About the Cover — W E B E X T

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ABOUT THE COVER — W EB E XTRA

Text by Kevin T. Karlson Front Cover Photo All photos by © Kevin T. Karlson Semipalmated Sandpipers are particularly aggressive dur - ing spring and fall migration, frequently engaging in he identification of certain small calidris sandpipers squabbles with neighboring small sandpipers for preferred has confounded birders for many years. In North feeding space. Although they typically confront con - TAmerica, we typically refer to five of these small sand - specifics, other species—especially Least and Western pipers as “peeps”: Least, Semipalmated, Western, Baird’s, Sandpipers—are sometimes recipients of this aggressive and White-rumped Sandpipers. In Britain and elsewhere, behavior. Aggressive body language includes raising the the terminology and classifications are a little different, but back feathers and tertials, crouching menacingly with the we will here refer to these five species as “peeps.” head bowed and tail raised, and even leaping above the en - One reason for continued confusion with “peep” sand - emy and landing on its back, all the while pecking and pipers is that birders concentrate on continually changing stabbing the foe. New York, August. plumage field marks for their answers to identification dilemmas. On a given day from late July to early October, Flap Photo 1 most of these small sandpipers can show a number of vari - This juvenile Least Sandpiper is feeding on a mat of algae able plumage characters, depending upon age and molt. in shallow water, using its wings to keep from sinking. Be - Differences in plumage may be dramatic, with all of the fol - cause of its light weight and small size (Least Sandpiper is lowing possibilities: (1) fresh juvenal plumage, (2) transi - the smallest shorebird in the world), it can feed in margin - tion from juvenal to first-winter (formative) plumage, (3) al habitats that larger shorebirds cannot. The brownish sec - first-winter (formative) plumage, (4) worn adult breeding ondaries and dusky flight feathers are good field marks for (alternate) plumage, (5) transition from breeding (alter - Least Sandpiper at all ages. This dark underwing pattern nate) to nonbreeding (basic) plumage, (6) adult nonbreed - differs from that of the four other peeps, and is surprising - ing (basic) plumage, and (7) first-summer (first-alternate) ly obvious on flying birds. plumage. All in one species! New York, August. This may sound very confusing—and it is. A helpful al - ternative to just looking at feathers and plumage patterns Flap Photo 2 is to learn and understand body shapes and structural fea - This photo of a juvenile Baird’s Sandpiper shows the dis - tures of each species, and combine those impressions with tinctive attenuated (long and tapered) body shape and long specific “body language” that each species shows due to its wings of the species. Compared to White-rumped Sand - structural features. Such impressions rarely change with a piper, which is similar in juvenile plumage, Baird’s has bird’s age or with time of year, and they are very helpful slightly longer wings, a steeper forehead, a straighter and with field identification. more fine-tipped bill, a more slender body shape, and of - Cameron Cox has taken this approach to another level in ten a more upright body posture. Baird’s also retains its ju - his article on feeding styles and body language of these venal plumage later than White-rumped, waiting until it small sandpipers. Anyone with an open mind and discern - reaches the wintering grounds in South America to molt. ing observation skills can find additional helpful ID clues, New Jersey, October. whether behavioral or related to body language and struc - tural features. All it takes is patience and dedicated obser - Flap Photo 3 vation and study of similar species. Many hypotheses will This bird is showing the characteristic body language of a turn out to be helpful in certain situations, but not others, feeding White-rumped Sandpiper, with its body tilted up - due to variations within the species, but some will hold ward to the rear and its tail raised. This posture alone en - true in virtually all conditions. Photos can be particularly ables birders to pick a White-rumped out in a crowd of misleading because they capture only a split second of feeding small shorebirds. Typical White-rumped structure structure and behavior, but field observation will give a is evident: the bulky chest, the tapered body shape, and the total picture of body shape, structural features, and body long wings projecting slightly past the tail. First-summer language. plumage shown here includes a mixture of plumages

5w1 BIRDING • JULY/AUGUST 2008 (feathers of different generations) on the upperparts, in - take place, this behavior may be exhibited by numerous cluding: nonbreeding-plumage (basic) feathers (for exam - birds feeding in the same location without incident. ple, the scapulars); scattered breeding-plumage (alternate) Texas, April. feathers; some intermediate feathers (showing features of both breeding and nonbreeding feathers) from the spring Flap Photo 5 molt; and worn retained juvenal wing coverts, tertials, and This juvenile Semipalmated Sandpiper is also showing rectrices. The atypical pale leg color probably reﬂects low typical territorial feeding behavior, similar to the breeding sexual hormone levels. Western in Flap Photo 4. Semipalmateds are particularly New York, September. aggressive toward each other at feeding locations during migration, with even juveniles, as depicted here, showing Flap Photo 4 aggressive behavior. Body language includes the following: This breeding-plumage (alternate) Western Sandpiper the rear of the bird tilted upward; bent legs with a shows characteristic territorial feeding behavior exhibited crouched posture overall; and raised tertials and scapulars. by migrating birds with elevated hormone levels. When Frequent squabbles result when birds encounter each oth - feeding in close proximity to other Westerns, birds will of - er, resulting in short ﬁghts to establish dominance for a ten crouch on bent legs, tilt their bodies forward, and raise particular feeding space. Typical juvenal plumage is shown their tails in an aggressive posture. They will also raise their here, with neatly arranged, uniform, crisp, pale, fringed tertials and some scapulars to further accentuate their dom - upperparts that impart a scaly appearance. inance for feeding space. While occasional squabbles might New York, August.