Waterfowl in north Queensland 69 The comparative ecology of waterfowl in north Queensland H. J. LAVERY Introduction conclusions that can be drawn from it. While the ecology of waterfowl in temper­ The study region (outlined in Figure 1) ate Australia has been investigated by is that around Townsville (19°18'S., 146° Frith (e.g. 1961), less is known about the 49'E.) from Ingham extending 200 miles south-eastwards to Bowen and westwards tropical species. Indeed relatively few to Powlathanga, approximately 100 miles studies have been made on waterfowl in the tropics. From 1958 to 1964, therefore, inland across the Great Dividing Range, detailed investigations were made on each which was used to separate the region of the species of Anatidae occurring in into Coastal and Inland areas. Queensland north of the Tropic of Capricorn. These investigations have been the sub­ The species studied ject of a series of detailed papers (Lavery 1966a, b, c, d; 1967a, b, c, d, e; 1969a, b; Fifteen species inhabited the study areas 1970a, b, c, d; Lavery et al. 1968). The during the period of investigation. Four present paper seeks to summarise this were vagrants, namely: Black Swan Cyg­ work and to point out the main ecological nus atratus, Chestnut-breasted Teal Anas Figure 1. Map of northern Australia showing locations of Coastal Study Area (1) and Inland Study Area (2) and relationships of these to rainfall (—) and evaporation rates (---- ). 70 Wildfowl castanea, Australian Shoveler Anas rhyn­ example Frith 1961). The greater part of chotis rhynchotis and Freckled Duck the habitat was available only seasonally. Stictonetta naevosa, with only the Black The rainfall of the tropics is regular, Swan breeding at a few new artificial wet­ 80% occurring during the late summer lands. One species, the Australian Black (November-April), emphasising the changes Duck Anas superciliosa rogersi, was found in wetland acreage. Rather surprisingly the nesting throughout the region. The rest decrease during the dry season was more fell predominantly into two breeding marked in the artificial wetlands (mainly groups, inland and coastal. The inland cattle watering impoundments) which lost breeders were Australian Grey Teal Anas 95% of the 6,585 acres; natural wetlands gibberifrons gracilis, Pink-eared Duck only lost 70% of 4,725 acres. In most parts Malacorhynchus membranaceus, Austra­ of northern Australia the inland areas lian White-eyed Duck Aythya australis show the greatest loss, having lower rain­ and Maned Goose Chenonetta jubata. The fall and higher evaporation rates (Figure coastal breeders were Magpie Goose 1). Anseranas semipalmata, Plumed Whist­ The coastal breeding species have ling Duck Dendrocygna eytoni, Austra­ phylogenetic affinities with the largely lian Wandering Whistling Duck Dendro­ tropical forms, for example Dendrocygnini cygna arcuata australis, Australian Radjah and Cairinini, while the remaining species Shelduck Tadorna radjah rufïtergum, have affinities with the largely temperate- Green Pygmy Goose Nettapus pulchellus zone forms, for example Anatini. The and the Australian Pygmy Goose Netta­ peculiar but common Magpie Goose pus coromandelianus albipennis. The last (Anseranatini) of northern Australia was named has such a limited distribution that more or less confined to the bulkuru sedge comparative studies involving it could Eleocharis dulcis swamps which were the only be undertaken in north-eastern largest single areas of waterfowl habitat Queensland. (Plate VII, p. 64.) in the tropics. On the other hand, the The English names are those used by uncommon Radjah Shelduck, with tem­ Scott (1961). However, other vernacular perate-zone Tadomini affinities, occupied names are preferred in Australia, particu­ no widespread habitat type. The wide­ larly for the Whistling Ducks. Lavery spread distribution of the Black Duck (1965) proposed the names Grass for the suggests the potentially more aggressive Plumed and Water for the Australian and successful nature of temperate-zone Wandering Whistling Ducks. forms; nevertheless the Black Duck in northern coastal Queensland remained dispersed and utilized marginal habitat types such as creeks. The Black Swan in Habitat recent years has also invaded brackish- Within the study region there were 161 water swamps of coastal club rush Scir­ separate localities frequented by water­ pus littoralis on impounded saltpans while fowl. These can be grouped as nine habi­ the Grey Teal has increasingly invaded tat types (Table I), essentially similar to inland breeding grounds formed by stock those in southern Australia (see, for watering dams. Table I. Waterfowl habitat types, their abundance and seasonal fluctuations, in the north Queensland study areas. Permanency and Number of localities Total acreage Type ■water nature* Inland Coastal Wet (April) Dry (November) Grassland P. — 8 200 200 Lake P. F. St. D. 3 — 1225 620 River P. F. R. D. 6 6 135 75 Lagoon P. F. St. Sh. 14 35 595 310 Bay P. S. Td. D. — 1 2 2 Tidal Flat P. S. Td. Sh. — 4 100 100 Creek T. F. R. Sh. 3 6 6 3 Swamp T. F. St. Sh. 11 60 8940 430 Meadow T. F. St. Vsh. — 3 7 _ Saltpan T. S. St. Sh. — 1 100 — 37 124 11310 1740 * Temporary (T) or Permanent (P); Fresh (F) or Saline (S); Static (St.) or Running (R) or Tidal (Td.); Deep, >10 ft. (D), Shallow, <10 ft. (Sh.) or Very Shallow, < 2 ft. (Vsh.). Waterfowl in north Queensland 71 Breeding clutch was successful or until breeding In north Queensland waterfowl nest conditions ceased to be suitable. The almost entirely during and immediately timing of reproduction in all instances following the wet season (Lavery et al. coincided with a number of factors 1968). obviously important for success which Within the breeding ranges all species, developed with the rains. These were with the exceptions of the colony-nesting water depth, percentage of vegetation Magpie Geese and Black Swans, were cover and food production (measured by widely distributed and intermingled on the number of awnless barnyard grass the almost unlimited breeding grounds, Echinochloa colonum seed heads per having similar simple nesting require­ square yard). All these, and gonad size, ments. increased sharply with the rains. The In nearly all species except the longer- relation between the last two for the Wan­ maturing Magpie Geese and Black Swans, dering Whistling Duck and the Black most pairs laid eggs annually and did so Duck over a number of years is shown in repeatedly within each year until a single Figure 2. A severe drought, such as that Wandering W histling Duck mu @ fcMi EUS Clutches begun B la c k D u ck Clutches begun 10 H 1'S K — 11111111 ri 111 rrrrrm » 11 n 11111111111 m m nrnrrn in i » 11 * 1959 1 1960 1 1961 1 1962 1 1963 » Month and year B =• male gonads reproducing b = female gonads reproducing Figure 2. Relationship of reproduction of Wandering Whisding Ducks and Black Ducks to rainfall in north Queensland study areas, where 1961 was a year of severe drought (after Lavery 1970a). 72 Wildfowl experienced in 1961, results in the absence lian populations. The sizes of these of any of these favourable factors and in influxes were related to breeding and the complete cessation of reproduction. post-breeding conditions there, and were Clutch sizes varied somewhat from year readily discernible from resident popula­ to year. Thus for 1961, 1962 and 1963 the tion patterns. Thus the White-eyed Ducks Black Swans averaged 3.50 + 0.38 (24 in June 1969 soared to approximately clutches); 5.12 + 0.24 (58 clutches); and 1,800 birds, whereas the usual population 4.25 ±0.18 (101 clutches). The 1961 was less than 200. Many of these nomadic clutches were significantly smaller (P= flocks continued to move through north 5%). The Black Swan and the other Queensland along fairly well-defined colonial breeder, the Magpie Goose, paths (Lavery 1966b). tended to fledge a higher proportion of the young hatched than did the solitary- Parasites and predators nesting Wandering Whisding Duck and Parasitism and predation are liable to in­ Black Duck (Table II). However, the crease when birds become concentrated. colonies were sometimes completely des­ For the Black Duck (collected 1959-63) troyed by flooding. Thus after four inches 13 out of 42 of those taken in the wet of overnight rain on 25th February 1962, seasons had intestinal helminths, while 102 20 out of 32 Magpie Goose nests forming out of 143 collected in the dry seasons Table II. Reproductive success of some waterfowl species breeding in north Queens­ land, 1959-63. Young downy broods Old flapper broods No. Average No. Average Species examined size examined size Ratio Magpie Goose 3 8.67 + 1.67 11 5.82 ±0.87 0.67 Wandering Whistling Duck 26 10.66 ±0.65 14 4.64 + 0.89 0.44 Black Swan 40 4.38 + 0.24 11 4.09 + 0.46 0.93 Black Duck 21 6.95 + 0.52 5 2.00±1.06 0.29 a colony at Thornley Park, Townsville, were similarly parasitized, i.e. relatively were abandoned. The remainder, all float­ more than twice as many. ing, were saturated and eventually these Various parasite groups occurred on and were also abandoned. in all waterfowl species and many of these The growth curves of the above four parasites had specific hosts (Lavery 1967a). species were also investigated by using High incidences of certain potentially birds raised under aviary conditions at debilitating forms, such as intestinal hel­ Townsville. The three northern species minths, were probably a consequence reached fledging in rather similar times; simply of the hosts’ feeding habits in Magpie Goose in 76 days (20 birds), Wan­ relation to the parasites’ life cycles (Table dering Whistling Duck in 98 days (two III). Thus deep-water divers were most birds) and Black Duck in 100 days (three prone to infection.