Page 77 - Hand rearing birds second

60 Hand-Rearing Birds

Cracked, flawed, punctured, or dented eggs are often hatchable if carefully repaired. If not repaired,
they are vulnerable to infection and excessive weight loss. Even if there is a slight leakage of albumen
or blood, repairs can usually be made. Eggs leaking yolk material, however, are not repairable.
Various materials have been used to repair eggs, with some more suitable than others. Tape and
wound dressing products do not make an adequate seal over an opening in an egg. Similarly, surgical
tissue glue or other cyanoacrylate glues are too fluid and do not fill in fine cracks or punctures. In a
laboratory setting, where a large number of eggs are undergoing invasive procedures, high melting
point paraffin is typically used but is less practical in a small hatchery. Clear nail polish is quick‐dry-
ing and has been used successfully, especially with small eggs, but it contains volatile solvents that
have the potential to be toxic to the embryo. White glue (polyvinyl acetate – PVA) – such as Elmer’s
®
Glue All or Wilhold – although slow‐drying, is an excellent, nontoxic material for repair that also
provides some structural support and is waterproof when dry. School glue is not appropriate as it is
made to be washed out of clothing and may rehydrate in the humid incubator.
White glue should be applied with a sterile swab and using aseptic technique, thoroughly sealing
the entire crack or puncture but only covering the affected area so as not to interfere with chorioal-
lantoic respiration. For large dents or cracks which compromise the structural integrity of the egg,
thin, sturdy paper toweling (or gift wrap tissue for tiny eggs) may be used to create a papier mâché
patch. The patch should be torn (not cut) just larger than the area to be supported and carefully
pressed onto a layer of glue, eliminating air bubbles, and sealed over with another layer of glue.
Because white glue will become more fluid at incubation temperature and may run down the side
of the egg, the egg should be placed in a paper‐towel lined dish on the bottom of the incubator or
on a leveled tray until the glue is thoroughly dried. If necessary, slight hand‐turning can substitute
for machine turning during this time. It is better to take this precaution, even with a small repair,
than to come back later to find an egg glued to the tray.
Eggs compromised by cracks or excessive soil that are too valuable to discard should be incu-
bated in a separate machine from sound eggs, if possible, or, if this is not an option, at least in a
separate tray.

­ Incubation­Parameters

Natural incubation conditions create a temperature gradient from the top to the bottom of the
egg, humidity varies within the nest microclimate and turning occurs with varying timing and
radius. Artificial incubation does not strictly mimic the natural process, but rather should strive
to achieve the same outcome. Eggs should hatch in the same time period, or incubation term, for
the species as is seen under parental incubation. The chicks should be able to hatch without
assistance and be vigorous after hatching. And as with any scientific effort, these results should
be consistently repeatable.

Temperature

Incubating machines may be either still‐air or forced‐air. While still‐air incubators, those with a
radiant heat sources that circulate air by convection rather than fans, create a temperature gradi-
ent, the temperature is difficult to control, ventilation is poor, and capacity is limited due to the
necessity of setting eggs in a single layer. Temperature in a still‐air incubator is usually, but not
always, measured at the top of the egg. When using parameters developed by others, it is impor-
tant to verify how and where temperatures are taken. Nearly all incubators in current use have a