Audience effects are increasingly recognized as an important aspect of intraspecific communication. Yet despite the common occurrence of interspecific interactions and considerable evidence that individuals respond to the calls of heterospecifics, empirical evidence for interspecific audience effects on signalling behaviour is lacking. Here we present evidence of an interspecific audience effect on the alarm-calling behaviour of the kleptoparasitic fork-tailed drongo (Dicrurus adsimilis). When foraging solitarily, drongos regularly alarm at aerial predators, but rarely alarm at terrestrial predators. In contrast, when drongos are following terrestrially foraging pied babblers (Turdoides bicolor) for kleptoparasitic opportunities, they consistently give alarm calls to both aerial and terrestrial predators. This change occurs despite no difference in the amount of time that drongos spend foraging terrestrially. Babblers respond to drongo alarm calls by fleeing to cover, providing drongos with opportunities to steal babbler food items by occasionally giving false alarm calls. This provides an example of an interspecific audience effect on alarm-calling behaviour that may be explained by the benefits received from audience response.

In many cases of interspecific kleptoparasitism, hosts develop defensive behaviors to minimize the impact of kleptoparasites. Because vigilance and defensive behaviors are often costly, selection should favor hosts that adjust the amount of investment needed to minimize losses to kleptoparasitism. However, examples of such facultative responses are rare. Here, we investigate the response of cooperatively breeding pied babblers (Turdoides bicolor) to the drongo (Dicrurus adsimilis), an avian kleptoparasite that regularly follows pied babbler groups, often giving alarm calls to alert the group to predators but also occasionally giving false alarm calls in order to steal food items. We show that pied babbler response to drongos varies markedly according to babbler group size. In small groups, where there are few individuals available to act as sentinels, babblers sentinel less when a drongo is present and respond strongly to drongo alarm calls. However, in large groups, where there are many individuals available to participate in predator vigilance, babblers sentinel more often when a drongo is present, rarely respond to drongo alarm calls, and aggressively displace drongos, with a consequent decline in the number of successful kleptoparasitism events. This behavior represent a facultative response to a kleptoparasite according to the costs versus benefits of tolerating their presence.

Two new species of the feather mite genus Dicrurobius Mironov, 2001 are described from drongos (Passeriformes: Dicruridae) in Africa: Dicrurobius alatus sp. n. from Dicrurus atripennis Swainson, 1837 and D. cameroonensis sp. n. from Dicrurus adsimilis (Bechstein, 1794). New data on host associations and distribution of the sole formerly known species, D. monacrotrichus (Gaud, 1952), are given. A key to three Dicrurobius species known to date is presented.

Possible effects on wildlife of targets baited with an attractive odour (acetone), impregnated with deltamethrin and used to control tsetse flies (Glossina morsitans morsitans), were investigated in the Kasungu National Park, Malawi. Mammals and birds were censused simultaneously along transects in 'Miombo' woodland or 'Dambo' grassland/mixed woodland, with and without targets. Mammals were also monitored by surveys of their spoor on experimentally cleared plots (5 m in diameter) and a target relocation experiment was conducted when the targets were removed from the test transects and transferred to the controls. Significantly fewer small antelopes (e.g. common Duiker Sylvicapra grimmia) were detected in plots along transects with targets (tests) than along control transects. The presence of targets affected the frequency of occurrence of antelopes, suids and large herbivores in the experimental plots, but small carnivores, monkeys, rodents and hares were unaffected. A conclusion of the relocation experiment was that the deltamethrin-impregnated cloth was responsible for the observed effects and not the acetone. A total number of 23 species of birds meeting a criterion for their abundance in the areas surveyed were selected for detailed analyses. Lower indices in the test areas than in the controls were recorded for 15 of these 23 species in the Dambos and for 10 of 21 species in the Miombo woodland. Matched paired comparisons revealed significantly lower numbers in the test areas than in the controls in both habitats only for black-headed Oriole Oriolus larvatus, but for Grey Lourie Corythaixoides concolor, little bee-eater Merops pusillus, fork-tailed Drongo Dicrurus adsimilis and combined data on three species of sunbirds in the Dambos. The black-eyed bulbul Pycnonotus barbatus had significantly lower numbers in the tests than in the controls in Miombo woodland. The numbers of three species of dove were higher in the tests than in the controls in both habitats, significantly so for the Cape turtle dove Streptopelia capicola, and numbers of the Flappet Lark Mirafra rufocinnamomea were significantly higher in the tests than in the controls in Dambos. The results are discussed in the light of previous studies on environmental effects of tsetse control, including effects of tsetse targets on pollinators especially non-target horseflies.

Immunocytochemistry of the Pars Tuberalis of the Pituitary Gland in Some Indian Wild Birds: A Comparative Study

Owl perches of various designs are used in different parts of Tamil Nadu for rodent management. Efficacy of one such owl perch was tested in the rice fields by counting the number of live rat burrows, 30 days after erection of perches and at weekly intervals thereafter in fields with and without owl perches. The owl perch was made of wooden rod (2-3m long) with a ball of straw in the top. These were pegged at random, mostly near the bunds at the rate of 45 per ha from the booting to harvesting stages of rice crop. Ther perches helped the owls, mostly the Barn Owl. Tyto alba (Scopoli) and the Spotted Owlet, Athene brama (Temuninck) to hunt rats effectively. In fields with owl perches, there was no increase in the number of live burrows and in fields without perches, there was rapid increase in the number of live burrows. Rice yield from fields with owl perches was two times more than that from fields without perches. When owl perches were removed after a time, dramatic increase in the number of rat burrows was observed. The perches were used by the King Crow, Dicrurus adsimilis (Bechstein) during day time for perching and they hunted the flying insects.

Summary Nefdt, R.J.C. 1989. A study of some bird parties in Zambia. Ostrich suppl. 14: 27–32. An account is given of the specific and individual composition of bird parties (mixed-species flocks) associated with Brachystegial/Julbernardia woodland near Lusaka, Zambia. Of the 40 species in these flocks, the Forktailed Drongo was the most common, occurring in all the bird parties, and on average present 97% of the time in any one flock. Flocks travelled faster in more open vegetation and the routes taken were always different. Certain species tended to lead the bird parties, but their presence was not essential for the maintenance of the bird party. Some species joined parties infrequently, but once participating, remained attached throughout the observation time. It is concluded that several species, together or separately, influence the direction and speed of bird parties. They may also help bring different species together. By participating in such flocks, birds can reduce their vigilance against predato...

Summary A redescription is given of Haemoproteus dicruri from Dicrurus adsimilis in Zambia. It is suggested that H. dicruri is probably the only species occurring in Dicruridae.

SUMMARYKaryotypes of Dicrurus adsimilis, Dicrurus caerulescens, Anthus novaesselandiae rufulus and Dendrocitta vagabunda vagabunda belonging to three different families of order Passeriformes have been studied. The 2n ranged in these 4 species from 68 ± to 90 ± and Z- and W-chromosomes were identified in all except in Anthus novaesselandiae rufulus The karyotypes of D. adsimilis, D. caerulescens and D. v. vagabunda show a general resemblance whereas of A. n. rufulus has a different karyotype. Karyotypic relationship among confamilial and interfamilial species have been discussed.

Summary Skead, D. M. 1975. Drinking habits of birds in the central Transvaal bushveld. Ostrich 46:139-146. Seventy one species from 25 families are recorded drinking water with short descriptions of their drinking habits. Goldenbreasted Buntings congregated at permanent water during the dry winter season when their diet probably consisted largely of dry seeds. Analysis of Masked Weaver data shows that in the dry season their drinking peaked before noon in June, July and September, but in the afternoon in August. The significance of this is not clear. The drinking technique of the Forktailed Drongo is described, one intermediate between those of doves and most passerines.