- Established 1982 -


18-31 March 2023

Installment #803---Visitor #web counter

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We know it's really spring at Hilton Pond Center when we spot our first Blue-gray Gnatcatcher (BGGN) of the year (photo below). Such was the case on 31 March when one of these hyperkinetic little birds appeared after spending the cold months along southern U.S. coastlines or somewhere in Mexico. Historically, BGGN nested in subtropical areas of North America but are advancing northward and now breed as far north as the Great Lakes. This is a fairly recent range expansion likely due to climate change and higher average temperatures.

All text, maps, charts & photos © Hilton Pond Center

Some folks have likened BGGN to miniature Northern Mockingbirds because of a gray body and long white outer tail feathers (above) they flick constantly while foraging for insects. Despite any similarities to mockers, Blue-gray Gnatcatchers are in the Polioptilidae (Gnatcatcher Family) not the Mimidae (Mimic Thrush Family) and are more closely related to wrens. Incidentally, adult male BGGN (above) have a black superciliary line lacking in females.

All text, maps, charts & photos © Hilton Pond Center

Each year gnatcatchers are preceded at the Center by a less welcome influx of Brown-headed Cowbirds (BHCO), usually in late March in groups of two or three males chasing a female. The species is named for the male (above) with its chestnut-colored head, shiny black body, and sharply pointed conical black bill. Female cowbirds (below) are among the most nondescript birds in North America, and many novice birders have trouble identifying them. The female's body is a mousy grayish-brown but the distinctive black mandibles still say Brown-headed Cowbird. (Repeat: Look for that stout black bill.)

All text, maps, charts & photos © Hilton Pond Center

Like many ornithologists, we have mixed feelings about cowbirds because of their propensity for laying eggs in the nests of other species--maybe even Blue-Gray Gnatcatchers that typically fail to recognize a cowbird egg among their own clutch. As social parasites BHCO are known to take advantage of about 220 bird species, at least half of which have ended up raising cowbird foster chicks--often at the expense of their own.

One hypothesis is that Brown-headed Cowbirds evolved in the Great Plains following herds of American Bison to forage on stirred-up insects, eventually losing nest-building genes and now depending entirely on sedentary host species to propagate. Another interpretation is that BHCO arose in the Neotropics, where their nest parasitism became a successful strategy they brought with them as they radiated north. In any case, cowbirds these days have a stable North American population, so there's no question their brood parasitization is an effective adaptation that some folks admire for its evolutionary success.

All text, maps, charts & photos © Hilton Pond Center

Although we occasionally see BHCO (above) within massive winter flocks of Common Grackles, Red-winged Blackbirds, and European Starlings, come late March local cowbirds mostly just show up here in those small groups. They frequently enter our ground traps containing mixed seeds, but the best way to snare male cowbirds is to catch a female first and let her be bait. The species does not form pair bonds and both sexes copulate promiscuously, with males constantly chasing receptive females throughout the breeding season.

A female Brown-headed Cowbird may lay a dozen or more eggs, take a break, and lay a dozen more. After females drop those eggs in other birds' nests all our Hilton Pond cowbirds literally disappear by mid-summer: In 42 years of banding at the Center we've banded 558 BHCO--but only SIX of them July through December!

All text, maps, charts & photos © Hilton Pond Center


To summarize and expand upon our earlier reports:

On 20 February at Hilton Pond Center we observed a Black Vulture strutting on the metal roof of an abandoned chicken coop about 30 yards from our old farmhouse. As we watched from our office window, the vulture dropped to the ground and disappeared behind the far end of the shed. Curious about where the big black bird had gone, we later entered the structure and spooked the vulture, which flew out through a big hole in the coop siding. Left behind in a nest scrape on the hard concrete floor were two three-inch mottled greenish eggs (below) the bird must have been incubating. To minimize disturbance, we retreated from this nest area and took a station some distance away. From there we saw the Black Vulture re-enter the chicken coop.

All text, maps, charts & photos © Hilton Pond Center

The situation presented what we thought could be an interesting opportunity to observe Black Vulture reproductive behavior. Folks elsewhere have set up remote cameras at nests of Bald Eagles and Peregrine Falcons, but not many have showcased Black Vultures with webcams. Thanks to a financial gift from a major supporter of Hilton Pond Center for Piedmont Natural History, we immediately ordered a surveillance camera, laptop, Ethernet cables, and associated equipment and--within a week or so--had established a YouTube livestream depicting what was going on in the dim recesses of our ramshackle chicken coop, now elegantly dubbed "Chez Vautour Noir."

All text, maps, charts & photos © Hilton Pond Center

One big glitch occurred as we were running Ethernet cable on the ground from our desktop computer to the camera in the chicken coop. Within hours it seems one of our local Eastern Cottontails perceived the 100-foot-long red cable as some sort of delicacy and completely bit through the wiring (above)--not once, but twice!--requiring we run new lines (at twenty bucks each). After the second severing we threaded the cable through a couple lengths of metal electrical conduit in the vegetated area where the rabbit had been doing its work. We also coated the wire with nasty-tasting Bitter Apple spray. Dang rabbits!

All text, maps, charts & photos © Hilton Pond Center

Eventually the livestream from the vulture nest caught on and folks around the country began watching. One couple in Ohio told us they even projected the YouTube video on a big screen TV (above) so they could stay up-to-the-minute on what was happening in the ol' chicken coop. (And no commercials, they said!)

All text, maps, charts & photos © Hilton Pond Center

Most of the livestream was near-countless minutes of a Black Vulture simply sitting and incubating--punctuated by footage of the bird stretching (above), preening, and defecating. (The camera's infrared capability even showed what was happening during dark of night, and that was not much.)

All text, maps, charts & photos © Hilton Pond Center

Roughly every 24 hours, a second vulture would enter the scene and the pair would go through a ritual of head- and bill-rubbing and neck preening (above) before the new bird took over egg-sitting duties. Any sort of movement at the nest put the camera in "record," sending video snippets to our desktop computer. We collected these and posted them sequentially to YouTube, complete with interpretive commentary. Still images from these snippets are included above and below.

All text, maps, charts & photos © Hilton Pond Center

The livestream continued day after day, night after night as parent vultures took turns incubating, with one bird to departing to stretch its wings and forage on some distant offal while the other tucked in its head and took a snooze (above). Considering the incubation period for Black Vultures is an estimated 30-38 days, we figured hatching was imminent by the last week in March and expected any moment to welcome baby vultures into the world. Alas, that was not to be.

All text, maps, charts & photos © Hilton Pond Center

Early afternoon on 23 March, as we were watching the livestream in real time, what seemed to be a third Black Vulture (with distended crop, above) entered the nest area in the chicken coop. The new bird went straight to the incubating vulture, which seemed quite nervous but attempted the usual head and bill rub greeting ritual. The new bird wanted none of this, pushing the incubator off the eggs and immediately tossing them roughly around the shed with its bill. We were stunned.

All text, maps, charts & photos © Hilton Pond Center

The incubating vulture made feeble, mostly unsuccessful attempts to cover the eggs but seemed helpless during the assault and egg-toss. Eventually both birds left the scene, so we decided to re-enter the shed and check on the two eggs (above). One seemed intact but the other was cracked. We gathered them and placed them together in the nest scrape, then retreated to see what might happen next.

All text, maps, charts & photos © Hilton Pond Center

Within a few minutes the incubating vulture returned to duty, followed in short order by the more aggressive bird. The scenario repeated, with the interloper pushing the incubator around and violently tossing eggs. After about eight minutes of disruption, both vultures departed and we entered the chicken coop to examine the eggs again. The cracked one was damaged even more (above) and we couldn't really discern its contents but the other seemed undamaged; once more we placed them together in the scrape and exited.

(NOTE: We doubt our presence or our handling of eggs had any impact of the behavior of any of the adult Black Vultures. Our visits to examine the ransacked eggs was our first to the chicken coop since we set up the camera.)

All text, maps, charts & photos © Hilton Pond Center

Following our departure, the incubating vulture hopped into the shed one more time and incubated both eggs, this time almost all night. About 5:25 a.m. on 24 March, however, the incubator suddenly dragged the badly broken egg away from the scrape and began eating the contents (above)--apparently a partially developed chick--leaving some behind before walking out of the field of view. All this was happening in the dark before dawn and was revealed by the infrared camera.

All text, maps, charts & photos © Hilton Pond Center

A vulture appeared soon after, finishing off what was left from the first egg and shifting attention to the second, rolling it around and eventually pecking at it and breaking through the shell (above). For the next 90 minutes this vulture sampled contents of Egg #2, preened and wandered about the coop, pushing sticks and other vegetation from one spot to another--perhaps waiting for daylight--and eventually departed. Over the next several daylight hours and again the next day (25 March) at least two different Black Vultures returned individually and/or together to inspect the nest area. A solitary bird showed up on the 26th (see photo below) but video recordings revealed no more vulture visits after that.

All text, maps, charts & photos © Hilton Pond Center

So one might ask: "What the heck happened?" We don't have any definite answers, in part because Black Vultures all look pretty much alike--especially in low resolution video snippets. Were there two attentive parent vultures and then an interloper that attacked its competitors' eggs, which we suspect. Or did one parent bird decide the eggs were dead or perhaps just get tired of incubating? After all, both eggs were at least 35 days old, with typical incubation expected to take less than 40 days. (It's worth noting there were six cold, sub-freezing nights in mid-March when those eggs--despite being covered by a warm, incubating parent--were sitting on the shed's hard concrete floor. That's a situation that might chill an embryo enough to permanently stop development.)

The above are possibilities about what led to nest failure, but maybe something else was going on about which we simply don't have a clue. There may be too many variables and insufficient information to draw a definitive conclusion, of course, so for now we'll let the matter rest as The Mystery of Chez Vautour Noir: An Unexplained Black Vulture Nest Failure. We invite you to examine the Black Vulture Nest Cam video snippets on YouTube and to suggest in a message to INFO any alternative explanations you might derive.

All text, maps, charts & photos © Hilton Pond Center

Mystery or not, on the plus side Hilton Pond Center now has a nice infrared surveillance camera, a dedicated MacBook laptop, several hundred feet of Ethernet cable, power injectors, switches, extension cords, and ancillary equipment (to say nothing of hours and hours of video footage). We're all set if the Black Vulture pair (above) returns to try again in 2024--or if some other natural phenomenon suitable for livestreaming should pop up.

All text, maps, charts & photos © Hilton Pond Center

Just in case, the surveillance camera is still running--the livestream is not--sending snippets to our desktop computer when anything occurs in the Black Vulture nest area. The species is known to re-nest after a failed clutch, but that had not occurred through the end of March. And who knows what else might go on in the dark recesses of Chez Vautour Noir--like maybe a visit from a night-wandering Didelphis virginiana (above).


POSTSCRIPT: The empty shell from Egg #1 still sits in the nest scrape. Seems like it would be a good source of calcium for some wandering rodent that might enter the shed.

All text, maps, charts & photos © Hilton Pond Center

(from our on-going series)

"Never trust a person too lazy to get up for sunrise
or too busy to watch the sunset."

All text, maps, charts & photos © Hilton Pond Center

Sunset over Hilton Pond, 24 March 2023

Under a clear sky the sunset was pretty straightforward on 24 March, so we waited a few hours for the Earth's Moon and sister
planet Venus to come into view beneath a branch of the big
Shagbark Hickory outside my office window. There are lots
of pinpoint stars, too, along with fat terminal buds waiting
to burst on the old hickory--plus a few dogwood
blossoms down below.

All text, maps, charts & photos © Hilton Pond Center

Sunset over Hilton Pond, 27 March 2023

High above the clouds, passenger jets traced white contrails across blue sky, but lower down angry clouds could not decide whether to unleash another lightning storm or pock the pond with a little
spit-rain. The deluge missed us, but not by much; plenty of
loud thunder crashes nearby.

Don't forget to scroll down for lists of Hilton Pond supporters and of all birds banded and recaptured during the period.

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

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Thanks to the following fine folks for recent gifts in support of Hilton Pond Center for Piedmont Natural History and/or Operation RubyThroat: The Hummingbird Project. Your tax-deductible contributions allow us, among other things, to continue writing, photographing, and sharing "This Week at Hilton Pond" with students, teachers, fellow scientists, and the general public. Please scroll below to the blue section if you'd like to make a gift of your own.

We're pleased folks are thinking about the work of the Center and making donations. Those listed below made contributions received during the period. Please join them if you can in coming weeks.

Gifts can be made via PayPal/Vimeo (; credit card via Network for Good (see link below); or personal check (c/o Hilton Pond Center, 1432 DeVinney Road, York SC 29745). You can also donate through our Facebook fundraising page.

The following donors made contributions to Hilton Pond Center during the period 18-31 March 2023.

  • Anita Clemmer (repeat donor; via PayPal)
  • Liz Layton* (long-time supporter)
  • The friends below contributed via the "Donate" button on one of the Center's Facebook postings or fundraisers; some are repeat contributors. Several have set up through Facebook to make a recurring monthly donation to benefit the Center. Many are much-appreciated long-time and/or repeat donors.
    --Becky Laskody, Cheri Pierce, J. Drew Lanham, Bill Pennington, Pat Dubose, Lynn Biasini McElfresh
    * = Past participant in Operation RubyThroat Neotropical Hummingbird expedition

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18-31 March 2023

Chipping Sparrow--4
American Goldfinch--1
Carolina Chickadee--2
Pine Warbler--1
Yellow-rumped Warbler--1
Brown-headed Cowbird--17
Hairy Woodpecker-- 1
White-throated Sparrow--6
Purple Finch--
Song Sparrow--2
Mourning Dove--1

* = new banded species for 2023

11 species
43 individuals

23 species (42-yr. avg. = 65.0)

794 individuals
(42-yr. avg. =

0 Ruby-throated Hummingbirds

(Banding began 28 June 1982; since then 173 species have been observed on or over the property.)
128 species banded
77,859 individuals banded

7,190 Ruby-throated Hummingbirds banded since 1984

(with original banding date, verified sex, and current age):
Carolina Chickadee (3)
09/17/21--3rd year male
06/09/22--2nd year unknown
09/26/22--2nd year male

Chipping Sparrow (1)
04/14/22--3rd year unknown

Northern Cardinal (1)
08/29/21--3rd year female

House Finch (4)
06/05/20--4th year male
05/26/22--after 2nd year male
06/04/22--2nd year female
11/05/22--2nd year female

Purple Finch (2)
03/04/16--after 9th year male***
03/17/21--after 4th year male

Carolina Wren (1)
06/07/22--2nd year unknown

Tufted Titmouse (1)
06/19/21--3rd year female

Downy Woodpecker (1)
02/22/22--3rd year male

White-throated Sparrow (1)
12/03/22--2nd year unknown

** Notable local longevity for species
*** Longevity record for Hilton Pond

--For the record, at 5 p.m. on 29 March an adult male Ruby-throated Hummingbird made a fleeting visit to one of our freshly filled feeders at Hilton Pond Center--later by three days than our all-time earliest. Still no RTHU captured for banding through month's end.

--On 31 Mar at the Center we recaptured a male Downy Woodpecker with a prominent brood patch. Unlike songbirds, in many woodpecker species both male and female incubate eggs, so a naked-belly brood patch is a big plus for transmitting body heat to eggs--and chicks.

--Our last "flock" of Purple Finches was on 1-2 March 2023 when we had 20-plus (down from 50 or more back in January). Since then we've seen no more than three per day (often none) until this 30 Mar when 11 showed up at the Center's sunflower tube feeders. (None were adult males.)

--As of 31 Mar, Hilton Pond's 2023 Yard List stood at 51--about 29.5% of 173 avian species encountered locally since 1982. Our record for one calendar year is 111, reached in 2020 & 2021. (Incidentally, all species so far this year have been observed from windows, porches, or the yard around our old farmhouse!) If you're not keeping a Yard List for your own property we encourage you to do so, and to report your sightings via eBird, where you, too, can be a "citizen scientist!") New species observed locally during the period 18-31 March: Ruby-throated Hummingbird, Green Heron, Cedar Waxwing, Blue-gray Gnatcatcher, Black-and-white Warbler.

--Our immediate past installment of "This Week at Hilton Pond" was about dogwoods, hummers, and Purple Finches and is archived and always available on our Web site as Installment #802.

All text & photos © Hilton Pond Center

Please report your spring, summer &
fall sightings of
Ruby-throated Hummingbirds

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