Fostering To Be Or Not To Be ?


 By Mike Fidler.


Many years ago, I used to have 2 teams of 400 pairs of fostering Bengalese,i.e. 800 pairs.

Each pair was used to foster 3 rounds of eggs and at the end of the breeding season 200 pairs of the very best fosters were left to self rear one round of their own. The purpose of that was to produce the next generation of fosters.

Once their work had been done they were disposed of – usually just given away as there were too many to have any monetary value and the cost of paying for the labour of looking after them and their food was greater than the wholesale value. Plus they were not of real value to any other serious aviculturist as they had been hard used for nine months and needed to have a rest and moult before they were ready to be used again.

As the first team finished their tour of duty the cages were stripped down and together with the fostering room were thoroughly cleaned and disinfected.

Once the cages were replaced the second team was put down for breeding and the cycle continued.

Logistically to support this procedure we needed 400 breeding cages 40 large stock cages which held 20 birds each and housed team ‘B’ males in 20 cages and females in another 20.

When the first team finished their cycle we needed 20 spare stock cages of the same size to put them in for the period of time it took to get rid of the surplus, these were then used to house the first of the new generation fosters as they were produced.

We had special small cubicle sexing cages with solid removable dividers. Each compartment held one bird in isolation for 4 days, after which the divider between 2  bengalese was removed. Males tended to display immediately and were given a blue ring for the boys and put in an all male stock cage.

If a bird did not display it was kept in isolation for another 4 days and the process repeated with another bird partner. If it still did not display it was deemed a female and given a pink ring.

In the main this process worked well and was the least labour intensive and efficient method of sexing we could devise. There was no DNA testing in those days.

Once a team of 400 pairs was achieved any surplus was got rid of as quickly as possible.

For every pair of Gouldians, you need 3 pairs of bengalese to cope with the number of eggs produced and to maintain a synchronous breeding cycle. So this means we had 2 teams of 140 pairs of Gouldians, i.e. 280 pairs. Slightly more than needed but this covered deaths etc.

To house these we needed 140 breeding cages and 14 large stock cages to hold the second team. They used more space as Gouldians cannot be crowded without losing birds through stress.

Once weaned, juvenile Gouldians were placed 6 to the cage in 80 stock cages, and then transferred to a moulting room at 6 weeks old. The moulting room was maintained at a temperature of 35C which induced a rapid moult.

At our height we produced over 3000 Gouldians a year, but what an exhausting exercise!

And it definitely wasn’t fun. You might justifiably ask why I did it and the answer would be – by accident!

All of my life I seemed to have been busy and have frequent spells away from home. So for most of my life I have had to employ a bird keeper to look after my birds.

Without going into a long story of justification I expanded the birds we bred to keep full time bird keepers busy because I was fed up with ever changing, poor quality part timer staff.

So how did it end? Well first of all because I was no longer enjoying my lifetime hobby and secondly it is not economically viable.

Each pair of Gouldians will produce 30 eggs in a breeding cycle, sure you can take more, but then you start losing fertility, hatch rate goes down and then your bengalese team are under utilised. And each pair of Bengalese costs as much to keep as a pair of Gouldians.  Thirty eggs represents 6 rounds of 5 eggs a time and an average breeding cycle time of around 6 weeks. Six rounds therefore takes approximately 9  – 10 months.

A good healthy strain of birds can produce an average hatch rate of 70% delivering 21 juveniles per pair per complete cycle. Yeah, yeah!!! Someone out there is going to say they had a pair which laid 7 eggs and every single one hatch and rear. The best I ever produced was 9 eggs, 9 hatch and 9 rear, AND SELF REARED AT THAT!

But all the above figures are from accurate records, kept over a period of years.

They are REAL WORLD figures!!

So scale down the figures and work it out for yourself.

We had the capital cost of 720 cages and the cost of setting up the bird rooms and moulting room [ which was divided into indoor aviaries], plus heat, plus light, plus food, plus staff. In that volume, at least 50% of surplus birds will be sold at wholesale price. There was shipping costs and all sorts of incidental running costs that could not be budgeted for.

One year we had a virus run through the stock which meant there was a 6 month gap in production and sales. Ignoring the ethics, if we had attempted to sell infected stock we would have lost our reputation and hence our market.  If it had been a business having to pay salaries and overheads, we would have been bankrupt!

With the bengalese you have to keep checking the nest boxes and record when the first egg is laid. When the 3rd egg is laid they are removed and replaced by a clutch of Gouldian eggs. This is done on the Bengalese’s third egg as an average hatch time for a Bengalese egg is 14 days whilst it is 16 days for a Gouldian. From hatch to independence takes a Gouldian 40 days and bengalese 35. So the bengalese need to be manipulated to ‘go the distance’.

Of course the bengalese will lay at least 2 more eggs and it is important that these be taken out as the foster parents are very prone to feed their own young and exclude the nestlings they are fostering.

To be able to identify the bengalese eggs when they are laid the Gouldian eggs are marked on their blunt end using a solvent based felt pen.

It is important to remember that when transferring eggs one should wear surgical gloves. The sweat from your hands will damage the coating that protects the eggs from bacterial infection. Failure to do so will affect your hatch rate, particularly in summer.

So by now you gather that using fosters to breed Gouldians is not an easy option. In fact if you are to gain any benefit from fostering at all it is logistically a very precise and labour intensive process.

Even the record keeping is more arduous as you have to keep records of the Gouldians’ activities and a transfer record on both the Gouldian cage and a duplicate record on the bengalese cage, to keep a track on who has what.

I could ramble on about the minutae of fostering but all I wanted to do was to point out how labour intensive and space consuming it is.

You can replace every bengalese with a good self rearing strain of Gouldian and produce almost the same number of juveniles with a fraction of the work.

To actually produce the numbers quoted from a fostering exercise, the timing of transferring eggs and weaning youngsters is critical. Only a few people are that precise and that well organised. This means that those people who self rear are likely to produce more youngsters than fostering.

Also as a warning only bengalese which have been line bred for fostering have any degree of reliability.


Fostering only has a benefit for those rare birds which for one reason or another you think is advisable not to chance self rearing. This would perhaps apply to a new mutation for example which lacks the vigour to self rear. A new mutation may also have a very poor fertility or survival rate and therefore to maximise numbers and get the new mutation established, one might resort to fostering.

In the early days we knew very little  about how to breed Gouldians and also the stock we had was not of today’s quality. If we had not used fosters I honestly doubt we would have Gouldians in captivity in Europe today.

In my own case I have not fostered a bird for over 35 years [ yes I am getting old! ] and if I had to foster Gouldians, I would just use another pair of Gouldians. I can’t see the point of wasting cage space, food and labour on keeping bengalese on the off chance that one might need to use them.

That said let me stress I am not rabidly anti fostering it is just that it is not economically viable, is highly labour intensive and, in my case at least, I just don’t enjoy it.


Much is talked about ‘bengalese disease’. This is a syndrome where bengalese nestlings hatch and survive with no apparent problem but when the same parent bengalese are given Gouldians to foster all the nestlings die.

The reason for this is that bengalese have a very effective immune system and are capable of carrying a low level bacterial or parasitic infection without any impact on their apparent health or productivity.

To minimise his problem most people who habitually foster resort to medicating their stock just prior to the breeding season. This works pretty well unless your stock is infected with cochlasoma. This is a parasite which once contracted is extremely difficult to eradicate and can only be identified by a qualified vet. It is this ‘mystery disease’ which is usually called ‘bengalese disease’.

That said there are circumstances, fortunately reasonably rare, when introducing fostering as a ‘disease break’ is the only way to retain valuable stock which one may have line bred for a number of years, but has become or is in danger of becoming infected with a virus.

This problem usually occurs when you introduce a new bird into your stock which is infected or is a carrier of a Gouldian specific virus.

Although it is pretty rare, I could also argue that it is more common than many of us think.

These virus usually come in waves every few years, a bit like the different ‘flu viruses’ which infect humans from time to time.

Under these circumstances you need a meticulous hygiene regime and a separate room to house some bengalese. The Gouldian eggs are then fostered under disease free bengalese and obviously kept separate from your main stock.

When you have enough juveniles to perpetuate your strain all the rest must be euthanised.

It sounds harsh and it is very hard to do, but the stock birds which survive have become immune to the virus, but have a high probability they are carrying a low level of the infection which would transfer quickly to the non immune birds.

So her is the dichotomy.

Do you keep the survivors from your original stock and breed from them because they are now immunised against that particular virus, but- if you sell them to someone who has never had the virus there is a possibility you will infect their stock; or do you euthanise them and only use ‘clean’ stock?


Occasional fostering probably has no lasting impact on the well being and quality of your stock.

There is no evidence of imprinting in juveniles which were weaned from their foster parents between 40-42 days from hatching and then being placed in holding cages with other Gouldians.

Experiments with zebra fiches has shown that when brought up in isolation by fosters and then housed with bengalese and having no contact with any other zebras at all then imprinting does take place.

The latter experiment was pretty extreme, but it does demonstrate that imprinting could become a problem if husbandry practice was poor.

Exclusive and long term use of fostering does have a downside impact and could lead to severe problems if continued for many generations.

The downside effects are:

a) Losing the instinct to breed. Despite a  good husbandry regime, pairs are reluctant to breed, scatter the nesting material and the female lays eggs in a desultory fashion on the bare nest box floor.

b)Fertility drops in line with the males’ lack of interest in breeding.

c) Pairs will no longer self rear even when given every encouragement and opportunity

d) some females become egg laying machines and lay dozens of eggs, often infertile, and frequently succumb to a secondary disease.

e) long term we could end up like some of the breeds of canary and some strains of budgerigars where the instinct to breed has all but disappeared.

In my own case, when I decided I was only going to self rear after many generations of fostering, the first year approximately  50% of my stock did self rear and the other 50% did not. I obviously only kept self reared youngsters and when they were paired 60% self reared 40% did not. It took about 5 years of selective breeding before I had stock which equalled if not bettered the numbers I got from fostering.


So in closing. The benefits and liabilities of fostering are pretty obvious.

It is the usual thing. A glass or so of wine probably does you good but consistently drinking a couple of bottles a night almost certainly does not.

And this is the same with fostering! Economically there is no case for fostering unless you have an unusual or new and difficult mutation.

If you are line breeding and there is one particular pair of birds progeny you want to maximise one year, foster under an inferior pair of Gouldians. Much easier, much safer, much cheaper than keeping Bengalese on the off chance!!

1 Comment

  1. Pingback: Two new Post of intrest. - Naturally for Birds

Log In

create an account