Habitat Selection and Interspecific Territoriality among the Sylviid Warblers of England and Sweden

• DOI: 10.2307/2937239
• Publication Date: 2006-04-26T14:30:17Z
• Authors: Martin L. Cody
• Keywords: Warbler; Territoriality

The first part of this paper describes the quantitative characteristics breeding habitats sylviid warbler species, chiefly Sylvia and Phylloscopus, in Yorkshire, northern England, southern Sweden. second analysis is made up factors that permit or preclude coexistence various combinations species–vegetation structure, food density, competitive regime. Vegetation structure was measured 346 territories 2 locations, including 151 Phylloscopus (P. trochilus, collybita sibilatrix), 171 (including S. communis, curruca, atricapilla, borin, nisoria undata 16 Hippolais icterina territories. From data on distribution vegetation density over height territories, discriminant function generates new canonical habitat variables U 1 are independent each other reflect correlation original variables. Now species' niche can be shown as a family "confidence ellipses" plane , both species preference interspecific overlaps easily measured, within between genera countries. As result analysis, following conclusions drawn. 3 English canopy—foraging show some segregation but more noticeably great deal overlap preferred habitat. This reflected by accuracy with which specific occupant patch predicted basis vegetation—structural patch: average 2/3 such predictions verified, 1/3 wrong. Similarly Sweden, where drops out replaced an additional sylviid, icterina, occupancy correct just (72%) time. But positions niches rearranged countries, because Sweden absent taken partially sibilatrix mostly newly added occupies England would most typical trochilus. Despite these differences, canopy warblers countries use very similar vegetational criteria selection, to based country tested from nearly successful within—country tests. Five were studied country, 4 common. Interspecific poorer than (54% occupants correctly classifiable). Four occupy minor shifts, addition Swedish structurally any warblers. Again, cross—country successful, unsuccessful (@50% ), predictions. analyses precise disposition limited number study sites range low scrub tall woodland. Pilot studies pairs species: trochilus P. collybita, atricapilla communis considerable type, strongly interactive partial complete territoriality. More detailed conducted at locations. In woodland/tall Horby, nested. leave potential field unoccupied, while borin practically all ranks highly acceptable. However, pair present despite fact least might accommodated suitable habitat, likewise curruca fails site. presence particular dominant accounts for densities combination statistical direct observation supplanting replacement through aggressive behavior confirms interactions modify qualify acceptability. woodland Hoganas interact attains high levels only marginally acceptable borin. interaction them not affected absence At Bejershamn scrubland 5 Hoylloscopus breed. display variety interaction, territoriality (borin—nisoria, communis—nisoria) subtle exclusion (borin—curruca). Here diffuse competition evident (e.g., found together even though last occur frequently occurs either separately). With increasing coexist overlapping 1— 2— 3—species combinations. 2/7 one—species combinations, 3/21 two—species 2/35 common, stable compatible. remainder precluded differential simple mitigated behavioral interactions, avoidance behavior. role song convergence maintenance formation compatible documented, further questions about evolution system identified discussed.