Demographic parameters are influenced by a variety of ecological factors, for example resource availability, predator abundance and climatic conditions. Different demographic parameters do not all affect population growth rate equally and this variation has been examined in numerous populations of plants, reptiles, birds and mammals. Determining which demographic parameters are primarily responsible for variation in population growth rate is crucial to understanding population dynamics and underlying mechanisms. Populations increase and decrease over time according to changes in demographic parameters such as survival and reproductive success. The Joint Nature Conservation Committee and Fair Isle Bird Observatory Trust supplied guidance on study design, data collection, analyses, preparation of the manuscript and the decision to publish.Ĭompeting interests: The authors have declared that no competing interests exist. Funding was received from these two sources by Fair Isle Bird Observatory from 1986 to 2013. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are creditedĭata Availability: All data underlying the findings described in the manuscript are fully available from the Joint Nature Conservation Committee Seabird Monitoring Program data archive, accessible via and/or direct inquiry to the JNCC Seabird Monitoring Program database manager (current email address: This study was funded annually by Fair Isle Bird Observatory Trust ( with contributions from the Joint Nature Conservation Committee ( ). Received: JanuAccepted: JPublished: July 15, 2015Ĭopyright: © 2015 Miles et al. PLoS ONE 10(7):Įditor: Sébastien Descamps, Norwegian Polar Institute, NORWAY (2015) Decline in an Atlantic Puffin Population: Evaluation of Magnitude and Mechanisms. This study showed that increase in the size of a predator population does not always impact on the survival of adult prey and that reduced recruitment can be a crucial determinant of seabird population size but can easily go undetected.Ĭitation: Miles WTS, Mavor R, Riddiford NJ, Harvey PV, Riddington R, Shaw DN, et al. We concluded that reduced recruitment of immatures into the breeding population was the most likely cause of population decrease. To simulate the observed decrease, population models had to incorporate low immature survival, high immature emigration, or increasingly high adult non-breeding rates. A population model combining best possible demographic parameter estimates predicted rapid population growth, at odds with the long-term decrease observed. Estimated adult Atlantic Puffin survival remained high across all years and did not vary with Great Skua abundance however, Atlantic Puffin breeding success and quantities of fish prey brought ashore by adults both decreased substantially through the period. Estimates of Atlantic Puffin population size decreased considerably during the study period, approximately halving, whereas Great Skua population estimates increased, approximately trebling. Using a population model, we assessed whether estimated variation in adult survival and reproductive success was sufficient to explain the population change observed. Estimated demographic variation was then related to two ecological factors hypothesised to be key drivers of demographic change, namely the abundance of the main predator at the study site, the Great Skua Stercorarius skua, and Atlantic Puffin chick food supply, over the same 27-year period. This was achieved using a 27-year dataset to estimate changes in population size and in two key demographic rates: adult survival and breeding success. This study aimed to evaluate the magnitude and mechanisms of an apparent major decline in an Atlantic Puffin Fratercula arctica population. Determining which demographic and ecological parameters contribute to variation in population growth rate is crucial to understanding the dynamics of declining populations.
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