able success.

But if incubating eggs from day one of incubation, our experience is that this is not enough. Some of these eggs will hatch but some is not enough. Most modern incubators turn once per hour, but at the time of writing we are experimenting turning eggs during their first third of incubation every fifteen minutes. The reason for this is that it has been found that some softbills and macaws with a small yolk to albumen ratio, similar to raptors, have a far better blood membrane growth if turned more frequently than the standard once per hour. If eggs have been naturally incubated for the first third of incubation, then once per hour is frequent enough.

Humidity control

All eggs need to lose a percentage of weight via water evaporation through the shell to hatch successfully. As a general rule, a total of around 15% should he lost in weight, measured from when the egg is first laid to the egg starting to pip, and then a further 3% to 5% to hatch. The main period of time we are initially interested in, is from the egg starting incubation, through to it making its first pip mark in the shell. Why does an egg need to lose weight? The reason is that as the chick starts to respire, a

byproduct, as well as carbon dioxide, is water. This water must be diffused through the shell to stop the chick from drowning at the internal pip stage when pulmonary respiration starts.

incubators are never stored, as this may complicate the warming up procedure even more.

Turning of eggs

All raptor eggs have to be turned at regular intervals throughout incubation. In the first half of incubation the germinal disc floats on the top of the yolk and feeds from the. nutrients that it is in contact with, so by turning the egg it will reach a new feeding area. If the egg is not turned the developing embryo will stick to the side of the shell and the result is death. Research in poultry eggs, which weren't turned at all in incubation, showed a hatch rate of only 3%. In the great majority of cases the chick is mobile enough in the last quarter of incubation not to require turning. However most breeders including myself, keep the eggs turning until they pip.

When being turned, the egg should rotate approximately 180 degrees in one direction, and on the following turn, back in the

opposite direction to its starting point. With regard to the frequency of turning, we know from experiments with electronic eggs placed under raptors, that this occurs randomly every thirty minutes through to two hours. However, we really need to know

what's best in an artificial environment. Some people hand turn their eggs between five and eleven times per day (always an odd number, so they are not on the same side each night) with reason

any erroneous temperatures have occurred, are more than likely to have died from this problem.

When starting eggs fresh in an incubator, great care should be taken on warming the egg up to incubation temperature. Placing a cold egg directly into an incubator will be too much of a temperature shock. Under a parent bird the egg is warmed up gradually to incubation temperature. If we are incubating an egg from day one we take one of the following steps. When removing an egg from the nest, if it is found to be freshly laid and still warm, then it is weighed, measured and placed straight into the incubator. If' the egg is cool, we then warm it up in a spare

incubator by starting at ambient temperature and turning the incubator up gradually over a couple of hours until we reach incubation temperature Eggs that are to be incubated from day one in

incubator, but we have to be realistic.

Temperature control

The correct incubation temperature for raptors is between 37°C and 37.5°C. Larger eggs (eagles) are at the lower end of this scale and the smaller eggs (merlins) at 37.5°C. If the temperature deviates from this the overall effects will depend on:

1. The degree of inaccuracy.

2. The period of time that the eggs have been running at the erroneous temperature.

3. At what stage of incubation the eggs are at.

Eggs have a higher survival rate if the inaccuracy is below the optimum temperature than above, particularly in the latter half of incubation. A small discrepancy of say 0.5 to 1 degree for a short period of time should have no significant effect. Much more than this and overall hatchability is usually reduced. Eggs run slightly on the high side will pip up to a day early and the opposite for eggs run slightly low. If a slight discrepancy is found, do not try to equal it out by running the machine on the opposite side of the optimum temperature, just adjust the machine back to the required temperature.

It should he noted that eggs which overheat or cool for excessive periods might show no problem at that point when candled. However, as temperature is the timing catalyst for the vast

amount of chemical processes taking part in the development of the embryo, minor temperature problems that occur may not show up until a latter period. So eggs which die several days after

Modern Captive Breeding – Part III ...continued