VOL. 12 (5) MARCH 1988 LENZ: Crimson Rosella in Canberra 171 Crimson Rosellas Platycercus elegans Nesting in Buildings in Canberra The Crimson Rosella Platycercus elegans is a common suburban bird in Canberra, Sydney and parts of Melbourne (Forshaw 1981). In Canberra it is widely distributed and abundant, being recorded from 93-100% of gardens and ranking among the 10 most common species in the Canberra Garden Bird Survey (Taylor eta!. 1986, 1987). Numbers in the suburbs are lowest during the breeding season from October to December (Taylor eta!. 1986, 1987). This seasonal decline in numbers could be due to a shortage of food in late spring and early summer or of suitable nest sites in urban Canberra or both. Canberra offers an abundant and diverse food supply for the Crimson Rosella with its extensive plantings of native plants and exotics, among the latter being especially many fruit-bearing shn:;bs and trees. Good supplies of grass and herb seeds are available in parks, on sportsfields, on nature strips and along road verges (see Forshaw 1981, Immelmann 1972 and Schodde & Tidemann 1986 for details of the diet of this parrot). The Crimson Rosella is also one of the main visitors to seed-tables in gardens and on window ledges of houses, flats and offices. Crimson Rosellas, throughout their range, nest in hollows in eucalypts (living or dead) from 1 to 20 m above ground (Forshaw 1982; Frith 1984; Beruldsen 1980; Schodde & Tidemann 1986). Suitable trees are only patchily distributed in Canberra's suburbs. Even where such trees occurred naturally in the original landscape many were removed during development of an area for housing. Planted eucalypts and exotic trees are mostly too young to have hollows. In Canberra, as a rule, such trees are not attacked by subterranean termites; fungus rot alone is largely insufficient to produce hollow trunks and limbs that can be used by hole-nesting birds. The combined effects of age, decay, termites and wind are required to create the diversity of cavities characteristic of eucalypts growing in the wild. Falling branches during storms pose a threat to houses and public safety. Accordingly heavy pruning or even complete removal of such trees is steadily reducing potential nest sites within the suburbs. Elsewhere in their range, Crimson Rosellas are reported to nest in hollow stumps and fence posts (Beruldsen 1980) and rarely, even in cavities in buildings (Pizzey 1980). Observations over the past 10 years indicate that Crimson Rosellas are starting to use artificial nest sites - cavities in buildings - in Canberra. The following records are available (my own if not indicated otherwise): (1) 7 October 1977: one pair inspects a hole under the roof of a two-storey building of the CSIRO Division of Entomology in Acton. No further observations to indicate that this site was used for nesting. (2) 8 October 1977: one pair inspects a hole in the brick wall of the Mathematical Sciences building, Australian National University (ANU) in Acton. Site not checked at later dates. (3) 23 November 1985: one bird emerging at midday from a hole under the roof of a 10 m high section of the Cockroft building, ANU. The Rosella, apparently the female, flies into a nearby eucalypt, calls repeatedly. It is soon joined by the male, both birds fly off together. (4) 8 December 1986: one bird sits in a tree (c. 0900 h) near the northern corner of the A.D. Hope building, ANU; after watching its surroundings for a long time it finally flies on to the ledge of the facade brick wall , which extends only to the top of the windows, and disappears beind the wall (L.R. Miller, pers. comm.). This particular section of the brick wall and several others in the building must contain a number of entries into the wall cavities. In the 1984/85 breeding season AUSTRALIAN 172 LENZ: Crimson Rosella in Canberra BIRD WATCHER a minimum of 11 pairs of Common Starlings Stumus vulgaris were nesting behind the bricks, entering the holes in the same way the Crimson Rosella did. (5) 8 December 1986: one bird, the female, clings to a clay ventilation pipe below the roof of the community hall of the Church of Christ in Ainslie. The male sits on the high wire fence of a tennis court 3 m away and chatters continuously (1740 h). The female takes about five min., partly thrusting its head and body into the opening (inner diameter 10 em) and retreating several times, before it finally disappears inside. The male follows 3 min. later without any hesitation. On 13 December 1986 I had a brief opportunity to climb up into the roof space. About 2 m away from the ventilation pipe one young Crimson Rosella was sitting on the ceiling between some battens, calling repeatedly from the moment I had opened the manhole. The young, :.estimated to be 3 weeks old, had apparently moved away from the actual breeding site. There were no droppings, feathers or other eggs at the spot where I found the bird. Circumstances did not allow a proper inspection of the roof area. Apaff from the Crimson Rosellas, a pair each of Starlings and Common Mynas Acridotheres tristis bred there as well. Their respective nests were located well away from the entrance pipes. (6) 22 December 1986: Dr. T.E. Bellas showed me a nest site in the wall near the entrance to the ANU Staff Centre. Birds had been seen throughout the nesting season entering a hole (probably left from a former water pipe) at a height of 3.5 m. The Rosellas reached the hole either from a set of bolts attached to the wall near the entrance or flew directly to it from a cypress Cupressus sp. a few metres away. The parrots appeared to be largely unperturbed by the many people taking their lunch close by. According to Dr. Bellas the wall cavity has served as a breeding site for about five years. (7) Early in the 1986/87 breeding season a pair of Crimson Rosellas frequently inspected a clay ventilation pipe (inner diameter 10 em) in the gable of a private house in Ainslie. The owner then hung a wooden nest box on the house wall. The parrots showed great interest in the box, but were finally driven away by a pair of Starlings (B. FitzGerald, pers. comm.). These observations originate from the suburbs of Acton (ANU) and Ainslie, and most likely reflect the fact that some of my own breeding bird surveys are concentrated in these areas, rather than indicating that nesting in buildings in Canberra is restricted to these suburbs. In other parts of inner Canberra where no natural nest sites are available, the first fledged young of Crimson Rosellas appear at the same time as in areas in which eucalypts with hollows are standing. This is notable because adults with young generally stay within a fairly small area around the nest site for a number of days after their young have left the nest. On the ANU campus families can be located within the same area for up to two weeks after the young are fledged. Crimson Rosellas are usually very cautious at the nest; also their habit of leaving the nest or feeding the young only a few times a day reduces the chances of detecting the breeding sites easily. It is interesting that while Ainslie had a shortage of natural nesting opportunities, that is certainly not the case on the ANU campus. Cavities in buildings may serve not only as breeding places where natural hollows are lacking or insufficient in numbers (Ainslie), but may also offer an advantage in reducing for the Crimson Rosella competition for natural hollows with conspecifics, other species of parrots and Starlings (especially at ANU). Starlings will often drive Rosellas away from nest boxes or hollow logs hung up in garden trees or on the outside of buildings. Both species could coexist, however, where for example suitable access to the roof space of a building exists. Inside, VOL. 12 (5) MARCH 1988 LENZ: Crimson Rosella in Canberra 173 the actual nests of both species could be located in several places, thus reducing the need to fight for a nesting site (example from Church Community Hall in Ainslie). So far only a few of the many hole-nesting native Australian bini species are known to breed in cavities in buildings, e.g. Australian Kestrel JiJlco cenchroitles (Pizzey 1980), Barn Owl Tyto alba (Beruldsen 1980; Schodde & Mason 1980), Laughing Kookaburra Dacelo gigas (Pizzey 1980), Tree Martin Cecropis nigricans (Beruldsen 1980), Grey Shrike-thrush Colluricincla harmonica (Pizzey 1980; Schodde & Tidemann 1986), White-throated Treecreeper Climacteris leucophaea (Pizzey 1980) and Striated Pardalote Pardalotus striatus (Beruldsen 1980; pers. obs.). Maintenance and even increase in size of the breeding population independent from immigration of birds from the original source habitats is the characteristic of all urbanised breeding bini species (Erz 1964, 1966; Mulsow 1968; Berressem et al. 1983). The use of buildings for nesting may increase the chances of the suburban breeding population of the Crimson Rosella in Canberra to become self-sustaining. I am grateful to Prof. H. Nix (Canberra) and an anonymous referee for critical comments on the manuscript. References Berressem, K.G., Berressem, H. & Schmidt, K.-H. (1983), '\bgleich der Brutbiologie von Hohlenbrutem in innerstadtischen und stadtfernen Biotopen: J. Omitlrol. 124, 431-445. Beruldsen, G. (1980), A Field Guide to Nests and Eggs of AllstnlliQit Birds, Rigby, Adelaide. Erz, W. (1964), 'Populationsokologische Untersuchungen an der Avifauna zweier nordwestdeutscher Gross-stadte', Z. wiss. Zool. 170, 1-ill. -- (1966), 'Ecological principles in the urbanization of birds', Ostrich SlqJp.
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