Thursday, December 18, 2014

Band-tailed Pigeon

In the United States, Band-tailed Pigeons occur in two, non-overlapping areas. These populations are considered to be racially distinct, with one occurring from southern British Columbia through California. The other is found from Utah and Colorado south into Mexico. Banding studies show that some individuals trespass between these two ranges (Keppie and  Braun 2000). Other races occur from Mexico into South America. This photo, taken several years ago, is of a dove in the treetops above the Nisqually National Wildlife Refuge.

Band-tailed Pigions have a long nesting season—up to three nests per year—but most clutches have but one egg. Nestlings are “fed curd-like crop milk” produced by both parents. These doves descend from their foothill forests to devour wild and domestic fruits and grains (Keppie and  Braun 2000). Hunting greatly reduced Band-tailed Pigeon numbers in the early 1900s. Hunting still occurs, but this pressure no longer appears to be affecting overall population size. Nevertheless, Breeding Bird Surveys indicate this dove is "decreasing at an average annual rate of 2.8% across its North American range" (Keppie and  Braun 2000).

Tuesday, December 16, 2014

Carolina Wren

Except for posting a photo, I find I have not blogged much about Carolina Wrens. The species is abundant in the American southeast and in parts of eastern Mexico. Here in the upper midwest, this wren is casual throughout the year. I have heard its ringing “tea-kettle, tea-kettle” call once in Minnesota and I seen it a few times in South Dakota. Swanson (in Birds of South Dakota), suspects that most records in that state are the result of post-breeding dispersal by young birds from southern breeding areas.

Perhaps due to warming climate, Carolina Wrens have expanded their range north since the late 1800s. These wrens, however, do not survive cold winters. They do quickly recover from winter setbacks, as they often nest up to three times during the summer, and nests with four or five eggs are the rule (Haggerty and Morton 2014).

This photo appears to be a February 2011 shot taken at the Corkscrew Audubon Sanctuary in Florida.

Sunday, December 14, 2014

Rough-legged Hawk

Large size, black belly, white base to the tail, all indicate that this photo is of a Rough-legged Hawk. Also note the dark underwing splotches on the flying bird’s wrists. John Holden and I encountered this individual in the Burnsville (Dakota Co.) landfill on 10 December 2014. We immediately knew the hawk’s identity because of its hunting habit of hovering above the wastelands surrounding the dump. Rough-legs can be completely black to very pale—I have posted photos of a much paler individual in an earlier post in this blog.

Like the Northern Shrike, Rough-legged Hawks breed across the arctic of both northern hemispheres. In North America, they winter to the southern United States (though they are less frequently observed in the southeast). They consume lemmings, voles, ground squirrels and birds. Breeding and wintering populations fluctuate in response to density of prey populations. Ornithologists do not know if, once in a wintering area, Rough-legged Hawks stay at one location or nomadically search for new areas with abundant prey (Bechard and Swem 2002).

Saturday, December 13, 2014

Northern Shrike

John Holden and I took this photo just west of Northfield on 10 December 2014. Gray, foggy days are not really conducive for digital photography. Furthermore, birds perched on telephone wires do not usually produce very aesthetic compositions. But freezing fog combined with the wires to make this photograph of a Northern Shrike slightly more interesting than I predicted.

Elsewhere I have blogged about identifying Northern and Loggerhead shrikes. The thin black mask that does not traverse the fore-crown indicates this bird is a Northern Shrike. The bill is not as stubby as a Loggerhead's. Especially in the winter, Northern Shrikes consume many small birds and mammals, which they impale on barbed-wire, thorns, and in tree branch forks. Due to their razor-sharp bills, Northern Shrikes are one bird that I do not like to band.

Northern Shrikes are found across the Arctic areas of the Northern Hemisphere. Birds in Europe and Asia, where they are named Great Grey Shrikes, are found further south than are North American ones. Our Northern Shrikes typically move erratically in the winter only to the Central United States.

Northern Shrike systematics are murky. Within North America, ornithologists question if eastern and western races exist. Northern and Great Grey shrikes used to be treated as separate species. In any given sample of Old and New World birds, you can identify about 75% of the birds as to their origin. Does this fact indicate we are dealing with different species or just two quite variable subspecies?  Old World populations may actually represent as many as three additional species. One factor contributing to this confusion is that these shrikes are widely spread geographically, especially in their breeding range, making the collecting of meaningful samples very difficult (Cade and Atkinson 2002).

Thursday, December 11, 2014

Masked Booby

In 2012 I blogged about how eBird added a species to my list, the Nazca Booby from the Galapagos. When I saw them, Nazca Boobies were considered to be a race of the Masked Booby. In 2000, due to differing morphology and ecology, the two races were split into distinct species. Where the two species overlap, they tend not to mate with each other. Molecular evidence supports the split.

In the United States, Masked Boobies breed on the Dry Tortugas, at the end of the Florida Keys. On 15 February 2011, this was as close to the tiny island with roosting boobies as our tourist boat would approach. The captain did oblige me by slowing down, allowing me this photograph.

Tuesday, December 9, 2014

Great Black-backed Gull

On 6 December 2008, when I found the Glaucous Gull in the last post, I also photographed a number of other interesting gulls near the Black Dog power plant in Dakota Co., Minnesota. The pale head, pale, specked body, and black wing tips combine with the heavy, black bill to identify this Great Black-backed Gull. The gulls behind the Great Black-backed Gull are probably Herring Gulls, the dark one being a first year bird.

Great Black-backed Gulls are common in northeastern North America and in Europe. They winter south to the Gulf of Mexico. Feather hunters and egg collectors almost caused this species' extinction. Great Black-backs made a remarkable recovery, and by the 1960s, North American populations probably exceeded their historical numbers and now may be displacing Herring Gulls in New England breeding colonies (Good 1998).

How many gull species are flying in the bottom photograph (taken the same day as the top photo)? I think I can count Great Black-backed (upper left, lower center), Herring (right center), Thayer’s (left center), and, at the lower left, one Iceland gull. The Thayer’s and Herring differ in that the Thayer’s has a reduced amount of black on its wingtip. The Iceland is smaller than a Glaucous Gull, but like the bigger bird, has unmarked wingtips. I have commented on all of these species elsewhere in this blog.

Sunday, December 7, 2014

Glaucous Gull

Inspired by a flurry of reports of Glaucous Gulls in Minneapolis this winter, I searched for my photograph of one taken in Dakota Co., Minnesota, at the Black Dog power plant on 6 December 2008. This date was prior to my blogging career and to my eBirding. Yesterday I submitted an “historical” record to eBird, complete with this picture.

Glaucous Gulls have a circumpolar distribution. In North America, they winter south to California and Virginia. A few also winter around the Great Lakes; this gull is considered to be uncommon in the Minneapolis area. Field marks include large size, large, black-tipped bill, and pale wing tips.

Saturday, December 6, 2014

Buff-tailed Sicklebill

The fanciest bird that I found in my errant hummingbird file is this Buff-tailed Sicklebill. This species was common near Limoncocha, in Amazonian Ecuador, where Erika and I conducted our doctoral research in 1975 and 1976. We also listed the species numerous times in various parts of eastern Peru in the early 1970s. This photo was part of a project we undertook with James Yost to photograph captured birds in a parachute-lined cage.
We caught sicklebills whenever we were near this flower, which I believe is a Campanulaceae, the Bellflowers, a large family containing some 2400 species around the world. My best guess is that it is in the genus Centropogon, which is known to be favored by sicklebills (Handbook of Birds of the World—Alive). The shape of the flower suggests coevolution with the hummingbird, the oddly curved bill perfectly shaped to service the curved flower blossom.
Sicklebills also favor Heliconias, called False Bird-of-Paradise or Wild Plantains, which are closely related to bananas. Heliconias' small flowers grow in the center of long, waxy, colorful, cup-shaped bracts. Buff-tailed Sicklebills practice trap-linning, which is where an individual, rather than guarding a specific flower, visits flowers in a regular, repeating sequence (Wikipedia). I believe the flower in the last photo is Heliconia rostrata, which is known from Peru, Ecuador, Bolivia and Columbia.

Thursday, December 4, 2014

Calliope Hummingbird

Another old photo is of this Calliope Hummingbird, perched atop a pine near Missoula, Montana, on 14 June 2007. Even for the gorgeous Calliope, this gorget seems massively elongated. Why isn’t it a Costa’s Hummingbird? Well, the Costa’s is not found in Montana. Notice the white line that connects the gape to the neck—the Costa’s is dark in front of the eye. Finally, the tail is hard to see on the short-tailed Calliope Hummingbird.

Calliope Hummingbirds are North America’s smallest breeding bird. In fact, this hummingbird is the world’s smallest long-distance migrant (Calder and Calder 1994). Some individuals may migrate some 5600 miles each year between northwestern states and the southwesterm provinces, their breeding range, to southern Mexico, where they winter.

Tuesday, December 2, 2014

Broad-tailed Hummingbird

While writing my series of posts about our 2014 travels to the Southwest, I happened upon an old folder that contained hummingbird photos. I have yet to blog about a few of these species, including this Broad-tailed Hummingbird from Santa Fe on 23 May 2003 at the Randall Davey Audubon Center. The combination of the green crown and rose-red throat readily identifies this male. The proximity of males in flight also can be detected by the shrill, buzzing whistle made by the tips of their tenth primaries.

Broad-tailed hummingbirds breed in the southern Rocky Mountains, eastern California, and Mexico. At higher elevations, where they feast on wildflower nectar, they often go into torpor during chilly nights (Camfield et al. 2013). They usually avoid flowers that they have recently visited and will also take insects. Males make spectacular, swooping displays as their wings loudly buzz.