1-7 September 2005

Installment #284---
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Join us for another
Winter Hummingbird Expedition to Costa Rica
in February 2006


Everybody loves hummingbirds, and many folks around the U.S. and Canada--even in Latin America--bring these amazing avian aerobats up close with kitchen window feeders or flower boxes on the back deck. We at Hilton Pond Center are among those millions who concoct countless quarts of 4:1 sugar water mix each summer, replacing our artificial nectar on a three-day rotation lest local hummingbirds add too much mold and bacteria to their diet. On top of hosting feeder birds, we have the good fortune to capture and band hummers that breed around or migrate past Hilton Pond. With the advent of inexpensive but good digital cameras, almost anyone who maintains a feeder can also "capture" backyard hummers--their images, that is--and we've received some splendid photos lately from shutter-clicking hummingbird enthusiasts. Even though these photographers can get up-close shots of their fast-flying subjects, one big advantage provided by banding is even closer views. We never cease to marvel at what happens when we examine a hummer in-hand or through our macro lens, so we thought it appropriate this week to share some "hidden hummingbird wonders" we're privy to through the banding process.

All text & photos © Hilton Pond Center

What stimulated us to broach the topic of super-close hummingbird wonders was a still-mysterious phenomenon we encountered on 24 August after sighting an unusual Ruby-throated Hummingbird at a feeder. Since its wings and body bore almost symmetrical white spots, we thought at first the bird must be a partial albino, so we watched it on and off for a few hours until it finally flew into a nearby mist net--just what we needed for an in-hand view. As we began to untangle our new capture--an apparently healthy hatch-year male--we noticed the white spots were actually three-dimensional and atop the feathers, as if the bird had become marked somehow with thick but tiny dots of paint. Still perplexed, we took the hummingbird back to our lab, grabbed a hand lens, and were startled to find under 10X magnification the white spots were cylindrical, rounded on the ends, and attached to each other and the bird's feathers with extremely sticky silk. The silk was SO sticky we were unable to scrape the white objects from the hummingbird's feathers; in fact, when we tugged on two of the objects with fine forceps, one of the bird's primary covert feathers pulled out with the white things still attached. This feather, shown below, was only about a centimeter in length (less than half an inch).

All text & photos © Hilton Pond Center

At first we thought the tiny objects--each 0.5mm wide by 1.5mm long--must be insect eggs, but after receiving a few responses to our posting on an entomology list serve we concluded they more likely were insect PUPAE. Nobody said for sure what kind of insect may have produced the sticky white structures--or how they would have gotten onto a hummingbird in the first place. One entomologist suggested we keep the pupae under warm, humid conditions to encourage critters inside to expupate, but that hasn't happened after a week of waiting; the pupae HAVE turned brownish, however, as shown in the photo just above. Oddly, we heard from another bander in Georgia who encountered similar pupae on a hummingbird he caught recently, so we'd both appreciate any insights folks might have about these mysterious objects and what they could become. (Tiny blowflies, perhaps, or some other winged parasite? Or maybe just an accidental encounter with pupae intending to hitch a ride on something besides a hummingbird.) We hope we don't have to resort to some sort of microdissection of the pupae to solve this up-close hummingbird mystery.

All text & photos © Hilton Pond Center

Along less mysterious lines, most kitchen window observers know Ruby-throated Hummingbirds have dark eyes that appear black; in reality, only the pupil is black, while the iris is very dark brown. What is NOT visible through the window glass does appear in the close-up photo above, i.e., hummingbirds have "eyelashes." A detailed view of the hummer's eye region reveals tiny clusters of short bristle-like feathers along the edge of both eyelids. We assume that, like eyelash hairs in humans, these feather structures keep objects out of the eye itself, and may even provide some shading from strong light. In front of the eye are additional stiff bristles that point forward; we surmise these help keep wind from rushing directly into the eye when a hummer is in flight. Incidentally, the photo above also shows that the distinctive white spot behind the eye of a Ruby-throated Hummingbird is created by several light-colored feathers.

All text & photos © Hilton Pond Center

We often hear the comment that mid-summer hummingbirds look "drabber" than their spring counterparts, which is true. After getting all new feathers on their tropical wintering grounds--each Ruby-throated Hummingbird returns to the U.S. and Canada decked out in brightest breeding plumage. As the season progresses, iridescent green feathers on the ruby-throat's head and back do indeed get worn and a little faded; in fact, following the "summer hummer wars" adult males can look quite haggard. It's worth remembering, however, that most summer and autumn birds are recently fledged young birds (above), all of which leave the nest with brown-edged dorsal feathers that mask some of the metallic green. Preening--plus the mere action of wind passing over these new feathers--wears off the brown tips, causing a young bird's back, neck, and crown to look progressively brighter as it ages.

All text & photos © Hilton Pond Center

And speaking of age, another up-close secret of a hummingbird is the texture of its bill. When baby hummingbirds are born their bills are very short--they couldn't carry an inch-long bill within a kidney bean-sized egg--but their mandibles begin to grow almost immediately after hatch. The lengthening bill lays down little grooves or etchings--called "corrugations"--that are somewhat analogous to growth rings in trees. In a recently fledged hummer, these corrugations--barely visible with a 10x magnifier and even harder to photograph--occur all along the bill (above). As the free-flying hummingbird ages, the corrugations gradually fill in and/or smooth out from insertion of the bill into feeders and flowers. Thus, the roughly corrugated bill of a juvenile versus the smooth bill of an adult makes it relatively easy to age hummingbirds in summer or fall--IF you're able to look REALLY close.

All text & photos © Hilton Pond Center

Hummingbirds--and their distant relatives, the swifts--are classified in the Apodiformes--the avian order that includes birds with "no feet." Well, not exactly, but that's the literal translation of the ordinal name, given because swifts and hummers alike were thought to be legless and had to fly continuously. In the case of a hummingbird, its legs are held against the body during flight--tucked so tightly they are often hidden beneath the belly feathers. Obviously, hummingbirds DO have feet--otherwise, we doubt manufacturers would put perches on their feeders--but the appendages are pretty small, and a hummer can't walk on the ground. A hummingbird's lower leg--the tibiotarsus--is especially short, which is why the HEIGHT of a hummer band (above) is just as critical as its diameter; if the band were too tall the hummer could not bend its leg. We've always been intrigued that, compared to its lower leg, a hummingbird's toes seem massive, with long, black, decurved talons that would do an eagle proud. Quite strong and fully capable of keeping a baby hummingbird in its nest--or an adult on its favorite perch--a hummer's toes are seldom seen as close up as those in the photo above.

Of all the Ruby-throated Hummingbird attributes NOT visible when observing birds outside your window, perhaps our favorite is the true nature of a breeding male's gorget. If you affix a feeder to window glass with suction cups, it's possible to peer through and get nose-to-bill with a hovering hummer, but even then it appears the adult male's gorget (above left) is a mass of metallic red plumage. However, if you're lucky enough to be a bander and have the bird drop one of his throat feathers on your banding table (below), you'll learn something quite surprising: Only the outer ends of the gorget feathers are iridescent. Through our macro lens we can see the basal majority of each quarter-inch-long throat feather is fluffy and gray, and just the tip looks as if has been dipped into molten metal. In actuality, of course, there is no fiery pigment in the feather tip; the iridescent color results from microscopic grooves and bubbles that scatter and refract light to make the gorget look ruby-red.

All text & photos © Hilton Pond Center

Yes, these close-up and otherwise unseen views of hummingbirds are amazing--and quite pleasing to the mind and eye. We'd certainly like to know the identity of those mysterious pupae on a hummer's wing, but NOT knowing what they are doesn't diminish our appreciation of all the other "hidden hummingbird wonders" we found and share this week at Hilton Pond Center.

All text & photos © Hilton Pond Center

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"This Week at Hilton Pond" is written & photographed
by Bill Hilton Jr., executive director of
Hilton Pond Center for Piedmont Natural History.

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Ruby-throated Hummingbirds


1-7 September 2005

Ruby-throated Hummingbird--39
Northern Cardinal--2
Carolina Wren--1
Eastern Towhee--1
Mourning Dove--1

* = New species for 2005

5 species
44 individuals

46 species
1,088 individuals

(since 28 June 1982)
124 species
46,395 individuals

(with original banding date, sex, and current age)
Carolina Chickadee (1)
06/22/04--after hatch year female

--Our 39 Ruby-throated Hummingbirds this week more than doubled the best weekly results of 2005 and brought the season total to 166. Thus, the number of RTHUs banded through 7 Sep is 127% of our 22-year average by that date. The best day of the week was 6 Sep when--sped our way by unusual and brisk northeasterly winds--12 RTHUs were netted or trapped; this is the most birds in one day we have caught so late in the season, exceeding 3 Sep as the previous late date for 12 birds captured. The current year is now our ninth best for banding hummers at Hilton Pond Center. With several weeks left before all the ruby-throats are gone, we expect to catch more--even though 95% of them will be gone from the Carolinas by 1 Oct.

All text & photos © Hilton Pond Center

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Hilton Pond Center for Piedmont Natural History is a non-profit research & education organization in York, South Carolina USA; phone (803) 684-5852. Directed by Bill Hilton Jr., aka The Piedmont Naturalist, it is the parent organization for Operation RubyThroat. Contents of this Web site--including articles and photos--may NOT be duplicated, modified, or used in any way except with the express written permission of Hilton Pond Center. All rights reserved worldwide. To obtain permission for use or for further assistance on accessing this Web site, contact the Webmaster.

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