AN INVESTIGATION INTO THE BREEDING DENSITY OF YELLOWHAMMERS (EMBERIZA CITRINELLA) IN HEDGEROWS ON THE BRACKENHURST ESTATE
by CHRISTINA TAYLOR
Abstract
In Britain, loss of habitat heterogeneity, at a range of scales, through agricultural intensification, has severely impacted on farmland biodiversity, particularly bird species. Yellowhammer population decline has been more recent and more accelerated than similar species, for reasons which are still debated. Yellowhammers specialise in breeding in hedgerows, but previous studies have failed to agree on what specific hedgerow attributes influence breeding territory selection. The aim of the study was to consider whether the Hedgerow Evaluation Grading System (HEGS) could be used as an indication of Yellowhammer habitat requirements during breeding season. Yellowhammer territory mapping, HEGS evaluations and vegetation surveys were
undertaken on the Brackenhurst Estate between June and August, 2009. The primary hypothesis, that there was a significant positive relationship between the HEGS values and breeding density of Yellowhammers, was supported. This finding implies that HEGS can give an indication as to the value of hedges for breeding Yellowhammers and is, therefore, an invaluable tool that could be utilised in both Yellowhammer and farmland
bird conservation. Secondary hypotheses were tested to consider whether any specific hedge attributes, or factors outside of the hedge boundary, significantly influenced breeding territory selection. Yellowhammers showed a strong preference for unimproved, semi-natural verges and a strong avoidance of permanent pasture in favour of cereal and mixed land use. All other preferences were weak, which was consistent with most previous studies, apart from a possible avoidance possible avoidance of grass-sown field margins which is contrary to previous studies and which way warrant further investigation.
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