4. RESULTS & DISCUSSION   continued

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4.4 Prey remains   continued

4.4.1 Variety and preferences in prey species The results yielded a diverse range of prey species. In total, 25 different species were identified. These ranged in size with the smallest being the pardalote to the largest being the ibis. This begs the question of how a peregrine is capable of overpowering large birds such as the ibis, great egret, maned duck, and sulphur crested cockatoo, which all weigh at least as much as, and in some cases more than, the male peregrine falcon. It is suggested that these prey birds were probably partially consumed by the peregrine where they fell as it is considered that the peregrine would be incapable of carrying such large prey. Spine-tailed swift were also identified in prey remains. With this bird being claimed as the fastest bird in level flight, this just confirms the power of flight peregrine falcons have. In addition, the agility of the falcon is highlighted by its ability to catch such birds as the pardalote, honey-eater and robin which were identified as prey. The crimson rosella was identified as the most common prey species, and appears to represent the type and size of prey that peregrines in KNP catch. This may be due to the fact that the rosella frequently flies above the tree canopy and also generally flies in a linear direction which would assist peregrines in their attack. It is difficult to identify whether individual peregrines had a preference for any particular prey species as a wide range of species were identified throughout all the sites. It should be remembered however, that the prey remains were collected during the breeding season. This is clearly a time when feeding the young is a priority and it may be a case of the parent birds procuring whatever prey presents itself. Collection of prey remains outside the breeding season may reveal preferences in prey selection. Starling remains were identified in quite a few of the remoter sites. This is of concern in that it indicates that the starling, a non-native species, may be more widespread in KNP than is perhaps realised. Racing pigeons were identified in all but a few sites. Most of the rings collected were from Victorian racing clubs. The reason for so many rings being found in the eyries is probably due to the fact that the pigeon racing season coincides with the peregrine breeding season. After contacting some of the pigeon fanciers, it was discovered that most of the races for the Victorians run north-south. Most of the valley systems in KNP also run in this direction. It is suggested that these valley systems serve to channel the pigeons flying south resulting in them being concentrated to these valleys. This concentration of the racing pigeons may assist the peregrine in procuring them. Rabbit remains were found in two separate sites indicating that peregrines do not source birds solely. This has also been found in studies undertaken in the ACT (J Olsen, personal comments) and in Victoria (Hurley, personal comments). back to top 4.4.2 Peregrines and kestrels At one site, kestrels are nesting within 80m of the peregrines. Obviously the kestrels are tolerated by this peregrine pair. In the ACT, kestrel has been found in prey remains indicating that some peregrines do not tolerate their presence (Per com. J Olsen). back to top 4.4.3 Male/female prey prefences It was expected that by collecting prey remains early in the breeding season and then again later in the season, when the young were over 14 days old, that some difference in prey types selected may be identified. This was of interest in terms of prey selection of the male peregrine compared to the female. The male generally is the sole provider of food early in the breeding cycle whilst the female is incubating eggs, and later in the breeding cycle both the male and female hunt. Insufficient data has been collected so far to firmly identify any differences. However there are some indications from the 1996 and 1997 data which show prey species such as maned duck, pigeon, galah and sulphur-crested cockatoo being sourced early in the breeding season whilst eggs were being incubated. This seems to suggest that the male is also capable of taking larger birds. This is of particular interest given that the male peregrine is smaller in size to the female. back to top 4.4.4 Pesticide threats to the peregrine Of the 24 species of birds identified in this study, only three species were identified which could pose some pesticide threat to the peregrine falcon. These were: the pied currawong which locally migrate to agricultural and township areas during winter, returning to the mountains in summer; the racing pigeon which are treated by fanciers with pesticides for parasites such as lice; the spine-tailed swift which migrates from Asia each year feeding on insects as it travels south. The extent of threat from the spine-tailed swift is uncertain due to lack of information about chemicals used in agriculture in the countries travelled through by the swift whilst migrating. Whilst the number of species is relatively few, either the pied currawong or pigeon, or both, were identified as prey in approximately two thirds of the sites from which remains were collected. This, and the fact that such prey were identified at the same sites on a number of separate occasions, show that they should be considered common prey for the peregrine, at least during the breeding season. The peregrine falcon in KNP may be exposed to potentially contaminated prey, however the actual impact on breeding success is unclear. As this study has only been undertaken for four years, there is insufficient data to identify any trends in exposure to potentially contaminated prey and breeding success. Continued monitoring needs to be undertaken. This should include testing of egg shell thickness as egg shell thinning is a typical effect of high pesticide accumulation in the parent bird. Whilst this study has looked at species which migrate into the peregrines' home range, research would need to be undertaken into the movement of the falcon outside the breeding season to determine whether they migrate locally to agricultural areas. back to top