Yellowhammer (Emberiza citrinella) ecology in an intensive pastoral dominated farming landscape

Anderson, Dawn E. (2014) Yellowhammer (Emberiza citrinella) ecology in an intensive pastoral dominated farming landscape. PhD thesis, University of Glasgow.

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Farmland birds in Europe have declined as agriculture has intensified, with granivorous specialists disproportionately affected. Despite grassland based farming being widespread, farmland bird research to date has focussed on mixed and arable farms. Yellowhammers are a red-listed species in the UK. This study investigated year round habitat requirements, diet, and movements of yellowhammers at four grassland dominated farms in Ayrshire, Scotland. Data were obtained via field surveys and trials, radio-tracking and faecal analysis. Fine scale breeding season foraging habitat requirements were studied by comparing invertebrate and vegetation communities at foraging sites with paired controls across all four farms. A small scale winter supplementary feeding trial was conducted on one farm. Breeding yellowhammers were distributed throughout the study sites; average density was low at 0.11 pairs per hectare (range 0.06 to 0.15), half the densities reported in arable and mixed regions. Yellowhammers preferentially foraged within 10m of field margins. Grassland summer foraging sites contained significantly higher invertebrate diversity and more large invertebrates than control sites. Faecal analysis revealed that adults ate significantly more cereal than nestlings, with both including more invertebrate material than observed in previous studies. Diptera, Coleoptera and Araneae were key orders, with Lepidoptera larvae additionally important for nestlings. A low proportion of cereal was found in nestling diet, suggesting that the invertebrate dominated diet provided was of high quality. In contrast to summer diet, and despite grassland being the dominant habitat, cereal dominated winter diet; grass seeds and invertebrates accounted for <1% of diet in winter. Winter yellowhammer density at each farm was positively correlated with stubble availability. Radio-tracking found yellowhammers significantly selected stubble in early winter and game managed habitat in late winter. Supplementary feeding attracted an estimated 247 to 267 yellowhammers at a site where the previous year’s winter surveys recorded only 5 birds despite holding a good breeding population. Survival rates of 1st years at the supplementary fed site appeared higher than elsewhere in the landscape, and a small increase in breeding density was observed post feeding. As winter progressed, the use of the grain provided increased, suggesting that the late winter period was the most crucial time for the birds regarding food supply. Providing supplementary food represents a cheap and easy solution that could be utilised by agri-environment schemes to tackle late winter farmland bird food shortages. Alternatively, increasing winter stubble in grassland dominated regions should provide additional biodiversity benefits associated with increased landscape heterogeneity as well as increased winter food availability. This study highlights differences in breeding density, habitat selection, movements and diet of yellowhammers on grassland farms compared to arable and mixed farm populations. Restricted winter stubble habitat limits winter food availability, and hence the likely overall size of the population able to subsist in this habitat.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: farmland, bird, ecology, conservation, yellowhammer, bunting, Emberiza citrinella,declining,pastoral, farming.
Subjects: Q Science > Q Science (General)
Q Science > QH Natural history
Q Science > QL Zoology
Colleges/Schools: College of Medical Veterinary and Life Sciences > Institute of Biodiversity Animal Health and Comparative Medicine
Supervisor's Name: Metcalfe, Prof. Neil and McCracken, Prof. Davy and Parish, Dr. Dave and MacKintosh, Dr. Jane
Date of Award: 2014
Depositing User: Ms Dawn E. Anderson
Unique ID: glathesis:2014-5356
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 16 Jul 2014 08:30
Last Modified: 07 Jul 2017 15:34

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