Warbler Guy, do the white tail spots in the Hooded Warbler (and other warbler species) provide it any benefit?

Catrina (in Portland, OR), the answer is “yes,” if you agree with studies conducted by Dr. Ron Mumme. In the field, he tested his hypothesis that the Hooded Warbler’s (above photo courtesy of Dr. Mumme) contrasting white tail spots and tail-flicking behavior increase foraging performance by startling potential insect prey that the warblers then pursue and capture in flight.

Results of his experiment indicated that Hooded Warbler individuals with darkened tails had significantly lower prey attack rates and delivered significantly less food to nestlings than did birds with normal, unchanged tail feathers. He and other theorists continue to test their theory about the importance of contrasting tail pattern in helping birds capture prey, and, in doing so, note that all 12 species in the Myioborus redstarts (also known as whitestarts) display similar behavior while using their white outer tail feathers to also conduct foraging displays designed to startle and flush potential insect prey.

Warbler Guy, which warblers are superspecies?

That’s a fine question, Jeremy (in Boise, ID).

Given a superspecies consists of two or more species that evolved recently into isolated breeding ranges next to each other, it is not surprising that superspecies’ members are closely related.

Among songbirds, think of Eastern and Western Meadowlarks. Their breeding ranges are separated across North America and are nearly isolated except for a small overlap area. The same kind of breeding isolation geography pattern occurs in more than 100 North American species that are considered members of 53 total superspecies.

Of these 53, some wood-warbler species qualify. Note the distinct breeding ranges of the Black-throated Green superspecies consisting of this species along with Black-throated Gray, Hermit, Townsend’s, and Golden-cheeked Warbler.

Other warbler superspecies include 1) Nashville, Virginia’s, and Colima; 2) Northern and Tropical Parula; 3) Yellow-throated and Grace’s; and 4) Mourning and MacGillivray’s.

Given, I saw your 9/2/10 article here, what warbler identification resources exist?

Eddy in Chicago.......That's a good question.

Violating my own anti-shill policy, I'll suggest my own "Warbler Tips ID" chart (that is accessed at my web site's home page: www.warblerwatch.com)

This chart has a column that lists the look-alike species, in addition to mentioning 1) whether they are early to late spring arrivals/autumn departures during migration; 2) their conservation status; 3) other information.

The direct link to this warbler identification resource:

http://www.warblerwatch.com/warblertips.htm

Confusing Fall Warblers? Warbler Identification Tips?

People often ask me to share the best ways to identify migrating warblers — especially in the East and Midwest where post-breeding plumages can sometimes create identification challenges.

My brief answer is that there’s no replacement for doing your homework in the field. Getting out early and often with your binoculars is the best way to see lots of warblers. The more challenging identification episodes you encounter, the faster you become precise with your warbler field skills.

One identification resource I recently found may interest you. It’s an online “chart” that’s found at: http://www.migrationresearch.org/mbo/id/fall_warblers.html

The author, Marcel Gahbauer, does a terrific job of separating 30 species of warblers by various key feather field marks: a) presence of wingbars or not; and b) facial, throat, and undertail characteristics.

Enjoy your late summer and autumn birding!

Warbler Guy, which wood-warblers use cavities for nests?

Only two of our North American breeding wood-warblers use a cavity nest: Prothonotary (above photo) and Lucy’s.

Prothonotary nests usually occur in stumps and snags either standing in or near water. An old or abandoned woodpecker hole is typically employed, most often one previously occupied by a Downy Woodpecker or Black-capped/Carolina Chickadee. Nest heights range from 2 to 12 feet above ground or water, with an average of 5 feet in height. Prothonotaries occasionally nest in bird boxes and near buildings.

Lucy’s Warbler is the only cavity nesting warbler in the western USA. This species usually places its nest in four types of cavities: natural cavities in trees (usually mesquite) where the entrance is in a sheltered spot; under loose bark; in abandoned woodpecker holes (especially those of Gila Woodpecker (Melanerpes uropygialis) in saguaros [Carnegiea gigantean] or other trees); and in deserted Verdin (Auriparus flaviceps) nests. Lucy's Warbler occasionally nests in holes in banks, in soap tree yucca leaves (Yucca elata), elderberry (Sambucus mexicana), sycamore (Platanus spp.), or willow/

Lucy's Warbler rarely nests in burrows or depressions in river banks, rocky crevices, deserted thrasher (Toxostoma sp.) and Cliff Swallow (Hirundo pyrrhonota) nests, "pseudocavity" evacuated in mass of debris in tamarisk, or forks in small branches.

Warbler Guy, were any changes in warbler names recently applied?

Yes, David (in Topeka, KS), the 51st supplement to the AOU Checklist of North American Birds includes changes to warblers names, but mostly due to the creation of new genera.

The new supplement includes the following changes:

• Blue-winged Warbler Vermivora cyanoptera
Formerly Vermivora pinus
• Tennessee Warbler Oreothlypis peregrina
Formerly Vermivora peregrina
• Orange-crowned Warbler Oreothlypis celata
Formerly Vermivora celata
• Nashville Warbler Oreothlypis ruficapilla
Formerly Vermivora ruficapilla
• Virginia’s Warbler Oreothlypis virginiae
Formerly Vermivora virginiae
• Colima Warbler Oreothlypis crissalis
Formerly Vermivora crissalis
• Lucy’s Warbler Oreothlypis luciae
Formerly Vermivora luciae
• Northern Waterthrush Parkesia noveboracensis
Formerly Seiurus noveboracensis
• Louisiana Waterthrush Parkesia motacilla
Formerly Seiurus motacilla

Warbler Guy, which wood-warbler clutch has the largest number of eggs?

Good question, Parker in New York City.

The answer is the Cape May Warbler (see female in photo, above), which usually lays six or seven eggs. Most other wood-warbler species typically lay four or five eggs in most instances. In extraordinary cases (that are seldom to rare), the Cape May deposits as many as nine eggs. In equally rare situations, merely four are laid.

Why does the Cape May lay eggs than other wood-warbler species? The answer may relate to the “boom and bust” cycle of its dominant food resource: spruce budworms (a larval form of a moth). When large population outbreaks of the spruce budworm occur, it behooves the Cape May to lay more eggs. Conversely, it makes sense that this species lays fewer eggs in years when spruce budworms are less plentiful.

Of course, this kind of phenomenon is not unique to Cape May Warbler. Many other bird species, in addition to other animals, act similarly in response to the presence or absence of food resources.

For more details about clutch sizes of North American breeding wood-warbler, see The Birder’s Handbook (Paul R. Ehrlich, David S. Dobkin, and Darryl Wheye)

Other life cycle information about USA-breeding wood-warbler species appears in a “Warbler Tips ID Chart” at my Web site: www.warblerwatch.com (After arriving at this site’s home page, click on the button title “Warbler Tips ID Chart.”