Black-Crowned Night-Heron (Nycticorax) Potential Occurrence: Rookeries Unlikely to Occur




Дата канвертавання24.04.2016
Памер16.08 Kb.
Aves (Birds): Ciconiiformes, Ardeidae

Black-Crowned Night-Heron (Nycticorax nycticorax)

Potential Occurrence: Rookeries Unlikely to Occur



Status: (Rookery Site)

Federal: None

State: None

Other: G4 S2S4 USFWS:BCC



S
Photo: Rick & Nora Bowers
pecies Description:

Adult Black-Crowned Night-Herons have pale gray bellies and wings and black backs. Their faces are white with a black cap, topped by a white plume. They have black bills and red eyes. Juveniles are mottled in gray, brown, and white coloring and have streaked breasts. One-year-old birds have an intermediate plumage somewhat between that of juveniles and adults. Black-Crowned Night-Herons have short necks that are often pulled in, giving the birds a somewhat thick-set appearance for a heron. (From Birdweb 2008)



Distribution:

The Black-Crowned Night-Heron is a fairly common, yearlong resident in lowlands and foothills throughout most of California, including the Salton Sea and Colorado River areas, and very common locally in large nesting colonies. Feeds along the margins of lacustrine, large riverine, and fresh and saline emergent habitats and, rarely, on kelp beds in marine subtidal habitats. Nests and roosts in dense-foliaged trees and dense emergent wetlands. Common nesting species on northeastern plateau from April to August. Uncommon in northwestern, and rare in northeastern, California in midwinter. Uncommon transient and rare in winter in southern deserts, and rare on Channel Islands. Seldom seen in mountains, but formerly nested at Big Bear Lake in San Bernardino Mts. (Cogswell 1977, McCaskie et al. 1979, Garrett and Dunn 1981). (From Granholm 1999)



Life History & Threats:

Black-Crowned Night-Herons are gregarious at all times of the year, and are often seen in very large groups. As their name implies, they are mostly nocturnal, roosting during the day in trees or marshes, and foraging at night, especially at dusk and dawn. They have also been seen feeding during the day, a practice most common during the demanding nesting season. When foraging, they usually stand still or walk slowly at the edge of shallow water, waiting for their prey. They will also perch above the water to fish. Birds return year after year to traditional winter roost sites. (From Birdweb 2008)

Feeds mostly nocturnally and crepuscularly. Highly variable diet consists of fishes, crustaceans, aquatic insects and other invertebrates, amphibians, reptiles, small mammals, and rarely young birds (Palmer 1962, Wolford and Boag 1971b). Collins (1970) and Hunter and Morris (1976) reported feeding on young terns. Usually hunts in shallow water, waiting motionlessly or, less commonly, stalking prey slowly (Kushlan 1976a). Sometimes vibrates bill to lure or flush prey, and may alight briefly on deep water to make a strike. (From Granholm 1999)

Breeds mainly February to July, but April to August in northeastern California (Cogswell 1977). Monogamous, colonial nester. Clutch size is 3-4, sometimes 5. Mean clutch size for 684 nests in a South San Francisco Bay colony (Bair Island) in May 1971, was 2.9 eggs (Gill 1977). Incubation reportedly 24-26 days. Semi-altricial, downy young are tended by both parents. They fly first at 6 wk, but are not independent until sometime later. A few breed at 1 yr, but most not until 2-3 yr (Palmer 1962, Harrison 1978). (From Granholm 1999)

Local migrator, dispersing widely from breeding colonies after nesting (Gill and Mewaldt 1979). Much of the breeding population from northwestern and northeastern California probably moves southward and is absent from those areas in midwinter. (From Granholm 1999)

Human disturbance of nesting colonies in Quebec (simulating a typical scientific nesting study) resulted in nest abandonment, predation of eggs, and reduced late-season nesting (Tremblay and Ellison 1979). Corvidae and other predators eat eggs. Numbers have been reduced from drainage of marshes and swamps, and cutting of trees, but this species is more adaptable and persistent than most other ardeids. (From Granholm 1999)



Habitat & Habitat Associations:

General:

Black-Crowned Night-Herons inhabit a variety of fresh and saltwater wetlands. In Washington, they breed primarily in freshwater areas. In spring and fall, they can be found in wetlands flanking large river basins. Winter habitat is varied, but these herons frequent forested swamps. (From Birdweb 2008)



Roosting Habitat:

Roosts among dense foliage of trees, not always near water, and in dense, fresh or brackish emergent wetlands (Grinnell and Miller 1944). Often rests on piers and pilings…(From Granholm 1999)



Nesting Habitat:

Nests in dense-foliaged trees, dense, fresh or brackish emergent wetlands, or dense shrubbery or vine tangles, usually near aquatic or emergent feeding areas. Nests are built of twigs and/or marsh plants. (From Granholm 1999)

In the San Francisco Bay Area, 11 Black-crowned Heron rookery sites were located in open shrub/grassland, wetlands, suburban areas, and islands. Birds nested in Eucalyptus (Eucalyptus sp.), Buckeye (Aesculus californica), Coast Live Oak (Quercus agrifolia), Monterey Pine (Pinus radiata), and reeds (Scirpus sp.) and most were within 0.5 km of wetland habitat (Kelly et al. 1993).

Conceptual Basis for GIS Model Development: To identify potential habitat for the Black-Crowned Night-Heron in the Study Area, we mapped:


  • Foraging Habitat: perennial and intermittent watercourses and ponds.

  • Nesting Habitat: woodland and forest vegetation types (i.e., coniferous, broadleaf upland, cismontane woodland, and riparian vegetation) within 0.5 km of foraging habitat

Potential Occurrence in the Galbreath Wildlands Preserve: Protection status for this species applies to nesting individuals.

Habitat: Rookery habitat for Black-Crowned Night-Herons is poor to moderate in the Preserve (Figure 79). Open forests are relatively abundant within 0.5 km of the mainstem of Rancheria Creek. However, foraging habitat needed to raise young is poor during most of the breeding season (February to July). Surface water in the mainstem draws down early in the year; the Creek is characterized by erosional surfaces and lacks substantial amounts emergent vegetation preferred by this species. Riparian forests on the Preserve are also poorly developed and patchy in distribution.

Nearest Occurrence:

Documented Occurrences in the Galbreath Wildlands Preserve: This species has not been observed on the Preserve. To our knowledge no surveys have been conducted.

Nearest Occurrence to the Galbreath Wildlands Preserve: This species has not been reported to occur in USGS quads adjacent to the Preserve.

Summary: We anticipate that rookery sites of this species is “Unlikely to Occur” on the Preserve because foraging habitats needed by breeding colonies are poor for most of the breeding season.

References

Birdweb. 2008. Black-crowned Night-Heron. Seattle Audubon Society.



. 2010 July 22.
Bowers R, and N Bowers. The Owl Pages-Flammulated Owl Photo. image.php?image=species-Otus-flammeolus-6>. 2010 July 21.


Hays D W, and E A Rodrick. 2003. Management Recommentations for Washington’s

Flammulated Owl. Washington Department of Fish and Wildlife.



. 2010 July 21.
Granholm S. 1999. Black-Crowned Night Heron. California Wildlife Habitat Relationships

System. . 2010 July 22.


Kelly, J P, H M Pratt, and P L Greene 1993. The distribution, reproductive success, and habitat characteristics of colonies in the San Francisco Bay Area. Colonial Waterbirds 16:18-27
Yasuda S. 2001 August 28. California Partners in Flight Coniferous Bird Conservation Plan for

the Flammulated Owl. USDA Forest Service.

species/conifer/flowacct.html>. 2010 July 21.
Species Account Description: Emily Harvey



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