WAEIS O A SMA ESUAIE WEA A SI YEA SUY.

PAULINE REILLY

19 Lialeeta Ave, Fairhaven, 3231

Received: 25 July 1996

rd p nd nbr n ll trn tlnd n thtrn tr r rrdd fr x r fr 0 t nlv. Obrvtn r d b tlp t lt n dl nd th x nbr f brd rrdd h hlfnth. t tn f th tr lvl. S nlt nd prfrn fr l t d tr lvl hn. h prnnt tlnd prtnt fr t tht vl, frn r nd rf n t f drht.

INTRODUCTION forms across the mouth of the creek. Stream flow and rain fill the and water spreads into the floodplain. exploit this Estuarine forms a large and important part of increased feeding area and only the largest are visible above the Australian . There are many published papers vegetation. Flooding can occur in wet summers as well as in winter. that relate to large wetlands (Lamm 1965; Briggs 1977; When the sandbar at the mouth of the creek is breached, either Whyte 1981, waterbird numbers relative to water level; by high water levels in the creek forcing its way out or artificially Crome 1988, breeding after drying; Lawler and (a high water level adversely affects dwellings upstream), water flow Briggs 1991; Geering 1993, individual waterbird is confined to the creek bed, with tidal inflow alternately covering species; White 1993 waterbird numbers and Lawler and exposing the . The water is then at its most brackish. et al. 1993, arid zone wetlands), yet none of them are The dominant species of vegetation in the wetter areas are: Juncus estuarine. Norman (1983) recorded Anatid populations krausii, lsolepis nodosus, Gahnia filum, Schoenus breviculmis and in a saline habitat at Corner Inlet, Victoria. Only one Phragmites australis; and above high water level: Poa poiformis, of six wetlands investigated by Gosper et al. (1983) Gahnia radula, Leptospermum continale and Leucopogon parviflora. was subject to tidal fluctuations. Apart from broad A small group of straggling old Melaleuca lanceolata on the sand dune is used almost continuously for roosting by cormorants ecological factors common to all the above studies, the Phalacrocorax spp and occasionally by Great Egrets Ardea alba. investigations by Norman (1983) and Gosper et al. (1983) are the only ones comparable to Mellors The area is used for recreation: , fishing, canoeing, Swamp. The aim of this paper is to detail which windsurfing and swimming, with considerable human activity during the summer holidays. Its main value for humans is aesthetic and as wetland birds use Mellors Swamp, a small estuarine a focus for Aireys Inlet, the village named after the . It also wetland on the Painkalac Creek in south-western acts as a firebreak in the event of bushfire. Until late 1995, all Victoria and how their numbers are affected by season drainage from septic tanks and dwellings on the surrounding hills of or water level or events inland. the Aireys Inlet/Fairhaven village emptied into the Painkalac Creek. Total connection to the sewerage system is to be completed in 1997. STUDY SITE METHODS A small estuarine wetland at Aireys Inlet (38°28'S, 144°06'E), 125 km southwest of , Victoria, is situated on the Painkalac This paper covers the six year period from January 1990 to Creek and extends two kilometres up an open valley, part of which December 1995, with only short gaps in recording, except for an is cleared and used for grazing. The creek, which rises in the forested absence of records for June 1991. My home commands a clear view foothills of the Otway Ranges, was dammed upstream in 1981. This of the whole of Mellors Swamp to the east; the south western corner dam restricts the natural water flow in the creek and periodic releases is about 200 m distant and a (D = 60 mm, F = 415 mm, K = 20 mm) of water in the hotter months during dry years do little to maintain telescope stands in a position available for frequent use. I observed the flow. in early morning and late afternoon, when viewing was at its best, as well as frequently throughout each day. Every half month I The southern portion of the wetland was protected in 1995 by a recorded for each species seen, the maximum number of individuals conservation covenant when the Surf Coast Shire entered into an at any time. I also recorded at the beginning of each half month agreement with the Trust for Nature to give it permanent protection. whether the creek was tidal (i.e. the sandbar was breached) and, if This southern portion is divided by the Great Ocean Road and the not, the level of the water — low, medium or high. If levels altered part south of this road is known as Mellors Swamp, where this study during the half month, this was also noted. species were classed was conducted. At Mellors Swamp there is continual variation from as regular (species present either all the time or at regular intervals); fresh to saline water with tidal inflow. irregular (species present often but at irregular intervals); or Mellors Swamp is bounded on the north and west by the Great occasional (species rarely present). Ocean Road, on the south by a high sand dune separating it from Bass Strait, on the east by a sandstone cliff and coastal heath, thence Bird species excluded to a gravel road bordered by dwellings (Fig. 1). lt covers Some birds were excluded from the counts: approximately 24 ha. In 1983 before the start of this study a portion was excised by filling and by slashing of the border vegetation to • Those birds inhabiting the floodplain vegetation that could not be create an emergency refuge in case of bushfire. Periodically a sandbar identified on a daily basis through the telescope: Quail Coturnix variations of change in bird numbers unless the levels changed at the beginning or end of a recording period. For instance, an excerpt from my records reads: `January 1990 creek mouth closed but mudflats dry and exposed; rain 1 February mudflats covered; 3 February flooded; 11 February sandbar breached; 16 February creek mouth closed'. Throughout the year, total bird numbers tended to be greatest when the water level was between low-and- medium, decreasing as it rose towards medium and high. Total bird numbers were fewest when the wetland was tidal and the sandbar had been breached, except for the few days immediately after breaching of the Figure 1. Map of Mellors Swamp. sandbar. Figure 3 shows the average over all years of waterbird numbers at the different levels.

spp, Latham's Snipe Gallinago hardwickii, Purple Swamphen Usually after breaching of the sandbar, there was a Porphyrio porphyrio, Dusky Moorhen Gallinula tenebrosa, Blue- slight increase in the number of individuals present for winged Parrot Neophema chrysostoma, White-fronted Chat a few days but in 1994 the result of breaching was Ephthianura albifrons, Clamorous Reed Warbler Acrocephalus spectacular. The creek mouth had remained closed for stentorus, Golden-headed Cisticola Cisticola exilis and Little a year, apart from a period of two days, during which Grassbird Megalurus gramineus. I regarded a Swamp Harrier Circus time the waters ran low, medium and high again, until approximans, observed on four occasions only, as a visitor from more extensive areas of open water and swampland further inland. the night of 12 October 1994. Pressure of water had Small waders were infrequent and not clearly identifiable from a caused the entire bar to break with rapid emptying of distance: Red-capped Plover Charadrius ruficapillus, Black-fronted the estuary. Hundreds of , many still alive, lay on Dotterel Elseyornis melanops and Hooded Plover Thinornis the banks. There was a big influx of waterbirds. Pacific rubricollis; Herons, sporadic visitors, numbered 38 and White- • Pacific Gull Larus pacificus and Crested Tern Sterna berg ii, that faced Herons numbered 68; only one or two birds of sheltered on the wetland during rough weather, were counted but the latter species had been present for the previous six not included in the analysis as they are not confined to wetlands. weeks. Exactly one year later in October 1995, the Silver Gull Larus novaehollandiae was treated similarly. Though creek mouth breached in its normal fashion. This did normally few in number, they arrived in their hundreds when the mudflats dried out completely in autumn 1992 and large numbers not produce any spectacular results. of crickets emerged. Water levels Number of species Water levels were variable and recorded as:. The total number of species recorded was 33 Tidal: Periods when the creek mouth was open, the mudflats (excluding the 16 mentioned in the Methods), of which exposed and the creek confined to its course. Tides flowed 7 were regulars, 9 irregulars and 17 occasional (Table through the mouth and daily high :ides inundated the 1). The number of species per half month fluctuated mudflats. from 14 to 4. Fewer species were present when the Non-tidal: mud flats were exposed or covered tidally a few days after opening of the creek mouth. Seasonally, species Low — The creek was confined to its course or there was a thin numbers were scored for all years and varied little: layer of water on the mudflats. Before the sandbar had a chance to build up after recent closure, high seas washed in there were 22 species present in spring, 23 in summer, and increased the water level. 24 in autumn, 24 in winter (Table 2). The number of species per year varied little: 23 in 1990, 22 in 1991, Medium — The mudflats were well covered with water. 20 in 1992, 21 in 1993, 22 in 1994 and 19 in 1995 High — Water reached the edge of the vegetation on the sand (Table 3). dune side and seeped into the grassland. This category included flooded levels, when the water was deep and grasslands were still emergent but waterlogged. Flooded levels Number of individuals were short-lived. They always resulted in breaching of the sandbar either naturally or artificially. The total number of individuals showed a change with seasons. Numbers were greatest in autumn (101.1 individuals, 39 per cent of annual total), dropping RESULTS through winter (51.9 individuals, 20 per cent of annual Fluctuations with changing water levels total) and spring (37.0 individuals, 14 per cent of annual total), lowest in November and rising in late Results for the fluctuations of species both seasonally summer (68.7 individuals, 27 per cent of annual total) and with changing water levels are presented (Table 2). No annual seasonality was apparent for 37 graphically in Figure 2 for the 12 more common sightings of occasional species, though these were species. The scale of recording of water level was too fewest in spring (six) as against 10 or 11 in the other coarse (that is, half monthly) to show the small seasons. Figure 2. Maximum half-monthly counts for the 12 more common waterbirds recorded for the six years 1990 to 1995 inclusive. Top row indicates the seasons (lowest row of dots = spring; highest row = winter). Next 12 rows show maximum numbers per species per half-month. Species numbers as per Table 1. Penultimate row shows total for all above species of waterbirds. Bottom row shows water level recorded (lowest row of dots = low, medium, and highest row = high), with gaps in record showing when sandbar was breached and water levels were tidally influenced. The y-scale for each species is according to its maximum abundance (see Table 1).

The number of individuals per year dropped each birds sailing together as pairs with necks hooked year from 80.2 individuals in 1990 to 49.3 individuals followed by heads pointed upwards. Pairs have courted in 1995, with the exception of 1994 (72.8 individuals) in May and copulated at the end of September. I when there was an increase over the previous year's believe there to be only one resident pair but I was total (Table 3). Bird numbers were highest in the drier unable to find a nest closer than the Angahook Park hot months generally coinciding with low rainfall and swamp which is 2 km distant on Distillery Creek near low water levels (Table 2). its junction with Painkalac Creek. This swamp has been used when full of water by a pair of breeding Fluctuations in number of twelve species swans each year and a pair with cygnets was observed I selected the 12 more common species for which on Mellors Swamp, possibly the same pair that I regard there were more than 100 half-monthly records during as resident. the six years of the study, (a total of 144 half-months). PACIFIC BLACK DUCK Anas superciliosa — Figure 2 shows the relative but not actual fluctuation Numbers of this species were also highest in autumn in numbers (the y-axis is not constant). and lowest in spring (Table 2). Annual numbers show

BLACK SWAN Cygnus atratus — Seasonality was a trend towards decline, except for an increase in 1994 evident with numbers highest in autumn and lowest in (Table 3). Some birds were usually present whatever spring (Table 2). The mean number of Black Swans the water level but numbers appeared to decrease with fluctuated annually (Table 3) but no trend was evident. higher water levels (Fig. 2). Birds fed together as a Water level had little effect on numbers (Fig. 2). I flock with few outliers, on exposed mudflats kept wet watched communal courtship of ten pairs where wings by tidal action. I watched a Swamp Harrier harass a were lifted displaying extensive areas of white, the single Pacific Black Duck on the water by repeatedly swooping at it, then landing on it and holding it underwater until it drowned and eventually flying with it to the bank and eating it. I noted copulation on the water in September 1995 and later a pair with young. The water level was high at that time and they may have nested on Mellors Swamp. GREY TEAL A. gracilis — This species appeared irregularly, with numbers highest in summer/autumn and lowest in spring (Table 2). Numbers increased annually from 4.1 birds in 1990 to a peak of 7.2 birds in 1992 but declined to 1.1 birds in 1995 (Table 3). Water level did not appear to affect numbers. HOARY-HEADED GREBE Poliocephalus poliocephalus — This species was present irregularly. The greatest mean number was recorded in winter (Table 2). Water level did not appear to affect numbers. GREAT CORMORANT Phalacrocorax carbo — This species was nearly always present (Fig. 2) and there Figure 3. Average numbers of waterbirds taken over all years for each was no correlation between numbers and water levels. water level. Numbers were greatest in spring and lowest in autumn (Table 2). Numbers increased from 0.9 birds in1990 to two Great Egrets were present, one continually chased 5.6 birds in 1993 and have been maintained at a similar the other not allowing it to settle and eventually driving level since (Table 3). In August 1995, I noted courtship it away. of a pair, posturing and picking up grass on the mudflats, though normally courtship takes place at the AUSTRALIAN WHITE IBIS Threskiornis molucca — nest. This species visited irregularly but was most likely to be present in autumn (Table 2). LITTLE PIED CORMORANT P. melanoleucos — This species was nearly always present (Fig. 2) and YELLOW-BILLED SPOONBILL Platalea flavipes — there was no correlation between numbers and water This species was a regular visitor in small numbers, levels. Numbers did not vary much but were slightly the greatest numbers recorded in autumn (Table 2). greater in autumn/winter (Table 2). There appeared to Numbers fluctuated annually with the highest average be a slight upward annual trend (Table 3). numbers (2.1 birds) in 1992. LITTLE BLACK CORMORANT P. sulcirostris — ROYAL SPOONBILL P regia — A few of this species This species appeared in winter with some overlap into appeared irregularly and fed together with Yellow- early spring (Table 2). Annual numbers were constant billed Spoonbills. Both spoonbills were observed to except for an increase in 1991/92 (Table 3). follow a feeding White-faced Heron. WHITE-FACED HERON Egretta novaehollandiae — MASKED LAPWINGS Vanellus miles were always During the six years of the study, annual numbers rose present, usually only one or two pairs. Annual numbers to a high of 7.2 birds in 1994 to drop to a low of 1.6 were highest in 1992 (Table 3) and in autumn (Table birds in 1995 (Table 3). Usually two birds were present 2). Nests or a pair with young were noted regularly. with a short-lived influx after breaching of the sandbar, Numbers increased coinciding with the inlux of particularly in spring 1994. One bird had been present crickets in autumn 1992. in two of the three preceding half-months but after the breaching 68 birds appeared for a few days. No Uncommon visitors variation with season was apparent (Table 2). Only one CAPE BARREN GOOSE Cereopsis novaehollandiae adult was present daily during breeding in August 1995 — One was present continuously for three months when it nested high in a Red Ironbark Eucalyptus from March to June 1990, the first record for the sideroxylon about 50 m from the creek and about district. It was not wary of people which suggests it 300 m north of Mellors Swamp. Four young hatched. may have been bred at Serendip Sanctuary 60 km The pair later returned to Mellors Swamp with at least distant where birds of this species are accustomed to one young. I observed a White-faced Heron being people. It fed on emergent vegetation but when this followed by both Royal and Yellow-billed Spoonbills became inundated it moved to grass on the road verges which apparently fed on prey it had disturbed. and was eventually hit by a car and its wing was broken. It did not survive. GREAT EGRET Ardea alba — When this species was recorded, there was usually only one individual present. AUSTRALIAN PELICAN Pelecanus conspicillatus — In most years the species was absent from October to Rarely recorded in the past, one was present in very February or March except for 1994 (Fig. 2). Whenever low water in February 1995. TABLE 1 All waterbird species recorded on Mellors Swamp from 1990-1995 inclusive, showing their status (Regular, Irregular, Occasional) and the greatest number present at any one time. Numbers assigned to species are for the purpose of reference for other tables and figures.

Maximum Number Species Status of Individuals 1 Blue-billed Duck Oxyura australis Occasional 1 2 Musk Duck Biziura lobata Occasional 1 3 Black Swan Cygnus atratus Regular 32 4 Cape Barren Goose Cereopsis novaehollandiae Occasional 1 5 Australian Shelduck Tadorna tadornoides Irregular 10 6 Australian Wood Duck Chenonetta jubata Irregular 15 7 Pacific Black Duck Anas superciliosa Regular 140 8 Grey Teal A. gracilis Irregular 52 9 Chestnut Teal A. castanea Occasional 4 10 Pink-eared Duck Malacorhynchus membranaceus Occasional 9 11 Hardhead Aythya australis Occasional 2 12 Hoary-headed Grebe Poliocephalus poliocephalus Irregular 8 13 Darter Anhinga melanogaster Occasional 1 14 Little Pied Cormorant Phalacrocorax melanoleucos Regular 10 15 Little Black Cormorant P sulcirostris Irregular 38 16 Great Cormorant P carbo Regular 28 17 Australian Pelican Pelecanus conspicillatus Occasional 1 18 White-faced Heron Egretta novaehollandiae Regular 68 19 White-necked Heron Ardea pacifica Irregular 38 20 Great Egret E. alba Regular 4 21 Intermediate Egret A. intermedia Occasional 1 22 Cattle Egret A.ibis Occasional 3 23 Australasian Bittern Botaurus poiciloptilus Occasional 1 24 Australian White Ibis Threskiornis molucca Irregular 25 25 Straw-necked Ibis T spinicollis Occasional 3 26 Royal Spoonbill Platalea regia Occasional 4 27 Yellow-billed Spoonbill P flavipes Irregular 11 28 Eurasian Coot Fulica atra Occasional 2 29 Black-winged Stilt Himanotopus himantopus Occasional 2 30 Banded Stilt Cladorhynchus leucocephalus Occasional 5 31 Masked Lapwing Vanellus miles Regular 24 32 Caspian Tern Sterna caspia Irregular 3 33 Whiskered Tern Chlidonias hybridus Occasional 6

WHITE-NECKED HERON Ardea pacifica — This DISCUSSION species visited irregularly, often singly, but after the There was no clear-cut reason for presence or creek mouth breached in spring 1994, 38 birds were absence of waterbirds on Mellors Swamp, though there present for a few days. was seasonality with some species (Black Swan, Little AUSTRALASIAN BITTERN Botaurus poiciloptilus Black Cormorant, Great Egret, Australian White Ibis, — One bird was observed on seven different occasions Yellow-billed Spoonbill) suggesting dispersal to and from May to August 1995. Six sightings were in the from breeding areas. Combined with this seasonality, south-western corner bordering the water and one was during the peak of summer holidays (Christmas and further along towards the creek mouth. All sightings most of January) disturbance caused by the influx of were in full daylight. It may have been overlooked in human visitors may have kept waterbirds away. the past because of its cryptic colouring and its habit The drop in number of individuals (Table 3) over the of stalking and freezing. It moved away when a White- six years probably results from the decline in numbers faced Heron approached. of Pacific Black Ducks that comprised a large proportion of the total. INTERMEDIATE EGRET Ardea intermedia — One in March/April 1993 and one in July 1994. Water level did have some effect. When water was confined to the course of the creek with dried mud BLACK-WINGED STILT Himantopus himantopus — surrounding, few birds were present. When daily high Two in December 1992. tides washed over the dried mud, Pacific Black Duck BANDED STILT Cladorhynchus leucocephalus — fed on the mudflats. During high water levels, some Five in January 1995. species exploited the changed conditions of the floodplain where only long-legged species (for example

WHISKERED TERN Chlidonias hybridus — Six Great Egret, White-faced Heron) were evident above fishing in October 1994, three in breeding plumage. the vegetation. These flooded conditions were usually TABLE 2 by waterbirds in the Murray-Darling Basin during 1994 The mean number of each waterbird species recorded over the six (Hutchinson 1996) and their dispersal towards more years in each seasonal period on Mellors Swamp. Species numbers permanent wetlands. In that year also a Great Egret as per Table 1. * Indicates species present in low numbers. was present throughout the year although this species was usually absent during spring/summer. Conversely, Species Season in 1995 the wet conditions that prevailed over a large No Spring Summer Autumn Winter area of the inland would have provided good foraging 1 0.0 0.0 * 0.0 0.0 conditions and possibly were the reason fewer birds 2 0.0 0.1 0.0 0.0 were present on Mellors Swamp. Woodall (1985) found 3 2.9 5.0 13.1 7.7 a positive correlation between inland rains and lower 4 0.0 0.0 0.2 0.0 * 5 0.5 1.1 0.7 0.4 bird populations on the coast. Reasons for fluctuations 6 0.1 0.0 0.0 * 0.9 in bird numbers may depend upon environmental 7 10.6 42.2 59.3 8.5 conditions both at the study area and at a remote site 8 0.8 5.8 5.1 3.0 at anything up to ten years earlier, not just the previous 9 0.1 0.2 0.1 0.2 year (White 1993). 10 0.0* 0.0 0.3 0.0 11 0.1 0.0 0.0 0.0 The substrate of Mellors Swamp has altered over the 12 0.3 0.1 1.0 2.0 period of this study by the clearing of vegetation and 13 0.1 0.0 0.0 0.0* 14 1.9 1.5 2.4 2.5 construction of a track along the western side of the 15 2.4 0.0* 0.1 3.2 wetland on the north side of the Great Ocean Road. 16 7.2 2.5 0.8 3.0 Surfaced with yellow gravel, the track has eroded 17 0.0 0.0* 0.0 0.0 18 4.5 4.0 5.6 4.6 19 1.6 0.0* 0.4 0.4 20 0.6 0.5 1.5 1.2 TABLE 3 21 0.0 0.0 0.1 0.0* The mean number of each waterbird species recorded over the six 22 0.0 0.0 0.3 0.1 years in each calendar year on Mellors Swamp. Species numbers as 23 0.0 0.0 0.0* 0.1 per Table 1. * Indicates species present in low numbers. 24 0.2 0.6 1.8 0.2 25 0.0 0.0 0.3 0.0 Species Year 26 0.0* 0.4 0.4 0.1 No 1990 1991 1992 1993 1994 1995 27 0.1 0.2 1.8 0.8 1 0.0 0.0 0.0 0.0 0.0* 0.0 28 0.0 0.1 0.0 0.0* 2 0.1 0.1 0.0 0.0 0.0 0.0 29 0.0 0.1 0.0 0.0 3 9.0 9.2 3.9 4.9 9.0 6.8 30 0.0 0.1 0.0 0.0 4 0.3 0.0 0.0 0.0 0.0 0.0 31 2.5 3.5 6.7 2.9 5 1.0 0.4 0.3 0.5 1.0 1.0 32 0.3 0.7 0.1 0.1 6 0.0 1.2 0.0* 0.0 0.3 0.0 33 0.2 0.0 0.0 0.0 7 48.8 32.3 31.4 25.5 35.2 23.4 Total Birds 37.0 68.7 101.1 51.9 8 4.1 4.8 7.2 3.3 1.9 1.1 9 0.2 0.1 0.3 0.2 0.0 0.0 Total number of 10 0.0 0.0 0.0 0.4 0.0 0.0 species present 11 0.0 0.0 0.0 0.0 0.1 0.0 per season over 12 0.4 1.4 1.8 0.4 0.9 0.2 all years 32 23 25 25 13 0.0 0.1 0.0* 0.0* 0.0 0.0 14 1.6 1.7 1.3 1.6 2.5 3.8 15 0.6 2.8 3.1 0.6 0.6 0.6 16 0.9 1.6 2.5 5.6 5.0 4.6 short-lived. The creek mouth normally began 17 0.0 0.0 0.0 0.0 0.0 0.0* discharging with a slow trickle of water through a 18 5.7 4.8 3.0 5.6 7.2 1.6 narrow opening which eroded to permit a fast flow or 19 0.0* 0.4 0.2 0.3 2.7 0.0 else it was opened officially by mechanical means or 20 1.1 0.9 0.9 1.0 0.8 1.0 unofficially by manual means. Low-to-medium water 21 0.0 0.0 0.0 0.1 0.0* 0.0 22 0.2 0.1 0.0 0.1 0.1 0.0 levels carried the greatest number of birds, although 23 0.0 0.0 0.0 0.0 0.0 0.2 there was usually an increase in bird numbers 24 0.8 1.0. 0.2 0.8 1.5 0.0 * immediately after breaching of the sandbar. This 25 0.4 0.0 0.0 0.0 0.0 0.0 increase was not invariable. For instance, the creek 26 0.4 0.1 0.3 0.3 0.2 0.0* mouth was closed from mid-November 1994 to mid- 27 0.6 0.6 2.1 0.1 0.7 0.1 June 1995 but after opening the numbers of birds 28 0.0* 0.1 0.0 0.0 0.0 0.0* 29 0.1 0.0 0.1 0.0 0.0 0.0 remained the same as in the previous six weeks. If bird 30 0.0 0.0 0.0 0.0 0.0 0.2 numbers varied only with season, then a spring break- 31 3.8 3.0 6.1 3.5 2.6 4.3 out of the sandbar (the period of lowest bird numbers) 32 0.5 0.3 0.3 0.1 0.2 0.4 should not result in a large increase of numbers as it 33 0.0 0.0 0.0 0.0 0.3 0.0 did in October 1994. Total 80.2 67.0 65.0 54.8 72.8 49.3 Annual numbers of birds showed a steady decline Percentage apart from 1994 which was inflated by the influx in total October, perhaps the result of greatly reduced breeding individuals 20.6 17.2 16.7 14.1 18.7 12.7 during heavy rain and the yellowing of the substrate septic tanks draining effluent into the wetland, water on the shallow area in the south-western corner is quality of the wetland is expected to improve. What noticeable, possibly impacting adversely on underwater effect this will have on the waterbird population will invertebrates. Care needs to be taken where native not be evident for some years. Continued monitoring vegetation (see Study Site, below the road ) bordering is needed to identify problems immediately they arise. the water is replaced. Kikuyu grass on a gently sloping bank, the upper part of which had been mown, acted ACKNOWLEDGMENTS as a sieve which trapped hundreds of fish during the explosive breaching of the sandbar in 1994. I thank Prof. J. M. Cullen who helped in the analysis and presentation of the data, Will Rolland for producing the map, Winston Powered boats were prohibited at the beginning of Huggins for botanical information and two unnamed referees who the survey period and so could not be implicated in greatly improved this paper. I am also grateful to the editor of Corella the reduction in numbers of waterbirds. On several who patiently advised and assisted throughout the revision. occasions I observed a fox Vulpes vulpes, once with young, on the wetland openly in daylight. On one such REFERENCES occasion, an Australasian Bittern and a White-faced Briggs, S. V. (1977). Variation in waterbird numbers at four Heron continued to forage undisturbed within easy on the northern tablelands of New South Wales. Aust. Wildl. Res. reach of the fox but it made no attempt to attack them. 4: 301-9. Two untended dogs were noted rampaging through the Crome, F. H. J. (1988). To drain or not to drain? — intermittent wetland on several occasions and were reported to have swamp drainage and waterbird breeding. Emu 88: 243-248. killed some waterfowl, species not stated. I do not Geering, D. J. (1993). The effect of -breaking rain on the know whether by either of these species re-establishment of egret colonies in north coastal New South contributed to changes in the size of the bird Wales. CoreIla 17: 47-51. Gosper, D. G., Briggs, S. V. and Carpenter, S. M. (1983). Waterbird population that I monitored. Dynamics in the Richmond Valley, New South Wales, 1974-77. Unlike Maddock (1991) who reported a White-faced Aust. Wildl. Res. 10: 319-27. Heron feeding on prey disturbed by a Royal Spoonbill, Hutchinson, M. (1996). Murray-Darling Basin Waterbird Project my observation was the reverse. Both species of Update — Birds do it ... Wingspan 6: 19. Lamm, D. W. (1965). Seasonal counts of birds at George, New spoonbill walked behind a White-faced Heron. South Wales. Emu 64: 115-128. Although the size of the waterbird population on Lawler, W. and Briggs, S. V. (1991). Breeding of Maned Duck and Mellors Swamp is small, the six year study has other waterbirds on ephemeral wetlands in north-western New South Wales. provided some understanding of the dynamics of birds Corella 15: 65-76. Lawler, W., Kingsford, R., Briggs, S. V. and Milkovits, G. (1993). on a small estuarine wetland. The drop in annual Movements of Grey Teal Anas gracilis from a drying, arid-zone numbers needs to be interpreted with caution. It may wetland. Corella 17:58-60. be the result of increased rainfall inland. Fluctuations Maddock, M. (1991). Observations on the biology of the White-faced in the size of the bird populations from year to year Heron Ardea novaehollandiae. Corella 17: 79-86.15, may not have been evident in a study covering a Norman, F. l. (1983). Grey Teal, Chestnut Teal and Pacific Black Duck shorter period (Table 3, Fig. 2). This permanent at a saline habitat in Victoria Emu 83: 262-270. wetland is important for its aesthetic value and as a White, J. M. (1993). Changes in the numbers of waterbirds on firebreak in the event of bushfire. For birds, it is a Llangothlin, New South Wales, in relation to the water level and foraging area and a refuge in times of drought. The distant flooding, 1981-84. Corella 17: 117-121. human population, both permanent and semi- Whyte, R. J. (1981). Winter fluctuations in waterbird numbers on a northern tablelands of New South Wales. Emu 81: 243-6. permanent, of Aireys Inlet and Fairhaven has shown a Woodall, Peter F. (1985). Waterbird populations in the Brisbane steady increase. With the new sewerage system region, 1972-83, and correlates with rainfall and water heights. disposing sewage and waste water inland instead of Aust. Wildl. Res. 12: 495-506.