Movement and foraging ecology of partially migrant birds in a changing world

Gilbert, Nathalie (2015) Movement and foraging ecology of partially migrant birds in a changing world. Doctoral thesis, University of East Anglia.

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Globally, migratory behaviour is changing in response to climatic and anthropogenic change. In recent decades, previously wholly migratory species started forming resident populations in the breeding area. Partially migratory species with resident and migratory individuals in the same population provide an opportunity to understand the causes and consequences of changing migratory behaviour. This study focuses on the influence of climate and food availability in determining movement and behaviour patterns of birds in populations that have recently become resident.
The white stork Ciconia ciconia recently established a resident population in Iberia, likely facilitated by the availability of abundant anthropogenic food resources including landfill and the invasive red swamp crayfish Procambarus clarkii. Movement data from individual white storks fitted with GPS data loggers showed that year-round nest use by resident individuals dictates many aspects of foraging behaviour, including frequency of landfill use and foraging range. Storks visited landfill from nests further away than previously expected (~48 km). High productivity near landfills has likely influenced the rapid population increase observed in recent decades, however breeding success in colonies far from landfill, particularly those located near rice fields, is low. This suggest that the imminent closure of landfills, due to EU directives, will have significant impact on white stork numbers.
Many species are still too small to be tracked with GPS tags, so stable isotopes can be used to identify breeding and wintering quarters of migratory birds. Stable isotopes were used to separate residents from migrants in a partially migratory population of lesser kestrels Falco naumanni. Carbon isotopic composition of feather samples indicated that birds completing their moult in Africa could be identified. However, resident birds could not be separated from birds that moulted in Iberia prior to migration. This emphasises the need to understand moult timing and sequence to correctly interpret stable isotope data.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Environmental Sciences
Depositing User: Stacey Armes
Date Deposited: 29 Jun 2016 11:26
Last Modified: 31 Oct 2016 03:34

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