Great Blue Heron Ardea herodias Linnaeus       Field Guide IDs: NG-62; G-94; P~l00; PW-pl 4; All-pl 14; AW-pl 15; AM (1)-108 Nest Location Nest Type Eggs & Mating System Dev. & Parental Care Primary & 2ndary Diet.. Foraging Strategy MF I: 28 DAYS SEMIALTRICIAL 1 30 feet - 70 feet (10 feet -130 feet) MF 3-5 (1-7) MONOG F: 56-60 DAYS MF AQUATIC INVERTS SM VERTS BREEDING: Freshwater and brackish marshes, swamps, lakes, rivers, mangroves. 1 brood. DISPLAYS: Male at nest: neck stretch and fluff, circle flight, twig shake. Pair: crest raising, bill clappering. Displays more varied than those of egrets, but used less often and continue after pair-bond formation. NEST: Also occ in shrub, rarely on ground, rock ledge, coastal cliff. Large, flat, well made of interwoven sticks. Lined with twigs and leaves; repaired nests often lined with green needles. EGGS: Light bluish-green. 2.5" (64 mm). DIET: Mostly fish, but opportunistic, including human food scraps, nestlings, small mammals. Young fed fish. CONSERVATION: Winters s to n S.A. Blue List 1980-81, Special Concern 1982, Local Concern 1986; numbers increasing but much Atlantic coast habitat gone. NOTES: Nests in colonies, variable in size, occ solitary; in mixed colonies, Great Blue nests higher. Average clutch size increases with latitude to 5 in s Canada. As in most herons, foraging success improves with age: adults 2x as successful as young, which expend far more energy in foraging. White morphs ("Great White Heron") found only in marine habitats. STANFORD. NOTES: Uncommon visitor throughout the year. Occasionally forages at Lagunita, and for voles and pocket gophers in grassy areas throughout campus &endash; including the median along Campus Drive. ESSAYS: Piracy; Variation in Clutch Sizes; Blue List; Coloniality REFERENCES: Gibbs et al., 1987; Hancock and Kushlan, 1984; Pratt and Winkler, 1985.