8-14 March 2007

Installment #351---
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One morning this week while we worked at our desk in the old farmhouse at Hilton Pond Center, a loud, dull thud caught our attention. It sounded as if a good-sized bird had flown into one of the large office windows that overlooks the pond itself--something that occasionally happens, especially when a Sharp-shinned Hawk takes aim at our backyard feeders. We immediately went out onto the deck to look for a stunned bird but found none--not even a loose feather--which meant any avian perpetrator of the sound likely survived, albeit with a bit of a headache. We didn't think much more about the incident until next day when we were back out on the deck looking in. Right in front of us on the window glass was the perfect, ghostly silhouette of a bird with outstretched wings (below). We concluded this must be the image of the bird that hit our window the day before.

All text & photos © Hilton Pond Center

The outline was barely visible in bright sunshine, but when we stood at just the right angle and placed black paper behind the glass there was no mistaking this eerie image was made by a bird in full flight. We suspected the artifact was formed by "powder down" or by feather dander--white matter stuck to the glass by oil the bird uses to waterproof and condition its feathers when preening. Hard to see, the image was even more difficult to catch through the camera lens, but we gave it a try and came up with three photos.

The impression left by the bird was stunning. In it we could see how the tips of the wings curved gracefully upward, with the lead edge of the front-most primary feather making the heaviest mark. Following the wing curve toward the body, we also saw a shorter bright line formed by the bird's wrist bone and hand against the window pane. Just above that was a short curved line pointing up at a 45-degree angle; this was the edge of the alular feather. The bright spots closest to the body looked a little like headlights and must have been made by the big joint where the humerus meets the ulna/radius.

While the image as a whole was graceful and ghost-like, a close-up of the body section (above) was surrealistic; it reminded us of the famous Shroud of Turin. The bottom half clearly showed imprints of the edges of breast feathers, and a large bright spot just above them was caused by impact from the bird's keel, its breastbone. The top half seems to show the bird hit the window with its bill straight ahead, the impact forcing the head to turn straight downward and roll against the glass--leaving a wide, smeared streak. We could see the outline of the bill itself at the bottom of the smear, and darker areas to either side that were likely the area around the eyes. The long, thin, crooked line that seems to arise near the tip of the bill was confusing, but may be from saliva ejected when the bird hit the glass. (We doubt it was the bird's tongue.)

We were absolutely fascinated by this spooky souvenir and zoomed in even closer on the section formed by breast feathers (above). In macro view this part of the image becomes a white-on-black abstract--short, curved lines that form larger, graceful, overlying arcs that any modernist painter or scratchboardist should be proud to claim. The more we look at this nearly three-dimensional image, the more we see; stare at it a while and it becomes nearly hypnotic.

If we tear our gaze away from the artsy image and become more scientific, our next task is to identify the bird that left its calling card on the window. It must have been fairly large, since the silhouette measured 4 inches top to bottom and 16 inches from wingtip to wingtip. It's certain this was no sparrow or finch we heard thump against the glass. The overall image size--plus the shape of the breast feathers--leads us to conclude it was left by a hard-headed Mourning Dove, perhaps a female because males (left) have wingspans up to 19 inches. And since doves lack an oil gland, that meant the image was indeed the result of powder down sticking to the glass.

The good part about this whole scenario is the dove apparently survived, at least in the short term; the bad part is every bird that hits a picture window or patio door or tall building isn't so lucky. Window strikes are a real and significant danger to birds, especially those that are migrating through and unfamiliar with local hazards. But that's a story for some other time. For now we're still marveling over the ethereal "study in black and white" on our office window at Hilton Pond Center.

All text & photos © Hilton Pond Center

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Be sure to scroll down for an account of all
birds banded or recaptured during the period,
plus other nature notes of interest.

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"This Week at Hilton Pond" is written & photographed
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Hilton Pond Center for Piedmont Natural History.

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8-14 March 2007

American Goldfinch--7
Chipping Sparrow--1
Northern Cardinal--2
White-throated Sparrow--2
Eastern Towhee--1
Mourning Dove--3

* = New species for 2007

6 species
16 individuals

13 species
397 individuals

(since 28 June 1982)
124 species
48,480 individuals

(with original banding date, sex, and current age)
American Goldfinch (1)
02/26/06--3rd year female

Dark-eyed Junco (1)
02/28/05--after 3rd year female

Chipping Sparrow (1)
04/02/04--after 4th year male

Northern Cardinal (1)
04/08/05--after 3rd year female

Tufted Titmouse (1)
08/24/06--2nd year unknown

White-throated Sparrow (1)
11/12/05--3rd year unknown

House Finch (1)
06/01/06--2nd year male

This Week at Hilton Pond
is part of the

--A male Wood Duck has been perching on one of the nest boxes along the perimeter of Hilton Pond this week, likely a sign a female is incubating within. Down on Nothilton Pond, the larger impoundment partly on the property, several Ring-necked Ducks are still present.

--On several nights this week we heard good numbers of Spring Peepers and Southern Leopard Frogs vocalizing from the banks of Hilton Pond. Historically, we dragged dead limbs away from the pond edges, but for the past few years have allowed branches and fallen trees to lie in place; we suspect this new practice has provided shallow-water hiding places for tadpoles and enabled some of our amphibian populations to increase.

--What a difference warmer weather makes. During last week's rain and chill we banded 85 birds (74 American Goldfinches), this week only 16 as the thermometer reached 80 on two consecutive days at Hilton Pond Center.

We banded a rather late female Rufous Hummingbird on 9 Mar near the Five Points section of Columbia SC; a second winter hummer--apparently a Rufous--also was present but did not enter the trap. These birds aparaently have been present since early Jan. 2007.

We observed but were unable to catch another late Rufous--a trap-wary male in full rusty plumage--on 13 Mar at Berea SC. This bird may have been present since Oct 2006.

It is often difficult to capture winter hummingbirds this late in the season because insects, nectar, and other natural foods are becoming abundant. Thus, it's important to report these hummers early when they're still coming primarily to feeders and are more catchable.

All text & photos © Hilton Pond Center

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