Tuesday, July 22, 2008

Non-Migrating Wood-Warblers?

Yes.......

....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.)

4 comments:

Anonymous said...

(Here's the temporary spot to read the answer to the above headline question. After I fix this blog's software problem, the below text will appear where it should as regular text, and I'll eliminate this comment.)

"Non-Migrating Wood-Warblers?"

Yes, as it’s easy to overlook the fact that approximately116 species
of wood-warblers occur in the Parulidae family.

Perhaps that’s because many of us are pounding our chest with elation when spring migration yields a “mere” 30 or 40 total species detections.

But the fact remains:

The vast majority of Parulidae family members do NOT migrate and live year-round in the tropics. They 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, among others) 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 within every one of the lower 48 USA states.)

Beyond CA, FL, TX and some southeastern states, even mid-Atlantic, New England and upper Midwest states sometimes 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.
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.

What about the other 64 remaining tropical resident species? -- the majority of the family members that do not migrate. These species’ life histories within the tropics feature some distinct differences from their migrating first-cousins (e.g., Blackpoll), 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.)

Anonymous said...

Thanx. I didn't know much about this situation till today. Stumbled upon your site with a search.

Peter S.

Anonymous said...

Which state has the most number of nesting warblers?

Is it one near the Appalachians? Or a northern one?

Franz

Anonymous said...

nice blog!