THIS WEEK at HILTON POND
1-7 May 2004
Installment #221--Visitor #

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THE BIRDS OF SPRING

After a long winter of banding mostly sparrows and those 1,056 Purple Finches, the onset of spring migration at Hilton Pond Center is a wondrous time indeed. When we unfurl our mist nets each morning, we do so with anticipation, ever mindful that a southerly breeze may bring with it some Neotropical migrant species that we seldom see except in spring or fall. We don't capture anywhere near as many migrant passerines as do banding stations in major flyways along the coast or mountains, but those we do get make it all the more worthwhile to open nets at dawn and check them every half-hour until closing down at dusk. Some springs, when there are no favorable weather fronts, we net almost no migrants, but 2004 has been both acceptable and enjoyable. For our photo essay this week, we decided to share photos of a few feathered friends that stopped in at Hilton Pond this week--birds of spring mostly on their way to breeding grounds much further north in the U.S. or Canada.

All text & photos © Hilton Pond Center

  • Male Scarlet Tanagers may be THE most brilliant birds that visit Hilton Pond Center. Unfortunately, we're just a little east and south of where they breed, so we have to content ourselves with taking an eye-popping look at them during spring and fall migration; we've banded only 70 since 1982. The wings on this week's individual weren't completely black; the greenish cast to several feathers indicated it was a second-year bird hatched out in 2003. The small "tooth" along the edge of the upper bill is a tanager characteristic.

  • Rose-breasted Grosbeaks also occur at Hilton Pond only during migration. Their heavy, bone-colored bills (above) are diagnostic. The typical rose-colored chest patch that gives the species its common name was quite bright in this male; less obvious were underwing linings of the same hue (below). This species is quite uncommon locally, with only 28 banded during the past 23 years and distributed nearly equally between spring and fall.

  • Although some of the 219 Eastern Bluebirds we've handled at Hilton Pond Center have been adult males (above and below), more than half have been nestlings banded before they were old enough to fledge from one of many nestboxes around the property. We had considerably more bluebirds nesting locally in the decade after 1982, but nestboxes that were out in the open back then are now in dense woods that have grown up via natural vegetational succession. These days, the "bluebird" boxes are more likely to be occupied by Carolina Chickadees or Southern Flying Squirrels, but we still get a few bluebird broods in boxes along the road that borders Hilton Pond Center.

  • The blue of the Eastern Bluebird is much different from that of the male Black-throated Blue Warbler (above and below), whose dorsum is more of a slaty hue. The male's black mask and large white wing spot are quick cues to identifying this wood warbler, which--like the Scarlet Tanager--breeds to the north and west of Hilton Pond Center. The female Black-throated Blue Warbler has the same prominent wing spot as the male, but is greenish-brown above with a yellowish breast--so unlike the male that no less an observer than John James Audubon thought they were separate species. The black-throated blue is one of our more common migrant warblers, with 144 banded since 1982.

  • When running mist nets in spring at Hilton Pond Center, we're sometimes surprised by what we catch, but one bird we captured this week was so unexpected it took a while to figure out its full story. When we first saw the bird in the net on 5 May, there wasn't much doubt it was a Hooded Warbler--the 40th of its species banded in the past 23 years. Its yellow breast and undertail coverts--in combination with large white tail spots (below)--clinched the ID. Adult male Hooded Warblers have a jet-black hood and bib, while adult females typically bear a dark greenish or even black crown--but no bib. The crown of the bird we caught seemed far too pale for an adult female, and the condition of the plumage indicated juvenile--something that seemed impossible at this time of year because the earliest reported egg-laying for South Carolina is 14 April. Since warbler eggs take about 12 days to hatch and the young are in the nest for another 8-10 days, the egg that produced the individual we caught on 5 May would have been laid on about the first week in April--only a week or so after the earlist-ever migrants have been reported for the Carolina Piedmont!

  • Thus, we had a little mystery in our hands, and the only conclusive way to age the warbler was through a process called "skulling," in which the crown feathers are moistened and bent back to reveal the skin beneath. We did this and then used a magnifier to examine the skin--so thin that the skull is visible through it. The bird's cranium is actually two layers of bone, and in adults ossification creates tiny columns that connect the two layers. These columns appear as white dots that show through the skin, but there were none in the bird we examined. This confirmed our original thinking that this was a recently fledged youngster, indicating it was from what could be the earliest Hooded Warbler breeding ever reported from South Carolina.

It's too bad we couldn't have found that Hooded Warbler nest when the female was incubating. Since we didn't, we can only extrapolate and speculate about hatch date and actual origin for the fledgling we caught. If the nest was on-site, it would be the 25th breeding bird species on our 11-acre property, but unless the female tries another brood--which she has plenty of time to do at this early date--we still won't know for sure if Hooded Warblers breed locally.

One thing we ARE certain of, however, is that a highly effective way to get a Rose-breasted Grosbeak to stop biting one's knuckles is to allow it to chomp down on one's finger instead--a small but somewhat painful price to pay for the joy of holding and photographing "The Birds of Spring" that occurred this week at Hilton Pond Center.

All text & photos © Hilton Pond Center

POSTSCRIPT: After we initially posted the above account, some folks who have far more experience with Hooded Warblers suggested that the bird in question shows too much tail wear to be a juvenile, and is instead a second-year female with delayed skull ossification--perhaps a bird that hatched out very late in the 2003 breeding season. In retrospect, this likely is the case, and we bow to their wisdom despite the misleading results of our skulling effort. Such reconsideration reflects the difficulties banders sometimes have in ageing birds and simply adds to our excitement over capturing a species that is rare at 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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BIRDS BANDED THIS WEEK
at HILTON POND CENTER
1-7 May 2004

SPECIES BANDED THIS WEEK:
American Redstart--2*
Blue-gray Gnatcatcher--1
White-eyed Vireo--1
Chipping Sparrow--1
Hooded Warbler--1*
Northern Waterthrush--1*
Indigo Bunting--2
Red-eyed Vireo--2
Gray Catbird--5
Northern Cardinal--1
Wood Thrush--1
Tufted Titmouse--1
Scarlet Tanager--1*
House Finch--2
Eastern Bluebird--1
Rose-breasted Grosbeak--1

* = New species for 2004

WEEKLY BANDING TOTAL
16 species
24 individuals

YEARLY BANDING TOTAL
(2004)
43 species
1,346 individuals

BANDING GRAND TOTAL
(since 28 June 1982)
123 species
44,651 individuals

All text & photos © Hilton Pond Center

This Week at Hilton Pond
is part of the

NOTABLE RECAPTURES THIS WEEK
(with original banding date, sex, and current age)

Carolina Chickadee (2)
03/29/02--after 3rd year female
07/08/02--3rd year female

Chipping Sparrow (1)
05/31/03--after 2nd year female

Northern Cardinal (3)
07/30/01--4th year male
07/08/02--3rd year male
11/23/02--after 2nd year female

Eastern Towhee (1)
08/08/02--3rd year female

Tufted Titmouse (3)
04/30/02--after 3rd year male
05/16/03--2nd year female
07/17/03--2nd year female

White-throated Sparrow (1)
11/11/03--2nd year unknown
12/22/03--2nd year unknown

OTHER SIGHTINGS OF INTEREST

--On 3 May, a covey of about a dozen half-grown Northern Bobwhite sailed into some dense cover just outside the farmhouse office window at Hilton Pond Center. When the property was more open in the 1980s, the sound of the quail's shrill whistle was fairly common, but these were the first we had seen or heard locally in more than five years.

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HUMMINGBIRD MORNINGS
In 2004, informative and entertaining hummingbird banding presentations are already scheduled for North Carolina, Ohio, Virginia, Michigan & Kentucky/Tennessee.
(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.

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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.