A large number of people think that fostering is the easy option, where, in fact, nothing is further from the truth. It takes a lot of preparation and a lot of skill to foster a difficult species.
Obviously fostering the so called 'hardy' easier to breed species is pretty easy but it begs the question if they are so easy, why bother with fostering?
Take Gouldians for example. To foster Gouldians you need three pairs of Bengalese. From this, with a bit of luck, you could expect to produce 20-25 juveniles. In the same space used by the Bengalese cages you could accommodate two Gouldian cages. From this space, with the same element of luck, you would produce 25-30 juveniles.
So it does not make economic sense to foster 'easy' species and it is a lot more time consuming and hard work than letting them self rear.
Other than the economic disadvantage what about the ethics? There is a strong contingent out there who are against the use of fosters.
At least in the southern hemisphere, the very mention of fostering often leads to a philosophical discussion, at best, and a heated argument at worst!
Some people have justifiable concerns about the effect of imprinting. Without wishing to embark on a monologue about imprinting let me cover just a few key points. The only work on imprinting ever done on finches was done by a personal friend of mine, Klaus Immelman. Klaus worked very hard to prove that a Zebra Finch male was 'imprinted' on Bengalese. A less well publicised paper of his also pointed out that when the same male Zebra Finch was given a choice between breeding with a female Zebra or a female Bengalese, it chose the Zebra.
It is well known that hand raised ducks imprint on humans but still choose another duck to breed with although I once had a Ruddy Shelduck which had lost its drake to a fox and, embarrassingly, had decided I was the next best thing and would spend the breeding season constantly waddling and squatting in front of me! Who said I don't have sex appeal ?
Imprinting can also be used constructively as proven by the gentleman who imprinted a group of endangered cranes and led them on their natural migration route using a microlite aeroplane, not that I am trying to encourage anyone to repeat the exercise with a flock of Brolgas!
The scientists involved in the Gouldian Research Project are currently running an imprinting experiment, so before too long we will be able to publish some more definitive data.
All that apart it makes sense not to overdo fostering, partly because, surely, our aim as aviculturists must be to produce strains of self sustaining, captive bred, stock; and must surely give us more pleasure in the doing. But, also, there is a real danger that some species may lose the ability or the instinct to self rear if fostered indiscriminately for many generations.
I do actually have experience of this syndrome. In the past we did not know how to self rear Gouldians, so in Europe, we fostered them for many generations, When I eventually decided enough was enough, I decided to allow every pair I had to attempt self rearing. In the first year, half were unsuccessful after being allowed three attempts and were eliminated from my stock. The juveniles from my remaining stock were retained, together with the best parent adults . In the second season 83% successfully self reared. Any which did not were again eliminated. This process was continued and by year five, my Gouldians self reared more successfully than had the Bemgalese fosters ! Ever since my policy has been to remove poor breeders from my stock and never to use any of the few juveniles they produced either.
So-when should we foster?
The first, and most obvious, reason is where a new mutation of a 'hardy' species is produced. Most mutations produced are very weak individuals and usually do not survive long under the pressure and stress of standard aviary life. Even when they survive, and eggs are produced, infertility is rampant. The original Blue Gouldians produced a ratio of one fertile egg in every nine. If they had not been fostered it is very unlikely the mutation would ever have been established. And don't think the fostering was easy either. Blue Gouldian nestlings were originally very weak and , as their mouth markings lacked ultra violet, the Bengalese were prone not to feed them.
This is also the reason why most people do not use normal Gouldians to foster mutations. Often the mouth markings and / or the UV colouring of the gape tubercules has been affected too, which causes the fostering Gouldians to refuse to rear. Bengalese on the other hand have naturally variable mouth markings which is possibly one of the reasons they are good fosters.
Another less obvious use for fosters is as a disease break. There are some diseases like mega bacteria, for example, which are almost impossible to eradicate by medicinal methods. The best option is to prepare a separate Bengalese facility and foster a whole season's eggs.
breeding facilities, and then start all over again with 'clean' stock.
The final reason for using fosters is to establish a viable captive breeding population of a species which is rare and difficult to breed in aviculture. In this context I use fostering in a more general term and do not specifically mean Bengalese.
The parrot aviculturists have established a number of very rare and difficult to breed species by both hand rearing and fostering under compatible good breeding parents of a different species.
Some famous zoos, conservation projects and private aviculturists have established rare and endangered pigeons by using collared doves and domestic pigeons. The use of fosters has been used in conservation work on raptors, pheasants, starlings, etc.
The criteria is to get sufficient numbers to ensure the survival of the species, be it in the wild or in aviculture. Once the numbers are created then the task is to learn how to get the species to self rear successfully. Or, in other words, fostering is a means to an end, not an 'end' in itself. It is superfluous to be for or against fostering, it is just another avicultural 'tool' and not a viable economic alternative to self rearing.
First of all it is important to house your fosters in separate quarters. It is important because your fosters must be absolutely disease free.
Bengalese are capable of carrying diseases that would definitely kill the nestlings and maybe even the adults of another species and show no ill effects them selves. Cochlasoma is a good example. It has little or no effect on Bengalese but can wipe out a flock of Gouldians which have no natural immunity to the parasite.
Before using Bengalese for fostering it is important to take fresh samples of faeces from all of the cages, put them in a small plastic container with a little distilled water to keep them moist, and take them as quickly as possible to your nearest bird vet. It is best not to refrigerate them and it is good to get to your vet fast as some protozoans eg cochlasoma quickly die once they are in contact with the air and ,when dead, are very difficult to detect.
I cannot stress enough how important it is to get your Bengalese stock disease free. Once you have 'clean' stock keep them that way. Do not EVER let them be in contact with freshly purchased birds and, personally, I would say the same about the rest of your stock. Be particular with hygiene. Before entering your Bengalese room wash your hands and take every precaution when you have been in contact with other birds. If you think I am being paranoid you are dead right! Been there done that! At one time, in my dim and distant past, I had 400 pairs of fostering Bengalese. Believe me, there is no mistake you can make I haven't made and then suffered the painful consequence.
I am so paranoid about 'clean' stock I have written about that first whereas really, I suppose, I should have started off with buying your fosters in the first place.
If at all possible it is far better to purchase from an aviculturist who has a good fostering strain of Bengalese. In the Southern Hemisphere this is more difficult as there are fewer around. However, it is worth the effort as there is a huge difference in success ratios between 'ordinary' Bengalese and those which have been line bred for fostering.
To develop a good strain of fosters, the eggs of the Bengalese which are the best parents are fostered under Bengalese which were the worst performers.
Never allow the eggs of the worst fosterers to hatch. By continuing this process for many years you will develop a strain of Bengalese that will hatch dinosaur eggs!
Sexing Bengalese is very easy once you get the hang of it. Hens lay eggs and cocks fertilise them! Seriously though, I have heard a number of theories and I must say, non have really worked for me. If you only have a small number, the easiest way is to put two birds in a cage with a nest box. If they lay fertile eggs, they are a pair. If they lay infertile eggs, no matter how many are laid, they are hens. If they lay no eggs at all, almost [ but not quite ] inevitably cocks. If you put different coloured split rings on your birds, you can sit there and identify the cocks when they crow. A sophistication of this, which is the best way if you have cages with a solid slide divide, is to put one bird in each cage. Ensure they cannot see each other or any other Bengalese and leave them isolated for 48 hours. Pull the divide between two birds. The cock will crow and display immediately and then can be pulled out and given a blue band [ blue for a boy, pink for a girl ] Any bird which does not display, leave in for a further period. Sometimes a sub-dominant cock will not crow first time. If it does not display and crow on the second attempt; it is a she !
The next decision is whether to use pairs or trios. Never ever use a pair consisting of two hens, it never works as the two hens will inevitably not synchronise on the same breeding cycle and you end up with one bird trying to lay eggs and sit whilst the other is trying to feed nestlings. Usually with terminal results !
A standard pair is good and works well.
A hen with two young first year cocks also works well and can be particularly useful when you are trying to foster a species which is more difficult to foster or where there are large broods.
A trio or a couple of trios of young first year cocks can be very useful. Give them a nest box and some plastic canary eggs or addled eggs to start them off. Once they are sitting, you can introduce whatever you like. Eggs, or nestlings at any stage. They are very versatile and will successfully rear a brood of nestlings which are all at a different age. Very useful as an emergency thing. However do not try this trick with second year birds, it does not usually work.
The other trick of the trade is to imprint your Bengalese on the species you want them to foster. This means never ever letting them rear anything other than the species you wish them to specialise in. This works particularly well with the difficult to foster species. One renowned Dutch breeder even went so far as to rear his young Bengalese with the young of the species they were going to foster. He also confessed to me that he had actually fostered Bengalese eggs to some of his rare species whilst the Bengalese reared theirs! His list of 'first breedings' was legend !
An ideal cage size is around 40cm longx35cm wide. Obviously it does not want to be too small but then neither does it want to be too big. You need to keep the Bengalese where no matter where they are in the cage they can hear the nestlings calling. This stimulates feeding.
The cage should only have two perches with the top one placed directly under the nest box, this means they spend most perching time right by the nestlings. The other perch needs to be low enough to the floor of the cage so that if any juveniles fledge early or crèche then the Bengalese is within easy feeding distance.
Feed the very best available. They need to be the healthiest, fittest birds you keep. They will survive on rubbish but presumably you only have Bengalese because you keep some rare and expensive birds. I will leave the rest of the logic to your common sense.
Getting cleverer than that though, the diet you feed your Bengalese is dependent on the species you wish to foster.
To take the more extreme cases. Some species are highly insectivorous when they have nestlings. This is where you have to know your bird. Some species are almost entirely insectivorous for the first 4-5 days others feed insects through to weaning. Others stop feeding insects just before fledging and, of course, some, like Gouldians, feed no insects at all.
It is important, therefore, to train your Bengalese to readily eat whatever you wish to be fed to your nestlings. It is no good getting nestlings and then feeding mealworms to Bengalese which have never seen one before.
So this is the 'craft' of fostering. I cannot give you details because it depends on the species, but, as an example, for a species which takes only insects for the first few days, I would remove all hard seed, lightly spray the insects with a dilute mixture of honey water and then sprinkle a multi-vitamin/mineral mix over them, [using an old pepper pot], before feeding.
With other species we take out the hard seed but leave a choice of sprouted seed, soft food and insects.
One of the benefits of using Bengalese is that you can do a nest box inspection as often as you want, so monitoring progress is simple.
With some really difficult species, particularly those with mouth markings entirely alien to Bengalese, it may be necessary to supplementary hand feed from time to time, using a crop needle.
If nestlings die at roughly the same age every time and the Bengalese are doing their job then it is more than likely your diet is at fault.
Another good practice is to monitor the nestlings droppings. Once you become experienced, you can tell at a glance whether all is well or not
As a guide line you will need three pairs of Bengalese to every pair of birds from which you need to foster.
The art is to get your Bengalese breeding in sequence so that one pair has 3-4 fresh eggs when you are ready to transfer. You have to catch the Bengalese at the beginning of their breeding cycle, particularly as many species have a longer natural breeding cycle than Bengalese. This is also important because the state of the food fed to the nestlings needs to vary with their age. For the first few days of hatching they will need to be fed partially digested food. The Bengalese do this naturally as their crop lining swells and they produce a glut of enzymes providing they are in the correct cycle. As the nestlings mature and their own endocrine system kicks in, the Bengalese feed a higher proportion of undigested food.
When transferring eggs it is important not to touch them with your hands. The sweat from your hands will destroy the natural protective coating on the egg and allow bacteria to enter and prevent hatching.
In Europe you can buy special calipers for transferring eggs but a plastic spoon held in hot water and then the sides bent in works well too.
Mark any eggs you transfer with a standard solvent based felt tip pen. This will enable you to identify and remove any Bengalese eggs which are laid after transfer. If you miss an egg and allow a Bengalese nestling to hatch they will feed that in preference and abandon the rest. So-not a good idea!
I suppose one could write a book on detailed technique but to close, if you live in colder climes, there is a benefit I forgot, and that is where tropical birds which do not brood or brood lightly, you could use Bengalese instead of a heated nest box or heated bird room
And finally, although I do have 11 pairs of Bengalese, since coming to live in Australia, I have never had time to use them.
Fostering is a great supplementary technique but very labour intensive and time consuming.