Journal of Ornithology最新文献

Annual variation in singing activity of the Song Thrush (Turdus philomelos), with comments on high postbreeding song output.

This study was carried out at the Zürichbergwald, a forest east of Zurich (47°20'N/08°30'E). The study site is a wooded hill of 350 ha between 480 to 680 m asl, characterised by a Beech Fagus silvatica forest with patches of Spruce Picea abies on 25 % of its surface. The Zürichbergwald is a popular recreational area with moderate forestry exploitation. We did not differentiate acoustic registration from singing activity, and we considered the number of singing males per km to be a measure for singing activity. Two different approaches were applied: in 6 breeding seasons (1989 and 1991 to 1995) JH counted birds at sunset on a 6.1 or 7.1 km circuit (n = 123). In 1990, the same was done by RS at dawn each morning on a zigzag track of 6.7 km (n = 46). Also in 1990, RS sampled data on the breeding biology of the species. The annual cycle of morning and evening song activity was significantly correlated (Spearman’s rank-test; p < 0.001 comparing pentads, p = 0.025 comparing half of months). Morning and evening revealed the same pattern: there was a first large peak of singing activity early in the year (earliest onset of singing 19 February 1989; latest 8 March 1993) until 5 April (phase I). A period of low song activity followed from 6 April to 15 May (phase II). The period from 16 May to (circa) 5 July was characterized by a second large peak (phase III). Each of the corresponding phases was comparable between morning and evening (Wilcoxon matching pairs; p > 0.05). The analysis of evening data reveals that phase II differed from I and from III (p = 0.05), but the last two did not differ significantly (Wilcoxon matching pairs; p > 0.05). The day with the highest song activity fell in phase I twice (maximum 6.1 singing males/km, 2 April 1995) and 5 times in phase III (maximum 6.9 singing males/km, 23 May 1994). The date females first laid was determined for 53 out of 68 nests. The first brood started 25 March, the last 25 June 1990. Only 3 broods were initiated later than 5 June. The first peak of singing activity could be correlated with the (delayed) onset of breeding, but the second started at the end of the breeding season and persisted too long to be correlated with any breeding activity such as female attraction or stimulation, mate-guarding, etc. We postulate the high post-breeding song output to have several possible functions: Song instruction by father to offspring, or territory announcement for the next season.

We analysed body mass and moult data of six passerine species along their autumn migration route from northern Europe to North Africa and derived hypothetical models of the organisation of their migration in terms of fuel store accumulation. We analysed data of 46,541 first-year birds from 34 trapping sites, sampled in a network of collaborating European and African ringing stations. After accounting for effects of time of day and size, there were marked differences between the six species examined in the change of body mass along the migration route and in the timing of moult. Garden Warblers (Sylvia borin) and Pied Flycatchers (Ficedula hypoleuca) underwent their postjuvenile moult prior to migration and increased their average body mass along the migration route. Sedge Warblers (Acrocephalus schoenobaenus) also increased body mass towards the south, but started the migration bout without further refuelling well before the Sahara and moulted mainly in the wintering grounds. Reed Warblers (Acrocephalus scircpaceus) and Whitethroats (Sylvia communis) migrated while still moulting and did not increase average body mass towards south. They accumulated the energy needed to fly over the Sahara just before it. Spotted Flycatchers (Muscicapa striata) behaved in the same way, but contrary to Reed Warblers and Whitethroats they did not accumulate much fat stores in North Africa, which might urge them to stop and fuel up regularly in the Sahara. In the course of the season average body mass of all species increased slightly, which enabled them to migrate faster. In general, average body mass of first-year birds in northern and central Europe during the migration period was comparable to that of adults during breeding.