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The American Ornithologists' Union
<br />Number of territories declines through winter;
<br />14% to 20% of territories in Yaquina estuary are
<br />defended by juveniles in Oct, but none in winter
<br />(Bayer 1978). On the Fraser River Delta, BC, adult
<br />females and juveniles feed nonterritorially on
<br />beaches, estuarine marshes, and in fields in winter,
<br />while adult males defend year -round feeding
<br />territories (Butler 1991).
<br />SEXUAL BEHAVIOR
<br />Mating system and sex ratio. Mostly mono-
<br />gamous. Birds: choose new mates each year
<br />(Simpson 1984).
<br />Pair bond. Elaborate courtship displays;
<br />described in detail by Meyerriecks (1960) and
<br />Mock (1976,1979,1980). Much variation between
<br />individuals and in sequence of displays. Mock
<br />(1976) describes pair formation displays as follows.
<br />Stretch display (Fig. 2b): unpaired males extend
<br />neck, raise bill toward vertical, and erect neck
<br />plumes while exhibiting bright soft parts; neck
<br />then retracted, accompanied by a moaning goo-goo
<br />call (see Sounds: vocalizations). Snap display:
<br />erected head, neck, and breast plumes as head is
<br />lowered; mandibles are clapped together and legs
<br />flexed when the neck is nearly straight. Wing
<br />Preen display: bird leans forward, opens wing
<br />slightly, runs bill along edge of primaries. Cirde
<br />Flights: heron flies laboriously in wide circle above
<br />colony with its neck outstretched. Landing call:
<br />when heron returns to nest, neck and head plumes
<br />erect; utters a series of croaks (see Sounds:
<br />vocalizations). Twig Shake: heron grasps a twig
<br />on the nest tree and shakes it side -to -side. Crest
<br />Raising: erects black occipital plumes. Fluffed Neck
<br />display: heron raises head, erects neck feathers,
<br />holds bill at or slightly above horizontal. Upright
<br />display: neck and bill extended in a straight line
<br />about 45° above the horizontal. Arched Neck
<br />display: rapid erection of plumes while curving
<br />neck so bill points downwards. Forward display
<br />(Fig. 2a) heron extends wrists fromits sides, retracts
<br />neck on to back, erects all plumes, then stabs
<br />forward with the bill, squawks and claps bill. Bill
<br />Duels (Fig. 2c): paired male erects plumage, stands
<br />tall, and lunges at the face of its mate with wings
<br />held away from its body and a dosed bill. Bill
<br />Clappering: rapid clicking of bill tips in mid air,
<br />directed toward mate.
<br />These displays not rigidly organized into
<br />predictable sequences (Mock 1976). Three
<br />sequences seen most often by Mock (1976) were
<br />the Greeting Ceremony, Stick Transfer, and Nest
<br />Relief Ceremony. The Greeting Ceremony occurs
<br />when a heron joining its mate on the nest gives the
<br />Landing Call. The bird on the nest usually responds
<br />with a Full Stretch or, less often, an Arched Neck
<br />ROBERT W. BUTLER
<br />or Fluffed Neck display. The Stick Transfer
<br />sequence occurs when the male brings sticks to its
<br />mate. She performs the stretch display and takes
<br />the sticks. The male then Bill Clappers the female
<br />as she places the stick in the nest. During the Nest
<br />Relief sequence an arriving heron utters the
<br />Landing Call and its mate stands followed by a
<br />Full Stretch. Often the pair Bill Clapper, preen,
<br />and even sleep before departure takes place.
<br />COPULATION
<br />Mostly morning and evening because females
<br />ate away from nests midday. Few or no displays
<br />(Mock 1976); occurs mostly on nest. Male places
<br />one foot gently in centre of female's back: Female
<br />leans forward, bends ankles slightly, holds wings
<br />slightly away from sides. Male grasps female's
<br />humeri with toes and lowers himself onto his tarsi,
<br />often while flapping his wings. The female moves
<br />her rectrices to one side while the male wags his
<br />lowered tail over her cloaca. He grasps her head or
<br />neck while copulating, then steps off the female.
<br />Extra -pair copulations rare (Cottrille and Cottrille
<br />1958, Brandman 1976, Mock 1976, I. Moul pers.
<br />comm.).
<br />SOCIAL AND INTERSPECIFIC BEHAVIOR
<br />Degree of sociality. Forages alone (Kushlan et
<br />al. 1985) or in loose flocks throughout year (see
<br />Spacing). Roosts alone or in loose flocks, on the
<br />ground during day, above ground at night.
<br />Hypothesis that colonies serve as information
<br />centres for location of food patches is not well
<br />supported (Mock et al. 1988).
<br />Play. Nestlings and fledglings stab at inanimate
<br />objects; adult play is undocumented.
<br />Interactions other than predation with
<br />members of other species. Utters mobbing calls
<br />toward mammalian and avian predators. Mobbed
<br />while flying by nesting gulls and chased by nesting
<br />Ospreys (Pandion haliaetus). Bald Eagles; Bayer
<br />1979), Turkey Vultures (Cathartes aura; Kushlan
<br />1978), and (rarely) gulls (Bayer 1985b, Quinney et
<br />al. 1981) steal large food items. In turn, steals food
<br />from gulls (Bayer 1985b) and (rarely) fish from
<br />Osprey nests (A. Poole pers. comm.). Catches fish
<br />driven near shore by Double- crested Cormorants
<br />(RW B): Occasionally feeds with other ciconiiformes
<br />(Kushlan 1978) and larids (Bayer 1985b). Its'nests
<br />used by Canada Geese (Branta canadensis), House
<br />Sparrows (Passer domesticus), and Great -horned
<br />Owls (Bubo virginianus; Vermeer 1969, RWB).
<br />Recovery of beaver (Castor canadensis) populations
<br />in rte. U.S. and in s. Canada has benefited this
<br />species by providing additional nesting and
<br />foraging areas (e.g., N.Y. State; Andrle and Carroll
<br />1988).
<br />The Academy of Natural Sciences of Philadelphia
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