The involvement of ethylene in the coiled sprout disorder of potato

Application of low concentrations of ethylene gas to the sprouts of Arran Pilot elicited many of the morphological and anatomical symptoms of the coiled sprout disorder. Similar effects were observed using 2-chloroethyl-phosphonic acid (Ethrel). Obstruction of coil-prone etiolated sprouts led to enhanced ethylene production for a period of two to three days but this pattern was not shown by non-coil-prone sprouts.     

The song of the Seychelles Warbler Acrocephalus sechellensis, an island endemic

The Seychelles Warbler Acrocephalus sechellensis is a resident, cooperative breeder in a saturated, island environment, whose song structure diners significantly from European marshland Acrocephalus species. The song is transmitted within a more restricted frequency range, that which propagates most effectively through tropical forest. The Seychelles Warbler has developed a relatively short, simple song, used for territorial defence throughout the year, which is readily elicited by playback. Yet it also has a complex repertoire of song types, and song activity peaks before and declines during breeding, suggesting a sexual function. The demands of tropical island life are thus reflected in both the structure and function of song in the Seychelles Warbler.     

Sexual Differences in the Responses of Captive Great Reed Warblers (Acrocephalus arundinaceus) to Variation in Song Structure and Repertoire Size

The function and evolution of repertoires in songbirds is still not clearly understood. This study involves the great reed warbler Acrocephalus arundinaceus and playback of recorded song to both captive males and females under controlled laboratory conditions. Females were implanted with oestradiol and the copulation solicitation display used as an index of sexual response. Males were not implanted and crest-raising used as an index of aggressive response. Two types of songs were used (short and long) and two sizes of repertoire (high and low). Females only responded to long songs, and responded significantly more to high than low repertoires. It was concluded that long songs have a sexual function and that high repertoires are the result of intersexual selection through female choice. Males responded to short and long songs, but did not discriminate between high and low repertoires. Adding a live male to the experiment made no difference to female responses but males responded significantly more. When field studies are also taken into consideration the overall conclusion is that song quality and repertoire size is particularly important in female choice, and that short songs and a male presence are more important in aggressive behaviour. Integration of both field and laboratory studies on males and females should lead to more rigorous testing of hypotheses concerning the function and evolution of bird songs.