A Plague of Mice at Warren by J

July J HOBBS, Mice Plague 43 r971 who made the first general ornithological collection in the area. That man, a young fellow named George Harper, who had reached Australia from Britain about 1820 with letters of recom mendation from Sir Walter Scott, was given a grant of land at Picton, whence he appears to have ranged considerably in amas sing natural history material. In consequence, according to the Sydney Gazette of February 3, 1827, he was then able to take to Britain a great many specimens, including no fewer than 1675 bird skins, as well as two living Emus that rather alarmed Sir Walter Scott. Some of Harper's bird-skins were bought by Sir William Jardine; others were acquired by the Edinburgh Museum. It would be interesting now, 140-odd years later, to have news of those specimens. A Plague of Mice at Warren By J. N. HOBBS, Katoomba, New South Wales INTRODUCTION It is generally accepted that certain species of birds will con gregate at plagues of insects or rodents, but more detailed docu mentations of such visitations are rare. House Mice, Mus musculus were in plague proportions in many parts of the wheat belt of eastern and southern Australia in the autumn and early winter of 1970. In May 1970, I made a short visit to Warren, New South Wales, one of the areas overrun by the mice. I had been there also in December 1969, before the build-up in the numbers of mice, and, therefore, was able to mal<e a comparison of the numbers of known and probable birct"'predators of mice at the two visits. In December 1969, conditions were dry and hot but the country carried a heavy growth of dried herbage following a wet spring which had brought local flooding. Although there were scattered groups of Plague Locusts, Chortoicetes terminifera, moving through, it is doubtful if they significantly affected the numbers of bird predators present, as much larger swarms were available in near-by areas. I saw little evidence of mice being present. In May 1970, the whole district was overrun with mice. No actual counts were attempted but the scuffling of mice in the herbage was a con tinuous noise; holes were frequently as close to each other as one to every square yard; in a paddock of maize which had been sprayed from the air I saw over 100 dead mice on a 100 yards length of narrow road, and rafts of dead mice floated some 20 to 30 feet back from culverts across the irrigation channels. Seasonal conditions were not good, much of the dried vegetation of December had gone and owing to lack of rain little fresh green replacement had taken place. METHODS I was at Warren from December 15 to 18, 1969, and from May 11 to 14, 1970. On each of the four days in December I drove 44 HOBBS, Mice Plague [ Bird Watcher along four different roads leading west, north and east of Warren, stopping approximately every mile and examining the surrounding habitat on foot. Over the four days a total of 39 hours of active bird-watching took place. The same procedure was adopted in May and the same roads were followed, but owing to shorter daylight periods each road was only followed to 12 miles, and a total of 20 hours was spent in the field. Thus just under one-half of the area covered in December was retraced, and just under one half of the total December time was spent in observations and counting. All birds seen, not only potential mice predators, were counted and recorded. The totals of each species which it is considered might prey on mice are listed below. To compensate for the reduced time spent and area covered in May the actual numbers of birds counted in that month have been doubled. An asterisk appe~rs against each species which was actually seen to be feeding on mtce. DISCUSSION It is possible that some of the birds listed are either winter or summer visitors to the area. As might be expected, big increases occurred in the May count for those birds of prey known to feed extensively on mice; the Black-shouldered Kite, the Whistling Eagle, the Brown Hawk and the Nankeen Kestrel. The first named was breeding and probably some incubating birds were overlooked. The increase in the Black Kite was probably due to the mice. The count for the Square-tailed Kite was too low fo r significance to be attached to it. In my experience this species preys mostly on birds and the contents of their nests. The Brown Goshawk is often very secretive and easily over looked but the May increase is large enough to indicate a definite influx. The conclusion that this occurred because of the mice is unavoidable. The same conclusion must be drawn over the very large rise in numbers of the Little Eagle. I usually associate this bird with rabbits but few were about the district at the time. Apparently, the Little Eagle is not ashamed to stoop to such small prey as a mouse, unlike the much larger Wedge-tailed Eagle which apparently vacated the district, finding no attraction in the readily available supply of tit-bits. The Spotted Harrier is generally considered to be a summer visitor to the southern parts of its range and the count bears this out. The mice do not appear to have caused it to remain, although the numbers seen in December were very low and any that were still about in May could have been missed. This bird also prefers to hunt over tall vegetation, grass or crops. Those seen in Decem ber were watched catching locusts. The Swamp-Harrier is a bird known to vacate much of its more southern range in winter, par ticularly moving north out of Tasmania. The increase in May could either reflect this movement or be due to the increase in mice. Those falcons which prey primarily on birds, the Grey, July ] HOBBS, Mice Plague 45 1971 Black and Peregrine, did not move into the district after the mice. The Black Falcons seen in December were watched catching locusts by running after them on foot along a bitumen road! No observing was carried out at night so perhaps little sig nificance should be attached to the counts of the owls, although the day sightings of the Boobook showed quite a large increase. The remaining species listed all show quite large increases in numbers in May, which increases could well be related to the mice plague. The Grey Butcherbird is accepted as a partial migrant and may have been in the district as such and not attracted by the mice. I found the number of Kookaburras to increase quite sub stantially in winter along the Murray River, in southern New South Wales, and perhaps it may be a winter visitor to the Warren area too. The Raven and Little Raven are known nomads, the first more so as a juvenile, and were probably in the area because of the mice. Two Little Ravens, after picking meat out of freshwater mussels opened earlier by White-winged Choughs, flew to the top of a red gum-tree, some 60 feet above ground level. Here they engaged in idle mutual preening and pecking and scraping at the bark on a dead limb. A piece of the bark fell to the ground dis closing a mouse surprised in its lofty hideaway. One of the Little Ravens took it by the neck, thoroughly bashed it against the limb, and swallowed it. Research carried out to date on the Black-backed Magpie indicates it to be a sedentary species, neither migratory or nomadic. The substantial increase in the numbers in May possibly indicates that not all is known about this bird's movements or apparent Jack of such. COMPARATIVE COUNTS DECEMBER MAY SPECIES 1969 1970 *Black-shouldered Kite, Elanus notatus 4 32 Black Kite, Milvus migrans 6 22 Square-tailed Kite, Lophoictinia isura 1 4 *Whistling Eagle, Haliastur sphenurus 8 76 Brown Goshawk, Accipiter fasciatus 0 8 Little Eagle, Hieraaetus morphnoides 1 32 Wedge-tailed Eagle, Aquila audax 5 0 Spotted Harrier, Circus assimilis 3 0 Swamp-Harrier, Circus approximans 2 12 Grey Falcon, Falco hypoleucos 1 0 Black Falcon, Falco subniger 3 4 Peregrine Falcon, Falco peregrinus 1 0 *Brown Hawk, Falco berigora 39 114 *Nankeen Kestrel, Falco cenchroides 40 384 Barn Owl, Tyto alba 0 2 Boobook Owl, Ninox novaeseelandiae 1 10 *Laughing Kookaburra Dacelo gigas 9 56 46 BERULDSEN, Letter-winged Kite [ Bird Watcher *White-winged Chough Corcorax melanorhamphus 384 266 *Pied Butcherbird, Cracticus nigrogularis 43 114 Grey Butcherbird, Cracticus torquatus 2 30 Raven, Corvus coronoides 28 200 *Little Raven, Corvus mellori 98 260 *Black-backed Magpie, Gymnorhina tibicen 160 464 The Letter-winged Kite, Elanus scriptus. By GORDON R . BERULDSEN, Glenalta, South Australia SUMMARY The Letter-winged Kite, Elanus scriptus, is a species about which little has been written and only fragmentary details of its habits and habitats are known. Rarely does it enter settled areas and rarer still does it remain long enough to allow any study. However, one such occasion did present itself during June and July, 1970, in the settled areas of South Australia's lower north, when numbers of this species arrived and bred. The author seized the opportunity to learn something of their habits and although time was limited, much information was gained. OCCURRENCE At a meeting of The Adelaide Ornithologists Club in May, 1970, it was announced that a number of Letter-winged Kites had recently been seen at Willowie, approximately 170 miles north of Adelaide, and between Wilmington and Orroroo.

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