Spatially correlated environmental factors drive synchronisation in populations of the Dalmatian Pelican

Abstract

Spatial synchrony in population dynamics has been documented recently across a range of taxa, and a number of hypotheses about the mechanisms driving spatial synchrony and the consequences of this phenomenon for the persistence of populations have emerged. Spatial environmental covariance is one of the principal factors influencing this synchrony on a large scale. However, most studies focus on population abundances, and little evidence exists on the spatial synchrony of demographic parameters. We used a 15-year dataset from two populations of a vulnerable bird species, the Dalmatian Pelican (Pelecanus crispus), to identify local and global environmental factors that cause population synchrony. We show that survival rates were temporally synchronised between the studied populations and that a large part ([50 % for both populations) of this covariation was driven by local environmental conditions. Several components of the North Atlantic Oscillation index were correlated with local climatic conditions, but not all of these components can be used as informative proxies for future variation in survival. We also present evidence that an individual's future survival can be strongly influenced by the conditions occurring during the early period of its life. Environmental factors such as water level and food availability had similar influences on breeding success and juvenile survival. Juvenile survival was lower during dry years and years of low food availability. This finding indicated that intraspecific competition may act as a limiting factor for species demography, especially in large populations. Estimating the strength of synchrony is important and should be considered in population and metapopulation analyses and in relationship to conservation measures.

Seasonal differences in energy expenditure, flight characteristics and spatial utilization of Dalmatian Pelicans Pelecanus crispus in Greece

“…, Doxa et al . 2012a). Dalmatian Pelicans start breeding at least 3 years after hatching but do not breed every year; the reasons for this and how often they do breed are unknown (Crivelli et al .…”

Differential contribution of demographic rate synchrony to population synchrony in barn swallows

“…; Doxa et al . ), but there is to our knowledge no study that included all demographic rates and population size jointly, although such an approach has been suggested repeatedly (Frederiksen, Harris & Wanless ; Grosbois et al . ).…”

“…Synchrony of single or several demographic rates is increasingly studied (e.g. Schaub, Kania & K€ oppen 2005;Grosbois et al 2009;Doxa et al 2012), but there is to our knowledge no study that included all demographic rates and population size jointly, although such an approach has been suggested repeatedly (Frederiksen, Harris & Wanless 2005;Grosbois et al 2009). Case studies are needed in order to understand better how synchrony of demographic rates translates into population synchrony.…”

Challenges for incorporating long‐term baselines into biodiversity restoration: A case study of the Dalmatian Pelican (Pelecanus crispus) in Britain

“…1998, 2000, Doxa et al . 2012b, Behrouzi‐Rada 2013). Depth of water influences foraging behaviour, and fish biomass limits colony size (Kallfa & Bino 2010).…”

“…They typically breed in colonies at inland freshwater lakes, on small islands or trampled floating 'reed islands' of dense emergent macrophytes such as Phragmites, and always in areas surrounded by water or deep mud , Doxa et al 2012a, Behrouzi-Rada 2013, Catsadorakis & Portolou 2018, Catsadorakis 2019. Colonies are also known from bare islands in coastal brackish lagoons and river deltas (Crivelli 1996, Doxa et al 2012b, Behrouzi-Rada 2013. Depth of water influences foraging behaviour, and fish biomass limits colony size (Kallfa & Bino 2010).…”