Wednesday, May 31, 2017

Ruby-throated Hummingbird

Ruby-throated Hummingbirds are visiting our sugar-water feeder. These hummingbirds breed across eastern North America and winter in Central America. A few winter in southern Florida and southern Texas.

Females, like this one, are slightly larger than males (3.5 vs. 3 grams). Despite their size, many Ruby-throated Hummingbirds migrate nonstop across the Gulf of Mexico. Prior to this flight, birds may double their body mass by fattening on nectar and insects. Little is known, however, about the details of their migration. Ornithologists do not know much about the relative numbers of hummingbirds making trans-gulf migrations versus those that go around the gulf. Nor do we understand regional routes or precise wintering areas (Weidensaul et al. 2013).

Tuesday, May 30, 2017

Common Whitetail

This past week, I made several unsuccessful jaunts looking for Southern Spreadwings. On 24 May along the Big Pond at St Olaf College, Erika and I photographed a strange dragonfly. Thanks to Scott King, we identified it as a young, female Common Whitetail. This species is often abundant in Erika’s garden. We have never seen one, however, with white rays in its wing like this one. Scott explained that recently emerged dragonflies often take several days to acquire their adult appearance. One hardly needs to wonder why dragonfly identification is so difficult.

Monday, May 29, 2017

Horned Clubtail

On 25 May 2017, Scott King and I surveyed a pond at the River Bend Nature Center. We were successful in our hunt for Horned Clubtails. Even as we searched, these dragonflies were hauling themselves on to algae mats in the pond, casting aside their exuvia, and inflating and hardening their wings.

According to Paulson, males remain near ponds. They often perch on the ground or on other flat surfaces. Females, on the other hand, tend to retire to high woodland leaves. The males, when disturbed, encounter the females in their woodland habitat.

Sunday, May 28, 2017

Dot-tailed Whiteface Explosion

On 25 May 2017, Scott King and I surveyed a pond at the River Bend Nature Center near Faribault. His goal was to record Horned Clubtails. I wanted to see a Southern Spreadwing. We discovered clouds of emerging Dot-tailed Whiteface. Over a thousand flew up from the sedges in the pond and a nearby grassy field. 
The first photo shows an exuvia left by a Dot-tailed Whiteface. An exuvia is the cast-off skin of a larval insect, in this case dragonfly. Some insects eat their exuviae, but others leave them behind. The second image is of a teneral Dot-tailed Whiteface perched next to its exuvia. Teneral dragonflies are soft, recently emerged dragonflies. Their colors are often muted and their wings shiny. If they can fly, they often do so poorly. Some teneral individuals have undeveloped wings.
Adult Dot-tailed Whiteface were also abundant at the pond. The photo above is of a male. You can easily see why it is named Dot-tailed Whiteface. Females, like the one below, are handsome dragonflies. They also sport white faces.
This day was one of the first truly warm days of the spring. Temperatures exceeded 80 degrees F. Whitefaces must develop rapidly. Already a few flew in a wheel-shaped wheel position over the pond. The male holds on to the back of the female’s head, preventing competing males access to her. The male then transfers sperm from his genitals at the end of his abdomen to a sperm holding pouch, his seminal vesicle, near the front of his abdomen. The female attaches her abdomen end here and collects the sperm in her abdominal pouches. Males may continue to guard their mates or the males may fly off. Competing males, upon mating with a female, are likely to flush out her seminal pouches. Females can carry sperm from a single mating for the remainder of their lives, fertilizing their eggs when suitable habitat is encountered.

Saturday, May 27, 2017

Bobolink

On 19 May 2016, I drove out to Cody Lake in search of Bobolinks. Here is a different prospective of the single Bobolink I found, taken out Erika’s car sunroof. The Bobolink’s strange plumage, black below and pale or white above, results in the bird’s being sometimes called Skunk Blackbird (Renfrew et al. 2015). Many birds exhibit countershading, light below and darker above. This pattern tends to flatten the bird and makes it harder for predators to see them. Presumably the Bobolinks’ reverse countershading makes the males more visible to potential mates. In nonbreeding plumages, the males molt into a brown, streaky pattern similar to the females.

Friday, May 26, 2017

Northern Waterthrush

On 22 May 2017, we banded a Northern Waterthrush. The two waterthrush species, Northern and Louisiana, can be tricky to identify. Northerns, however, almost always have speckled throats.

The Northern Waterthrush is fairly secure in its breeding range, which stretches from Alaska to eastern Canada south to the northernmost United States. In its Latin American winter range, however, destruction of mangrove forests threaten this waterthrush (Whitaker and Eaton 2014). 

Wednesday, May 24, 2017

House Wren

Male House Wrens, when seeking mates, often sing from high, exposed perches. Once nesting, the males sing much closer to the ground. We found this bird in the Carleton College arboretum here in Rice County on 22 May 2017. 

Tuesday, May 23, 2017

Pectoral Sandpiper

On 11 May 2017, I also found several Pectoral Sandpipers at the Bridgewater Township flood control pond just south of Northfield. This pond is named Central Pond, because it drains several smaller upstream pools.

Pectoral Sandpipers are another long-distance migrant. They breed in the high Arctic and winter in the Argentine pampas. Individuals may make 30,000 km round-trip journeys, placing them among the longest migrating species in the world (Farmer et al. 2013).

Monday, May 22, 2017

Least Sandpiper

Another shorebird on11 May 2017 at the Bridgewater Township flood control pond just south of Northfield. Note the dark breast and rich, brown back. The small size and yellow legs cinch identification as a Least Sandpiper.

These common shorebirds breed across arctic regions of North America. They winter from the United States to northern South America. Eastern populations make non-stop, 4000 km flights from New England to Venezuela (Nebel and Cooper 2008).

Sunday, May 21, 2017

Semipalmated Plover

Bridgewater Township just completed a flood control pond just south of Northfield. The muddy shores attracted migrating shorebirds, like this Semipalmated Plover on 11 May. Unlike other shorebirds, numbers of this plover appear to be stable. Reasons for this status include the bird’s not being picky about its habitat or its diet. It also enjoys an extremely wide winter range, being found on the coasts of North and South America, which allows it to survive areas of local habitat destruction.

Saturday, May 20, 2017

Chestnut-sided Warbler

Once again home, on 12 May 2017, I banded this male Chestnut-sided Warbler. As I have written several times in this blog, this warbler went almost unreported by early ornithologists. Now it is one of the most common warblers, breeding in disturbed secondary growth left over by human development. The species breeds across eastern Canada and the northeastern United States. This warbler also nests south to Georgia in the Appalachians. Isolated populations are found in southern Illinois, Missouri, Arkansas, and eastern Iowa. In Minnesota, most breed in northern counties.

Friday, May 19, 2017

White-crowned Sparrow

The only other bird of passing interest that we photographed during our quick trip east was on 8 May at a rest area along I-74 in Woodford County, Illinois. Four races of White-crowned Sparrows are known. Two are found along the West Coast. The other two are seen across North America. The race leucophrys, is generally found further east than gambelii. Several field marks separate these subspecies. The major one is the color of the male's lores, the area between their eye and the crown stripe. This area is black in leucophrys, but gray in gambelii. In areas of overlap between the two races around the Hudson Bay, intermediate-plumaged individuals are sometimes encountered. The bird in this photo is clearly leucophrys.

Thursday, May 18, 2017

Fragile Forktail

The evening of May 3, 2017 found us parking in front of a motel near Fremont, Indiana. To our delight, a small damselfly landed on the car trunk—a ready-made white background. The Fragile Forktail’s scientific name is Ischnura posita. Ischnura refers to this ode’s small size. The species name, posita, alludes to the exclamation mark on the top of the male’s thorax (Paulson and Eunkle 2016).

Despite this species being new to us, it is common and widespread across eastern North America, south through Mexico to northern Central America. A few Minnesota records exist. Fragile Forktails were introduced to Hawaii in 1936 and is now found on all but one of the major islands.

Wednesday, May 17, 2017

Eastern Forktail

Eastern Forktails are among the most common damselflies in eastern North America. They are one of the first to imerge in the spring, and one of the last to disappear in the fall. We found this individual on 3 May 2017 at the Independence Grove Forest Preserve near Libertyville, Illinois. I am left a bit confused by this damsel’s brownish thorax, but the blue abdomen tip, with its two downward-pointing bars, is typical of this species. Perhaps this individual is a young forktail.

Tuesday, May 16, 2017

Red-winged Blackbird

During the first week of May, we made a non-birding drive to New Jersey to attend to family matters. Our best day was 3 May 2017 at the Independence Grove Forest Preserve near Libertyville, Illinois. We searched for dragonflies.  Mostly we saw Red-winged Blackbirds (like this female). In the summer, the species is mostly insectivorous, sometimes completely so (Yasukawa and Searcy 1995). Perhaps the blackbirds’ abundance is one reason we saw only one dragonfly.

We only saw two damselflies during our journey. Most days, however, were chilly, windy and rainy. The weather greatly diminished our wildlife photography for the rest of the trip. But, as I wrote, this was a non-birding trip.

Monday, May 15, 2017

American Redstart

This bird is a second-year, male American Restart. Elsewhere I have blogged about this warbler's plumage sequences. The fine “whiskers” around a redstart’s mouth may help catch the small arthropods that this warbler grabs from the air, or the bristles may protect the bird’s eyes from their prey, I found the orange wing stripe of this redstart to be stunning. American Redstarts are abundant, but suffer from habitat fragmentation and other forms of human urbanization. Gruson writes that the word redstart is a corruption of the Old German “rothstert,” meaning red-tail.

Sunday, May 14, 2017

Northern Parula

This Northern Parula is yet another of the warblers in our yard on 10 May 2017. Early ornithologists named this bird the Blue Yellow-backed Warbler. Paula means small bird or little titmouse.

The bird breeds across eastern North America, with a gap between northern and southern populations. Northern birds build nests of Beard Moss, while southern ones use Spanish Moss. Eastern and western populations, on the other hand, differ in song patterns. 

Friday, May 12, 2017

Golden-winged Warbler

Golden-winged Warbler, another striking bird in the backyard on 10 May 2017. I have written about this fascinating species many times before in this blog. This species’ range has expanded into New England during the last century. Elsewhere, however, populations are declining, even disappearing. Several factors may be involved in the decline. Their secondary growth habitat is being replaced by more mature forests. As Blue-winged Warblers also enjoy a northward range expansion, they appear to out-compete and replace Golden-wings. Finally habitat destruction in Latin America probably contributes to the decline of the Golden-winged Warbler (Confer et al. 2011).

Thursday, May 11, 2017

Magnolia Warbler

A non-birding trip for family matters pulled us away from Minnesota for the first week of May. Upon our return on 9 May, I restarted the water feature and opened my banding nets. Today, on the 10th, we enjoyed a relatively large warbler migration.

Roger Tory Peterson described warblers as “the butterflies of the bird world.” The male Magnolia Warbler is one of the most beautiful. The bird breeds in boreal forests of Canada and northern-most United States. Winter is spent in Central America and  in Caribbean islands.

Alexander Wilson collected the first specimen of this species from a Mississippi magnolia in 1810. You might think that ornithologists could come up with a better name. In fact, although giving the Magnolia Warbler its scientific name of magnolia, he called it the Black-and-Yellow Warbler (Dunn and Hall 2010).

Tuesday, May 9, 2017

Nashville Warbler

I banded this adult Nashville Warbler last spring. The rufous crown patch is hard to see in the field, making it easy to confuse this warbler with other species. Nashville Warblers are common breeders across much of North America. These birds prefer second-growth habitats, such as occur after farms are abandoned or forests are clearcut.

Sunday, May 7, 2017

Killdeer

Killdeer get their name from their raucous calls. In the 18th century, these shorebirds went by the names of Chattering or Noisy plover. Killdeer were shot by market hunters in the 1800s, and were, in those years, in decline. Now they are common, benefiting  from human changes to the environment. They are attracted to mudflats, meadows, construction sites, gravel roads, lawns, pastures and golf courses (Jackson and Jackson 2000). The species is famous for its broken wing and tail distraction behaviors. On 28 April at the University of Minnesota Landscape Arboretum, I must have been near a nest. This Killdeer patiently led me in the opposite direction.

Friday, May 5, 2017

White-throated Sparrow


I found a small flock of White-throated Sparrows on 28 April at the University of Minnesota Landscape Arboretum. These sparrows are common migrants in our part of the state. A search of my blog will reveal several previous posts with discussions of White-throated Sparrow plumages and songs.

Based on genetic evidence, White-throated Sparrows and other birds in their genus are most closely related to Juncos. Morphologically this conclusion may seem surprising, but hybrids between the two genera are reported. Within their genus, White-throated Sparrows diverged from White-crowned and Golden-crowned sparrows about 750,000 years ago. Still earlier, some 1.2 million years ago, the ancestors of these three species diverged from Harris’s Sparrows (Falls and Kopachena 2010).

Wednesday, May 3, 2017

Purple Finch

On 21 April 2017 I banded this Purple Finch in our backyard. Male Purple Finches take two years to acquire their merlot-colored plumage. A brown individual, therefore, may be either a female or a first or second-year male.

Purple Finches undergo “quasicyclical” irruptions (Wootton 1996). I am not sure what quasicyclical means—not in my dictionary. I think it means that their movements, presumably dependent on conifer seed production in their breeding areas, are unpredictable. Wootton writes, “Although widespread and regularly seen, this bird is one of the least-studied finches in North America because it is neither common enough to be easily studied nor rare enough to be threatened with extinction."

Monday, May 1, 2017

Palm Warbler

 
Like Yellow-rumped Warblers, Palm Warblers winter along our southeastern coasts. Thus they are one of the first warblers here in Minnesota. In Canada and the northern United States, this warbler breeds in bogs and fens. The bird owes its name to its being discovered in Hispaniola, where palm trees are more common than in northern swamps. 
Unlike most of our warblers, Palm Warblers often feed on the ground. Males and females have similar plumage.The first two birds fed among dandelions in a freshly cut lawn at the University of Minnesota Landscape Arboretum on 28 April 2017. Note that Yellow-rumped Warblers are not the only bird with a yellowish rump. The third photo is one left over from last year, taken at the River Bend Nature Center on 14 May 2016.