New observations on the Brazilian Merganser

WOLF BARTMANN

Introduction

The Brazilian Merganser octoceta- ceus is one of the world’s rarest waterfowl. First described by Viellot in 1817 from specimens taken in , this Merganser remains a great rarity even in museum collections where, at most, a few dozen skins exist. Little behaviour has been docu­ mented. primarily due to the absence of specimens in captivity. It has never been held in North American or European collections, and a few taken captive in South America died within days. Endemic in south-eastern Brazil and the neighbour­ ing regions of eastern Paraguay and north­ eastern Argentina, the centre of its distribu­ tion is the Alto Parana basin (Delacour 1959). Small upper river tributaries inter­ spersed with waterfalls and flowing through tropical forested valleys are the preferred Figure 1. Location of the Serra da Canastra habitat for isolated, sedentary populations National Park. Minas Gerais State, Brazil, South of this remote duck. The main rivers are America. shunned. Because of its shy, secretive ways and inaccessible habitats it was even at one observations were augmented, when I paid time considered extinct (Phillips 1929). especial attention to one breeding pair of More fortunate than its only austral coun­ Brazilian Mergansers during another stay terpart, the Auckland Island Merganser in 1984. Mergus australis now extinct, the Brazilian Besides documenting the present status species, last taken in Brazil in 1922 (Sztolc- and distribution of the Brazilian Merganser man 1926), was rediscovered in 1947—48 in in Brazil itself, the purpose of this paper is the Province of Misiones, Argentina (Giai to report in more detail on parental care 1951). The field studies there of Partridge with some first photographic records of (1956), who began his work in 1949 and first family life. discovered a Brazilian Merganser nest, in a tree cavity, and collected three of the downy young in 1954, constitute about all Study area and methods the knowledge to date of the species. Ornithological exploration in south­ The Serra da Canastra National Park eastern Brazil after the last known was (20°15'S, 46°40'W) is situated some 700 km taken there in 1922, revealed no records in north-west of Rio de Janeiro in south­ the extensive area supposed to be inhabited eastern Minas Gerais State. The Park's by the Brazilian Merganser. I therefore had 73,000 ha is a highland plateau, 900-1,400 little hope of an encounter, when in 1981 I m in elevation. The topography is charac­ went to conduct an anteater field study in terised by rolling, rocky grassland with the Serra da Canastra National Park in steep escarpments, and deep valleys. The Minas Gerais (Figure 1). Nevertheless Pro­ climate is high mesothermal tropical, with fessor Helmut Sick from the Rio de Janeiro dry winters and rainy, mild summers. National Museum had strictly advised me Prior to the foundation of the National to keep an eye open for octocetaceus in th at Park in 1972 and subsequent expropriation, region. I quickly found how right he was, the dominant grasslands were privately because my son Claus and I indeed disco­ owned as a single large ranch with low- vered the curious duck in the Park during density cattle grazing. Gallery forests per­ our fieldwork in 1981 and again 1983. My sist on lowland and riparian sites too wet 7 Wildfowl » (1988): 7-14 8 Wolf Bartmann

for periodic burning. The Park's ecological duck is therefore not a very photogenic importance derives from its numerous subject. watercourses, which form the headwaters of the rivers Paranaiba and Rio Grande running west to the Parana basin and those Observations of the River Sao Francisco draining to the east and north. The Serra da Canastra National Park was My study area was in the north-east of visited and observations made on the Braz­ the Park, where the Sao Francisco River ilian Merganser as follows:- originates and runs with mild gradient Year Dates Sightings Observations about 14 km through the uplands before (Hours) ending in the spectacular 2 0 0 m waterfall 1981 3(1 Julv - 25 Aug 5 14 Casca d'Anta. The pair of Merganser I 1983 21 Mar - 12 Apr 4 9 mainly observed occupied this upriver 24 Oct - 4 Nov ? 3 stretch and a second pair was occasionally 1984 12 Aug - 22 Aug 9 47 recorded downstream. A third pair existed 1985 10 Aua - 22 Aug 3 5 about 50 km away along a rivcrcourse (Corregio dos Rolinhos) near a place In 1981 and 1983 not much tim e could be named Retiro das Pedras. This pair was also spent on duck observations because of our observed by D.A. Scott (pers, comm.) in day-long fieldwork on the Giant Anteater 1983. All river habitats frequented are Myrmecophaga tridactyla on the hillside. characterised by clear, oxygenated water Our camp was near the Casca d’Anta that flows over rocks, stones, gravel and waterfall and while going to bathe in the limited areas of sand. Boulder strewn rapids river pools in early morning or late after­ and numerous exposed cliffs alternate with noon we had good chances for opportunistic wider channels or pools with reduced duck watching. In this way we first recorded currents which may be quite deep. The the in flight close to the surface along meandering mountain streams are in some the river, disappearing before we could areas bordered by high banks with over­ even clearly identify them as mergansers. hanging vegetation of the luxuriant gallery Having found early on that an open forest. Much of the river below the Casca approach will frighten them and cause them d’Anta fall contains large rounded cliffs and to fly away from us, we usually stalked to gravel banks up to the Park border. the water in the shelter of vegetation and Changes in water level are frequent and cliffs, carefully avoiding open ground. Hid­ irregular during heavy rains. Seasonal dif­ den on the bank, we could then spend more ferences between lowest and highest water time observing their movements, displays, levels can be up to 5 m. feeding, diving and resting behaviour. There were some opportunistic encoun­ Usually one pair was observed in an area ters with mergansers in the years 1981 and and only on one occasion (22 March 1983) 1983, but I concentrated in 1984 on day­ were three ducks recorded, staying together long surveys on one pair with a brood. The peacefully. The undisturbed mergansers ducks were daily located on foot or from were always very silent. When frightened hides and their movements and behaviour and in flight a harsh krack was to be heard. were recorded with the help of binoculars As soon as they discovered us, the ducks and tape recorder. I supplemented my field became nervously alert, swimming or flying notes with tele-lens (640 mm Novoflex) swiftly out of sight. The food of mergansers photography and Super- 8 -mm films. living in the National Park is primarily the Male and female could only be disting­ known as Lambari Astyanax fasciatus, uished by a slight variation in the greenish- which is abundant, with sizes up to 15 cm, black head and neck region, because they in all creeks, rivers and pools of the whole showed otherwise little external dimorph­ area. No other kind of fish could be found ism in size and proportions. In particular in the waters of the highland plateau. The the crests were of similar length, the mergansers preferred rapids and cataracts female’s not, like those observed by Par­ with fast flowing currents as feeding tridge (1956) being shorter as a consequ­ grounds, where their prey is apparently ence of copulation grappling. A Brazilian abundant and easy to obtain. We observed Merganser appears rather dark on the water them feeding in the shallow water with their except for white patches on the wings. The heads submerged, but also diving in deeper Observations on the Brazilian Merganser 9

Figure 2. General view of the upper Rio Sao Francisco, Serra da Canastra National Park. (Photos by the author, taken from colour transparencies.)

F igure 3. A pair of Brazilian Mergansers at midday in July 1981. 10 Wolf Bartmann pools, remaining under water for periods above the river and from blinds established from 9 to 27 seconds. During the day they near the water. In this way the mergansers were found resting on exposed stones in the could be observed either in the distance river, not walking very much when ashore. when overlooking several hundred metres of river or quite close in front of the hides. Breeding pair and young The consecutive all day watches were limited to daylight hours usually from In August 1984 I returned again to the Serra 06.00-18.00 hrs. Sightings of the duck da Canastra National Park to concentrate family were more common in the mornings my time strictly on the mergansers. During and evenings than in the middle of the day. eleven days I focused on the particular pair Movements and activities on the water

I had already encounted on former occa­ decreased rapidly after 1 0 . 0 0 hrs, and later sions along the river above the Casca it was not easy to locate the immobile birds d’Anta waterfall. It was still the dry season resting for hours on cliffs or gravel banks. when I arrived on 14 August and the water During all my observations the young levels in the riverbed and pools were ex­ were seen only with both parents present. tremely low. After having again set up my Without doubt the male took an active part tented camp near the waterfall I did a first in the parental duties after the female had survey on the Sao Francisco upstream, but reached the water with the newly hatched found nothing except one Darter A nhinga brood. Indeed, (Partridge) 1956 noted that anhinga and a pair of Pied-billed Grebes the male remained in close attendance Podilymbus podiceps, on the water in that while the female was incubating and when late afternoon. But next morning just after she came off the nest, once a day, to feed. 06.00 hrs when daylight came and I walked My birds remained paired and spent all the up the river a few hundred metres, I sud­ time in close association, attended by the denly became aware of duck vocalisations, ducklings. In search for food the latter a soft, quiet rack sound. I could not see the occasionally spread some distance over the birds because of the thick vegetation. After water surface, but quickly returned towards rushing through the brush I was suddenly their parents when alarmed. A contact call confronted with a pair of adult mergansers like a softer rak-rak-rak was sometimes in close association with their brood of six heard from the leading adults and the chicks downy young. The family was just passing answered with a high-pitched ik-ik-ik. Simi­ some rapids and while the adults often lar vocalisations, but harsher and louder, swam with their heads submerged, the tiny were used by both young and adult birds ducklings drifted on the fast-flowing water when frightened. Although normally so surface like dancing corks. Judging by their wary and ready to fly off, the adults size and activity they seemed to be no more remained with the brood even when threat­ than about three days old. The adults soon ened by my approach and the entire family became aware of the intruder and raised escaped by swimming off, uttering loud the alarm with loud and intensive krack- warning calls. Only on one occasion did krack calls, jerking head and tail rhyth­ both adults fly up and leave the scattered mically. This caused their young to immedi­ ducklings behind. However, they landed 40 ately hurry up close to them. The whole m away on the water, and immediately family then swam quickly down the river began calling and searching for their young. and was soon out of sight behind the veget­ The chicks showed great ability for passing ation of the next bend. Although I caught rapids when pursued and hurried directly one more glimpse on this day when walking to the parents. along the river, I found that observing the On 18 August one of the ducklings was ducks by following them on shore was a missing and I never counted more than five complicated, exhausting and inefficient young again. Besides the resident birds of method. The merganser family was too prey, including the Black-and-White mobile, moving over 4 km that day, and Crested Eagle Spizastur melanoleucus, as therefore it was often difficult to locate and enemies from the air. Otters Lutraplatensis follow them through all the dense, over­ were observed in that river territory, and hanging vegetation, which made observa­ they must be presumed to be a predator on tions almost impossible. During the coming young mergansers. During resting periods days it proved better to study the ducks one of the adults at least was cautiously from observation posts on the hillside far alert, while the other slept or brooded the Observations on the Brazilian Merganser 11

Figure 4. Apparently the same pair as in Figure 3, with 5 young. The female, leading, had less extensive dark feathering on the neck.

Figure 5. Guided by the adults, the young often fed on in the shallows close to the bank. 12 W olf R artmann young. Disturbed mergansers entered the lian Merganser, the species was found in water quickly and sought shelter under Brazil itself during recent times only in the overhanging vegetation or gathered states Goias (alto RioTocantins 1953,1960, together, swimming towards the centre of 1972) and Minas Gerais (Serra da Canastra open water. While swimming the ducklings 1979). Dietz (1980) noted the occurrence sometimes tried to mount their parents of the Merganser in that National Park and back and when successful, they were carried estimated the population in the Park and clear of the water, as is known from other the surrounding areas to be about 50 birds, merganser species (Bauer and Glutz 1969). which I believe is much less. My surveys The adults with the chicks were observed and study, 1981-84, confirmed their pre­ foraging mainly during the early morning sence and resulted in a first breeding record and late afternoon hours either in the shal­ for the area. Furthermore, while visiting in low waters of rapids and along banks or 1987 the Serra do Cipo National Park near occasionally in the deeper pools. The young Belo Horizonte, I found another suitable showed much agility when pursuing insects merganser habitat in Minas Gerais along above or on the water surface. They paid the clear headwater of the Rio Cipo. De­ much attention to the parents when these spite the fact that no other records are dived for fish. As soon as one parent available, the species may exist in some surfaced all the chicks sped towards it other protected and remote areas of south­ hardly touching the water surface with their eastern Brazil, where human pressures and feet and flapping their downy wings, de­ developments have not destroyed the pris­ sperate to pick the prey from their parent's tine river ecosystem. The Brazilian Mer­ bill. 1 never recorded ducklings diving, ganser is a river specialist, extremely depen­ perhaps because these downies were still dant on fast, clear mountain streams. These too young. In the shallow water they fed have become quite rare, outside national primarily by sight, with their heads sub­ parks and nature reserves, as a result of merged, probably consuming aquatic inver­ agricultural development, watershed de­ tebrates such as larva ( Trichoptera, gradation and . Within the Serra Plecoptera, Diptera) at first and fish as soon da Canastra National Park the protection as they were able. Fish seemed rapidly to to date is excellent and the scarce mergan­ replace invertebrate food in the growing ser population can remain undisturbed ex­ ducklings. cept for increasing nature . This is During my observation period the resi­ concentrated on a limited area mainly be­ dent pair never encountered other mergan­ low, and, to a lesser extent, above the scenic sers in their territory and therefore no Casca d'Anta waterfall. But it seems to me aggressive display was recorded. They by observations in 1985-87, that the ducks occupied a river stretch about 7 km in formerly resident here are now avoiding length, as far as could be estimated from such tourist frequented locations. all the locations and sightings. Daily move­ The strong long-term pair bond and terri­ ments over at least half this distance were toriality were a conspicuous aspect of the quite common for this family. Unfortun­ Brazilian Merganser’s behaviour. The pair ately I had to leave the area on 22 August I observed in particular obviously remained and no further reports on that family are on the same stretch of river throughout the available except for one personal communi­ year, never being migratory. The territory cation I received on 28 December 1984 from maintained in the non-breeding season is Sr Luiz Artur Castanheira, former Park tied to the food resource and will probably Director. He wrote: “. . . a familia do Pato be defended by both pair members against Mergulhao (= Merganser) foi observada no intruders. Territory size may be correlated mesmo local e havia 5 filhotes bem grandes to variation in the number of rapids, falls, junto do casal. Sao provavalmente os mes- pools, current velocity and other factors mos que voce fotografou . . .”. I am indeed determining territory quality. Presumably quite sure those ducks were the family I merganser density in a certain area will be had observed some months before. related to these factors. Our impression of the breeding season of the Brazilian Merganser in the Serra da Discussion Canastra accords with that of Partridge According to Sick ( 1984), who reviewed the (1956) for an area a thousand kilometres to past and present distributions of the Brazi­ the south-west. It begins in June, with Observations on the Brazilian Merganser

Figure 6. The family also frequently foraged in the rapids.

Figure 7. The family rested at midday, but the adults remained alert. 14 Wolf Bartmann

incubation in July/August. Downy young his recommendation. I thank the Instituto Brasi- were found in August. Despite careful leiro de Desenvolvimento Florestal (IBDF) for search, I was never able to spot a nest, and licensing my stay in Serra da Canastra National the incubation period and the full range of Park in Minas Gerais. To the former Directors clutch sizes remain uncertain. But Partridge Drs Jairo de Barrho and Luiz Artur Castanheiro and their park staff I am indebted for assistance observed a brood of four and had a report and help. I am grateful to Sr Guenter P. Kunze of another of five, while my observation of Sao Paulo for support and providing facilities indicates that at least six eggs are possible. in Brazil. The active role of the male in brood rearing is clearly shown and verified as a form of pair bond maintenance. Summary What of the Brazilian Merganser’s fu­ ture? Its limited range and specific habitat Preliminary observations in 1981-83 revealed requirement suggest a small population. and confirmed the occurrence of the Brazilian Like most small, specialised populations, M erganser Mergus octocetaceus endemic in the this duck is highly vulnerable to habitat area of Serra da Canastra National Park in Minas alteration and human pressure. Survival is Gerais, south-eastern Brazil. In 1984 a breeding only guaranteed in strictly protected areas pair rearing six chicks was found here and of its reduced historical range. observed closely during the middle of August. The adult pair remained strongly bonded and the male took part in parental care. Day-time activi­ ties and behaviour are described. The species is Acknowledgements a year-round resident and territorial in that area. The species should be secure here, as long as the I would like to extend my special appreciation appropriate habitat is not violated. to Professor Helmut Sick of Rio de Janeiro for

References

Bauer, K.U. and G lutz, U.N. v. Blotzheim. 1969. Handbuch der Vogel Mitteleuropas. Vol. 3,2. 407 pp. Delacour, J. 1959. The Waterfowl of the World. 3:200-207. London. Dietz, J.M. 1980. Ecological studies of the Maned Wolf in the Serra da Canastra National Park, Minas Gerais State, Brazil. South America. IUCN/WWF Project 1584. Giai, A.G. 1951. Notas sobre 1a avifauna de Salta y Misione. Hornero 9:247-276. Partridge, W.H. 1956. Notes on the Brazilian Merganser in Argentina. A uk 73:473^188. Phillips, J.C. 1929. An attempt to list the extinct and vanishing birds of the Western Hemisphere with some notes on recent status, location of specimens, etc. Verh. VI Intern. Ornith. Kongresss Kopenhagen /926: 503-534. Sick, H. 1984. Ornithologica Brasiliera. 1:195. Sztolcman. J. 1926. Etudes des collections ornithologiques de Parana (D'apres les resultata scientifiques de L'Expédition Zoologique Polonaise au Brésil, 1921-1924). Ann. Zool. Mus. Polonia, Warszawa 5:107-196.

Dr. Wolf Bartmann, Tierpark Dortmund, Mergelteichstr. 80, D-4600 Dortmund 50, W-Germany.