49th ANNUAL ASSESSMENT OF SHEARWATER BREEDING SUCCESS ON MONTAGU ISLAND,
25th MARCH – 1st APRIL 2008
The format of this report and the abbreviations used therein are consistent with those in previous annual reports (e.g. Davey et al. 2007). The study area on the south-eastern side of the smaller northern part of Montagu Island is known as NISA (293 m2); the two study areas at the northern end of the southern part are known as SISA (428 m2) and THISA (293 m2). Their position is shown on the maps in the report on the size of the shearwater breeding population on Montagu Island (Fullagar and Heyligers 1998). The bird records for the island have been reviewed by Fullagar (1989). Names of all vertebrates follow Clayton et al. (2006). Names of butterflies follow Braby (2004) and moths follow Common (1990) whilst those of vascular plants follow those used by Heyligers and Adams (1989, 2004).
Weather and Habitat Conditions
We departed Narooma at 09:45 on 25th March crossing to the island in overcast conditions with rain threatening. There was a low swell with a light northerly wind. Little was seen during the crossing and the weather deteriorated during the reminder of the day with frequent showers and some periods of steady rainfall such that no work was possible on the study areas for that day. The wind increased all day but overnight the rain cleared to give fine weather for the following seven days with only light breezes, although a sharp thunder storm built up at dusk on the 26th with a brief period of rain and scattered hail and there was a spectacular ‘silent lightning display’ to the north east during the night of the 29th. Overnight on 30th it was cloudy and windy but the following night was clear and dawn on the 1st April was calm and hazy. Generally the wind was from the north throughout most of our stay.
Rainfall figures (mm) for the twelve months (April 2007 to end of March 2008) are as follow: 116.8; 35.6; 216.0; 19.2; 35.2; 22.2; 70.6; 109.2; 63.0; 85.6; 141.2 and 28.2. The highest daily falls during the shearwater breeding season between October and March included a fall of 37.4mm in November and another of 42.8mm in February but these would not amount to any likelihood of serious burrow flooding. The island appeared lush and growth of plants on areas newly vegetated in August last year had advanced spectacularly. All three study plots were well vegetated with no significant open ground on any of them. A small intrusion of Kikuyu grass Pennisetum clandestinum was found at one point just inside the northern edge of SISA and another small patch was found just beyond the southern limits of the plot.
Coverage
We started work on NISA at 08:50 on 26th and finished this plot by 15:40 the same day. We then moved to THISA and made a start on this second plot at 16:30 working until 17:50. On the 27th we resumed work on THISA at 07:45 completing the plot by 09:10. We then moved to SISA beginning work at 09:20 and finishing this last plot at 17:15. For the first time all three plots were finished within two days!
Apart from observations made while on the study plots we explored both islands. A short trip by inflatable dinghy was made to the seal colony on the west side of North Island in the late afternoon on 28th to investigate a reported sighting of a noddy tern. North Island was visited on the 30th and South Island was surveyed each day 28-31st, mostly on the western and southern sides. We returned from the island at 09:00 on 1st April in calm conditions.
Survey Team
Vanessa Place, Daniela Binder, Peter J. Fullagar, Amy Jorgensen, Mavis Russell and Naoko Takeuchi.
Survey Results
The results of this year’s survey, together with those of last year, are summarised in Table 1.
Table 1. Number of shearwater chicks and number of burrows found in the three study areas this year and last year (figures in brackets), together with the totals for both years.
Short-tailed Shearwater P. tenuirostris chick numbers were far short of the long-term averages on NISA, THISA and SISA (33.0, 17.0 and 54.2 respectively). However, the general condition of this species was good with the mean weight being 658g (the lightest was 300g and the heaviest was 934g) and 80% of chicks were still completely down covered. Compared with the previous season there were less than half as many chicks of this species on the study plots.
Two Sooty Shearwater P. griseus chicks were found, one (1225g) on THISA and one (1045g) on SISA.
Burrow occupancy was low with at least two thirds of burrows on all three plots being found to be empty.
General observations of birds, mammals, reptiles and Lepidoptera
During the period since the last survey on Montagu Island an intensive House Mouse Mus musculus eradication has occurred and a 2.5 Ha. portion of the island east of the North Landing jetty has been burned and revegetated with Coastal Wattle Acacia longifolia var. sophorae, Coast Rosemary Westringia fruticosa, Coast Banksia Banksia integrifolia, Swamp Oak Casuarina glauca, Spiny-headed Mat-rush Lomandra longifolia, Giant Honey-myrtle Melaleuca armillaris, and Bangalay Eucalytus botryoides. Other additional plantings of most of these species have occurred in areas previously re-vegetated and on all re-vegetation plots plants have grown very well over the last twelve month period.
Birds
Little Penguin Eudyptula minor. Little activity ashore. No counts were made of birds coming ashore in the evenings. The birds recorded ashore were an occasional individual in the numerous nestboxes or were seen along a track. No calling was evident at night.
Wedge-tailed Shearwater Puffinus pacificus, Sooty Shearwater P. griseus and Short-tailed Shearwater P. tenuirostris. See text above. Only small numbers of Wedge-tailed Shearwaters occasionally seen at sea during the day and a visit to the colony area north-east of the light station on the night of 31st revealed some Wedge-tails landing and a few calling from burrows.
Australasian Gannet Morus serrator. Few, mostly immatures. Most of the time a scan of the sea revealed no birds other than a few Silver Gulls near fishing boats.
Little Pied Cormorant Phalacrocorax melanoleucos. One reported 27th.
Great Cormorant Phalacrocorax carbo. One on west side of North Island on 26th and another east of the Gulch in the late afternoon on 27th and another west of the jetty in the morning on 28th. A maximum count of 3 on 29th along western shore of South Island and again in this area two birds often seen resting on rocks on subsequent days.
White Faced Heron Ardea novaehollandiae. One bird on rocks north of jetty at North Landing in the late afternoon of 28th. Eastern Reef Egret Egretta sacra. One dark morph bird seen at dusk foraging on rocks at North Landing. Cattle Egret Bubulcus ibis. One flying south over the sea to the west of the island on 31st.
White-bellied Sea-Eagle Haliaeetus leucogaster. Observed every day with a maximum of 6 individuals; aged as three adults, a sub-adult and two first year birds. The three adults were most often seen and appeared to roost each night on the island. Swamp Harrier Circus approximans. One bird flying SE past the light station in the early afternoon on 28th. It remained only briefly on the island. Two flew north in the early morning of 29th. It is notable that at no time was a harrier seen quartering over any part of the island during this trip. Peregrine Falcon Falco peregrinus. Three birds on 26th but thereafter no more than a single bird was seen at any time. Most mornings a Peregrine circled south over South Island soon after dawn. Australian Kestrel Falco cenchroides. Male and female seen often using roost sites on the window ledges of the lighthouse or foraging over the north end of South Island.
Sooty Oystercatcher Haematopus fuliginosus. Two on 28th at North Landing jetty in the late afternoon. Both were showing signs of active wing moult. Maximum count would include two often seen at the jetty and another three seen on the east side of South Island with possibly two more individuals at the South Landing. Count would have been 5-7.
Silver Gull Larus novaehollandiae. Small numbers at sea and around island every day. Two adults with two fledged young were found below and to the north-east of the light station near the track. Caspian Tern Sterna caspia. One bird on 25th quartering inshore off the west side of South Island and again on 31st and 1st April.
Crested Tern Sterna bergii. Notably absent but one on west of island on 31st and two offshore from the North Landing together with a Silver Gull on the 1st April.
Brown Noddy Anous stolidus. One seen and confirmed as this species in the late afternoon on 28th. The individual was with Silver Gulls resting ashore amongst the seal colony on the west side of North Island south-west of Pebbly Beach. It was a first year bird and had been reported as present in this area for some days before we confirmed its identity.
Common Bronzewing Phaps chalcoptera. One flushed from track alongside the Acacia thicket at mid-day on 31st.
Shining Bronze-Cuckoo Chrysococcyx lucidus. One calling at far south end of track on South Island during the morning on 30th.
Yellow-faced Honeyeater Lichenostomus chrysops. A small party of 5-10 at the end of the track to the southern end of the South island on 29th. Others were seen or heard from time to time. Golden Whistler Pachycephala pectoralis. An immature or female bird seen in the Acacia thicket on the 31st. Leaden Flycatcher Myiagra rubecula. A female was seen near South Landing on 29th. Grey Fantail Rhipidura fuliginosa. Maximum of three in Acacia thicket on 28th and one seen 31st in this same area. Willie Wagtail Rhipidura leucophrys. One on SISA in the morning on 27th. Black-faced Cuckoo-shrike Coracina novaehollandiae. An immature bird foraging over Coast Banksia alongside the path to the South Landing on 29th. Probably the same individual seen along the main track to North Landing during the morning of 30th and again on the 1st April. This bird was having trouble trying to dismember a very large grasshopper on 30th. Australian Pipit Anthus australis. One at light station and another, or the same individual, at the jetty on 28th in the afternoon and again at one or other of these locations on subsequent days. Welcome Swallow Hirundo neoxena. Seen each day. Individuals seen on both islands. Two regularly at the light station and these birds were using the mower shed to roost; another two were using the boatshed at the North Landing with two more in this area or at the old gardens in the north west of South Island; three presumably different individuals were seen in the north-west of North Island on 30th with another at the gulch in the north-east of North Island that day. Maximum count therefore would likely be 7-10. Little Grassbird Megalurus gramineus. Inconspicuous at this time of the year but some birds heard calling occasionally and a few seen most days. Golden-headed Cisticola Cisticola exilis. Not vocal and difficult to detect but a few birds seen each day. Silvereye Zosterops lateralis. Small parties heard each day with up to 30 near South Landing on 29th and on subsequent days. All observed were the Tasmanian sub-species.
Mammals
House Mice Mus musculus. None present. Eradication seems to have been successful. European Rabbits Oryctolagus cuniculus. None observed. Presumed to be eradicated.
Seals.
Approximately 150 seals estimated to be present on the island. The Australian Fur Seal Arctocephalus pusillus doriferus and the New Zealand Fur Seal Arctocephalus forsteri was observed but no count of individual species was attempted. Several pups were observed amongst those hauled out on the west side of North Island. Three haul-out sites were in use. The rock platform to the north west of North Island (c. 30 seals); the rocks at the southern end of Pebbly Beach (75-100) and the rocky islet to the south-west of South Island and south of the South landing (c20). No seals were using the traditional site in the north-east of North Island.
Bottle-nosed Dolphin Tursiops truncates. A pod of at least 40 was cavorting east of the island in the late afternoon on 25th.
Reptiles
Both species known to occur on the island, White’s Skink Ergenia whitii and Grass Sun-skink Lampropholis guichenoti were observed occasionally and throughout the island.
Lepidoptera
Butterflies were conspicuous. The Common Brown Heteronympha merope was particularly numerous along paths, mostly on the west side of South island, throughout our visit. Also found was a superb specimen of a Tailed Emperor Polyura sempronius which was discovered inside the empty shade house along with an unidentified hawk moth (Sphingidae) on 30th. A Black and White Tiger Moth Spilosoma glatignyi was observed on the path alongside the Acacia thicket on 29th. Lycaenid blues of at least two unidentified species were often observed along pathways together with a very small Hesperid skipper. Cabbage White Pieris rapae were numerous on 31st suggesting an overnight arrival and two other butterflies, a Black Jazebel Delias nigrina and some Spotted Jazebel Delias aganippe were seen at the southern end of the island on 31st. Also present that day were several Australian Painted Lady Vanessa kershawi and, like the Cabbage Whites, these appeared to be recent arrivals.
Acknowledgments
We are indebted to the NSW National Parks and Wildlife Service for hospitality while on the island and thank Ross Constable and Paul Bourke for assistance with transport as well as Andy and Lisa Young for allowing us to share accommodation with them.
References
Braby, M.F. 2004. The complete field guide to butterfies of Australia. CSIRO Publishing, Melbourne.
Clayton, M., Wombey, J.C., Mason, I.J., Chesser, R.T & Wells, A. (2006). CSIRO List of Australian Vertebrates A Reference with Conservation Status. CSIRO Publishing, Melbourne.
Common, I.F.B. Moths of Australia. Melbourne. 1990. University Press, Carlton, Melbourne.
Davey, C.C. Crowley, M.A. and Fullagar, P.J. (2007). 48th annual assessment of shearwater breeding success on Montagu Island, 27 March – 3 April 2007. Nature in Eurobodalla 21: 67-71.
Fullagar, P.J. (1989). The birds of Montagu Island, NSW. Nature in Eurobodalla 2: 27-35.
Fullagar, P. J. and Heyligers, P. C. (1998). Montagu Island shearwater population survey March 1997. M I Partners Report No. 7 (iv + 10 pp).
Fullagar, P. J., Davey, C. C., van Tets, G. F. and Heyligers, P. C. (1991). Is the Short-tailed Shearwater colonizing New South Wales? Nature in Eurobodalla 5, 51-56.
Heyligers P.C. and Adams L.G. (1989). Vascular flora of Montagu Island, NSW. Nature in Eurobodalla 2: 36-40.
Heyligers, P.C. and Adams L.G. (2004). Flora and vegetation of Montagu Island – past and present. Cunninghamia 8(3): 285-305.
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