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YELLOW-THROATED WARBLER

When we think about spring warblers at Hilton Pond Center, what often comes to mind is getting a crick in the neck while trying to squint through binoculars at tiny hyperactive birds still for only an instant 'way up in the canopy. Indeed, many Wood Warblers zip through the Carolina Piedmont in April and May, presumably on their way to northern breeding grounds after spending only an hour or two gleaning newly emerged insect larvae from just-as-fresh leaf buds in the treetops high above us.

There ARE warblers that forage at or near ground level--Ovenbirds, Louisiana Waterthrushes, and Yellow-rumped Warblers are examples--but many members of the Wood Warbler group (Parulinae) are hard to catch for banding unless one finds a way to raise mist nets to heights where they are foraging. Alas, our nets at the Center are all low-standing, with the top edges a mere ten feet off the ground, so through the past 25 years we have seldom captured such warbler species as the canopy-dwelling Blackburnian (two since 1982), Black-throated Green (eight), and Yellow-throated (seven through 31 Mar 2006). This week we did manage to band one of the latter, but under unexpected circumstances.

All text & photos © Hilton Pond Center

Our first ever capture of a Yellow-throated Warbler at Hilton Pond was on 23 June 1985. The rest came in either spring (1992 & 1995) or fall (1987, 1992, 1994 & 2000). In every case these birds swooped low and got temporarily snared in a net. This week's Yellow-throated Warbler was a real surprise, however, since we caught it along with a Chipping Sparrow on the GROUND in a walk-in trap baited with cracked corn and white millet--NOT exactly a predicted habitat! We doubt the warbler was actually dining on vegetable matter; perhaps there were insects roiling around in the seed mix, or maybe the warbler was somehow attracted by the sparrow's movement in the trap. In any case we won't complain because it gave us a chance to view up-close our eighth-ever Yellow-throated Warbler.

Especially prevalent in South Carolina's Piedmont during migration months, Yellow-throated Warblers are known to breed across the state--most commonly in the Sandhills, Coastal Plain, and Savannah River Valley, with a few nesting records from lower elevations of the Mountain Province. We occasionally see them in summer at Hilton Pond--consider that first bird we banded in late June '85--but have never found a nest. Elsewhere they breed throughout the southeastern quadrant of the U.S., ranging primarily into Virginia and Pennsylvania, southern Illinois, and east Texas (see map of relative breeding abundance, above). In some northern areas--Wisconsin, for example--Yellow-throated Warblers are declining and are now so rare they are on state endangered species lists. Not so in the Atlantic Coastal Plain where this warbler often builds its nest in hanging mats of epiphytic Spanish Moss, Tillandsia usneoides. In other regions, pines and sycamores seem to be nest sites of preference.

The Yellow-throated Warbler's song is loud and boisterous and reminiscent of a Louisiana Waterthrush, Indigo Bunting, or Carolina Wren. John James Audubon--whose painting of the warbler is above right--had this to say:

The song of the Yellow-throated Warbler would please you, kind reader. Of this I have not a doubt, as it is soft and loud, and is continued for two or three minutes at a time, not unlike that of the Painted Finch, or Indigo-bird. As it is heard in all parts of our most dismal cypress swamps, it contributes to soothe the mind of a person whose occupation may lead him to such places. I never saw this species on the ground.

There are actually two accepted subspecies of Yellow-throated Warbler--one that breeds in the Atlantic Coast states and Alabama migrates to the Bahamas and Greater Antilles, and another that winters in Mexico and Central America. Yellow-throated Warblers rarely overwinter in south coastal South Carolina and Georgia but are rather common in central and South Florida from late fall through early spring.

Yellow-throated Warblers are a bit unusual among arboreal warblers in that males and females show little sexual dimorphism; i.e., the sexes have similar plumage. (In ground-feeding warblers such as Ovenbirds and the waterthrushes, sexual monomorphism is the rule.) Generally, black areas are more intense on male Yellow-throated Warblers, and females have somewhat less black on forehead and crown. Second-year males--those that hatched the preceding year--are a tad paler than older males, and their tails tend to be slightly browner and more worn (below). In all plumages, however, Yellow-throated Warblers fall into that group of warblers that have "wing bars and tail spots."

One species novice birders sometimes confuse with Yellow-throated Warblers is the closely related Magnolia Warbler, Dendroica magnolia (below left). Males of both species have a black mask and a partial white eye ring below the eye, but the Yellow-throated has a long white superciliary line that extends from the base of the bill to the nape; this line is much shorter in the Magnolia. In addition, the Magnolia's wing bar is quite wide and prominent, and the species exhibits a distinctive white band across its tail rather than just tail spots.

Although Yellow-throated Warblers sometimes capture insects by flycatching and by hovering and gleaning from leaves and twigs, more often they creep along limbs and climb vertical trunks of trees--a behavior they share among parulids only with the Black-and-White Warbler. After observing this behavior, early American naturalist and bird painter Mark Catesby called the species Yellow-throated "Creeper" instead of "Warbler."

Below is Catesby's 1815 rendering of the species perched among seeds of the Red Maple--a much more likely habitat than the ground trap in which we captured our Yellow-throated Warbler this week at Hilton Pond.

All text & photos © Hilton Pond Center
Breeding Bird Survey map courtesy USGS Patuxent Wildlife Research Center

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Be sure to scroll down for an account of all birds banded or recaptured during the week, plus other nature notes of interest.

"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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