Blue Duck 115

The hand rearing of young Blue Duck

W. J. PENGELLY and JANET KEAR

Introduction part of both mandibles furnished with interlocking lamellae. Iris, dark brown. The Blue Duck Hymenolaimus malaco- Legs and feet, yellowish-brown with rhynchos of New Zealand is an isolated pale digits and darker joints and webs. species of uncertain affinities and is still Body, upper surface dark grey, suf­ largely unstudied, both in captivity and fused with metallic green sheen in the wild. It lives in fast-moving moun­ brightest on the back. Cheeks and tain streams, is apparently insectivorous, under surface, white with a dark stripe territorial, and has a long pair-bond (the through the eye; a vertical dark line male sharing the care of the young), all joins the eye-stripe to the crown. unusual features in the dabbling ducks Wings, dark except for a white line with which it is generally classified. where the secondaries will appear. A In September 1968 a request was made dark band runs along the upper thighs by the Wildfowl Trust to collect eggs to the heel. Tail, rather long and from the wild so that ducklings could greenish above with, at each side, a be hand-reared and later shipped to chestnut dorsal spot; under-tail chest­ England. Permission was granted and a nut. clutch of four was taken from near the The predominantly green, white and Hopuruahine River, North Island, on chestnut colour of these ducklings is 25th November. They were successfully probably unique and is certainly startling. incubated by a bantam hen and hatched In many respects, however, their pattern­ a month later. ing resembles that of the downies of other This paper deals with the development dabbling and perching ducks (see Figure of the Blue Ducks to one year of age. 1). The vertical dark stripe from the eye Aspects of the species’ ecology and sexual to the crown is unusual and found other­ behaviour will be considered in other wise only in Black-headed Ducks Hetero- publications. netta atricapilla (Weller 1968) and Tor­ The attempt to propagate the species in rent Ducks Merganetta (Johnsgard 1966), captivity was a sad failure. One male the taxonomic positions of which are also duckling died at eight days and the other somewhat problematical. at seven months. The females succumbed within a few days of each other at one year old. However, valuable knowledge was gained and it is fortunate that, as the clutch would have been destroyed by a Sexual dimorphism of the ducklings flood that swept the nest-site away, The young birds were sexed, by cloacal nothing was lost from the wild population. examination, and given numbered web- tags at 11 days. It was noted subsequently Downy young that the colour of the dorsal spots dif­ fered in the sexes. In the two males, the Of the published descriptions of the spots were a uniform dark chestnut, young of Blue Ducks, only that of Potts while in the females the down was mainly (1870) is full and accurate. Later accounts pale fawn with only a few chestnut (Delacour 1956; Johnsgard 1965) erron­ plumules. This variability was not seen eously state that the ducklings lack the at hatching and indeed does not clearly dorsal spotting typical of many anatid indicate the sex of the skin of a day-old species, and the illustrations in Phillips duckling in the Wildfowl Trust Museum. (1926) and Delacour (1956) are incorrect However, photographs of the live birds for the same reason. Scott (1958) had, at seven days show the difference quite however, noted the ‘curious golden brown distinctly and a colour picture of wild spot on either side of the back’ of young ducklings reveals the same dimorphism. Blue Ducks in the wild. Further material is obviously required. The following description is an ampli­ This feature as an indicator of sex appears fication of Potts’ (1870): to be unique, but has probably never been Bill, greyish-blue lightest on the lower looked for in other waterfowl, where in mandible and rosy at the tip; mem­ any case it would hardly be obvious as the branous appendage, slaty black, well spots are normally pale, like the under­ overlapping the lower mandible, basal parts. 116 Wildfowl

Figure 1. Downy young of the Blue Duck.

Table I. Feather growth in young Blue Duck. Age in days 24 Scapular feathers out of sheaths, but still beneath down. 26 Scapulars, underwing coverts and tail feathers showing through down. 29-31 Secondaries out of sheaths. 32 Feathering on face. 33 Crown of head well feathered. 36 Primaries out of sheaths. Belly almost completely feathered. 41 Head, neck and body nearly fully feathered. Down remaining on mid-back, lower neck and flanks. Primaries and secondaries not yet visible between the wing coverts. 46 Down visible only on mid-back. 48 Secondaries appearing from wing coverts. Dorsal spots losing definition. 56 Considered fully feathered, although traces of down could still be found at 97 days. Wings short, primaries barely longer than inner secondaries. 70-77 First flights. Figure 2. Juvenile Blue Duck in first plumage.

Feathering At six months, full adult plumage had The first contour feathers were noticed been attained; the bill was turning white breaking from their sheaths beneath the and the iris distinctly yellow. At one year, down at 24 days. Table I shows the stages the eyes were as golden as those of the of feather growth. The juvenile first adult, but the dark streak along the bill plumage (see Figure 2), which lasted from was still not completely eliminated (see 8 to 20 weeks, was lead grey, with Plate XHa facing p. 97). brownish shading on the wing coverts In July, a single adult male in the and heavy dark brown spotting on breast Slimbridge collection, and the two juve­ and shoulders. The undertail coverts were nile females, all moulted their wing ginger, but otherwise the chestnut pat­ feathers. The young birds were now only terning of the adult was absent. The bill six to seven months old and it seems pos­ was light blue-grey, with a dark grey sible that in New Zealand the first change band from the culmen to the nail, and of flight feathers would have occurred the eyes were dark brown. not at this stage, but when the ducks Relative weight 14 - 15 16 measurements 8 male m X 18 Figure 3. Relative growth curve of Blue Ducks (hatching weight equivalent to 1.0). to equivalent weight (hatching Ducks Blue of curve growth Relative 3. Figure eitl uo arvl t lmrde they Slimbridge at arrival upon mediately linear and weight body in Changes (Ogilvie days period 27-28 of incubation period long incubation long a a with waterfowl, related In 1953). Boyd (Scott days 56 and and 49 dabbling between achieved is temperate with comparison usual. the than poses earlier acquired other been the have to in change hemisphere suspected tem­ This for age species. normal perate old—the year a were Until they were nine weeks old, the young young the old, weeks nine were they Until cor­ be to tendency a has period fledging the in Flight latitudes. Mallard higher from ducks possi­ will interesting this habitat deny natural bility. or the confirm in also Observation may plumage adult whether one question from shift a after pattern wing-moult id wr wihd lot al. m­ Im daily. almost weighed were birds ducks. the dabbling of one among it making longest an unpublished), (Kear has Mallard the Thus 1968). (Lack 1964) and the Blue Duck of 31-32 days days 31-32 of Duck Blue the and 1964) 118 2 - The rate of feather growth is slow in in slow is growth feather of rate The -\ x 10 0 ns platyrhynchos, Anas X for instance, instance, for X

es f age of eeks W Wildfowl al I. vrg wih i gas of grams in weight Duck. Average Blue II. Table * acig49 Males Hatching (zveeks) Age 3 Figure and intervals, weekly at weight another to moved was she when weighed old. Subsequently, a single female was was female single a not Subsequently, could old. and quarantine in placed were aviary. Table II shows average body body average shows II Table aviary. 14weeks were they until again handled be 2 id utlti age, this until birds dl 8 750 887 Adult 23 485710* 805 14 0 623 708 368 9 7 6 4 3 2 8 5 438 450 5 1 range 753-1,077 range (8 20 birds) 246 677 612 519 4 143 142 4 Adult 24 — 66 * 1 thereafter. • fmale fem • $ range 680-850range (5 birds) Females 241 742 346 619 519 582 73 48

Blue Duck 119

shows the relative growth curve, with especially at shiny green and yellow hatching weights adjusted to 1.0. Adult objects which moved. The facial stripes, weights are from Kear (unpublished). obscuring and protecting the small At hatching Blue Ducklings are larger shining eyes, and pale bill tip, contrasting than young Mallard, which weigh about and attractive, both suggest a pecking 35 gm. (Kear 1965), although adult Blue habit. Duck average some 200 gm. lighter. This For the first ten days the birds were phenomenon of relatively large eggs and given a turkey-starter meal, sieved egg- young is general among New Zealand yolk, duckweed Lemna sp., chopped waterfowl. The growth curve is, however, earthworms Eisenia or Allolobophora sp., less steep than that recorded from higher maggots, flies, woodlice Porcellio sp., latitude ducks, such as the Mallard chopped bivalve molluscs Amphidesma (Southwick 1953) or the Tufted Duck sp., and quartz grit. From 16 days their Aythya fuligula (Kear 1970)—another diet consisted of earthworms (about 20 feature common in New Zealand ducks. a day each until they were 30 days old), Apart from the bill length, very few starwort Callitriche sp., and chick- linear measurements were made because starter ‘Niblets’ (a commercial meal in of the danger to the birds of prolonged crumb form). handling. Some are given in Table III. Live food was preferred but good quan­ As far as these go, they indicate that, tities of ‘Niblets’ were taken, especially as except in weight, the birds are almost the birds grew. As well as pecking, they full-size at 14 weeks. Certainly the leg used various other feeding methods. They in many waterfowl develops quickly, ‘burrowed’ a great deal, even at two days presumably an adaptation to life on fast old, pushing the bill into crevices (in the flowing water. Weller (1957), Dzubin lawn, for instance, or under stones, or (1959) and Kear (1970) all found that in between human toes) and moving it

Table III. Average measurements in millimetres of Blue Duck.

Hatching 1 week 14 weeks Adult <5 9 c? 9 Head (biU tip to back of skull) 44.2 48.0 91.4 84.8 91.7(4) 86.2(6) Tarsus length 23.3 25.8 50.7 47.5 49.8(4) 47.0(4) Tarsus thickness 1.8 2.2 4.6 4.6 4.8(4) 4.7(5) Wing — — 225 215 233(4) 217(3)

diving Aythya species, the tarsus reaches Table IV. Culmen length in millimetres full length between six and eight weeks. of Blue Duck. Changes in the length of the bill (ex­ posed culmen) are shown in Table IV. These data suggest that growth is rapid Age in days d Not sexed 9 to 63 days but relatively little occurs after hatching 15.3 that, although the culmen does lengthen 8 18.3 slightly after the flying stage is reached. 17 24.7 Similar curves for bill growth are found 22 28.2 28.0 in other ducks (Weller 1957; Dzubin 28 31.0 30.0 1959). 35 34.0 33.4 42 36.1 35.4 49 38.5 36.3 Feeding 56 40.0 38.3 63 41.6 39.1 Persuading the ducklings to feed was no 97 43.4 39.7 problem and they started gaining weight during their third day. Like other young adults 44.0 40.8 dabbling and perching ducks, they initi­ range 42.3-45.1 range 40.3-41.6 ally pecked at small objects nearby and (4 birds) (6 birds) 120 Wildfowl rapidly from side to side. Woodlice were and it may be a serious predator of the discovered beneath debris in this way. species in some places in the wild. On the Maggots and other preferred titbits mixed 26th day, the sight of a visitor in a bright with meal were found by pulling the bill orange frock again apparently panicked backwards through the food. Items were the birds, which rushed into their coop also successfully sieved by sucking food and did not emerge until the woman had and water in at the tip of the bill and left. squirting the water out at the sides of the The ducklings themselves were a close- mouth. The vacuum-cleaner action of knit group up to the time they were sucking food off rocks, described by Scott separated into pairs, in adult plumage, at for the adults, was not seen, probably 23 weeks. Aggressive action was never because of the artificial rearing situation. obvious. They did a great deal of nib­ At 10 days the ducklings were eating bling at each other’s heads and faces and whole earthworms by picking up one end were still sleeping touching each other at and shaking them from side to side as 10 weeks (a behaviour that normally they slipped further down the throat. At ceases at fledging). 30 days, on the first of many subsequent The voice of the young birds was typi­ occasions, the birds were seen doing a cal of those of dabbling ducks (Kear 1968, little grazing in a Mallard-like fashion. and unpublished). The contact call was a At 125 days they were first noticed diving rapid two- or three-syllable sound and the to the bottom of their pond for food. distress call consisted of slower notes, resonating at a higher frequency. No Other behavioural changes trills were heard, but a slurred sleepy call was given rarely, when the ducklings The bantam proved an admirable foster­ were under the hen at night. At 33 days parent; she and her family did a great the voice was starting to change, that of deal of travelling by car and plane before the females becoming more guttural. The hatching and during the first two weeks rasping quack of the adult female was and she never lost her calm demeanour. obvious at 10 weeks, at a time when the The ducklings imprinted well and re­ drake was still contact calling, but by 14 sponded to at least some of her calls. weeks a clear whistle was his normal They froze at her alarm note, apparently greeting. As Phillips (1926) surmised, without previous learning, but did not Buller (1882) was incorrect in attributing respond initially to her feeding clucks, the whistle to the female, a misconcep­ although they were associating these with tion still apparent 80 years later (Child food by 16 days of age. By the fifth week 1961). the hen was losing interest and on the A good part of the ducklings’ day was 44th day was seen attacking them, so was spent preening and oiling their down and removed. feathers, and the appearance of the As might be expected in a species various comfort movements corresponded evolved in a land without indigenous almost exactly with that described for the mammals (except seals and bats), the Mallard by McKinney (1965). ‘Dashing ducklings were relatively tame and readily and diving’ in water, which in Mallard accepted the presence of human beings. appears at 13 or 14 days, was first noted Indeed, they soon learnt that people were in the Blue Ducks at 16 days, so it is very efficient providers of food, took many possible that development was slightly titbits from fingers and, on excursions to slower at this age. look for woodlice, followed the humans At walking, running and swimming the more closely than their foster-mother. Blue Ducklings were as adept as any They remained tame and frequently waterfowl, at jumping and climbing they called to and approached visitors at were superior to most dabbling ducks. Slimbridge. Their lack of fear was not They climbed using their chins rather absolute, however, and they were still than their toes as perching ducks do, freezing at sudden sounds at three weeks indeed their claws were not especially of age. On the 21st day their reaction to sharp. By six days they were jumping a stuffed and mounted Stoat Mustela five or six inches straight up and at ten erminea was tested (the hen having been days, nine inches. In jumping, their removed). The effect was immediate and chestnut under-tails became particularly they rushed to the end of their coop in an obvious, and it seems likely that both apparently alarmed condition. Adult Blue their leaping abilities, and the flash of Ducks in captivity show little response colour as they moved, have adaptive to this mammal (which was unfortunately value in the wild where they must nego­ introduced into New Zealand in 1885) tiate rock-strewn pools, their cries often Blue Duck 121 drowned by the thundering water around National Park. Mr. T. H. Steel found the them. nest and helped in numerous ways. Incu­ bation by a bantam was arranged through Acknowledgements Mr. P. R. Fisher and Mr. J. S. Standring, and Mr. C. D. Roderick allowed the birds The Wildfowl Trust is extremely grate­ to be cared for at Mount Bruce Native ful to the many people who assisted this Bird Reserve, from 4th January to 26th study. The Wildlife Service, Department February 1969, when they were sent by of Internal Affairs, Wellington, New air to Slimbridge. Zealand, and the National Parks Auth­ The drawings of the downy young and ority (Head Office) gave permission for the juvenile bird were prepared by the eggs to be removed from the Urewera Robert Gillmor.

Summary This paper deals with the captive rearing of a brood of Blue Duck Hymenolaimus malaco- rhynchos in New Zealand and England. The duckling is not without dorsal spots as has been previously stated and, indeed, a possible sex-linked colour difference in these structures was discovered. Development in feathering, weight and bill length was slower than in ducks which breed at higher latitudes. Feeding, preening, vocalization, locomotion and social behaviour are described. Excellent jumping abilities and the vivid undertail colouring are considered adaptive to the wild situation.

References b u l l e r , w. L . 1882. Manual of the Birds of New Zealand. Wellington. c h i l d , p . 1961. Female Blue Duck apparently paired with Paradise drake. Notornis 9 : 170. D E LA C O U R , J. 1956. The Waterfowl of the World. Vol. 2. London: Country Life. DZUBIN, A. 1959. Growth and plumage development of wild-trapped juvenile Canvasback (Aythya valisneria). J. Wildl. Mgmt. 23 : 279-90. JOHNSGARD, P. 1965. Handbook of Waterfowl Behavior. Ithaca : Cornell University Press. j o h n s g a r d , p . 1966. The biology and relationships of the Torrent Duck. Wildfowl Trust Ann. Rep. 16 : 66-74. KE A R , J . 1965. The internal food reserves of hatching Mallard ducklings. J. Wildl. Mgmt. 29 : 523-8. K E A R , J . 1968. The calls o f very y o u n g Anatidae. Die Vogelwelt 1 : 93-113. K E A R , j. 1970. Studies on the development of young Tufted Duck. Wildfowl 21 : 123-32. l a c k , d . 1968. Ecological Adaptations for Breeding in Birds. London : Methuen. MCKINNEY, D. F. 1965. The comfort movements of Anatidae. Behaviour 25 : 120-220. OGILVIE, M. a . 1964. A nesting study o f Mallard in Berkeley New Decoy, Slimbridge. Wild­ fowl Trust Ann. Rep. 15 : 84-88. PHILLIPS, J. C. 1926. A Natural History of the Ducks. Boston : Houghton-Mifflin. p o t t s , T . H . 1870. On t h e birds o f New Zealand. Trans. N.Z. Instit. 2 : 40-80. s c o t t , p. 1958. Notes on Anatidae seen on world tour. Wildfowl Trust Ann. Rep. 9 : 86-112. s c o t t , p . and H . b o y d . 1957. Wildfowl of the British Isles. London : Country Life. s o u t h w i c k , C . 1953. A system of age classification for field studies of waterfowl broods. J. Wildl. Mgmt. 17 : 1-8. w e l l e r , M . w. 1968. The breeding biology of the parasitic Black-headed Duck. Liiing Bird 7 : 169-207. w e l l e r , M . w. 1957. Growth, weights and plumages o f the Redhead Aythya americana. Wilson Bull. 69 : 5-38.

W. J. Pengelly, Wildlife Service, Department of Internal Affairs, Wellington, N.Z. Dr. J. Kear, The Wildfowl Trust, Slimbridge, Gloucester, GL2 7BT, England.