around the periphery of the colony, while 

 little blue herons prefer more protected 

 locations (Jenni 1969). 



Egg destruction occurs as the result 

 of predators such as raccoons or crows 

 (Teal 1965). During the first few weeks 

 after hatching, chick mortality may be 

 high. Jenni (1969) suggested that snowy 

 egret chick loss was largely due to star- 

 vation. He found that mortality rates 

 were Zl% per nest of four, 23% per nest of 

 three, and 10% per nest of two. In a mixed 

 species heronry in Georgia, 10% of the 

 nestlings died of starvation (Teal 1965). 

 Nest success varies from species to spe- 

 cies. Teal (1965) found that only black- 

 crowned night herons fledged more than 50% 

 of the eggs laid. He attributed this to 

 pugnacious behavior of the chicks who 

 vigorously defend their nest. He suggested 

 that the smaller and less fierce species 

 (snowy egret and Louisiana heron) were the 

 least successful. 



After fledging, high mortality rates 

 may be sustained through the first year of 

 life. Kahl (1963) found that 76% of the 

 common egrets alive on July 1 died during 

 their first year, and mortality rates of 

 71% (Owen 1959) were reported for the 

 great blue heron. Most of the first year 

 mortality for both common egrets and great 

 blue herons occurs between July and Decem- 

 ber and may be due to the unfamiliarity of 

 inexperienced young of the year with 

 migratory territories (Kahl 1963). It 

 takes time for young birds to become pro- 

 ficient hunters. Although feeding behav- 

 iors appear to be innate components of a 

 heron's biology and similar techniques are 

 used by both adults and juveniles, success 

 rates are much higher for adult birds. 

 Recher and Recher (1969a) found that for 

 each minute spent foraging, adult little 

 blue herons obtained more prey by weight 

 than the juveniles. Similarly, adult great 

 blue herons were found to be successful in 

 62% of strikes while juveniles captured 

 prey in only 33% of their attempts (Quin- 

 ney and Smith 1980). 



While it appears that food is a lim- 

 iting resource particularly during the 

 breeding season. Teal (1965) concluded 

 that there is a surplus of food, but this 

 food is not sufficiently available to even 

 the adult birds since they are relatively 



inefficient predators. This is not sur- 

 prising since the primary prey are mobile 

 fish and large crustaceans, making food 

 finding and foraging techniques critical 

 factors in heron ecology. 



The role of colonies as information 

 centers has been studied extensively in 

 heron breeding colonies. Krebs (1974) 

 specifically addressed this problem in a 

 study of the great blue heron. To illus- 

 trate the advantage of gregariousness, he 

 showed that while the birds exploited a 

 patchy food supply, individuals were not 

 behaving independently, and birds that 

 foraged in groups had a higher rate of 

 food intake than those feeding solitarily. 

 Feeding areas were highly variable from 

 day to day and the colony tended to switch 

 in unison from one feeding site to anoth- 

 er. Departure from the breeding colonies 

 to foraging areas generally occurred in 

 groups and birds from neighboring nests 

 frequently fed in the same areas. Finally, 

 Krebs (1974), who put styrofoam models of 

 foraging herons in the field, found indi- 

 viduals flying overhead were attracted to 

 them, landed, and began foraging. 



During foraging, the herons may be 

 either solitary and defend feeding terri- 

 tories or gregarious and form small 

 flocks. Great blue herons have their 

 highest rate of feeding success at a flock 

 size of about twenty birds and Krebs 

 (1974) suggests that flocks may buffer the 

 risk of birds being unsuccessful in feed- 

 ing on the short term, which may be criti- 

 cal when rearing chicks. Even when great 

 blues feed alone, colonies may still play 

 a role as information centers in locating 

 the position of food resources relative to 

 the colony (Ward and Zahavi 1973). 



As a group, the herons use a diverse 

 array of foraging behaviors and within the 

 tidal flat environment, may segregate 

 themselves according to habitat prefer- 

 ences and morphology. As a result, the 

 overlap in prey items between species may 

 be reduced. In Florida, Meyerriecks 

 (1962) has seen as many as nine species of 

 herons feeding on the same shoal; he 

 claims that their ability to coexist while 

 using a common habitat results from their 

 use of different feeding methods. Kushlan 

 (1976) provides a good descriptive sum- 

 mary of heron feeding behaviors. The major 



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