School of Anthropology & Conservation

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Debbie Fogell

Measuring the effects of supplementary feeding on trajectory of threatened populations

Supervisor(s): Professor Jim Groombridge (Main) and Dr John Ewen (ZSL)

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My research focuses on the provision of supplementary food (SF) in endangered species recovery programmes and how this facilitates the transmission of disease-causing pathogens between individuals reliant on SF. SF has become a widespread management tool for species recovery, often applied as a safety net whilst the limiting factors of a threatened population are addressed. However, decisions to provide SF are seldom based on sound population theory and, crucially, anticipated benefits are rarely evaluated against resulting demographic trajectory.

Yellowing of feathers and feather loss in a PBFD-affected female Echo parakeet

Yellowing of feathers and feather loss in a PBFD-affected female Echo parakeet. © Chantal McLeod-Nolan

Disease-causing pathogens have an important regulatory role within ecosystems by directly reducing species' fitness and reproductive capacity, or indirectly affecting interspecific interactions and environments. Psittacine beak and feather disease (PBFD) is the most commonly diagnosed disease in parrots. Caused by the beak and feather disease virus (BFDV, family Circoviridae), it is thought to have originated from the South Pacific with clinical signs of disease including feather dystrophy, beak and claw deformities, and immunosuppression. PBFD has been implicated in the decline of free-living parrot populations and has now been listed by the Australian government as a “Key Threatening Process” to biodiversity. BFDV is considered to demonstrate high environmental persistence owing to its ability to infect a broad range of closely-related host species and is transmissible both horizontally (through contact with contaminated feather dust, surfaces or objects), and vertically (from a female to her offspring). PBFD has been observed in the Mauritius parakeet since an outbreak in 2005 and the population prevalence of BFDV has subsequently been monitored annually.

Through my Masters research, it has been determined that the proximity to nearest SF hopper is inversely related to the prevalence of BFDV in Mauritius parakeet nestlings, where the proportion of infected individuals is higher in those broods produced closer to hoppers. Therefore, the primary aims of my PhD are to determine whether provisioning of supplementary food has a positive or negative effect on ‘vital rates’ of this endangered bird population, what the drivers are behind patterns of SF use, and to test management methods to reduce the spread of disease and promote species recovery. This will be done by:

  1. Quantifying the temporal and spatial environmental accumulation of BFDV on feeding hoppers used to provide SF to the recovering Mauritius parakeet population using molecular genetic techniques.
  2. Experimentally manipulating the biosecurity protocol currently employed by the Mauritian Wildlife Foundation at SF hoppers to assess whether both the environmental accumulation of virions and, consequently, the prevalence of BFDV in annually-produced offspring can be reduced.
  3. Determining the social contact network between individuals that regularly attend SF hoppers and relate this to demographic variables to determine 'super-spreaders' of infection within the Mauritius parakeet population.


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  • Fogell, D. J., Martin, R. O. and Groombridge J. (2016) Beak and feather disease virus in wild and captive psittacines: an analysis of geographic, taxonomic and methodological trends. Archives of Virology, 161(8), 2059-2074
  • Fogell, D. J., Tolley, K. A., & Measey, G. J. (2013). Mind the gaps: investigating the cause of the current range disjunction in the Cape Platanna, Xenopus gilli (Anura: Pipidae). PeerJ, 1, e166.
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Echo parakeets feeding from one of the pigeon hoppers in the Black River Gorges National Park

Echo parakeets feeding from one of the pigeon hoppers in the Black River Gorges National Park.

Debbie is a NERC ENVeast funded student with two CASE partners: Dr Andrew Greenwood from the International Zoo Veterinary Group (IZVG) and Dr Richard Young from Durrell. Other small awards contributing to field and laboratory expenses have been gratefully received from:

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Last Updated: 15/09/2017