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).

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.

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. The resemblance to a dragon is astounding.

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.

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.

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.

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). 

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. 

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).

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).

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.