feeders and will often stand in water up to their bellies 

 when feeding. As with other waders, they are opportu- 

 nistic feeders. 



Louisiana herons construct nests in woody vegeta- 

 tion, but will also nest on elevated herbaceous vegeta- 

 tion or on the ground (Palmer 1962). They frequently 

 nest in mixed-species colonies where the plant canopy 

 is open. They often nest on the periphery of colonies 

 at lower levels in the vegetative cover. McCrimmon 

 (1978) studied nesting requirements and found that 

 those of the Louisiana herons were distinct from other 

 species except for the little blue heron. This may be 

 due to inability to compete with other species for more 

 central sites (Maxwell and Kale 1977). About 7% of 

 the nesting population in Louisiana is located in the 

 Chenier Plain (Portnoy 1977). Renesting occurs and 

 incubation begins after the first (Rodgers 1978) or 

 second (Maxwell and Kale 1977) egg is laid. 



Chemical contamination in food chains and the 

 destruction of nesting and feeding habitat by human 

 activities is threatening this species. 



5.3.11 BLACK CROWNED NIGHT HERON {Nycti- 

 corax nycticorax) 



In the Chenier Plain, most night herons are found 

 in salt marshes; however. Palmer (1962) reported that 

 the species may be found in almost any wading-bird 

 habitat. 



This species is abundant in the Chenier Plain from 

 early March to late September (Lowery 1974a) and less 

 abundant in winter. It is not known if individuals pre- 

 sent in winter are permanent residents or migrants 

 from more northern breeding areas. Post-nesting dis- 

 persal is common (Byrd 1978). The black-crowned 

 night heron feeds primarily at night and roosts during 

 the day. Its nocturnal habits help to reduce competi- 

 tion with other species. Daily movements consist pri- 

 marily of flights of individuals or small flocks between 

 feeding areas and resting areas. In North Carolina, these 

 flights probably average 15 km (9 mi) (Parnell and 

 Soots 1978). 



The black-crowned night heron's diet includes 

 worms, insects, crustaceans, mollusks, fish, amphibians, 

 and reptiles. This species occasionally consumes the 

 eggs and young of other nesting herons (Palmer 1962). 



Black-crowned niglit herons nest in mixed colonies 

 with other herons, but usually closer to the ground and 

 in heavier vegetation (Burger 1978). Approximately 8% 

 of the Louisiana breeding adults reported by Portnoy 

 (1977) occurred in the Chenier Plain. 



Loss of breeding habitat and the presence of chem- 

 ical contaminants in ecosystems has had a detrimental 

 effect on black-crowned night heron numbers 

 (Ohlendorf ct al. 1978). In the Great Lakes area, this 

 species may have been adversely affected by high PCB 

 levels (Gilbertson et al. 1976). 



Common crows and fish crows actively preyed 

 upon black-crowned night heron nests in several New 



Jersey heronries (Burger and Hahn 1977). The crows 

 could not successfully rob the actively defended nests 

 of other species in these mixed-species colonies. Thus, 

 it is an advantage for night herons to nest in mixed- 

 species colonies (Burger and Hahn 1977). 



5.3.12 YELLOW-CROWNED NIGHT HERON 



(Nyctanassa violacea) 



Although this species primarily inhabits fresh 

 marshes and swamp forest habitats in the Chenier 

 Plain, it also occurs in salt or brackish marshes. Food 

 consists largely of crustaceans; in the Chenier Plain 

 crayfish are the major food item. 



Although listed as a permanent resident by Low- 

 ery (1974a), this species rarely winters in the Chenier 

 Plain. Migrants begin to leave in September and begin 

 to return in March. Daily movements consist of flights 

 from roosting and nesting areas to feeding areas. This 

 species is less nocturnal than the black-crowned night 

 heron. 



Yellow-crowned night herons nest high in trees in 

 loosely formed colonies. They rarely colonize with 

 other species. In the Chenier Plain, clutch size is pro- 

 bably 3 to 5 eggs, and both sexes incubate. The incu- 

 bation period is unknown, but young leave the nest 

 approximately 2 months after the eggs are laid (Palmer 

 1962). 



Draining of swamps has a detrimental effect on 

 this species. In Louisiana, the larger nestlings are eaten 

 by local residents. 



5.3.13 LEAST BITTERN (Ixobrychus exilis) 



The least bittern is primarily a summer resident in 

 the Chenier Plain. Occasionally, a few remain through 

 the winter. Highest densities occur in April through 

 September (Lowery 1974a). Because breeders maintain 

 territories that include both feeding and nesting areas, 

 daily movements are somewhat limited. Territories often 

 are about 0.8 ha (2.0 a) in size (Palmer 1962). 



Least bitterns are more common in fresh marshes 

 than in salt marshes. They generally occur in the densest 

 marsh vegetation (Palmer 1962) where they consume a 

 variety of foods. Of 93 stomachs analyzed by the U.S. 

 Biological Survey, 40% contained freshwater fishes; 

 10% contained crustaceans, mainly crayfish; and 33% 

 contained insects. 



Nests are usually located in dense stands of cattail, 

 bulrush, or similar vegetation. The least bittern nests 

 singly and has a clutch of 4 to 5 eggs. Incubation lasts 

 17 to 18 days and both sexes participate. 



Drainage of marshes and the use of pesticides have 

 adversely affected this species in some areas (Palmer 

 1962). 



5.3.14 AMERICAN BITTERN (Botaurus 

 lentiginosus) 



Although this species is listed as a year-round resi- 

 dent by Lowery (1974a), it is primarOy a migrant and 



234 



