Friday, September 30, 2016

Bighorn Sheep

Just as last year, this September we found Bighorn Sheep in South Dakota’s Badlands National Park. These regal mammals are introduced to the park. Native Bighorns were extinct in the state by the early 1900s. All now are the result of repeated introductions.

These two sheep were part of a band of about a half-dozen individuals. The bands often combine to form herds. Band size depends on environmental conditions. Sexes may form separate groups and females may form nursery bands.  The sexes usually intermingle during winter. During breeding season, only one female breeds in a given band (Higgins et al. 2000).

Thursday, September 29, 2016

Canada Darner

I catch a few dragonflies in my bird nets. On 9 September 2016, I was at a loss to identify this darner. The ode seemed very dark. I know that dragonflies often lose their bright colors when they are cold or dead. But the weather was balmy and the darner was alive.

I called Scott King for help. To my surprise, he called it a Canada Darner, a species I have been seeking.  I thought they sported brilliant blue spots. That turns out to be in males. Females’ spots and stripes are either dingy blue or, as in this case, dull greenish. Both sexes of Canada Darners are especially liable to become dull-colored in low temperatures and brighten when the dragonflies are active as the day warms (Paulson).

My text books left me confused. I asked Scott what the clincher is for Canada Darner identification. He replied, “the darner ID is based on the length of segment 9, the segment with the ovipositor. For Aeshna canadensis [Canada Darner] it's short....just slightly longer than segment 10; for A. constricta [Lance-tipped Darner] it's long, at least twice the length of segment 10.” I am not sure how a fellow figures that out in the field. A net, I guess.

Tuesday, September 27, 2016

Mountain Bluebird

14 September 2016 found us driving west to Olympia, Washington. As we often do on such trips, we took the scenic drive through South Dakota’s Badlands National Park. We saw relatively few birds, but were delighted to find this Mountain Bluebird near the park headquarters.

These birds increase when people clear forests and put out nesting boxes. On the other hand, populations decline when people convert habitat for single uses, like monocultures or urban development. Most of what we know about their breeding biology is from studying birds using boxes. Much less is known about birds using natural cavities (Power and Lombardo 1996).

Monday, September 26, 2016

Swamp Sparrow

Erika and I found a Swamp Sparrow at the Whitetail Woods Regional Park, Dakota County, on 19 June 2016. Swamp Sparrows are common in eastern North America and boreal Canada. They breed in swamps and wetlands, where they tend to be elusive. We found this bird singing from an exposed perch (“song posts”), a critical element of their breeding habitat. Males also make short, territorial flights above emergent vegetation. Otherwise both sexes forage in dense marsh vegetation.

Sunday, September 25, 2016

Sedge Wren

I have written about Sedge Wrens on numerous occasions. Here is a post from a couple of years ago. The wren in these photos flew up in front of us on 13 June 2016 at Lake Byllesby Regional Park in Dakota Co. It behaved slightly differently than others I have seen. The others were aggressive, keeping their heads down and tails cocked up. The one seemed more curious about us than angry. It stretched its neck up while it checked us out.

Actually little is known about Sedge Wren biology (Herkert et al. 2001). Where and when the wrens breed tend to be unpredictable and they are hard to see in their grassy habitat. See another previous post for a discussion of Sedge Wren distribution.

Friday, September 23, 2016

Rainbow Bluet

On 24 June 2016, I walked around Carleton College’s Lyman Lakes. By accident, I discovered a pair of Rainbow Bluets, one of the more striking damselflies. I noticed them on the side of a Yellow Water-Lily. I took the photo think it would be a pretty photo of ordinary, unidentifiable bluets. I checked the photo focus out on my camera screen, I immediately knew these were a male and female Rainbow Bluet in tandem. The male clasps the back of the female’s neck to guard her from competing males.
In the first photo I noticed another species of bluet behind the lily stem. This damselfly turns out to be a Stream Bluet. Too bad its head is hidden. Male Stream Bluets have one of the terminal abdomen segments entirely blue, They have only thin, blue bands across the abdomen, which is mostly black.  Unlike similar bluets, the thorax is blue with black stripes (DuBois). Stream Bluets are one of the most common damselflies across their range.

Thursday, September 22, 2016

Coral Hairstreak

This spring, I found a Coral Hairstreak in the Koester Prairie (Prairie Creek Wildlife Management Area). This grassland is fairly pristine. Males perch and wait for females. Their eggs overwinter. Adults feed on a variety of flowers. Caterpillars consume Wild Cherry, plum, chokecherry and Butterfly Weed. The species is found across much of North America.

Tuesday, September 20, 2016

Black Saddlebags


Black Saddlebags are most often seen flying high overhead. This summer I have found two perched. The first was at Carleton College’s Lyman Lakes. The second was along the Cannon Valley Trail. The latter forayed out and repeatedly returned to a solitary, high twig. I was ready on one of its returns. Note that it has its legs down, but has not quite landed. Paulson writes that Black Saddlebags are highly migratory. They appear in the north in summer, and their young return south in the fall.

Monday, September 19, 2016

Ring-necked Pheasant

I took this Ring-necked Pheasant photo on 29 April 2016. I was in Rice County, near a game-bird farm. This species often escapes captivity. To survive, pheasants need dense winter cover and diverse farming practices. Agriculture with large monocultures and clean farming practices do not tend to support pheasants. Early mowing takes out many pheasant nests (Giudice and Ratti 2001).

Sunday, September 18, 2016

Cobra Clubtail


Cobra Clubtails are identified by their broad, black-topped tail tips. The second to last yellow spots at the end of their abdomens is smaller than the last one. Finally, the dorsal side of their addoments have small, yellow spots, making the tails look relatively dark. 

Each of the five years that I have been paying attention to dragonflies has been different. Until this year, I rarely found Cobra Clubtails. This year they seemed to be everywhere, even in Erika’s garden. This abundance seems a bit odd to me. My reference guides all report that Cobra Clubtails are usually seen near rapid streams. Such habitat is in short supply here in Rice County.

Saturday, September 17, 2016

Book Sale

All formats of my dragonfly book are on sale through 21 September 2016. Use code VIP20. eBooks are already inexpensive at $9.99 before the sale. The more expensive traditional formats also qualify for the sale. Check it out at http://www.blurb.com/b/6845664-dancing-dragonflies-and-damselflies

Friday, September 16, 2016

Bobolink

Bobolinks are blackbirds.  They breed across the northern United States and southern Canada and winter in Bolivia, Paraguay and Argentina. They make an annual round-trip of about over 12420 miles. Renfrew et al. (2015) report a ten-year old, banded male that “presumably made this trip annually, a total distance equal to traveling 5 times around the earth at the equator!”

Bobolink numbers have decreased during the last 50 years. Factors contributing to this decline include hayland mowing, grazing, shooting and trapping (especially in their wintering and migratory ranges), and pesticides. Bobolinks are, nevertheless, relatively easy to find in Minnesota in the summer. These birds were in the Prairie Creek Wildlife Management Area—Koester Prairie Unit on 14 May 2016. I have blogged about Bobolinks in several previous posts, including in December 2011.

Thursday, September 15, 2016

Common Yellowthroat


Common Yellowthroats love marshes and weedy fields. Adult males are easy to identify. Females and young males are much more difficult. Usually these drab birds show some brown on the crown and yellowish-green tails.

I believe the first photo is of a female bird. It strongly responded when Erika and I made spishing sounds in the Carleton College arboretum on 2 August. The bird appeared to be defending a breeding territory.

I discovered the yellowthroats in the second photo on 16 August at the Dennison Sewage Treatment facility. These two birds are much brighter yellow and appear to show small black flecks on their faces. These field marks add up to immature males.

Common Yellowthroats are common across most of North America, south into Mexico. They were one of the first American species described by European ornithologists. Because of their wide, but somewhat fragmented range, many races of yellowthroats have been recognized. As their genetics are studied, some may prove to be distinct species.

Wednesday, September 14, 2016

Review: The Second Nebraska Breeding Bird Atlas

The Second Nebraska Breeding Bird Atlas. Wayne J. Mollhoff. Bulletin of the University of Nebraska State Museum. Volume 29. 2016. $30.00 softbound.

This book gives the results of Nebraska’s second breeding bird survey. The first census was conducted in 1989. This book, a 30-year update, is essential reading for anyone remotely interested in Nebraska’s breeding birds. The book consists of accounts, one page for each species, for each of the state’s 225 breeding bird species.

A 29-page introduction describes the methods used for the two atlas projects. Nebraska’s ecology and climate are also covered. A short discussion of changes of breeding bird distribution concludes this introduction. Finally, there is a page or two on how to interpret the species accounts.

Each account consists of a short description of the status of each species. These paragraphs include habitat and distributional notes. Comments are included on population trends, along with data from Breeding Bird Surveys. Two charts follow, one describing habitat use and the other, patch size.

Aside from the perennial problem of the variability of identification abilities by observers, two weaknesses stand out. First, patch size is the estimated size of the habitat in which birds were found breeding. Mollhoff admits that patch size is an odd concept. Reporters differ in their ability to estimate patch sizes. Often observers did not report patch sizes. The other “weakness” is that many more observers participated in the second survey. The result is that one does not know if population increases are the result of actual increases or an artifact of having more observers. To his credit, Mollhoff points out this problem where it occurs.

Each account concludes with two distribution maps, one for the first Atlas, the other for the current survey. These maps are invariably fascinating. They allow the reader quick access to distributions and to geographical trends. The blocks with breeding birds are indicated by a red dot. The result is a flat representation of occurrence, but not a display of relative abundance.

The book ends with 10 appendices. These statistically compare the two atlas surveys and present county-by-county analyses. Atlas blocks are described, species at risk are listed, and potential additional species are discussed. Finally Mollhoff presents acknowledgments, references, and a checklist of Nebraska’s breeding birds.

Tuesday, September 13, 2016

Turkey Vulture

On 24 August 2016, John Holden and I drove by two large, black birds. I declared them to be young Turkey Vultures. These vultures begin life covered by fuzzy, white down. A bit of this fuzz remains around the back of this bird’s head and ear. For several months, young have black heads. In the fall, the head begins to turn pinkish. Adult coloration is attained late in their second year.

Turkey Vultures accumulate pesticides in their tissues They are shot or trapped, either accidentally or on purpose. They may succumb to lead poisoning eating animals that have been shot. Like this bird, vultures often scavenge for roadkill along highways. This behavior makes them liable to collisions with automobiles or to electrocution from power lines. Turkey Vultures are the number one cause of damage and fatalities in military aircraft bird strikes. Despite all these perils, these vultures are tolerant of humans and adaptable in diet and nesting sites. Populations are thought to be stable or increasing (Kirk and Mossman 1998).

Monday, September 12, 2016

White-breasted Nuthatch

August White-breasted Nuthatches: I photographed the female, above, on the 25th, the male, below, on the next day. You can tell the females from the males by the females' gray crown, which is black on the male.

White-breasted Nuthatches are common across most of North America, and south through western Mexico. Most beginning birders recognize nutchatches. The birds often forage upside-down on tree trunks. All year, and especially in the winter, they visit feeders. They collect seeds, nuts, and suet, caching food, one item at a time, across their territories. 

These nuthatches are usually permanent residents. In some years, however, some individuals of northern and western populations,move out of their breeding range. Ornithologists do not know what causes these birds to wander or if they ever return to their areas of hatching (Grubb and Pravosudov 2008). This uncertainty makes banding White-breasted Nuthatches all the more worthwhile.

Sunday, September 11, 2016

Ruby-throated Hummingbird

I took these photos of a female and male Ruby-throated Hummingbird on 26 August 2016. We watched as a single bee drove the hummers from the feeder. The hummingbirds flew off and hovered about three meters from the feeder. They then returned to the feeder, only to be driven off again. Finally the bee relented and allowed the birds brief visits to the sugar-water.

Prior to their migration, these hummers can double their body mass, consuming nectar and insects. Despite an average body mass of 3.5 grams for females, and 3 grams for males, many Ruby-throated Hummingbirds cross, non-stop, the Gulf of Mexico. The proportion of Ruby-throats that make a trans-gulf flight is unknown, as are many other details of their migration (Weidensaul et al. 2013).

Friday, September 9, 2016

Green-striped Darner

Yesterday Erika stopped short as we fled the mosquitos in the Carleton College arboretum. An exquisite darner flew slowly along the edge of the path before perching horizontally on a dead weed. Scott King and the Minnesota Dragonfly Society Facebook page all concluded this dragonfly is a Green-striped Darner. This species is found in northeastern North America, west to Minnesota and Iowa.

Field marks include the 90-degree notch on the front thoracic stripe. This stripe also has a broad extension of its top, back aspect. Part of the frustration with being a beginning dragonflier is figuring out terminology. Mead writes that this species spends most of its time in flight, even past dusk. Paulson reports that dense grasslands, the those found in the prairie, are among their favored habitats. When they do perch, they often land on tree trunks.

Thursday, September 8, 2016

Common Nighthawk

Yesterday, 7 September 2016, Erika and I returned to Northfield after a relatively unproductive local birding jaunt. As we entered the eastern edge of town, at the Roosevelt Parkway Wetlands, we noticed 50 long, sharp-winged birds swarming through the sky. “Aren’t those nighthawks?” asked Erika.
She was correct. These were our first Common Nighthawks of the year. I had about given up seeing them this year. Across much of their North American range, Common Nighthawks have become uncommon. The causes of these birds’ decline are unclear, but may included increased predation, pesticides (especially non-selective mosquito control), and/or habitat loss. In the later case, nighthawks prefer nesting on flat, gravel roofs, a design no longer favored by architects. Non-gravel roofs may not provide eggs sufficient camouflage, may get too hot for egg survival, and smooth roofs can result in eggs rolling away. Nighthawks are also often victims of roadkills and aircraft strikes (Brigham et al. 2011).

Tuesday, September 6, 2016

Steller’s Jay


As I populate my eBird checklists with photographs, another species surfaced that escaped note in this blog. We photographed this Steller’s Jay in Lacey, Washington, on 17 June 2008. This jay is common in conifer forests, from Alaska to Central America. They invade campgrounds and cities, and are common at bird feeders.

With such a large range, often isolated by mountain ranges, there is no surprise that the Steller’s Jay exhibits considerable geographic variation. Seventeen races are recognized by Walker et al. (2014). These subspecies fall into two groups, northern ones with long, black crests and southern birds, with short, blue ones. Races also differ in the amount of white on the head and in general body size. Southern birds tend to be smallest. Where these races come into contact, populations are intermediate and presumably interbreed.

Sunday, September 4, 2016

Burning Prairie

Much of Carleton College’s lower arboretum is converted to prairie. This process involves periodic burning. Native prairie plants tend to be fire resistant, while invasives do not survive. In the early Spring, the blackened earth warms the ground, promoting early growth. Carleton burns the prairies on more or less of a four-year rotation (Braker, pers. com). Carleton is doing a good job—the prairie appears to be healthy and a number of prairie birds have returned to the area. There can be too much of a good thing. Pyle (2010) warns of “overzealous” prairie burning. He writes that burning Leadplant is lethal to three species of butterfly and at least one moth. If prairies are burned too often or too extensively, the native Lepidoptera do not survive.

On 22 April  2016, Erika and I came upon a fire crew maintaining the prairie. A Red-tailed Hawk oversaw the project. The raptor flew back and forth over the burned grassland. Presumably the hawk searched for small mammals displaced by the flames.

Saturday, September 3, 2016

Yellow Warbler

Chances are that this male Yellow Warbler wintered somewhere between coastal, Mexico and the jungles of Bolivia, Peru, or Brazil. Only scattered winter records exist for the United States. I found this spring migrant near Northfield on 10 May 2016.

In Aberdeen, South Dakota, I often banded Yellow Warblers. I never had one recovered during the winter, but twice I retrapped birds I banded the previous year. I find it remarkable that a small bird like this can find its way back to the same backyard where it nested.

Yellow Warblers prefer to breed in willow patches in wetlands. This sort of habitat is where I took this photograph. Destruction of willow patches, for farming, grazing, or landscape development, can have a negative effect on Yellow Warbler populations. The species is also vulnerable to parasitism by cowbirds. Some populations have declined by 50% since the 1980s (Lowther et al. 1999).

Friday, September 2, 2016

Blue Dasher Day

On 22 July 2016, Erika and I returned to the Lebanon Hills Regional Park. This year we first visited and were inundated with dragonflies. During the more recent visit, we found far fewer Odonata—except that we encountered dozens of Blue Dashers. Many were females. I am less familiar with the females than with the males. I took a long time before I identified this first photo as a female Blue Dasher. I have never seen one with such green eyes, or with green dorsal stripes.
Male Blue Dashers were present, like this one in the obelisk position. Dragonflies are said to raise their tails in this fashion to reduce their exposure to the blazing sun on hot days. And the weather was hot during our hike, over 90 degrees (32 Celsius)—and humid.
Perhaps dragonflies also obelisk for camouflage. I am fairly certain this third photo is also of a male. The fact that it looks like an extension of its perch probably hides the dasher from both prey and predators.
These final two Blue Dashers are more typical looking females (compared the the female in the first image. They are probably adults, while the first may be an immature. In any event, both Erika and I were impressed with their colorful eyes.