@phdthesis{Wild2020, type = {Master Thesis}, author = {Clara Mila Wild}, title = {Quantification of the ecosystem function pest control: assessing predation rates of artificial caterpillars by birds in secondary forest fragments within a peri-urban area in southeastern Brazil}, url = {https://nbn-resolving.org/urn:nbn:de:hbz:832-epub4-15866}, year = {2020}, abstract = {Urbanization processes are one of the main factors for habitat loss and fragmentation, driving global biodiversity loss and species extinction. The neotropical Atlantic forest in Brazil is considered a global key biodiversity hotspot and used to be one of the most extensive forests of the Americas. Due to substantial deforestation over centuries, its landscape was transformed into a mosaic of small forest fragments surrounded by a predominantly agricultural matrix. Urban expansion and rural urbanization have created peri-urban zones, which still can harbor natural habitat remnants, contributing to biological diversity and thus providing essential ecosystem services to urban and rural areas. The maintenance of such ecosystem services requires an understanding of the ecological processes in the ecosystem. A prerequisite for such an in-depth insight is the quantification of the underlying ecosystem functions. The ecosystem function pest control, a trophic interaction between insectivorous birds and herbivorous arthropods, was quantified in an empirical study using artificial caterpillars as prey models. This technique allows the identification of predator groups and the assessment of their predation rates. A total of 888 plasticine caterpillars were distributed at eight sites in secondary forest fragments surrounding the university campus of the federal university of S{\~a}o Carlos (UFScar) in peri-urban Sorocaba, southeastern Brazil. In sixteen point counts, 72 insect-eating birds, belonging to 19 species, were identified as possible artificial caterpillar attackers. Local habitat variables were measured to describe the forest vegetation structure and the landscape context. The study aimed to assess which structural components of the forest fragments, together with the recorded bird community variables (abundance, richness, αdiversity), best explain the estimated predation rates by birds. The mean predation rate for birds was 8.25 ± 6.3 \% for a reference period of eight days, representing the first quantification of the ecosystem function pest control for the study area. The three treatments of caterpillar placement heights (ground, stem: 0.5 -1.0 m, leaf: 1.5 - 2.0 m) were the best and only estimator to explain bird predation rates. The little dense understory and ground vegetation might have facilitated the accessibility of artificial caterpillars, especially for carnivorous arthropods and birds. The detected contrast in their foraging and predation patterns suggests that arthropods and birds complement each other in their function of pest control. Bird predation rates were found to be negatively related to the vegetation structure. Thus, more open habitats, with less understory and low tree density, but high canopy cover and including dead trees were correlated with the highest predation rates and also exhibited more specialized forest-dependent bird species. This study confirms the importance of the maintenance of forest fragments in peri-urban areas, even if they are small, to preserve forest-associated birds, to contribute to the biological diversity on a broader scale, and to prevent the loss of ecosystem functions and services, mitigating some of the adverse effects of urbanization. Further investigation of the effect among the three treatments of caterpillar placement on the predation rates is encouraged, including comparative studies among different habitat types. For future studies, it is recommended to model the avian community variables with the vegetation structure measures to predict habitat preferences of insectivorous birds. Therefore, the sampling of more units and on a bigger scale, including over a more extended period, is necessary to improve the robustness of the results, which could provide the basis for a monetary analysis of the ecosystem service pest control by birds.}, language = {en} }