Australian Swiftlet Aerodramus terraereginae Description: The only swift known to breed on mainland Australia. The white to pale grey rump distinguishes this species from vagrant Uniform and Glossy Swiftlets that occasionally reach mainland Australia. The wingspan being more than twice the length of the bird, and the practice of never folding the wings in against the body in flight, separates this bird from swallows and martins, whose wingspan is less than twice the body length.. Swiftlets do not perch on top of objects other than their nests, but hang below or at the side of their roost. When roosting their wings project beyond the end of the tail but the tails of roosting swallows and martins, project well beyond their folded wings. In flight the swiftlets wings may be held at right angles to the body in which instance they appear quite broad, but when held back in the typical sickle-shape of swifts they are narrower and reduce drag. The tail displays a shallow fork when folded but can look square-ended when half open, or rounded when fully spread – particularly when manouevreing to catch prey or make sharp turns in caves. Males and females are similar but juveniles have a fine pale edging to their primary feathers that distinguishes them from adults, either of which might be brooding an egg in a breeding colony. Aerodramus t. terraereginae Aerodramus t. chillagoensis Mean ± SD (mm) Range (mm) N Mean ± SD (mm) Range (mm) N Wing:flat & straight 110.6 ± 3.2 102 - 117 75 107.0 ± 2.7 99 - 116 516 Outer Rectrix 51.0 ± 2.0 46 - 54 42 47.6 ± 2.1 41 - 56 119 Central Rectrix 41.9 ± 2.4 38 - 49 43 44.0 ± 5.3 40 - 53 6 Tail 52.7 ± 1.6 49 - 55 31 46.9 ± 2.0 43 - 51 13 Length 109.9 ± 4.8 101 - 118 29 103.3 ± 4.6 94 - 112 173 Wing Span 246.3 ± 8.8 232 - 260 15 249.9 ± 5.1 238 - 262 122 Tarsus 10.1 ± 0.8 8.2 – 12.1 45 9.6 ± 0.5 9 - 11 56 Mid-Toe 5.5 ± 0.6 4.2 – 7.1 43 5.5 ± 0.4 5 – 6.2 6 Claw 4.1 ± 0.3 3.5 – 5.2 43 4.1 ± 0.3 3.7 – 4.4 6 Culmen 7.4 ± 0.7 6.2 – 9.2 37 6.9 ± 0.5 6.4 – 7.5 6 Exposed Culmen 4.4 ± 0.5 2.4 – 5.3 37 4.3 ± 0.4 3.7 – 4.8 14 Weight (g) 10.9 ± 0.9 8.5 - 13 47 9.4 ± 0.7 7.7 – 12.1 598 The majority of these measurements were taken by M.K. Tarburton from live birds and all the skins in Australian museums. 49 A. t. chillagoensis measurements were provided by the Australian Bird and Bat Banding scheme. Distribution: A.t. terraereginae is usually seen within the cream-shaded area of the accompanying figure, while A.t. chillagoensis is moderately common in the light green area (Tarburton 2013). Observations have also been made on these Continental Islands: Fitzroy (Warham 1962), Dunk (Banfield 1911), Timana (Thorpe), Bedarra (Richards), Goold (Campbell & Barnard 1917), & Hinchinbrook (Storr 1984a). On Magnetic Island they are occasionally observed during summer (Wieneke 1988). The vagrants seen at Weipa and Cape York are from the New Atlas of Australian Birds (Barret et al 2003). Vagrants have also been recorded from near Brisbane and in northern N.S.W. Habitat: Feeding habitat is air-space over rainforest, sclerophyll forest, savanna, & plantations. Breeding & sleeping habitat as under breeding behaviour. Breeding Behaviour: Clutch: 1 invariably (Storr 1984) 2? (Mathews 1918). 20 nests with single egg (Banfield 1911). The coastal A.t. terraereginae builds its nest in moderately dark situations to the underside of suspended granite boulders, in creek beds or above coastal shores, one to three metres from the ground. Sometimes it uses abandoned mine sites (Cassels 1961, Smyth et al 1980). Nests number between one and 600 in each colony (Griffin 1968, Smyth et al 1980). Nests may be built of moss (Griffin 1968), Casuarina leaves, Kangaroo Grass, vines, feathers, egg shells, Eucalyptus leaves, vines, twigs, or mixtures of these components held together and to the rock face by the glue in the birds saliva (Smyth et al 1980, Crouther 1983). The inland form A.t. chillagoensis builds its nest in totally dark situations well inside limestone caves, where nest numbers may also range from one to 600 in a colony. The nests are built of Kangraoo Grass, Black Spear Grass and saliva, and are attached to smooth overhanging surfaces from two to 30m above the cave floor. This location makes it impossible for Childrens Pythons and Brown Tree Snakes to reach most of the nests. I have watched both species fall from the rock in an effort to reach swiftlet nests. This rock houses the Lower Dooloomai colony of Australian swiftlets. Photos: Copyright M. K. Tarburton. Aerodramus t. chillagoensis builds its nests in genuine totally dark limestone caves not just overhangs. This colony is in Bottle Cave 2011, Photo Copyright M. K. Tarburton Nesting in caves has its theoretical advantages for swiftlets just as nesting in tree hollows has for birds in general. These include lower predation rates (e.g. Tarburton 2009) and lower losses due to high winds. But do these advantages always convert into reality? It is possible that the clustered nature of their nesting activities may make at least some populations of swifts vulnerable to local weather events that could lead to local extinction. The Australian Swiftlet, like all swiftlets studied to date, has a slow reproductive rate (e.g. clutch of two once a year compared to clutch of 4 twice a year for Welcome Swallows Hirundo neoxena), long incubation period (27 days compared to 16 for Welcome Swallows), and long fledgling period for its size (46-51 days compared to 19 days for Welcome Swallows) (Tarburton 1988b, 1993b). This means replacement of losses due to catastrophic events is slow compared with most passerines. The two eggs they lay each year will only be increased to three if one of the first two eggs or young nestlings is lost (Tarburton 1988b). The advantage of slow development in the egg and nestling stage is that the young can successfully go without food for 2-3 days during a cyclone or some other disruption. This is well beyond the starvation endurance of passerine birds of similar size. The disadvantage of slow development in the short breeding season presented by the Australian climate is that they cannot raise two broods in the one year. I first learnt of this problem after I had determined that their close relative, the White-rumped Swiftlet in Fiji laid two eggs, but only a single egg was ever found in Australian nests. This phenomenon is the opposite to what we would expect, because the harsher dry season of Australia should require the birds to lay more eggs not less than their island counterparts. Research was started in Queensland to determine if the published clutch size of one was correct. To everyones surprise it was found that while Qld birds (both sub-species) initially lay only one egg, on average of 32 days later the parents present the first nestling with a second egg, which it accomodatingly incubates for its parents while they spend all their daylight hours catching food for the first nestling. The second egg was always found to hatch after the elder sibling fledged and the parents just kept on feeding the younger sibling. This trick saves the parents three weeks and allows them to raise two progeny in a “normal” or even a dry season. This sibling incubation was the first new method of incubation to be discovered in 150 years (Tarburton & Minot 1987). Although researchers studying other birds breeding under climate stress, thought they might find this phenomenon, the Australian Swiftlet is still the only bird in the world known to employ sibling incubation. Experiments demonstrated that Australian Swiftlets cannot raise two nestings simultaneously. There are not enough flying invertebrates for them to do so (Tarburton 1993b). When colonies are small compared to the area of suitable & available rock surface; nests are spaced out. When space is at an optimum, nests are built against or even onto neighbouring nests. Breeding Colonies: This is what the Lower Dooloomai Colony looked like before it was decimated by a land-based predator. Photo copyright M.K. Tarburton Number of known Breeding Name of Colonies # of Active Census Date # of Birds at Census Date Colonies in Breeding Nests at Last Count Last Count Districts. (Tarburton 2013). _____ A.t. terraereginae: Broken River (4). Dip Creek Cave 1 2.9.1988. 2 Geologists Find 40 ?.4.1988 80 Millenium Cave large # 2000-2001. Trippers Delight 30 2.7.2010. 60 Cairns – Cooktown (7). Russell River Cave – Cairns district 12 ?.1.1993. 24 Red Peak – Cairns distr. 50 ?.?.1978. 100 Thornton Peak – Cairns district ? Jampee Cave, Mt Bartle Frere 20 ?.3.1997. 40 Cave B, - Cooktown district P ? Family Islands (5). Bedarra (Richards) Isl. 167 ?.?.1980. “ “ 0 ?.1.2007. 0 Dunk Isl. 173 9.9.1989. 246 Timana Isl. (Thorpe) small #. 1948. Wheeler (Toolgbar) Isl. 500 27.12.1977. 1,000 Innisfail (4). Downey Creek Falls 250 1990. 500 N. Johnston River P ?.10.1995. Golden Crown Mine Shaft 1 5.3.1960. 2 The Twins Mine, 3 ?.12.1977. 6 Mackay (2). Above Dooloomai Falls 168 24.11.2011 50 9.2.2015 Below Dooloomai Falls 160 24.11.2011 48 9.2.2015 Tully (4).