Saturday, December 31, 2016

Common Whitetail

A Common Whitetail in the Carleton College lower arboretum from 30 May 2016. This dragonfly is “ubiquitous” across the United States and southern Canada (DragonflyID). Males are aggressive and often try to steal females from other males. Their white abdomens are raised in challenge as they fly after their competitors. After mating, females each lay about 1000 eggs.

Across their range, Common Whitetails are found near almost any body of water. They venture from aquatic habitat, and are often seen along walkways, on the grournd, or perhced in shrubbery. They are common in Erika’s garden.

Friday, December 30, 2016

Scarlet Tanager

I banded this Scarlet Tanager in Northfield on 12 September 2016. Notice the molting wing coverts. These tanagers molt into their basic, winter plumage from July through September. They do not, however acquire new regimes or rectrices (wing or tail) feathers. Males molt into their bright scarlet plumage beginning in January while they are in their tropical wintering grounds.

Thursday, December 29, 2016

Olive-sided Flycatcher

Erika and I discovered this Olive-sided Flycatcher in Carleton College’s lower arboretum on 3 June 2016. Typical of the species, this bird foraged from and returned to the dead tops of a tall tree. From these perches, they sally forth in search of flying insects and especially bees (Altman and Sallabanks 2012). Its relatively large bill and vested appearance are among this flycatcher’s field marks.

Tuesday, December 27, 2016

Ebony Jewelwing

Ebony Jewelwings occur across much of the eastern United States and southern Canada. They can be abundant along shady streams and rivers. I took these photos on 6 June 2016 in the Carleton College lower arboretum. The first image is of a male. Females have a white spot on their wings.

These damselflies have a long flight season, from May through October (and all year in southern parts of their range). Individual adults, however, survive only a couple of weeks (Dragonfly ID). Ebony Jewelwings were among the first odonates I discovered during my dragonfly odyssey.

Monday, December 26, 2016

Midland Clubtail

Midland Clubtails are difficult to identify. I photographed this one in the Carleton College lower arboretum on 6 June 2016. Some of the field-marks are not visible in this photo. The underside of the third abdominal segment is white in the Plains Clubtail—it is usually yellow in the Midland, which tends to have narrower colored bands on the sides of its thorax. Midland Clubtails in our part of Minnesota tend to be quite variable. Our population is in a blend zone between a western and eastern subspecies, Gomphus fraternus fraternus and Gomphus fraternus manitobanus. Most our our Midland Clubtails have a yellow triangle on the top of their 8th abdominal segment. The 9th segment is variable, sometimes yellow, other times dusky, and can be black. In any event, this species is a voracious predator that often consumes other dragonflies.

Saturday, December 24, 2016

Eastern Kingbird

On 24 July 2016, Erika and I hiked in the Carleton College Upper Arboretum. We photographed a curiously speckled Eastern Kingbird. Turns out that the speckles are typical of juvenile plumage—this bird was hatched this year.

Eastern Kingbirds are monogamous. If the pair survives their winter sojourn to South America, they usually remate and use the same territory. “Nevertheless,” write Murphy (1996), “extra-pair copulations and intraspecific brood parasitism may be common.”

Pairs only raise one brood of young per year. One reason for single brooding may be that catching enough flying insects to raise a brood is difficult, especially during cool, wet summers. The result is an extended period of parental care.

Thursday, December 22, 2016

Northern Rough-winged Swallow

I photographed this Northern Rough-winged Swallow at the River Bend Nature Center in Faribault in May 2016. This swallow gets its name from the rough outer edge of its outer primary feather. This edge is caused by feather barbs, recurved in males, or pointed in females. The swallow’s scientific name is Stelgidopteryx serripennis, which translates to “scrapper-wing saw-feather” (De Jong 1996), The function of this structure eludes ornithologists.

Tuesday, December 20, 2016

Gray-cheeked vs Swainson’s Thrush

Gray-cheeked Thrush (7 September 2016) and Swainson’s Thrush (1 September 2016), two often difficult to identify species. These birds migrate through Northfield.

Generally Gray-cheeks lack the bright tan-colored eye rings of the Swainson’s Thrush. Some individuals are so similar that they have been thoguht to be hybrids. Genetic or other evidence of hybridization, however, is lacking.

I band more Swainson’s than Gray-cheeked thrushes. In their breeding range, Swainson's forage closer to the ground than Gray-cheeks, which may account for this difference. On small islands that lack Gray-cheeked Thrushes, Swainson’s forage higher in the forest (Mock and Yong 2000). I doubt, however, that these ecological differences are maintained during migration.

Monday, December 19, 2016

Intergrade Flicker

The best bird we saw during Saturday’s Northfield Christmas Bird Count was this odd Northern Flicker. I think it is an intergrade between the western Red-shafted and eastern Yellow-shafted races of the species. The two races interbreed where their ranges overlap in the upper Great Plains.

It is quite different from the intergrade flicker we saw in Wyoming last summer. The Wyoming bird looked much like a yellow-shafted bird. Saturday’s bird looks like a female Red-shafted Flicker. It has gray sides to the face and reddish wing and tail feathers. But the red nape feathers are red, a yellow-shafted field mark, which should be lacking in a red-shafted female.

Recent research indicates that Yellow-shafted Flicker feathers sometimes turn orange after the birds eat non-native honeysuckle berries. The gray sides to this bird’s face, however, argue against this bird’s being an orange-shafted Yellow-shafted Flicker.

Sunday, December 18, 2016

Eastern Screech-Owl

Saturday’s Christmas Bird Count was run despite dire predictions from the weather service. We got about six inches of fluffy snow on Friday night, but the winds were not fierce and the temperatures stayed above zero. We saw a couple of interesting birds. One, the Eastern Screech-Owl was found by others outside our count area. After lunch, we drove over to take a look.

Friday, December 16, 2016

Gray Catbird

This Gray Catbird is an exception to the rule that this species inhabits dense, shrubby vegetation. I found this bird foraging for insects from a Frisbee course basket. I was searching for dragonflies along Carleton College’s Lyman Lakes last June. Catbirds sometimes earn farmers’ ire by consuming fruit. This individual ate small caterpillars, perhaps redeeming its berry-eating reputation.

Gray Catbirds are one of the few birds that regularly eject cowbird eggs from their nests. This ability is learned. Catbirds only destroy cowbird eggs after they learn what their own eggs look like. If cowbirds lay their eggs in the nest before the catbirds, then the catbirds destroy their own eggs! Ornithologists do not know if, in subsequent years, older catbirds have to relearn the appearance their eggs (Smith et al. 2011).

Wednesday, December 14, 2016

Great Crested Flycatcher

Great Crested Flycatchers are another species that is probaby more common now than before the great forests of eastern North America were destroyed. Forest fragmentation caused increases in woodlots and woodland edges favored by this flycatcher. I took this photograph last summer in Erika’s garden.

This species is the only flycatcher that nests in cavities, either natural, excavated by woodpeckers, or human built. Great Crested Flycatchers are famous for often using shed snakeskin in their nest, presumably to discourage potential predators. Other items that look like snakeskin, like plastic wrappers, are occasionally used instead (Miller and Lanyon 2014).

Sunday, December 11, 2016

Common Baskettail

Flying dragonflies are always a challenge to photograph. I captured this Common Baskettail on 11 June 2016 over the Lyman Lakes of Carleton College. This baskettail was making patrolling flights back and forth along the edge of the lake.

Common Baskettails are often abundant across most of eastern North America. The are found over almost any body of quiet water. Although not present on all individuals, the dark spotted hindwings are good field marks for identifying this species.

Saturday, December 10, 2016

Blue and Green-winged Teal

On 24 August 2016, I found a large flock of Blue-winged Teal at the Dennison, Minnesota, sewage treatment ponds. The ducks circled the facility as I took photos. To my surprise, when I got home and worked on the images, I discovered that one of the ducks was not a Blue-winged Teal. The lowest bird in the center of the photo is actually a Green-winged Teal.

Thursday, December 8, 2016

Eastern Pondhawk

Eastern Pondhawks from 2016. The first two photos, both taken on 1 June, are from Carleton College’s Lower Arboretum here in Rice County, Minnesota. The first one is male, the second, female.
The third photo is of an immature male taken at the Savannah National Wildlife Refuge in Jasper County, South Carolina on 24 March. The last image is from St Marks National Wildlife Refuge, Wakulla County, Florida on 23 March.
Considering their wide range, almost all of the eastern United States east of the Rockies, I am surprised that local, isolated populations have not evolved into distinct species. On the other hand, Eastern Pondhawks are abundant and not very particular in their habitat selection. Almost any slow moving or still water will suffice.

Tuesday, December 6, 2016

Snow Goose

Yesterday, 5 December, Erika and I found two Snow Geese at the Jefferson Parkway Wetlands in eastern Northfield. These birds were first reported by Gerry Hoekstra on 29 November, but had not been seen since. Gerry returned later in the day and found a third, young Snow Goose.

White and “blue” Snow Geese are color morphs of a single species. Only in 1983 did ornithologists figure out this situation. One gene controls this color difference. The dark gene is incompletely dominant over the white one.  The dark gene is unequally distributed across the Snow Goose’s range. Most dark-morph geese breed and winter in central areas of North America. Finally, ornithologists discovered that the two morphs’ ranges did not overlap until about 70 years ago (Mobray et al. 2000).

Monday, December 5, 2016

Chestnut-sided Warbler

I banded this Chestnut-sided Warbler this spring in Northfield. In Audubon’s time, this species was hardly ever encountered (Byers et al. 2013). An inhabitant of forest edges and secondary growth, this warbler benefited from humans’clear-cutting the continent’s old growth forests. Now it can be the most abundant breeding warbler in early succession woodlands.

Saturday, December 3, 2016

Common Green Darner

A perched Common Green Darner can be hard to see, even when you are looking right at one. This female, from last summer, was resting in the Whitetail Woods County Park in Dakota County, Minnesota.

As its name suggests, this dragonfly is common across most of North America. The species migrates south into Central America. They arrive in the north well before local dragonflies have emerged. Their migration is cued by warm fronts (DragonflyID app). After breeding, they head south, sometimes in large numbers. Common Green Darners are an important component of many bird diets, including those of American Kestrels, nighthawks, and Purple Martins.

Thursday, December 1, 2016

Purple Martin

I photographed this female Purple Martin on 13 June 2016, at Lake Byllesby Regional Park, Dakota County, Minnesota. Martins in Canada and the northern United States have a lot going against them. They depend on flying insects. Cold weather kills their insect prey, which, in turn, can wipe out local martin populations. By out-competing nesting martins, introduced starlings and House Sparrows can also wipe out these swallows.