Fledge is the stage in the life of a young bird when the feathers and wing muscles are developing for flight. It, also, describes the process of raising chicks to a fully grown state by the chick's parents. A young bird that has recently fledged but is still dependent upon parental care and feeding is called a fledgling that feels comfortable in its own fledgling bird house.

In ornithology, the meaning of fledgling can mean different things, depending on the particular species. Birds are sometimes considered fledged once they leave the nest even if they still cannot fly. However, usually a fledgling is considered a chick that is independent from an adult because, very often, adults will continue to feed the chick after it has left the nest and is able to fly.

The murrelet fledges two days after hatching, running from its burrow to the ocean and its calling parents. Once it reaches the ocean it is cared for several weeks by its parents. Other species, such as guillemots and cormorants leave the nesting site before they are, barely, able to fly. The behavior of the guillemot fledgling is interesting. The adult will lead the chick to a large drop like a cliff. The adult will, then, fly down and call to its young. The chick will launch itself off the cliff attempt to fly as far as possible, crash land on the ground below before continuing its run towards the ocean.

Baby birds often look different from the adults, if only in the body proportions. Some fledglings look so different from the adult that their species are difficult to identify. Baby birds typically have very brightly colored bill and throat linings. As a chick opens its mouth to vocalize or beg, the parent bird sees a flash of orange, red, or yellow--a "target zone" that shows where to stuff the next juicy grub or worm. In many altricial species, born helpless and naked when hatched as in the Eastern Tufted Titmouse, fledglings temporarily retain colored target zones that change to gray or white or even black as the youngster matures.

The bright color of a nestling's mouth lining typically extends to the edge of the bill and to the juncture of the upper and lower mandibles--an area known as the "gape." In young birds, the gape is very soft and noticeable but in a fledgling it begins to harden somewhat, become less prominent, and--like the bill itself--darken with age. In some bird species such as the Purple Finches, the adult retains a yellow gape, albeit smaller and less obvious.

In some bird species, young birds exhibit a remarkable change in bill color. In some birds such as the fledgling cardinal, the bill is very dark. It, eventually, becomes bright orange as the youngster begins to forage on seeds and berries containing carotene it lays down in the bill sheath. Strangely, adult cardinals quit processing yellow-orange pigment during the non-breeding season, so bill color in winter birds gradually fades until it resembles that of juveniles. The same phenomenon occurs in the American Goldfinch.

The titmouse, cardinal and young House Finch also illustrate another common characteristic of nestlings/recent fledglings, a sort of "natal plume", a few wispy feathers that sprout from head or nape. Such plumes, especially noticeable in older nestlings, look really out of place in a fledgling. These non-essential feathers, usually, break off or fall out within a week or so after a bird leaves its nest. Consequently, their presence is a fairly precise indicator of a youngster's age.

The House Finch demonstrates another common characteristic of fledglings. The body feathers are loosely structured and give the young bird a disheveled look. It's not that fledglings haven't yet learned how to preen but that their first feathers have poorly formed vanes and barbs and barbules. Thus, young birds, often, do not have the sleek and smooth appearance of the adult--a characteristic that may continue for several months or more until the fledgling gets its first full set of "adult" feathers.

Sometimes, those loosely-structured juvenile feathers have entirely different markings than the bird will have as an adult. In this situation, the crissum--the short, tan-colored plumage that overlaps the underside of the dark rusty tail feathers is not only poorly formed but uniformly light brown. When the fledgling molts these soft undertail feathers, usually by late in its first summer, the stronger adult feathers that replace them are whiter and bear prominent dark bars. These marks match the barring characteristic of plumage in most members of the wren family.

The ruby-throated hummingbird is another bird in which young males do NOT look like adult males. In this species, the young male lacks a full red gorget and, in fact, resembles his white-throated mother--even sporting the white-tipped outer tail feathers found in all females. Most, but not all young males of the year have at least a hint of dark green or black streaking on their throats, and some will acquire one or more red gorget feathers before departing for the tropics in autumn. With that in mind, except for early spring before the current year's youngsters fledge, one should NEVER assume a white-throated Ruby-throated Hummingbird is a female. In the Carolinas, after about mid-May the hummer very well could be a fledgling male. The fact that the young male ruby-throats look like females, probably, saves them from potential hazardous territorial encounters with adult males.

Another characteristic that differs significantly between fledglings and adults is eye coloring. Many fledglings have what we call "muddy" eyes in which irises are dull and not very sparkly. As the eye matures, the crystalline make-up of the iris changes, muddiness clears, and color generally deepens. In some cases, however, there is a drastic and quite noticeable change in eye color, as when the gray-eyed fledgling Brown Thrasher acquires brilliant yellow irises as an adult. Such drastic color change in thrashers and other species may take a couple of years. Older thrashers sometimes get a red outer ring around the iris.

Once you find your way around fledglings, you will enjoy watching how they mature into the adult species that you know and love. Enjoy your bird-watching.