Probable Cause Corrective Measures High incubation or hatching temperatures Follow recommended incubation temperatures. Warm and cool spots in incubator due to faulty design Contact incubator company or obtain a different incubator design. Old or improperly stored eggs Gather eggs frequently, cool immediately and store eggs properly. Do not store longer than 7 days.

Contact Incubators

Contact Incubation mimics the natural incubation process that occurs in the nest.

The most striking difference between natural and artificial incubation is the fact that the natural parent provides warmth by contact rather than surrounding the egg with warm air. This may not at first sight seem significant but important research studies carried out by J. Scott Turner at New York State University and the University of Cape Town has revealed major unsuspected differences in thermal behaviour of eggs incubated by contact rather than convection.

Crucially, eggs in a forced draft incubator have near uniform temperature throughout incubation; there will be some increase in embryonic temperature towards the end of incubation as a result of increased metabolism but otherwise the whole egg will remain near incubator air temperature. By contrast, eggs incubated naturally or by contact, have significant temperature differences. Heat is entering the egg over a relatively small brood patch, which is therefore warmer than other regions of the egg and is being lost from most of the remaining shell area, which is
cooler.

In contact incubation, the embryo temperature tends to fall at later stages of incubation as a result of the embryo’s own blood circulation which becomes significantly more important than embryonic metabolism in determining temperature distribution and heat flow within the egg, quite contrary to previous understanding which assumed
metabolism to be dominant and cause egg temperature to rise. The inevitable fact that the embryo grows larger and must move from its original position on top of the yolk sack downwards in the egg to cooler regions also tends to reduce embryonic temperature as incubation progresses. These important findings emphasise surprising differences
between natural and artificial incubation, but there are others.

Eggs in nature are certainly subjected to a cycle of warming and cooling coupled with ventilation as the parent bird
leaves the nest to feed and defend territory, etc.

The first manufactured contact incubator, Brinsea’s ‘Contaq’ incubator should be viewed as replacing the natural Bird and Nest combination. The lid with the attached ‘skin’ mimics the functions of an incubating parent; providing warmth by contact with the tops of eggs, but also the facility to lift from the eggs periodically and in doing so, causes a substantial influx of fresh air in the manner of a bird standing or leaving the nest. The skin is gently but firmly pressed against the eggs by a low positive pressure of air, ensuring good thermal conduction.

The egg chamber substitutes for the ‘nest’ in providing a safe, protected environment for the eggs, with provision for air to be induced through the nest material which enables the operator to exercise control over the degree of ventilation of eggs. Nests of different species have very different characteristics, particularly with respect to gas permeability. This in turn affects water loss from eggs, so it is necessary to adjust the amount of nest material accordingly. Where required, additional humidity is introduced to the egg chamber automatically. The ideal combination of nest material and humidity setting is best determined by weighing eggs and monitoring water loss. The egg chamber is not directly heated.