A first-of-its-kind model, which provides guidance on the survival likelihood of abandoned penguin chicks in southern Africa, has been developed by researchers from Bristol Zoological Society, the Universities of Bristol, Exeter and Cape Town and The Southern African Foundation for the Conservation of Coastal Birds (SANCCOB).
Large numbers of abandoned African penguin chicks are hand-reared each year by SANCCOB before being released back into the wild as part of the African penguin ‘chick bolstering project’.
Hand-rearing chicks that are unlikely to survive naturally has the potential to significantly contribute to the conservation of threatened bird species, such as the African penguin.
Bristol Zoological Society has been working with SANCCOB since 2006 to hand-rear abandoned chicks and offer rehabilitation to chicks that have been oiled.
The new study shows that analysing the chicks’ body condition index, other structural measurements and its sex can help predict individual rehabilitation outcome and guide colony managers on when best to remove chicks for hand-rearing.
Dr Christoph Schwitzer, Bristol Zoological Society’s director of conservation, said: “We have known for a number of years that hand-rearing and releasing abandoned penguin chicks can be a very important contribution to the conservation of this species. However, it has always been difficult to decide when to classify a chick as ‘abandoned’ and when best to remove the abandoned chicks from a colony, so as to give them the best chances of survival.
“This study helps us enormously, as it provides quantitative guidance for colony managers to figure out the ideal point of time for chick removal.”
Chick abandonment is often seen if the adults start to moult before their chick fledges, meaning the adults are not waterproof anymore and are unable to feed their young.
Scarcity of prey leads to slow growth rates and can result in chicks not fledging in time. Often it is the case that abandoned chicks do not survive without intervention.
Globally the use of rehabilitation for conservation is growing, with many research papers monitoring the success of individuals post-release.
The ‘chick bolstering project’, which came up with this new model, is an important conservation action for these endangered birds, as it aims to bolster the African penguin population while methods to establish new colonies near sites of high prey abundance are developed.
Decisions of whether to and when to remove animals from the wild rarely use quantitative criteria. Where such criteria are assessed, there have been few studies to investigate their efficacy to predict rehabilitation outcomes.
Joanne Morten from the University of Bristol’s School of Biological Sciences, was lead author of the research.
She said: “Using data from over 1,400 chicks rescued over six breeding seasons, we identified clear body condition thresholds that colony managers can use to prioritise the removal of chicks.
“These thresholds also allow the rehabilitators to rapidly identify individuals in need of critical attention.”
African penguin colony managers are currently using the body condition index to guide removal. This study demonstrates its effectiveness, with only 2.3 percent of chicks admitted with a body condition index so low that there was a less than 50 percent chance of survival.
Joanne added: “The body condition thresholds identified in this study can be used to guide future management strategies, and can be rapidly incorporated. The body condition index uses mass and bill length, two measurements that are easy and quick, minimising handling stress.
“This is an extremely useful guide which, when used in conjunction with nest monitoring, can effectively identify chicks that have been abandoned. This tool could be useful, not just to the endangered African penguin, but other species where chicks can be successfully hand-reared.”
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