Fledge

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Fledging stage of the northern mockingbird (Mimus polyglottos) Mimus polyglottos (Mockingbird Fledgling).jpg
Fledging stage of the northern mockingbird (Mimus polyglottos)

Fledging is the stage in a flying animal's life between hatching or birth and becoming capable of flight. This term is most frequently applied to birds, but is also used for bats. [1] [2] For altricial birds, those that spend more time in vulnerable condition in the nest, the nestling and fledging stage can be the same. For precocial birds, those that develop and leave the nest quickly, a short nestling stage precedes a longer fledging stage. [3]

A pair of welcome swallow chicks, Hirundo neoxena, taken the day after they fledged. Swallow chicks444.jpg
A pair of welcome swallow chicks, Hirundo neoxena, taken the day after they fledged.

All birds are considered to have fledged when the feathers and wing muscles are sufficiently developed for flight. A young bird that has recently fledged but is still dependent upon parental care and feeding is called a fledgling. People often want to help fledglings, as they appear vulnerable, but it is best to leave them alone. [4] The USA National Phenology Network defines the phenophase (or life cycle stage) of fledged young for birds as "One or more young are seen recently departed from the nest. This includes young incapable of sustained flight and young which are still dependent on adults."

In many species, parents continue to care for their fledged young, either by leading them to food sources, or feeding them. Birds are vulnerable after they have left the nest, but before they can fly, though once fledged their chances of survival increase dramatically. [5]

A pigeon fledgling on a tiled floor Pigeon fledgling.jpg
A pigeon fledgling on a tiled floor

One species, the ancient murrelet, fledges two days after hatching, running from its burrow to the ocean and its calling parents. Once it reaches the ocean, its parents care for it for several weeks. Other species, such as guillemots and terns, leave the nesting site while they are still unable to fly. The fledging behavior of the guillemot is spectacular; the adult leads the chick to the edge of the cliff, where the colony is located, and the chick will then launch itself off, attempting to fly as far as possible, before crash landing on the ocean. [6]

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<span class="mw-page-title-main">Breeding biology of the tawny owl</span>

Tawny owls are monogamous and territorial year around. Young birds select territories and look for mates in autumn and tend to be very vocal, especially males. Due to their highly territorial behaviour, young birds frequently struggle to establish a territory unless a nearby adult dies. Males routinely engage in territorial fights. Territories have been known to have been maintained by single tawnys for up to 10 years in Russia and 13 years in Berlin. Of 34 males in Wytham, only one male moved off of territory, due to being disturbed by humans. It appears to be largely up to the male to select territorial boundaries. Despite the aforementioned territorial behaviour, active nests of two separate pairs at as close as 100 m (330 ft), in the Tegel forest, have been reported. This species shows very little extrapair parentage. In Switzerland for example, a study of 137 nestings found that only one, or 0.7%, were from a different father than the mate, females cannot generally raise young without male contribution so the pair structure of these highly residential owls insures little instance of cuckoldry. Cases of bigamy were reported at Wytham in 6 of 34 males, in situations where apparently a neighboring male died and was suffixed subsequently, however, one or the other nesting attempts would completely fail each time. In Pavia, 3 of 22 territories included two mature females.

<span class="mw-page-title-main">Precociality and altriciality</span> States of newborn mobility and independence

In the biology of birds and mammals, altricial species are those in which the young are underdeveloped at the time of birth, but with the aid of their parents mature after birth. Precocial species are those in which the young are relatively mature and mobile from the moment of birth or hatching. Precocial species are normally nidifugous, meaning that they leave the nest shortly after birth or hatching. These categories form a continuum, without distinct gaps between them.

References

  1. Skutch, A.F. (1976). Parent Birds and Their Young . Austin: University of Texas Press. ISBN   9780292746343.
  2. Kunz, T. H.; Fenton, M. B. (2005). Bat Ecology. University of Chicago Press. pp. 216–217. ISBN   0226462072.
  3. Gill, Frank. Ornithology (3rd ed.). New York: W.H. Freeman and Company. p. 491.
  4. "What to do if you find a baby bird".
  5. Gill, Frank. Ornithology (3rd ed.). New York: W.H. Freeman and Company. p. 492.
  6. As shown in this National Geographic video.