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The American Ornithologists' Union
<br />of 81 d (range 64-91 d), chicks of late - nesting pairs
<br />at mean of 67 d.
<br />PARENTAL CARE
<br />Brooding. Shared by both parents (see Behavior
<br />self maintenance). Begins immediately after
<br />hatching and lasts 3 to 4 wk (RWB).
<br />Feeding. Both parents feed chicks (see Behavior.
<br />self maintenance). Newly hatched chicks peck at
<br />adult's bill, the nest, and each other (Pratt 1970).
<br />Adult stands on rim of nest and places food in
<br />open bill of chicks ( Cottrille and Cottrille 1958). By
<br />end of second week, chicks grasp adult's bill
<br />momentarily; by the end of the third week, until
<br />they leave nest, chicks pull adult's bill into the nest
<br />(Pratt 1970). Sometimes they reach into adult's
<br />open mouth (Cottrille and Cottrille 1958). Largest
<br />chicks get most food (Mock 1985, 1986, 1987).
<br />Chicks also eat regurgitated food dropped by
<br />parents in nest for up to about 30 d after hatching,
<br />then take food directly from parents (Mock 1987).
<br />Food remains eaten by parents.
<br />Aggression between nestmates is low and not
<br />related to brood size (Mock et al. 1987a). Brood
<br />reduction is apparently not mediated by hunger
<br />of nestmates but by size of prey items delivered by
<br />parents (Mock et al. 1987b). Chicks fed small prey
<br />compete to monolopize food boluses and fight
<br />with nest mates more frequently than chicks fed
<br />large prey items.
<br />Two - day -old chicks fed 10 times in 13 h, 6-d-
<br />old chicks more variable: 6 times in 13 h, twice in
<br />15 h (Pratt 1970). Number of feeding visits /h
<br />peaked at about 29 d after hatch, lowest rate
<br />several weeks before fledging (Dowd and Flake
<br />1985b).
<br />Nest sanitation. Most eggshells thrown from
<br />nests (Brandman 1976). Feces, partly eaten prey,
<br />and dead chicks remain in nest and on ground
<br />below. Chicks sometimes regurgitate into nest or
<br />onto ground below when disturbed (RWB).
<br />Parental carrying of young. Not known to occur.
<br />COOPERATIVE BREEDING
<br />Not known to occur.
<br />BROOD PARASITISM
<br />Not known to occur.
<br />FLEDGLING STAGE
<br />Departure from the nest. Age at first flight:
<br />Alberta, 52.6 d (range 51 -54 d, Vermeer 1969), 7 to
<br />8 wk in Oregon (Werschkul et a1.1977) and Nova
<br />Scotia (Quinney and Smith 1979). First flight as
<br />early as 60 d, mean of 81 d, in California (Pratt
<br />1970).
<br />• Growth. See above: Breeding: young birds.
<br />ROBERT W. BUTLER 11
<br />Associations with parents or other young.
<br />Fledglings return to nest to be fed by adults for a
<br />further 3 wk ( Quinney and Smith 1979). Fledglings
<br />in British Columbia follow adults from the foraging
<br />grounds to the nest to be fed, or return to nest
<br />alone (RWB).
<br />Ability to get around, feed, and care for self.
<br />First flights clumsy but improve rapidly. Foraging
<br />skills poorer than adults (Quinney and Smith
<br />1980, Butler 1991). Strike and pace rates similar to
<br />adults but capture rates about half of adults during
<br />2 mo following nest departure ( Quinney and Smith
<br />1991, Butler 1991).
<br />IMMATURE STAGE
<br />Independent of adults a few weeks after first
<br />flight. Wander in late summer. Forage with adults
<br />on beaches in British Columbia until about Oct,
<br />after which juveniles feed in grasslands and
<br />marshlands (Butler 1991).
<br />DEMOGRAPHY AND POPULATIONS
<br />MEASURES OF BREEDING ACTIVITY
<br />Age at first breeding; intervals between
<br />breeding. Most apparently breed in second spring
<br />(i.e. > 22 mo), based upon plumage, but this
<br />conclusion might reflect ability of observers to age
<br />herons. Juvenile plumaged birds have attempted
<br />to breed (Pratt 1973, RWB).
<br />Clfitchf2 to 6 eggs; generally increases with
<br />latitude. Great Blue: California, mean = 3.16, SE =
<br />0.04, n = 297 (Pratt and Winkler 1985); Oregon
<br />mean = 4.19, SD not given, n = 32 (Henny and
<br />Bethers 1971); Nova Scotia, mean = 4.2, SD = 0.8, n
<br />= 36 (McAloney 1973); Quebec, weighted mean =
<br />4.1, n = 77 (data in DesGranges 1979); British
<br />Columbia, mean = 4.2, SD = 0.6, n = 23 (Butler
<br />1989); Alberta, mean = 5.0, SD not given, n = 11
<br />(Vermeer 1969). Decreases through season (Pratt
<br />and Winkler 1985).
<br />Great White: Florida, mean = 2.9, SD = 0.6, n =
<br />64 (Powell 1983);
<br />Annual and lifetime reproductive success.
<br />Annual success based on number of nests with
<br />eggs varies widely. Most authors, however, report
<br />only the number of fledged young per successful
<br />nest (nest fledging young), which shows small
<br />annual variation: mean of means 2.3 young /nest
<br />(SD = 0.30, n = 16 studies, RWB). Future studies
<br />should determine number of fledglings raised per
<br />nesting attempt. Lifetime reproductive success
<br />unknown.
<br />Most researchers have been unable to see into
<br />nests so causes of chick loss remain poorly known.
<br />The average reproductive success (mean number
<br />The Academy of Natural Sciences of Philadelphia
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