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JERSEY WILDLIFE PRESERVATION TRUST ST LUCIA PARROT FOOD CONSUMPTION AND PREFERENCES 199 Int. Zoo Yb. (1998) 36 199-214 0 The Zoological Society of London Individual variation in food consumption and food preferences in St Lucia parrots at Jersey Wildlife Preservation Trust Amazona versicolor J. E. FA & M. L. CAVALHEIRO International Training Centre, Jersey Wildlife Preservation Trust, Les Augr2s Manor, Trinity, Jersey JE3 5BP, United Kingdom Individual food consumption and food item prefer- ence of 12 St Lucia parrots Amuionu vrrsicolor were studied at Jersey Wildlife Preservation Trust. Diet offered contained a maximum of 29 foods, mostly fruits, vegetables and pulses but also processed foods and commercial parrot pellets. Each day all birds were presented with the same selection of foods and no novel items were introduced during the study period. Birds varied in their average food intake per feeding session (mean SD) from 15.1 & 5.6 g kg- to 89.0& 138.3 g kg-’. Diversity of food items eaten per session was determined by the Simpson’s index of diversity. Food preferences were measured by Ivlev’s electivity indices from the total amount of each food type consumed relative to the total amount of that food type offered during all sessions. Foods were classified as ‘disliked’ when electivity indices were negative and ‘rejected’ if not consumed at all. The order in which food types were consumed by each parrot was also analysed. Results showed that diet diversity and food intake were significantly higher for 97 than 83. Wild-born parrots consumed less but ate a wider variety of foods than captive- born ones. Significant sexual differences in overall food intake as well as in the percentage of disliked and rejected foods were found among captive-born birds but not in wild-born parrots. However, because all wild-born birds in the present study were twice as old as the captive-born ones, age of bird and origin were confounded variables. Older birds dis- liked less foods than younger ones but younger par- rots ate more than older birds. Within paired birds, ?? were more aggressive towards JJ than vice versa. This may have influenced the lower feeding levels observed by subordinate JJ but single JJ ate even less than those kept in pairs. The results of this study suggest that it is not possible to make generalizations to satisfy optimal diet requirements of the species because of the considerable individual variation found. Quantifying intake and preference from direct observations of the birds during feeding can be a useful technique to help with the formulation of diets. Further studies are required to determine the roles of sex, age and origin on food consumption and preference. The behaviour of paired and single birds should also be assessed in order to identify suit- able methods for feeding dominant and subordinate birds in an attempt to optimize nutritional intake of each individual. Key-words: aggression, direct-observation sampling, food intake, food preferences, nutrition, St Lucia parrots Formulating diets for captive birds poses considerable challenges because nutrient requirements need to be adjusted according to age, activity and reproduc- tive status of the animals (Alderton, 1986). Most zoos achieve this by pro- viding a nutritionally complete manu- factured diet in order to protect the birds from fluctuations in food nutrient con- tents and nutrient loisses caused by storage and preparation. Although manufactured diets are convenient, natural diets have benefits for the animal beyond nutrition by meeting psychological and behavioural needs as well as physiological ones. Furthermore, if c,aptive-breeding pro- grammes are to propagate species for reintroduction, naiural diets provide animals with the opportunity to manipu- late food items and examine texture, shape and colour of foods in preparation for living in a wild habitat. Researchers who have attempted to quantify the diets ol’ birds in captivity to date have used estimates of consumption based on ‘food offered’ to ‘food left over’ ratios (Ullrey et al., 1991). Although this method may provide some approxima-

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Page 1: Individual variation in food consumption and food preferences in St Lucia parrots Amazona versicolor at Jersey Wildlife Preservation Trust

JERSEY WILDLIFE PRESERVATION TRUST ST LUCIA PARROT FOOD CONSUMPTION AND PREFERENCES 199

Int. Zoo Yb. (1998) 3 6 199-214 0 The Zoological Society of London

Individual variation in food consumption and food preferences in St Lucia parrots

at Jersey Wildlife Preservation Trust Amazona versicolor

J. E. FA & M. L. CAVALHEIRO International Training Centre, Jersey Wildlife Preservation Trust, Les Augr2s Manor, Trinity, Jersey JE3 5BP, United Kingdom

Individual food consumption and food item prefer- ence of 12 St Lucia parrots Amuionu vrrsicolor were studied at Jersey Wildlife Preservation Trust. Diet offered contained a maximum of 29 foods, mostly fruits, vegetables and pulses but also processed foods and commercial parrot pellets. Each day all birds were presented with the same selection of foods and no novel items were introduced during the study period. Birds varied in their average food intake per feeding session (mean SD) from 15.1 & 5.6 g kg- to 89.0& 138.3 g kg-’. Diversity of food items eaten per session was determined by the Simpson’s index of diversity. Food preferences were measured by Ivlev’s electivity indices from the total amount of each food type consumed relative to the total amount of that food type offered during all sessions. Foods were classified as ‘disliked’ when electivity indices were negative and ‘rejected’ if not consumed at all. The order in which food types were consumed by each parrot was also analysed. Results showed that diet diversity and food intake were significantly higher for 97 than 83. Wild-born parrots consumed less but ate a wider variety of foods than captive- born ones. Significant sexual differences in overall food intake as well as in the percentage of disliked and rejected foods were found among captive-born birds but not in wild-born parrots. However, because all wild-born birds in the present study were twice as old as the captive-born ones, age of bird and origin were confounded variables. Older birds dis- liked less foods than younger ones but younger par- rots ate more than older birds. Within paired birds, ?? were more aggressive towards JJ than vice versa. This may have influenced the lower feeding levels observed by subordinate JJ but single JJ ate even less than those kept in pairs. The results of this study suggest that it is not possible to make generalizations to satisfy optimal diet requirements of the species because of the considerable individual variation found. Quantifying intake and preference from direct observations of the birds during feeding can be a useful technique to help with the formulation of diets. Further studies are required to determine the roles of sex, age and origin on food consumption

and preference. The behaviour of paired and single birds should also be assessed in order to identify suit- able methods for feeding dominant and subordinate birds in an attempt to optimize nutritional intake of each individual.

Key-words: aggression, direct-observation sampling, food intake, food preferences, nutrition, St Lucia parrots

Formulating diets for captive birds poses considerable challenges because nutrient requirements need to be adjusted according to age, activity and reproduc- tive status of the animals (Alderton, 1986). Most zoos achieve this by pro- viding a nutritionally complete manu- factured diet in order to protect the birds from fluctuations in food nutrient con- tents and nutrient loisses caused by storage and preparation. Although manufactured diets are convenient, natural diets have benefits for the animal beyond nutrition by meeting psychological and behavioural needs as well as physiological ones. Furthermore, if c,aptive-breeding pro- grammes are to propagate species for reintroduction, naiural diets provide animals with the opportunity to manipu- late food items and examine texture, shape and colour of foods in preparation for living in a wild habitat.

Researchers who have attempted to quantify the diets ol’ birds in captivity to date have used estimates of consumption based on ‘food offered’ to ‘food left over’ ratios (Ullrey et al., 1991). Although this method may provide some approxima-

Page 2: Individual variation in food consumption and food preferences in St Lucia parrots Amazona versicolor at Jersey Wildlife Preservation Trust

tions of diet, it is affected by inaccuracies related to the recovery of left-over food when birds are housed in pairs or groups (see, for example, Fidgett & Robert, 1993; Wrobel et al., 1995). Moreover, left-over studies are likely to be severely biased if there are individual differences in food intake and preferences. Formulation of natural diets should therefore reflect individual food choices which may be affected by age, sex, group structure and breeding origin of the birds.

There are four Amazon parrot species of Lesser Antilles which are classified as Vulnerable (IUCN, 1996): Red-necked parrot Amuzona arausiaca, St Vincent parrot Amazona guildingii, Imperial parrot Amaionu imperialis and the St Lucia parrot Amaionu versicolor, which has been seriously affected by habitat destruction and the pet trade. Amazona versicolor inhabits the montane forests of St Lucia and in 1992 numbers were esti- mated to be c. 300 individuals (Jeggo et al., unpubl.). In 1976 Jersey Wildlife Pres- ervation Trust established a captive- breeding programme for the St Lucia parrot, thereby creating a need for studies that investigate feeding behaviour and nutritional requirements of wild and cap- tive birds.

At Jersey, research has been carried out to monitor the diet of St Lucia parrots in the collection. Following premature deaths and poor reproduction, suspected to be linked to an inadequate diet, Fidgett & Robert (1993) highlighted some nutrient deficiencies in the diet offered and

of origin, sex, age and pair dynamics on food intake and preference was also investigated. Although preliminary, the objective was to determine whether it is possible to ignore individual differences in how birds eat and assume that animals will choose food items in the proportions they are offered in an assumed optimal diet.

SUBJECTS Between 8 August and 7 September (n = 24 days) the food consumed by four pairs and four single J St Lucia parrots at Jersey was recorded (Table 1). The birds were maintained in two locations: two 3-$ pairs, a 3-3 pair and two single 33 were housed in five aviaries in the Car- ibbean Range (CR) and the other two ;-; pairs in aviaries in Shep’s Field (SF) (Table 1). Six of the study birds were wild- born (4.2) and brought into the collection as adults and the remaining six (4.2) were born and hand-reared at Jersey. Differ- ences in age and body mass of wild-born and captive-born birds existed; wild-born parrots were older (mean f SD, 18.1 k 3.8 years) and heavier (675.7k 146.1 g) than

I D NO. ORIGIN BODY A G I AVIARY MASS (years) (&Y

-+ B1076 Jersey 585 9 SFI B2283 Jersey I80 5 C R ? B479 St Lucia 580 18 SF 1 B480 St Lucid 680 18 C R2

recommended changes in protein and fat G 131589 Jersey 445 7 CRZ B1865 Jersey 420 6 CR.5 B1867 Jersey 410 6 CR I content, and some mineral (notably Ca:P)

and vitamin concentrations. Although the B1982 Jersey 490 6 CR5 study identified general nutritional imbal- B465 St Lucia 1000 28 CR2 ances in the food offered, it lacked B476 St Lucia 705 18 CR3

B477 St Lucia 505 18 SF3 SF 1

information on the actual foods and nutri- B568 St Lucia 650 25 ents consumed by individuals, and the fac-

tors affecting differences in intake. In this study the quantities of different food types , Fldgett ~ Robert (1993)

Table 1 . The origin, age and body mass of St Lucia parrots Amazona verrrcolor observed during a study of fond intake and preferences at Jersey Wildlife Pres- ervation Trust.

consumed7 item preferences and llutri-

tional intake were recorded from direct observations of individuals. The influence

Page 3: Individual variation in food consumption and food preferences in St Lucia parrots Amazona versicolor at Jersey Wildlife Preservation Trust

JERSEY WILDLIFE PRESERVATION TRUST: ST LUCIA PARROT FOOD CONSUMPTION A N D PREFERENCES 20 1

captive-born birds (age 4.0 k 1.3 years; body mass 455.0 k 67.2 g).

All exhibits comprised a free-flight weldmesh outdoor enclosure (7.2-9 m x 3.6 m x 3.6 m high) and an indoor house (1.8 m x 3.6 m x 2.2-3 m high), The floor of the outdoor enclosure was covered with sand and planted with shrubs. Perching and raised feeding platforms were located in both inside and outdoor areas. The indoor area was heated to 26°C and a timer-controlled light prolonged day length during winter (1ight:dark 12: 12).

FEEDING REGIMES All parrots were fed twice daily and were offered the same diet throughout the study period. The diet comprised 13 fruits, four pulses, a bean mix (soaked haricot, pinto and butter beans), a soup mix (pearl barley, red split lentils, yellow and green split peas, marrow-fat peas and pudding rice) and seven types of vegetables. Some processed foods, such as commercial parrot pellets, were also given. All foods were prepared in the same way but the actual items offered differed on a daily basis depending on availability. All birds were offered the same selection of food items each day.

The mean mass (L-SDg) of food offered to each bird per day was 310.9k62.5 g. The amount of food offered per kg of body mass averaged 200.7k57.2 g kg-I: 84.5k35.9 g kg-I for the morning feeds and 1 18.0 f 29.7 g kg- I

for the afternoon feeds. The mean number of food types offered to individuals was the same for both morning and afternoon feeds (12.5 f 2.8 types).

Food was prepared in the morning and the ration for each bird was divided between two plastic dishes for the morning and afternoon feeds. Morning feeds (1000 hours) were placed on the raised feeding platform in the outside enclosure on dry days or when there was only light rain. If it was raining more heavily the birds were fed indoors. All afternoon feeds (1 600 hours) were given

inside. Water was changed daily and pro- vided ad libitum.

Average mass of single food pieces was derived by weighing samples of each food type ( f0 .1 g) using an Ohaus CT-600 balance.

DATA COLLECTION Because the parrots only fed immediately after food presentation, feeding data for the focal animal/pair (after Altmann, 1974) were collected by one observer for a period of 60 minutes commencing upon food presentation. Because one parrot was observed each day, certain foods appear in analyses for some birds but not for others. This does not affect calculated preference indices because these were gen- erated from the total amount of food con- sumed from the total niass of food offered during all study sessions.

During feeding bouts the time, food type and the number of pieces ingested or rejected were recorded. A feeding bout was defined as the period of time in which an animal ate continuously. Each focal animal was observed for six sessions during morning or afternoon feeds (total 72 hours of observations; n = 12 birds). In addition, the occurrence of aggressive interactions within pairs during feeding was recorded.

CALCULATION OF AMCUNT OF FOOD CONSUMED The mass of food consumed by an indivi- dual was determined by counting the number of pieces ingested and multiplying by the average mass of each food type (see Smith et al., 1989, for a similar method). When only a portion of a food item was consumed, the proportion ingested was estimated visually and subsequently con- verted to grams.

DIET DIVERSITY The diversity of each bird’s diet for each session, was calculated using the Simpson’s index (Krebs, 1989). This index ranges from a value of zero (individuals

Page 4: Individual variation in food consumption and food preferences in St Lucia parrots Amazona versicolor at Jersey Wildlife Preservation Trust

111 NO. FOOD MASS INTAKE/ SESSION

(6)

, B1076 1650f243 B2283 24 21 f 3 3 37 B479 14 34 f 2 09 B480 I4 S 8 + 3 63

T3 B1589 B1865 81867 B1982 B465 8476 B477 B568

18.34 i 7.95 16.88f 10.39 10.54f3.83 6.57 f 5.35

18.56 f I 1.79 10.65 f 3.92 1756f 5.12 16.45 f 5.40

NO. PIECES CONSUMED/ MINUTE

1.10f 1.41 0.51 10 .66 0 ~ 5 0 f 0 ~ 1 0 0.25 * 0.10

0.2 1 * 0.08 0.22 f0.07 0.28 f0.23 0.26 f 0.43 0.46 f 0.1 1 0.29 f 0.12 0.34 f 0.06 0.52f0.14

FOOI) MASS INGESTtD (glminute)

0.87 f 1.35 0.40 f 0.56 0.24 & 0.03 0.24 f 0.06

0.31 20.13 0.28 f 0.17 0.18 f 0.06 0.53f 1.01 0.3 I & 0.20 0.18 f0.07 0.33 f0.09 0.27 10.09

TIMI- SPENT FEED IN G (minuted session)

41.17 f 82. I5 16.95 I29 .67 3.75 f 0.48 4.06 -t 1.24

5.28 1.84 3.89f 1.10 4.97 f 1 ’ 15 8.42 f 10.52 5.92 k2.76 3.26 i 0.59 S.40f 1 . 1 I 3.99 k0.59

FOOL1 MASS INGESTED/ K G OF BIRD

89.03 i 138.28 63.72 i 87.80 24.72 i 3.61 21.44k5.34

41.21 i 17.86 41.1 7 f25.34 25.72 f 9.35 64.43 f 83.58 18.56& 11.79 15.11 k5.55 34.78+ 10.13 25.3 1 f 8.30

DIET DIVFRSIl Y i f f y

0.73 & 0.1 5 0.80 f0.1 2 0.58 f 0.2 1 0,82+0.15

0.87 i 0 4 3 0.83 f0.12 0.67 f 0.39 0.52 k0.30 064& 0.1 6 0.77*0~10 0.79 f 0.09 0.68 f 0.1 0

Simpson’s diversity index. Table 2. Food intake of St Lucia parrots per session (n = 6), ingestion rates (g per minute), time spent feeding per session, diet diversity and food mass ingested per kg of bird.

with a diet consisting entirely of one food type) to higher values (individuals that ate portions of each food type).

FOOD ITEM PREFERENCE A N D ORDER OF CONSUMPTION Preference for a particular food item was inferred using Ivlev’s ( 1 961) electivity index. The index compared usage and availability (defined as mass offered) of the different food types which were given to the birds during the total study period. The electivity measure ranges from - 1.0 to +1.0, with values between 0 and + 1 indicating preference and values between 0 and - 1 indicating avoidance. An overall measure of ‘acceptability’ of foods was also obtained by ranking the foods consumed by a bird according to the elec- tivity index of the food and obtaining an average rank for each food type for all 12 birds.

The order in which food items were selected from the bowl by each bird was also recorded. The average rank order of consumption was then used as another measure of acceptance of each food type.

STATISTICAL ANALYSIS Non-parametric Kruskal Wallis ANOVAS (KW) (Siegal & Castellan, 1988) were per- formed to detect differences between individual birds regarding mass of food consumed, diet diversity and food item preference. Wilcoxon Mann-Whitney tests (Wx) (Siegal & Castellan, 1988) were used to determine differences between groups by sex and origin. Kendall’s Coefficient of Concordance (W) (Siegal & Castellan, 1988) was used to express the intensity of agreement among rankings of food preference and order of consumption of the different foods by all birds. Corre- lations between variables were identified using simple linear regression analysis or Spearman rank correlation tests ( r , ) . Significance level for all tests was set at PzO.05.

RESULTS Food intake and ji>ed cluratiorz Feeding performance (food mass intake, ingestion rates, feeding time per session, diet diver- sity and food mass consumed per kg of bird) for each study bird is given in Table 2. Average food mass consumed by all birds per session was 15.4k4.4 g

Page 5: Individual variation in food consumption and food preferences in St Lucia parrots Amazona versicolor at Jersey Wildlife Preservation Trust

203 JERSEY WILDLIFE PRESERVATION TRUST ST LUCIA PARROT FOOD CONSUMPTION AND PF!EFERENCES

total intake (%)

20 I," t 81076

10

0 sm bm mb cp sb or to ba gb ph ca pl me ap ne br pe ae pr ki gf cy

62,283

30 40 i

ba gr cp bm sm ch pr sb ap ki or cu pe mb me pl ph ne to ae be

B4;'S

sm w or bm cp pl sb ki mb pr ph lo br ba pe me ae eg ap cu cy br ne gb

8480

10

0 c

;!Illnnnnl ,I ,I Inl II I( II , r I I I, I, ,, ,, ,, ,, ,, ,, ,, ,.

bm cp ba gr mb sh pe or gf sm ca pr ae sm ph ch sm PI M to cu cy ap ne me !3b

food type

Fig. 1. Total intake ("h) of food types for 12 St Lucia parrots Amazonu versicolor at Jersey Wildlife Preservation Trust, calculated from total food mass consumed per item per bird during the entire study period. Study birds (cb. captive-born; wb. wild-born): 9 B1076 (cb); 9 B2283 (cb); $. B479 (wb); 2 8480 (wb); 3 BlS89 (cb); 3 B186S (cb); 3 B1867 (cb); 2 B1982 (cb); 5 B465 (wb); 8 B476 (wb); 2 B477 (wb); 8 B568 (wb). Food type$. ae. apple; ap. apricot; ba. banana; be. black-eye bean; bm. bean mix; br. beetroot; ca. carrot; ch. cheese; cp. chick pea; cu. cucumber; cy. celery; eg. boiled egg; gb. green bean; gf. grapefruit; gr. grape; ki. kiwi; mb. mung beau; me. melon; ne. nectarine; or. orange; pe. commercial pellet; ph. peach; pl. plum; pr. pear; sb. soya bean; sm. soup mix; sw. swede; to. tomato; tp. turnip.

Page 6: Individual variation in food consumption and food preferences in St Lucia parrots Amazona versicolor at Jersey Wildlife Preservation Trust

204

total intake (%)

81589

pl gr ba cp or ae bm pr ki e g mb ne ph sm s b to pr gb ca cy pe

40 I

or bm ae gr pr pl ne cp sb to me sm ca mb ki pe ch sw

s m ba pr p i me ch to gr ae br ki cp pe rnb

40

30 1 B1982

or sb sm eg ki cp ba mb pe ch to bm gf me a e pr sw

food type

ranging from 6.6 g (6 B1982) to 24.2 g from 15.1 & 5.6 g kg ' (3 B476) to (P B2283). Time spent feeding per session 89.0 i 138.2 g kg- (F 81076). Modal was 8.1 _+ 10.1 minutes, from 3.3f0.6 intake for all birds was 20 g kg- I but this minutes ( J B476) to 41.2k82.2 minutes value ranged from 1 g kg-' to over (9 B1076). Controlling for body mass, 300 g kg-I per individual session. parrots ate on average 38.8k21.7 g kg I,

Page 7: Individual variation in food consumption and food preferences in St Lucia parrots Amazona versicolor at Jersey Wildlife Preservation Trust

JERSEY WILDLIFE PRESERVATION TRUST: ST LUCIA PARROT FOOD CONSUMPTION A N D PREFERENCES 205

total intake (%) 40 8465

10

0 nnl 1 1 II ll II I I ,. .. . - bm gr sm ba ki sb or cp pr mb me ap pe ch ae gf ph pl tp cy

B476

10

0 - ./n, ( , ,nl ( , ,I I, ,) ,) ), ,[ ,) ) ) ,, I I ,, , _

to sb eg ki sm ae mb br ch pr pe or ca cp me cp ne gf gb

40

B477

20

bm or ca cu ae sm me ba cp mb sb ch to ph ki pi pe br eg pr cy gf 111 gb

:: 20

B5Ei8

smbm or cpmembae ch pr ca ba pe ki to sb pl gb cu br ap ph gf eg

food type

Comparisons between sexes indicated that food intake was higher in 99 (16.6f2.8 g per session) than in $3 (14.4 & 4.2 g per session) (Wx = 58, df = 5, P=0.002). Ingestion rates (pieces per minute and mass per minute, respectively) were also higher for 99 (0.6f0.3 pieces per minute, 0.4k0.3 g per minute) than

for $8 (0.3f0.1 pieces per minute, 0.3k0.1 g per minute) (Wx=50, df=5, P=0.002). Similarly, 99 ate on average 45.2 f 79.7 g kg-' per session whereas S$ consumed less (21.5& 10.4 g kg-I; Wx=65, df=5, P=O.OOl).

Captive-born 99 were found to con- sume more food (76.1 k 9.0 g kg- I) than

Page 8: Individual variation in food consumption and food preferences in St Lucia parrots Amazona versicolor at Jersey Wildlife Preservation Trust

average choice rank 20 , - 18

16

14

12

10

8

6 4

2 0

tp ae to sb sw ap pr pl ph sm ch ba me ca bm ne ki br cp pe gr eg or cu gb mb cy gf be

food type

Fig. 2. Average order in which food items were selected, calculated from the average rank of each food type for all 12 St Lucia parrots. Turnip (tp) was, on average, consumed first and black-eye bean (be) last. Food-type identification as in Fig. 1.

captive-born 3; (60.8 f24.0 g kg-I; Wx = 49, df = 5, P = 0.002) but wild-born birds of both sexes did not differ signifi- cantly in food intake (YF23.1 1.6 g kg-I; 33 23.4k7.5 g kg-'; Wx=5, df= 11, P = 0.50). Food intake was negatively cor- related with age (r ,= -0.72; P=O.005).

The interaction between pairing of birds, origin and sex could not be exam- ined because of low sample sizes within some origin x sex x pairing categories. However, paired 74 were not observed to eat significantly more (45.2 k 79.7 g kg-I) than paired 33 (41.9k66.3 g kg-') (Wx= 14, df= 7, P= 0.90). Differences in food intake between paired and single birds by sex, could only be examined for 33. Single 28 ate significantly less (20.4f9.3 g kg-I) than 3-0 paired birds (Wx=23, df=7, Pt0.01) .

Percentage contribution of food types to the diet of individual parrots showed that the most consumed item contributed 10-30'%, of the total diet (Fig. 1). Total number of items eaten by individuals varied from 14 (3 B1867) to 26 types (TB480). Bean mix accounted for an average 19.4+4.7% of the diet for three birds (9 B480, 6 B465, 8 B477), soup mix was 16.6 5.7% of the diet for four birds (9 B479, 3 B568, B1076, 8 B1867), orange was 25.5 rfr 8.1% of the diet for two birds (3 B1982, SB1865), plum was 14.5% of the diet for 8 B1589 and tomato was 10.9% of the diet for 3 B476. For all

12 birds, the amount consumed of each food type was not correlated with the weight offered.

Difference in the amount of food con- sumed according to time of day was sta- tistically significant. Average total amount of food ingested by all birds was 22.7 f 40.7 g during morning feeds but significantly less (18.6 f 25.8 g) during afternoon feeds (Wx = 130, df = 47. P= 0.03). Weather conditions (sunny, cloudy or raining) also affected ingestion rates. More food was consumed on cloudy days (32.1 & 63.9 g, n = 9) than sunny days (1 7.7 & 24.6 g, y2 = 26) and much less was consumed on rainy days (1 3.8 k 6.6 g, n= 13).

Diet diversity The percentage of items eaten ranged from 42%) (2 B1867) to 100% (8 B477) of those offered. Thc overall diet diversity index calculated for all sessions for all 12 parrots (Table 2), showed that the highest dietary diversity index was typical of 3 Bl589 while the lowest was observed for 3 B1982. Dietary diversity for each bird was also assessed by calculating the Q statistic (Kempton & Taylor, 1974). Females were observed to eat more diverse diets (14.4 rtr 2.8) than 33 (8.1 f 1.9) (Wx=41, df= 11, P=0.004). These differences were also affected by the origin of the birds in the case of 97: cap- tive-born ?? (12.9k1.3) did not have significantly lower diversity diets than

Page 9: Individual variation in food consumption and food preferences in St Lucia parrots Amazona versicolor at Jersey Wildlife Preservation Trust

207 JERSEY WILDLIFE PRESERVATION T R U S T ST LUCIA PARROT FOOD CONSUMPTION A N D PREFERENCES

electivity index value I

n

-I 5 ph gb ba to me ne ap cp gf pl pr br 5m ae Sb mb cy ca or pe bm ki eg

1

r- 841283

8 - - 1 s t ' ' ' ' '

ch ap ba pr or cp me gr ne sb pl ki pe srn bm to mb ph cu ae eg gb gf cy be 3r ca

1

84 79

_i - 1 5 1 ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' '

eg ba cy br ca to mesm gb pr pl ap or cu cp kl ph ne sb mb ae pe bm 1p ch

1

8480

L_ . r 5 L " " " " " " " " " " ' "

ch or pl cp ca pe ha ap ne mb sb sm to pr gf ph ki cy bm gr gb w ae me eg br be

food type

Fig. 3. Ivlev's electivity indices for all food types consumed by each St Lucia parrot. Values between 0 and +I indicate preference and values between 0 and - 1 indicate avoidance. Bird and food-type identification as in Fig. 1.

wild-born ones (1 5.9 3.0) (Wx = 7, Food order and prej'erences Differences df=3, P=0.50), but wild-born 88 existed between birds in the order in (9.3 f 1.9) had a more varied diet than which food items were selected (W = 0.1 6, captive-born ones (6.9 f 0.8) (Wx = 25, k = 12, P= 0.05). Tht: pooled data for all df = 7, P = 0.002). birds indicated that turnip was, on

Page 10: Individual variation in food consumption and food preferences in St Lucia parrots Amazona versicolor at Jersey Wildlife Preservation Trust

208

1 5

0 5

0

1

-0 5

electivity index value

1 - -

1

0 5

0

0 5

1

-1 5 eg pl or ne ba ae cp gb pr gr ki sm to mb ph 5b bm ca cy pe ch cu gf 11, ap be

1 ,

-1 5 ' J ba ae me lo pr br ch pl sm gr ki cp pe mb ne gf or sw sb ca bm cu eg cv

1

81982

-1 5 1 I ba eg or sb ki me ch cp ae sm gf lo pe bm ma pi cy cu ne gb ca ap Sw br be

food type

average, consumed first and black-eye significantly between birds (W = 0.17, bean last (Fig. 2). Ivlev's electivity indices k = 12, P = 0.05). The number of types not for all food types consumed by each study eaten varied from ten (42% of all foods subject (Fig. 3) showed that the number of consumed) in 5 B1867 to none in 3 B477. rejected and preferred items differed Fond types showing negative (0 to - 1 )

Page 11: Individual variation in food consumption and food preferences in St Lucia parrots Amazona versicolor at Jersey Wildlife Preservation Trust

JERSEY WILDLIFE PRESERVATION TRUST ST LUCIA PARROT FOOD CONSUMPTION AND PREFERENCES 209

electivity index value 1

13465

- 1 5 ' " " " " " " " " " " " ' - ch or ap ki bm ba sb Qr sm pr mb pe cp tp pl gf cy ph meae gb eg to ne br be cu ca

1 ,

cu ph cy me eg ba ae ca or to tp pr pl gf ch ki br cp bm pe sm sb n b gb

1 1

- 1 . 5 ' " " " ' " " ' " " ' " " " ' ch me ba gb to eg ae cu br sm or pl pr gf ap cp ca mb pe ki sb bm ph tp ni! cy

food type

electivity values (i.e. 'disliked') also Number and percentage of foods ranged from 18 out of 24 consumed (75%) rejected and disliked by parrots related to in 6 B1865 to ten of 27 types (37%) in sex and origin are given in Table 3. There 9 B480. were no significant sex differences in the

Page 12: Individual variation in food consumption and food preferences in St Lucia parrots Amazona versicolor at Jersey Wildlife Preservation Trust

ORIGIN SEX ID NO. OFFERED DISLIKED RFJEC'TF 11

ITEMS ( n ) FOODS FOODS (%I) (''4,)

Captive-born -c B1076 26 56 52 1 69 B2283 28 59 26 41 15

2s B1589 28 51 69 40 00 B1865 24 15 00 78 89 B1867 24 54 17 7 69 B1982 2s 68 00 i? 94

Wild-born -f B479 2s 42 31 27 21 B480 27 31 04 40 00

;7 B465 28 51 14 50 00 B476 26 50 00 76 36 B477 26 58 31 0 00 B568 26 52 00 15 38

Table 3. Percentage of foods disliked and rejected by St Lucia parrots at Jerse? Wildlife Presenation rrust according to sex and origin.

percentage number of items rejected by 99 (29.7f7.8%1) and 85 (30.2f 13.1%) (Wx = 26, df = 1 1, P = 0.53). However, captive-born 88 rejected more items (46.5 & 6.5%) than wild-born S$ there were no significant differences between wild-born (33.6 f 6.4%) and cap- tive-born (25.7 f 18.0%) 99. Captive-born 29 rejected significantly fewer items than captive-born 32 (Wx =45, df = 5 , P = 0.004) but there was no difference

(32.7+17.3%) (Wx=11, df=7, PzO.03);

average preference rank

:x 1 15

between the sexes among wild-born birds. Overall 9 parrots disliked fewer items (48.8 f 9.4%)) than 33 (59.0 7.9%) (Wx = 19, df = 1 1, P = 0.03). Captive-born 99 disliked 57.9 f 1,4'1/0 of items consumed but wild-born 99 disliked significantly less (39.7 & 2.6%). Captive-born (63.7 f 8.3%) and wild-born (54.4&3.5%) 33 did not differ in the percentage of disliked foods in their diets.

According to the age of the birds, older parrots disliked less foods

7 i

10

5

0

than younger

__ ba or me gr ch pr to pl cp ae ki ap sm eg ne sb ph gb mb pe ca gf br cu cy ip sw be

food type

Fig. 4. Average preference rank, calculated from electivity indices for 12 St Lucia parrots, for each food type. The most preferred food type was banana (ba) and the least preferred food type was black-eye bean (be). Food-type identification as in Fig. 1.

Page 13: Individual variation in food consumption and food preferences in St Lucia parrots Amazona versicolor at Jersey Wildlife Preservation Trust

JERSEY WILDLIFE PRESERVATION TRUST ST LUClA PARROT FOOD CONSUMPTION AND PREFERENCES 21 1

SEX AGGRESSIVE BEHAVIOUR TOTALS PAIR

PECK WING SCRATCH FOOD FIGHT ATTACK BLOW ATTACK SNATCH

B1589 B2283

B465 B480

B477 B1076

B568 B479

TOTAL

3 3 1 1 2 1

s 1 2 r 3

d 47 5 1 57 1 3

s 4

n

r

P 17 1

130 7 1 10

5 1

3 4 7

2 55 4 65

4 I 19

11 159

Table 4. Distribution of aggressive acts observed in pairs of St Lucia parrots at Jersey Wildlife Preservation Trust.

ones ( r ,= -0.66, P<O.Ol) but no signifi- cant correlation was found between age and percentage of rejected foods ( r , = 0.29, P = 0.50).

Average ranks of all foods, calculated from the electivity indices for the 12 par- rots, demonstrated that the most preferred food was banana while the least preferred was black-eye beans (Fig. 4). Despite a considerable variation in the data, these preference values were positively corre- lated with the amount (g) eaten per item (y = 0.40 f 0.34x, df = 229, P<O.OOOl). The general order (ranking of foods based on the average rank for all sessions per type per bird) in which the food types were eaten was also positively correlated with the general preference for each item (r , = 0.39, P = 0.03).

r2 = 0.1 5,

Aggressive behaviour during feeding Table 4 shows the number of aggressive acts observed during the study period. On average, frequency of aggression or sub- mission was low (0.13 acts per minute). Most aggressive behaviours between birds were peck attacks (81.7%) followed by wing blows (4.4%) and scratch attacks (0.6%). Of the 159 recorded aggressive acts, more than half (58.9%) were initiated

by 99. Most aggression (79.9% of all acts) was observed in the SF3 aviary (9 B1076/3 B477), where a similar number of attacks was made by both birds. However, 9 B1076 initiated more fights than 6 B477 and the 3 was seen moving away from the 9 more times than the 9 moved away from the 6. In all pairs except 9 B480IS B4658, which showed only one instance of peck attacks (8 B465) and none of wing blows or scratch attacks, more aggressive acts were initiated by 99. To understand the possible influence of aggression on the quantity of food con- sumed by each sex, the amount of each food type eaten by 38 and 99 within the four pairs was compared (Fig. 5). Food mass consumed per item was biased towards 99 (regressions slopes 9 B1076/ 8 B477 = 0.6 f 0.2; 9 B 1589/3 B2283 = 0.3 f 0.2; 9 B479/$ B568 = 0.7 0.2) except in pair 9 B480/3 B465 (regression slope= 1.OfO.4).

DISCUSSION Direct visual recording of feeding behav- iour has not been utilized by many inves- tigators studying the diets of captive birds even though in most captive situations there is good visibility of the study

Page 14: Individual variation in food consumption and food preferences in St Lucia parrots Amazona versicolor at Jersey Wildlife Preservation Trust

212

log male food consumption/item

“-81076/8477 +8480/8465 * 81589/82283 *8479/8568

1.5

1

0.5

0

-0.5

-1 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 1.2 1 1

log female food consumption/item Fig. 5. Comparison of the food mass consumed by 3 and St Lucia parrots housed in pairs. Each point on the graph corresponds to the total amount of different food types (8) consumed throughout the entire study period. Studj, pairs G B1076 (cb) and 3 B477 (wb); $’ B480 (wb) and 3 B465 (wb); 9 B2283 (cb) and 3 B1589 (cb):

B479 (wb) and 3 B568 (wb).

animals. The present study has success- fully employed this method to determine food intake of 12 parrots. The alternative method, left-over food analysis, is limited in the information gained and when used for paired birds, can only approximate food intake per bird by assuming that each animal eats identical amounts and that neither bird ate all of one item. The present study has shown that ‘per bird’ estimations are not reliable because con-

siderable variation in the amount of food consumed, food item preference and, therefore, nutrient intake can exist between birds.

A practical problem associated with the use of the direct-observation method is the estimation of the amount of food eaten when only a fraction of the piece has been consumed. Estimation of portions consumed of less than one quarter of a piece may have introduced some bias,

Page 15: Individual variation in food consumption and food preferences in St Lucia parrots Amazona versicolor at Jersey Wildlife Preservation Trust

JERSEY WILDLIFE PRESERVATION TRUST ST LUCIA PARROT FOOD CONSUMPTION AND PREFERENCES 213

especially when dealing with smaller-sized items. Although some overestimation is likely, the number of times in which less than one quarter of a piece was consumed was actually minimal (2% of records). A comparison between the direct-observa- tion and left-over food methods will shed light on the biases associated in each sam- pling technique.

Differences between wild-born and cup- tive-born parrots Although all birds in this study were given a similar variety of foods to choose from, the parrots con- sumed different amounts of these foods, which may reflect preferences. Observa- tions of choice order and electivity showed that there was a clear individual bias in which food items each animal ate. In addition, the correlation between amount of the item consumed and its elec- tivity value suggests that, in general, the birds eat more of what they prefer and reject what they do not like.

This study has also indicated a potential difference in the way captive-born and wild-born parrots feed. Although this observation cannot be substantiated at present because age and origin in the sub- ject animals are correlated, this finding is of crucial importance. If true, captive- born parrots may overeat, reject more offered items and, consequently, consume diets which are nutritionally suboptimal. As a result of this, it is probably not sur- prising that captive-born parrots at Jersey have been more affected by ateriosclerosis and visceral gout associated with inappro- priate diets than wild-born ones (Fidgett & Robert, 1993). Further investigation on the influence of rearing history, especially on the impact of foods given from hatching, is required.

Diet, sexual differences and the influence of’ pair dynamics There was a significant contrast between the sexes in the amounts eaten and diet diversity, related to origin (or age) differences. Although this may be related to differences in metabolism and

levels of activity of each sex, in some pairs it may also reflect the level of aggression in !&’ at feeding tirne. This was most clearly seen in two pairs of birds (9 B479/$ B568 and 9 B1076/$ B477) where the food intake of the was related to more time spent feeding but with more aggressive acts directed at the 66. Female B1076 had the highest average food consumption of all the observed parrots and showed the highest aggression rates. Only 0 B2283 had a high average food consurnption rate despite exhibiting low aggressive behaviour towards its partner but this may have been because the 6 was unable to fly and move around the enclosure.

CONCLUSIONS The challenge when fcirmulating psittacine diets is to be able to offer food that will meet the specific nutrient requirements of a bird while allowing {.he animal to choose from a variety of items. Providing foods that are visually attractive and palatable is also an effective means of providing behavioural enrichment. More important, because birds may select food items on the basis of colour and texture, rather than on taste or nutrient conitent, it is important to ‘guide’ optimal intake. Manufactured pellets, although nutritionally complete, do not provide for the psychological and behavioural needs of the parrots. How- ever, pellets in combination with other favoured and nutritionally suitable foods may provide the ideal diet, but even this must be adapted to account for individual preferences and age of the birds.

ACKNOWLEDGEMENTS

We are most grateful for the support and help of everyone in the Bird Department at Jersey Wildlife Preservation Trust, particularly to David Jeggo, Head of Department, who entrusted the present work to us. Noel Snyder gave useful suggestions and comments on an earlier draft of this paper.

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2 I4

PRODL CTS ME\TIONED IN THE TEX?

Ohaus CT-600: balance, manufactured by Ohaus Scale Corporation, 29 Hanover Road, Florham Park, NJ 07932. USA Parrot pellets: manufactured by Special Diet Serv- ices. Witham. PO Box 705, Essex CM8 3AD, UK

REFERENCES ALDERTON, D. (1986): Nutrition in parrots, h i e s und c~ockutoos. London: Saiga Publishing Co. ALTMANN, J . (1974): Observational study of behavior: sampling methods. Behaviour 49: 227-267. FIDGETT, A. L. 8; ROBERT, J . N. (1993): An investi- gation into nutrition and mortality in captive St. Lucia parrots A~~iu-.ona versicolor. Dodo 29: 103-1 25. IUCN (1996): 1996 IUCN red list of threatened trninrtr1,s. Gland: IUCN. 1vr.w. V. S. (1961): E,xperirnentul ecology of the fi~eu‘ir?~ of fis1ie.s. New Haven. CT: Yale University Press. Jt:c;c;o. D. F.. JOHNSTON, J. & Cox, C. (Unpubli- shed): Prc~lirizinurj~ report on the I992 biennial St. L i ~ i r r .snrwy of tlir Sr. Luciii pcirrot Amazona vevsi- color.. Unpublished report. Jersey Wildlife Preserva- tion Trust, 1992.

KBMPTON. R. A. 8; TAYLOR, L. R. (1974): Log-serie.; and log-normal parameters as diversity discriminants for the Lepidoptera. Journd of’ Aninzal Ecolox? 43: 381-399. KREBS, C. J. ( 1989): Ecologicul nzefliotiologj.. New York: Harper and Row. SIEGAL, S . & CASTELLAN, N. J. (1988): Nonpurunrc~- tric stutistics for the hehaviortil sciences (2nd edn). New York: McGraw-Hill Book Company. SMITH, A., LINDBURG, D. G. & VEHRENCAMP. S. (1989): Effect of food preparation on feeding behavior of lion-tailed macaques. Zoo Biologj. 8: 57-65. ULLREY, D. E., ALLEN, M. E. & BAEX D. J . (1991): Formulated diets versus seed mixtures for psitta- cines. Journul of Nutrition 121: 193--205. WROBEL, M., TWINNEY. J . K. & VALDES, E. V. (1995): Monitoring food intake of a pair of Major Michell’s cockatoos, I Cucatua leudbeutcri). Proceed- ings of the $rst unnuul conff’rencc of’ tlir Nrrtritiorz Advisory Group, 1995: 228-251. Toronto: American Zoo and Aquarium Association.

Manuscript submitted 23 July 1996

Int . Zoo Yb. (1998) 3 6 214222 0 The Zoological Society of London

Management of the Amazon River dolphin

at Valencia Aquarium, Venezuela Inia geojfiensis

E. 0. BOEDE’, E. MUJICA-JORQUERA? & N. DE BOEDE’ I Funrimion Aquarium de Valabnciu, Apurtudo postal 1595, Vulenciu 2001 and 2Fundricicin Nucional de Purques Zoolbgicos y Acuarios (FUNPZA) , Apurtudo 1567, Vukencirr 2001, Venezuelrr

The Amazon River dolphin Inia geofjensis is dis- tributed throughout the Amazon and Orinoco River basins. The species is rare in captivity and as a t 31 December 1996 there were only 3.0 reported to ISlS and I .4 maintained at Valencia Aquarium, Ven- ezuela. This paper describes the husbandry, diet and veterinary care of 14 dolphins maintained at Valencia Aquarium between 1975 and 1995, and the rearing and development of a I born at the institu- tion in 1994.

Kq-ii.orrls.- Amazon River dolphin, development, diet, husbandry. longevity. veterinary treatment

The Amazon River dolphin Iniu gcwff- jiensis, also known as the Orinoco dol- phin, pink dolphin, tonina, boto and bufeo, is the largest freshwater dolphin and is found in the rivers and siow- flowing muddy tributaries of the Amazon and Orinoco basins and in clear, aniber- coloured rivers, such as the Rio Negro and Ventuari (Trebbau & Van Bree. 1974; Trebbau, 1975) (Plate 1). In 1800 A. Humboldt reported a large number of