Saturday, May 31, 2014

Blackburnian Warbler

One of the highlights of spring migration is finding a male Blackburnian Warbler. The bird almost glows among the green foliage. On the breeding grounds, this warbler is usually found high in trees, where it forages for caterpillars. During migration they also are often found in the treetops, although this individual was netted near our water feature.

Blackburnian Warblers, like the Canada Warbler I wrote about in the last post, are threatened by tropical deforestation in their winter range. The species is less frequently seen in their breeding grounds if forests are fragmented or diseased. Nevertheless, Breeding Bird Survey data indicate their numbers are stable (Morse 2004).

Friday, May 30, 2014

Canada Warbler

Canada Warblers are late spring migrants and pass through our area early in the fall. They are faithful mates, with some individuals remaining paired for up to six years (Reitsma et al. 2010). Populations of Canada Warblers are declining about 2% a year—breeding birds suffer from loss of forest wetlands and  the secondary habitat they prefer. Canada Warblers winter along the east slope of the Andes, which are being deforested. I banded this male in late May 2014 in Northfield, Minnesota.

Thursday, May 29, 2014

Least Flycatcher

In late May, I photographed this Least Flycatcher in a field near the Cannon River Wilderness Area in Rice County, Minnesota. Although facing away from me, the bird turned its head 180 degrees, making the head appear to be attached backwards on its body.

There are a couple of odd things about Least Flycatchers. The birds, when breeding, tend to cluster their small territories. The flycatchers vigorously defend these territories against other species, such as redstarts and cowbirds. As a result, cowbirds only infrequently parasitize Least Flycatchers. Another strange thing is that Least Flycatcher adults wait to molt until after they arrive in their wintering grounds. Birds of the year molt either before they leave the breeding areas or during migration. Ornithologists do not understand this difference, but speculate that the adults need to arrive early in the wintering areas to quickly establish winter territories (Tarof and Briskie 2008).

Wednesday, May 28, 2014

Six-spotted Fishing Spider

On 25 May 2014, I was not the only predator searching for dragonflies along a small pond in Carleton College’s arboretum. This Six-spotted Fishing Spider was looking for aquatic nymphs, whereas I was more interested in flying adults. This spider is found across much of the United States and Canada to South America. This species is our most aquatic spider. It hunts along ponds and rivers and even walks on the water surface—it takes water striders or other insects that have fallen onto the water.  It also dives for its prey, which includes small fish, frogs, and aquatic insects, and can stay under water for up to an hour (Wikipedia).

Tuesday, May 27, 2014

Tennessee Warbler

Here are five Tennessee Warblers feeding on one of John Holden’s jelly feeders. This spring, Erika and I have occasionally seen these warblers at our hummingbird feeder.

In a previous post, I explained why Tennessee Warblers might be better named Coffee Warblers. In any event, numbers of these warblers tend to fluctuate greatly from year to year. These fluctuations are probably due to the species' being a Spruce Budworm specialist. When budworms are abundant, Tennessee Warblers can be the most common bird in eastern Canadian boreal forests. Thirty-year censuses, however, indicate that Tennessee Warblers enjoy stabile populations over the long term (Rimmer and Mcfarland 2012).

Monday, May 26, 2014

Baltimore Oriole

Many of our friends have feeders for Baltimore Orioles, where the birds consume massive amounts of grape jelly. We seldom attract orioles at our feeding station. On Thursday two orioles appeared at our hummingbird feeder. I can not recall seeing orioles at hummingbird feeders, and we quickly put up a jelly feeder. The orioles fed at both feeders most of the afternoon. We have not seen either bird since.

I have previously blogged about some of the Baltimore Oriole’s strange taxonomy. Males do not acquire their brilliant plumage until the fall of their second year. Until then, they resemble females. These drab, spring, second-year males do occasionally attract mates and successfully raise young (Rising and Flood 1998). Baltimore Orioles are usually seasonally monogamous.

Our orioles are in the blackbird family. They are named for their superficial resemblance to Old World Orioles, a completely different bird family. Mark Catesby named the Baltimore Oriole in 1731, calling it the “Baltimore Bird,” since orange and black were the family colors of the Baltimores of Maryland Colony.

Sunday, May 25, 2014

Magnolia Warbler

As I have previously written, the Magnolia Warbler owes its name to Alexander Wilson’s collecting the first specimen from a Mississippi magnolia tree. Considering the species’ northern breeding habitat, better names might have been Spruce Warbler or Hemlock Warbler. Magnolia is actually the bird’s scientific name and Wilson’s English name was Black-and-yellow Warbler (Dunn and Hall 2010). By any name, Magnolias are among our more strikingly beautiful warblers.

Saturday, May 24, 2014

Chestnut-sided Warbler

Chestnut-sided Warblers are now common migrants in the Northfield area. Surprisingly, in Audubon's time, naturalists almost never reported seeing this species. The populations of Chestnut-sided Warblers have greatly increased because they breed in scrubby secondary growth--the habitat that often results from regenerating logging clear cuts or from fallow fields in abandoned farmland. Byers et al. (2013) write, "the Chestnut-sided Warbler is one of the few Neotropical migrants that has benefited dramatically from human activities on the North American continent." (See also my previous post on this species.)

Friday, May 23, 2014

Scarlet Tanager

When John Holden called me on Tuesday and said that he had Scarlet Tanagers in his yard, I think he was disappointed in my relative lack of enthusiasm  I had just checked the species off on my year list. I did not know he meant he had Scarlet Tanagers at his bird feeders! Our bird trip last Wednesday was subverted as I took photos of his birds, both the male above and the female below. The birds fed on both suet (as in the third photo) and seed. The female in these photos seems to have black wings (which would make it a second-year male), but this dark color is an artifact of the photograph. The wings were actually greenish.
Scarlet Tanagers breed in the eastern United States and southeastern Canada and winter in northeastern South America. We often observed this species in the winter along the Napo River in the Ecuadorian Amazon Basin. But the biggest threat to the species is not its long-distance migration, but, rather, forest-fragmentation. As forests are felled for development and agriculture, small forest patches leave tanagers susceptable to cowbird parasitism and predators (Mobray 1999). 
As I wrote this post, Erika and I banded a another tanager, this time at our home. Try as I might, I just can’t get the camera to reproduce the intensity of this tanager’s scarlet. This last photo comes close, although I do not know from whence comes the yellow. Perhaps the yellow comes from the base of the contour feathers. At least you can easily see the “toothed” nature of the bill.

Thursday, May 22, 2014

Black-crested Titmouse

Erika and I found ourselves visiting long-time friends at their Texas retreat on 20 February 2014. They live in scrubland north of Edinburg, Texas. We had a lot of catching up to do, and spent a delightful day on their porch. We were entertained by a parade of birds at their feeders.

The first were a hoard of Black-crested Titmice. You may recall the first post I made about our trip was of a Tufted Titmouse from Oklahoma. Note the Black-crested's black crest and white forehead. Because they hybridize where their ranges overlap, the two titmice have a checkered history of being considered the same or different species. I was unaware that, these days, the two forms are considered to be separate species.

Wednesday, May 21, 2014

Pyrrhuloxia

Back to our February Texas trip. Visiting our friends at their ranch north of Edinburg. 21 February 2012. The first bird to greet us was this female Pyrrhuloxia. I have previously posted a photo of a male Pyrrhuloxia taken in south Texas in 2012.

Pyrrhuloxia are found in desert scrub in the southwest United States and northern Mexico. They are closely related to Northern Cardinals, and their calls are difficult to separate. The ranges of the two birds overlap, although Pyrrhuloxia prefer drier habitat. When breeding in the same area, the two species tend to ignore each other. One hybrid Northern Cardinal x Pyrrhuloxia has been recorded from Arizona (Tweit and Thompson 1999).

Tuesday, May 20, 2014

Harris’s Sparrow

Speaking of burned prairies, Gerry Hoekstra and I were thrilled to find a single Harris’s Sparrow in this habitat last Thursday in the Louisville Swamp Unit of the Minnesota River Valley National Wildlife Refuge in Scott County. I have previously posted on this species.

These sparrows have an oddly restricted range. They breed in the forest-tundra zone of Ontario, Manitoba, Saskatchewan and the Canadian Northwest Territories. This sparrow is the only songbird that nests only in Canada. The species enjoys a narrow winter range in the central Great Plains, from northern Nebraska and central Iowa to eastern Texas (Norment and Shackleton 2008). Elsewhere the Harris’s Sparrow is accidental.

This sparrow was collected by Thomas Nuttall in 1834. Audubon later named it after Edward Harris, who accompanied Audubon up the Missouri River to the current region of Minneapolis/St. Paul in 1843.

Monday, May 19, 2014

Cattle and Great Egret

I was busy last Wednesday in southwestern Rice County taking photos of a Great Egret (upper photo) wading right next to our car, when John Holden exclaimed, “What is that small white bird ahead of us?” “A Cattle Egret!” I replied. This egret now breeds across most the the southern United State, but it has an odd range extension in the Upper Midwest. The species breeds up through eastern North and South Dakota almost to Canada, yet remains rare in Minnesota. (I have previously written about the expansion of Cattle Egrets from Africa, though South America, to the United States.) Cattle Egrets owe their spread, at least in the Dakotas, to increasing conversion of prairie to livestock pasture.

What about the Great Egret’s lime-green face? I have previously posted notes about this breeding season affectation.

Sunday, May 18, 2014

Lark Sparrow

Lark Sparrows, like this one Gerry Hoekstra and I found at the Louisville Swamp Unit of the Minnesota River Valley National Wildlife Refuge in Scott County, often favor recently burned fields. Such was the case with this bird, found last Thursday in a recently burned prairie. Lark Sparrows also are partial to shrubby or heavily grazed pastureland. I have previously written about this species’ breeding behavior.

Saturday, May 17, 2014

Killdeer

Killdeer bathing. Water splashing. Jackson and Jackson (2000) write, "Often bathes after feeding: Sits in water, splashes water over back and wings, and then stretches wings, shaking water off.” Like the bird in the first photo.

The second photo is of another individual performing a classic Ungulate Display to lure intruders away from its nest. The Killdeer positions itself between an intruder and the nest. The the bird spreads its wings forward and lower, often beating the wings against the ground. Finally the bird fans its tail and fluffs its feathers, making the Killdeer appear larger (Jackson and Jackson 2000).

Friday, May 16, 2014

Cape May Warbler

On 13 May 2014, I finally took my first photographs of a male Cape May Warbler. Scott King and I found a pair of birds feeding on a residential street in Northfield. I have seen warblers behaving in a similar fashion before, on pavement, during cold weather after elm and other tree flowers have fallen to to the ground
Why has it taken me so long to capture the image of a male? Cape May Warblers are uncommon birds in South Dakota and, throughout their breeding range, Cape Mays are spruce worm specialists, subject to boom-or-bust population cycles. When there are few budworms, this warbler may not be seen at all. Last year must have been a banner year for budworms. In addition to this pair, I have seen another pair at a local Northfield bird feeder (where they ate grape jelly) and yesterday, 15 May 2014, Gerry Hoekstra and I counted four birds in Carver County, Minnesota.
Spring females, as you can see, are less brilliantly plumaged than the males. Note the yellow line behind her dark cheeks along the the breast streaks. I recently blogged about a South Dakota female and you can check out that post for more information on the species.

Thursday, May 15, 2014

Ruby-crowned Kinglet

This April I caught an oddly plumaged Ruby-crowned Kinglet. While I was banding the bird, I noticed its forehead and chin were black. After looking closely at the photo, you may notice that the area just behind the bill appears to be damaged, with bare skin showing. The underside of the bill on the throat was similarly wounded. Late April was at least 20 degrees cooler than average, complete with rain and snow. Kinglets fed in mossy patches at the base of trees. Possibly feeding in this fashion knocked feathers from the base of the bill at the same time depositing a sappy stain on the remaining feathers.

Wednesday, May 14, 2014

Northern Waterthrush

I have not banded many warblers this spring. Perhaps this season’s stormy weather is keeping the warblers further south. An exception is this Northern Waterthrush. Previously I blogged about identifying this species. One key is this bird’s speckled throat.

Northern Waterthrushes breed across northern Canada and winter in Central America and the Caribbean. They are common migrants over the eastern two-thirds of the United States. Despite being differently shaped (and with different behavior), waterthrushes are closely related to typical warblers. Curiously, Ovenbirds, whose silhouette is similar to that of a waterthrush, is more distantly related.

Tuesday, May 13, 2014

White-throated Sparrow

I band a good number of White-throated Sparrows during early May. The species breeds in the North Woods and winters across much of the United States. As most of my readers well know,  during migration, this sparrow is often common at local bird feeders.

Unlike the Swamp Sparrows, about which I last posted, White-throated Sparrows are one of our best-studied songbirds (Falls and Kopachena 2010). I have blogged about this species on many previous occasions. For example, see my discussion on how White-throated Sparrows come in two color morphs.

Because White-throated Sparrows are easily kept in captivity, much is known about their physiology. Between college and graduate school, Erika assisted Albert Meier of Louisiana State University in his pioneering research into the role of the hormone prolactin in White-throated Sparrow biology (see, for example, this article from Jstor). Briefly, Meier discovered temporal differences in release of prolactin and corticosteroids result in different regimes of fat storage and migratory behavior in White-throated Sparrows and other birds. Differing day length regimes trigger these different times of hormone release.

Monday, May 12, 2014

Swamp Sparrow

This stormy spring seems to be slowing migration. I did band a couple of Swamp Sparrows, a species I have written about several times in the past, including in 2011 and 2013. Mowbray (1996) writes that this species is “a common, if elusive and local resident of the eastern United States and boreal Canada.” The Swamp Sparrow’s scientific name is Melospiza georgiana, the species name referring to the state in which it was first discovered in 1790. The retiring behavior and the swampy nature of this sparrow’s habitat result in relatively little being known about the bird's natural history.

Sunday, May 11, 2014

Pectoral Sandpiper

Among the Solitary Sandpipers I reported in my last post were several Pectoral Sandpipers and a single Least Sandpiper. The Pectoral's yellow legs may confuse the unwary with Least Sandpipers or the yellowlegs. The Least is a much smaller bird (see bottom photo), and the yellowlegs are much more gray.

As I wrote in a previous post, Pectoral Sandpipers migrate from Arctic regions of North America and Siberia to the pampas of southern South America. The total mileage of this round trip is more than 18,000 miles, making this species one of the longest-distance migrants among the birds.

Saturday, May 10, 2014

Solitary Sandpiper

As we birded together on Wednesday, John Holden spied a Solitary Sandpiper in a Rice County, roadside ditch.  The photos I took did not come out to my satisfaction, so I returned the next day. At least a half-dozen of these common sandpipers fed in the area. 
The main food eaten by Solitary Sandpipers includes insects, small crustaceans, mollusks, and tadpoles (Moskoff 2011). This sandpiper often wades in puddles, delicately moving its feet to flush out aquatic prey such as mosquito larvae and midges.
Solitary Sandpipers also eat grasshoppers, caterpillars, beetles, dragonfly nymphs, caddisfly larvae, spiders, and even small sails.  Moskoff (2011) also lists worms among the Solitary's diet, and to this John and I can attest. 
One sandpiper patrolled a  water-logged, grassy field. After searching intently, in a flash, the bird speared a worm and then struggled to pull the annelid out of the ground.
The worm held on for dear life until it broke in two. (Fortunately for the worm, annelids are often able to regenerate missing halves.) The sandpiper carried the worm carcass for several seconds, before rapidly swallowing it whole.

Thursday, May 8, 2014

Tree Swallow

Tree Swallows, with their aggressive defense of artificial nesting boxes, are not always the favorite bird of bluebird enthusiasts. These swallows are, nevertheless, gorgeous birds, with their fresh plumage glistening in the sun. The pair is one of my first in 2014. One consequence of their use of nesting boxes is that Tree Swallows are among the best-studied birds in North America (Winkler et al. 2011).
The two birds here perched near a “bluebird” box. The two birds chattered and gaped at each other. Earlier I posted that one reason for swallow yawns is to strengthen their jaw muscles. Another possibility is that these are appeasement displays to calm this swallow’s aggressive nature. Throughout the breeding season, Tree Swallows are on a constant defense of their nesting sites. Substantial numbers of non-breeding males and females (non-breeding floaters) constantly attempt to take over occupied sites. The territory holders drive the intruders away. Perhaps this gaping behavior reduces aggression to one’s proper mate.

Wednesday, May 7, 2014

Barred Owls

Two Barred Owls hooted at Erika and me as we left the Cannon River Wilderness Park last Saturday. The second owl, perhaps on a nest, roosted in Northfield on Tuesday. I have previously posted on this species.

Barred Owls consume most anything that comes their way in the vicinity of their territories. They take small mammals, birds, amphibians, reptiles and even fish and invertebrates. Mammals, especially in the winter, consist of over half the diet (46-97%). Birds only make up about 6% of their prey (Mazur and James 2000).

Tuesday, May 6, 2014

Angry Rose-breasted Grosbeak

This is one angry bird. I forgot what pain a Rose-breasted Grosbeak can inflict upon a bander. Grosbeaks returned to Northfield on 4 May, and I banded this one on the fifth.

You might think that a species with such an out-sized bill might specialize on a particular, larger food item. In fact, Rose-breasted Grosbeaks are generalists when it comes to food. Wyatt and Francis (2002) cite an extensive study that found that invertebrates (beetles, bees, ants, bugs, and caterpillars) comprised 52% of their diet. Wild fruit comes in next at 19.3%, followed by weed seeds (15.7%), and cultivated crops and fruit (6.5%). Finally, some 6.5% of the diet included other vegetable matter, like tree flowers and buds and galls.

Monday, May 5, 2014

Mating Soras

I took Erika to see the Soras that John Holden and I discovered last Wednesday. We  had no trouble finding the birds. Two Soras strolled along the edge of their tiny cattail pool, one bird following the other. They ducked into the vegetation. The second bird, presumably the male, walked on top of the first. In the upper photograph, you can see the male’s toes on the female’s back. Then the pair performed a cloacal kiss, the male fluttering on the top (presumably to keep his balance), and the female raising her tail on the bottom (see second photo). I can’t imagine that too many photos exist of Soras in action.

Sunday, May 4, 2014

2014 Spring Ephemerals

Spring ephemerals are wildflowers that bloom (in Minnesota) in late April, or (during this cold spring) early May. These plants take advantage of the sunlight let onto the forest floor by the leafless trees. After the advent of the foliage, the ephemerals are gone. On Saturday, our second sunny day, we noticed Bloodroot blooming in the backyard. We hiked in the western sector of the Cannon Valley Wilderness area and found six species of spring ephemerals. I have linked each name with past posts.
Oddly, I do not seem to have a previous post on Wood Anemone, the last photo in this series. This is a poisonous wildflower, especially when consumed in quantity. Symptoms "include inflammation and blistering upon contact with freshsap and irritation of the mouth, vomiting and diarrhea following ingestion” (Lady Bird Johnson Wildflower Center). As an ephemeral, the species blooms in the early spring. Our species, Anemone quinquefolia, is closely related to the European Wood Anemone, Anemone nemorosa. Both flowers are in the buttercup family.