EA 115 – Field Ornithology – Class VI

Last week’s class focused on Dowitchers, two devlishly-difficult birds to tell apart, although Dowitchers aren’t too difficult to tell from other shorebirds.

We first talked about Flood & Waverly, an area east of Stockton in California’s Central Valley that is known for having good birds. A classmate recently saw a Short-eared Owl, Ferruginous Hawk, Rough-legged Hawk, American Kestrel, Red-tailed Hawk, Bald Eagle, and Golden Eagle in an afternoon (must’ve been nice!). Other areas of high raptor concentration include the Altamont Pass region (famous locally for its windmill farms, which are killing Golden Eagles), Grizzly Island, and Robinson Road in eastern Solano County, which is also a good place for Mountain Plovers.

We picked up on pg. 188 of the National Geographic Field Guide to North American Birds.

Dowitchers:

• 2 nearly-identical species, Long- and Short-billed. It’s tempting to just call of them “Dowitcher sp.” (this is what I do on my website!)
• it’s not always possible to tell them apart, especially in winter
• they used to be one species, the “Dowitcher,” with Long- and Short-billed subspecies, Short-billed being eastern and Long-billed being western until a researcher found many “eastern” Short-billed Dowitchers in the SF Bay Area, and ensuing research resulted in the species being split (I think I preferred it being one!).
• both species appear regularly in California as migrants and wintering birds
• have a white wedge on their back, unlike any other American shorebirds (other Eurasian birds have this, though, so this mark isn’t helpful across the pond)
• call notes are diagnostic, if heard
• juveniles are easy to tell apart, alternate-plumaged adults are difficult, and basic-plumaged birds are nearly impossible to separate, unless heard
• female is larger and longer-billed on both species
• contrary to what you might think from their names, bill length is all but useless to separate these birds, as there is much overlap in length between them. Male Long-billed Dowitchers’ bill length is the same length range as either sex of Short-billed Dowitcher.

Long-billed Dowitcher (LBDO):

• is a shorter-distance migrant than the Short-billed Dowitcher
• migrate later than Short-billed, especially juveniles
• prefers fresh water, flooded fields, marshes, estuaries, and creek mouths
• forage on emergent vegetation
• juveniles migrate through California starting the 2nd week of September
• more common in SF Bay Area Christmas Bird Counts than Short-billed

Short-billed Dowitcher (SBDO):

• all Dowitcher records south of the Equator are Short-billed
• there are 3 subspecies, but we will not go there 🙂
• found mainly in tidal mudflats, where they forage
• juveniles migrate through California in July/August
• do not stop to molt, whereas Long-billed molt en-route to the wintering grounds. Unfortunately for us in the SF Bay Area, both species overwinter here, so this isn’t any help.

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