THIS WEEK at HILTON POND
13-31 March 2011
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All text & photos © Hilton Pond Center

DIMINUTIVE DOWNY:
NORTH AMERICA'S
SMALLEST WOODPECKER

After nearly a month and a half studying Ruby-throated Hummingbirds on their Central American wintering grounds, we returned home this week to the Carolina Piedmont and Hilton Pond Center. Our backyard thermometer read 84 degrees--almost as warm as it was in Belize--but we were pretty sure this late winter "heat wave" soon would disappear. Even though it took a few days to get re-accustomed to watching White-throated Sparrows and Purple Finches rather than Jabiru storks and Long-tailed Manakins, we were quickly back to banding our usual winter resident birds. We were happy to see Pine Siskins were still consuming our thistle seeds; any more we captured would simply the record number banded so far this winter season.

All text & photos © Hilton Pond Center

We catch most of our winter finches--siskins, Purple and House Finches, and American Goldfinches--in a custom-made trap baited with sunflower seeds relished by all four species. Several other species also will enter the trap's one-way tunnels, allowing us to snare everything from Pine Warblers to Northern Cardinals to Carolina Chickadees. One day this week the feeder even caught a tuxedo-clad bird familiar to most feeder watchers across the U.S. and Canada--a black and white male Downy Woodpecker with red on its nape (above).

All text & photos © Hilton Pond Center
Downy Woodpecker map modified from one by Terry Sohl at www.sdakotabirds.com

Downy Woodpeckers are the smallest and third-most widely distributed of 22 extant woodpeckers in the U.S. and Canada. (To be honest we'd never tallied all our woodpecker species and were surprised to find there were 22 of them--23 before the Ivory-billed went extinct!) Downy Woodpeckers live year-round somewhere in every state except Hawaii (see map above), and they occur throughout Canada except the extreme Arctic regions. About the only places you won't find Downy Woodpeckers in the contiguous U.S. are West Texas and desert areas of the Southwest. For whatever reason, downies don't regularly get into Mexico--as do Hairy Woodpeckers (the downy's slightly larger relative) and the Northern Flicker (which has the widest range of all our woodpeckers). Downy Woodpeckers occur in wooded habitats that include deciduous trees potential nesting cavities; in dryer regions they tend to hang out along streams and river bottoms.

Here at Hilton Pond Center Downy Woodpeckers are by far the most commonly encountered member of the Picidae (Woodpecker Family), with 174 banded locally since 1982. Compare that to results for our five other picids: Red-bellied Woodpecker (80), Yellow-bellied Sapsucker (43), Northern Flicker (35), Hairy Woodpecker (24), and Pileated Woodpecker (just one). Cornell's Project FeederWatch lists Downy Woodpeckers as the fourth-most-commonly reported backyard species in North America.

All text & photos © Hilton Pond Center

Recently fledged Downy Woodpeckers look a bit different than adults. Their overall plumage tends to be fluffier and a tad brownish and they begin molting some of their flight feathers shortly after leaving the nest. Of special interest is that many nestling Downy Woodpeckers have red on their head, but on the crown rather than the nape as in adult males; this red is more extensive in nestling/fledgling males (above). We speculate the function of the red crown in young birds is to make them more visible to parents peering down at them in the darkness of the nest cavity.

All text & photos © Hilton Pond Center

Observers sometimes have trouble differentiating Downy Woodpeckers from the quite similar Hairy Woodpecker, but there are a few diagnostic characteristics. For one, the diminutive Downy is only about 5.75" long from bill tip to end of tail, while the Hairy is 7.5" long. (That's roughly the size difference between a White-throated Sparrow and a noticeably larger Northern Cardinal.) You should also consider bill size; in a Downy the bill is half the length of the head or shorter, while in a Hairy the mandibles are more than half the head length. In the photo above of a female Downy Woodpecker the bill length is distorted somewhat by the camera angle; note her complete lack of red head feathers.

All text & photos © Hilton Pond Center

Although all Downy Woodpeckers, Picoides pubescens, have black bars on their white outer tail feathers (underside view above), this character is not quite as diagnostic as many observers believe; a very small percentage of Hairy Woodpeckers, Picoides villosus, also have black tail spots, but the chance of encountering one of these birds is quite small. Despite the two species' external similarities, some ornithologists believe they are not very closely related and should be split into separate genera. Note, by the way, that the Downy's central tail feathers--aka rectrices--are long and quite stiff, providing a sort of tripod support when the bird's feet are gripping a tree trunk. (The rectrices in the photo above are quite worn, indicating they are old and have become abraded by rubbing against tree trunks all winter.)

All text & photos © Hilton Pond Center

And speaking of the feet of Downy Woodpeckers (above), these appendages are zygodactyl--meaning there are two toes in front and two in back. (Most birds are anisodactyl, with three front toes and a rear-facing toe, or hallux.) The woodpecker's outside toe has rotated back toward the hallux and has become the longest digit, a configuration that allows a woodpecker--in conjunction with its long decurved claws--to get a better grip on a vertical tree trunk.

Downy and Hairy Woodpeckers can also be differentiated by tree foraging behavior: The smaller Downy tends to feed on twigs and smaller branches of vines, shrubs, and trees (as depicted John James Audubon's painting at the top of this page that includes a Crossvine), while Hairy Woodpeckers seek insects on main limbs and trunks. Downy Woodpeckers also feed on berries and seeds and come readily to suet feeders in winter (banded male, above). The species even pecks on goldenrod galls and in winter forages in mixed flocks with chickadees, nuthatches, kinglets, and titmice. There is some indication local food resources are partitioned according to sex, with males feeding on thinner twigs in the canopy and females gravitating toward thicker branches in the understory.

All text & photos © Hilton Pond Center

We've heard some observers say Downy Woodpeckers have pronounced wing bars, but they do not. Wing bars are typically created when the tips of covert and lesser covert feathers are paler than the rest of the feathers. In a Downy, however, the spotted appearance of its wing is caused by actual spots (above), distributed evenly along the lead edges of the primary and secondary feathers. (Note, however, that tips of the secondary coverts DO bear white spots, as do bases of the primary coverts.) White spots are much less prominent on wings in the species' western and northwestern populations.

Downy Woodpeckers can make their nest cavities in limbs as small as 3"-4" in diameter, while the Hairy requires a somewhat larger branch. The Downy occasionally nests in a main trunk, as shown in the rendering at right from Illustrations of the Nests and Eggs of Birds of Ohio (1879-1886). Both species excavate their own nest holes and usually use them only for one year, after which the cavity can be taken over by any number of species including bluebirds, titmice, chickadees, and nuthatches. One Downy Woodpecker nest that successfully fledged four youngsters one year at Hilton Pond Center was occupied in successive springs by Eastern Bluebirds, Carolina Chickadees, and House Wrens. Among downies both parents share all dutues, including incubation, brooding, feding chicks, and nest sanitation. It's worth mentioning that male Downy Woodpeckers develop an "incubation patch"--an area of featherless skin on the belly that becomes vascularized and edematous and tranmits body heat very efficiently to eggs and chicks. In the vast majority of bird species, only the female develops an incubation patch; woodpeckers are one exception.

Downy Woodpeckers occasionally use nest boxes erected for bluebirds, but pairs seem to prefer excavating their own nest sites. (Be sure to use a 1.25" opening--Eastern Bluebird houses have a 1.5" hole--and add fresh wood chips to the bottom of nest boxes intended for Downy Woodpeckers.) The species also roosts in boxes during the colder months--a good reason to maintain those artificial cavities year-round. Incidentally, the longevity record for a free-flying downy is a banded male in California that lived at least 11 years and 11 months.

All text & photos © Hilton Pond Center

The male Downy Woodpecker we caught this week at Hilton Pond Center was more docile than most, so we were able to take lots of in-hand photos. Sometimes individuals are quite aggressive and peck away at our fingers and knuckles, causing numerous little puncture wounds and considerable pain. (Their claws are also very sharp and inflict serious scratches if we're not careful.) It's fortunate, as shown in the photo above, a Downy's upper mandible is slightly chisel-shaped rather than sharply pointed. A stilletto-like bill would cause much more damage to our hands, but it also would be more likely to wear or break as the woodpecker pecks wood. Right now we can hear a Downy pecking on an oak branch not far from our office window, but it is a loud, repetitive sound that indicates he's drumming for a mate rather than drilling for insects.

The photos above and at left reveal one final note you might not know about this week's spotlight species: Irises of the adult are a deep plum red--a colorful touch as this diminutive Downy Woodpecker watches us watch it at our feeders year-round at Hilton Pond Center.

All text & photos © Hilton Pond Center

"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

13-31 MARCH 2011

SPECIES BANDED THIS WEEK:
Ruby-throated Hummingbird--1*
American Goldfinch--41
Pine Siskin--38
Chipping Sparrow--12
Carolina Chickadee--1
Northern Cardinal--2
Purple Finch--26
Downy Woodpecker--1
*
House Finch--6

* = New species for 2011


WEEKLY BANDING TOTAL
9 species
128 individuals

2011 BANDING TOTAL
16 species
929 individuals

30-YEAR BANDING GRAND TOTAL
(since 28 June 1982, during which time 170 species have been observed on or over the property)
125 species (30-yr avg = 66.6)
55,806 individuals
(30-yr avg = 1,860)

NOTABLE RECAPTURES THIS WEEK
(with original banding date, sex, and current age):
Carolina Chickadee (1)
05/13/10--after 2nd year female

American Goldfinch (1)
01/05/08--5th year male

House Finch (1)
09/11/08--4th year male
12/31/09--after 2nd year male


Operation RubyThroat has teamed with EarthTrek so citizen scientists--like YOU--can contribute observations about hummingbird migration and nesting behavior. Membership is free for this great new opportunity to help increase scientific understanding of Ruby-throated Hummingbirds. Data entry forms for 2010-11 are on-line, so please register today at EarthTrek.

NOW is the time to report your 2010 RTHU fall departure dates for the U.S. & Canada, and fall arrival dates for Mexico & Central America.
Please participate.


OTHER NATURE NOTES:
Things happen fast in spring, and in the two weeks since we returned from the Neotropics a lot has occurred at Hilton Pond Center. Just a few springtime observations:

--Pink flowers of Eastern Redbuds have been replaced by the showy white bracts of Flowering Dogwoods, and leaves of Confederate (Blue) Violets have gone from the size of a nickel to 2" across. (Those violets are also in full bloom.)

--Despite the presence of four very finely constructed and precisely positioned cedar Wood Duck boxes on the edges Hilton Pond, the woodies are still walking along branches 60' up in our big White Oak tree, undoubtedly looking for some natural cavity that better suits their housekeeping instincts.

--We watched a Great Blue Heron grab a 12" Largemouth Bass and were amazed using only its bill the heron was able to shuffle the big fish into position and swallow it whole.

--The first Ruby-throated Hummingbird (an adult male) of 2011 showed up--and was trapped and banded--on 27 March. This ties the Center's all time early record for the species, set in 1991.

--Observers north of Hilton Pond Center should be on the lookout for our ruby-throats with GREEN color marks on their upper breasts/throats. There's also a possibility you might see our birds from Costa Rica (BLUE color marking), Guatemala (BLACK), or Belize (PURPLE). Please report any sightings immediately to RESEARCH, and document with a digital camera if you can.

--Personal note: Downy Woodpecker was one of the first species we identified through binoculars back in the mid-1970s when lifelong friend Jim Shuman was trying to get us interested in birdwatching. Thanks, Jim, and happy early 66th birthday!

--As mentioned in the photo essay above, we were surprised to find there are so many species (n=22) of woodpeckers in the U.S. and Canada--mostly because we'd never actually tallied them. How many can you name without consulting a reference? (Hint: Don't forget to include flickers and sapsuckers.)

All text & photos © Hilton Pond Center


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Oct 15 to Mar 15:
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(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 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.


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