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<br />
<br />63(3)
<br />
<br />,
<br />
<br />moving northw'd up the coast
<br />llifornia. In the past two winters
<br />eratures and snow (early Janaur;
<br />,t the Serpentine Fen, Surrey On
<br />n the delta area. The observers
<br />Ie cause of death was starvation.
<br />a have had greatly reduced bOdy
<br />s are subject to starvation.
<br />e delta area within the next few
<br />3.5 the Fraser Delta area seems to
<br />
<br />.-
<br />
<br />mcouver Natural History Society
<br />e Id notes on sightings. I am also
<br />Provincial Museum, courtesy of
<br />
<br />who reviewed the draft of the
<br />
<br />tine Fen which is the first spring
<br />; records for the province, single
<br />\t James, Queen Charlotte Island
<br />rgess).
<br />
<br />:0 November 1981.
<br />
<br />EGRET IN IDAHO
<br />
<br />fROST
<br />
<br />:15ion in the Western Hemisphere
<br />2:56-63). In much of the, United
<br />eding species.
<br />je by C. H. Trost on 1 July 1971.
<br />ed adjacent to Minidoka National
<br />;>astern Idaho. Cattle Egrets were
<br />.:i 20 June 1974 by J. Hill, refuge
<br />e reported a Cattle Egret in Rex-
<br />rets were seen at Minidoka NWR
<br />ir of Cattle Egrets were observed
<br />attle Egrets in breeding plumage
<br />ne 1978, On this same day, one
<br />'e leg band (Band No, 876-56034)
<br />ted, evidence presented indicates
<br />; the first record of Cattle Egrets
<br />
<br />,land near the southern shore of
<br />5ists primarily of dead trees artd
<br />The center of the island is void
<br />luded Double-crested Cormorant
<br />;ret (Egrdta thuIa), Black<rowned
<br />ifornicus).
<br />n a colony near the eastern shore
<br />:0. Two adult Cattle Egrets were
<br />'anded by C. H, Trost (Band Nos.
<br />
<br />
<br />WINTER 1982
<br />
<br />GENERAL N QTES
<br />
<br />89
<br />
<br />896-10314 and 896-10315). Nesting associates of Cattle Egrets' included Snowy Egrets and Black-
<br />crowned Night Herons. All nests were in willows (5alix sp.), Double-crested Cormorants and White-
<br />faced Ibis (PIegadis cJlihi) were also nesting at the eastern end of American Falls Reservoir but not
<br />in the immediate vicinity of the colony where Cattle Egrets were nesting. The following day one
<br />adult. Cattle Egret was observed on Gull Island, Lake Walcott, Minidoka NWR, indicating that
<br />Cattle Egrets may have nested at Minidoka NWR during 1981. The Cattle Egret appears to be
<br />becoming a well established breeding species in Ida~o,
<br />
<br />Acknowledgements.-Data on Cattle Egrets were'collected incidental to research supported by the
<br />Idaho Department of Health and Welfare, a Grant-in-Aid of Research from Sigma Xi, and the
<br />Biology Department, Idaho State University, We are grateful to the U.S. Fish and Wildlife Service
<br />for allowing us access to Minidoka NWR.
<br />
<br />DeparJment of Biology, Idaho State University, Pocatello, ID 83209. Present address (SF): 630 Papa Agie
<br />St., Lander, WY 82520. Accepted 14 April 1982.
<br />
<br />PREY MANIPULATION IN THE GREAT BLUE HERON
<br />
<br />L. S. FORBES
<br />
<br />The purpose of this paper is to describe the prey manipulation behaviors Prey Stabbing and
<br />Prey Mandibulation in the Great Blue Heron (Ardea herodias) and to discuss their possible functions.
<br />
<br />STUDY AREA AND METHODS
<br />Foraging Great Blue Herons were observed for over 600 hrs during the nesting season from 1979
<br />to 1982 at Creston, Pender Harbour, and Sechelt, British Columbia. Length of prey items was
<br />estimated by comparison with the exposed culmen, Culmen lengths were estimated from mea-
<br />surements taken from about 90 live-captured (Keith Simpson, unpubl. data) and salvaged herons.
<br />
<br />RESULTS AND DISCUSSION
<br />
<br />Prey Stabbing in the Great Blue Heron was similar to Stabbing in the Goliath Heron (Ardea
<br />goliath) as described by Mock and Mock (1980).1t involved repeated strikes with closed or slightly
<br />open mandibles. Most fish (over 95%) were captured by the normal scissor-like method, rather than
<br />by skewering as in the Goliath Heron, and transported to a relatively dry area where the fish were
<br />not likely to escape (Recher and Recher 1968). Herons struck the fish in the dorso-cranial and
<br />ventro-abdominal regions up to 44 times. Between strikes, herons often picked up the fish, posi~
<br />tioned it between the mandibles as though {or swallowing, and then returned it to the ground for
<br />further strikes, The fish would occasionally become impaled on the ends of the mandibles and
<br />would be removed by axial twisting of the heron's head. Herons dipped their mandibles in water
<br />after swallowing. Prey Mandibulation involved extensive mastication of the fish between the her-
<br />on's mandibles for periods much longer than appeared necessary for simple positioning of the fish
<br />headfirst for swallowing,
<br />For fish less than 10 em long, herons used Prey Mandibulation; for fish greater than 10 cm long,
<br />herons used Prey Stabbing (Table 1).
<br />At Creston, four species of spiny fish comprised over 90% of the observed prey items (unpubl.
<br />data) but only black bullhead (Idalurus melas) were regularly Stabbed or Mandibulated (Table 1).
<br />Two large yellow perch (Perea flaveseens) were Stabbed, At Pender Harbour and Sechelt, Prey
<br />Stabbing and Mandibulation occurred with only two prey species, plainfin midshipman (Parichthys
<br />notatus) and Pacific staghorn sculpin (Leptocottus armatus) although several other spiny species
<br />including threespine stickleback (Gasterosteus aculeatus), tidepool sculpin (Oligocottus maculosus),
<br />shiner perch (Cymatogaster aggregata), snake prickleback (Lumpenus sagitta), and starry Hounder
<br />(Platichthys stellatus) were taken,
<br />Krebs (1974) speculated that Mandibulation of Pacific staghorn sculpins by Great Blue Herons
<br />probably served to snap off the sharp preopercular spines, based on observations of a captive heron,
<br />At Duck Lake near Creston on 23 June 1981, I recovered a 9 cm black bullhead dropped by a startled
<br />Great Blue Heron. The fish had been Mandibulated since mandibular marks were present on the
<br />head and body. Both pectoral spines and the dorsal spine were broken off near the base. That
<br />
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