102 BIRDS OF PREY

leaving no suitable successor in the collection, and at least two pairs are now believed to be beyond breeding age.

The aviaries are well protected from the wind and the owls are kept out-of-doors all the year round, with the exception of the African wood owl Ciccaba woodfordi and Verreaux’s eagle owl Bubo lacteus which are moved into heated indoor quarters in the winter. All the breeding birds are kept in pairs throughout the year.

The birds are normally fed once a day six days a week on minced lean meat, rats, mice and chickens, with Vitakombex vitamin sup- plement added.

Our original prolific pair of Snowy owls Nyctea scandiaca which holds the zoo record for the total number bred was also the first pair in West Germany to achieve breeding success. A pair from the 1972 offspring first produced young when they were five years of age.

The Boobook owl Ninox novaeseelandiae breeding in 1972 was another first breeding in Germany, possibly in Europe.

The two native species, the Little owl Ath- ene noctua and Tawny owl Strix a. aluco were formed into breeding pairs fortuitously. A number of these birds are brought into the zoo by members of the public who have rescued or hand-reared them. Wherever possible they are later released by us back into the wild, but occasionally individuals are kept to make pairs suitable for breeding.

PRODUCT MENTIONED IN T H E T E X T Vitakombex: vitamin supplement, manufactured by Puke-Davis & Co., Usk Road, Pontypool NP4 8YH, Great Britain.

Manuscript submitted 13 April 1982; revised August 1983

Breeding birds of prey at the East Berlin Zoo DIETER MINNEMANN Curator of Birds, Tierpark Berlin, DDR- I I36 Berlin-Friedrichsfelde, A m Tierpark 125, East Germany

When the East Berlin Zoo opened in 1955, the modest number of animals then in the collec- tion already included some birds of prey. Over the years this number has steadily increased and today the zoo houses some 67 species of diurnal birds of prey and 34 species or sub- species of owls. Our object, however, has not been merely to display rare specimens but to study and breed them, and our present scien- tific breeding programme is based on the foun- dations laid in the early years.

The years of observation and research are now beginning to show results. In the last six years we have achieved the breeding of seven species of diurnal birds of prey and seven species of owls for the first time. Of these the American bald eagle Haliaeetus leucocephalus was the first to be successfully bred in Europe and three species, the Harpy eagle Harpia harpyja (Plate 1 ), the European black vulture

Aegypius monachus and the Wedge-tailed eagle Aquila audux are world ‘firsts’ (Table 1).

The experiences of the last 25 years have led us to believe that there are four basic criteria for breeding bird of prey species: housing, feeding, pairing and staffing. A few comments on each of these are offered below together with a few remarks on hand-rearing and, more particularly, the avoidance of hand- rearing in certain circumstances.

HOUSING The first requisite for successful breeding is favourable living conditions. Only part of our collection is on display to the public and the more delicate and sensitive species, such as tropical hawks, are kept off exhibit. The exhi- bition cages are modern and spacious, with an immense open-air aviary in the centre of the complex for large and middle-sized vultures,

BIRDS OF PREY 103

mineral supplements are unnecessary. Except when rearing young, adult birds have one non- feeding day per week, with the exception of the vultures which are fed every other day.

PAIRING Ideally birds should be paired only after a thorough study of their individual behaviour. T h e increasing rarity of many species, how- ever, and even the laws which have been invoked to protect them, often increase the difficulties of finding suitable breeding pairs. Despite strenuous efforts we are still in a position where some species are represented in the collection by only one sex.

A large part of the answer to this problem lies in co-operation between the world’s zoos and this fortunately has become more exten- sive in recent years. We, for instance, have collaborated closely for many years with the Antwerp, London and Moscow zoos, the Vogelpark Walsrode and many private breeders. The world’s first captive-bred Harpy eagle was hatched in our collection in 1981 as the result of a breeding loan agreement between the warden at the Falconry Station at Berlebeck and our zoo,

Plate 1. Adult p Harpy eagle Hay@ harpyia with her young, aged 19 days, hatched in September 1981 at East Berlin Zoo. Klaus Rudloff

which can often be seen in full flight. Display cages, however, should always be capable of being adapted for the birds’ special needs for breeding. In our zoo some exhibition areas are closed to the public during the breeding season, while those species or individuals which require complete seclusion in order to breed and rear their young successfully are housed in specially designed breeding quarters.

FEEDING With the exception of the vultures, birds of prey and owls need freshly killed whole animals such as domestic chickens or their chicks, mice, rats, hamsters, guineapigs, rabbits or freshwater fish. Wherever possible animals reared as food species are provided with only fresh food (green plants, fruit, vege- tables and seeds). In this way we feel that the birds of prey and owls will receive food of a high nutritional standard and that vitamin and

STAFF Well-trained and experienced keepers are essential to any breeding programme, and we believe them to be of particular importance with birds of prey.

In addition to those members of staff en- gaged in the day-to-day care of the animals, we also have a large number of research workers involved in a continuous programme of biological study. This work it is hoped will not only help to fill the many gaps in our knowledge of these species but also provide the essential background for further breeding successes.

HAND-REARING With modern equipment and methods, arti- ficial incubation has become a highly reliable technique which for some regularly bred species has greatly increased the rate of hatch- ing. Some breeders take advantage of this fact to exploit breeding pairs to their maximum potential by removing eggs as they are laid to

104 BIRDS OF PREY

SPECIES NO. OF NEST LAYING MATURE BIRDS BUILDING d Q ?

Turkey vulture Cathartes a. aura

American black vulture Coragyps atratus

Andean condor Vultur gryphus

Black kite Mzlvus migrans

Red kite M. milvus

Pallas’ sea eagle Haliaeetus leucoryphus

American bald eagle H. leucocephalus

White-tailed sea eagle H. albicilla

Steller’s sea eagle H. pelagicus

Egyptian vulture Neophron permoptems

Lammergeier Gypaetus barbatus

Hooded vulture Necrvsynes monachus

Himalayan griffon Gyps himalayensis

Griffon vulture G. Jiulztus

Lappet-faced vulture T v r p tracheliotus

European black vulture Aegypius monachus

White-headed vulture Trigvnoceps vccipitalis

Northern goshawk Accipiter gentilis

Red-tailed hawk Buteo jamaicensis

Common buzzard B. buteo

Rough-legged buzzard B. lagopus

Long-legged buzzard B. rujnus

Ferruginous hawk 8. regalis

Harpy eagle Harpia harpyja

Greater spotted eagle Aqutla clanga

Tawny eagle A. rapar

Golden eagle A. chrysaetos

Wedge-tailed eagle A. audax

1 1

1 1

1 1

1 1 3

2 2 4

1 2

1 1

2 3

2 1

1 1

2 0 3

1 1 1

5 5

1 1

0 1 2

3 3

1 1 1

0 1

1 1 2

1 2 4

0 2

1 1

1 2

1 2

1 1

3 3

1 1

2 2

X

X

X

X

xx

X

X

x

X

X

X

X

xxxx

X

- XXX

X

X

X

xx

X

X

xx

xx

X

XXX

X

xx

X

X

X

X

xx

X

X

X

- X

X

X

xxxx

X

X

XXX

X

X

X

xx

X

X

xx

xx

X

xxx

X

xx

FERTILE REARING

X - X X

- -

X -

xxxx xxxx

- -

X -

X X

X X

X X

- -

xx xx

X X

xx X

BIRDS OF PREY 105

SPECIES NO. OF NEST LAYING FERTlLE REARING MATURE HlRDS BUlLDlNG d p ?

Ornate hawk eagle Spizaetus nrnatus

Secretary bird Sagittarius serpeniarius

Forster’s caracara Phalcoboenus australis

African pygmy falcon Polihierax semiiorquatus

Red-legged falconer Microhierax caerulescens

American kestrel Falcn sparverius

Common kestrel F. iinnunculur

Prairie falcon I.: mexicanus

Barn owl Tyto alba guttaia T. a. alba T. a. aflnnrs

scops owl otus scops

Collared scops owl 0. bakkarnnena

Great horned owl Bubo virginianus

Eagle owl B. b. bubo B. b. omissus B. b. bengalensis

Cape eagle owl B. capensis mackinderi

Spotted eagle owl B. a. a f ianus

Fraser’s eagle owl B. poensis

Malay eagle owl B. sumatrana

Verreaux’s eagle owl B. lacteus

Malay fish owl Keiupa keiupu

Vermiculated fishing owl Srotopelia bouvieri

Spectacled owl Pulsatrix perspuillata

Snowy owl Nyciea scandiaca

Boobook owl Ninor novaeseelandiae

Little owl Aihene noctuo

Spotted little owl A. brama

African wood owl Circaba woodfordi

1 3

1 1

1 1

0 1

1 2

0 2

1 2

n i

3 3 2 2 0 1 1

1 1 2

0 2

1 1

4 4 2 2 1 1

0 1

1 1

0 2

0 1

1 1

0 1 1

0 1

1 1 1

5 5

1 1

n i

0 2

0 1 1

xxx

X

X

X

xx

xx

xx

-

xxx xx X

X

xx

X

xxxx xx X

X

X

xx

X

X

X

X

X

XXXXX

X

X

X

X

xxx

X

X

X

xx

xx

xx

X

XXX xx x

X

xx

X

xxxx xx X

X

X

xx

X

X

X

X

X

XXXXX

X

X

X

X

- X

X

-

X

- X

-

xxx xx -

X

-

X

xxxx xx X

-

X

- -

X

-

-

X

xxxxx

X

-

-

-

106 BIRDS OF PREY

SPECIES NO. OF NEST LAYING FERTILE REARING MATURE BIRDS BUILDING

8 9 ’

Tawny owl

Rusty barred nwl

Ural owl

Great grey owl

Long-eared owl

Tengmalm’s owl

Strix aluco 2 2 xx xx xx xx

S. hylophala 3 3 XXX XXX xxx xxx

S. uralensis 1 2 X X X X

S. nebulosa 0 2 xx xx

Asio O ~ U S 0 2 6 xx xx

Aegolaus funereus 2 2 xx xx xx xx

- -

- -

Table 1. Diurnal birds of prey and owls at present in the collection of East Berlin Zoo which have bred or shown some breeding behaviour. The number of crosses indicates the number of pairs (or individuals) involved.

Plate 2. A pair of Tawny eagles Aquila rapar with their young, aged 15 and 16 days, hatched in April 1976 at East Berlin Zoo. Cerhard Budiclt.

BIRDS OF PREY 107

boost egg production, incubating artificially and rearing the chicks by hand. In special cases such intensive breeding methods may be beneficial. They are justified, for example, in an attempt to give a rapid growth to a highly endangered population, such as in the conser- vation programmes for the Peregrine falcon Falco peregrinus or the Mauritius kestrel F. punctatus; they can be used to advantage to produce birds for falconry and avoid pressures on the wild birds. We believe, however, that used to excess they could be detrimental to the health of the captive-bred population.

It has to be admitted that the history of arti- ficial rearing techniques is relatively short but our observations to date suggest that birds as well as mammals may suffer serious inter- ference with their behaviour patterns if natural breeding processes are continually disrupted. We should be particularly careful when manipulating species whose way of life and behaviour are, as yet, little known.

It is clear, however, that hand-rearing will continue to be necessary for a variety of com- pelling reasons. We would stress that when it is undertaken, full and precise data should always be recorded and published. The obser- vations published by Fentzloff (1979; see also this volume) on a variety of artificial methods provide a good example of the useful data which can be obtained.

Wherever possible we try to avoid hand- rearing, and the use of bird of prey foster parents has proved of value for both aban- doned eggs and nestlings.

If we find abandoned fertilised clutches we first try to place the eggs under an incubating Q of similar species. One egg, or at the most two, can be added to the existing clutch of an experienced pair. The additional egg should not be more than twice the size of the bird’s own egg nor should the incubation period exceed the foster parent’s by more than one-third. We have found that it is quite poss- ible to get a p of a Buteo sp to accept and hatch the egg of an eagle or a sea eagle (Minnemann, 1976).

In our part of Europe nearly all bird of prey species breed between the end of February and early June. Among the species which breed at different times during this three-and-a-half-

month season, we have used as foster parents the Common kestrel Falco tinnunculus, Com- mon buzzard Buteo buteo and Tawny eagle Aquila rapax. If we believe that a suitable Q might be needed at a particular time, an indi- vidual’s breeding season can be delayed by manipulating various factors. We have, for example, deliberately postponed the incuba- tion of a Common buzzard by offering the most important stimulus, the nesting material, a few weeks later than normal. It is not essen- tial for a p to have laid a clutch of her own; providing that she is in breeding condition, an artificial egg can be used to encourage her to sit.

Clearly when eggs or young of another species are added to an existing clutch it is necessary to select species where the growth rates of the young are similar, since if there are marked differences the weaker nestling will be at a disadvantage and may be killed by the larger chick. This has occurred with both the Lesser spotted eagle Aguzla pornarina and the Ferruginous hawk Buteo regalis.

The rearing of young by foster parents has also proved successful. In general the behav- iour and voice of the young of many birds of prey are similar, and foster parents will accept another species with little difficulty. As birds of prey apparently do not recognise their off- spring individually, chicks can be exchanged at any time and Meyburg (1971) based his method of increasing the offspring of the Lesser spotted eagle on this principle.

If the egg has been incubated by the foster parents there is little likelihood of their not accepting the offspring and we have had a Wedge-tailed eagle successfully reared by a pair of American bald eagles and a Ferrugi- nous hawk by a p Common buzzard.

Introducing a hatched chick into the nest of foster parents is somewhat more complicated but we have found that one can usually be added to an existing brood if the difference in size is not too great.

If the bird is incubating an infertile or dummy egg, however, it can be encouraged to accept the chick as its own by providing it with any hatching egg. The first contact between parent and young appears to be aural, the incubating bird reacting to the sounds made by

108 BIRDS OF PREY

Plate 3. Two three-day-old Golden eagle chicks Aqurlu c b y z e t o s hatched in May 1980 at East Berlin Zoo. Kluus Rudloff

the chick before hatching. With birds of prey, at least, it appears that these sounds do not have to be from the same species. In fact according to our present research the chick's calls from within the egg appear to be similar in most birds. Other experiments have shown that it is not even necessary to use a live egg and acceptance of a strange chick has been achieved on at least one occasion by playing the calls on tape (Fentzloff, pers. comm.).

When on 7 May 1980 a Golden eagle Aquila chrysaetos hatched two chicks for the first time (Plate 3), we had the opportunity to put the live-egg method to the test. We had had experience of first broods being neglected by GoMen eagle 9 9 and when this 9 had failed to feed the young after 48 hours we were obliged to remove them and hand-feed. At the same time, at 1800 hours on 9 May, we

placed a pipped domestic chick egg under an American bald eagle 9 which had been sitting on an unfertilised clutch for 47 days. When this hatched at about 0700 hours the following morning, the pair began to defend the nest with increased vigour and the newly hatched chick was exchanged for one of the four- day-old Golden eagles. The foster parents fed it for the first time seven hours later, and three days later, when the rearing appeared to be progressing well, the second young eagle was put into the nest. Both young were reared successfully by the foster pair.

Our first observations indicate that similar methods would be successful for owl species and in the near future we hope to investigate the possibilities of fostering of both eggs and young of vultures. The more involved feeding biology of some of the latter, however, intro- duces complications which we have not yet experienced.

REFERENCES FENTZLOFF, c. (1979): Die Handaufzucht von Greifvogeln und Eden mit Tabellen zur Gewichtsennvicklung und zum Futterverbrauch. In Greifvngelhalrung und Arten- scbutz. (Symp. EHA Heidelberg 2, 3: 4342. ) Fentzloff, C. (Ed.). Burg Guttenberg: Verlag Deutsche Greifen- warte. MICYRURG. B - U (1971): Versuche der kunstlichen Steiger- ung der Vermehrungsrate des Schreiadlers (Aguilu pomarina) zu seinem Schutze. Beitr. Vogelk. 17: 207-227. MINNEMANN. D. (1976): Aufzucht eines Weisskopf- seeadlers (Haliueetus leucocepbalus) durch ein Adlerbus- sardpaar (Buteo ru j fus ) . Zool. Curt., Jena (N.F.) 46: 54-65,

Manuscript submitted 11 January 1983; revised October 1983

Longevity of birds of prey and owls a t East Berlin Zoo DIETER MINNEMANN & HORST BUSSE Curator of Birds and Head Keeper, Tierpark Berlin, DDR-I136 Berlin-Friedrich$elde, A m Tierpark 12.5, East Germany

Some years ago a number of longevity records for birds of prey and owls kept at the London, San Uiego and Zurich zoos were published in the Yearbook (Lucas, 1970) and it might be of

East Berlin collection (Table 1). A wider knowledge of their possible life-

span would be of value to the research on the

biology of these birds and where the birds are breeding or showing some breeding behaviour this has also been indicated.

interest to add to these Current data from the ~ ~ ~ ~ k ~ ~ ) ~ 1 9 7 0 ) : Longevity ofbirds ofprey and in captivity. Int. Zoo Yb. 10: 36-37.

Manuscript submitted 11 January 1983