Short-term dynamics and spatial pattern of nocturnal birds inhabiting a Mediterranean agricultural mosaic
Published: Volume 57(2), December 2010. Pages 303-320.
Understanding the interaction between abundance fluctuation and spatial pattern of populations is crucial for designing conservation strategies, particularly in systems such as Mediterranean agricultural mosaics subjected to intensification and weather fluctuations. We investigated the effects of a severe drought on short-term population dynamics of nocturnal birds, a threatened and declining group of species that has been little studied. We addressed three levels (i.e. species, food guild and assemblage) for three consecutive years. The highest fluctuation in abundance occurred for species which feed on invertebrates, and the lowest abundance corresponded to the year after the severe drought. Species that feed on invertebrates occupied different sites in the different season sampling periods, whereas species that feed on vertebrates tended to occur at the same sites throughout the year. At the assemblage level, species composition did not change between years. Patterns of site occurrence and population abundance in different years were mostly spatially congruent; thus, habitat features that are strictly space-dependent are more critical for explaining these patterns than other factors that change over time such as weather. The spatial segregation of little owl Athene noctua and Eurasian scops owl Otus scops is partially attributed to the sedentary character of the former and the migratory character of the latter. The low population fluctuations observed for most species make their conservation more straightforward since harsh years in relation to weather were not associated with abrupt population declines except for stone curlew Burhinus oedicnemus, a vulnerable species that should be prioritised for conservation actions.