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THIS WEEK at HILTON POND
1-13 December 2019

Installment #706---Visitor # website counter

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21 December 2019
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WINTER'S HUNGRY HAWKS

When folks find out we're into ornithology, they often ask: "What's your favorite bird?" Well, let's see. Downy Woodpeckers and Carolina Wrens were our "spark species" that got us into watching birds. While in grad school in Minnesota we focused on behavioral ecology of Blue Jays. And for the past 36 years we've grown deeply interested in Ruby-throated Hummingbirds. Nonetheless, we typically reply we have no favorite bird, that all of them from Brown Thrashers to Black Vultures are equally interesting.

Along those lines, we also caution people when they pass judgment on various bird species, like how they "hate" Sharp-shinned Hawks because these speedy raptors sometimes prey on songbirds at backyard feeders. Our usual comment is "If you put out sunflower seeds for chickadees, you're really just putting out chickadees for sharp-shins"--after which we congratulate the birdwatcher for the uncommon opportunity to observe sharpies and chickadees in a perfectly performed predator-prey tableau.

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

Although diurnal raptors are present year-round at Hilton Pond Center, the best time to watch them in action is during winter when hardwood trees are bare and smaller birds are congregating at our feeders. It's then that Sharp-shinned Hawks migrate in from further north and resident Cooper's Hawks and Red-shouldered Hawks start looking for appropriately sized prey at our feeders. Rarely we host an immature Red-tailed Hawk whose attention is focused more on our substantial population of Eastern Gray Squirrels--one of which is being consumed in the photo above. (Migratory Mississippi Kites and Broad-tailed Hawks are on the Center's "Yard List" only because they sometimes circle overhead during breeding months, but we haven't seen an American Kestrel locally in more than 30 years. Osprey is our only other diurnal raptor; they occasionally dive after a fish in Hilton Pond as they fly north or south in spring and fall.)

One of our first activities each morning at Hilton Pond Center is to look out the kitchen window of the old farmhouse, checking to see which birds are also early risers. Some days there are no songbirds at all at the feeders, which usually means a predator is present. Sometimes it is an adult Red-shouldered Hawk (RSHA, below), perched in a nearby snag or even on a platform feeder!

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

RSHA are our most frequently observed raptors at the Center, likely because a pair nests and raises a couple or three young on the property each year. Most days we see one or more perched--or gliding through the trees or across the pond. The adults are permanent residents, with the current year's fledglings remaining through the first winter or dispersing in autumn for points unknown.

It's likely the Red-shouldered Hawk in the feeder photo above was waiting for an Eastern Chipmunk to venture forth on its usual mission of cleaning up spilled seeds beneath the feeder. Or it might have been looking for a Green Frog in the small garden pool just below. Chipmunks and frogs are among the red-shouldered's favorite meals, but the hawk undoubtedly would settle for breakfast fillet from a careless Northern Cardinal or Mourning Dove. (Check out those stout toes and talons--to say nothing of the hawk's heavily hooked upper mandible!)

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

The RSHA in our feeder photo has "adult" plumage; i.e., the breast is marked with horizontal rusty barring rather than the vertical brown streaks of an immature (just above). That said, the "adult" hawk is likely in only its third year--hatched in 2017--because its eye is pinkish-yellow rather than the bright crystalline red characteristic of older, mature Red-shouldered Hawks.

Another notable attribute is the hawk's bright yellow cere (below left)-- the relatively soft area surrounding the nostrils at the base of the upper mandible. The true function of the cere is a bit of a mystery. Some ornithologists claim it extends the length of the nostril and thus protects it from penetration by struggling prey items. A better explanation may have been discovered by a researcher who demonstrated the cere "emits" ultraviolet light that may be visible to other hawks (although not to humans). The investigator showed among Montagu's Harriers (an Old World diurnal hawk), males with the brightest UV reflectance were also the most robust and more likely to garner attention of female harriers. Thus, the cere's main function actually may be to serve as a sexual signal.

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

We banded our first local red-shouldered back in 1993 and have handled a total of 11--one full adult, one sub-adult, and nine hatch-year or second-year individuals. They are a handful and require a Size 6 lock-on band with overlapping flanges (above); with its hooked bill this large hawk can pry open a standard butt band.

Our second most commonly observed winter raptor at Hilton Pond Center is the Cooper's Hawk (COHA), an accipiter whose short, rounded wings and long tail are adaptations for chasing avian prey through thick vegetation. (The Sharp-shinned Hawk is a close relative discussed later.)

As with the Red-shouldered Hawk, adult Cooper's Hawks (right) have rusty horizontal barring on breast and belly. Immatures (below) have dark brown vertical streaking. Observers sometimes confuse large adult female "coops" with red-shouldereds, but the former have slate blue wings and back compared to brown in the RSHA (NOTE: Immature Cooper's also have brown backs.) When feet are visible, the toes, legs, and talons of Cooper's Hawks and other accipiters are much thinner than those in buteos such as the Red-shouldered.

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

Even though we see Cooper's Hawks fairly often at Hilton Pond, we've banded only three. All were young birds will yellow or grayish-yellow irises; adults generally have red eyes after the second year or so. Two were banded in late fall (October and November) and could have been arriving migrants; the other hit a high mist net in mid-May one year when Ernesto M. Carman was visiting from Costa Rica. Based on measurements we made with a leg gauge, all three Cooper's Hawks required lock-on bands, but in Size 5 (a bit smaller than those needed for a Red-shouldered Hawk).

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

We didn't deploy mist nets much during early December at Hilton Pond Center, deferring to windy and damp weather that made it unwise to try to snare birds in that way--lest feathers get matted down and hypothermia set in. We did run various traps unless rain was really coming down. Some days we just used two hanging traps, each containing a sunflower seed tube feeder (shown above, with American Goldfinches inside). These two are the most effective of all our traps, and it's not uncommon to quickly catch a dozen or more winter finches at one time as they enter through one-way tunnels.

On 9 December the two hanging traps were baited and set, so we checked every few minutes to see if anything had gone in. It was a slow day, but at about 4 p.m. we glanced at the trap just outside the office window of our old farmhouse and noticed three House Finches caught therein. Oddly, they were completely stationary and not fluttering about. A broader view revealed the reason: A small hawk was perched a few feet away on an outdoor water fountain, so the finches were apparently in freeze mode.

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

Grabbing our ever-ready SLR camera with telephoto lens, we slowly moved into position for a shot through the window and got the image above. Such stealthiness was unnecessary, however, for when we opened the sliding glass door for another photo the little hawk just sat there and stared back. As we walked onto the deck, the hawk suddenly flew at the trap and attempted to get at the finches, so we spooked it away and brought the smaller birds in for banding. Meanwhile, the hawk perched on a tree limb about 20 feet from the trap, perhaps wondering where its prospective lunch had gone.

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

A large hawk this was not. With a body not much bigger than the palm of one's hand--Blue Jay size--its skinny legs and long thin toes armed with sharp talons indicated it was another accipiter, either a Sharp-shinned Hawk (SSHA) or Cooper's Hawk (COHA). These two species--adapted for preying on smaller birds--are often difficult to differentiate in the field, although SSHA generally have squared tails while the COHA tail is usually rounded. (CAVEAT: This is not a 100% reliable characteristic. See our copyrighted graphic above for other identification hints.)

Of the two species, "coops" are somewhat larger than "sharpies," but this difference falls apart when we learn male sharp-shins are relatively small, female SSHA are about the same size as male COHA, and female COHA are the largest of all.

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

To make a long story shorter, we managed to capture the little hawk using a bal-chatri trap covered with monofilament nooses that snared the raptor's toes. In-hand, a short wing chord measurement (193mm) told us it had to be a Sharp-shinned Hawk, and wing plus tail measure (165mm) showed it was a longer-tailed female sharpie.

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

More-or-less brownish vertical streaking on her breast and a streaked crown indicated she was immature; older SSHA (just above) typically have that horizontal rusty-red barring and dark bluish crowns and backs just like a Cooper's Hawk. Again, our young hatch-year sharpie had yellow irises (below) that should darken as she ages and likely will turn crystalline red.

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

This individual was the 40th SSHA captured at Hilton Pond since 1982--our most commonly banded raptor--but the first in a long while (7 December 2001). Of those, 78% were banded in autumn or early winter, suggesting they were southbound migrants. Upon banding and release this week's little Sharp-shinned Hawk high-tailed it across the pond, after which we figured it was safe to let go the three newly banded House Finches. Even so, we wager more than one of the Center's dickey-birds will end up in the crop of a hungry and efficient winter raptor.

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




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Don't forget to scroll down for Nature Notes & Photos,
plus lists of all birds banded or recaptured during the period.



"This Week at Hilton Pond" is written and photographed by 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, and the general public. Please see Support or scroll below 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 (funding@hiltonpond.org); 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 made contributions to Hilton Pond Center during the period 1-13 Dec 2019:

  • Sara Brydges (repeat donor, via Network for Good)
  • James F. & Nelle E. Burgess Foundation, via Pam Shucker
  • Susan B. Clark (long-time repeat supporter)
  • Anne C. Dillon (long-time sustaining donor)
  • Robert T. Oesterle (long-time donor)
  • The following friends contributed via the "Donate" button on one of the Center's Facebook postings, including GivingTuesday and our End-of-Year Fundraiser; some may be repeat Facebook contributors. Rosemarie Wahaus, Lynn Biasini McElfresh, Susan B. Hilton, Peg de Lamater, Myer Bornstein, Laura Crompton, Ann Bailie, Amy Girten, Lisa Rest, Cindy Massey (major donor), Cheryl Hill, Robert Woerner, Elizabeth Layton, Sherry Ede
 
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The Piedmont Naturalist--Vol. 1--1986 (Hilton Pond Press) is an award-winning collection of newspaper columns that first appeared in The Herald in Rock Hill SC. Optimized for tablets such as iPad and Kindle, electronic downloads of the now out-of-print volume are available by clicking on the links below. The digital version includes pen-and-ink drawings from the original edition--plus lots of new color photos. All sales go
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BIRDS BANDED THIS WEEK at
HILTON POND CENTER
1-13 December 2019

SPECIES BANDED THIS PERIOD:
Pine Warbler--1
Northern Cardinal--4
House Finch--19
Mourning Dove--1
Sharp-shinned Hawk--1
*

* = new banded species for 2019


PERIOD BANDING TOTAL:
5 species
26 individuals


2019 BANDING TOTAL:
67 species (38-yr. avg. = 65.0)

1,505 individuals
(38-yr. avg. =
1,832.5)

Ruby-throated Hummingbirds = 162


38-YEAR BANDING GRAND TOTAL:
(Banding began 28 June 1982; since then 171 species have been observed on or over the property.)
127 species banded
69,635 individuals banded

6,355 Ruby-throated Hummingbirds banded


NOTABLE RECAPTURES THIS WEEK:
(with original banding date, sex, and current age):
Carolina Chickadee (1)
06/03/14--6th year male

Northern Cardinal (1)
09/26/18--after 2nd year female

Tufted Titmouse (2)
07/27/18--2nd year male
10/13/18--2nd year female

House Finch (1)
10/
29/18--2nd year male

Carolina Wren (1)
01/18/18--after 2nd year female

OTHER NATURE NOTES:
-A rather old Carolina Chickadee recaptured locally on 12 Dec 2019 was in his sixth year, having been banded at Hilton Pond Center as a recent fledgling in Jun 2014.

--As of 13 Dec, the Center's 2019 Yard List stood at 95--about 56% of 171 avian species encountered locally since 1982. Incidentally, 94 of the species so far this year have been observed from the windows or porches of our old farmhouse! (We captured a small flock of Wild Turkeys on a trail cam.) 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. You, too, can be a "citizen scientist." New species observed during the period: Red-tailed Hawk.

--Our immediate past installment of "This Week at Hilton Pond" was about Keeping Birds Warm In Winter. It's archived and always available on the Center's Web site as Installment #705.

All text & photos © Hilton Pond Center



Oct 15 to Mar 15:
East of the Rockies please report your sightings of
Vagrant & Winter Hummingbirds

(immature male Rufous Hummingbird at right)


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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.