A fecal sac (also spelled faecal sac) is a mucous membrane, generally white or clear with a dark end, [1] that surrounds the feces of some species of nestling birds. [2] It allows parent birds to more easily remove fecal material from the nest. The nestling usually produces a fecal sac within seconds of being fed; if not, a waiting adult may prod around the youngster's cloaca to stimulate excretion. [3] Young birds of some species adopt specific postures or engage in specific behaviors to signal that they are producing fecal sacs. [4] For example, nestling curve-billed thrashers raise their posteriors in the air, while young cactus wrens shake their bodies. [5] Other species deposit the sacs on the rim of the nest, where they are likely to be seen (and removed) by parent birds. [4]
Not all species generate fecal sacs. They are most prevalent in passerines and their near relatives, which have altricial young [6] that remain in the nest for longer periods. [3] In some species, the fecal sacs of small nestlings are eaten by their parents. In other species, and when nestlings are older, sacs are typically taken some distance from the nest and discarded. [7] Young birds generally stop producing fecal sacs shortly before they fledge. [8]
Removal of fecal material helps to improve nest sanitation, which in turn helps to increase the likelihood that nestlings will remain healthy. [9] It also helps to reduce the chance that predators will see it or smell it and thereby find the nest. [10] Experiments on starling nests suggest that bacteria in faeces produce volatile chemicals that may provide cues for predators and ectoparasites such as flies in the genus Carnus . [11] There is evidence that parent birds of some species gain a nutritional benefit from eating the fecal sacs; studies have shown that females – which tend to be more nutritionally stressed than their mates – are far more likely to consume sacs than are males. [12] Even brood parasites such as brown-headed cowbirds, which do not care for their own offspring, have been documented swallowing the fecal sacs of nestlings of their host species. [13]
Scientists can use fecal sacs to learn a number of things about individual birds. Examination of the contents of the sac can reveal details of the nestling's diet, [14] [15] and can indicate what contaminants the young bird has been exposed to. [16] The presence of an adult bird carrying a fecal sac is used in bird censuses as an indication of breeding. [17]
The American goldfinch is a small North American bird in the finch family. It is migratory, ranging from mid-Alberta to North Carolina during the breeding season, and from just south of the Canada–United States border to Mexico during the winter.
The American robin is a migratory bird of the true thrush genus and Turdidae, the wider thrush family. It is named after the European robin because of its reddish-orange breast, though the two species are not closely related, with the European robin belonging to the Old World flycatcher family. The American robin is widely distributed throughout North America, wintering from southern Canada to central Mexico and along the Pacific coast.
The cinereous vulture is a large raptor in the family Accipitridae and distributed through much of temperate Eurasia. It is also known as the black vulture, monk vulture and Eurasian black vulture. With a body length of 1.2 m, 3.1 m (10 ft) across the wings and a maximum weight of 14 kg (31 lb), it is the largest Old World vulture and largest member of the Accipitridae family.
The American white ibis is a species of bird in the ibis family, Threskiornithidae. It is found from Virginia via the Gulf Coast of the United States south through most of the coastal New World tropics. This particular ibis is a medium-sized bird with an overall white plumage, bright red-orange down-curved bill and long legs, and black wing tips that are usually only visible in flight. Males are larger and have longer bills than females. The breeding range runs along the Gulf and Atlantic Coast, and the coasts of Mexico and Central America. Outside the breeding period, the range extends further inland in North America and also includes the Caribbean. It is also found along the northwestern South American coastline in Colombia and Venezuela. Populations in central Venezuela overlap and interbreed with the scarlet ibis. The two have been classified by some authorities as a single species.
The northern cardinal, known colloquially as the redbird, common cardinal, red cardinal, or just cardinal, is a bird in the genus Cardinalis. It can be found in southeastern Canada, through the eastern United States from Maine to Minnesota to Texas, New Mexico, southern Arizona, southern California, and south through Mexico, Belize, and Guatemala. It is also an introduced species in a few locations such as Bermuda and Hawaii. Its habitat includes woodlands, gardens, shrublands, and wetlands.
The tree swallow is a migratory bird of the family Hirundinidae. Found in the Americas, the tree swallow was first described in 1807 by French ornithologist Louis Vieillot as Hirundo bicolor. It has since been moved to its current genus, Tachycineta, within which its phylogenetic placement is debated. The tree swallow has glossy blue-green upperparts, with the exception of the blackish wings and tail, and white underparts. The bill is black, the eyes dark brown, and the legs and feet pale brown. The female is generally duller than the male, and the first-year female has mostly brown upperparts, with some blue feathers. Juveniles have brown upperparts, and grey-brown-washed breasts. The tree swallow breeds in the US and Canada. It winters along southern US coasts south, along the Gulf Coast, to Panama and the northwestern coast of South America, and in the West Indies.
The house finch is a bird in the finch family Fringillidae. It is native to western North America and has been introduced to the eastern half of the continent and Hawaii. This species and the other two American rosefinches are placed in the genus Haemorhous.
The brown-headed cowbird is a small, obligate brood parasitic icterid native to temperate and subtropical North America. It is a permanent resident in the southern parts of its range; northern birds migrate to the southern United States and Mexico in winter, returning to their summer habitat around March or April.
The veery is a small North American thrush species, a member of a group of closely related and similar species in the genus Catharus, also including the gray-cheeked thrush, Bicknell's thrush, Swainson's thrush, and hermit thrush. Alternate names for this species include Wilson's thrush and tawny thrush. Up to six subspecies exist, which are grouped into the eastern veery, the western veery or willow thrush, and the Newfoundland veery.
The yellow warbler is a New World warbler species. Yellow warblers are the most widespread species in the diverse genus Setophaga, breeding in almost the whole of North America, the Caribbean, and down to northern South America.
The grasshopper sparrow is a small New World sparrow. It belongs to the genus Ammodramus, which contains three species that inhabit grasslands and prairies. Grasshopper sparrows are sometimes found in crop fields and they will readily colonize reclaimed grassland. In the core of their range, grasshopper sparrows are dependent upon large areas of grassland where they avoid trees and shrubs. They seek out heterogenous patches of prairie that contain clumps of dead grass or other vegetation where they conceal their nest, and also contain barer ground where they forage for insects, spiders, and seeds. Grasshopper sparrows are unusual among New World sparrows in that they sing two distinct song types, the prevalence of which varies with the nesting cycle. The primary male song, a high trill preceded by a stereotyped series of short chips, is reminiscent of the sounds of grasshoppers and is the origin of this species' name. Like some other birds of the central North American grasslands, this species also moves around a lot, not only via annual migrations, but individuals frequently disperse between breeding attempts or breeding seasons. Grasshopper sparrows are in steep decline across their range, even in the core of the breeding distribution in the tallgrass prairies of the central Great Plains. The Florida grasshopper sparrow is highly endangered.
Brood parasitism is a subclass of parasitism and phenomenon and behavioural pattern of certain animals, brood parasites, that rely on others to raise their young. The strategy appears among birds, insects and fish. The brood parasite manipulates a host, either of the same or of another species, to raise its young as if it were its own, usually using egg mimicry, with eggs that resemble the host's.
A bird nest is the spot in which a bird lays and incubates its eggs and raises its young. Although the term popularly refers to a specific structure made by the bird itself—such as the grassy cup nest of the American robin or Eurasian blackbird, or the elaborately woven hanging nest of the Montezuma oropendola or the village weaver—that is too restrictive a definition. For some species, a nest is simply a shallow depression made in sand; for others, it is the knot-hole left by a broken branch, a burrow dug into the ground, a chamber drilled into a tree, an enormous rotting pile of vegetation and earth, a shelf made of dried saliva or a mud dome with an entrance tunnel. The smallest bird nests are those of some hummingbirds, tiny cups which can be a mere 2 cm (0.8 in) across and 2–3 cm (0.8–1.2 in) high. At the other extreme, some nest mounds built by the dusky scrubfowl measure more than 11 m (36 ft) in diameter and stand nearly 5 m (16 ft) tall. The study of birds' nests is known as caliology.
The shiny cowbird is a passerine bird in the New World family Icteridae. It breeds in most of South America except for dense forests and areas of high altitude such as mountains. Since 1900 the shiny cowbird's range has shifted northward, and it was recorded in the Caribbean islands as well as the United States, where it is found breeding in southern Florida. It is a bird associated with open habitats, including disturbed land from agriculture and deforestation.
The vermilion flycatcher is a small passerine bird in the tyrant flycatcher family found throughout South America and southern North America. It is a striking exception among the generally drab Tyrannidae due to its vermilion-red coloration. The males have bright red crowns, chests, and underparts, with brownish wings and tails. Females lack the vivid red coloration and can be hard to identify—they may be confused for the Say's phoebe. The vermilion flycatcher's song is a pit pit pit pidddrrrreeedrr, which is variable and important in establishing a territory. Riparian habitats and semi-open environments are preferred. As aerial insectivores, they catch their prey while flying. Their several months-long molt begins in summer.
In zoology, a nectarivore is an animal which derives its energy and nutrient requirements from a diet consisting mainly or exclusively of the sugar-rich nectar produced by flowering plants.
The African pygmy falcon —or simply pygmy falcon—is a diminutive raptor native to eastern and southern Africa. It is the sole species in its monotypic genus, Polihierax. The pygmy falcon is the smallest bird of prey on the African continent, and among the smallest raptors on earth; only the Asian falconets are smaller, weighing roughly 30-40 grams less and measuring about 5 cm shorter from head-to-tail.
The red warbler is a small passerine bird of the New World warbler family Parulidae endemic to the highlands of Mexico, north of the Isthmus of Tehuantepec. It is closely related to, and forms a superspecies with, the pink-headed warbler of southern Mexico and Guatemala. There are three subspecies, found in disjunct populations, which differ in the color of their ear patch and in the brightness and tone of their body plumage. The adult is bright red, with a white or gray ear patch, depending on the subspecies; young birds are pinkish-brown, with a whitish ear patch and two pale wingbars.
The screaming cowbird is an obligate brood parasite belonging to the family Icteridae and is found in South America. It is also known commonly as the short billed cowbird.
The white-rumped swallow is a species of bird in the family Hirundinidae. First described and given its binomial name by French ornithologist Louis Pierre Vieillot in 1817, it was for many years considered a subspecies of the Chilean swallow. The species is monotypic with no known population variations. It has a white supraloral streak, or streak above its lores, which can be used to differentiate it from the Chilean swallow. The lores, ear coverts, tail, and wings are black, with white tips on the inner secondaries, tertials, and greater coverts of the wings. The rest of the upperparts are a glossy blue. Its underparts and underwing-coverts are white, in addition to the rump, as the name suggests. The sexes are similar, and the juvenile is duller and browner with a dusky breast.