Page 43 - Hand rearing birds second

Identification and Aging 25

Table 2.2 Stages of life and development of passerine birds.

Stage of Life Days Description

Hatchling 0 Skin is thin and transparent. Down may be sparse or thick in one area or all over,
Stage (hatch or there may be no down at all. Eyes are closed and bulbous. Unable to
day) thermoregulate; must be brooded by parent. Weak.
1 Pinfeathers may be becoming visible (pigmented) beneath skin in dorsal tracts.
Begs for food.
2 Most feather tracts, especially primaries, show through skin. First food calls.
3 Beak darkens and begins to take shape. Gape flanges thicken and become
brighter. Mouth interior color intensifies. Egg tooth may have disappeared.
Feather tracts continue to darken as pins grow. Down may thicken. Eyes are
partly open (slits). Most can raise head and gape. May use wings as props.
Nestling 4–5 Beginning of rapid growth stage and increase in weight. Pinfeathers develop
Stage along tracts. Ventral feather tracts are visible, but belly and chest area up to neck
are bare. Primaries pierce through skin. Eyes still opening. Begins to use legs.
Evacuates at edge or over nest rim. Voice is stronger.
5–6 Some temperature control. Beginnings of motor coordination.
7–8 Eyes are fully open (may be longer for cavity‐nesting species). Rapid growth of
motor coordination. Well covered with feathers. Primaries unsheathing. Down
feathers, if present, are still attached to feather tips. Flutters when begging.
Makes new calls for location and feeding. Freezes, cowers, crouches, and may
snap bill when alarmed. Responds to alarm call of parent.
9–10 Fully feathered; wing and tail feathers still growing. Temperature control
nearly established; siblings keep each other warm. Juvenile plumage covers
entire skin surface. Preens, scratches head, moves about, exercises wings,
stays awake for longer periods, responds to parent’s alarm calls, is alert to
sights and sounds outside nest, may peck at objects on or near nest rim. Fear
response very strong, if nest discovered or disturbed, may jump before it
would normally fledge.
12–13 May still have a few downy feathers protruding from head. Pecks at objects
outside of nest. May be antagonistic toward siblings. Can perch, walk, and
hop. May perch on edge of nest or may venture out onto a branch and
flutter wings.
14–15 Leaves nest. Exceptions: cavity‐nesters and long‐winged species take about
20 days. Longer for some cavity nesting species. To 44 days for large corvids.
Fledgling 9–22 70–80% of adult weight (or more depending on species). Breast feathers have
Stage grown in to cover ventral body. Tail is about half grown. Wings are not as
long as those of adult. Can perch, walk, hop, or run well, but flight
capability varies. In general, some species do not fly well at first; not capable
of sustained flight for a few weeks. Cavity nesters fly better right out of nest
than open‐cup nesters. At first, fledgling remains mostly immobile and
silent except for food calls and stays apart from nest mates. Sleeps in adult
position with head under wing. Begins wiping beak, pecking at objects, and
picking up food off the ground or catching insects in the air (swallows,
flycatchers), working at grass heads (finches), or scratching at ground
(sparrows). Pursues parent(s) for food, begging in horizontal rather than
vertical position. Bathes, suns, and preens.