The diet of adult psittacids: Veterinarian and ethological approaches

Abstract

Parrots species are kept as pets because of their colours, their vocal abilities, their longevity and also their behaviours. Nevertheless, many owners do not know how to feed their bird in a healthy way and sometimes veterinarians and ethologists are confronted to dramatic situations. Diet is a key factor to prevent and reduce health and psychogenic disorders. Imbalance can lead to physical, physiological and behavioural modifications that can weaken the owner-bird relationship, cause bird discomfort and sometimes threaten its survival. Psittacids are known for their complex cognitive and communicative abilities. They are social animals and need many interactions. Kept in captivity, they could suffer from boredom because of lack of stimulations and also because of lack of possibility to explore and to forage, which could represent up to 70% of their day time in the wild. Indeed, humans control every parameter in the environment of pet psittacids. They provide a highly digestible diet. In captivity, foraging is not mandatory, and the bird can get bored. Here, we present a review of the literature regarding the quality of the diet and health disorders on one hand and the interaction between foraging opportunities and psychogenic disorders in adult psittacids on the other hand.

Full text

REVIEW ARTICLE
The diet of adult psittacids: veterinarian and ethological
approaches
F. P
eron
1
and C. Grosset
2
1 School of Life Sciences Riseholme Campus, University of Lincoln, Lincoln, UK, and
2 Clinique v
et
erinaire de la gare, Taverny, France
Summary
Parrots species are kept as pets because of their colours, their vocal abilities, their longevity and also their behav-
iours. Nevertheless, many owners do not know how to feed their bird in a healthy way and sometimes veterinar-
ians and ethologists are confronted to dramatic situations. Diet is a key factor to prevent and reduce health and
psychogenic disorders. Imbalance can lead to physical, physiological and behavioural modifications that can
weaken the owner–bird relationship, cause bird discomfort and sometimes threaten its survival. Psittacids are
known for their complex cognitive and communicative abilities. They are social animals and need many interac-
tions. Kept in captivity, they could suffer from boredom because of lack of stimulations and also because of lack
of possibility to explore and to forage, which could represent up to 70% of their day time in the wild. Indeed,
humans control every parameter in the environment of pet psittacids. They provide a highly digestible diet. In
captivity, foraging is not mandatory, and the bird can get bored. Here, we present a review of the literature
regarding the quality of the diet and health disorders on one hand and the interaction between foraging opportu-
nities and psychogenic disorders in adult psittacids on the other hand.
Keywords psittacids diet, health prevention, psychogenic disorders, cognition, welfare
Correspondence F. P
eron, School of Life Sciences, Riseholme Campus, University of Lincoln, Lincoln LN22LG, UK. Tel: 0044 (0)1522835474; E-mail:
fperon2008@yahoo.fr
Received: 6 November 2011; accepted: 13 June 2013
Introduction
Over 330 makes up the family Psittacidae, including
parrots, parakeets, parrotlets, macaws, lovebirds, loris,
and lorikeets (Homberger, 2006). The following
review will exclude nectarivore and frugivore species.
Some of these psittacids species are kept as pets and
are seen in exotic animal veterinary practice. Many
people are attracted by these species because of their
physical characteristics and mainly because of their
cognitive and communicative abilities (Pepperberg,
1999; P
eron, 2012). Indeed, they are able to learn and
imitate human words and use them in appropriate sit-
uations (Pepperberg, 1999; Giret et al., 2009, 2010).
They are colourful clowns that use their beak as a
third foot and play most of the time. Parrots and para-
keets represent a new market for food industry and
accessory shops. It is clear that a parrot represents a
great investment in time and money as they live sev-
eral decades. Products offered in shops are quite reas-
suring for people because their bird will like it.
Indeed, psittacids like humans do not select food to
promote health but only to experience pleasure when
consuming it and follow habits (Koutsos et al., 2001;
Kalmar, 2011). Furthermore, the way the food is pro-
vided does not always respect the natural behavioural
repertoire of the animals. Thus, veterinarians and
ethologists face dramatic situations where bird welfare
and sometimes survival are threatened. Hess et al.
(2002) surveyed owners of psittacid birds and found
that several birds had inadequate intakes of vitamin A
and D3 and calcium (when fed with seeds or human
food); excessive fat intake (when fed with seeds) or
low protein and energy intake (when fed with human
food). Manifestation of resulting deficiencies remains
subclinical for prolonged periods of time, and when
clinical symptoms do emerge, they are often unspe-
cific and remain undiagnosed (Wolf et al., 1998). As
the diet influence directly the life span (Munshi-
South and Wilkinson, 2006), here we provided some
elements to improve psittacids’ captive diet and thus
human–bird interactions. After a short review of vet-
erinary knowledge, ethologic results will be pre-
sented.
Journal of Animal Physiology and Animal Nutrition 98 (2014) 403–416 ©2013 Blackwell Verlag GmbH 403
DOI: 10.1111/jpn.12103

Veterinarian perspectives
Feeding of birds is one of the most challenging aspects
of their care, primarily because of limited specific
nutritional experimental studies on each species
(Koutsos et al., 2001; Harrison et al., 2006). Most neo-
tropical parrots inhabit closed-canopy forests, which
renders research on their natural diet very difficult and
incomplete (Gilardi and Munn, 1998). Nutritional sta-
tus of companion birds is known to influence not only
their physical appearance but also their immunity and
reproductive success (Koutsos et al., 2001).
Determination of bird nutrient requirements
Bird nutrient requirements vary depending on spe-
cies, age and physiological status (breeding, mainte-
nance, illness, etc.) (Brue, 1994; Koutsos et al., 2001).
More and more publications about psittacids’ nutri-
tional requirements are available (see Kalmar et al.,
2010b for a review) but because of the extreme diffi-
culty in accurately determining the requirement of all
nutrients, even for a single species, the trace nutrient
requirements established for poultry remain, by
default, as the standard (Koutsos et al., 2001). How-
ever, results to date indicate that the energy, protein
and calcium requirements are lower in psittacine birds
than in poultry (Koutsos et al., 2001). It is now well
established that seed mixes are not a balance diet, and
that improving diet in a short term during moulting or
egg laying is not a good practice (Harrison et al.,
2006). Feeding should be optimal year round. Some
breeders choose the diet depending on the bird prefer-
ences. However, animals do not exhibit ‘nutritional
wisdom’ when selecting dietary ingredients (Koutsos
et al., 2001). For example, egg-laying kakapo hens
select a diet that apparently is deficient in essential
fatty acid even when foods that can meet the require-
ment are available (Body and Powlesland, 1990).
Birds have individual preferences for foods based on
taste, habits, food placement, texture, size, shape and
colour (Brue, 1994; McKenzie and Whittingham,
2010). Avian taste buds are found in much lower
numbers than those of mammals in the oral cavity.
Parrots have been reported to have 350 taste recep-
tors, compared with 9000 in humans (Berkhoudt,
1985). However, studies in cockatiel suggest that their
gustatory abilities depend on the compound being
tested: they appear to be insensitive to three common
sugars (sucrose, fructose and glucose) (Matson et al.,
2000, 2001) but reject salts around the point of osmo-
larity (Matson et al., 2001) and plant secondary com-
pounds (quinine, gramine, tannins) with thresholds
ranging from 0.1 to 10 lM(Matson et al., 2004).
These findings support the hypothesis that cockatiels
use taste to detect, monitor and possibly avoid intake
of potentially toxic compounds. A recent study reports
that even if parrots try to avoid toxic plants, they are
able to cope with it (Gilardi and Toft, 2012). Geoph-
agy–ingestion of clay or charcoal for example–is one
of the defence mechanism against secondary toxic
plant compounds (Burger and Gochfeld, 2003; Mee
et al., 2005) adsorbing potential dietary toxins and
possibly conferring cytoprotection of the gastrointesti-
nal lining (Collar, 1997; Gilardi et al., 1999).
The preferences for some specific type of food (seeds
mainly) can be strong, and some owners encourage
them by providing what the bird is most likely to read-
ily eat. When given the choice, birds often choose
seed mixes (Kalmar et al., 2008a). This type of limited
feeding pattern, like 100% sunflowers or peanuts, can
result in severe deficiency. Providing a large variety of
foods immediately pre- and post-weaning is a very
effective way to develop good eating habits that will
tend to persist throughout life (Brue, 1994).
Imbalanced seed mixes and over-supplementation
There is a general perception that fresh is better. How-
ever, seed mixes (edible part) are not a balanced diet
because they lack vitamin A, D, K, E and calcium, and
they are too rich in fat (Wolf, 2002; Harrison et al.,
2006). Much of the product is sold in its immature
state of growth, and even when matured, it does not
provide the same nutrient profiles as wild seeds. Many
seeds contain appropriate total protein, but lack essen-
tial amino acids like lysine and methionine (Roudy-
bush and Grau, 1985). Determination of specific fatty
acid dietary requirements has been undertaken on
some granivorous species. In contrast to fatty acid pro-
files of commercial grains, fatty acid composition of
wild seeds is characterized by a lack of x-6 fatty acids
(McDonald, 2004a). Even for granivore species, a
standard commercial grain can be considered an
imbalanced diet because seeds from domestic plants
are more concentrated in energy and lower in protein
and many other nutrients than seeds available in the
wild (Klasing, 1998). Formulation of species-specific
seed mixtures is largely based on the size of seeds in
relation to the beak size and on experience as regards
dietary preferences of the species, rather than on spe-
cies-specific nutrient requirements (Kalmar, 2011).
While breeders and owners currently supplement
drinking water with vitamins and minerals, this is
not recommended. Indeed, water intake varies
among species, individuals and is influenced by
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Psittacids nutrition F. P
eron and C. Grosset

environmental temperature and diet (Koutsos et al.,
2001). Some vitamins such as vitamin A and C are
light sensitive (Harrison et al., 2006), and in aqueous
solution, many vitamins are destroyed because of the
high redox potential of minerals, especially iron, zinc
and copper (Koutsos et al., 2001). Moreover, vitamin A
and D toxicoses have been reported as a result of mis-
use of liquid vitamin supplementation in macaws
(Takeshita et al., 1986; Shoemaker et al., 1997), cocka-
toos (Shoemaker et al., 1997), cockatiels (Koutsos
et al., 2001) and conures (Bourke, 1997). Attempts
have been made to correct the nutritional imbalance of
domestic seeds by coating them with supplement. In a
study conducted on African grey parrots, birds were
offered such a diet and they selected mostly a seed diet.
This self-selected diet was shown to be deficient in
twelve vitamins, minerals and amino acids (Ullrey
et al., 1991). When looking at daily intake of dietary
essential amino acids in African grey parrots, while fed
either with a seed mixture diet or with extruded pellets
ad libitum, the authors did not find that amino acids
were deficient in seed-based parrot diets (Kalmar et al.,
2012). Nevertheless, formulated diet is more advisable.
Vitamin D toxicity leads to widespread calcification
of soft tissue. Toxic levels can be transferred mater-
nally to the embryo, leading to abnormalities in chick
development. Vitamin A toxicity may lead to iron
storage disease in cockatiels and lorikeets (Koutsos,
2003; McDonald, 2003a), pancreatitis (Koutsos et al.,
2003; McDonald, 2003a) and vocalization changes
(Koutsos, 2002) in cockatiel. Alternatively, a supply of
carotenoids, like carrot juice or spirulina, instead of
vitamin A, can be provided (McDonald, 2004b). Die-
tary vitamin A requirements have been established to
4000 UI/kg for cockatiel (Harrison et al., 2006).
Excesses of vitamin A may interfere with uptake of
vitamin E, increasing embryonic liver concentration
at the expense of vitamin E, thus compromising the
antioxidant status of progeny. This may decrease fer-
tility, hatchability and survivability of chicks (Koutsos
and Klasing, 2005). On the contrary, high doses of
vitamin E decrease absorption of vitamin A, D and K.
McDonald (2003b) found that it was possible to
improve the health and productivity of large psitta-
cines feeding the birds with organic formulated diets
low in vitamin A.
Carciofi et al. (2003) evaluate the food intake of six
parrots of five different species when fed with a fruit-
and seed-based diet. The authors observed a great var-
iation between individuals in terms of selectivity of
alimentary items but a general trend to prefer seed
over other food items (such as papaya), leading the
diets to be nutritionally heterogeneous and non-
balanced. The average diet consumed presented a
marginal level of protein, high energy, low calcium,
phosphorus and manganese and inadequate calcium/
phosphorus ratio. Another study shows that each co-
nure subject consumed a diet with unique nutritional
characteristics and that the evaluation of the mean
composition of the diet eaten by all birds may result in
an incorrect assumption of what occurs with each bird
individually (Carciofi et al., 2006). When given the
choice, long-billed corellas (Cacatua tenuirostris) pre-
ferred hulled seeds in relation to whole ones, decreas-
ing the general activity linked to deshulling (Waples
et al., 2000). The feeding behaviour of the grey par-
rots and yellow-shouldered amazons (Amazona bar-
badensis) approximately doubled protein content, led
to a three- to four fold increase in fat content and
halved carbohydrate content in relation to the offered
seed mixture diets (Kalmar et al., 2008a). This corrob-
orates with the assertion that, in captivity, given a var-
ied feeding and the possibility of choosing, psittacines
do not present the capacity of nutritionally balancing
their food (Ullrey et al., 1991; Kollias, 1995), render-
ing nutrient ingestion conditioned to the particular
taste of each bird towards the offered foods.
High fat diet with low polyunsaturated fatty acids
predisposes birds to atherosclerosis (Bain, 2012). Birds
fed with dietary omega-3 (fish oil) supplementation
show lower cholesterol and triglycerides in relation to
the group receiving flax oil (Heinze et al., 2012). This
type of diet supplementation can decrease the risk of
developing atherosclerosis. On the contrary, another
type of fatty acid present in seed mixture, a-linolenic
acid (ALA) is thought to be a risk factor for this pathol-
ogy. As the blood concentration of ALA is linked to
the (food) intake, thus this later has to be the lowest
as possible (Bavelaar et al., 2005).
The composition of 30 commercially available parrot
seed mixtures have been analysed and compared to de-
hulled seeds (as parrots remove this part) and several
commercial diets. The results revealed that most parrot
species are fed a diet rich in fat and energy, and that
the energy density of most formulated, pelleted/
extruded diets is far below the energy density of com-
mon seed mixtures (Werquin et al., 2005). This type of
unbalanced diet increases the catabolism of amino
acids and leads to an increase of ketone body formation
in psittacine birds (Kalmar et al., 2010e) that could
lead to metabolism modification such as acidosis.
Seed mixes diet and multisystemic abnormalities
Birds offered seeds alone tend to have a higher body
condition score. Obesity has been defined as a body
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F. P
eron and C. Grosset Psittacids nutrition

weight in excess of optimal body weight >20% (Harri-
son et al., 2006). The basal metabolic rate (BMR) of
psittacine birds depends upon the thermal climate of
the species origin (Koutsos et al., 2001). According to
McNab and Salisbury studies (1995), species originat-
ing from tropical climates have a BMR (kJ/
day) =4.184 973.6 9(body weight in kg)
0.73
,
whereas species originating from temperate climate of
New Zealand and Australia have a 21% higher basal
metabolic rate (McNab and Salisbury, 1995). The reg-
ulation of food intake is not always perfect, and obes-
ity can result when diets with high energy density are
fed. For instance, budgerigars fed a 13 MJ/kg of
metabolizable energy were able to maintain their
body weight, whereas those fed a 14 MJ/kg became
obese (Drepper et al., 1988). In sedentary pet birds,
overweight may be associated with pododermatitis,
higher oxidative damages while performing an escape
flight (Larcombe et al., 2010). This condition may pre-
dispose a bird to congestive heart failure, atherosclero-
sis, fatty liver and kidney disease and diabetes,
although this condition is rare in psittacids (Murphy,
1992; Desmarchelier and Langlois, 2008). Deficiency
of cysteine and methionine also predisposes to fatty
liver syndrome (Harrison et al., 2006). In a study, a
seed-based diet with 12.8% protein that was low in
lysine resulted in increased body fat. However, the
same diet supplemented with lysine was adequate to
maintain weight and body composition in budgerigars
(Underwood et al., 1991). So amino acid deficiencies
of seed mix diets could also be responsible for obesity.
A study was conducted in budgerigars to compare
haematological and biochemical parameters of two
groups of birds fed either on seed mixture diet or on
commercially formulated diet during 1 year (Fischer
et al., 2006). The authors did not notice any differ-
ence regarding the haematological parameters. The
group fed the seed mixture had significantly higher
concentrations of glucose, albumin, triglycerides and
uric acid and higher activity of aspartate aminotrans-
ferase, but the values were within the published refer-
ence ranges for normal birds.
Vitamin A is critical for vision, cellular differentia-
tion and immune function (Koutsos et al., 2001).
Hypovitaminosis A typically leads to keratinization of
squamous cells (Koutsos et al., 2001). This is corre-
lated with hyperkeratosis on the footpad and the plan-
tar surface of the toes, leading to pododermatitis.
Keratinization of the excretory ducts of uropygial
gland results in impaction of this gland and predis-
poses to abscess formation (Harrison et al., 2006). In
parrots, focal metaplasia of the excretory duct of the
glandular epithelium of the salivary gland was identi-
fied when liver vitamin A levels reached extremely
low levels (<50 IU/g liver) (Dorrestein et al., 1987).
Clinical signs involving integumentary system also
manifest as overgrowth of the beak and the nails. Epi-
thelial metaplasia may predispose to dermatological,
respiratory and kidney diseases (Harrison et al., 2006).
Reproductive success also greatly depends on the nutri-
tional status of breeders and chicks. Seeds decrease
reproductive performance because they lack calcium,
lysine, vitamin A and E. Vitamin A deficiencies are
correlated with increased time between clutches,
reduced hatchability, increased embryonic mortality,
decrease survival time of progeny, decreased testes
size, failure of spermatogenesis and a decline in sexual
activity in males (Zhengwei et al., 2000). If a breeder
is fed a nutrient-deficient diet, embryo development
may be affected by early embryonic death or devel-
oped poor feathering, facial dermatitis and reduced
body weight (Koutsos and Klasing, 2005).
Blood calcium levels in birds depend on dietary cal-
cium and vitamin D3 levels (Stanford, 2006). Some
species also rely on UV B, which enable the bird to
convert vitamin D2 into vitamin D3 (Stanford, 2006).
In an experiment, African grey parrots were divided
into two groups receiving either a formulated nugget
diet or a seed mix. Nugget diet produced a statistically
significant increase in both the ionized calcium levels
and the 25-hydroxycholecalciferol levels over the
seed-fed group, even if both groups received the same
amount of UVb (Stanford, 2003). Improved breeding
performances were also observed in the nugget-fed
group. Calcium deficiency may lead to egg binding in
laying birds. Additionally, calcium-deficient parents
may give birth to osteodystrophic juveniles (Harcourt-
Brown, 2003; Stanford, 2006). Clinical evidence indi-
cates that calcium (Ca) requirement for maintenance
is probably above 0.05% (Wolf et al., 1998). Most
seeds commonly fed captive parrots have <0.1% Ca,
and grains such as millet and corn, are especially low
with <0.03% Ca. In addition, seeds can contain high
levels of phosphorus (P), which can bind the calcium
in phytate complexes (Stanford, 2006). Seeds there-
fore do not meet calcium requirements of psittacids.
Suboptimal Ca supply and Ca/P ratio when fed seed-
based diets are a well-known cause of impaired skele-
tal mineralization and are consistent with clinical pre-
sentation in practice (Wolf et al., 1998). Calcium
enters in muscle contraction and its mobilization is
important for egg laying in female. Deficiency could
lead to nutritional secondary hyperparathyroidism
(Wallach and Flieg, 1967), rachitis or osteomalacia
(Kalmar, 2011). The optimal range of Ca/P ratio is
between 2:1 and 1.5:1 (Wolf, 2002). Hypovitaminosis
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Psittacids nutrition F. P
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A, D3 toxicity and excess of dietary calcium could lead
to chronic kidney diseases (Bain, 2012). It seems that
birds do not select food based on potentially limiting
minerals including sodium and calcium but select high
value nutrition food: seeds (Gilardi and Toft, 2012). It
is possible to supplement the seed diet with oyster
shells or cuttlefish bone to increase the quantity of
calcium intake.
In the wild, some psittacine birds time their breed-
ing to the seasonal availability of higher protein foods,
indicating that amino acid nutrition is a major deter-
minant of reproductive output (Wilson et al., 1998;
Houston et al., 2007). In captivity, cockatiels increase
egg lay after protein content of the diet increases
(Koutsos et al., 2001). In general, avian species are
unable to synthesize the essential amino acids leucine,
threonine, lysine, tryptophane, phenylalanine, valine,
methionine and isoleucine (Koutsos et al., 2001). A
requirement for glycine has been observed for the
budgerigar, suggesting that psittacine birds are unable
to synthesize enough glycine to meet metabolic
demands (Taylor et al., 1994). The lysine requirement
of cockatiel chicks from hatching to weaning was
found to be 0.8% of the dry portion of diet (Roudy-
bush and Grau, 1985). This high requirement is not
met by seeds alone. Chicks fed with a lower rate of
lysine achieve slower growth (Roudybush and Grau,
1985). However, on the contrary to poultry, lysine
deficiency did not result in a lack of melanin pigment
in feather pigmentation of psittacine chicks (Roudy-
bush and Grau, 1985). Amino acid deficiency is mani-
fested in reduced growth rates (Klasing, 1998) and
anorexia (Koutsos et al., 2001). Adult cockatiel fed
70% crude protein for 11 months were able to main-
tain general conditioning without post-mortem renal
abnormality in an experimental study (Koutsos et al.,
2001). So, the role of high levels of dietary protein in
gout of psittacine birds is not supported by experimen-
tal evidence, at least in cockatiels. However, sudden
changes from low- to high-protein diets should be
gradual because sudden changes might lead to hyper-
ammonemia, elevated uric acid production and poten-
tially nephritis and gout, especially in young birds
(Koutsos et al., 2001). At the opposite, the supple-
mentary feeding influences also the reproduction. For
instance, in kakapo, supplementary feeding (high
energy diet) causes a male-biased offspring sex ratio
(Clout et al., 2002).
Immunity is also influenced by the nutritional status
of the bird. Both deficiency and excess of dietary
vitamin A suppress immune function (Koutsos and
Klasing, 2005). In cockatiels, vitamin A deficiency
may be associated with diarrhoea and pneumonia by
impairing intestinal IgA response (Koutsos et al.,
2003).
Current recommendations
Recommendation for psittacins is to provide each bird
with 20% fruits and vegetables and 80% pellets (Reid
and Perlberg, 1998). Kalmar (2011) and Slooten
(2012) provide recent recommendations (review and
new data) regarding the different nutritional require-
ment (protein, energy, vitamins, fat, etc.) of psitaccids
bird. Commercial diets are formulated for different
physiologic status. (Harrison et al., 2006). Energy
requirement (kJ/kg diet) increases for hatchlings,
whose growth is rapid, and for females a few days
prior to egg production until the clutch is laid (Klas-
ing, 1998). Usually, two different diets can be offered
to accommodate these changing needs: a grower-
breeder diet and a maintenance diet (Koutsos et al.,
2001). In eight psittacin species, a study demonstrated
that fledging success was greater when a pelleted diet
was fed in place of seeds (90% success vs. 66%) (Ull-
rey et al., 1991). Moult may not be associated with
change in diet formulation because increase in food
consumption to meet energy requirements results in
sufficiently increased amino acid intake: the percent-
age increase in the energy expenditure associated with
moult often exceeds the percentage increase in
protein needed (Murphy, 1996).
The heating of nutrients enhances their digestibility,
making them more appropriate for geriatric and juve-
nile patients. This also provides more energy and
nutrients to birds suffering from maldigestion caused
by proventricular dilatation disease or by pancreatitis
(Clubb, 2009). Some diets are compounded of organic
food but there is no proof that is. It has been shown
that some birds choose conventional seeds when
given the choice (in relation to organic food). This
could be explained either because conventional seeds
have a higher protein rate or because of the animals’
previous feeding habits (McKenzie and Whittingham,
2010). Different kinds of cooking processes are also
available: pelletizing and extrusion. In the extrusion
process, raw materials are ground to smaller particle
size. The dry mix is passed through a preconditioner,
where other ingredients are added, steam is also
injected to start the cooking process. The precondi-
tioned mix is then passed through an extruder and
then forced through a die where it is cut to the desired
length. Use of the extrusion cooking process (approxi-
mately 140 °C; Frame, 1994) induces protein denatur-
ation, leading to inactivation of enzymes, and
destruction of naturally occurring toxins (Riaz, 2000).
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This high digestibility makes it advisable for birds suf-
fering from diseases leading to maldigestion like prov-
entricular dilatation disease. This process of extrusion
creates starch gelatinization but also Maillard products
and fat hydrogenation among other things. A recent
study showed that lower degree of starch gelatiniza-
tion in extruded diets enhance digestibility in pigeons
(Abd El-Khalek et al., 2011). Maillard products
reduce the availability of amino acids, and fat hydro-
genation leads to high level of fatty acids, which
could increase the risk of atherosclerosis. The process
decreases the number of micro-organisms (Riaz,
2000). This improves the safety of the final product
but also inactivates probiotics. In the pelletizing pro-
cess, feed ingredients are hammered to reduce the
particle size. Ingredients are then batched, combined
and mixed thoroughly by a feed mixer. Feed is condi-
tioned and thermal treated (low temperature) in the
fitted conditioners of a pellet mill. The feed is then
pushed through the holes and a pellet die and exit
the pellet mill as pelleted feed. Finally pellets are
cooled. This process enables to spare probiotics.
Cooking (roasting, pelletizing or extrusion) is
designed to stabilize oils. However, depending on the
lipase concentration in some seeds, like brown rice
and oats, rancidity can occur. These ingredients need
to be roasted or partially cooked separately, then
mixed to other ingredients prior to final processing
(Harrison et al., 2006). Overcooking is also associated
with degradation of some nutrients and conversion
of cis to trans fatty acids (Harrison et al., 2006). For-
mulation of commercial diet should include enough
antioxidants such as vitamin E, A, C and carotenoids.
Antioxidants help to counter the detrimental effects
of oxygen-free radicals implicated in the development
of cancer, inflammatory conditions and heart disease
(Harrison et al., 2006). Antioxidants could be advis-
able for weaker birds (Larcombe et al., 2010).
Studies with captive adult parrots (Psittaciformes)
indicate that particle size and the degree of starch gela-
tinization are important parameters of the diet, relating
directly to the health and function of the intestinal
tract (Janssens et al., 2004; Kalmar et al., 2007). Three
hand-rearing formulas with identical nutrient compo-
sition but different native starch content and particle
size as a result of applied processing conditions were
used in the study on the growth of parrot chicks of the
genus Amazona (Reinold et al., 2012). The authors
find that diets with more native starch (bigger particle
sizes) tend to have a positive effect on intestinal health
and function of Amazon parrot chicks.
Finally, packaging impacts the quality for a com-
mercial diet (Brennan, 2006) as it has to prevent
exposure to light and oxygen to slow down auto-oxi-
dation of fatty acids and triglycerides. That is why
cardboard and paper boxes are not adequate, but at
the same time soft plastics may act as phytoestrogens
(Harrison et al., 2006). Even with adequate products,
all food should be smelt when first opened to check it
is not rancid (Harrison et al., 2006). Following these
precautions, commercial diets are recommended to
keep a companion bird healthy. A main advantage of
pelleted diets over seed-based diets includes preven-
tion of selective feeding behaviour.
Ethological perspectives
Consequences of captivity on bird diet
Feeding behaviour of birds represents a way to esti-
mate parrots’ health and welfare. Owners and breed-
ers can observe either on: (i) overconsumption due to
pharmacological treatment, behavioural disorders or
just inadequate diet; or on the contrary; (ii) anorexia
that could appear when food is not adapted or fresh
enough (for fruit and vegetables), the bird has health
problems (such as cardiac disease) or receive a treat-
ment (for a review, see Bain, 2012). Controlling the
diet and increasing the general activity would reduce
risk factors of health problems. The diet of parrots
influences their life span: granivorous, big parrots
with communal roasting and periodic resource short-
ages live longer. The caloric restriction linked with the
activity and the spare resources increases the life span
(Munshi-South and Wilkinson, 2006).
Captivity imposes constraints on the expression of
the normal behavioural repertoire. We can observe
abnormal behaviour traducing an attempt to cope
with adverse environment such as lack of space or
social instability (Broom, 1991; Danzer, 1991). In gen-
eral, psittacids, as other prey animals, are neophobic
(Wilson and Luescher, 2006), and they tend to avoid
new food items. The likelihood of neophobia or reluc-
tance to novel food items is influenced by the extent
of environmental enrichment in early life (Fox and
Millam, 2007). In the wild, individuals can eavesdrop
conspecifics, but in captivity, owners have to play this
role. Studies on language learning show that Model/
Rival method can help in the learning process as birds
tend to compete for reward (Pepperberg, 1999) but
also mimic the ‘model’ behaviour (vocal responses).
Secondly, birds are programmed for important ener-
getic cost for their daily life while foraging, defending
their territory, breeding or escaping predator attacks
for instance. In the wild, birds spend 90% of their
active daytime foraging and preening (self and allop-
reening) (Engebretson, 2006). As this natural foraging
Journal of Animal Physiology and Animal Nutrition ©2013 Blackwell Verlag GmbH408
Psittacids nutrition F. P
eron and C. Grosset

behaviour is time consuming, birds have to eat ener-
getic food and tend to favour protein and fat. The
same is observed in captivity but in this situation,
energetic expenditures are very limited because pet
birds tend to be sedentary leading to obesity. In cap-
tivity, humans control food availability, variety,
quantity and quality. Other factors can also influence
food intake mainly indirectly when the general activ-
ity is modified because of the temperature, light/dark
cycle or sexual status (e.g. courtship behaviour;
Schnegg et al., 2007). On the contrary, the diet itself
could influence the behaviour. The nesting behav-
iour of kakas, similar to kakapos, is synchronized to
the abundance of specific food items for instance
(Wilson et al., 1998; Houston et al., 2007). Snyder
et al. (1987) documented that Puerto Rican Amazon
parrots (Amazona vittata) spend approximately 4–6h
per day foraging across sites that could be distant
from several miles. It is presumed that other psitta-
cine species spend similar amounts of time searching
for and acquiring food as part of their daily behavio-
ural repertoire. In contrast, companion birds (captive)
such as orange-winged Amazons (Amazona amazo-
nica), spend approximately 30–72 min per day eating
a pelleted diet (Oviatt and Millam, 1997) without
travelling, manipulating food items (podomandibula-
tion) or attempting to balance their own diet (Mee-
han et al., 2003b). Furthermore, the reduction in or
even omission of the appetitive phase (foraging per-
iod) reduces the diversity of the parrots’ behavioural
repertoire (Kalmar, 2011).
In the wild, parrots fed on a huge variety of food
such as seeds, fruits, flowers, leaves, bark or insect lar-
vae. The study of Gilardi and Toft (2012) on 17 differ-
ent species (of eight genera) living in Peruvian
amazon revealed that their diet is diverse even if the
seeds represent 70% of the food intake. This flexibility
enables the birds to reduce the competition between
individuals and species and also to adapt to the sea-
sonal variation and other factors that could impact on
the foraging areas. The same flexibility and diversity
in the diet and feeding behaviour has been observed
in several different species in other countries and con-
tinents: see, for example Best, 1984 (Strigops habropti-
lus); Galeti, 1993 (Pionus maximiliani); Garnett and
Crowley, 1995 (Psephotus dissimilis); Renton, 2001
(Amazona finschi); Symes and Perrin, 2003 (Poicephalus
fuscicollis suahelicus).
Even when bred in captivity, exotic parrots are not
considered domesticated animals and, as such, they
retain the inherent behavioural and physical needs of
wild parrots (Davis, 1998; Graham, 1998). For
instance, their natural behaviour facing an apparent
danger will be to fly away but most of the time they
cannot (lack of space, deflighting method), and we
can observe a redirection of the arousal that leads to
decreased anxiety due to the stress (Jenkins, 1999).
Moreover, psychogenic disorders can appear because
the behavioural repertoire cannot be displayed nor-
mally. Secondly, the bird is often housed alone and
tends to suffer from boredom. It has been suggested
that the denial of these activities (social interactions
and foraging) can cause both physical (Graham, 1998)
and behavioural abnormalities in captive parrots (van
Hoek and ten Cate, 1998; Garner et al., 2003b; Mee-
han et al., 2003a,b, 2004). The size of the cage and
the general activity represent the main (physical) con-
strains linked to the captivity and could lead to
feather-damaging behaviour (Seibert, 2006; Van
Zeeland et al., 2009). Oral stereotypy (e.g. feather
picking, bar chewing) is related to lack of opportunity
to perform foraging behaviour. Lack of social interac-
tion with the same species appears to contribute to the
development of both oral and locomotor stereotypy
(Sargent and Keiper, 1967; Keiper, 1969; Meehan
et al., 2003a,b, 2004). Garner et al. (2003b) showed
that stereotypy in captive orange-winged Amazon
parrots (Amazona amazonica) is correlated with poor
performance on a cognitive task (the ‘gambling task’).
The extent to which animals are positively or nega-
tively affected by their captive environments is likely
to depend on their cognitive abilities as well (Held
et al., 2001). Parrots have been shown to have high-
level cognitive abilities (Pepperberg, 1999; P
eron,
2012). These abilities may be an important factor on
parrots’ susceptibility to develop abnormal behaviour
in captivity (Birchall, 1990). In captivity, feeding time
is short thus boredom and ‘redirected foraging’ result-
ing from lack of foraging opportunities (e.g. Meehan
et al., 2003a,b; Lumeij and Hommers, 2008) can be
observed. Plucking Crimson-bellied Conures (Pyrrhura
perlata perlata) spend more time preening and are less
active, spending less time flying and vocalizing (van
Hoeck and King, 1997). In the same study, the sever-
ity of feather damages was correlated with the time
spent preening. It was also shown that adding fruit
basket and willow branches of different sizes
increases exploration such as flying, hopping and
climbing, and also manipulation with both foot and
beak that competes with other activities such as
preening or vocalizations. The experimenter observed
a stabilization of the picking problem following this
environmental enrichment (van Hoeck and King,
1997). Thus, it seems that oral activity with edible
food or material is the expression of a natural behav-
iour for birds.
Journal of Animal Physiology and Animal Nutrition ©2013 Blackwell Verlag GmbH 409
F. P
eron and C. Grosset Psittacids nutrition

Consequences of inappropriate diet on bird cognition
We have seen in the first part that imbalanced diet
could impact general health. Regarding ethological
aspects, birds kept on inappropriate diet can also exhi-
bit behavioural modifications such as voice change,
aggressiveness or apathy, which can be observed by
the owner. The diet can directly impact on sexual dis-
play. The beginning of reproductive season could be
influenced by modification of food quantity and qual-
ity (Perrins, 1970).
In other avian species, carotenoid supply can mod-
ify sexually selected colour signals. However, psittacin
birds use psittacofulvin pigments instead of carotenoid
pigments in their plumage. Therefore, diet does not
seem to influence their colour (Knott et al., 2010).
Despite lack of effects of dietary carotenoids on nor-
mal feather coloration, chronic malnutrition can
induce aberrant feather pigmentation (Koski, 2002).
Moreover, a typical indication of malnutrition, or
even a period of impaired health, includes the pres-
ence of stress marks–horizontal, linear defects across
the vane–at the feathers (Harcourt-Brown, 2000). It
has been demonstrated that carotenoid content of the
diet has an impact on avian oil droplets, located in ret-
inal cones (Knott et al., 2010). A change in avian oil
droplets’ composition was observed after 2 months on
carotenoid-free diet (Knott et al., 2010). It is therefore
likely that a diet lacking carotenoids can modify
colour vision in birds, therefore impacting their
behaviour.
van Hierden et al. (2005) also found that supple-
mentation with serotonin precursor tryptophan might
improve feather picking in some cases. However, pre-
vious experiments in which specific amino acid defi-
ciencies have been induced have not indicated
increased behavioural disorders such as feather pick-
ing (Klasing, 1998). Vitamin A can lead to epithelial
squamous metaplasia and subsequent behavioural dis-
orders such as feather picking. Other minerals such as
selenium also play a role in skin quality. It has been
shown that cockatiels fed 100 000 IU vitamin A/kg
diet had increased numbers of vocalizations in relation
to an adequate vitamin level of 2000 IU/kg (Koutsos,
2002). However, whether or not this indicates cogni-
tive disorder remains to be determined.
Does obesity lead to cognitive impairment in birds?
In mice, scientists have strong evidence that high fat
diet impairs cognition (and increases brain inflamma-
tion) (Pistell et al., 2010). Triglycerides are a major
cause of cognitive disturbances in diet-induced obesity
(Farr et al., 2008). In humans too, obesity has adverse
effects on cognitive performances (Elias et al., 2005).
In psittacids, whether or not obesity impacts cognitive
abilities remains to be determined. On the contrary,
deficit in high-quality fatty acid could lead also to
some cognitive impairment. For instance, kittiwakes
chicks fed with lipid-poor fishes have lower perfor-
mances in cognitive task (Kitaysky et al., 2006) when
compared to other birds fed with lipid-rich fishes.
Omega-3 fatty acids are known to have a positive
impact on health and cognition. Docosahexaenoic
acid (DHA) is a long-chain polyunsaturated fatty acid,
within the omega-3 family, which has been demon-
strated to play an essential role in brain development
in several species. DHA also impacts cognitive func-
tion because of its involvement in synaptic plasticity,
neurotransmission, neurogenesis and its protective
properties against oxidative damage to brain lipids and
membranes that could cause loss of cognitive or motor
skills (for review see Callicrate et al., 2011). A recent
study conducted on budgerigars suggests that Docosa-
hexaenoic acid (DHA) dietary supplementation (Calli-
crate et al., 2011) do not impact on birds’ behaviour
even if the authors do not know whether the quantity
or the absorption were correct.
Food quality but also food distribution can predis-
pose to behavioural disorders. Studies by Harcourt-
Brown (2004) suggested that premature physical
activity in hand-reared chicks may exacerbate the
effects of a deficient diet and contribute to skeletal
deformity. Furthermore, hand-rearing has the poten-
tial to produce physical as well as behavioural prob-
lems in parrots (Harcourt-Brown, 2004). In another
study, lead on passerines, canaries that were forced to
work for food compared to those which had free
access to food also showed a reduction in stereotypic
behaviour such as spot-picking (Keiper, 1969).
Furthermore, environmental enrichment can lead
to better performances in cognitive tasks as it has been
observed with chickens: the enrich group (with the
opportunity to explore an outdoor free-range 1 week
prior to the experiment) learnt the task faster(Krause
et al., 2006). Tested with a Y-maze task, the enriched
group left the start-box faster and was better in learn-
ing the task and made fewer initial mistakes. Garner
et al. (2003a) already revealed that stereotyping birds
display had poor results on a cognitive task. Neverthe-
less, to our knowledge, no study addressed the ques-
tion of potential benefits of enriched environment on
cognitive performances.
The diet as a way to enrich birds’ housing conditions
Following the last paragraphs, it seems logical to assess
that improving diet can be a way to prevent some
Journal of Animal Physiology and Animal Nutrition ©2013 Blackwell Verlag GmbH410
Psittacids nutrition F. P
eron and C. Grosset

behavioural disorders. In feeding trials with amazons,
grey parrots and cockatoos, Wolf et al. (2002) noticed
that the feeding pattern but not time spent for feed
intake differed between pelleted/extruded diets and
seed mixtures. A typical rhythm of feed intake was
observed while offering seed mixtures ad libitum
(higher ingesting activities in the early morning and
in the afternoon), whereas formulated diets were
ingested continuously during the whole day. Compar-
ing the food intake and the budget time of rose-ringed
parakeets (Psittacula krameri) feeding on either a
extruded pellet diet or sunflower seeds ad libitum, the
authors did not observe overfeeding in the pellet diet
group even if their food intake was higher (Kalmar
et al., 2010a). The same had been observed with grey
parrots while fed either on a seed diet or on a pellet
diet: their daily water and food intake was increased
in the second situation (Kalmar et al., 2010d). Never-
theless, the voluntary energy intake was lower for the
pellet diet group because of the energetic density of
the food (compared to sunflower seeds) (Kalmar
et al., 2010a). This indicates that the use of balanced
foods, pelleted or extruded, tested with success by
authors such as Roudybush et al. (1984) and Ullrey
et al. (1991), is an important path to be considered in
improving the nutrition of parrots in captivity. De-
husking seeds leads to an important increase in fat
and protein content on account of a decline in crude
fibre content (Kalmar et al., 2008b). Kalmar et al.
(2010c) observed that providing apple to the amazons
significantly lowered voluntary energy intake in birds
by approximately 1/8.
Providing food items of different sizes and when
possible in a very raw and natural form, such as non-
peeled pellets, increases beak and tongue manipula-
tion and oral activity, foot handling is thought to
improve bird coordination and helps to maintain body
condition. In a study, over-sized pellets (20–30 times
larger) were preferred in captive orange-winged par-
rots (Amazona amazonica) compared to regular size
because it increased the oral activity and provided
enrichment foraging (Rozek et al., 2010). Moreover,
birds were motivated to work in order to reach larger-
sized pellet manipulating weighted-lid feeders even
when regular pellets were freely available (Rozek and
Millam, 2011). Then it seems that captive parrots dis-
play contrafreeloading–animals will work for a
reward, in the presence of the same reward available
freely (Elson and Marples, 2001; Van Zeeland et al.,
2010).
Food provisioning should be realized at all times
and not only when the owner is present. Owners have
to make their bird as independent as possible, as it will
feel less bored when left alone. Of course, part of the
diet could be distributed when the owner is present to
maintain the relation, and this moment can also be
associated to medical training or behavioural modifi-
cation sessions as a reward. Hand-reared birds are sen-
sitive to food quantities and develop expectation
when they see humans manipulating food. They are
sensitive to their owner intention, such as teasing for
instance (P
eron et al., 2010) and can be aggressive
when they feel frustrated, so owners should only use
favourite food to work with their bird and should
never starve it.
It has been demonstrated that it is possible to pre-
vent and reduce behavioural disorders such as feather
picking or stereotypies using physical and foraging
enrichments (Meehan et al., 2003b). The general idea
is to add elements in the environment so that a bird
has to chew through barriers, manipulate objects
through holes, sort through inedible material or open
containers to obtain food items. In this study, the
authors observed that foraging enrichment is more
used compared with physical enrichment, which
means that podomandibulation activity seemed to be
compulsory. Thus, simply using a pipe feeder rather
than a bowl to distribute the diet increases foraging
time and improve feather picking score (Lumeij and
Hommers, 2008) because the new activities enter in
competition in the time budget.
Foraging material can be used to increase activity.
Owners should try to dispense food, for example using
shavings of wood. Food items should be placed in dif-
ferent areas,which are difficult to access like hung up
toys that the bird could try to manipulate and destroy.
Thus, enrichment programs create a competition in
motivation, time budget and physical activities so that
animals tend to be in better mental health as they can
express their natural behaviour (Meehan et al.,
2003b). Thus, the diet represents a way to increase
environmental enrichment as several modalities are
involved in foraging such as tactile, visual, olfactory
and gustatory senses. In budgerigars (Melopsittacus un-
dulatus), placing the feeder as far as possible under
perch level increases bird activity: budgerigars come
and feed more often but spend less time on the feeder
because a lower position makes them more exposed to
potential predators (Schnegg et al., 2007). Parrots feel
sensory pleasure with food and are able to express it
(Cabanac, 2009) or to ask for specific food (Pepper-
berg, 1998; P
eron, in press). This ability could then
take part in the foraging decision (favouring fat) but
can be used also in the enrichment programme as a
way to motivate the bird. Furthermore, offering of
fruit next to a seed-based diet effectively reduces
Journal of Animal Physiology and Animal Nutrition ©2013 Blackwell Verlag GmbH 411
F. P
eron and C. Grosset Psittacids nutrition

voluntary energy intake and can hence be applied to
abate obesity (Kalmar et al., 2010c).
Parrots in captivity spend significantly less time in
feeding and foraging activity and more in resting and
maintenance behaviours than parrots in the wild.
Food-based enrichment devices can be used to
increase the levels of activity of captive parrots:
increasing foraging and locomotor activities and on
the contrary decreasing resting periods–that could
lead to boredom–and maintenance behaviours–that
could lead to feather-damaging behaviour–(Van Zee-
land et al., 2009). Species-specific enrichments,
designed to bring out wild-type behaviour, have a
greater attraction for parrots than devices, which are
less species specific (Elson and Marples, 2001).
Conclusion
To conclude, if owners want to improve the relation
with their ‘feathered apes’ they should take care of
their diet. Food quality and normal behavioural rep-
ertoire expression help the bird to be in good mental
and physical health. Because parrots tend to select
the food they preferred (over the food that could be
the healthiest) and also because they dehull the
seeds, we observed most of the time that their diet is
unbalanced. Formulated diet seemed to be one of
the best ways to feed these birds. Increasing the for-
aging time is also a good way to control the activity
of the bird and to prevent some physiological and
behavioural disorders. Even though the number of
publications on psittacids nutritional requirement
has increased over the last few years the data come
from very few different species. In the future, it
could be interesting to determine whether diet can
improve cognitive processes in birds such as solving
tasks and learning tricks.
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