December ] PESCOTT: Tree Martins as Cave Nesters 273 1978

Tree Martins as Cave Nesters The Otway Range is a sandstone massif which extends from Anglesea in the east to Port Campbell in Western Victoria; it is flanked its northern face with broad basalt plains of the Wes­ tern District and on the south by Bass Strait. The range rises steeply from the shore to an average elevation of 600m at distance ten km inland, then falls rather more gradu­ ally to the plains. The whole area is subjected to heavy rainfall, rising from 800mm at the eastern end to over 2000mm on the ridge above Apollo Bay (Weeaproinah); as a result the inland (northern ) flank is drained by two major river systems, the Barwon which flows east to Geelong and the Gellibrand which flows to Bass Strait west of Cape Otway. On the seaward face are a number of short rivers which run from the ridge to the sea; swiftly-flowing rivers which have cut through the softer surface layers of sandstone to the hard lower horizons below, creating in the process deep valleys across which are hard rock bars forming waterfalls and cascades.

" Cave", the huge overhang on the Sheoak River, Otway Ranges, Victoria. Plate 51 Photo by Trevor Pescott. 274 PESCOTT [ Watcher

One such river is the Sheoak; the Great Ocean Road crosses it some five km west of Lome, and although a deep and scenic gorge, and part of the Lome Forest Park, it is not served with mGre facilities than a roadside car park and a basic walking path. A short distance upstream is a site described on tourist maps as "Swallow Cave" - which in reality is a wind-eroded overhang cavern beside a long cascade waterfall; the latter has been formed by water cutting through the softer sediments to hard b~d-rock, the cave being created subsequently by wind and occasional ex­ treme floods under-cutting the cliff. Swallow Cave is crescent-shaped, some 30 m-:: tres long, 10 metres deep and with a concave ceiling ab:mt six metres high. The ceiling itself is honeycomb::d with a complex pattern of pits, holes and ledges, and it is here that a large number of "swal­ lows" of unspecified regularly nest. In January 1976, I visited the cave and found it to be the nest site of large numbers of Tree Martins nigricans; it was difficult to accurately count the number of nesting becau:;e the nests were built into the complex ceiling structure, such that one entrance led into a number of inner chambers. However, my estimate at the time was that at least 50 pairs of Tree Martins were in occupation - an estimate which has been confirmed as conservative by subsequent visits. The birds have modified many of the hollows by partly closing them with mud placed very roughly on to the rock surface: there wr,s no ev:dence of the neat finish adopted by other mud nesters, suggesting that the extensive use of such material is not widely practiced by the species, although, some plant fibre including grass stems was incorporated into the mud, and in many cases the amount of mud used to partially seal the opening of the hollow would have been more than that used by a neoxena in its nest. · According to Graeme Chapman (entry p. 340, Readers' Digest Complete Book of Australian Birds, 1976), Tree Martins will use mud to reduce the size of the hollow opening in tree-nest sites. Mr. A. R. McEvey (pers. comm.) had visited the site on Jan­ uary 13, 1974, and although he had observed the birds entering the ceiling recesses, he had not seen them carrying any material into the holes. M. Hodges ( 1960) recorded the same species nesting beneath a pier deck at Swansea, Tasmania, while Serventy & Whittell ( 1951) record Tree Martins as nesting in buildings in Perth and under wooden shelters and verandahs. On a subsequent visit to the Sheoak River, I have found two pairs of Tree Martins nesting in recesses in the concrete bridge where the Great Ocean Road crosses it on the shoreline. Hamilton-Smith ( 1965) in a summary of bird species known to inhabit caves in , does not mention the Tree Martin. The practice of this species in nesting in the overhangs on the Sheoak River, and under the concrete bridge in recesses, is apparently quite Portion of the ceiling of "SwaJiow Cave" - the pale areas around the nest cavities are caused by the Tree Martins brushing off erosion products from the rock. Plate 52 Pho to hy T revor Pescott. A Tree Martin in attendance at a nest in an eroded hollow. "Swall ow Cave··. Sheoak River, Otway Ranges, Victoria. · Plate 53 Photo by T revor Pescon. 276 ALLEN: Nesting of Black Kite Bird [ Watcher

an unusual occurrence. The author would be interested to know of other cliff-overhang breeding colonies of the Tree Martin. During a visit in December, 1977, with Ken Simpson, and a Council for Adult Education natural history class (some 25 per­ sons strong) , a Laughing Kookaburra Dacelo gigas, which had been perched well off to the side of the moving mass of people, suddenly flew low over the heads of numerous people, to snatch up a fledgling Tree Martin which was on the rock surface below the nesting colony. The baby bird had not been previously noted on the ground, and perhaps was seen by the Kookaburra to fall. It would seem that the Kookaburra could be a predator on this colony of Tree Martins on a regular basis, and, considering that martin fledglings would have to fly some metres to tree cover on leaving the nests for the first time, could indeed have a major bearing on the number of young successfully leaving the area.

REFERENCES Hamilton-Smith, E., 1965. Birds in Australian Caves. Emu 65: 152-155. Hodges, M ., 1960. Nesting Sites of Tree Martins. Emu 60: 118. Readers' Digest, 1976. The Complete Book of Australian Birds. Readers' Digest Services, Sydney. Serventy, D. L. & Whitten, H. M., 1951. A Handbook of the Birds of Western Australia. Patterson, Brokensha Pty. Ltd., Perth. By Trevor Pescott, 4 Victoria Terrace, Belmont, 3216, Victoria.

Nesting of the Black Kite in North Western Victoria. During the spring of 1977, Black Kites Milvus migrans were found to be nesting some twenty five kilometres south west of Mil­ dura in an area to the south of the Adelaide Highway. Habitat comprises open wheat farms and mainly cleared grazing country with small stands of mallee eucalypts, belar and a few native pine, and remnant scrub along road edges. A most important feature of the habitat is the series of long shallow basins formed by irri­ gation water pumped and channelled from drainage lakes into de­ pressions between the parallel sand ridges. These basins attract large numbers_ of waterbirds and other species. While the whole area appears to support a fairly stable and regular breeding population of birds of prey including Little Eagle, Brown Falcon, Spotted Harrier and Nankeen Kestrel, periodic influxes occur of other species presumably from further inland. notably the Letter-winged Kite in late 1975, the Black Kite and Whistling Kite.