Friday, December 28, 2007

Short-eareds at Jake's, plus subspecies and splits in white-crowneds, crossbills, and Savannah Sparrows

Word is that a half dozen or more Short-eared Owls were up and about at Jake's Landing last night, with over a dozen harriers, plus the usual Clapper Rails, Marsh Wrens, and a Seaside Sparrow. Evenings with light winds are always the best for the Short-eareds.

In the last hotline I reported that amongst the White-crowned Sparrows at the Cape May Migratory Bird Refuge was an apparent gambellii (as reported by Michael O'Brien), thus delving into an area that sometimes can cause eyes to glaze over or the sudden desire to look at large, easy-to-identify birds: subspecies.

The "normal" White-crowned for our area is the nominate subspecies leucophrys, which the big Sibley guide calls the east taiga form. Gambellii, the west taiga form, has pale lores and an orangy bill, while our usual birds have dark lores and pink bills. Gambellii are really rare in Cape May, and the word "apparent" is used because there are intergrades between the subspecies, which is why they are subspecies and not likely candidates for splitting.

A candidate for splitting did appear in the recent hotline, however: Red Crossbill. Nine types or populations of Red crossbills have been identified, perhaps representing multiple species. In the east we only need deal with types 2, 3 and 4, unless we're in the southern Appalachians (type 1) or Newfoundland (type 8). Again reported by Michael, these were 17 birds of type 4 and one type 2. I'm presuming Michael separated them by call, since in the other key mark, bill size, these two types differ by only about 1.5 mm. Type 4 has a prounced rising inflection to its call, while Type 2's call descends. Big Sibley treats the different types, and the flight calls CD has examples of the eastern types. They do sound distinctive if you've spent some time training your ear to hear subtle differences between single notes.

Yet another someday-maybe split is a bird that once was treated as a separate species: "Ipswich" Savannah Sparrow, the larger, paler form of Savannah that winters on coastal dunes. I saw one of these in the dunes at the north side of the Cape May ferry terminal last Sunday, when I was looking for the Black Guillemot. Ipswich Sparrows are isolated from other Savannah Sparrows during the breeding season, and they are distinctive in appearance, certainly moreso than, say, Willow and Alder Flycatchers. Besides being larger and paler, try noticing this fact: Ipswich Sparrows almost always walk, and Savannah Sparrows almost always hop.

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