. Bulletin of the British Ornithologists' Club. Birds. 5. Haftorn 217 Bull. 1993 113(4). Figure 1. (a) The faint and dry terr or tirre sound, which the Chiffchaff frequently utters during the interval between songs (Klaebu, 28 June 1967). (b) The corresponding sound of the Willow Warbler, a soft note, which is inaudible at a distance, just as the ChiffchafFs tirre. The two calls depicted were given by the mixed singer at Heimdal (13 July 1983) between two songs. The same call is also seen as an introduction to the mixed song in Fig. 4. Material and methods In Julv 1983, Karl G. Larsson
. Bulletin of the British Ornithologists' Club. Birds. 5. Haftorn 217 Bull. 1993 113(4). Figure 1. (a) The faint and dry terr or tirre sound, which the Chiffchaff frequently utters during the interval between songs (Klaebu, 28 June 1967). (b) The corresponding sound of the Willow Warbler, a soft note, which is inaudible at a distance, just as the ChiffchafFs tirre. The two calls depicted were given by the mixed singer at Heimdal (13 July 1983) between two songs. The same call is also seen as an introduction to the mixed song in Fig. 4. Material and methods In Julv 1983, Karl G. Larsson drew my attention to a peculiar Willow Warbler in the suburb of Heimdal (63°19'N, 10°21'E) close to Trondheim, in Sor-Trondelag province in Central Norway. According to this observer the bird sang the song of the Chiffchaff in addition to its specific song. A bird with a similar song pattern, most likely the same individual, had been observed in exactly the same locality the previous year. However, it did not return in 1984. On 17—18 July 1983 I watched the bird for several hours and tape-recorded the song. It claimed a rather small territory, comprising gardens with lawns bordered by spruce and deciduous trees. I heard Chiffchaff song in the vicinity and, some distance away, a Willow Warbler's typical song. According to Larsson, the Willow Warblers were clearly outnumbered by Chiffchaffs in this area. The bird behaved like a typical Willow Warbler and sang when either sitting in the crown of a spruce or while foraging in the bushes and trees within its territory. For long periods at a time it uttered pure Willow Warblers songs (type 1), but then, at irregular intervals, it suddenly gave forth mixed songs with either figures of both species. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original British Ornitho
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectbirds, bookyear1893
