The primary hazard for open-cup nesting birds is nest predation. Vegetation structure and coverage may affect nest predation through various mechanisms such as the ability of a predator to locate the nests, which may vary between breeding habitats. We examined the association between vegetation structure and nest predation in three different types of pine plantations using artificial nests of the Sardinian warbler, Sylvia melanocephala, which were located 30 cm above ground in low bushes. We also assessed the relationship between bird abundance and nest predation in each type of forest. Finally, we identified predators through their bite marks on 3D-printed plaster eggs that were placed in the nests. The percentage of nests predated in pine forests with high understory coverage was significantly higher than in pine forests with only sparse understory. We also found that the nest predation rate positively correlated with total bird abundance and the abundance of S. melanocephala. The species of nest predators varied between different forest types, although rodents and birds were the most and second-most abundant predators, respectively, in each forest type. These results show that patches with only sparse understory vegetation within the forests generate nesting sites for birds with less risk of predation. But because bird abundance in this habitat type was relatively low, the net effect of preserving such habitat on the number of hatched birds should be further studied.

中文翻译：

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植被结构控制三种针叶林栖息地的巢穴捕食

开杯筑巢鸟类的主要危害是巢捕食。植被结构和覆盖率可能会通过各种机制影响巢穴捕食，例如捕食者定位巢穴的能力，这可能因繁殖栖息地而异。我们使用撒丁岛莺 Sylvia melanocephala 的人工巢穴检查了三种不同类型松树种植园中植被结构与巢穴捕食之间的关联，这些巢穴位于低矮灌木丛中，距地面 30 厘米。我们还评估了每种森林中鸟类数量与巢穴捕食之间的关系。最后，我们通过放置在巢穴中的 3D 打印石膏蛋上的咬痕识别了捕食者。早在林木覆盖率高的松林中的巢穴百分比明显高于林木稀疏的松林。我们还发现，巢穴捕食率与鸟类总丰度和 S. melanocephala 的丰度呈正相关。巢穴捕食者的种类在不同的森林类型之间有所不同，尽管啮齿动物和鸟类分别是每种森林类型中数量最多和第二大的捕食者。这些结果表明，森林中只有稀疏林下植被的斑块为鸟类提供了较少捕食风险的筑巢地。但由于这种栖息地类型的鸟类数量相对较低，因此应进一步研究保护此类栖息地对孵化鸟类数量的净影响。我们还发现，巢穴捕食率与鸟类总丰度和 S. melanocephala 的丰度呈正相关。巢穴捕食者的种类在不同的森林类型之间有所不同，尽管啮齿动物和鸟类分别是每种森林类型中数量最多和第二大的捕食者。这些结果表明，森林中只有稀疏林下植被的斑块为鸟类提供了较少捕食风险的筑巢地。但由于这种栖息地类型的鸟类数量相对较低，因此应进一步研究保护此类栖息地对孵化鸟类数量的净影响。我们还发现，巢穴捕食率与鸟类总丰度和 S. melanocephala 的丰度呈正相关。巢穴捕食者的种类在不同的森林类型之间有所不同，尽管啮齿动物和鸟类分别是每种森林类型中数量最多和第二大的捕食者。这些结果表明，森林中只有稀疏林下植被的斑块为鸟类提供了较少捕食风险的筑巢地。但由于这种栖息地类型的鸟类数量相对较低，因此应进一步研究保护此类栖息地对孵化鸟类数量的净影响。在每种森林类型中。这些结果表明，森林中只有稀疏林下植被的斑块为鸟类提供了较少捕食风险的筑巢地。但由于这种栖息地类型的鸟类数量相对较低，因此应进一步研究保护此类栖息地对孵化鸟类数量的净影响。在每种森林类型中。这些结果表明，森林中只有稀疏林下植被的斑块为鸟类提供了较少捕食风险的筑巢地。但由于这种栖息地类型的鸟类数量相对较低，因此应进一步研究保护此类栖息地对孵化鸟类数量的净影响。