorax stripes; the variability of this field mark is why this species is called the Variable Darner.

Friday, September 23, 2011

Blue Dasher

In July, an outing that Erika and I enjoyed was the Minnesota Water Garden Society's annual water feature tour across the greater Minneapolis/St. Paul area.  My new interest in stalking dragonflies added to the good time.  I photographed these Blue Dashers in Dakota County of 30 July 2011.
Look for Blue Dashers almost anywhere with still water. The larvae are highly tolerant of poor water quality and low oxygen levels (Buggide.net). Indeed, many biologists use the presence of Blue Dashers as an indicator of poor water quality.  This species is found from southern British Columbia east to Ontario, extending south through the U.S. from southern California east to Florida. The top photo is a male, the lower, a female.

Thursday, September 22, 2011

A Rose is a Tree Frog?

Shakespeare wrote, "What's in a name? That which we call a rose, by any other name would smell as sweet." Romeo may have been romancing Juliette; or, perhaps Shakespeare joked about a rival theater, The Rose, which had substandard plumbing (The Phrase Finder). Gertrude Stein wrote, "A rose is a rose is a rose;" Stein may have meant that roses exist independent of language. In this blog post, a rose is a Gray Tree Frog!
Gray Tree Frogs show a great deal of variablity in color. The photo below is of a gray Gray Tree Frog taken in Erika's garden last spring. I previously posted on this critter.

Wednesday, September 21, 2011

Leucistic Gray Catbird

Leucism is characterized by reduced pigmentation in animals.  Unlike albinism, leucism is caused by a reduction in all types of skin pigment, not just melanin (Wikipedia).  Leucistic animals usually have normal-colored eyes; albinos' eyes often are pink. Frequently, like in this catbird, with its white throat and bill tip, leucism is patchy, resulting in regular-colored animals with patches of white. This condition is called partial luecism. I banded and released this Gray Catbird near Northfield on 19 September 2011.

Tuesday, September 20, 2011

Horned Clubtail

This female Horned Clubtail is another of this summer's dragonflies that I encountered in June alongside the small pond at the southern end of Carleton College's lower arboretum. This species ranges across the northern, midwestern North America, usually near ponds, lakes, and marshes.  According to Ecobirder, Horned Clubtails appear early in the summer and are gone by the end of July. Adults will consume just about any small, soft-bodied, flying insect they encounter (Montana Field Guides).

Monday, September 19, 2011

Valley Grove Preservation Project

Erika and I discovered a "new" place in Rice County: the Valley Grove Church and Prairie. The church is just north of Big Woods State Park, on the highest elevation of land (about 1200 feet above sea level) between Minneapolis and Chicago. The Valley Grove Preservation Society acquired the church and began returning the surrounding acreage from farmland to native prairie. The church was built in 1894; it was decommissioned in 1973. The Burr Oak on the right side of the photo above is at least 200 years old. 
Historically Rice County contained a dynamic mosaic of woodland and prairie. When Nicollet passed through the county in 1838, land south and east of the Cannon River was prairie; north and west was woodland (opposite of what you might predict). The Cannon River Valley, once a gigantic glacial drainage, lies in the far distance in the photograph above. Today the restored prairie and adjacent woodlands are definitely worth exploring.
At a monthly meeting of the Northfield Garden Club, Erika and I attended a talk on prairie invasive plants. Invasive plants are non-indigenous species that replace native vegetation (weeds are simply unwanted plants in disturbed or cultivated areas). Reestablishing a prairie means battling invasive plants.  
Two of these invasive plants are photographed here--the yellow Bird's-Foot Trefoil and the white Queen Anne's Lace.  The trefoil is native to Eurasia and North Africa. It is grown as a forage plant, but can replace native species, especially in Australia and North America. Trefoil's cyanogenic glysoides can be poisonous to humans. (The species is common along Northfield streets, so caution with young flower collectors is advised.)


Queen Anne's Lace, native to Europe and Asia,  is also known as Wild Carrot. Garden Carrots are derived from Queen Anne's Lace. It is a pest, taking over pastures and prairies. Apparently eating wild carrot seeds interferes with progesterone synthesis--thus the plant had a folk use for birth control. Crushed seeds prevent egg implantation in laboratory mice. Handling the plant can also cause skin sensitivity to sunlight. All of these amazing plant facts must be correct, because I read them in Wikipedia!

Saturday, September 17, 2011

Black-throated Blue Warbler

On 16 September 2011, I banded a first-year male Black-throated Blue Warbler. Curiously, this date is the same as I banded this relatively uncommon species (in Rice County) last year. While fall females can be confusing, males, as you can see, molt directly into a bright fall plumage. On the females, look for the white square wing patch; but be warned that some females lack even that identifying feature. For more information and a photograph of the female, see my post of 17 September 2010.

Friday, September 16, 2011

Variegated Meadowhawk

On 13 September 2011, Erika and I found this Variegated Meadowhawk in the Carleton College Arboretum prairie. The harlequin tail amazed me! Over the following two days a high pressure cell brought us cool air, below freezing with snow showers in northern Minnesota, in the upper 30s F here. This dragonfly probably migrated ahead of the weather. Many western individuals fly east in the fall towards the Atlantic coast and Florida (Mead 2003); others head south towards Honduras and even eastern Asia (Idaho Digital Atlas). Many breed in their wintering areas. Young emerge in the spring and, often within 24 hours, begin flying north. In their summer range, they again go through their life cycle. Thus most fall migrants tend to be immature individuals, as is the one in my photo, while many spring migrants are adults. Apparently these dragonflies use the sun's position to navigate (Talk About Wildlife). In his website, Jeff Pippen writes "this species should be called 'variable meadowhawk' as it seems to be variable in size, color pattern and exact range!" Variegated Meadowhawks are often seen migrating with Common Green Darners, which we also noted nearby (see lower photo). 

Wednesday, September 14, 2011

Plains Clubtail

Erika and I flushed several Plains Clubtails from the Carleton Arboretum prairie paths in early August (the same day we found the Cobra Clubtail). Look for this species in July and August along sandy or muddy streams that have some current. Plains Clubtails are widespread, but can be picky about exactly where they are found.  According to Wikipedia, they "will often occur only in certain stretches of a particular river..." Plains Clubtails, however, are common in Iowa along large streams, and especially the Mississippi (Iowades.com). Wikipedia claims this species does not tolerate cool weather, even rarely flying on cloudy days. 

Tuesday, September 13, 2011

American Redstart

American Redstarts readily approach birders who make spishing or squeaking noises. Both sexes are territorial. Territory for the male serves to make sure he his the father of his mate's young, to assure that his mate enjoys optimum breeding habitat, to defend food resources for the pair, and to defend the area used to attract mates. Territories help the female make sure her mate is not lured away by competing females and to defend their habitat resources. Redstarts also defend winter territories (and return to them year after year). Winter territories defend food resources and may reduce competition between redstarts (Sherry and Holmes 1997). Second year males, which look similar to females, attempt to establish territories during the spring (see blog post of 10 June 2010).  A few breed, but most move away after a few weeks, and attempt to create territories elsewhere.
The upper photo was taken along the Cannon Valley Bike Trail this July; the female, below was caught, banded, and released this fall in Northfield.

Monday, September 12, 2011

Cobra Clubtail

Early in August, Erika and I came upon this Cobra Clubtail in muddy tire tracks in a path in the Carleton Arboretum's prairie. The dragonfly is named for its abdomen end's looking like a cobra's head. All my sources, including Mead (2009), advise looking for this species on the shoreline brush, sand, or rocks along mud-bottomed rivers and lakes. The Fontenelle Nature Association writes that "Males can wander some distance from water." We found this female about a quarter-mile from the Cannon River. I was able to take this one photograph before the clubtail fled. We never saw another. 

Sunday, September 11, 2011

Black-and-white Warbler

The Black-and-white Warbler is breeds commonly in eastern North American and central Canadian forests. This warbler winters from the southern United States south through much of Latin America.  Possibly due to its tolerance of disturbed habitat, it is one of the few neotropical migrants not suffering widespread population declines. (This photo was taken during May's migration.)


Male Black-and-white Warblers, like the one in the photograph above, migrate earlier in the spring than their mates. Once on their breeding territories, the males establish territories.  Females are known to take males to territorial boundaries.  Here aggressive interactions take place between owners of adjacent territories.  Observing these conflicts, the females appear to assess the fitness of the males. Females build their nests, usually on the ground near a tree trunk or fallen log. Females do all the incubation, although are often fed at the nests by their mates. Both sexes cooperate in raising the young (Kricher 1995).

Friday, September 9, 2011

Whooping Cranes

For the second time this year, on 9 September 2011, two Whooping Cranes were discovered in Rice County. Ray Simon first found the birds, which grazed in a wetland on the south side of 90th Street East (Old Dutch Road), a couple of miles west of Decker Avenue. Like the cranes seen this spring, these birds are from the flock that breeds in Wisconsin and winters in Florida (see below). Although the birds are about a quarter-mile from the roadside, observers are cautioned not to trespass into the field or wetland and to use caution against disturbing the cranes.
Eva Szyszkoski of the International Crane Foundation writes: "Based on the bands I could pull off of your photos, these two birds are adult breeding pair numbers 7-07 and 39-07. They are both four years old. They nested this year near the Necedah NWR but abandoned their nest on 4 May. Two eggs were collected (one infertile, one fertile but addled). They have a history of moving into Minnesota in the summer or fall every year (except for last year when they molted and were unable to fly for ~6 weeks). They will most likely begin migration south from Minnesota and will not return to Wisconsin before then. No. 7-07 was raised and released using the ultra-light release method and no. 39-07 was raised and released using the Direct Autumn Release method. They have been together for about three years now."

Giant Swallowtail 3

In Minnesota, 2011 certainly has been the Year of the Giant Swallowtail. As I recently blogged, this handsome butterfly usually does not range north of Iowa. This distribution is understandable, since the larvae require citrus trees. The adults, nevertheless, do occasionally migrate into the upper Midwest.  Jeffrey Hahn, of the Minnesota Extesion Service, writes that Giant Swallowtails can not reproduce in the state because of our lack of citrus trees. The male Giant Swallowtail in the background of this photo was clearly more interested in this female than he was in the garden flowers. Perhaps he was interested in giving reproduction a try. But, because of the larvae's citrus requirements, I doubt that the reproductive cycle will be successful here in Minnesota. These Giant Swallowtails cavorted in our CSA (Community Sustainable Agriculture) farm in southern Dakota County.


Update: A reader writes that the Prickly Ash, a fairly widespread understory shrub/tree in Minnesota is listed as a host plant for Giant Swallowtail larvae. Thus the butterfly might propagate locally. 

Thursday, September 8, 2011

Yellow-bellied Flycatcher

I wrote in a previous blog that this flycatcher's short breeding season makes this migrant a late in the spring and early in the fall. This year has been an exception--I missed it this spring and August passed without my seeing it this fall. I banded this Yellow-bellied Flycartcher on 7 September 2011. An exception among the hard-to-identify Empidonax flycatchers, the Yellow-bellied is told relatively easily by its greenish back and yellowish throat and belly. I mentioned in my previous post the difficulty in photographing the subtleties of these colors.


Despite these features, this species is hard to see. The colors blend into the muskeg forests in which they breed and the Central American rainforests where they winter. Gross and Lowther (2011) claim that this flycatcher is "one of the continent's most overlooked birds." The authors warn, futhermore, that its "soft voice is easily confused with that of other species." 

Wednesday, September 7, 2011

Autumn Meadowhawk

Autumn Meadowhawks have returned to our garden.  They were among my first dragonflies last year, beginning this odonata kick of mine. This species flies in late summer, sometimes even into November.  As the season progresses, males become more red, probably due to age rather than temperature. Thanks to Scott King for sharing a haiku by Kaya Shirao (1738-1791):
The start of autumn
is decided
by the red dragonfly

Tuesday, September 6, 2011

White-lined Sphynx Caterpillar

Earlier this summer Erika and I saw an adult White-lined Sphynx in Erika's garden. Typical for the species, the moth fed just at dusk and fled by the time I found my camera. The adults are sometimes mistaken for hummingbirds and are often named "hummingbird moths." 


On 3 September 2011, while performing our civic duty by weeding the mulch of a local playground, we dug up two White-lined Sphynx caterpillars, often known as hornworms. Unlike the similar Tomato Hornworm, this caterpillar usually does not damage gardens. The caterpillars feed on a wide range of host plants before digging into loose soil to go into chrysalis.  Pupation occurs in a small, packed-earth chamber. Two to three weeks later they emerge as adult hummingbird moths  (Colorado State University Extension Service).  

Monday, September 5, 2011

September Warblers

These photos are of warblers I banded in Northfield, Minnesota, on 3 September 2011. I enjoy sharing these head-on portraits with you. More traditional poses are available on the Internet or elsewhere in this blog. The head-on angle makes the top two birds difficult to identify. In the field, because of the white patches in its upper tail, this first bird is obviously a Magnolia Warbler. (Last September I posted a photo of these patches from a somewhat brighter fall bird.) Closer study reveals a gray head with white eye-rings, a hint of a gray breast band, and two white wing-bars.
The second fall warbler may be even trickier to identify. This exceptionally bright Tennessee Warbler displays a green back and hints at its white belly and undertail coverts.  The beginnings of a yellow eye-line are clearly visible, although you may have to take my word that the yellow lores continue over the bird's eyes. (A post of last September shows some of Tennessee Warbler's variability and better views of those eye-lines.)
Finally an easy fall warbler--no doubt about this male Wilson Warbler's identity. Unlike other warblers, the Wilson's basic feathers are similar to its alternate (spring) plumage. One difference is that a young bird in its first basic (winter) plumage has pale edges to its black cap feathers. Note that about 50% of females also have black crowns, but the black is less extensive than on the males' caps.

Sunday, September 4, 2011

Bay-breasted Warbler

Saturday morning, 3 September 2011, was hot and humid. A cold front went through around mid-day, with clouds and wind.  At 5 PM I banded my first fall warbler flock. Among them were three Bay-breasted Warblers. A Confusing Fall Warbler, few diagnostic field marks are visible on this first photo. The second photo actually gives one key to identification. Note this bird's faint bay-colored flanks. Although absent on a few birds, this color is present on almost all fall Bay-breasted Warblers. With the flank feathers exposed, this color is even more visible in the second photo.
One of the other Bay-breasted Warblers, in the last photo, showed even brighter flanks. All the birds sported black feet. The very similar Blackpoll Warbler shows some yellow on its feet and always lacks the bay-colored flanks. For further discussions on Bay-breasted and Blackpoll warblers, see my posts of 5 September 20105 October 2010 and 26 May 2011.

Saturday, September 3, 2011

Riverine Clubtail

In Minnesota, the Riverine Clubtail is probably widespread but uncommon. This dragonfly is usually encountered perched in vegetation along streams and rivers. The clubtail's weight often bends their leafy perches downward, leaving the clubtail hanging vertically. From these perches, Riverine Clubtails hunt over rivers. Although said not to be as wary as other hanging clubtails (Mead), this individual only allowed this single photograph.  Erika and I discovered this dragonfly in ideal habitat on 9 August 2011 in Goodhue County along the Cannon River. The species is found across much of the eastern United States. 

Friday, September 2, 2011

Eastern Red Damsel

Eastern Red Damsels are fond of springs, such as the small ponds at Lake Byllesby County Park in Dakota County. I took this photo in mid-July. This damselfly can be common if appropriate habitat exists, but is vulnerable to drought and draining.  They are often overlooked, since they are small and tend to fly through dense vegetation. Eastern Red Damsels are found in the eastern United States; Minnesota is near the western edge of their range. 

Thursday, September 1, 2011

Black-shouldered Spinylegs

This dragonfly is found along rivers and streams in the eastern United States and southeastern Canada. On 19 August 2011, Erika and I found Black-shouldered Spinylegs on the bike path at Afton State Park on the bluffs above the St. Croix River. Spinylegs were among hundreds of dragonflies flying above the prairie where we found the Henslow's Sparrow, of which I recently blogged. 


Back-shouldered Spinylegs get their name from large spines, not visible in these photos, on their legs.  The spines are used in prey capture. The species is shiny yellow as young adults, but later becomes dusky, as in the lower photograph.