Abstract
Determining which demographic and ecological parameters contribute to variation in population growth rate is crucial to understanding the dynamics of declining populations. This
study aimed to evaluate the magnitude and mechanisms of an apparent major decline in an
Atlantic Puffin Fratercula arctica population. 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. 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. Using a population model, we assessed
whether estimated variation in adult survival and reproductive success was sufficient to
explain the population change observed. Estimates of Atlantic Puffin population size
decreased considerably during the study period, approximately halving, whereas Great
Skua population estimates increased, approximately trebling. 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. A population model combining best
possible demographic parameter estimates predicted rapid population growth, at odds with
the long-term decrease observed. To simulate the observed decrease, population models
had to incorporate low immature survival, high immature emigration, or increasingly high
adult non-breeding rates. We concluded that reduced recruitment of immatures into the
breeding population was the most likely cause of population decrease. 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.
study aimed to evaluate the magnitude and mechanisms of an apparent major decline in an
Atlantic Puffin Fratercula arctica population. 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. 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. Using a population model, we assessed
whether estimated variation in adult survival and reproductive success was sufficient to
explain the population change observed. Estimates of Atlantic Puffin population size
decreased considerably during the study period, approximately halving, whereas Great
Skua population estimates increased, approximately trebling. 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. A population model combining best
possible demographic parameter estimates predicted rapid population growth, at odds with
the long-term decrease observed. To simulate the observed decrease, population models
had to incorporate low immature survival, high immature emigration, or increasingly high
adult non-breeding rates. We concluded that reduced recruitment of immatures into the
breeding population was the most likely cause of population decrease. 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.
| Original language | English |
|---|---|
| Article number | doi.org/10.1371/journal.pone.0131527 |
| Journal | PLoS One |
| DOIs | |
| Publication status | Published - 15 Jul 2015 |
