Population size and feeding behaviour of Andean Geese at Lake Junin, Perú RONALD W. SUMMERS and GONZALO CASTRO Introduction llamas. Pigs roam freely and forage among the muddy water channels. The wet pas­ The Andean Goose Chloëphaga melanop- tures on which the geese forage are com­ tera (known as the Huallata or Huashua in posed almost entirely of short-leaved (1—4 the Quechua language of the Peruvian cm) fleshy plants. The following other Indians) is one of five species of sheldgeese plants were recorded: mosses, N ostoc sp. (Tadornini), all of which are restricted to (Nostocaceae), Chara sp. (Characeae), South America. The Andean Goose occurs Myriophyllum sp. (Halorrhagidaceae), along the Andes from 8 °S in P eru to 33°S Hydrocotyle sp. and Lilaeopsis sp. (Umbel- in Argentina and 38°S in Chile (Hellmayr liferae). Grasses (Gramineae) are rare in 1932; Goodall et al. 1951; M. Plenge pers, this habitat. comm.) where they nest above 3,000 m. In winter some migrate down to about 2 , 0 0 0 m (Casares 1934; Goodall et al. 1951) and Methods are rarely found at sea level (Pearson and Plenge 1974). The lake was visited between 1 and 4 The little that is known about the Andean September 1984. Birds were searched for Goose is based on casual observations by by touring the roads and tracks round the field naturalists or observations made in lake and periodically scanning the sur­ waterfowl collections (Castillón 1918; rounding area with binoculars and a xl5- Casares 1934; Delacour 1954; Koepcke and 60 telescope. Koepcke 1965; Johnsgard 1965,1978; Rossi On 3 September the diurnal activity of 1967; Weller 1968). Large numbers gather geese was recorded each 2 0 minutes from in winter at Lake Junin, Perú, and in this sunrise to sunset, from a sample of about study we describe the numbers, distribution 150-200 geese in each 20 minute period and feeding behaviour of this population. (Altmann 1973). The following activities Comparisons are also made with the sheld­ were recognised; “grazing”, “walking”, geese which winter in the Falkland Islands: “standing”, “agonistic behaviour”, thus comparing species which winter at high “flying”, “sitting”, “preening”, “drinking”, latitudes with the Andean Goose which “swimming” and “bathing”. The percen­ occurs at high altitudes. tage of the day spent in different activities was calculated by taking the mean percen­ tage of birds carrying out each activity in Study area each 2 0 minute period. Food intake was calculated indirectly Lake Junin is a large lake (28 x 13 km) at from estimates of daily production of faeces an altitude of 4,078 m in the Andes, 300 and digestive efficiency, using the cell-wall km east of Lima. The habitats and ecology material (cellulose, hemicellulose and lig- in and around the lake have been described nin) as an indigestible marker (Ebbinge et by Dourojeanni et al. (1968) and a recent al. 1975). Summers and Grieve (1982) have account of the waterbirds is given by Harris shown that this method gave similar results (1981). The climate is cold (annual average to a direct determination of digestive tem p eratu re is betw een 3 and 6 °C) and most efficiency in the Upland Goose Chloëphaga of the rain (400-800 mm) falls in summer. picta. Intervals between successive defaeca- The plant associations belong to the tions (the interfaecal period) were mea­ “Páramo húmedo sub-alpino” and “Tundra sured with a stopwatch whilst geese were muy húmedo-alpino” formations of the observed through the telescope (Owen Holdridge classification adapted by Tosi 1971). Fresh faeces were collected and (1960). samples of the herbage were clipped, dried The drier pastures around the lake are to constant weight in an oven at 60-90°C, intensively grazed by thousands of sheep weighed, and the organic content, calorific and smaller numbers of cattle, horses and value and cell-wall content measured. 22 W ildfow l 39 ( I9XX): 22-2X Andean Geese at Lake Junin 23 Statistics are given in the form of mean ± (Figure 1). The total number counted was standard deviation. DM = dry matter and 1,887. OM = organic matter. Time of day is given The geese at each locality occurred in as hours:minutes. pairs or loose flocks which, at Paucarcoto, numbered several hundred individuals. The flocks also contained pairs and presumably Results family groups since young of other sheld­ geese tend to remain with their parents for Numbers and distribution about eight months after fledging (Summers 1983). However, first-year Andean Geese Most of the geese were encountered in the are not readily distinguished from adults at area to the east of Paucarcoto and smaller this time of year. groups occurred on the west side of the lake Figure 1. Lake Junin and surrounding villages and roads. Numbers indicate the number of Andean Geese at each locality. Diurnal activity lake where they presumably roosted over­ night. Initially, no feeding was observed Observations at Paucarcoto started a few and most geese were standing or preening at minutes after sunrise (06:15 hours), though the water’s edge. Flocks of geese soon it had been light for about half an hour. began to take off and fly 0.5-1 km inland to Most geese were still along the shore of the the surrounding marshes where they grazed 24 Ronald W. Summers and Gonzalo Castro throughout the day. Between 06:20 and was little overlap in the habitats used by 07:30 hours it was extremely cold and frost sheep and geese since the former were covered the ground, and it was not until found grazing on the dry pastures, and the about half the frost had melted that grazing geese were on wetter areas. The geese became intense and formed the main activ­ started to fly back to the roost site on the ity for the day (Figure 2, Table 1). The lake shore about half an hour before sunset. percentage of time spent grazing then decli­ Shortly after sunset practically all the pop­ ned through the middle of the day, but ulation had left the pastures and were intensified again in the latter part. The present along the shore of the lake. Bathing percentage of birds sitting was g reater in the and swimming were noticed at this time. Table 1. Diurnal time-activity budget of Andean Food intake Geese on 3 September at Paucarcoto, Lake Junin. Inter-faecal periods had an average value of Time spent at each activity 359± 158 second (n = 15) for geese observed Activity Hours Percent between 10:00 and 13:00 hours. Thirty faeces were collected and had the following Grazing 8.8 73.3 Standing 1.1 9.2 dimensions and mass: 65±9 x 14±2 mm, a Sitting 0.8 6.6 fresh mass of 9.9+2 . 8 g and dry mass of Preening 0.7 5.4 1.42±0.38 g. The length of the grazing day Walking 0.4 3.5 was 10.5 hours (Figure 2) but one would not Flying 0.1 1.1 expect droppings to be produced in the first Drinking 0.1 0.5 hour of grazing (Ebbinge et al. 1975). Thus Swimming - 0.2 95 droppings would have been produced on Bathing - 0.1 the pastures and a further 25 may be depo­ Agonistic behaviour 0.1 - sited at the roost during the night (Ebbinge 1975; Summers and Grieve 1982). The Total 12.0 100.0 et al. daily output of faecal material would there­ Number of observations 6,462 fore have been 170 g D M o r 135 g O M (Table 2). The OM digestive efficiency was found to be 35% (Table 2) so the daily afternoon compared with the morning. intake would have been 208 g OM herbage Also drinking was more common in the or 235 g DM. Examination of plant remains afternoon, but the percentage preening, in faeces revealed that the diet was mainly walking and standing showed little variation the fleshy-leaved marsh plants that pre­ through the day, apart from around sunrise dominated on the pastures. and sunset (Figure 2). Agonistic behaviour took the form of aggressive posturing (males), inciting behaviour (females) or Discussion short chases (Johnsgard 1965) and formed only a small percentage of the diurnal Numbers and distribution activity despite the high density of geese. Shepherds tending flocks of sheep occas­ The waterfowl at Lake Junin have been ionally put up the grazing flocks of geese surveyed before so that observations on the causing them to fly a few hundred metres to past population size and distribution are an undisturbed locality. Generally, there available. Dourojeanni et al. (1968) Table 2. Organic matter content, calorific value and cell wall content of Andean Goose faeces and clipped herbage, and resulting estimate of digestive efficiency. (DM = dry matter, OM = organic matter). % organic Calorific value % cell wall content OM m atter digestive Sample Kj/g DM Kj/g OM DM OM efficiency Faeces 79.3 16.4 20.7 26.8 33.8 ) ) 35% Herbage 88.5 19.5 22.0 ) Andean Geese at Lake Junin 25 1 0 0 5 0 - 0 20 Walking ~ 3 0 ~ ] • Preening c © o V. o . 0 - 6 0 Standing 3 0 - • • 20n Sitting • • • • • • i i i i i i r r 9 12 15 18 ▲ Sun Time of day Sun rise set Figure 2. Diurnal changes in the percentage of Andean Geese carrying out different activities. The line for grazing is described by the quadratic equation, y = 0.66 x2 - 0.93 x +76.44; r2 = 0.61; F(2,27) = 23.4, PcO.OOOl.