01/30/2002 Env Bd Packet - Laserfiche WebLink

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The American Ornithologists' Union often than at other stages. Females snap bills when approaching bachelor males and after they have formed breeding pairs (Mock 1979). Possibly analogous to territorial song of passerines (Mock 1976). Bill clappering (Hancock and Kushlan 1984), a rapid chattering of the tips of the bill, is very common between paired birds; many other heron species also do it (Hancock and Kushlan 1984). BEHAVIOR LOCOMOTION Walking. Walks erect with long strides and wades in water, often up to belly or nearly so. Toes are spread as the foot is placed on the ground. Flight. Folds neck in S -shape and extends legs along the body axis on long flights. Extends neck and dangles legs when preparing to land, when chasing other herons, when startled (e.g., when pursued by Bald Eagles, Haliaeetus leucocephalus), and at colony -sites during courtship flights. Flies with deep, slow wingbeats at 2.3 to 3.2 beats /s; flight speed 30 to 46 km /h (Palmer 1962). Soars to great heights and glides occasionally. Capable of evasive maneuvers when pursued. SELF - MAINTENANCE Preening, head- scratching, stretching, etc. Powder downs on flanks and pectinated middle toe nail used for scratching are common to herons, including this species. Stands on one foot to scratch head by lifting leg over closed wing, erecting crest feathers, and lowering and twisting head in position where it can be reached by pectinate toe. Preens by sliding bill along feathers. Droops wing slightly when preening neck. Partly opens wing when preening underwing feathers. Shakes head, body, and finally tail in one motion. Cleans bill by wiping on branches or shaking. Sunbathing, thermoregulation, temperature metabolism. Droops and exposes inside of wings on sunny days, perhaps to radiate body heat on warm days and absorb solar radiation on cool days (Kahl 1971, Larkins 1989). 'Avoids strong winds by seeking shelter behind bushes, fences, etc. Leaves nest to drink on hot days (Pratt 1977). Sleeping and roosting. Roosts alone or in loose flocks of over 100 on the ground, in trees, and on man -made objects near feeding grounds during day. Some roosts used repeatedly. Sleeps at night in trees with dense foliage. Tucks bill under wing - coverts while asleep. Daily time budget. On Pacific Coast, activity controlled mostly by tides. Peak feeding activity near low tide (Brandman 1976, Bayer and ROBERT W. BUTLER McMahon 1981); pair formation, courtship, and nest building generally just before or after foraging (Brandman 1976). During pair formation male spends 100% of his nonforaging time at the nest (perhaps to guard against robbing of nest sticks), 50% to 60% during courtship, 100% during incu- bation, and 51 % at nest when chicks are > 4 to 5 wk old (Brandman 1976). Female spends 50 to 60% of her nonforaging time at nest during courtship, 100% brooding chicks < 4 to 5 wk old, and 31% with older chicks (Brandman 1976). Adult nest attentiveness declines from about 83% to 99% in the first week after hatching to near zero at 6 to 7 wk (Dowd and Flake 1985a). Feeding- activity peaks when chicks are 4-wk old; Males spend less time foraging and more time on the nest than females during the day (Brandman 1976); opposite at night. AGONISTIC BEHAVIOR Physical interactions. Individuals erect crest and fly toward conspecifics that approach within about 2 m of nests and nest sites; also jab such intruders with bill during courtship (see Fig. 2c). Thrust bill at herons that approach nest after eggs are laid. Communicative interactions. The rich repertory of courtship displays at the nest are described below (see Behavior: sexual); displays in this section described by Bayer (1984b). The most spectacular display given by herons on the foraging grounds is the "Upright and Spread Wing" display given when two herons approach one another; neck is nearly fully extended and tilted slightly over the back, head and bill are held above horizontal, wrists are drooped or held away from the body exposing the black shoulder patch of the adult. Sometimes wing nearest the opponent is drooped lower than the opposite wing and body plumes are erected. As opponents approach one another, head and bill are raised closer to the vertical and the neck extended farther over the back. These displays usually cause the two herons to move apart but occasionally bring a chase. This display is sometimes directed towards gulls (Larus sp.), Great Egrets (Casmerodius albus), and even people. A less spectacular display on the foraging grounds is the "Vertical" display (Bayer 1984b). A heron performing this display sleeks its plumage, extends the neck forward at about a 45 °, and tilts the head along its axis so its eyes alternately direct upwards. This behavior used when predators and herons fly at high altitudes over the foraging grounds. The "Forward and Full Forward" display entails partly folding the neck with the bill facing the opponent and partly erecting the body plumes. The Academy of Natural Sciences of Philadelphia