By Dr Colin Walker BSc, BVSc, MRCVS, MACVSc
Anatomically speaking, a bird’s respiratory system has
some similarity to our own in that inhaled air travels down a central
windpipe, which then opens into a set of lungs. There are, however,
several critical differences. In an evolutionary sense, the respiratory
system of birds is more primitive anatomically than our own. Birds
do not have a diaphragm, which is the muscle sheath that separates
the abdomen from the chest and contracts to create a negative pressure
in the chest cavity causing air to rush down the windpipe into the
chest. Also, the ability of the respiratory tract to heal after infection
or injury in birds is considerably reduced. A major anatomical difference
is the presence of airsacs in birds. Although regarded as primitive,
the bird’s respiratory system has some amazing functional advantages.
Airsacs are transparent tissue balloons that open off the lungs.
Because they occupy a lot of internal body space, this means that
much of the bird is filled with air and therefore comparatively light,
making flight easier. Because of the nature of air flow through the
airsacs, fresh air can enter the lungs both during inhalation and
exhalation, making for very efficient oxygen delivery to the tissues.
This is part of the reason why pigeons have the stamina and speed
that they do. Fast humans can run 100 metres in 10 seconds, while
a good greyhound can run 300 metres in 16 seconds but compared to
a pigeon they are ‘stuck in third gear’. Pigeons can
not only match the greyhound’s fastest speed but maintain this
velocity for hours and hours and, of course, they can fly even faster
if they need to.
Apart from being involved with buoyancy and indirectly with oxygen
delivery to tissues, the air sacs are also integral to maintaining
normal body temperature and fluid levels. Birds do not have sweat
glands and so can not cool themselves by evaporation of moisture
from their skin. When hot, their only metabolic option for cooling
is to evaporate moisture from the lining of the airsacs. This is
why, when pigeons become hot, they start to pant. The resultant
increase in air movement over the airsacs leads to increased moisture
evaporation, which, in turn, leads to loss of body heat and cooling.
Because this method of cooling involves the loss of moisture,
it is vital the pigeons have access to water to replace the fluid
lost, otherwise the birds will start to become dehydrated.
Panting and Disease
Panting, at times, can be of concern for fanciers because birds
with a respiratory infection are more inclined to pant. As mentioned,
however, panting is not always a sign of ill health. As explained,
panting encourages evaporation from the lining of the respiratory
system, in particular, from the airsacs. This evaporation cools
the bird in the same way as an evaporative air conditioner and
is, in fact, the only way that birds can cool themselves in this
manner because of their lack of sweat glands. It is therefore
a normal mechanism by which healthy birds can cool themselves.
In birds with inflamed airsacs, moisture fails to evaporate from
the airsacs in an efficient way, resulting in incorrect amounts
of moisture being lost. If too much moisture is lost, this leads
to dehydration and makes the birds thirsty. Alternatively, if not
enough moisture can be lost from the airsacs, then evaporative
cooling cannot occur and the birds become ‘overheated’.
Either way the result is protracted panting. This is why birds
with inflamed airsacs are more likely to pant excessively. In the
longer term, interference with oxygen delivery to tissues inhibits
the development of race form and predisposes birds to muscle cramping.
A failure of this mechanism therefore has a disastrous effect on
the bird’s stamina.
Panting In Young Birds
A common concern of fanciers who contact the clinic during January,
February and March (the post-weaning time in Australia) is that
the birds are panting and reluctant to fly around the loft. Certainly,
birds that have a respiratory infection are more inclined to
pant but more often than not, during this time of year, the panting
is associated with other factors. The weather at this time of
year is often hot while the growing young birds have yet to develop
any real fitness. At the same time, they are moulting, which
can lead to increased effort involved with flight. Panting, however,
does alert the fancier to the possibility of a respiratory problem.
Inflamed airsacs do not work as well and so the birds try to
compensate for this decreased function by increasing the amount
of air flow over the airsacs through panting. However, if panting
is associated with inflammation of the deeper respiratory structures
(such as the airsacs), it is usual to also find signs of inflammation
of the upper respiratory structures (such as the sinsues and
windpipe). Fanciers can expect to see watery red eyes, swollen
sinuses and nasal discharge and to observe sneezing. If signs
consistent with upper respiratory tract inflammation are not
apparent, it is unlikely that any panting observed is due to
inflammation of the deeper structures such as the airsacs. These
signs are therefore more reliable indicators of a respiratory
infection during this time.
Often, however, signs can be very subtle, particularly in older
youngsters where a reasonable natural immunity may have already
formed. All that may be noticed here is an increased level of panting
coupled with a subtle decrease in flying in a team that had been
flying the loft well. In these older youngsters, sneezing in particular
is a good indication of low-grade sinus irritation. If respiratory
infection is suspected, a veterinary visit and health check are
A health check involves a microscopic examination of a faecal
smear and a crop flush. The faecal smear is examined for evidence
of parasites. Worms and coccidia sap the energy of the growing
pigeon and not only compromise long-term development but lead in
the short term to poor exercise tolerance and predispose the birds
to panting. The crop flush is examined for wet canker and heterophils.
Heterophils are white blood cells that weep away from the inflamed
lining of the sinuses and windpipe into the throat, if inflammation
is present. Their appearance is therefore a good indicator of respiratory
Often, however, if respiratory infection is diagnosed at this
time it is not treated. The usual causes of respiratory infection
are chlamydia and mycoplasma. Young birds need exposure to these
organisms to develop a strong natural immunity. Any treatment programme
must be aimed at the development of a strong natural immunity by
the start of the racing season so that the birds will be able to
tolerate high levels of stress and disease exposure once racing
starts. Treating the birds in the post-weaning time certainly keeps
them well but does not allow for the disease exposure required
to stimulate the development of a strong natural immunity. If mild
respiratory infection is detected, then any parasitic disease detected
during the health examination is treated and this, coupled with
ongoing good care and the maintenance of a clean dry loft, often
results in the birds mounting an immune response and becoming well.
This ongoing low level of disease exposure acts like a mini vaccination
and helps develop a good level of natural immunity. Respiratory
infection at this time is only treated directly if things progress
to the stage where they are compromising the bird’s development.
Full details of this treatment are outlined in my latest book ‘The
Flying Vet’s Pigeon Health & Management’. Do keep
in mind, however, that most panting in young birds is associated
with either the moult, hot weather conditions or a lack of fitness,
rather than a respiratory illness.
Whether the birds are overweight or at a difficult stage of their
moult can be determined by handling. Exercising the birds in a
cooler part of the day will allow a fancier to determine if the
panting is heat-related.
Panting and Aerobic Exercise
Healthy fit birds that are forced to fly hard for a short period
of time will pant. They do this to compensate for the oxygen
deficit created by the burst of activity, in the same way that
a marathon runner will pant for a short period of time if forced
to sprint. We see this in lofts where the birds experience repeated
falcon attacks. Birds in such situations are often reluctant
to leave the loft but when forced to do so often fly in tight
hard circles around the loft, being reluctant to range in case
they are surprised by a falcon while away from their loft. In
most Australian States, February to May are the months that hawk
and falcon activity is highest. The fear that establishes itself
in some teams is obviously quite high because some will continue
to fly like this even when hawk appearances decrease, almost
as if the behaviour has become a habit. Often the only answer
is to short toss the birds for 7 to 10 days. This breaks the
habit by building up the birds’ confidence while at the
same time giving the birds adequate exercise.
After any exercise period, there may be individual birds that
pant. These are usually birds that for one reason or another are
finding it hard to keep up with the others. These individual birds
should be examined for signs of injury or illness. I have always
believed that panting in a few birds as the team lands from a training
toss is a good sign. This often means that the team as a whole
is fit and are happy to push as hard as possible to get home. For
these birds, tossing enhances their fitness. The few birds that
are ‘not quite right’ struggle to keep up with them.
These birds should be evaluated to ensure that there is no underlying
disease problem. Healthy but unfit birds will recover quickly in
themselves and their droppings will remain normal. Tossing unwell
birds tends to exacerbate their illness. This means that their
recovery from the training toss will be prolonged and their droppings
may change to green or green and watery. The muscles of birds that
are healthy but worked beyond their fitness capability or of birds
forced to work when unwell are inclined to become bluish and increase
in tone due to cramping.
Panting During Racing
Because panting is the healthy pigeon’s natural way of cooling
itself, panting will be observed in birds during the racing season
when they are hot. This means that healthy birds that are exercised
on hot days will pant. Similarly, it is possible to see birds panting
while resting in the loft during the heat of summer. However, if
during the competitive season a team that has been going well suddenly
starts to pant, this may be an indication of respiratory infection.
This is particularly so if the sudden increase in the amount of
panting is accompanied by a reluctance to fly or other signs of
airway inflammation, such as sneezing. Because by the time racing
has started the birds are older, their natural immunity is already
quite high. As a result their response to disease is considerably
modified. This means it is unusual to see the more obvious signs
of respiratory infection such as a ‘one eye cold’ or
dirty cere. Often all that will be noticed are vague signs of respiratory
tract inflammation such as sneezing and panting. A sudden reluctance
to fly coupled with sneezing and panting warrants a veterinary
The atmosphere in a pigeon transporter provides a particular challenge.
Pigeons have a high body temperature (40.7°C) compared to our
own. With the large number of pigeons confined to the relatively
small area in a race basket, a large amount of heat can be generated
even on a cool day. If the birds become hot, they will pant. In
a well-ventilated transporter where the birds are provided with
water, this is not necessarily a problem. However, if the transporter
is not well ventilated, the moisture evaporating from the bird’s
airsacs creates a humid environment. As the humidity starts to
climb, less and less moisture can evaporate from the airsac surfaces
with the result that the pigeon gradually loses the only ability
it has to keep itself cool. The pigeon therefore starts to overheat.
Unless the pigeon has ready access to water this is quickly accompanied
by dehydration. Experiments have shown that at 25°C, pigeons
will become 5% dehydrated in only 24 hours if deprived of water.
Similarly, experiments have shown if they have access to water
no dehydration will occur even at higher temperatures. In a transporter
that is inadequately ventilated or where birds do not have easy
access to water, the result can be an overheated, dehydrated pigeon
by the time of release. Birds released in this condition can be
expected to orientate poorly and fatigue readily. It is therefore
vital that transporters are adequately ventilated and water is
provided in all races.