Great Bustards in Portugal

Transcription

1 Great Bustards in Portugal By M, D. England Photographs by M. D. England and A. N. H. Peach (Frontispiece and plates 1-8) ORNITHOLOGICALLY, Portugal is still one of the least explored countries in Europe and a visit to any part may be most rewarding. Nevertheless, until my experiences of the last few years, I would not have chosen to go there to study and photograph the Great Bustard Otis tarda. Indeed, Bannerman (1962: 41) commented: 'Mr. Eric Flower writes under date 19th September, i960 that he would not put the whole population in Portugal at more than a couple of score.' After three visits totalling some sixteen weeks, however, I am glad to "be able to say that my friend Eric Flower (who has given me the greatest possible help on each occasion) was being unduly conservative, and it might be difficult to find anywhere in Europe where the species is more easily seen, even though the total number in Portugal may not be very great. I was shown several breeding areas on my first visit in 1963, but, tecause every moment of my stay was devoted to searching for the Black-winged Kite Elanus caerukus {Brit. Birds, 56: , plates 65-72), I only by chance saw three Great Bustards. The following year, while still concentrating on other things, I spent two days assessing the Great Bustard situation with a view to a further visit and I was shown five nests, parties of up to nine adults and two females with chicks. In late April 1965 I was therefore not altogether surprised, continued... 22

2 GREAT BUSTARDS IN PORTUGAL though very pleased, when on the first day of our visit we flushed a flock of 59 in this area. On another occasion 36 were seen together; once a largeflockflewacross a main road in front of our car; and several times large parties of males were seen feeding or sheltering from the sun. Great Bustards are reported from many parts of Portugal, especially out of the nesting season, but the main breeding area falls within a semi-circle of radius 70 miles about the town of Elvas, near the Spanish border. The present position seems to merit greater optimism than either of the maps by Eric Flower and Dr. J. A. Valverde (Bannerman 1962: 43-44) would lead one to suppose, and Victor Reynolds, who has long lived near the centre of the breeding area, considers that numbers have seemed greater in recent years. Although the actual breeding habitat may broadly be described as 'rolling plains', the terrain is of several different types. A majority of nests in most areas are in vast cornfields, but many are also in rough pasture, some in various types of low-growing crops other than cereals, some on land so barren and rough that there is little growing on it, and we were even shown nests in large olive groves, one actually in the shade of a small olive tree. Trees are, in fact, by no means shunned and, when not engaged in nesting duties or in feeding, the birds often congregate in the shade of large cork oaks and eucalyptus. The nesting success must be very low indeed, at least in the parts of Portugal which we visited. Apart from the fact that these wary birds desert readily, the eggs are frequently taken for food or are 'cooked' by the full heat of the blazing sun when a female is kept off the nest by farm-workers or shepherds, while those in oats are often destroyed by the early harvest (those in wheat and barley stand a better chance). Of the five nests which we were shown on our first day in 1965, only one was known to hatch and that because of our intervention. The female in these photographs cracked both her eggs on a small projecting stone in the middle of the nest (plate 2b). Despite this and their becoming increasingly obviously 'addled', she continued to sit well until ants discovered them. She then began to lose interest, but two good eggs were hastily substituted from a nest which was about to be destroyed by the scythe. These she hatched successfully, mainly because we offered to buy the standing crop to stop it being cut, though in the event this proved to be unnecessary because of the co-operation of the land-owner. I have no evidence at all of second layings. On the contrary, on several occasions odd females, which were either non-breeding birds or ones which had lost their nests, were seen during the period when most were sitting or tending young. By this time the males had flocked and had ceased to display. *3

3 BRITISH BIRDS Added to all this, the adults are much shot for sport and food; the mechanisation of farming is spreading, albeit not very fast; and toxic pesticides are being used as enthusiastically as a new toy. It is therefore surprising, and most gratifying, that so large a bird can still be found in Portugal in such numbers. Most nests are a mere scrape in the ground (plate 2b), often nothing more than a flattish bare patch, and two which we saw had so little hollow that the eggs tended to roll away. On the other hand, one in fairly tall grass had a distinct cup and the eggs were well sheltered by overhanging grasses. The eggs which we saw varied very much both in size and colour but were, broadly speaking, various shades of olive with dark brown markings, as has frequently been recorded. A clutch of three is slightly less common than two in our experience: two of the first five nests had three; and one, probably two, of another five had three (one clutch had been smashed by a plough). In Portugal most eggs are laid about the middle of April, and the substituted eggs in the nest photographed hatched on 23 rd May. This mention of a number of Great Bustards' nests must not be taken to mean that they are easily found. On the contrary, it would be possible to go to the right place in Portugal many times without finding a nest, and even without seeing a female Great Bustard. The large number which we saw was the result of planning and a system of rewards for reported nests. One cannot, in fact, ruthlessly trample down acres of growing corn in the remote hope of flushing a sitting bird, and very few females (only one which we saw) can be watched back to the nest. During the incubation period female Great Bustards are very wary. Most rise and slink silently from their eggs when the intruder is a considerable distance away, though some sit very tightly, especially if the nest is in well-grown corn or other thick cover, with the result that when they do leave they go in such a flurry of alarm that there is a grave risk of non-return. The site chosen for photography (plate 2a) had a solitary tree at a distance of seventy or eighty feet, behind which a hide could be started. This was erected at half-height behind the tree in tall undergrowth and must have been virtually invisible to the bird. It was then carefully moved forward by stages, and the growing oats between it and the nest were slowly cut away. The very short moves forward were made only on alternate days. The screen of oats on the hide side of the nest was only very gradually thinned and, as can be seen, was never completely removed. No doubt this careful treatment was the cause of the bird's eventual 'tameness', which allowed such photographs as plate 2a to be taken by people standing in full view. On our first few visits to move the hide we never.saw the bird, but 24

4 GREAT BUSTARDS IN PORTUGAL later she once or twice rose from about a hundred yards away and, after a short flight, landed to cluck agitatedly like an enormous domestic fowl. The blazing sun was at once a menace and a help. We covered the eggs while we were working at the site, but every moment they were left uncovered afterwards was fraught with anxiety lest they Suffer in the great heat. We were in no doubt that the hotter the day the more anxious she was to get back. This was particularly noticeable because, whereas at mid-day she would be incubating a few minutes after one's companions had retired, at the end of the afternoon when the shadows were lengthening she seemed in no great hurry to return. Even so, the eggs must have a remarkable tolerance of great heat, because, of course, there are occasions when they must be left exposed. While we were there the shade temperature frequently rose to 95 F. or more and conditions within the hide, which was in the full sun all day, necessitated the camera being enclosed in a 'cold compress' to prevent the metal parts from becoming jammed. The bird approached the nest, with the utmost wariness and in complete silence, by a series of short zig-zag walks from the side away from the hide (plate 3a). So complete was her camouflage, so stealthy her movements and so long her pauses that one became aware of her presence a few feet behind the nest only because of her continuously pulsating throat. Even when she had practically no cover at all she was very difficult to see unless she raised her head (plate 8). On the nest she was rather clumsy. She trampled down, or broke with her breast, the surrounding oat stems and more than once her efforts at turning the eggs (plate 5 b) left one of them out beside her. As noted earlier, she eventually cracked both of them. Although at various times she was seen to sit facing in most directions, her favourite was with her back to the breeze, cooling herself by lifting her feathers (frontispiece and plates 5 a and 7). In this position photography was nearly impossible when the breeze was at all strong, since fluttering feathers, pulsating throat and waving oats became one large movement. She normally held her head fairly high, even while dozing with her eyes shut, but when suspicious she stretched it higher," only to drop it almost to the ground if danger became imminent, as when someone approached the hide (plate 4). Only once was she seen to stand when alarmed (plate 1) and then she looked remarkably like a watchful gander; this was when she heard the opening of the car door some three hundred yards away. What little evidence we have suggests that the eggs hatch at roughly the same time, which is perhaps to be expected of a species in which the male apparently takes no part in incubation or rearing. A precocious two-day-old youngster would be an impossible responsibility for a 25

5 BRITISH BIRDS bird which dare not leave an unhatched egg for too long on a hot day. Certainly the two pairs of newly hatched young which we have examined closely have appeared to be of the same age (plate 6a). From the time of hatching, their feet and legs are noticeably large (plate 6b), although they are surprisingly weak at first and cannot run far without stumbling and resting. They have a faint mewing call, noted by Dr. Geoffrey Beven as being not unlike the distant mewing of a Buzzard Bttteo buteo. At this time the female clucked like a domestic hen or sometimes made deep 'lowing' or 'moo-ing' notes. When disturbed from her eggs she had uttered guttural croaking or clucking noises. On one occasion (one day after the hatch) a watcher who entered the hide with apparently no hope whatever, because the nest was empty and neither parent nor chicks were visible, was delighted when, after ten minutes, the female walked on to the nest followed by the two tiny chicks. The chestnut on the lower neck of the adult female is very variable; for example, the one in these photographs had almost as much as is usually shown in coloured illustrations of the male (frontispiece). The question of separating the sexes in the field has recently been discussed by Barbier and Stead (1965), but it seems worth adding that some females look very large when by themselves and that flocks of males of mixed ages may consist of birds of very different sizes, some indeed looking little more than half the size of the biggest when standing together. In late April or May solitary' birds are likely to be females and gregarious ones are almost certainly males, though I have no proof that some of the smaller birds in these flocks are not immature females. ACKNOWLEDGEMENTS I have once again to express my thanks to Eric Flower and Victor Reynolds both resident in Portugal for their invaluable assistance. Since the latter lives in the midst of the Great Bustard country, he in particular gave help without which we might have achieved very little. He also most kindly lent us a Land Rover and it was due to his intercession that the cutting of the oats was delayed and'the nest saved, so making photography possible. I am also very grateful to many landowners, especially Snr. Joao de Noronha, who most kindly offered hospitality, and Snr. Jose de Matos Cortes, on whose land was the nest which we photographed; to Snr. Joao F. Flores Bugalho for a great deal of work in preparation for our visit; and, perhaps most of all, to Eng. Francisco Flores and his charming American-born wife, Dona Virginia, to whom nothing was too much trouble and who devoted themselves to smoothing out our difficulties. I must not omit my gratitude to Alan Tait of Oporto for introducing me to Joaquim 26

6 PALEARCTIC BIRD SOUND RECORDINGS Inacio Saloio, whose capacity for collecting information on the whereabouts of Great Bustards and their nests is quite uncanny. Finally, all my party, most of whom had sessions in the hide, worked very hard as a team to bring about success and their observations have been incorporated in these notes. SUMMARY In the years the principal known nesting areas of the Great Bustard Otis tarda in Portugal were visited. Flocks of up to 5 9 were watched and nests seen in a number of places and a variety of sites. The nesting distribution seems rather more extensive in Portugal than previously recorded and there is justification for hoping that numbers have recently increased or at least that previous estimates were pessimistic. One nest was watched and photographed from a hide almost daily for nearly three weeks. REFERENCES BANNERMAN, D. A. {1962): The Birds of the British Isles. Edinburgh and London. vol. ii, pp BARBIER, P. G. R., and STEAD, P. J. (1965): 'The wing pattern of the female Great Bustard'. Brit. Birds, 58:

7 PLATE I. Female Great Bustard Otis tarda standing up at nest before walking off into the oats as an intruder approaches, Portugal, May This shows the general shape, plumage and size of the female, who is smaller and slimmer than the male but still stands about thirty inches high (pages 22-27) {photo: M. D. England)

8 PLATE 2. Above, breeding habitat of Great Bustard Otis tarda, Portugal, May 1965, showing the hide from which the other photos were taken (the sitting female can be seen just beyond). Below, the nest scrape and two greenish eggs blotched with brown; the usual clutch is either two or three (page 24)\ {photos: Al D. England)

9 PLATE 3. Female Great Bustard Otis tarda at nest, Portugal, May Above, approaching the eggs with neck retracted and crouching walk. Below, alerted but not alarmed by a noise from the hide; she stretched up her head when suspicious, but crouched right down if danger threatened (see plate 4) {photos: M. D. England)

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11 PLATES 4 and 5. Female Great Bustard Otis tarda on nest, Portugal, May Left, three studies in alertness: head low as someone approaches, then lower still, and finally right down when he reaches the hide. Above, plumage ruffled in breeze to keep cool. Below, settling down after turning the eggs {photos: A. N. H. Peach)

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13 PLATES 6 and 7. Left, newly hatched chicks of Great Bustard Otis tarda at another nest, Portugal, May 1964, covered in sandy-buff down boldly marked with blackish-brown; note the egg tooth and large foot. Above, a fine study of the female panting in the heat with feathers ruffled to catch the slight breeze and showing the beautiful patterning to good advantage (page 25) {photos: M. D. England)

14 PLATE 8. Female Great Bustard Otis tarda, Portugal, Mav IQ6S. showing the effectiveness of her crvptic coloration: if one covers up the head and neck, the body almost disappears, even though there is only one 'layer' of oats between her and the camera (page 25) {photo: M. D. England)