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Modern Captive Breeding by Peter Gill……….continued |
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shavings on the basis that it may be
a possible source of aspergillosis. We have had no instances of this, even
with species kept on them that are very susceptible to the complaint i.e.
Goshawks, Golden eagle and Gyr falcon. If the shavings are kept dry then
fungal problems should not occur. Indeed fresh pine is a natural
disinfectant. Nutrition Very little scientific research has
been carried out into raptor nutrition. Of all the areas of research needed
in raptor propagation this is at the top of the list. The difference between
an average diet and one approaching optimal nutritional requirements can be
the difference between being successful with your propagation attempts and
failure. Sub optimal diets can manifest themselves via infertility, poor
hatchability and weak chicks through to no breeding activity at all and in
severe case disease and illness in the adults. Numerous falconers have viewed
a general concern that captive bred birds seem to be getting smaller.
This is not something I have noticed in my own birds but enough falconers
have commented on this with regard to birds bought elsewhere for it to be an
issue. One answer generally given is genetic inbreeding, but although this
could he a reason 1 believe suboptimal nutrition at the time of rearing, to
be a more realistic answer. To the novice, a diet that is as
close to the bird's wild prey would seem to be the ideal choice. Well, apart
from the problems of obtaining the prey source in sufficient quantities and
the health risks associated with wild food, is it nutritionally adequate for
the captive raptor? We believe it isn't, for the |
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following reason. There are around forty known nutrient
requirements (and probably more) which a raptor receives from its prey. These
consist of fats, proteins, minerals, vitamins and trace elements. In the
wild, the energy requirement of a raptor dictates the amount of food, which
it needs to eat. So if for sake of argument and as an easy to follow example,
a wild female Peregrine eats 300 pigeons per year to meet its immediate
energy requirements, which is obtained from the protein and fat content from
the pigeons. At the same time it consumes all the vitamins, minerals and
trace elements from the pigeons it requires to keep the body functionally
correctly. Once the Peregrine enters a breeding pen its energy requirements
drop. To fall in line with this drop, and based on my experience, the
Peregrine now eats up to a third less food, so it now eats 200 pigeons. The
problem is that all the vitamins, minerals and trace elements have also been
reduced by a third. It is not known precisely what levels of these the
raptor, requires for the body to function correctly, but it's almost certain
that this shortfall of a third is far too much. So the ideal diet is one with an
energy level, which meets the raptors immediate needs and contains all the
other nutrients at the sufficient levels required. This is where the two
areas of research are required. First, what are the exact requirements of
these levels, and second what food source can be produced in captivity and
under what dietary conditions do they need to be fed, to reach the levels
required. Of course this is impossible to work out exactly, as the
requirements will vary for different |
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species, between sexes within a
species, ages of birds, the time of the year etc. etc. but I hope this has
provoked some thought on how complex diet is and how far we are from finding
a form of optimal nutrition. With these problems in mind, we are
strong believers in giving our birds nutritional supplements. Increased
supplementation can be achieved by placing the supplements directly onto the
food source, or by feeding the food source high levels of supplements when
they are being reared. Of course there is a limit to the level of
supplements, which the food source can hold in its body. Supplement enhanced
quail, are the most often used food source if this avenue is to be taken. It
should be remembered that whatever you decide to feed your raptors, the
nutritional content is directly proportional to the food, which the food
source has been fed itself. In an ideal world and from a control point, it is
better to breed and rear the food item yourself. This may not be practical in
most cases, but some investigative work should be undertaken as to how your
supplier has reared your food. We never feed wild food, simply
because of the disease factor. It is though possible to go too far the other
way. Let's say for example we hand rear a Merlin on laboratory-produced
mice. As the Merlin has never been in a nest with other siblings and parent
birds, and as it has been fed a very clean mammalian diet, will its immune
system be strong enough to cope once it catches and eats its first Skylark? A
closed sterile system of rearing chicks does not work when rearing birds for
falconry. Of course we have to be as clean as possible in choice and
preparation of food used for rearing, but total exclusion of germs from the
outside world is not possible and not required. With regard to water, raptors should be given the option of fresh
water at all times. Some females at the egg laying stage will |
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drink regularly, after all, an egg consists of around 70% water. Most food items have to be frozen and stored, and again great care
should be taken with your freezing and thawing techniques. By far the best
method is blast freezing. Some food suppliers have invested a lot of time and
money to perfect their freezing and storage methods here in the UK. |
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Article and pictures courtesy of International
Falconer Magazine |
