LaDissertation.com - Dissertations, fiches de lectures, exemples du BAC
Recherche

Pélican

Commentaire d'oeuvre : Pélican. Recherche parmi 298 000+ dissertations

Par   •  4 Mars 2015  •  Commentaire d'oeuvre  •  827 Mots (4 Pages)  •  415 Vues

Page 1 sur 4

Pelicans are large water birds that live on seacoasts or inwarminland water habitats. There are seven generally recognized species. The coastal brown pelican lives from North Carolina to the Gulf of Mexico and the Caribbean, and from British Columbia to Chile, as well as the GalГЎpagos Islands. The American white pelican inhabits inland habitats in the western, central, and southeastern United States, Mexico, and Canada. The remaining species live in Australia, Europe, Asia, and Africa.

Physical Characteristics of Pelicans

Pelicans rank among the largest of living birds, ranging in size from four to six feet in length, and weighing from four to sixteen pounds. The brown pelican is smallest, and the large eastern great white pelican has a wingspan of up to ten feet. They have short legs and broad, fully webbed feet, which act as powerful paddles in the water, and cause them to walk with an awkward waddle on land. The pelican is famous for its huge, featherless throat pouch that is attached to the lower mandible. The pouch stretches as it fills with water when the bird is fishing, and can hold nearly three gallons. The pouch also functions as an evaporative cooling mechanism. The pelican opens it mouth and flutters its pouch, which keeps air flowing over the moist surface. Plumage color varies among species and according to age. Pelicans can be predominantly white, black, brown, or gray, with markings on the head, wingtips, underfeathers, or tail. The legs and feet are orange, brown, or black, and the bill and pouch are reddish, orange, or black. During the breeding season, these body parts change color, and many pelicans develop a yellow patch on the chest, a distinctive crest, and a bright ring around the eyes. The American white pelican also grows a noticeable horny knob on its beak.

Feeding and Other Behaviors

Pelicans feed on many species of saltwater and freshwater fish, fromtiny anchovies to fish weighing over a pound. Small crayfish, salamanders, frogs, and snakes are also consumed. The pelican thrusts its head and neck underwater and uses its pouch as a dip net to scoop up its prey. It drains out the water, then tilts its head back and swallows the fish whole. Many pelicans are social fishers, swimming in a circle to close in on the school, then all thrusting and dipping at once. Brown pelicans are solitary feeders, utilizing a spectacular plunge dive from about twenty feet above the water, with neck outstretched and bill pointed down. They hit the water hard, stunning the fish and trapping them in the pouch. Air sacs beneath the pelican's skin cushion its dive and help it to surface quickly. Pelicans are graceful fliers. They take off against the wind, beating their wings and pumping their feet simultaneously, hopping until they are airborne. They fly at a relatively slow speed, with their necks retracted and their heavy bills tucked in and resting on the breast, and often glide on thermals to conserve energy. Pelicans regularly fly in flocks in aV-formation, flapping their wings in unison. They often travel a great distance in search of food. Pelicans sleep standing or sitting on their bellies, with the head twisted back and the beak tucked into its feathers. Self-care activities include muscle exercises such as body shaking, wing flapping, tail wagging, leg stretching, bill throwing, and yawning. Pelicans groom

...

Télécharger au format  txt (5 Kb)   pdf (73.1 Kb)   docx (9.9 Kb)  
Voir 3 pages de plus »
Uniquement disponible sur LaDissertation.com