EA 115 – Field Ornithology – Class IV

28 November, 2007 by Adam R. Paul

Oops, guess I’d better post my notes from class 2 weeks ago before I get farther behind with tonight’s class!

We started with a review of ageing shorebirds (Sibley Guide to Birds, pg 181).

– Joe highly recommends “Sibley’s Birding Basics” for its discussion of molt sequences (I second this recommendation – despite the word “basic” in its title, nearly anyone could learn a thing or three from it!)

juvenal – 1st full set of feathers acquired. Note funky spelling of “juvenal” – equivalent to the more common “juvenile,” which means any young bird when used as a noun. “Juvenal” is only used as an adjective to describe plumage. In the US, not in the UK. Horray for language standards!
- worn juvenal is faded/bleached-looking compared to fresh juvenal
1st winter plumage is often very plain
basic plumage is acquired by molting all feathers
alternate plumage (if present – not all birds have one) is a partial molt – typically the flight feathers (primaries, secondaries, tail feathres) are retained
molts are named for the plumage being molted into (eg. pre-basic, pre-alternate)
the usual sequence is: juvenal -> partial molt -> first “basic” -> partial molt -> 1st alternate (note the remiges (flight feathers) are not molted in any of the above and also that the 1st alternate plumage is often “washed out” or “dilute” due to the young birds not quite having adult hormone levels).
- The first molt of a juvenal is not the pre-1st basic molt, since not all feathers are of the same generation at the end of the molt (the juvenal remiges are retained. This molt is referred to as the “pre-formative molt” and the “first basic” plumage is more properly called the “formative plumage”
“definitive basic plumage” – the first full basic set of feathers acquired, after which the bird cannot be reliably aged. This is the 2nd year plumage for most birds, except for 4-year gulls and the like.

– Juveniles often look more “sculpted” and “neater”

– Alternate-plumaged adults have a more complex pattern than juveniles

On to our field trip to Coyote Point (see my blog post here). ~20 new birds were added to the cumulative list for this trip, but this isn’t surprising, since this was only the second year this trip has been done in the fall semester.

We picked up on shorebirds on pg. 186 of the National Geographic Field Guide to the Birds of North America.

Pectoral Sandpiper (PESA)

Pectoral Sandpiper on our field trip to Rodeo Lagoon in late September

migrant in California in fall, few in spring
looks like an oversized Least Sandpiper (LESA)
male is ~50% heavier than female
brown with white supercilium in front of eye
heavily-streaked chest with a sharp line demarcating where the streaks end is diagnostic in all plumages
male has a large air sac that they inflate on breeding grounds to impress the ladies
are long-distance migrants, mostly through the Mississippi Valley
we mostly get juvenile birds, mostly in September, migrating through
they prefer freshwater habitat – estuaries, lagoons, etc
juvenile has a streaked breast on a buffy background
have a pale striping on the back, similar to LESA
unlike LESA, has some primary projection
yellowish legs
long toes – don’t confuse with Long-toed Stint!
head pattern varies
little or no wing stripe in flight
relatively late fall migrant – few August records in California
duller juveniles look like adults

Sharp-tailed Sandpiper (STSA)

is rare/accidental in California
has an eye ring, unlike PESA
has a pale bill base sometimes, but so does PESA, and STSA doesn’t always have it
has a redder head cap than PESA
smaller than PESA
less sexual size dimorphism (the sexes are closer in size than in PESA)
replaces PESA breeding in Siberia and wintering in Australia
when seen, they’re usually in PESA flocks
California records are nearly all juveniles
are rare in any plumage, very rare in alternate plumage
have markings down onto flanks, which are spot/scallop-shaped
mantle is about the same as PESA, but brighter on average
supercilium extends behind eye more prominently than PESA
about the size of a Dunlin
rich buf/peach colored chest w/o a lot of streaking – streaks often confined to a “necklace” below chin
throat and lower face sometimes white’ish in juveniles
named because central tail feathers are longer than outer tail feathers – not at all a useful indicator in the field.
peak later than PESA, in late Oct/early Nov
often appear to have shorter neck than PESA
juveniles have been seen migrating through SF Bay Area as late as January
undertail coverts are streaked on STSA, rarely, if ever, in PESA, but undertail coverts are difficult to see on these birds
chest streaking stops before the buffy color wash does, unlike PESA