Birds of Indian Subcontinent

Dynamics of a Local Population of the Willow Warbler Phylloscopus trochilus in Southern Finland

Publication Type:Journal Article
Year of Publication:1983
Authors:Tiainen, J
Journal:Ornis Scandinavica
Date Published:1983
ISBN Number:00305693
Keywords:Finland, Phylloscopidae, Phylloscopus, Phylloscopus trochilus, Trochilus
Abstract:A local population (22-27 pairs) of the Willow Warbler Phylloscopus trochilus L., studied in 1972-1978, was almost stable (18-20 pairs, CV = 5%) in the deciduous part of the study area, but more variable (4-7 pairs, CV = 28%) in the spruce-dominated part. The annual survival rate of the highly site-tenacious adult males was about 41%, but only 17% of the breeding females returned in the subsequent year. Adult mortality was low during the breeding season. The mean clutch size decreased after y = -0.060x + 6.51 eggs during the season (x is the day of the first egg, x = 0 on 31 May). Timing differences of the breeding season explained almost all annual differences of the mean clutch size. Nesting mortality was higher when the nestlings were 0-7 d old than during other phases of the whole nesting period, but this was due to human disturbance increasing the vulnerability of some nests to predation. No significant differences in the nesting success between years, parts of the study area, stage of the breeding season, or broods of different sizes were found. Estimated with the Mayfield method, only about 34% of the eggs laid produced fledglings, but probably more than 50% if the effect of disturbance is corrected for.
Short Title:Ornis Scandinavica
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith