Modern Captive Breeding–Part III
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.
To simply leave the eggs with the parent birds would at first
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.” 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 raptors and there is a high skill factor to be learned as to their husbandry. Most larger breeders tend to shy away from this method as it is another job in itself. An incubator is required to complete the hatching when using nonraptor surrogates.
Over the last twenty years the use of electromechanical incubators has grown in popularity not only with raptor breeding but also in many other branches of aviculture.
Major steps forward have occurred in this field not only with the advancement of the machines themselves but also in our understanding and knowledge of the parameters needed to successfully hatch a high percentage of eggs.
It is essential that a deep understanding of the egg’s needs during incubation be acquired prior to trying to incubate valuable eggs. Once a good grounding has been acquired then you need to gain experience, which can only be obtained by trying out your techniques. In most cases you are chasing your own tail, as with generally only a small number of eggs being produced and incubated annually, it is hard to gain experience. I have been fortunate in this respect; as well as incubating several hundred raptor eggs annually we also house a large parrot collection and it is rare for us not to have at least a few eggs in the incubators all year round.
As to the question of which is the best type and make of incubator, again experienced breeders hotly debate this. We use the RollX and TurnX incubators produced by Lyon’s Electrical Company and during the last season we have added a number of Grumbach S84 incubators which we are extremely impressed with. There are a number of other makes of incubators which
some breeders have expressed their confidence in. It is now the accepted view that forced air incubators (ones with a fan to circulate air, as opposed to a still air machine, which relies on convection) are far more accurate when it comes to maintaining a constant temperature.
The five key elements of successful incubation are as follows:
1. Quality fertile egg.
3. Temperature control.
4. Correct amount of turning.
5. Humidity control.
Quality Fertile Egg
For an egg to stand any chance of hatching, it has to be of the highest quality. Diet is the main contributing factor, and small
inadequacies in the female’s diet will show up as poor hatchabilitv. Unfortunately, unless the egg has a poor shell quality, which is obviously seen, the egg gives little away optically as to its internal qualities. Eggs which fail to hatch, can he sent for laboratory evaluation of their nutritional makeup, with a view to finding any shortfall. However the results are usually compared with those obtained from poultry and any comparisons should he viewed sceptically.
Fertility can usually he determined by clay 5 or 6 of incubation via candling. Candling, is the term used to describe placing the egg over a cool strong contained light source to view the contents of the egg through the shell. At this period of incubation, if fertile, the yolk will become mare defined in shape and begin to expand in size. Accipiter, buteo and eagle eggs are more difficult to candle than falcons due to their more dense and thicker shells.
Although eggs have a mild resistance to bacteria found in the wild nest, the bacteria found in captivity is generally of a different type and can be lethal. As an egg is laid it cools and contracts rapidly, any bacteria in contact with the egg may be drawn through the shell. For this reason nest ledges and platforms
should be kept as clean as practically possible and yet again clue to easy access this is more easily achieved with imprinted birds.All incubators must be cleaned thoroughly and fumigated prior to use, and frequently throughout the incubation season. This is also the case for egg transport boxes, scales and any other areas the eggs may come in contact with and particularly the human hands.
Eggs that we find to be dirty or soiled when removed from the nest, are cleaned with warm water before being placed in the incubator. There are a number of commercial egg sanitant solutions available, and if used, it is imperative that the instructions are followed exactly as they have the potential to harm eggs if not.
Types of bacteria found on a tree nesting accipiter egg against a cliff nesting falcon egg will vary, and although it usually doesn’t affect its natural host it may well be lethal to another species eggs. With this in mind we try not to have too dissimilar eggs within the same incubators. We have found merlin eggs in particular, to be very prone to cross infection from other eggs.
Eggs that are found to be infertile or which have ceased developing (died) when candled are removed from the incubator
Hygiene levels cannot be over stated in incubation, and it is a constant battle. In the ideal world each egg would have its own