Modern Captive Breeding – Part III by Peter Gill

The sight of your first captive produced egg, is generally easily remembered by any breeder. But this is only one step, be it a very important one, to be passed prior to a successful breeding.

The next hurdle is incubation. As with other areas of captive breeding, you are faced with several options to choose from as to how to incubate your eggs.

Leave them with the parents for them to hatch.

Place the eggs with another incubating bird whether another raptor, bantam or pigeon.

Artificially incubate via the use of an electro/mechanical incubator.

Each aspect has its pros and cons and your own individual circumstances may dictate the course you have to take. Many breeders will extol their preferred method, but these methods generally result from a small number of eggs that they have incubated, and from a limited number of females. Only by trying each method over several seasons with a large variety and quantity of eggs, does a true picture become apparent as to the merits of each type of incubation.

NATURAL INCUBATION

To simply leave the eggs with the parent birds would at first

glance seem the obvious choice to the tyro propagator. However, like numerous other decisions that you are faced with when captive breeding, this is not as straight forward as it first seems. A primary problem is that not all individual birds make good parents when it comes to incubation. Some will break eggs either by accident or

SURROGATE PARENTS

The use of a surrogate parent for incubation whether another raptor, bantam or pigeon is an option open to the propagator.

Imprinted raptors tend to be the best option, as the placing and removal of eggs is straight forward and close observation is easily achieved. The surrogate female should have laid her own eggs and be broody before any eggs are placed with her. The length of time a raptor can be kept broody will vary between individuals, but common sense should prevail on the period of time the bird has been sitting over its normal incubation period. As to the number and size of the eggs requiring incubating, they shouldn't be too dissimilar to the surrogate's own eggs. As an example, most large falcons will sit one another's eggs and redtails or common buzzards will sit Harris' hawk and goshawk eggs and viceversa.

Once broody, most imprinted females are very intense and diligent with incubation. Our female golden eagle refuses to even stand up when we remove eggs from her and we have to place a hand under her and feel for the eggs. We have several imprinted falcons that can be aggressive toward us prior to laying but once broody and with the change in hormone levels, they always become extremely tame.

Some breeders use bantams or pigeons as surrogate sitters. These

birds should be kept to an equally high standard as one keeps rap

intentionally. Others will stop and abandon sitting at any point during incubation for what seems no reason at all. A particular area of concern is at hatching time, where some parent birds (male or female) will eat their emerging offspring.

A second point to consider is by leaving the eggs with the parents, generally only one clutch will be laid. A few individuals, particularly Harris' hawks have incubated and reared young and then laid and reared a repeat clutch in the same season. For a raptor to be persuaded to lay a repeat clutch, its eggs should be removed from it before or up to two weeks from the last egg laid.

If this is your chosen method of incubation then as well as close observation there are several other items of management which may be of aid. The clutch of eggs should be checked for fertility once they have received 710 days of incubation. If they prove infertile, then by removing them at this point a second clutch may be laid 824 days later dependant on species, giving a second chance of fertility in the same season.

As a small insurance policy, a couple of eggs may be removed from the nest to an incubator just prior to hatching, just in case the parents kill the young as they hatch. If all goes well in the nest, then the incubator hatched young can be put back in the nest for rearing at 2 or 3 days of age, thus the old saying "don't place all your eggs in the same basket."