Miles W.T.S.,University of Aberdeen |
Mavor R.,Joint Nature Conservation Committee |
Riddiford N.J.,Fair Isle Bird Observatory |
Harvey P.V.,Shetland Biological Records Center |
And 4 more authors.
PLoS ONE | Year: 2015
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. Copyright: © 2015 Miles et al.
Frederiksen M.,University of Aarhus |
Moe B.,Norwegian Institute for Nature Research |
Daunt F.,UK Center for Ecology and Hydrology |
Phillips R.A.,Natural Environment Research Council |
And 27 more authors.
Diversity and Distributions | Year: 2012
Aim An understanding of the non-breeding distribution and ecology of migratory species is necessary for successful conservation. Many seabirds spend the non-breeding season far from land, and information on their distribution during this time is very limited. The black-legged kittiwake, Rissa tridactyla, is a widespread and numerous seabird in the North Atlantic and Pacific, but breeding populations throughout the Atlantic range have declined recently. To help understand the reasons for the declines, we tracked adults from colonies throughout the Atlantic range over the non-breeding season using light-based geolocation. Location North Atlantic. Methods Geolocation data loggers were deployed on breeding kittiwakes from 19 colonies in 2008 and 2009 and retrieved in 2009 and 2010. Data from 236 loggers were processed and plotted using GIS. Size and composition of wintering populations were estimated using information on breeding population size. Results Most tracked birds spent the winter in the West Atlantic, between Newfoundland and the Mid-Atlantic Ridge, including in offshore, deep-water areas. Some birds (mainly local breeders) wintered in the North Sea and west of the British Isles. There was a large overlap in winter distributions of birds from different colonies, and colonies closer to each other showed larger overlap. We estimated that 80% of the 4.5 million adult kittiwakes in the Atlantic wintered west of the Mid-Atlantic Ridge, with only birds from Ireland and western Britain staying mainly on the European side. Main conclusions The high degree of mixing in winter of kittiwakes breeding in various parts of the Atlantic range implies that the overall population could be sensitive to potentially deteriorating environmental conditions in the West Atlantic, e.g. owing to lack of food or pollution. Our approach to estimating the size and composition of wintering populations should contribute to improved management of birds faced with such challenges. © 2011 Blackwell Publishing Ltd.
Pennington M.G.,9 Daisy Park |
Riddington R.,SpinDrift |
Miles W.T.S.,Fair Isle Bird Observatory
British Birds | Year: 2012
An exceptional arrival of Lapland Buntings Calcarius lapponicus in Britain & Ireland occurred in autumn 2010. Large numbers remained to overwinter in some areas, and there was a substantial return migration in spring 201 I.The distribution and timing of the influx is analysed. Numbers were greatest in north and west Scotland, and many central and western recording areas reported record numbers. Counts in the southeast were high but generally not record-breaking. Data from Europe are compared with the situation in Britain & Ireland.The origins and causes of the influx are explored and there is circumstantial evidence to suggest that the main drivers of the influx were an unusually good breeding season in Greenland combined with weather patterns in August and September 2010. © British Birds.
Miles W.,Fair Isle Bird Observatory
British Birds | Year: 2011
Abstract This short paper summarises all known data on the population size and trends of the St KildaWren Troglodytes troglodytes hirtensis, now included as a taxon monitored by the Rare Breeding Birds Panel. The appearance of this distinctive subspecies of Wren is discussed briefly and illustrated. © British Birds 104. June 2011.