Use of supplementary feeding to induce breeding in free-living kakapo Strigops habroptilus in New Zealand

Biological Conservation 69 (1994) 97-106 © 1994 Elsevier Science Limited Printed in Great Britain. All rights reserved 0006-3207/94/$07.00 ELSEVIER

USE OF S U P P L E M E N T A R Y F E E D I N G TO I N D U C E B R E E D I N G IN FREE-LIVING KAKAPO Strigops habroptilus IN NEW Z E A L A N D R. G. Powlesland & B. D.

Lloyd

Science & Research Division, Department of Conservation, PO Box 10-420, Wellington, New Zealand

(Received 27 March 1993; revised version received 20 July 1993; accepted 20 July 1993)

Observations of kakapo in Fiordland (Fig. 1 in Lloyd & Powlesland, this issue) in the late 19th century (Henry, 1903) and on Stewart Island from 1977 to 1988 (Powlesland et al., 1992) indicated that they usually bred at three-four year intervals in years coinciding with above-average crops of fruit, e.g. of the podocarps rimu Dacrydium cupressinum and pink pine Halocarpus biformis (Powlesland et al., 1992). Preliminary nutrient analyses in 1987 of the main foods on Stewart Island indicated that podocarp fruit contained about twice as much nitrogen (crude protein) as most other foods eaten by kakapo (A. Grant, pers. comm.). Subsequent analyses indicated that the breeding season diet of kakapo contained nearly twice as much crude protein as the non-breeding season diet (James et al., 1991). However, the crude protein level of 59 g/kg in the breeding season was still very low when compared with the requirement of at least 150 g/kg for cockatiel Nymphicus hollandicus nestlings (Roudybush & Grau, 1986). Thus, it seemed that kakapo bred only when foods relatively rich in protein were available. This suggested that by supplementing the kakapo's natural diet with proteinrich foods it might be possible to induce breeding. We describe how free-living kakapo on Little Barrier Island were encouraged to feed from feeding stations, the design of the stations, the food supplements, how often stations were used by kakapo (September 1989 to June 1991), and the impact of the foods on the birds.

Abstract Nine female and 13 male kakapo Strigops habroptilus ( Psittacidae) were transferred from Stewart Island and Fiordland (one male) to Little Barrier in 1982. During the following seven summers (1982~83 to 1988-~89) there was no evidence that any bred. A programme of providing food supplements to some kakapo was begun in September 1989 to induce breeding. Six preferred foods (apple, kumara (sweet potato), and the kernels of almonds, brazil nuts, sunflower seeds and walnuts) were eventually supplied ad libitum each night at up to 12 feeding stations. These foods were eaten least often by both sexes in summer, when male activity at track-andbowl systems was at its peak and females were mating, laying or incubating. Females nested on Little Barrier Island for the first time in the summers of 1989-90 and 1990-91, though nesting success was low.

Keywords: New Zealand, kakapo, Strigops habroptilus, supplementary foods, breeding.

INTRODUCTION The kakapo Strigops habroptilus is a large, flightless, nocturnal parrot, endemic to New Zealand. It is herbivorous, and is the only lek-breeding parrot (Merton et al., 1984; Powlesland et al., 1992). The species was originally widespread on the three main islands of New Zealand (Williams, 1956; Millener, 1981). Decline in numbers began in pre-European times and accelerated following the European introduction of mammalian browsers and predators, and the widespread destruction of forest. By 1989 the kakapo was critically endangered, with only about 40 birds known to survive (Powlesland, 1989). It survived on Stewart Island, Codfish Island and Little Barrier Island (see Fig. 1 in Lloyd & Powlesland, this issue). A male on Stewart Island was the only bird known in the natural range of the species. Twentytwo kakapo (nine females and 13 males) were transferred to Little Barrier Island in 1982 to remove them from predation by feral cats Felis catus (Lloyd & Powlesland, this issue); at least 11 survived in 1989 (Hodsell, 1989). There was no evidence in 1989 that any of the kakapo on Little Barrier Island had bred during the previous seven summers; an urgent need to stimulate breeding was recognised.

STUDY AREA Little Barrier Island (3055 ha, maximum elevation 723 m) is situated in the Hauraki Gulf (36°12'S, 175°07'E), 22 km east of North Island (Fig. 1 in Lloyd & Powlesland, this issue). Importantly, as a refuge for endemic fauna, the kiore Rattus exulans is the only introduced mammal present. The island is an eroded extinct volcano comprising steep ridges radiating from central peaks. The vegetation zones inhabited by kakapo are described in Moorhouse and Powlesland (1991). The island has a warm-temperate climate, with a mean annual temperature of 15.7°C (range: 4-32°C) and a mean annual rainfall of 1504 mm at sea level (Moorhouse & Powlesland, 1991). Twice as much rain falls in winter as in summer, and summer droughts are frequent. 97

98

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METHODS Locating and radio-tagging kakapo Kakapo were captured to identify birds at feeding stations and track-and-bowl systems (where males 'boom' to attract females for mating (Powlesland et al., 1992)), or for radio-tagging, either by locating them at roosts during the day with muzzled dogs and captured by hand, or by trapping them at night in baited walkthrough cage-traps. Each bird was identified either from a black-and-white pattern painted on its metal band, or after capture by the numbered stainless steel leg-band with which all transferred kakapo were fitted. Transmitters were mounted on the backs of some kakapo using a harness of polypropylene braid attached around the base of the wings. The transmitter, a lithium battery, and a miniature magnetic reed switch encased in silicon resin within an epoxy resin shell, weighed 20-35 g and had a field life of 120-360 days. Hand-tracking (Kenward, 1987) was used to determine the birds' general positions each day, to find nests, and to determine whether a female was present when the nest was to be checked.

Use of feeding stations Baits (carrot, apple or kumara Ipomea batatas) skewered on wire stakes were placed at 50-100 m intervals

along all tracks to detect where kakapo foraged. Once the distinctive feeding sign was evident (beak marks and 'chews' (Powlesland, 1989)), the bird was captured to determine its identity. It proved necessary to present the foods to each kakapo on a structure so as to shelter it from rain and make it inaccessible to kiore. A tray 350 mm above the ground proved inaccessible to most kiore. Before the feeding station was established, the previously baited wires were moved closer together over several nights to a reasonably flat area of track. The feeding station was then gradually assembled over several nights as long as the bird continued to feed regularly at the site. The feeding station eventually consisted of a 50-mm deep tray (300-mm diameter pan) supported 350 mm above ground by a 25-mm diameter aluminium tube (Fig. l(a)). Subsequently a cover (600-mm black plastic dust-bin lid) 150 mm above the tray was added to shelter it from rain. Although kakapo fed readily from such stations, some rats jumped to the trays and fed, and at stations in the cloud forest the frequent mist and wind made the food so damp within 24 h that it had to be replaced. To overcome these problems a lid was placed directly over the tray which contained one or two hinged flaps which kakapo had to raise to obtain the food (Fig. l(a)). Initially the flap was tied fully

Supplementary feeding of wild kakapo open and then lowered gradually over three weeks. Kakapo quickly got used to raising the flap to reach the food; very few rats learnt to do so and the lid kept the food dry except during heavy rain. To reduce the need for daily stocking, a hopper was designed to hold sufficient food for a kakapo for two-three nights'(Fig, l(b)). A 300-mm length of 80-mm diameter plastic drain pipe formed the column of the hopper, with the base being a section of drain pipe with a I l0 ° bend. A cover was placed over the top and a hinged flap over the front of the base. The column was clamped to a pole at an angle so that the food readily fell as kakapo removed it. This hopper proved suitable for dry, small items of food, such as nuts and seeds, and for water. Food fragments left on the ground were removed to prevent the kakapo eating food contaminated by mud, mould and rat faeces. To improve hygiene, a piece of plywood (400 × 300 mm), which the birds stood on when feeding, was placed at each station. Most food fragments left by kakapo fell on these boards. Small hides were set up gradually over several days within 5 m of five feeding stations. An image intensifier and infrared lights were used to observe kakapo and rats at feeding stations. To reduce the numbers of rats, food scraps were removed and up to three snap traps in individual tunnels were set within 3 m of each station. Nonetheless, a few rats were present at each station most nights.

Automatic weighing Kakapo feeding at the stations were weighed using a Sartorius balance and a Toshiba lap-top computer as a data logger via an interface. Weights with the date and time were recorded when a bird stood on the balance. The system was powered by a 12-volt lead acid battery, and the computer, interface and battery were enclosed in a weather-proof container nearby. To get the birds used to stepping on the scales, the base boards were first replaced with wooden platforms 60 mm high, and then replaced with the scales. Monitoring at track-and-bowl systems and nests All known track-and-bowl systems were inspected regularly in the 1989-90 and 1990-91 breeding seasons from 1 October until evidence of kakapo activity ceased, usually in April. Inspection varied from daily, for conveniently located active systems, to monthly, for remote and inactive systems. Any kakapo sign (such as grubbing, trimming of vegetation, feeding sign, faeces or feathers) at or near each system was noted. Kakapo feathers at feeding stations and track-andbowl systems were collected and recorded. Large numbers of feathers at a system indicate that a copulation or a fight has occurred there (Powlesland et al., 1992), and occupied systems were carefully checked for feathers during breeding seasons. Clusters of feathers thought to result from a copulation were restricted to a small area (<1 m 2) within 5 m of an occupied bowl, were mixed into the substrate and were mainly down feathers (Lloyd & Powlesland, 1992).

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Nests were found by trained dogs tracking the scent of females using feeding stations, or by radio-tracking. Females for whom no nest was discovered were captured and examined for the presence of a brood patch late in the season. RESULTS

Foods offered During the first year of supplementary feeding 45 foods were offered; two were apparently untouched, and 20 were tasted but then rejected (Appendix 1). The remaining 23, eaten regularly, were mainly root vegetables, seed and nut kernels, and fleshy fruit. Six foods (apples, kumara, and kernels of almonds, brazil nuts, sunflower seeds and walnuts) were provided nightly because they were eaten in quantity by all the kakapo, were readily available, could be stored for the two weeks of a field trip, and carried to the stations without deteriorating; they contained reasonable levels of protein and/or lipid. We doubted if we were providing an entirely suitable diet on which females could raise young, and we did not know if the females would obtain missing nutrients from natural sources. Therefore, a greater variety of food was provided at stations used by the two females with nestlings in 1991 (Appendix 1). Of these, only figs, pears and plums were eaten and then usually in small quantities; the rest were ignored after being tasted for a few nights. The two females rearing chicks in April-June 1991 drank much water from hoppers, whereas the three other females ignored it. Female A drank an average of 63 ml (+SE=3.86) of water per night. Scraps of food left on the ground included partly eaten items, skin of some foods and chews. A bird was seen to throw pieces of kumara and apple from its tray before eating nut kernels. Because kiore ate these food scraps, no precise measure of the amount of food eaten by kakapo was possible, but we could determine whether or not a kakapo fed at a station on a particular night. We ensured that there was ample favoured food available each night. Frequency of visits to feeding stations During October and November 1989, feeding stations were set up at nine sites and later increased to 14; usually only 12 were in use at any one time. Except for one distant station and on the few days of torrential rain, each station was visited daily to note whether a kakapo had fed at it the previous night, to measure the weight of each food remaining (Powlesland & Lloyd, 1992), to remove food scraps, and to leave weighed amounts of fresh foods. Kakapo are fairly sedentary and solitary, but the home ranges of neighbouring birds overlap (Moorhouse & Powlesland, 1991). Although some birds fed at more than one feeding station per night and some stations were visited by more than one bird per night, the following results are for birds each of which we considered had exclusive access to one or two stations. For the first few months the frequency of visits to stations

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was variable, particularly by females (Fig. 2). However, once a kakapo learned the location of a food station within its home range and how to reach food in it, the bird returned regularly to feed from it. Both sexes fed from stations almost nightly in winter (June-August 1990), but the proportion of nights on which they fed declined from about 100% to about 90% in spring (September-November 1990) (Fig. 2). Kakapo visited feeding stations least often in summer (December 1990--February 1991), when male activity at track-andbowl systems was at its peak (Males A, B and C), and females were mating, laying or incubating (Females A and C). Likewise, when Female C nested in January-February 1990 she visited the feeding station less often (Fig. 2). Radio-tracking of Female D in summer 1990-91 revealed that she did not mate or nest but moved widely, often roosting by day in neighbouring birds' ranges. Both Females A (Fig. 2) and B, when rearing nestlings, fed each night at their feeding stations. The dependence of Female A on supplementary food at this time is evident in her increased frequency of visits per night to both her stations (52%) compared with previously (2-5% per season). Once Female C's infertile egg was removed in late January, her frequency of visits to her feeding station gradually increased to

nearly 100% by autumn (Fig. 2). Similarly, after males had abandoned their track-and-bowl systems in March-April 1991, they fed almost nightly at stations. Weights

Generally, the weights of kakapo prior to the provision of supplementary food on Little Barrier Island were similar to those of non-breeding birds on Stewart Island (Fig. 6 in Moorhouse & Powlesland, 1991). Weights increased significantly after the provision of supplementary food. Weights of breeding birds were not used in the following analyses because they can fluctuate considerably over a short period, particularly those of males (Moorhouse & Powlesland, 1991). The mean weight of seven males increased by 42% from 1.75 kg (+SE=0.04) before supplementary feeding to 2.49 kg (_+0.06) afterwards (Fig. 3(a)) (using the pairedsample t test of Zar (1984), p<0.0003). The mean weight of five females increased from 1.26 kg (+0.02) to 1.72 kg (+0.06), a 36% increase (p<0.0005)(Fig. 3(b)). Breeding

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Although males boomed at track-and-bowl systems during five of seven summers before supplementary feeding began (Table 1), we suspect that no females

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(b) Fig. 3. Weights(kg) ofnon-breeding (a) male and (b) ~male kakapo on Little Barrier Island before and after supplementary ~eding began in September 1989 (indicated by vertical dashed line). bred because no feather clusters from copulations were seen (Moorhouse, 1986; Handford, 1987; Dowding, 1988; Greene, 1989), and no juveniles were found during surveys in the winters of 1986 and 1989 (Veitch, 1986; Hodsell, 1989). By the end of the 1988-89 booming season, 45 track-and-bowl systems were known (Greene, 1989).

During the 1989-90 booming season, the first after supplementary feeding began, kakapo activity at trackand-bowl systems was found daily in the period 21 N o v e m b e r - 1 0 April; booming was heard from 20 December to 27 March (Lloyd & Powlesland, 1990). Thus male courtship in 1989-90 started as early as in 198687, but persisted longer than in any previous season

Table 1. Kakapo breeding activity on Little Barrier Island, 1982-91 Season 1982-83 1983-84 1984-85 1985-86 1986-87 1987-88 1988-89 1989-90 1990-91

Start of activity

End of activity

Booming heard

No. of males active

No activity No -~ Mid-April Yes 3-5 ? Mid-April Yes c. 8 Early January ~ Late April Yes >7 Late December~ Late January No 3-5 Early January a Late March Yes 7-8 Early January~ Mid-March Yes 9 Provision of food supplements began in September 1989 Late December Mid-April Yes 11-13 Early October Late April Yes 10

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Nests found

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"Estimated period when activity started at track-and-bowl systems because activity was evident when the systems were first inspected.

102

R. G. Powlesland, B. D. Lloyd

(Table 1). During the 1990-91 breeding season kakapo became active at track-and-bowl systems earlier and persisted for longer than in any of the previous eight seasons (Lloyd & Powlesland, 1992). Activity was first noted on 1 October and continued until 30 April; booming was heard from 9 October 1990 to 27 March 1991. Kakapo sign was evident at 22 track-and-bowl systems in 1989-90, four of which were newly developed. In the 1990-91 season, sign was detected at 31 systems, including at one new system. During one night a male may use one or several adjacent systems (Powlesland et al., 1992). From their location and the nightly activity at each, we grouped the track-and-bowl systems into 17 clusters, each comprising one or more systems probably used exclusively by a single male per night. The number of clusters used each

night, and hence the number of calling males, was estimated by interpolating between inspections when systems were not inspected every day. The maximum number of calling males at the height of the booming season was 9-13 in 1989-90 and 10-12 in 1990-91 (Fig. 4). During previous seasons there were three-nine males active at the systems (Table 1). Feather clusters, indications of copulations, were found at track-and-bowl systems twice in January 1990, and three times in January 1991. A fourth cluster found in January 1991 was inconclusive because it included 76 contour feathers, compared with 10 or fewer in other clusters.

Breeding by females Two of the four females recaptured during the 1989-90

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Supplementary feeding of wiM kakapo breeding season were found at nests (Females C and E). The other two females (Females A and D) are assumed not to have bred as they were not found at nests and had no brood patches. Neither of the nesting females raised a chick. Female C incubating an egg on 19 February had a dead chick on 21 March (it had died about a week previously when some six days old). Female E was incubating at least one egg on 12 March, but it was abandoned, apparently infertile, on 28 March. Both nests were abandoned during unusually cold, wet weather; it is not known exactly what caused the failures. The two females that nested had fed regularly at feeding stations for three months before mating in January, but it was not until December 1989 and February 1990 that Females A and D respectively began eating supplementary food regularly. By the beginning of the 1990-91 breeding season, the four radio-tagged females had been taking supplementary food for at least 11 months. During the season it became evident that a fifth female had fed from stations for an unknown period previously. Four of these females nested; the fifth did not attempt to nest. Two of the four nests were unsuccessful: one contained an infertile egg (Female C), and the other one infertile and one fertile egg, but the embryo died at about six days of age, probably from chilling (Female E). To encourage renesting, the unsuccessful clutches were removed during early incubation, but neither female did so. Female A laid two fertile eggs in late January. One egg was removed on 20 February so that the chick could be hand-reared. Although it hatched, the chick died when four days old as a result of digestive and respiratory infections. The other egg hatched and the chick x~'as raised successfully. Female B laid three eggs, probably during 19-25 January, two of which hatched; the third was removed intact on 17 March. One chick aged about 30 days disappeared between 22 and 25 March, during heavy rain. The other chick was raised successfully, and fed from a feeding station with its mother in September 1991, four months after leaving the nest. DISCUSSION The fact that kakapo had bred irregularly in Fiordland and on Stewart Island (Henry, 1903; Powlesland et al. 1992) suggested that they might respond positively to supplementary food. Nesting on Stewart Island had coincided with the irregular prolific fruiting of two podocarp tree species, the fruit of which were avidly eaten by the birds (James et al., 1991). Boutin (1990) had shown that the provision of supplementary food to small (<2 kg) herbivorous or omnivorous vertebrates increased the proportion of adult females that bred, advanced the age of first breeding, and advanced and/or prolonged the breeding season. Our concern that wild kakapo might not feed regularly from specially built stations was quickly allayed: within six months the eight targeted kakapo (four females and four males) fed almost nightly on unfamiliar foods (Appendix 1) at unnatural structures (Fig. 1)

103

while standing on raised platforms; and they quickly learnt to reach food by lifting the flaps of food stations and hoppers. Although the kakapo tasted almost all of the 45 foods offered, it soon became evident which foods they ate readily, and which could be supplied year round; we assumed that those with reasonable levels of protein and/or lipids would be required for breeding. In winter both sexes fed from the feeding stations almost nightly (Fig. 2). For females the frequency of visits began to decrease in September, but for males the decline was not until November. Why females fed at stations less frequently in spring than in winter is unknown. Breeding females visited their stations least frequently in January and February 1991: the two breeding females were then absent from their home ranges for two-four nights while mating at track-andbowl systems. During incubation they fed at stations only every second or third night (Lloyd & Powlesland, 1992); this differs from a closely monitored incubating female on Stewart Island, which left her nest to forage nightly for 1-2 h (Powlesland et al., 1992). Radiotracking from near the nests of Females C and E on Little Barrier Island for three nights each suggested that when they did not feed at stations they left their nests only briefly and remained within 50 m of them (Lloyd & Powlesland, 1992). This difference in the frequency of extended absence from the nest during incubation of Little Barrier Island and Stewart Island females suggests that females on Little Barrier Island had greater body reserves because of supplementary feeding; they did not need to be absent for long periods each night in order to find sufficient food. However, once Little Barrier females had chicks they were very dependent on supplementary food and water, taking them nightly. The decrease in supplementary feeding visits per month by Males A and B in early summer (Fig. 2), in spite of one station being within 50 m of each of their track-and-bowl systems, coincided with the males' initial occupancy of the systems for the season (midNovember-December) and when females visited for mating (January). Although it would have been advantageous for males to spend as much time as possible at their systems in early summer (to prevent usurpation by another male and to ensure they were present when a female visited), it seems unlikely that this should have prevented them feeding at the nearby stations at dusk and dawn. These males probably had sufficient body reserves early in the breeding season so that they did not need food supplements each night, or there was sufficient natural food near their systems. Weights of non-breeding kakapo increased significantly with supplementary feeding. The provision of ad libitum food may have resulted in at least one bird becoming obese: Female D weighed 2.1 kg in October 1990, the heaviest of any female (the previous heaviest being 1.86 kg on Stewart Island). She was the only Little Barrier Island female taking food supplements in 1990-91 without nesting. Some captive birds, particu-

104

R. G. Powlesland, B. D. Lloyd

larly parrots, are prone to becoming obese when provided with ad libitum fat-rich foods (Stroud, 1964; Harrison & Harrison, 1986). When kakapo were captured there was no sign of obvious obesity (e.g. bumblefoot or lipomas, Harrison & Harrison (1986)). The main impact of f o o d supplements on male breeding was to enable them to occupy their track-andbowl systems earlier than previously recorded. On Stewart Island (Powlesland et al., 1992) and Little Barrier Island prior to supplementary feeding (Table 1) males occupied their systems in mid-December at the earliest. However, in 1989 on Little Barrier Island one male was regularly active in late November (Fig. 4(a)). In the next season, 12 months after food supplements were first provided, the earliest male (Male C) occupied his system by 1 October, at least two months earlier than usual. By 1 November 1991 a further four males were active (Fig. 4(b)). Even in Fiordland males did not occupy their systems until late November (Merton et al., 1984). Male activity at track-and-bowl systems on Little Barrier Island did not continue later than usual; males abandoned their systems in April (Table 1), as on Stewart Island (Powlesland et al., 1992) and Little Barrier Island before supplementary feeding (Table 1). Thus, some males on Little Barrier Island during the 1990-91 season were active at their systems for five months, compared with only four months for males on Stewart Island in 1985 (Powlesland et al., 1992). In contrast, supplementary feeding by females did not alter the timing of their nesting cycle. Females mated in January in 1990 and 1991 on Little Barrier Island, as on Stewart Island in 1985 (Powlesland et al., 1992). The two Little Barrier Island females whose non-viable clutches were removed during incubation in early February 1991 did not renest although they continued to feed on supplementary food and males were active at track-and-bowl systems until late April. If supplementary feeding could enable female kakapo to renest, then numbers could be increased quickly by removal of the first clutch for artificial incubation and hand-rearing or fostering the brood, while the second clutch could be left for the female to raise. By companson, some large parrots, such as the white-tailed black cockatoo Calyptorhynchus funereus, rarely renest during the same breeding season after failure (Saunders, 1982), but the smaller galah Cacatua roseicapill a commonly does so (Smith & Saunders, 1986). Even though female kakapo did not renest, the impact of supplementary feeding on their breeding was more dramatic than on that of males. Two females nested in 1990, just four months after supplementary feeding started, whereas there was no evidence of any nesting during the seven prior summers (Table 1). In addition, these same two females (plus two others) nested in 1991, the first time that female kakapo have been recorded to nest in consecutive years. Although neither female nested successfully in 1990, the evidence suggests that females may be able to raise broods annually, and that the irregular nesting of kakapo on Stew-

art Island (Powlesland et al., 1992) and in Fiordland (Henry, 1903) was the consequence of poor nutrition. It seems reasonable to conclude that supplementary feeding induced breeding by females. ACKNOWLEDGEMENTS Special thanks to Ian Flux, Terry Greene, Jane Maxwell, Don Merton, John McCallum, Ian McFadden and Hans Rook for leading some field trips and helping on others; to the many Department of Conservation staff and volunteers whose efforts made this study possible, in particular to the Hauturu boat crew, Shaarina Boyd, Alex and Mike Dobbins, Murray Douglas, and Chris and Robyn Smuts-Kennedy; and to John Cockrem, John Gibb and Chris Robertson for constructive comments on drafts of this paper. REFERENCES Boutin, S. (1990). Food supplementation experiments with terrestrial vertebrates: Patterns, problems, and the future. Can. J. Zool., 68, 203-20. Dowding, J. (1988). Report on kakapo booming activity, Little Barrier Island, March-April 1988. Department of Conservation, Wellington (unpublished report). Greene, T.C. (1989). Kakapo booming activity, Little Barrier Island, January-March 1989. Science & Research Internal Report, No. 48. Department of Conservation, Wellington. Handford, P.A. (1987). Report on kakapo booming activity on Little Barrier Island in January-April 1987. Department of Conservation, Wellington (unpublished report). Harrison, G.J. & Harrison, L.R. (1986). Clinical avian medicine and surgery, including aviculture. W.B. Saunders, Philadelphia. Henry, R. (1903). The habits of flightless birds of New Zealand. With notes on other New Zealand birds. Government Printer, Wellington. Hodsell, C. (1989). Kakapo survey Little Barrier Island, 12 September-7 November 1989. Department of Conservation, Auckland. James, K.A.C., Waghorn, G.C., Powlesland, R.G. & Lloyd, B.D. (1991). Supplementary feeding of kakapo on Little Barrier Island. Proc. Nutr. Soc. NZ., 16, 93-102. Kenward, R. (1987). Wildlife radio tagging. Academic Press, London. Lloyd, B.D. & Powlesland, R.G. (1990). Kakapo breeding activity on Little Barrier Island: 21 November 1989-10 April 1990. Science & Research Internal Report, No. 83. Department of Conservation, Wellington. Lloyd, B.D. & Powlesland, R.G. (1992). Kakapo breeding activity on Little Barrier Island: October 1990-June 1991. Science & Research Internal Report, No. 129. Department of Conservation, Wellington. Lloyd, B.D. & Powlesland, R.G. (1994). The decline of ~kakapo Strigops habroptilus and attempts to conserve them by translocation. Biol. Conserv., 69, 000~00. Merton, D.V., Morris, R.D. & Atkinson, I.A.E. (1984). Lek behaviour in a parrot: The kakapo Strigops habroptilus of New Zealand. Ibis, 126, 277-83. Millener, P.R. (1981). The Quaternary avifauna of the North Island, New Zealand. PhD thesis, Geology Department, University of Auckland, Auckland. Moorhouse, R.J. (1986). Report on kakapo booming activity on Little Barrier Island: January-April 1986. Department of Conservation, Wellington (unpublished report). Moorhouse, R.J. & Powlesland, R.G. (1991). Aspects of the ecology of kakapo Strigops habroptilus liberated on Little

Supplementary feeding of wild kakapo Barrier Island (Hauturu), New Zealand. Biol. Conserv., $6, 349-65. Powlesland, R.G. (1989). Recovery plan for kakapo. 1989-1994. Department of Conservation, Wellington. Powlesland, R.G. & Lloyd, B.D. (1992). Supplementary feeding of kakapo on Little Barrier Island, May 1990-June 1991. Science & Research Internal Report, No. 122. Department of Conservation, Wellington. Powlesland, R.G., Lloyd, B.D., Best, H.A. & Merton, D.V. (1992). Breeding biology of the kakapo Strigops habroptilus on Stewart Island, New Zealand. Ibis, 134, 361-73. Roudybush, T.E. & Grau, C.R. (1986). Food and water interrelations and the protein requirements for growth of an altricial bird, the cockatiel Nymphicus hollandicus. J. Nutr., 116, 552-9.

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Saunders, D.A. (1982). The breeding behaviour and biology of the short-billed form of the white-tailed black cockatoo Calyptorhynchus funereus. Ibis, 124, 422-55. Smith, G.T. & Saunders, D.A. (1986). Clutch size and productivity in three sympatric species of cockatoo (Psittaciformes) in the south-west of Western Australia. Aust. Wildl. Res., 13, 275-85. Stroud, R. (1964). Stroud's digest of the diseases of birds. T.F.H. Publications Inc., New Jersey. Veitch, C.R. (1986). Kakapo~Little Barrier--winter 1986. New Zealand Wildlife Service, Wellington (unpublished report). Williams, G.R. (1956). The kakapo Strigops habroptilus, Gray. A review and reappraisal of a near-extinct species. Notornis, 7, 29-56. Zar. J.H. (1984). Biostatistical analysis, 2nd edn. Prentice-Hall.

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Appendix 1. List of foods presented to kakapo at food stations on Little Barrier Island during 1989-91, and the birds' response to each food (unless indicated otherwise, the foods were presented raw and fresh) Food Almond kernel Apple Green Red Apricot, dried Asparagus Avocado Banana Raw Dried Brazil nut kernel Bread Carrot Cashew nut kernel Celery Chick pea, cooked Conditioner fooda Corn on the cob Raw Frozen Cucumber Date, dried Fig, dried Flax seed pod Hazlenut kernel Kiwifruit Kumara Macadamia nut kernel Mung bean, sprouted Nut bar b Orange Parsley leaves Parsnip Peanut butter and 'Roudybush' peUetsc Pear Pine nut Porridge mixd Potato Raw Boiled Baked Pumpkin Cooked seed kernel Roudybush pellets e Sultana Sunflower seed kernel Swede Walnut kernel Yam

Untouched

Tasted, but not eaten

Eaten ,/ ¢ ¢¢

,/ ,/ ¢¢ ¢¢ ,/ ,/ ,/ ¢¢

4

J 4 4 ,/ ,/ 4 4 ,/ ,/ 4 ,/ ,/ ,/ J ,/ ,/ ,/ ¢ ¢ J ,/ ¢¢ 4 ,/ ¢¢ ¢¢ ¢¢ /

J ,/ ¢¢ ¢¢ 4

High protein meal product available from pet shops; mixed with water to a paste and provided to nesting canaries. b Equal portions of crushed almond, brazil nut, walnut and sunflower seed kernals bound together with gelatine or egg and low heat. c Crushed 'Roudybush' pellets mixed with peanut butter. dCooked mixture of rolled oats, crushed 'Roudybush' pellets, soya grits and sunflower seed. e A balanced diet formulated for captive parrots. a