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.

Tuesday, November 29, 2016

Halloween Pennant

Halloween Pennant—24 July 2016—along the Jefferson Parkway Wetlands in Northfield, Minnesota. I should have posted this image on Halloween. This image lay forgotten in my blog queue. I am going to try to empty the queue during the next several weeks.

According to the DragonflyID app, this large dragonfly is common and widespread across most of the eastern United States. Minnesota is about as far north as they get. Like this one, pennants perch atop vegetation and wave in the breeze like flags. The fore and hind wings often lie on separate planes—this field mark can be seen in my photo.

Sunday, November 27, 2016

Red Fox

While we photographed the Great Gray Owl in Yellowstone Park, up trotted a Red Fox. These foxes are found from the Arctic Circle through most of North America, North Africa, and Eurasia. Their range has expended into suburban areas and they are introduced into Australia, where Red Foxes are considered to be invasive pests. They mainly take rodents, but also feed on rabbits, game birds, reptiles and invertebrates. Red Foxes are often found in pairs or in small family groups. Young remain with their parents and assist in caring for other young (Wikipedia). We, however, only saw this single fox.

Saturday, November 26, 2016

Great Gray Owl

We found the Great Gray Owl in Yellowstone National Park last September. It was not hard to spot. The poor bird was surrounded by birdwatchers. A park ranger kept vigilance over the birders. Actually this bird does not look too healthy. Hopefully it was just napping at midday. Great Grays hunt both by night and day.
The owl performed a few maintenance behaviors, like preening its legs in this second photo. I find the pine needles on the bird’s side odd. I would have thought that the owl would have cleansed itself of miscellaneous vegetation. Preening is common for this species. Stretching is another frequent behavior. I am not sure what is happening in the last picture. Several times the owl appeared to face upwards, perhaps stretching? Or trying to become invisible to the enthusiastic birders?

Thursday, November 24, 2016

Rocky Mountain Elk

Yellowstone National Park is a good place to see Rocky Mountain Elk. Elk were once found across much of North America, but their range is now greatly contracted. 

The elk in this photo is a female. Females and young live in herds. Males either live alone or in groups of batchlors. During rutting season, females and young will move into harems with one or two males. Males coat themselves with urine-soaked mud, which attracts the females. I did not notice it at the time, but this female is urinating. This behavior is probably not marking territory, and no more complicated than it seems. (As we raced across Yellowstone in search of the Great Gray Owl, this photo is the only elk image I captured.)

Tuesday, November 22, 2016

Bison and Magpie

Look closely at this Bison from Yellowstone National Park. A Black-billed Magpie is perched on its head. Magpies form symbiotic relationships with large ungulates. The magpie feeds on ticks and other ectoparasties. The advantage to the bison is obvious, but the situation may be more complicated. Magpies cache the ticks for later consumption, but often don’t kill the ticks first. If the ticks survive, they reproduce, thus increasing tick numbers. For the bison, tick borne illnesses and outright blood loss from tick wounds can cause deaths. Magpies feast on the bison carcasses, and both carcasses and ticks are probably critical food sources for the birds (Trost 1999).

In yet another twist, I have been told that ranchers often treat cattle with poisons to kill ticks. If their cattle die from other causes, the poisons sometimes collaterally kill scavengers like magpies and Golden Eagles.

Magpies are omnivorous, consuming grains, vegetable matter, and both living and dead animals. Magpies cache food for only a couple of days. Often their caches are stolen by other magpies, that find the caches by smell. Female magpies watch males cache food and later steal the males’ hoard. Males will often move caches away from carcasses on which they feed and take the food closer to their nests. Magpies cache whatever food is most abundant. Both wild and pet magpies also cache shiny trash.

Sunday, November 20, 2016

Greater White-fronted Goose

On 16 November, John Holden and I checked out the New Prague, Minnesota, sewage treatment ponds. This location often harbors migrating waterfowl, and this day was no exception. Nearby, among a large flock of loafing Canada Geese, we spied a solitary Greater White-fronted Goose.

White-fronted Geese breed in arctic regions around the the world. They migrate over much of Canada and the United States, and winter in California, the Southeast, and in Mexico. In our country, it is most common west of the Mississippi River. The numbers of this goose have fluctuated greatly since the early 1950s, declining from over-hunting and habitat destruction (Ely and Dzubin 1994). Nevertheless, over a million birds inhabited North America in 1994.