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320 Hand-Rearing Birds

should be delayed or skipped until the crop clears. Chicks that are overfed or are slow to process
may develop sour crop and subsequent crop stasis, requiring intervention.
Once chicks are out of the brooder and housed in a tub, food is presented in a small, shallow
ceramic crock. Water is offered in a deeper crock with supervision initially. Plastic crocks have also
been used but are more lightweight and easily spilled by the chick. Beginning at about 5 weeks,
chicks are offered larger whole prey items, such as rats and rabbits, which provides exercise and
develops skills for feeding on carcasses. The size of these items is not crucial as lot of waste is
expected at first. When chicks have moved and adjusted to an outdoor nest box chamber, food and
water are delivered in larger crocks placed in a shallow tray, such as a small cat litter box. The tray
slides into a custom-made, fixed plywood box with a sliding lid. This allows food and water to be
changed from outside the enclosure without human contact. This system also minimizes the
chicks’ ability to remove the crocks to out-of-reach areas of the chamber.
After fledging, juveniles and adults are usually fed only in the holding enclosure, which is about
6 × 12 × 8 ft. (2 × 4 × 2.5 m) high and attached to the main flight enclosure. This conditions birds to
routinely enter this enclosure, the door of which can be closed from the outside, allowing staff to
capture birds easily for physical exams and moves. Food is delivered by way of a chute, made
from a section of 8 in. (20 cm) diameter PVC pipe, painted black and mounted through the fence
on a downward angle at a height of 6 ft. (2 m). The tube is covered with a PVC cap when not in use.
The holding area and adjacent enclosure walls are covered with solid material, such as corrugated
metal sheets, to provide a sight barrier. This virtually eliminates the birds’ associating humans with
food, as long as staff members are especially quiet and stay out of view when feeding.

­ Expected­Weight­Gain

Weigh chicks daily before the first morning feeding to provide the most consistent basis for com-
parison. This is easily done while chicks are still housed in brooders or in open “tubs” indoors.
Chicks usually do not gain weight the first day and in fact lose 1% of their hatch weight on average.
Initial weight gain is slow, from 3 to 5% daily for days 2–5, but jumps dramatically to an average of
12% ±5% for days 6–18. From day 19–35, weight gain averages 7% daily but varies from 2 to 16%
each day (Figure 19.2).
Once they have been moved to outdoor rearing chambers or nest boxes, weighing is more diffi-
cult as chicks are no longer handled directly on a daily basis. Weights may be taken opportunisti-
cally during this period, such as when chicks are vaccinated. Once they are old enough to jump up
on a low perch, 12–15 in. (30–40 cm) high, a sturdy spring scale (Pelouze model 10B60 heavy-duty
receiving scale, 27 kg/60 lb capacity), on which a protective plywood box housing is attached to
replace the weighing platform, may be mounted inside the rearing chamber. Placed where it is
likely to be a favored perch and facing the camera or observation window, this scale can provide
weights on a fairly consistent basis without the need to handle the chick. Scales can also be placed
in outdoor flight enclosures, mounted high on a sturdy post to serve as a preferred perch, to provide
weight information on fledged juveniles and adults. Because the birds tend to bounce heavily on
the scale, the plywood box housing should be mounted to the scale platform brackets using nuts
and bolts designed for aircraft. Hang gliding shops and light aircraft mechanics are good places to
find these. Similarly, the lightweight metal ferrule that secures the clear cover over the face of the
scale must be secured with screws to prevent the birds from systematically tearing it off and
destroying the face of the scale. Electronic scales have been tried with condors but have not proven
to be practical as both the birds and the environment are too hard on the scales.