22-31 August 2004
Installment #236---Visitor #

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In 2004, informative and entertaining hummingbird banding presentations are scheduled for Aug-Sep in North Carolina, Ohio, Virginia & Kentucky/Tennessee.
Next Up: Canton, Ohio on 4 September
(Click on the logo at left for details.)
If your group would like to host Hummingbird Mornings anywhere in the U.S. or Canada in 2004 or later, contact
Bill Hilton Jr.


Across the Carolina Piedmont, hordes of plants from the Orient have found the region's red clay, ample rain, and mild winters very much to their liking. Our least favorite Asian import is the infamous Kudzu, Pueraria lobata, a fast-growing, tree-smothering vine we're grateful to have none of at Hilton Pond Center. (Knock on wood.) Instead we have Japanese Honeysuckle, Lonicera japonica, a twiny, viny plant against which--thanks to a sharp set of lopping shears--we seem to be holding our own. Overbearing Russian Olive, Eleagnus angustifolia, and prolific Japanese Privet, Ligustrum japonica, are pernicious shrubs we'll probably never be rid of, even though we use chainsaws and dynamite to deter them. (We exaggerate, but sometimes we ARE tempted to try incendiary devices--even though we doubt anything less than a nuclear warhead would have an impact on Chinese Wisteria, Wisteria sinensis.)

Despite the local success of these Far Eastern interlopers, the one foreign invasive we'd actually LIKE to have but can't seem to encourage at the Center is Mimosa, Albizia julibrissin (above left). This pink-flowered sweet-smelling tree--when kept in check--can be a real magnet for hummingbirds, native bees, and butterflies, but for some reason has not survived on our Hilton Pond acreage. In its absence we actually have another much-smaller Mimosa--Mimosa microphylla, the Little-leaf Sensitive Brier--a plant whose flowers are delightful to behold but whose real claim to fame is its behavior. "Plant BEHAVIOR?" you ask. Yes, plant behavior.

All text, photos & movies © Hilton Pond Center

Unlike the Mimosa tree--which originally occurred from Iran to Japan and now is found across temperate North America--M. microphylla grows naturally in the southeastern U.S. as far west as Texas; it is considered "very rare" and subject to possible extirpation in Virginia. And while Asian Mimosa is a woody tree that reaches 40 feet in height, its smaller local namesake is a perennial herbaceous vine whose green stems wind along the ground or ramble over low walls and shrubs. The 3-to-6-foot stems grow from a taproot that allows Little-leaf Sensitive Brier to overwinter underground and get a head start when warm days of spring arrive. We found our first plant at Hilton Pond Center back in the mid-1980s in a spot that is now too-shaded by new-growth trees; the specimen depicted on this page is in full sun on the Center's road frontage--right where road crews are likely to whack it back next time they cut vegetation along the shoulder. One vine from the taproot grows flat along the substrate, while the other has managed to find vertical support from low branches of an Eastern Red Cedar, Juniperus virginiana (large bottom photo).

The pink "powderpuff" blossom of Little-leaf Sensitive Brier is reminiscent of that of Mimosa trees, but to our eye it has much better form. Perfectly spherical and about three-quarters of an inch across, the flower heads erupt along the stem and are quite complex. Each globose cluster consists of many individual flowers: Sets of five petals fused into tubes; long anther stalks; and multiple stamens that carry a tiny spot of pollen at their tips. The overall effect is such that the entire blossom resembles a burst of fireworks, or--as one observer put it--the flower of Little-leaf Sensitive Brier looks like it could have been designed by Disney studios.

Both Mimosa and Little-leaf Sensitive Brier are classified in the Fabaceae (Pea Family), so one should not be surprised to find that seeds from each are borne in pods. Mimosa's fruit ripens in a more typical pea pod (see top photo), while that of Little-leaf Sensitive Brier is produced in a 3-6" spiny, downy, awl-shaped structure in which lies a row of tiny seeds. Members of the Pea Family are also known as "legumes"--plants that harbor nitrogen-collecting bacteria in nodes on their roots. Like soybeans and other legumes, Mimosa and Little-leafed Sensitive Brier help enrich land on which they grow by returning nitrogen to the soil.

Incidentally, one problem native plant enthusiasts will encounter when seeking information about Little-leaf Sensitive Brier is that it has been known by a confusing variety of scientific names. First described by Swedish botanist Jonas C. Dryander in the late 18th century, it was "misidentified" or "rediscovered" so many times that the scientific literature lists a dozen synonyms--the most common being Schrankia microphylla.

To learn more about the subject of this week's photo essay, we also need to dissect its common name: Little-leaf Sensitive Brier. Like many legumes, this plant has compound leaves, but in this case they are doubly compound; i.e., the petiole comes off the stems and is divided into leaflets that, in turn, are divided into subleaflets. These subleaflets are less than a quarter-inch long--hence the name "Little-leaf." The "Brier" part of the name pertains to inconspicuous decurved thorns (above right) that grow along the main vine, on the flower stalk, and on the midrib of the main leaf petiole. In spite of being less than an eighth-of-an-inch long, these briers are quite sharp and can easily lacerate a bare ankle or ungloved hand. (NOTE: A second thorned species, Mimosa quadrivalvis floridana, occurs in the Coastal Plain of Georgia and Florida, while a thornless type, M. strigillosa, grows just in Florida.)

All text, photos & movies © Hilton Pond Center

The most interesting aspect of Little-leaf Sensitive Brier we have saved until last--that being its "sensitivity." If you tap even lightly the leaves of this plant, there is an immediate change in osmotic cell presure that causes leaflets to point away from the main vine and subleaflets to fold in on themselves. This reaction--similar to the closing of a Venus' Fly Trap--occurs rapidly and has the function of protecting leaflets from herbivores by exposing all those sharp little briers. Curiously, a leaflet of Little-leaf Sensitive Brier doesn't have to be touched directly to fold; mere vibration from an adjoining leaf closing can cause an entire vine to fold its leaves in chain reaction. (Double-click on the image below to play a QuickTime movie of wind-blown leaflets folding in response to human touch; note also the small Hoverfly coming in for a sip of nectar.)

When disturbed, most flora simply sit there and take it, but the big Mimosa tree and Little-leaf Sensitive Brier actually respond to their environment. In the case of the tree, its leaves often fold at sunset or during rains and then re-open when the sun strikes them. By comparison, the more complex touch-response in Mimosa microphylla at Hilton Pond Center leads us to think that "plant BEHAVIOR" is a perfectly legitimate term for what happens in the leaflets of our sensitive little legumes.

All text, photos & movies © Hilton Pond Center

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NOTE: Be sure to scroll down for an account of all birds banded or recaptured during the week, as well as some other interesting nature notes.

"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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sightings of
Ruby-throated Hummingbirds


22-31 August 2004

Blue-winged Warbler
This juvenile captured on 31 Aug was only the 22nd of its species banded at the Center since 1982; of those 11 were netted in spring, 11 in fall.

Ruby-throated Hummingbird--24
Blue-winged Warbler--1
American Goldfinch--1
Acadian Flycatcher--1
Summer Tanager--1
House Finch--5
Carolina Wren--1

* = New species for 2004

7 species
34 individuals

51 species
1,692 individuals

(since 28 June 1982)
123 species
44,997 individuals

(with original banding date, sex, and current age)


--Hurricanes are coming fast and early in the eastern U.S., but without much fury here at Hilton Pond Center. Hurricane Gaston barely reached us with its outermost band of rain showers, dumping a grand total of 0.1" of rain. Just ten miles to the east, however, matriarch Jackie Hilton reported 1.0" of rain, and 30 miles east of her there some spots got up to 10" of hurricane-induced precipitation. (Our thanks go out to those of you who have expressed concern about the recent rash of storms along the Carolinas coast. Remember, however, that here in the northcentral Piedmont we're at least 150 miles from the ocean and that most hurricanes do relatively little damage this far inland--Hurricane Hugo excepted.)

--It's interesting that the American Goldfinch captured on 31 Aug at Hilton Pond was an adult female with active brood patch, indicating she was still sitting either on eggs or chicks. Nearly all our other local bird species have finished breeding for the year; Mourning Doves and goldfinches are notable exceptions.

All text & photos © Hilton Pond Center

This Week at Hilton Pond
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All text © Hilton Pond Center; white hummingbird photos © Kathy Greene

Try as we might on two mornings this week, we were unable to induce a white hummingbird--probably a Ruby-throated--to enter our portable trap when we deployed it at the home of Kathy Greene in Sharon SC, less than 8 miles west of Hilton Pond. We hoped to band Kathy's unusual hummer, but over a total of five hours it flew to and sat on the trap without ever going to the sugar water feeder we placed inside. On one overcast day before our visit, Kathy took a photo (above left) clearly showing the hummer had some pale tan spots and a black bill, eye, and feet; in other words, it was "leucistic" rather than a true albino. What's really curious is that a few days after our unsuccessful trapping attempts, Kathy took another photo (above right) that looks for all the world like an albino hummingbird with pink eye and pinkish-orange bill and feet. We're not positive, but the second photo may have been taken with electronic flash--which might account for a significant color shift and the "red-eye" effect. (And just what color IS eyeshine in hummingbirds?) We should note that a couple of leucistic hummers we handled had bills that in good light appeared more brown than black, which may be the case in the bird at upper right. Nevertheless--and as impossible as it might seem--it may be that Kathy actually had TWO white hummers at her rural feeder, one leucistic and one albinistic.

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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.