Pellet (ornithology)

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Pellets from a long-eared owl. Shituan.jpg
Pellets from a long-eared owl.
The alimentary canal of a bird. PigeonAnatomy.png
The alimentary canal of a bird.
Long-eared owl pellets and rodent bones obtained from dissected pellets (1 bar = 1 cm). Pelotes rejection Asio Otus.jpg
Long-eared owl pellets and rodent bones obtained from dissected pellets (1 bar = 1 cm).

A pellet, in ornithology, is the mass of undigested parts of a bird's food that some bird species occasionally regurgitate. The contents of a bird's pellet depend on its diet, but can include the exoskeletons of insects, indigestible plant matter, bones, fur, feathers, bills, claws, and teeth. In falconry, the pellet is called a casting.

Contents

The passing of pellets allows a bird to remove indigestible material from its proventriculus, or glandular stomach. In birds of prey, the regurgitation of pellets serves the bird's health in another way, by "scouring" parts of the digestive tract, including the gullet. Pellets are formed within six to ten hours of a meal in the bird's gizzard (muscular stomach).

Ornithologists may collect one species' pellets over time to analyze the seasonal variation in its eating habits. One advantage of collecting pellets is that it allows for the determination of diet without the killing and dissection of the bird. Pellets are found in different locations, depending on the species. In general, these are roosting and nesting sites: for most hawks and owls, under coniferous trees; for barn owls, at the bases of cliffs or in barns and silos; for yet other species of owls, at their burrows or in marsh and field grasses. [1]

Pellet of a common kingfisher Kingfisher pellet - 2020-02-02 - Andy Mabbett - 02 (cropped).jpg
Pellet of a common kingfisher

Hawk and owl pellets are grey or brown, and range in shape from spherical to oblong or plug-shaped. In large birds, they are one to two inches long, and in songbirds, about half an inch. Many other species produce pellets, including grebes, herons, cormorants, gulls, terns, kingfishers, crows, jays, dippers, shrikes, swallows, and most shorebirds.

Ornithologists examining pellets have discovered unusual items in them—even bird bands that were once attached to a smaller species that was consumed by the predator bird. In the United States, screech owl pellets have contained bands from a tufted titmouse, black-capped chickadee, and American goldfinch. In 1966, a golden eagle pellet in Oregon was found to contain a band placed on an American wigeon four months earlier, and 1,600 km (990 mi) away in southern California. [1]

The hair, bones and other body parts (such as limbs, skin fragments, and even faeces) of rodents found in owl pellets may carry viable rodent viruses and bacteria. for this reason, they are sometimes sterilized before study. Smith et al. described two pellet-borne outbreaks of Salmonella typhimurium in schools where unsterile pellets were dissected. [2] Rodents tend to avoid owl pellets, apparently due to their infective potential. [3]

In falconry

In falconry, casting involves giving a hawk roughage, which is regurgitated later to purge and cleanse its crop. Hawks in the wild will produce castings of their own accord, in the form of small pellets of fur, feathers, and other indigestible material, regurgitated hours after it has eaten. Of the roughage used for falcons in captivity, there are two kinds: plumage, and cotton; the latter of which is generally in pellets about the size of hazelnuts, made of soft fine cotton, and conveyed into the hawk's gorge after supper. In the morning, the hawk will have cast them out, at which time they should be examined for color and condition to determine the state of the hawk's body. If they are cast out round, white, without stench, nor very moist, then the hawk is healthy; if otherwise, particularly black, green, slimy, or the like, the hawk is ill. [4]

The casting of plumage is examined in the same manner. The yellow down feathers of day-old rooster chicks, which are a common diet among hawks in captivity, can be enough to induce casting. However, rabbit fur and feathers from game birds are better suited for this purpose. [5]

Casting will occur at the same time daily, provided that hawks are flown at the same time daily. Hawks in captivity are usually weighed immediately before being flown. If they were fed roughage the previous day, they should cast it out before being weighed, to avoid an inaccurate measurement. [5]

Casting is a necessary part of a hawk's survival. Not only does it clear out the crop, but the roughage that is regurgitated cleans bacteria from the walls of the crop. If hawks in captivity are not provided with this necessary roughage, and instead are simply fed meat, they will become seriously ill and unreleasable into the wild. [6]

Related Research Articles

Mouse Small long-tailed rodent

A mouse is a small mammal. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse. Mice are also popular as pets. In some places, certain kinds of field mice are locally common. They are known to invade homes for food and shelter.

Owl Birds from the order Strigiforme

Owls are birds from the order Strigiformes, which includes over 200 species of mostly solitary and nocturnal birds of prey typified by an upright stance, a large, broad head, binocular vision, binaural hearing, sharp talons, and feathers adapted for silent flight. Exceptions include the diurnal northern hawk-owl and the gregarious burrowing owl.

Barn owl Common cosmopolitan owl species

The barn owl is the most widely distributed species of owl in the world and one of the most widespread of all species of birds, being found almost everywhere in the world except for the polar and desert regions, Asia north of the Himalayas, most of Indonesia, and some Pacific Islands. It is also known as the common barn owl, to distinguish it from the other species in its family, Tytonidae, which forms one of the two main lineages of living owls, the other being the typical owls (Strigidae).

Rough-legged buzzard Species of bird

The rough-legged buzzard or rough-legged hawk is a medium-large bird of prey. It is found in Arctic and Subarctic regions of North America, Europe, and Russia during the breeding season and migrates south for the winter. It was traditionally also known as the rough-legged falcon in such works as John James Audubon's The Birds of America.

Short-eared owl Species of owl

The short-eared owl is a widespread grassland species in the family Strigidae. Owls belonging to genus Asio are known as the eared owls, as they have tufts of feathers resembling mammalian ears. These "ear" tufts may or may not be visible. The short-eared owl will display its tufts when in a defensive pose, although its very short tufts are usually not visible. The short-eared owl is found in open country and grasslands.

Northern hawk-owl Species of owl

The northern hawk-owl or northern hawk owl is a medium-sized true owl of the northern latitudes. It is non-migratory and usually stays within its breeding range, though it sometimes irrupts southward. It is one of the few owls that is neither nocturnal nor crepuscular, being active only during the day. This is the only living species in the genus Surnia of the family Strigidae, the "typical" owls. The species is sometimes called simply the hawk owl; however, many species of owls in the genus Ninox are also called "hawk owls".

Great horned owl Species of owl

The great horned owl, also known as the tiger owl, or the hoot owl, is a large owl native to the Americas. It is an extremely adaptable bird with a vast range and is the most widely distributed true owl in the Americas. Its primary diet is rabbits and hares, rats and mice, and voles, although it freely hunts any animal it can overtake, including rodents and other small mammals, larger mid-sized mammals, birds, reptiles, amphibians, and invertebrates. In ornithological study, the great horned owl is often compared to the Eurasian eagle-owl, a closely related species, which despite the latter's notably larger size, occupies the same ecological niche in Eurasia, and the red-tailed hawk, with which it often shares similar habitat, prey, and nesting habits by day, thus is something of a diurnal ecological equivalent. The great horned owl is one of the earliest nesting birds in North America, often laying eggs weeks or even months before other raptorial birds.

Eastern screech owl Species of owl

The eastern screech owl or eastern screech-owl, is a small owl that is relatively common in Eastern North America, from Mexico to Canada. This species is native to most wooded environments of its distribution, and more so than any other owl in its range, has adapted well to manmade development, although it frequently avoids detection due to its strictly nocturnal habits.

Eclectus parrot Species of bird

The eclectus parrot is a parrot native to the Solomon Islands, Sumba, New Guinea and nearby islands, northeastern Australia, and the Maluku Islands (Moluccas). It is unusual in the parrot family for its extreme sexual dimorphism of the colours of the plumage; the male having a mostly bright emerald green plumage and the female a mostly bright red and purple/blue plumage. Joseph Forshaw, in his book Parrots of the World, noted that the first European ornithologists to see eclectus parrots thought they were of two distinct species. Large populations of this parrot remain, and they are sometimes considered pests for eating fruit off trees. Some populations restricted to relatively small islands are comparably rare. Their bright feathers are also used by native tribespeople in New Guinea as decorations.

Training raptors is a complex undertaking. Books containing advice by experienced falconers are still rudimentary at best. Many important details vary between individual raptors, species of raptors and between places and times. The keeping and training of any raptor is strictly and tightly regulated by U.S. state and federal laws. Anyone in the USA who is interested in flying raptors must seek out a state and federally licensed falconer to sponsor them through an apprenticeship period lasting two years at a minimum, and often considerably longer.

Indian eagle-owl Species of owl

The Indian eagle-owl, also called the rock eagle-owl or Bengal eagle-owl, is a large horned owl species native to hilly and rocky scrub forests in the Indian Subcontinent. It is splashed with brown and grey, and has a white throat patch with black small stripes. It was earlier treated as a subspecies of the Eurasian eagle-owl. It is usually seen in pairs. It has a deep resonant booming call that may be heard at dawn and dusk.

Uropygial gland

The uropygial gland, informally known as the preen gland or the oil gland, is a bilobed sebaceous gland possessed by the majority of birds used to distribute the gland's oil through the plumage by means of preening. It is located dorsally at the base of the tail and is greatly variable in both shape and size. In some species, the opening of the gland has a small tuft of feathers to provide a wick for the preen oil. It is a holocrine gland enclosed in a connective tissue capsule made up of glandular acini that deposit their oil secretion into a common collector tube ending in a variable number of pores (openings), most typically two. Each lobe has a central cavity that collects the secretion from tubules arranged radially around the cavity. The gland secretion is conveyed to the surface via ducts that, in most species, open at the top of a papilla.

Ashy-faced owl Species of owl endemic to Hispaniola in the Caribbean

The ashy-faced owl is a species of owl in the family Tytonidae. It is endemic to the Caribbean island of Hispaniola. Its natural habitats are subtropical or tropical dry shrubland, subtropical or tropical high-altitude shrubland, and heavily degraded former forest.

Plucking post

A plucking post is a raised structure such as a tree stump which is used regularly by a bird of prey to dismember its prey, removing feathers and various other inedible parts before eating it.

Outline of birds Overview of and topical guide to birds

The following outline is provided as an overview of and topical guide to birds:

Andaman masked owl Species of owl

The Andaman masked owl is a barn owl endemic to the southern Andaman Islands, an archipelago between India and Myanmar, in the Bay of Bengal. Regarded by some authors as a subspecies of the common barn owl, it is recognized by others as a species in its own right.

Mountain pygmy owl Species of owl

The mountain pygmy owl is a small species of owl from the family Strigidae. They reside throughout southern Arizona, New Mexico and Mexico.

Eastern barn owl Species of owl

The eastern barn owl is usually considered a subspecies group and together with the American barn owl group, the western barn owl group, and sometimes the Andaman masked owl make up the barn owl. The cosmopolitan barn owl is recognized by most taxonomic authorities. A few separate them into distinct species, as is done here. The eastern barn owl is native to southeastern Asia and Australasia.

Western barn owl Species of owl

The western barn owl is usually considered a subspecies group and together with the American barn owl group, the eastern barn owl group, and sometimes the Andaman masked owl make up the barn owl. The cosmopolitan barn owl is recognized by most taxonomic authorities. A few separate them into distinct species, as is done here. The western barn owl is native to Eurasia and Africa.

American barn owl Species of owl

The American barn owl is usually considered a subspecies group and together with the western barn owl group, the eastern barn owl group, and sometimes the Andaman masked owl, make up the barn owl, cosmopolitan in range. The barn owl is recognized by most taxonomic authorities. A few separate them into distinct species, as is done here. The American barn owl is native to North and South America, and has been introduced to Hawaii.

References

  1. 1 2 Terres, John. K. The Audubon Society Encyclopedia of North American Birds, New York: Alfred A. Knopf, 1980. ISBN   0-394-46651-9
  2. Smith, KE; Anderson, F; Medus, C; Leano, F; Adams, J (2005). "Outbreaks of salmonellosis at elementary schools associated with dissection of owl pellets". Vector-Borne and Zoonotic Diseases. 5 (2): 133–136. doi:10.1089/vbz.2005.5.133. PMID   16011429.
  3. Sike T, Rózsa L 2006. Owl pellet avoidance in yellow-necked field mice Apodemus flavicollis and house mice Mus musculus. Acta Zoologica Academiae Scientiarum Hungaricae , 52, 77–80.
  4. PD-icon.svg This article incorporates text from a publication now in the public domain :  Chambers, Ephraim, ed. (1728). Cyclopædia, or an Universal Dictionary of Arts and Sciences (1st ed.). James and John Knapton, et al.{{cite encyclopedia}}: Missing or empty |title= (help)
  5. 1 2 Ford, Emma. Falconry: Art and Practice, Revised Edition. Octopus Publishing Group - Cassell Illustrated. 1998. ISBN   0-7137-2588-5. p 23.
  6. Elsberry, Wesley R. "Falconry Jargon". Austringer. URL accessed 2006-05-30.