BREEDING 101

ranged from 38-58 days; the average age was 46 days.

Ruddy ducks are highly aquatic. From as early as one day of age, they remain in the water most of the time, sifting small food items through their bills as they swim. The types of foods provided may not be as critical as the method of presentation. Food floating in the water is more readily ingested by the ducklings than the same food provided on land. The size of food is also important, finely chopped and ground duck pellets or trout chow being easier for ducklings to eat than whole pellets, even if the latter are softened in water.

It appears therefore that access to water adequate for swimming and diving, which allows immediate swimming activity and food consumption, is the most important survival factor. Replication of these rearing methods will determine whether successful results will be consistent. Furthermore, the methods de- scribed may provide an important contribution to other captive breeding programmes not only for the Ruddy duck but other highly aquatic species as well.

ACKNOWLEDGEMENT

Recognition is due to John Mallen, Biological Technician, for his assistance and contributions to the success of the programme.

PRODUCTS M E N T I O N E D IN T H E T E X T Betadine: disinfectant, manufactured by Purdue Frederick Co., Norwalk, CT06856, USA. Marsh Roll-X Automatic Incubator: manufactured by Marsh Manufacturing Co., Inc., Garden Grove, CA 92643, USA. Purina trout chow and duck breeder pellets: manufac- tured by Ralston Purina Company, St Louis, MO 63188, USA.

REFERENCES APPLETON, T. P. (1975): A note on a water tank for hand-rearing stifftail ducklings. Int. Zoo Ylh. 15: 236237. BELLROSE, F. c. (1976): Ducks, geese and swans of North America. Harrisburg PA.: Stackpole Books. JOHNSGARD, P. A. (1975): Waterfowl of North America. Bloomington: Indiana University Press. SIEGFRIED, w. R . (1 973): Post-embryonic development of the ruddy duck Oryura j . jamaicensis and some other diving ducks. Int. Zoo Yb. 13: 77-86.

Manuscript submitted 8 June 1980

History of captive management and breeding of Bald eagles

a t the National Zoological Park Haliaeetus leucocephalus

SHERYL GILBERT', PAUL TOMASSONI* & PAMELA A. KRAMERZ IKeeper Leader and lKeepers, Department of Ornithology, National Zoological Park, Smithsonian Institution, Washington, DC 20008, USA

There have been no consistently favourable captive breeding results for Bald eagles Haliaeetus leucocephalus although isolated in- stances of breeding are recorded as early as 1885 (Hancock, 1973; Maestrelli & Wiemeyer, 1975). Recently undertaken breeding pro- grammes, especially the larger scale efforts at USDA's Patuxent Wildlife Research Center, promise greater success (S. Wiemeyer, pers. comm.).

In the summer of 1973 a pair of Bald eagles at the National Zoological Park successfully hatched and reared a chick in their first breeding season in captivity (Johnson & Gayden, 1975). Surprisingly, no further young were hatched despite the pair's apparently normal reproductive behaviour, i.e., courtship, nest building, copulation, laying and incu- bation. In an attempt to improve the situation a number of management changes were made

BRtF.DING 102

and in the summer of 1978 a second chick was successfully hand-reared after artificial incu- bation. This report covers the history of our Bald eagle breeding efforts together with the methods used to hand-rear the chick.

BREEDING ATTEMPTS, 1973-1979 With the exception of 1979, the eagles have each year produced two clutches, each consist- ing of two eggs: the first in February or March and the second in April or June. T h e birds always appear willing to incubate the eggs, and from 1973-1975 they were left to do so undisturbed. Of the ten eggs in five clutches laid over this period, nine disappeared from the nest with only a few shell fragments remaining, and the tenth was hatched in 1973.

From 1976-79 a total of 15 eggs was removed from the nest leaving the adults with four to incubate themselves; unfortunately, three of these were lost with the fourth spoiling after five weeks. Eggs taken from the nest were candled after two weeks and 13 were found to be infertile; the birds' ages, which were unknown, may have been an influencing factor here. In 1976 an egg was sent to the Patuxent Wildlife Research Center (Fish and Wildlife Service, US Department of the Interior) in Laurel, Maryland, where its infertility was confirmed. We were informed that had the egg been fertile it could have hatched, having low levels of organochlorines and a shell thickness only 22'10 below the pre-1976 norm (repre- senting normal egg dimensions unaffected by pesticides). The remaining two fertile eggs were laid in 1978 and 1979; the former hatched, while the embryo in the latter died shortly before pipping.

Eggs not incubated solely by the adults were removed from the nest either when a clutch was completed or part-way through parental incu- bation. In 1979 no natural incubation was permitted and each egg was removed on the day of laying which, incidentally, resulted in the 9 laying seven eggs in rapid succession.

In January 1978, as in the late mid-winter of each preceding year, the aviary was supplied with a bundle of sticks 30-100 cm long and a quantity of straw. In addition, as in 1973 the parents and chick had been observed panting under the hot sun, a sunshade made of opaque

plastic sheeting measuring 1 x 1 . 5 m was placed on the cage roof directly over the previous year's nest which was located in the upper rear right-hand comer. Six days later nest construction began with the eagles demonstrating, as always, a clear division of labour, the d carrying sticks while the 9 worked on the nest itself. Rather than adding to their familiar nest, however, they began build- ing another one in the right front comer of the cage where there was no underlying plat- form to support the structure. This continued until late February when the sunshade was removed; two days later the eagles were back on the original nest site where building proceeded normally. T h e rejection of the sunshade was unexpected since a pair of captive Bald eagles a t Patuxent is reported to have accepted the installation of a similar protective screen (Maestrelli & Wiemeyer, 1975) and Bald eagle nests in the wild are frequently sheltered by leaf canopies, with such locations being consistent with fledging success (Hancock, 1973).

After ten days the Q was spending much time at the nest which was now 100 cm in diameter and 50 cm deep with an oval depression measuring 25 x 15 x 7 . 5 cm deep situated slightly off centre. Three days later the first egg was laid and immediately removed, weighed and dipped in a 10% solution of Betadine to disinfect the shell. Two more eggs appeared after intervals of two and five days; both were removed a couple of days later and treated with Garasol (gentamicin sulphate), an antibiotic dip developed for the poultry industry which penetrates the shell and kills bacteria inside.

INCUBATION AND ACCOMMODATION The eggs were placed in a Roll-X incubator with a dry bulb temperature of 37.5"C, wet bulb 30°C, in which they were automatically rotated 70" every two hours. O n the day of laying a pattern of decreasing weights was determined, with the egg laid first being the heaviest and the third being the lightest - a pattern repeated in 1979 when six eggs were laid and weighed 123 g, 116g, 1 1 0 . 5 g , 107.5 g, 100 g and 85 g. Each egg was weighed daily to measure weight loss resulting

B R E E 0 IN G 103

Eggweights (g)

- Weights Recorded

1M-- *"". Weights Nat Recorded 0 Pipped& ._-. ....... 112--

......... Hatched-

108

.........

102 .... ......... .....

Infertile xx)

98 ......... 96-- 94

92--

--

90 I I I I 1 I I I I I I I I I

0 5 lo 15 20 25 30 35 40 nse (days)

Fig. 1. Weight loss ofthree Bald eagle Huliueetus leucocephulus eggs during artificial incubation.

from evaporation and metabolic activity (Fig.

The density of the eggs made them difficult to candle, but it soon became apparent that only the third egg - also the smallest, lightest and least opaque-was fertile. Its weight loss was slightly greater than that of the other two.

On day 33, when the vocalisations of the chick could be heard distinctly through the shell, the turning mechanism of the incubator was disconnected and the humidity gradually increased until it reached a wet bulb temper- ature of 32°C on the day of pipping. In late April, 35 days after it was laid and 24 hours after pipping, a grey, downy chick hatched. It weighed barely 70 g, had a long thin neck, a relatively large head, a distinctive hooked beak and surprisingly small feet. A subcutaneous injection of gentamicin sulphate was given a few hours after hatching, a procedure NZP used routinely in 1978 on hatchlings vulnerable to infection immediately after having broken out of the shell. The chick was left in the incubator to dry until the next day.

Initially the eaglet was housed in a glass- sided hospital incubator developed for human infants; in this isolette it was possible to keep

1). the environment relatively free from contami- nation, to maintain control over temperature and humidity and to observe the bird without disturbing it. The temperature was first set at 32"C, then gradually decreased to room tem- perature (25°C) over two weeks with the humidity being decreased concurrently to slightly above ambient.

At first, the bottom of the isolette was covered with indoor-outdoor carpeting, but by day 6 the eaglet's legs were becoming splayed. The chick was therefore moved to a stainless steel bowl 13 cm in diameter which was lined with cheesecloth and steep sided to ensure that the legs were kept well under its body.

On day 12 the eaglet was transferred to a bowl 18 cm in diameter to prevent accidental choking, since it was now large enough to hang its head over the sides of the bowl. After it had outgrown this and another larger receptacle it was moved back onto the carpeted floor of the isolette and although this was covered in a layer of twigs to provide a less slippery, more uneven surface, the eaglet failed to grasp with its talons as expected.

When it was four weeks old the young eagle was transferred to a floor pen c. 1 mz, followed

104 BRF.F.DING

BREEDING 105

two weeks later by gradually increased periods in an outdoor enclosure of about the same dimensions. As the weather became warmer it remained outside for up to eight hours a day, sitting on the thick lawn which formed the floor of its enclosure. At two months, when it was about two thirds grown and still flightless, the bird was placed on exhibit in a corn crib cage 3 m in diameter and 7 m high where it would sit at the back on a pile of leaves. Because of its health problems, however, it was returned to the Bird House until autumn.

DEVELOPMENT The eaglet was weighed daily on a triple-beam balance scale (Fig. 2) until day 32 when it was found to have outgrown the basket with which the scale was fitted. Weight was subsequently measured with a hanging scale at irregular intervals. T h e rate of growth suggests a possible error in the calculated age of an eaglet found in the wild in 1970 (Stewart, 1972) which was said to be one week old; it weighed 347 g, a size the N Z P bird did not reach until day 17.

At hatching the chick’s feet were small, soft and limp with no ability to grasp or to support its body weight, so for several weeks it either rested on its abdomen or sat on its hocks, though it was observed to move forward, still on its hocks, on day 17. T h e feet continued to grow slowly and on day 31 they were strong enough to permit standing for a minute or two at a time. The bird finally stood firmly on day 50, which agrees with the age at which a parent-reared chick at Patuxent was first observed standing in the nest (Maestrelli & Wiemeyer, 1975).

T h e body was covered with light grey down until it was three-and-a-half weeks old. Behaviour associated with preening was observed soon after hatching with the bird rising onto its hocks, stretching its body and flapping its wings two or three times. O n day 8 the eaglet was able to remain sitting for a few seconds while it preened a wing. The pin feathers appeared first on the body and then, about two weeks later, on the head and wings. When the primaries were half grown, around day 47, the bird began to exercise its wings, doing so for longer periods every day. Its first

Plate 1. lefr Ten-day-old Bald eagle chick; right month-old bird in moult. O&e of Graphia d Exhibits, National Zoological Park.

I06 BREEDING

flight, from the floor to a perch 1 . 2 m high, took place on day 77 which is consistent with fledging dates observed in the wild (Herrick, 1933), though much earlier than the chick hatched in 1973 which fledged at 91 days.

At the peak of its first moult, the bird lost interest in food: its intake reached a plateau and its weight gain gradually slowed - a phenomenon observed in other moulting birds (Stewart, 1972).

FOOD AND FEEDING Apart from one incident, feeding presented no problems; food intake was recorded daily and

frequency (k Hz)

C

1

d

e

I 1

time (sec)

the bird’s appetite was guod. By day 6 it was displaying a typical begging posture when hungry which involved the beak pointing up- wards, the mouth open and the neck stretched; a begging call consisting of a series of tonal peeps, lower in pitch than later calls (Fig. 3), accompanied the posture.

T h e staff nutritionist at NZP formulated a meat-based diet which conformed to the nutrient requirements of starting poultry chicks (NRC, 1977) except that it was cor- rected to the higher energy level of a meat-oil diet (Table 1). It contained raw chicken breast with added supplements to overcome the nutrient imbalances and deficiencies in raw meat (Table 2). High levels of vitamins A, D and E were included to cover possible deterior- ation of these vitamins in the oils used and because the requirements of a carnivorous fish-eating bird may be greater than those of a chicken. There may have been a deficiency in manganese (4 ppm) because the supplements available for use at the time contained only low levels, but the diet was otherwise found to be adequate.

Initially, the eaglet was given six to eight meals a day, in contrast to feeding methods used in the rearing of an eagle chick in 1970 when two meals were fed daily (Stewart, 1972). Fillet of trout was added to the diet on day 10, and baby mice on day 15. During this same period the chick began approaching its food

Fig. 3. Development of call of Bald eagle chick. a. day 1 (19 April), simple rising or rising and falling short tonal sounds, with little range in frequency and lower in pitch than later recordings (f 2-3.5 kHz, duration 0 33 sec). Cry given when eaglet approached by the microphone; b. day 10, long (0.5-055 sec) quavering tonal sounds, rising in pitch then flattening before final fall. New characteristics included rapid frequency modulation (9 kHz for 0.4 sec) and a non-harmonically related ‘mirror’ tone (two simultaneous voices), in the last two-thirds to three-fifths of each sound, of slightly lower pitch than the loudest component If346 kHz); c. day 15, frequency range remaining the same but the two voices heard both separately and combined. More harshness in the mid- or end-portion of call (seen in the vertical beat-interference lines) (f 2.3-5 kHz, duration 0.6 sec). d. and e. day 30, more variation in tonality, harshness and duration (04-07 sec), sharp ‘chirp pulse at end of each note giving quality very similar to adult call (f3-7 kHz).

BRELDING 107

INGREDIENT SOURCI: OF APPROXIMATE AMOL VTS

MADE PER FEEDING

Chicken breast (later replaced with trout flesh and other meats)

Cod-liver oil

Wheat germ oil

Cal-Phos powder

Vionate powder Minerals and vitamins

Energy, protein, some vitamins and minerals

Vitamins A and D,, essential

Vitamin E, essential fatty

Calcium 32%, phosphorus 14.5%

fatty acids

acids

by weight

10 g

0 . 0 5 ~ ~

0 . 0 5 ~ ~

150 mg

100 mg

Table 1. The starting diet for the Bald eagle chick.

UNITS CALCULATEDLEVEL (DRY MATTER BASIS)

DESIRED LEVELa (DRY MATl'LR UASIS)

Protein Fat Calcium Phosphorus Zinc Manganese Iodine S e 1 en i u m Vitamin A Vitamin D, Vitamin E

% Yo

% % PPm PPm PPm PPm i d k g iu/kg iu/kg

78 10 2 .1 1 . 7

80 4 1 . 4 0 . 4

20000 2000

45

40 1.6b 1 . 4 1 . 1

60 8OC 0 .6 0 . 2

10000 1000

40

abased on NRC (1977) levels for starting chicks multiplied by 1 . 5 to correct for higher energy content (approx. 45 kcal/g) of meat-based diet. Increased levels of vitamins A, D and E selected on basis of NRC (1978) levels for cats. bas essential fatty acids. This diet contains at least 2% essential fatty acids from the added oils Cestimate probably high because availability of manganese in meat diet is greater; cat requires 10 ppm (NRC, 1978).

Table 2. Selected nutrient levels in Bald eagle chick diet.

dish rather than remaining passive when food was placed in front of it; shortly after, it was picking food up by itself and no longer required hand-feeding. Three weeks later the chick stopped displaying the begging behaviour but instead adopted what may be termed a sub- missive posture whenever it was approached: the wings were partly open and curved forward, the neck stretched forward slightly below shoulder level and the beak pointed upwards while the neck bobbed up and down; a softer call was uttered which was still much rougher and lower in pitch than the typical whistle of an adult eagle. Starting at four months the eaglet

was fed Nebraska brand bird of prey diet along with trout, rats and adult mice cut into large pieces, with Vionate powder as a supple- ment. It regurgitated its first pellet on day 33. In its 14th month live food was sometimes pro- vided, principally baby chicks which were readily despatched and eaten.

HEALTH Apart from an initial illness, the chick appar- ently thrived for five weeks but then suffered continual bad health from the age of five weeks to four months, a fact that demonstrates these

1 ox BREEDING

birds’ susceptibility to disease while highlight- ing the gaps in our understanding of health problems in large raptors.

T h e first illness occurred on day 8 when from 0700 hours onwards the eaglet refused all food, regurgitated most of the tube-fed Ringer’s solution and became gradually weaker. Finally, at 1700 it was force-fed one small piece of chicken which it retained, and by 1800 it had regained enough strength and appetite to swallow two more pieces, its condition then improving rapidly. T h e following morning it was found to have lost 3 6 . 4 g, i.e., 21% of its body weight. The cause of the incident remains a matter for conjecture, but the symptoms resemble those described as characteristic of ‘foul crop’ (Olendorff, 1972), a condition caused by over-feeding excessively dry food leading to an impaction of the crop and spoilage ofthe food within.

On day 28 a nodule, 75 mm in diameter, was discovered, directly above the left eye. An incision was made and a caseous plug was removed from the frontal sinus; antibiotics were administered and the wound quickly healed.

Four days after the appearance of the nodule, the eaglet developed cataracts in both eyes and was examined by a veterinary opthal- mologist who prescribed no treatment apart from the antibiotics already being adminis- tered. Although the cataracts did not dissipate for three weeks, the bird showed no obvious sign of visual impairment; i t had no trouble locating its food dish and responded normally to the presence ofkeepers. On day 33, however, it began to bite its feet. A 3 4 - c m layer of straw spread over the floor of the cage and covering the feet appeared to effectively discourage the behaviour which did not recur after day 41. T h e cause has not been identified, but is unlikely to have been hunger since foot biting seemed to occur as much after meals as before but it is thought that the cataracts may have been bad enough to prevent the eaglet from distin- guishing its feet from other moving objects.

On day 44 it started breathing with a rasping sound and its mouth open; the symptoms appeared most pronounced indoors when the bird was exposed to air conditioning and con- tinued for ten days. Miconazole, an anti-

fungal drug, was administered for one week as a prophylaxis against aspergillosis.

O n day 65 the eaglet was found to have ruptured a tendon of the cranial tibia1 muscle in the right leg and corrective surgery was immediately attempted by an orthopaedic surgeon. T h e leg was put in a cast but after a month the bird was still unable to use it for support. Ankylosis of the right tibiotarsal joint was diagnosed and further surgery was per- formed; eventually the bird could land and lean, although its use of the talons was limited, and the leg could not bend at the joint. After the cast was removed the bird slowly adjusted to its handicap but continued to favour the right leg.

When the young eagle was a year old a laparoscopy showed it to be p . In the autumn of 1979, out of concern for the handicapped leg which might cause suffering in cold weather, she was placed on breeding loan with the National Wildlife Rescue Team in Miami, Florida, where it is hoped she will contribute towards the current breeding programme.

I C K S OW I. E DG E ME NT S The following staff members at the National Zoological Park made contributions either to the rearing of the young eagle or to the writing of this paper: Department of Ornithology: Dr Gene Morton, Curator, recorded the bird’s calls and analysed the sonograms. He also read and reviewed the paper most thoroughly and made many help- ful suggestions. Charles W. Pickett, Ornithologist, was most instrumental in designing a management plan for the adult Bald eagles, putting emphasis on artificial incubation after natural incubation had failed repeatedly. John W. Mallen, Biological Technician, contributed many practical suggestions for incubation and hand-rearing. Department of .4nimal Health: Dr Mitchell Bush, DVM, was respon- sible for the eaglet’s daily health care and contributed infor- mation from his records for this paper. Department of Zoological Research: Olav T. Oftedal, Nutritionist, contri- buted all information concerning the eaglet’s diet, including the analysis of the nutritional contents of the food. Dr Stank)- Wiemeyer, Research Biologist in the Terrestrial Ecology Project at Patuxent Wildlife Research Center, Laurel, Maryland gave unstintingly of his experience in the captive management of Bald Eagles in numerous conver- sations concerning the method of incubation and the hand- rearing ofour Bald eagle chick.

PRODK C T S , M k N T I O h E D I N T H E T E N T Betadine: disinfectant, manufactured by Purdue Frederick Co., Nonvalk, CT06856, USA. Cal-Phos powder: manufactured by Veterinary Laboratories. Inc.. Lencxa, KS 66216, USA.

BREEDING 109

Bird-of-Prey diet: Nebraska brand, manufactured by Central Nebraska Meat Packing, Division of Allied Mills, Inc., North Platte, Box 550, NE 69101, USA. Garasol: a brand of gentamicin sulphate veterinary for turkey egg dipping (used at a conc. of 250 ppm), manu- factured by American Scientific Laboratories, Schering Co., Madison, WI 53701, USA. Miconazole: anti-fungal drug, manufactured by Janssen R-D, Inc., New Brunswick, NJ 08903, USA. Roll-X Automatic Turning Incubator: manufactured by Marsh MFG., Inc., 14232 Brookhurst Street, Garden Grove, CA 92643, USA. Vionate: vitamin/mineral powder supplement, manufac- tured by E. R. Squibb & Sons, Inc., Princeton NJ 08540, USA.

REFERENCES HANCOCK. D (1973): Captive propagation of bald eagles Haliaeetus leucocephalus -a review. Int. Zoo Yb. 13: 244-249.

HERRICK. F. H. (1933): Daily life of the American eagle: early phase (concluded). Auk 50: 35-53. JOHNSON, M. J. & GAYDEN. R. (1975): Breeding the bald eagle Haliaeetus leucocephalus. Int. Zoo Yb. 15: 98-100. MAESTRELLI, J , R. & WIEMEYER. S. (1975): Breeding bald eagles in captivity. Wilson Bull. 87: 45-53. NATIONAL RESEARCH COUNCIL (1 977h Nutrient requirements ofpoultry (No. 1). Washington DC: National Academy of Sciences. NATIONAL RESEARCH COUNCIL (1978): Nutrient requirements of cats (No. 13). Washington DC: National Academy of Sciences. OLENDORFF, R. R. (1972): Comments on rearing young buteos. RaptorRes. 6: 6-10, STEWART, P. A. (1972): Weight changes and feeding behavior of a captive-reared bald eagle. Bird Banding 41: 103-1 10.

Manuscript submitted 16 April 1980

Captive breeding of American Golden eagles

a t Topeka Zoo between 1969 and 1976 Aquila chrysaetos canadensis

JUDIE STEENBERG Topeka Zoological Park, 635 Gage Boulevard, Topeka, Kansas 66606, USA

In May 1971 the first successful hatching of the American Golden eagle Aquila chrysaetos canadensis in captivity occurred at Topeka Zoo. Between 1971 and 1976 the breeding pair of eagles hatched 15 out of 17 eggs laid, and until 1975 one chick each year was fledged; in 1976 two chicks fledged.

The breeding pair was acquired from Kansas; the d in September 1964 and the Q in September 1966. Since 1967 they have been kept in a 15 x 9 x 7 m high pipe framework enclosure which is covered with a chain link wire mesh (Kish, 1970). The cage is exposed to all weather conditions and receives only natural light.

The two eagles are easily told apart: there is a characteristic size difference in this species, the Q being the larger, and also an obvious difference in vocalisation pitch and frequency. In addition, there is a small but prominent

growth on the cere of the Q which is a reliable and easily seen identification mark for this individual.

The birds were originally fed on a diet of horsemeat, liver and kidneys supplemented with mice and rats (Kish, 1970). In early March 1969 they were started on Zu/Preem bird of prey diet which they accepted readily, although it was noted that they subsequently drank more water probably because the new diet had a lower moisture content (Kish, 1970). At first, the birds were fed once a day, but this was increased in later years because wild birds ate quite a large proportion. In 1970 entries on the daily report indicate that a canned food was given to the eagles during November, but make no further mention of the experiment except to say that the birds accepted the diet, eating most of the c. 1 . 5 kg offered in five hours. Occasionally the eagles were observed to