Thursday, May 14, 2020

Savannah Sparrow

On 5 May 2020 at Mima Mounds Natural Area Preserve south of Olympia, Erika and I listed several Savannah Sparrows, Passerculus sandwichensis. This sparrow breeds across northern North America and south through the West through parts of Mexico. Northern birds winter across Mexico and the southern United States. Breeding birds tend to be darker and larger in the East and are smaller and paler as you go West, with each population tending to blend with adjoining groups. Over the years, at least 28 races of Savannah Sparrows have been named. Today about half of these subspecies are recognized. Molecular research suggests that a few of these races are actually separate, although similar, species—which is why birders should pay attention to subspecies. In the early 1960s, the Peterson field guide listed subspecies, which is one of the aspects of ornithology that intrigued me. My 1961 printing includes a discussion of subspecies. Peterson, claiming subspecies just confused the lay reader, abandoned these lists in later editions.

Because of its overall paleness and relatively gray back, I suspect the Savannah Sparrow in this photograph is P. s. brooksi, the race that breeds in the Pacific Northwest. At this time of year, however, P. s. anthinus should be migrating through this area on its way to Alaska or northern Canada. Most brooksi are smaller and paler than the northern race, but you really need them in hand to know (Wheelwright and Rising 2020).

No comments:

Post a Comment