Current Distribution Rangewide

Ranges from California, eastern Oregon, southern Idaho, Utah, Montana, southern North Dakota, northwestern Iowa, and southwestern Minnesota south into Mexico, coastal Texas, and southwestern Louisiana, southern Alabama, Florida [1;2]. Also found in South America in southwestern Peru, Bolivia, Paraguay, Uruguay, southern Brazil, northern and central Chile, and northern and central Argentina [3;4; both cited in 1;5, cited in 2] during the breeding season. In the non-breeding season, ranges from north to southern California, Baja California, southern Texas, and coastal Louisiana, south through lowlands to Guatemala and El Salvador, and generally in breeding range in South America [1;5, cited in 2].

Known Populations in San Diego County

Known to occur in the lower Santa Margarita and San Luis Rey River Valleys, northern San Diego County coastal lagoons, and up Escondido Creek and the San Dieguito River to the San Pasqual Valley during the breeding season. Winters primarily in the San Pasqual Valley and occassionally in Ramona and Dairy Mart Pond [6].

List Status

None.

Habitat Affinities

Inhabits primarily freshwater wetlands and marshes, especially those containing cattail (Typha spp.) and bulrush (Scirpus spp.)[6] , and flooded stands of saltcedar (Tamarix spp.) and Baltic rush (Juncus balticus) [7, cited in 1]. Also found in ponds, mudflats, and swamps outside of California [1]. In San Diego County, depends on dense freshwater marshes for nesting and forages in shallow water, wet grass, and irrigated or flooded pastures and croplands [6;8, cited in 9].

Taxonomy and Genetics

Sometimes considered conspecific with the Glossy ibis, P. falcinellus [2]. No genetic studies have investigated the genetic divergence of these two groups [10], though hybrids have been produced in captivity [1].

Seasonal Activity

Diurnal [2;9]. Several days before nesting, roosts near or within colony site surrounded by emergent vegetation such as cattails, bulrushes, and reeds or low shrubs over water [1;11, cited in 9]. Winters mainly in San Joaquin Valley and Imperial Valley, but recorded widely as transient [9]. Birds breeding in the Great Basin migrate to the Imperial Valley [12].

Life History/Reproduction

Gregarious [2]. Nest in large colonies that range in size from 30-50 nests in new colonies and up to more than 1500 in established colonies [13]. First breed around 2 years of age [13;14]. Average distance of 2 meters between nests [15] and typically defend one meter area around nest [16, cited in 10]. Nests made up of dead tules and cattails supported on leaves bent over to make a crude platform [6;9]. Lay eggs from the last week of March to mid-May [6]. Incubation begins soon after first egg is laid with average incubation period ranging from 20-22 days [2;17, cited in 10;18, cited in 9]. Clutch usually 3-4 eggs [2;18, cited in 9]. Young are born semi-altricial and fledge at 28 days [13]. Young are independent at 8 weeks of age [17, cited in 10]. Live to about 14 years of age in captivity and from 9 to 11 years of age in the wild [19].

Diet and Foraging

Diet consists mostly of insects and their larvae, crustaceans, earthworms, small fish, and amphibians [18, cited in 9;20]. May also consume crayfish, snails, spiders, and leeches. Locate prey using two different quatic methods: a ranging method while probing the water and a stationary method swinging its bill side-to-side. Observed to drink water [16, cited in 9].

Dispersal

Highly mobile [1]. Wander greatly depending on water conditions and the availbility of prey. Prebreeding wandering seems more prevalent than postbreeding [18]. Adults and subadults wander far from breeding areas during late summer [1]. Beginning by late July, post breeding dispersal or fall migration commences and is substantial by late August [6].

Threats

Threatened by development of the floodplains [6].

Literature Sources