Tuesday, March 3, 2015

House Finch

Here are a male and female House Finch at the feeder last Saturday. It is hard to remember that this species, now one of the most numerous birds across the United States, southern Canada, and Mexico, was unknown in the East before 1939. Then caged birds either escaped or were released from a New York City pet store. They quickly expanded their range across the continent. Curiously, at the same time, House Finches expanded out of their desert southwestern range. Although a House Finch thought to be an escaped cage bird was discovered in Minneapolis in 1896, birds from the current expansion appeared in the state in the early 1980s (Janssen 1987).

In 1994, House Finches were super abundant across the country and found in almost every conceivable habitat. Then the species was struck by an outbreak of mycoplasmosis, a bacteria that formed grotesque pustules around finch eyes, bills, and feet.  Several species of mycoplasma bacteria also attack poultry, causing serious respiratory infections. Others infect people, resulting in pneumonia and pelvic inflammation. We bird banders were never thrilled to handle infected House Finches. Banding recoveries, however, demonstrate that the disease is not invariably fatal to birds.

Millions of House Finches died, and, in some areas, local populations disappeared. This disease has been called one of the “worst epizootics in history” (Badyaev et al. 2012). Other species, like goldfinches, occasionally showed symptoms, but not with the same devastating destruction of populations. One hypothesis is that eastern House Finches, since they originated from those few New York birds, were genetically less robust than western birds, and, thus, were exceptionally susceptible to the bacteria. Genetic studies demonstrate western birds do, indeed, have significantly greater genetic diversity than eastern ones.

Saturday, February 28, 2015

Dunlin

A basic-plumaged Dunlin can be a difficult bird to identify. Birders pay attention to the relatively long, slightly down-curved bill. Sometimes they are confused with the smaller and streakier Western Sandpiper.

Across their huge, circumpolar range, Dunlin have evolved into about nine subspecies. Ornithologists debate the number that occur in North America. Many scientists say one species breeds here, others recognize two or three. Genetic studies indicate two races exist, Pacific Dunlin breeding in western and northern Alaska, and Hudsonian Dunlin across Northern Canada. These breeding birds differ in size (Canadian birds being the largest), their backs’ brightness and their undertail covert’s streaking.

Pacific Dunlin winter from southern Alaska south along the Pacific Coast at least through Mexico. Hudsonian Dunlin winter along the Gulf Coast and eastern Mexico south South America (although the race of Latin American birds is often not determined (Warnock and Gill 1996). Based solely on range, the bird in this post is probably a Pacific Dunlin, since this photo was taken at Westport, Washington, along a Pacific beach.

Thursday, February 26, 2015

Snowy American Crow

This cold and snowy American Crow huddled above the bird feeder on Wednesday morning. Look at the ice on its head, eyes, and back. Finally it dropped down and fed on scraps below the feeders. I have previously blogged on crows—you can search for these posts by using the search-box in the right column on this page. After you search once, remember to return to the whole blog before performing a second search.

A a few physiological adaptations allow crows to survive Minnesota winters. In warm weather, crows keep their body temperature near 40 degrees C (104 F).  In colder weather, crows are able to reduce their body temperatures as low as 38 degrees C (100.4 F). Obviously this plasticity saves energy. Their large size results in a relatively low surface to body mass ratio, also resulting in relatively lower heat loss (Verbeek and Caffery 2002). Finally, notice that, like many chilly birds, this crow has fluffed out its feathers, creating warm spaces near its body.

Monday, February 23, 2015

Common Goldeneye

Female birds often get a short shrift in art and photography. I was surprised that I have very few decent photos of Common Goldeneyes of either sex, and this one is my only closeup of a hen. The females can be difficult to tell apart from the similar Barrow’s Goldeneye, but the Common can be recognized by their larger bills usually being more black than yellow. A few of my other photos of both species can be found in this previous post. I took this photo several years ago in Duluth, Minnesota.

Saturday, February 21, 2015

Sharp-shinned Hawk

On Friday morning, Erika and I were reading in our sunroom, which looks out at our bird feeders. Suddenly a small Accipiter swooped around the feeders, narrowly missing our picture window, and perched on an overhanging tree branch. Its square-ended tail feathers indicate Sharp-shinned Hawk. The small size probably means it is a male. The iris color, between yellow and orange, signifies a second-year bird. The good news is that I had my camera on the table in front of me. Unfortunately this gray day was not ideal for photography. After a couple of minutes, the hawk launched itself back towards the empty feeders, banking sideways, with its feet towards the feeders, and disappeared into the woods.

Sharp-shinned Hawks are renown for consuming small birds. This species often takes songbirds at bird feeders (Bildstein and Meyer 2000). These authors cite studies that show birds comprised 91 to 100 percent of Sharp-shinned diets in various samples around the country. Mammalian prey, however, sometimes made up a greater mass of the diet than did birds, especially late in the breeding season.

Thursday, February 19, 2015

California Gull

The top two photographs are of California Gulls. The species breeds in western, interior North America. The eastern-most breeding colonies are in the Dakotas, Colorado, and Manitoba. Most of these gulls winter along the Pacific Coast, from British Columbia south to central Mexico. Only a few winter in the continent’s interior. Wintering coastal populations are interesting because they appear to slowly drift southward during the winter, with juveniles dispersing the longest distances. Off the coast of Washington, adults are normally found close to shore, presumably forcing younger birds out to sea.

As birders become better at identifying gulls, California Gulls are being reported with increasing frequency from the Great Lake, the Mississippi River, and the Gulf Coast (Winkler 1996). Most of these out-of-range birds are expected to be immatures, like the bird in the first photo. The young birds have dark-tipped and relatively thin, pinkish bills. Adults’ bills are also relatively narrow bills with black and red spots on them (see middle photo).
I took the last gull photo a couple of years ago in Duluth, Minnesota. I was perplexed, because this gull’s bill looks “spot-on” for a California Gull. I noticed, however, that the legs were the wrong color—pink instead of gray and the back was too pale for a California Gull (also note the difference in iris color).  Turns out that, not only do young Herring Gulls often have black and red spots on their bills, banding studies show that even older adults often retain black bills spots David Bell (pers. com.). The moral of this blog post is to be careful when identifying out-of-range California Gulls.

Tuesday, February 17, 2015

Glaucous-winged Gull

Recently I blogged about “Olympic” Gulls, the hybrid swarm between Western and Glaucous-winged Gulls breeding around Puget Sound, Washington. Previously I posted notes about Western and Glaucous-winged species, but I have only a few photographs of the later.  This photo is of an immature bird. These gulls breed along the Pacific Coast from Alaska to the Olympic Peninsula. They winter from there to Baja California and the Gulf of California.

In recent years, populations of Glaucous-winged Gulls have greatly increased. Apparently this trend is in response to increasing supplies of human garbage and fish offal.  Declines in Bald Eagle numbers may have contributed gull increases—with fewer eagles, more dead fish are available to the gulls. With Bald Eagle numbers recovering, some populations of Glaucous-winged Gulls are declining (Hayward and Verbeek 2008).

Sunday, February 15, 2015

Red Squirrel

Another creature that crossed my path during Sunday's stroll in the Carleton College arboretum was this Red Squirrel.  I have written twice previously on this species—you may recall that Red Squirrels do not hibernate, though they may be inactive during ugly weather. This squirrel watched me fidget with my camera, only fleeing just before I remembered to try to use my flash attachment. The squirrel held on to a Black Walnut fruit that it had probably cached in the fall.

Friday, February 13, 2015

Canada Goose

On Sunday, one hundred Canada Geese loitered along the Cannon River in Carleton College’s arboretum.  I took a photo for BirdsEye.com.  This bird stood on one foot, but, after ruffling its feathers, walked to the water on both feet.  I believe these geese were small Canada Geese rather than large Cackling Geese, which would have sported shorter bills.  

Canadas are the most abundant of North American geese. They are monogamous and form life-long pairs.  During the first year, offspring remain with parents. In many areas, increases in breeding populations have mixed migrants and local birds. The result has been a confusing mixture of genes and general genetic chaos among flock members.  Flocks have become so large, that they become a nuisance in many urban areas. Over 27,000, for example, have been reported from Minneapolis (Mobray et al. 2002).

Wednesday, February 11, 2015

Mallard

On Sunday, I finally got out with camera in hand this cold, gray Febraury.  I did not see much of note in the Carleton College arboretum. I did photograph several of the hundred Mallards loafing along open water along the Cannon River. My goal was to get a few shots with the dimensions preferred by BirdsEye.photo.
The mallard is North America’s most abundant duck, breeding across most of Canada and the United States. The species is adaptable in its habitat preferences and will eat a wide variety of food items. It is cold-hearty, and will winter as far north as open water persists. Despite being heavily taken by sport-hunters, populations remain steady (Drilling et al. 2002).