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Fall Migrations: Shorebirds of California

Golden Gate Audubon SocietyEddie Bartley

eddie@naturetrip.com

Shorebird Plumage and Molt:

Life HistorySnowy Plover

Charadrius nivosus

Killdeer

Charadrius vociferusSemipalmated Plover

Charadrius semipalmatus

Complex Alternate Strategy?

or

Complex Basic Strategy?

Complex Alternate Strategies

But timing different

complete prebasic molts

partial preformative molt

limited prealternate molts

in both first and definitive cycles

Simple Alternate Strategy

complete prebasic molts

a single, protracted, partial-to-

incomplete molt in the first cycle

partial prealternate molt in the

definitive cycle

Black-bellied Plover

Pluvialis squatarola

Least Sandpiper

Calidris minutilla

Western Sandpiper

Calidris occidentalis

Complex Alternate Strategy

Hatchlings: Precocial and downy

Juvenile Plumage: Prejuvenile molt complete

Basic I Plumage: Birds do not appear to molt

prior to their first migration however, Maxwell

(in Senner and Howe 1984) states that molt

may be completed during migration at

migratory staging areas

Alternate I Plumage: Prealternate I molt

partial to incomplete

Complex Alternate StrategyHatchlings: Precocial and downy

Prejuvenile (First Prebasic) Molt:

Complete, primarily Jun–Jul, on or near natal territory

Preformative Molt: Partial to incomplete, Aug–Dec/Feb

First Prealternate Molt: Limited to partial, Mar–May

Definitive Prebasic Molt: Complete, primarily Jun–Nov

Definitive Prealternate Molt: Partial, primarily Feb–Apr

Juv., July 31 Adult, August 2

Juv., August 27 Adult, August 27

Cryptic Plumage strategies of Shorebirds

• Countershading: dark on back, gradually

become lighter towards the belly

Cryptic Plumage strategies of Shorebirds

• Disruptive Coloration: striking

patterns to breakup the outline

Cryptic Plumage strategies of Shorebirds

• The extreme crypticism is when birds take

on the color of their typical background

Self-Identification by plumage in Shorebirds

• Birds use color and

pattern to hold

themselves together

with other flock

members

Long-billed Curlew 23

Marbled Godwit 18

American Avocet 18

Whimbrel 17.5

Willet 15

Greater Yellowlegs 14

Black-necked Stilt 14

Long-billed Dowitcher 11.5

Short-billed Dowitcher 11

Ruddy Turnstone 9.5

Black Turnstone 9.2

Dunlin 8.5

Sanderling 8

Western Sandpiper 6.5

Least Sandpiper 6

~Measurements in inches

Tip of bill to end of tail

National Geographic

Field guide to the

Birds of North America

Relative size of our local Shorebirds