Variation in yield loss of oilseed rape due to grazing by mute swans Cygnus olor

摘要: Abstract Yield loss due to grazing by mute swans was measured on nine fields of autumn-sown oilseed rape located in five regions England. Using a paired-plot design, significant reduction yield (total dry weight seed) observed three the fields: 18%, 23% and 24%, respectively. On first these not simply fewer seeds being produced, as individual also significantly lower grazed plots, with thousand seed 13%. Between (n=9), positively correlated number per ha, days swan ha. Significant levels occurred only >5 The density ha can thus be used predict potentially provides an indicator level activity at which growers should consider deploying measures reduce grazing.