Tuesday, July 22, 2008

Non-Migrating Wood-Warblers?


....and it’s easy to overlook the fact that the majority of approximately 116 wood-warbler species
(Parulidae family) do not migrate and live year-round in the tropics.

Approximately 64 species of wood-warblers never occur farther north than Mexico.

The true migrators (i.e., neotroprical migrants) – 52* wood-warbler species, such as the Blackburnian, Cerulean, Prothonotary, to name merely three -- with which we enjoy steeping our senses after (too) long winters are primarily breeding residents only within some of the lower 48 USA states.

Interestingly, some states (e.g., CA, TX, GA, FL, and a few southeastern USA states) host one or more wood-warbler species as either winter and/or permanent residents (e.g., The above photo features Common Yellowthroat, thanks to Martin Myers © whose image of this Nevada individual in April is one of 15 subspecies within the Common Yellowthroat species found throughout North America where it breeds in all of the lower 48 USA states.)

Even mid-Atlantic, New England and upper Midwest states regularly host small populations of wood-warbler species that remain year-round. Hardy species surviving northern latitude winters may typically include Yellow-rumped Warbler and Common Yellowthoat, and, less commonly, Yellow-breasted Chat and Palm Warbler. All four of these species are uncommonly to sometimes observed during annual Christmas Bird Counts (CBC) that occur in mid- to northern-latitude states. Whether CBC detections are simply truant individuals that eventually flee winters grip and move south remains uncertain from one year to the next.
But, if suitable micro-habitat conditions occur and the winter season is not too severe, then all four of the aforementioned species may remain during some years.

In general, and in sum, the greater northern latitudes host few numbers of and fewer non-breeding season wood-warblers than southern latitudes corresponding to, say, S. Carolina, Georgia, Florida and other southeastern states.

What about the other 64 remaining tropical resident species (that live primarily outside the USA)? -- the majority of which are wood-warbler species that do NOT migrate. These species’ life histories within the tropics feature some distinct differences from their migrating first-cousins (e.g., Blackpoll and other typical northern North America wood-warbler species), including:

1) tropical resident wood-warbler species tend to have sexes that exhibit the same plumages (unlike the Blackpoll where the female looks starkly different than the male); and 2) the most brilliant of the tropical wood-warbler species express the same bright colors throughout the year; 3) the nesting period for tropical wood-warbler species is often longer.

(* = Note that only 52 of the 116 wood-warblers (Parulidae family) are
typically reliably seen in the lower 48 USA states each year, according to "A Field Guide to Warblers of N. America" authors Jon L. Dunn & Kimball L. Garrett.)

Tuesday, July 8, 2008

New Kirtland’s Warbler Sighting in Wisconsin

. . . Federally endangered species reported in third WI county (Bayfield County) this breeding season (2008)

. . . To find the following article online as of 7/8/08, go to:

Nicolet National Forest
Wisconsin State Journal Reporter

A pair of Kirtland's warblers, one of the rarest North American birds, has been spotted for the first time in northern Wisconsin, the U.S. Fish and Wildlife Service confirmed last week.

"It's been a little more than 70 years since we've seen any presence of this particular bird," said Anthony Erba, deputy forest supervisor at Chequamegon-Nicolet National Forest in Bayfield County, where the birds were seen. "When you come across something that unexpected ... it's like, 'Whoa, there it is.' "

The Kirtland's warbler has been on the list of federally endangered species since 1967, and was only known to nest in Michigan until last year, when about eight males were spotted in southcentral Wisconsin and two in Canada.

Conservation efforts in Michigan have raised the population of the warblers, which are now expanding outward, said Kim Grveles, assistant ornithologist at the Wisconsin Department of Natural Resources' Bureau of Endangered Resources.

About 1,697 males were reported in Michigan in 2007, Grveles said, an increase of about 200 from 2006.

The population increase is mostly credited to efforts from Michigan's Kirtland's Warbler Recovery Team, a 40-year-old partnership between private groups and state agencies to manage jack pine, the birds' preferred habitat, for the expansion and nesting of the species in the state, Grveles said.

"Even though we have habitat — and high-quality habitat — for the bird, we just didn't have much confidence that the bird would make that much of a jump to northern Wisconsin," Erba said. "But now we have confirmed presence of this bird in Wisconsin, and that's very exciting for us."

"We started last year doing formal surveys, because we knew that with a population growing like that, they would start dispersing," said Scott Posner, a wildlife biologist at Chequamegon-Nicolet National Forest's Washburn Ranger District.

Now that warblers have been confirmed in the region, the next step is to survey the area during the next breeding season to see if the migrating birds are coming back, and then ensure there is suitable habitat for them to breed in the forest, Posner said.

"After that, we will continue monitoring to see what's needed for them," Posner added.

The DNR is talking with land managers about possible management options to encourage the species to come to Wisconsin to breed, Grveles said.

Wisconsin has one of the best opportunities in the Midwest for these birds to increase its population, she added.