Abstract
Investigating habitat selection and ecological factors trade-offs is a major avian ecology topic which is closely implicated for conservation purposes. Studies dealing with the impacts of ecological factors on wintering Spoonbills are overall scarce. Here, we used Principal Component Analyses (PCA) and Generalized Linear Mixed Models (GLMM) to test the relevance of geographical, environmental and anthropogenic factors in predicting the occupancy and abundance of the Eurasian spoonbills (Platalea leucorodia) during 2008-2011 within 28 Moroccan wetlands. The Eurasian Spoonbill mean annual occurrence was 59.2% (± 1.5% SE; 95%CI: 56.3%-62.1%). Among the occupied wetlands, 15 (83.3%) were regularly occupied. We found that the Eurasian spoonbill occurrence was negatively related to distance to coastline, altitude and human presence, whereas its abundance increased significantly with increasing mudflat areas. These findings highlight the significant effect of human presence in selecting wintering sites, but not in the prediction of abundance. Management strategies should therefore address specific attributes of coastal wetlands and should carefully consider the effects of habitat use especially those related to mudflats. We further suggest guidelines for future studies to understand the dynamic of Eurasian spoonbills wintering in the region.
Highlights
When choosing a site at which to settle, individual waterbirds need to simultaneously consider the quality of available sites in terms of their environmental conditions, resource availability and the presence/frequency of predators and/or parasites [1, 2, 3, 4,5]
Based on two Principal Component Analyses (PCA) [one for data of occupied and unoccupied wetlands (PCAoc), and the otherone for data of occupied wetlands only (PCAabto model the abundance)], we reduced the total number of studied variables (n = 9) to a smaller number by merging different categories, while minimizing the loss of independent information
The PCA summarized these studied field variables into four independent axes accounting for 82.5 % of the variance of the original dataset [28.6 %,22.2 %(eigenvalue = 1.997), 18.2%, and 13.5% respectively].The varimax rotation revealed a first gradient (PCwetland features) characterized by high loadings of variables related to wetland features as it was positively correlated with distance to the nearest coastline (r= 0.983,p< 0.001), and altitude (r= 0.964,p< 0.001)
Summary
When choosing a site at which to settle, individual waterbirds need to simultaneously consider the quality of available sites in terms of their environmental conditions, resource availability and the presence/frequency of predators and/or parasites [1, 2, 3, 4,5] This choice can be influenced by: (i) geographical and topographical factors, which may either decrease or enhance attractiveness of a site [6, 7, 8, [9], and (ii) human activities, which are known to affect wildlife populations Wetlands are habitats of the highest conservation interest due to their high biological diversity [18, 19, 20]) They play a vital role in the life cycle of many species, both during wintering, breeding and migration of waterbirds [21]. The global population is of about 66,000-140,000 individuals [23]
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