Individual study: Effects of supplementary spring feeding on willow tit Parus montanus and crested tit P. cristatus breeding success in coniferous forest east of Göteborg, Västergötland, Sweden
von Brömssen A. & Jansson C. (1980) Effects of food addition to willow tit Parus montanus and crested tit P. cristatus at the time of breeding. Ornis Scandinavica, 11, 173-178
This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.
Provide supplementary food for songbirds to increase reproductive success
A controlled trial in coniferous forest in southwest Sweden in 1976-7 (von Brömssen & Jansson 1980), found that willow tits Parus montanus and crested tits P. cristatus in a 1.8 km2 area provided with supplementary food started laying eggs significantly earlier than individuals in a 5.5 km2 control (non-supplemented) area (willow tits: average of 2-5 days earlier, 44 pairs tested; crested tits: average 5-8 days earlier, 38 tested). There was no corresponding difference in 1978, when no food was provided. Twelve-day old crested tit nestlings were significantly heavier in the fed area (average of 12.2 g for fed area vs. 11.5 g for control, number of chicks not provided) but there was no difference in willow tit nestlings (average of 10.6 g for fed area vs. 10.7 for control, number of chicks not provided). Clutch sizes did not differ between areas for either species (willow tits: average of 8.1-8.2 eggs/clutch for fed area vs. 7.7-8.2 for controls; crested tits: average of 5.3-5.4 eggs/clutch for fed area vs. 5.0-5.2 for controls). Food was provided at feeding stations located in the approximate centre of each fed territory and contained one feeder of sunflower seeds and three coconut shells containing a mixture of tallow, soy protein, wheat germ, sun-flower seeds, vitamins and minerals. In 1976 feeding started on 20th February and in 1977 on the 20-24th March, in both years it continued until all females had started laying and resumed for the first half of June (when second clutches could be expected to be laid).