Habitat and territory segregation within Sylviine warblers of the Flemish coastal dunes

Sylviine warblers are abundant breeding birds in the Flemish coastal dunes. Although their habitat preferences are clearly different, habitat overlap can occur. Their habitat preferences can largely be explained by the overall territory-specific vegetation structure (all components included in the discriminant analysis). The transition from woodland to scrubs and from scrubland to short grasslands explains 92% of the total variance within the species' habitat characteristics. Species of the different genera (Sylvia, Phylloscopus, Acrocephalus, Locustella) show a large amount of habitat overlap. Within the Phylloscopus and Sylvia-genus, only the Lesser Whitethroat S. curruca and the Whitethroat S. communis use the same breeding habitat. Although the other congeneric species show distinct habitat characteristics, a priori classification cannot predict territory occupancy without errors: only 78.3% of the two Phylloscopus-territories and 58.3% of the Sylvia-territories were correctly classified. This indicates a certain amount of territory settlement in non-typical habitats, where competition can occur between sister species. All possible interactions between congenerics were studied by comparing the expected (based on the total of wrong classifications in the typical habitat of the other) and the observed coexistence. The number of wrong classifications could only be explained by real coexistence in the species pair S. borin-S. curruca. Interactions between all other congeneric species pairs were asymmetrical, resulting in distinct territory occupancy with one dominant species. S. borin was always the dominant species, whereas S. communis was never dominant within the possible interactions. In general, species typical for higher vegetation were dominant (with the exception of the species pair S. atricapilla-S. borin). Direct and song aggressiveness are probably the driving forces for the observed territory segregation. Our results confirm and supplement the findings of CODY (1978), who studied similar habitat and territory segregation in Sylviine Warblers in England, Southern Sweden and Sardinia