2.3. Nest predation experiment
For the nest predation experiment, we used artificial ground nests. Each corner of the bird survey plot contained one ground nest; hence the minimum distance between neighbouring nests was about 30 m (Fig. A.1). In total 192 artificial ground nests were exposed. The artificial nests mimicked the nests of common ground breeders in the study area, such as Willow Warbler (Phylloscopus trochilus), Common Chiffchaff (Phylloscopus collybita), Wood Warbler (Phylloscopus sibilatrix), Wren (Troglodytes troglodytes) and European Robin (Erithacus rubecula). We built a small hollow on the ground for each artificial nest under saplings, near deadwood or trunks. In each nest, one Blue-breasted Quail egg (Coturnix chinensis) was placed, which was similar in size (length is _22 mm) to the eggs of local ground breeding bird species (12–15 _ 15–20 mm; Bezzel, 1993). In addition, each artificial ground nest was baited with one white plasticine egg (15 _ 20 mm) in order to roughly determine the predator guild (see next paragraph). Bamboo sticks with red adhesive tape were placed 50 cm away from the artificial nests to mark the place for recovery at nest controls.
Nest exposition started at the beginning of May (from the 5th to the 18th of May), which is the main breeding season of the four ground breeding species mentioned (Bezzel, 1993). Nests were controlled after 4 and collected after 8 days of exposure. A nest was considered as preyed upon only if the quail egg was damaged or lost. We decided to do this, since plasticine eggs might overestimate the nest predation by attracting small mammals (Purger et al., 2012). Marks left on the eggs (mostly on plasticine eggs) were assigned to four predator guilds (mammalian or avian, small or large; Appendix A.2 in Supporting information). Missing eggs
were categorized as depredated by an unknown predator.
2.3. Nest predation experiment For the nest predation experiment, we used artificial ground nests. Each corner of the bird survey plot contained one ground nest; hence the minimum distance between neighbouring nests was about 30 m (Fig. A.1). In total 192 artificial ground nests were exposed. The artificial nests mimicked the nests of common ground breeders in the study area, such as Willow Warbler (Phylloscopus trochilus), Common Chiffchaff (Phylloscopus collybita), Wood Warbler (Phylloscopus sibilatrix), Wren (Troglodytes troglodytes) and European Robin (Erithacus rubecula). We built a small hollow on the ground for each artificial nest under saplings, near deadwood or trunks. In each nest, one Blue-breasted Quail egg (Coturnix chinensis) was placed, which was similar in size (length is _22 mm) to the eggs of local ground breeding bird species (12–15 _ 15–20 mm; Bezzel, 1993). In addition, each artificial ground nest was baited with one white plasticine egg (15 _ 20 mm) in order to roughly determine the predator guild (see next paragraph). Bamboo sticks with red adhesive tape were placed 50 cm away from the artificial nests to mark the place for recovery at nest controls.Nest exposition started at the beginning of May (from the 5th to the 18th of May), which is the main breeding season of the four ground breeding species mentioned (Bezzel, 1993). Nests were controlled after 4 and collected after 8 days of exposure. A nest was considered as preyed upon only if the quail egg was damaged or lost. We decided to do this, since plasticine eggs might overestimate the nest predation by attracting small mammals (Purger et al., 2012). Marks left on the eggs (mostly on plasticine eggs) were assigned to four predator guilds (mammalian or avian, small or large; Appendix A.2 in Supporting information). Missing eggswere categorized as depredated by an unknown predator.
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