Luecistic Tree Swallow

While birding in Rice County on Wednesday, I found swallows beginning to flock on local power-lines. One of these birds, a Tree Swallow, sported a white cap reminiscent of a South American White-capped Dipper. Clearly this individual is aberrant, a leucistic bird. Partial leucism, like on this swallow, occurs when pigment production is blocked and the result is a bird with white and normal patches. Leucistic birds generally show normally colored eyes, whereas albinos have pink eyes. Also notice the white bands on the edges of this swallow’s scapulars.

Note this bird's frayed flight feathers. Perhaps more than leucism is affecting these feathers, resulting in weak feather structure. Although I have no evidence in this case, another possibility is that other Tree Swallows have been harassing this bird. Leucistic Barn Swallows are known to be attacked by their fellow flock members (Brown and Brown 1999). Swallows can be extremely aggressive. Tree Swallows are known to kill their “step children,” when a male mates with a recently “widowed” female (Winkler et al. 2011),

Shadow Darner

Monday, the fall banding season began not with a bird, but with a dragonfly. Odonates are difficult to remove from the bird nets. But, once untangled, having the critter in hand makes for close inspection. I should go into the field with a net. Perhaps I could drag a wagon behind me with all the equipment I would need for birding, dragonflying and banding.

The prominent throacic stripes and relatively unbanded abdomen suggested a Shadow Darner. The clincher, however, is the spine on the lower part of the long claspers at the end of the abdomen (see bottom photo). So add a hand lens to that wagon!

This is my second Shadow Darner—see post of 30 August 2011. There I wrote about this species’ adaptations to cool weather—definitely NOT a problem this year. I caught this year’s Shadow Darner, nevertheless, first thing in the morning, before the heat of the day. The darner flew across a forest opening, which happened to contain my banding net. 

Blackburnian Warbler

The end of August brings the first autumn migrants. The fall is my favorite season. The migrants, although definitely difficult to identify, are more plentiful than in the spring. Their numbers are augmented by the new hatch of young. Yesterday we banded a very drab, immature Blackburnian Warbler—quite a difference from a spring bird! Note the dark cheeks that are surrounded by yellow and the prominent white wing bars. Other warblers caught in the last two days include American Redstart, Wilson’s Warbler, and Northern Waterthrush.

Shooting Star

Dodecatheon is another genus of wildflower that depends on bee pollination. The bees hold on to the petals and gather pollen by shaking the flowers by buzzing their wings (Wikipedia). What appear to be backward-facing petals on these flowers are actually sepals.

This photo is of one of 14 species in the genus, which is found in North America and northeastern Siberia. This species is Dodecatheon puchellum, often called Pretty Shooting Star or Dark-throated Shooting Star. The species is found across most of western North America, probably south into Mexico. This photo was taken in the Black Hills of South Dakota.

Plants are found in dry soil and need at least three years to bloom. Plants can be propagated by division in winter. Some Native American tribes used Shooting Stars medicinally—as an eye wash, and a throat gargle.

Fairy Slipper

Perhaps the ice in the photo of a Fairy Slipper orchid that attracts me on this blazing hot August afternoon. As I write, temperatures are at a near record-breaking 93 degrees with high humidity. I took this photo on a chilly May day four years ago near Missoula, Montana. This orchid is also called Calypso, for its genus.

Fairy Slippers are found across the northern hemisphere, from North America, across Scandinavia, Russia, eastern Siberia and Japan. In the United States, they grow in the Rocky Mountains into the southwest. Despite this wide range, Fairy Slippers are often classified as endangered plants. They are intolerant of disturbance and are short-lived. They do not transplant well as the require specific soil fungi to flourish (Wikipedia).

The pollination of these ochids depend on specific bumblebees. The bees are fooled by the flowers, which attract the bees, but produce no nectar. The bees learn this trick and do not visit the same flowers twice, to the genetic benefit of the orchids. This deception may be the origin of this orchid’s genus, Calypso, from the Greek, meaning to hide or deceive; or the name may refer to Calypso, the daughter of gods, who kidnaped Odysseus for seven years, hoping to keep him as her immortal husband. 

If the present decline of bees noted across the world continues, Fairy Slippers are yet another plant in peril.

Robber Fly 2

Camera in hand, I was sitting on the back porch, when up flew an odd-looking fly. I sent the photograph to my local entomologist, Scott King, who identified it as a robber fly, probably Machimus notatus. This identification is based on the black, rather than yellow, tibia (the first long segment) of the hind leg. I have previously posted on robber flies, though this one looks quite different from the last.

Sometimes called assassin flies, these bugs are fierce predators, taking a wide variety of arthropods, even dragonflies. They perch on low plants and attack prey in the air. These flies stab their victims with their proboscis, and inject neurotoxins and enzymes that liquify the prey’s insides. The insides are then sucked up by the robber fly.

Robber flies are not considered to be pests, unless they are feeding on bees. They can inflict a painful bite on people who handle them. Their larvae live in rotting wood and in soil.

Albino Ring-billed Gull

Gulls are hard to identify. Many take three or four years to attain adult plumage, with different patterns in each year. Gulls often show a lot of individual variation. Complicating matters is the rare but regular occurrence of albino and leucistic birds. I believe this photo, taken many years ago in Pierre, South Dakota, is an example of a leucistic bird (an albino would probably lack the dark bill tip). A normal bird in one of its first or second winter plumages would probably be dusky and show black wing tips. A dark terminal tail band is usually present.

Great Blue Heron

Herons and cranes are usually identified by their flight silhouettes. Cranes fly with their necks extended, while herons fly with their necks folded in an S-shape. As you can see in this photo taken in Dakota County, Minnesota, this rule is not invariable. Great Blue Herons, when they are landing, chasing other herons, fleeing from predators, or courting, often fly with extended necks. This heron was landing in a nearby marsh.

Black Swallowtail

Black Swallowtails are common across much of eastern North America. Erika and I encountered this one in the Carleton College arboretum. These butterflies lay their eggs on plants related to carrots (Queen Anne’s Lace, carrot, celery, parsley and dill). Planting dill in your garden is a good way to attract the species. Females lay singe eggs on the leaves or flowers of the host plants. Upon hatching, their caterpillars feed on these same plants. Adult food includes Red Clover, milkweed, and thistles (butterfliesandmoths.org). Some confusion exists in the literature as to whether Black Swallowtails accumulate toxins from the plants that they eat (and are thus bad tasting or toxic to their predators) or if this species mimics similar appearing butterflies that are toxic to predators. Perhaps both statements are true, in which case Black Swallowtails are examples of Mullerian mimicry, wherein two or more toxic species look similar so as to lower predators’ learning curves.

Eastern Amberwing

I previously blogged about dragonfly sex. Eastern Amberwings are a bit different. The spotted-winged females, like the one above, often oviposit (lay their eggs) unguarded by their mates. In this case, however, at Carleton College’s Lyman Lakes, did her egg laying within a short distance of a territory holding male (lower photo). Males often establish territories around good egg laying sites. The enjoy a brief copulation (about 17 seconds) before leading his mate to the laying site.  Females may tap the water surface up to 100 times, facing different directions as they lay. Meanwhile the males may “take other males in tandem, perhaps to keep them from mating with [the] nearby female” (Paulson).