Nashville Warbler

A Nashville Warbler on its way after picking up a band at our banding station—you can tell by its yellow throat, white eye-ring, and barely visible white belly. This month continues to be exceptionally poor at the banding nets. Has the weather just been too good this fall for migrants to make landfall in Northfield? Did the breeding season fail in the north woods? Are this year's birds just too smart to be caught in my nets? (My nets were open about equal hours in both years.)

Here is a quick, unofficial, comparison of small birds banded at Northfield and Dundas in September 2013 and September 2012. (Please excuse the list not being in taxonomic or alphabetical order.)

September 2013 (total= 41)          September 2012 (total=140)
2 Black-and-White Warbler          17 Yellow-rumped Warbler
8 Black-capped Chickadee            19 Nashville Warbler
1 American Goldfinch                  9 Tennessee Warbler
1 Tennessee Warbler                    3 American Redstart
2 Nashville Warbler                     9 Chestnut-sided Warbler
2 American Redstart                    1 American Redstart
1 Chestnut-sided Warbler             3 Red-breasted Nuthatch
1 Golden-winged Warbler            2 Black-throated Green Warbler
1 Wilson’s Warbler                     1 Wilson’s Warbler
1 Yellow-bellied Flycatcher         1 Philadelphia Vireo
1 Common Yellowthroat             1 Magnolia Warbler
2 House Wren                            12 Red-eyed Vireo
7 Swainson’s Thrush                   7 Ovenbird
1 Downy Woodpecker                 2 Blue-headed Vireo
1 Gray-cheeked Thrush               3 Bay-breasted Warbler
5 Northern Cardinal                    1 Wilson’s Warbler
2 Ovenbird                                 1 Black-throated Blue Warbler
1 Red-eyed Vireo                        4 Canada Warbler
1 Indigo Bunting                         1 Common Yellowthroat
                                                 3 Black-capped Chickadee
                                                 1 American Goldfinch
                                                 1 Black-and-White Warbler
                                                 1 Blackburnian Warbler
                                                 1 Golden-winged Warbler
                                                 1 Wood Thrush
                                                 4 Gray Catbird
                                                 5 Northern Cardinal
                                                 1 Scarlet Tanager
                                                 1 Gray-cheeked Thrush
                                                 9 Swainson’s Thrush
                                                 2 White-breasted Nuthatch
                                                 21 American Robin
                                                 1 Red-headed Woodpecker

Caspian vs. Royal Tern

I find Caspian Terns (below) and Royal Terns (above) to be tricky to tell apart. One field mark is the bill color: orange-red in the Royal, dark red in the Caspian. The trouble is that the Caspian’s bill color can vary, especially with different lighting and depending on the bird’s age. Note the dark tip on the Caspian Tern’s bill. The crowns often distinguish the two. Royal crowns tend to be white with a narrow black band across the sides of the face. Even as juvenals, Caspian Terns do not have as much white in the crown. Breeding Royal Terns, however, have black crowns.

The situation is less confusing in North America's interior, where only Caspian Terns are normally encountered (either as breeding birds or as migrants). Royal Terns almost never stray inland, keeping instead to the coasts of the Atlantic, Gulf of Mexico, Gulf of California and southern California. The Royal Tern in this blog was photographed on Florida's Atlantic Coast; the Caspian was in costal Texas.

Ebony Jewelwing

This male Ebony Jewelwing is proclaiming his territory and trying to attract females (which have white spots on their fore-wings) by opening and closing his wings.  Males often also make courtship flights. Males guard the females with whom they have mated. Keeping track of their females may be difficult, because, according to Dubois, females are “blatantly promiscuous, mating up to five times a day and rarely with the same male."

American Goldfinch and Black-headed Siskin

John Holden and I birded near the visitor center at Faribault's River Bend Nature Center on 25 September 2013. The morning was cloudless and 60 degrees F. A flock of American Goldfinches fed at a feeder and perched on the brick building. Other goldfinches flew up, some landing on the bricks; others appeared to try to displace the perched bird. 

This behavior seemed curious, since plenty of small trees and shrubbery stood nearby. The goldfinch does not appear to be in peak health—its eyes are partially closed and its plumage appears worn and fluffed out.  On the other hand, possibly this bird and the others were sunning, a feather-maintance behavior that I have described in a recent post about robins. When this bird finally flew, its flight appeared to be normal.

Years ago, as a teenager in Chiapas, Mexico, I witnessed similar perching behavior with a Black-headed Siskin. I searched my photo files, and found the fuzzy picture below. These siskins are in the same genus as goldfinches, and are common in Mexico south to Guatemala. I wonder if both the siskin and the goldfinch used the warm bricks to rid their feathers of various parasites.

Swainson’s Thrush

I have often blogged about this common migrant—the Swainson’s Thrush. A link to a few of these posts can be found here. None of my previous photos show this thrush’s mustaches quite so comically. This species winters from Mexico through northern South America. A bird I banded on 19 May 1985 in Aberdeen, South Dakota, was recovered in Guatemala on 11 April 1988.

Saffron-winged Meadowhawk

Saffron-winged Meadowhawks are among the last meadowhawks to appear, emerging from June through October. These photos show their ovipositing in tandem over shallow water in the Straight River at the River Bend Nature Center on 13 September 2013. To guard their mates from the attentions of others, the males attach themselves to the females' necks. As you can see in the lower photo, pairs often attract other couples, “until there can be quite a crowd” (King). The female repeatedly dips her abdomen into the water, sometimes a half-dozen times, before the pair move along the shore. (The algae-covered rocks in the lower photo are all under water.)

Males can be difficult to identify, but the female’s saffron veined wings “seem to glow in the right light" (Mead). Note the female’s yellow spots (stigma) at the end of her wings. Last year I posted closeup photos of both sexes of Saffron-winged Meadowhawks.

Cape May Warbler

Cape May Warblers breed in boreal coniferous forests across Canada, dipping down to northern Minnesota, Wisconsin, Michigan and northern-most New England. They winter in the West Indies and in Central America. Alexander Wilson described this species from a specimen taken in Cape May, New Jersey. The bird was not seen there again for more than 100 years (Baltz and Latta 1998).

Over the years, I have seen Cape May Warblers numerous times, but never with a camera in my hand. The exception is this female bird I found near the Missouri River in South Dakota. The breast streaks and the yellowish color surrounding the cheek patches are the keys to identification. I have banded several fall-plumaged birds at my home in Northfield, but inexplicably I never photographed them. Surely I won’t repeat this lapse if ever I catch one of the gaudy plumaged spring males.

One problem when searching for Cape May Warblers is that this bird is a spruce budworm specialist. This warbler’s numbers explode when budworms are numerous. Between budworm outbreaks, Cape May Warblers may become extremely rare or even absent. Baltz and Latta (1998) report that the Cape May "has has a larger average clutch size than most wood-warblers [—six eggs—] which may enable it to increase rapidly during such short-term resource bonanzas.”

Wilson’s Warbler

Wilson’s Warblers, like the male I banded last week, are relatively easy to identify. Females are also fairly simple, although they are somewhat similar to a female Hooded Warbler. Female Wilson’s Warblers differ from Hoodeds in that the sides of Wilson’s faces are brighter and show more contrast with the rest of the head and Hooded Warblers show white in the tail, which is absent in the Wilson’s.

Some birders are not aware that many female Wilson’s Warblers sport black crowns. Only females in their first fall and winter lack any black in the crown. When present, the female’s black crown averages smaller than in the male. We banders measure the extent of the black crowns when we catch Wilson’s Warblers. Only birds with crowns longer than 15 mm can be safely sexed as males.

Dragonfly Eyes

The identity of this female meadowhawk eludes me. I suspect it is a White-faced, one of a trio of dragonfly species called “the troublesome three,” the females often being impossible to identify in the field (King). This photo shows dragonfly eyes.

The eyes are compound, consisting of some 28,000 photoreceptors, each with its own lens and nerve. Dragonflies can see in every direction at once, but see best where their receptors are densest. These clusters, called pseudo-pupils, are often dark. On their crowns, dragonflies also have several simple eyes that do not percieve images, but are sensitive to sudden changes in light or shadow (Taylor).

Scott King comments: "this is one place that Taylor got the facts wrong. The dorsal portion of the eye, a characteristic of many skimmers, and seen in your photograph as the maroon area on the top of the compound eye and more sensitive to short wavelengths of light, a specialization for locating prey against the blue sky. The pseudo-pupils has to do with the angle at which we are viewing the ommatidia, not their density."

Dark-form White-faced Meadowhawk

I found this meadowhawk to be perplexing to identify. This dragonfly lacked the yellow legs of an Autumn Meadowhawk and the white face of a White-faced Meadowhawk. Nothing in my books matched. Turns out to be a dark-form, female White-faced Meadowhawk. I have seen several more in this phase since Scott King helped me with this identification.

Female White-faced Meadowhawks, then, are found in three forms. The “normal” one with which I was familiar is a yellowish dragonfly. This form is in the photo below, the lower animal in a wheel formation with a red male. (I have discussed dragonfly sex in a previous blog.) Female White-faced Meadowhawks also appear as andromorphs, pale versions of their males—I blogged about andromorphs last month. You would think selective pressure would produce a single version of the females so that the males might have little trouble with recognition. Looking somewhat like a male might have advantages if the females are often harassed by males. Looking dark and nondescript might help a female avoid predation.