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Title: Breeding ecology and conservation of yellow wagtails Motacilla flava in intensive arable farmland
Author: Gilroy, James J.
ISNI:       0000 0001 3500 3672
Awarding Body: University of East Anglia
Current Institution: University of East Anglia
Date of Award: 2006
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Causes of population decline in the yellow wagtail Motacilla jlava jlavissima are currently unclear. A large proportion of Britain's yellow wagtails breed on arable farmland, and factors influencing breeding productivity in this habitat could also influence national population trends. Intensive autecological studies of an arable-breeding population in eastern England revealed a number of constraints on productivity. Breeding season length could be influenced by seasonal changes in habitat suitability. Most early nesting attempts occurred in autumn-sown cereal fields, but cereal crops were avoided once they reached their full height. Consequently, second broods or replacement broods were constrained by the availability of alternative nesting habitats. In our study region, potato crops were strongly favoured for these late broods, and yellow wagtails appeared to abandon their early territories and perform dispersal in order to locate these more suitable habitats. Field-bean crops were also preferred for nesting, but nests in beans tended to become poorly concealed following growth of the crop above them, and suffered high predation rates. As such, bean fields may represent an ecological trap for yellow wagtails. Preference for nesting close to tramlines in autumn-sown cereal fields also lead to a high predation rate. Nests away from tramlines had a high success rate, but these areas were avoided by settlers, and may represent an undervalued resource for yellow wagtails. Soil conditions strongly influenced the breeding distribution of yellow wagtails in our study region. On a landscape scale, higher abundance occurred on soil types with more organic content. At a smaller scale, territory abundance within preferred crop types was largely determined by soil penetrability. Penetrable organic-rich soils may be more productive for insect prey, though the proximate mechanism underlying this pattern remains unclear. Preferred foraging habitats during breeding included wheat and potato crops, as well as field margins including ditches and tracks. However, the availability of these habitats did not influence the condition of nestlings. Breeding productivity was largely dependent on the habitat chosen for nesting, which affects nest predation likelihood. These fmdings provide an evidence-base that can be used in the design of conservation actions for breeding yellow wagtails in arable land. Activities aimed at enhancing late season nesting habitat availability, as well as attracting breeders away from potential ecological traps, could be most fruitful.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available