International Journal of Molecular Zoology 2024, Vol.14, No.2, 97-110 http://animalscipublisher.com/index.php/ijmz 106 7.2 Case study 2: fragmentation in urban environments Urban environments present unique challenges and opportunities for bird conservation. A systematic review of the occurrence of forest Neotropical Migrant Bird Species (NMB) in small forest fragments and residential areas with urban tree canopy in Latin American countries revealed that urban and rural forest fragments and residential areas could serve as habitats for NMB during migration and winter seasons. The review identified 58 forest NMB from 19 studies, including 45 Nearctic Migrants and 12 Austral Migrants, suggesting that fragmented urban habitats can provide critical stopover and wintering sites for some interior-forest specialists (Amaya-Espinel and Hostetler, 2019). In another study, researchers investigated the value of small forest fragments and urban tree canopy for Neotropical migrant birds during winter and migration seasons. They found that 54 NMB were present in small urban/rural fragments and 30 in residential areas. This indicates that urban environments, despite their fragmented nature, can still support a variety of migrating birds. However, the study highlighted the need for more research to determine the extent to which these fragmented habitats are used by NMB during migration and winter seasons (Amaya-Espinel and Hostetler, 2019). 7.3 Case study 3: comparative analysis of island vs. mainland bird populations The effects of habitat fragmentation on bird populations can vary significantly between island and mainland environments. A study comparing bird communities on land-bridge islands and mainland forest sites in Lake Kenyir, Peninsular Malaysia, found that insectivorous birds were the most affected by fragmentation. The study used timed point counts to evaluate the effects of area, isolation, and dietary guild on species richness, abundance, and diversity. The results showed that insectivorous birds were particularly sensitive to fragmentation, followed by frugivorous and omnivorous birds. This pattern is consistent with other studies in the Neotropics, highlighting the vulnerability of insectivorous birds to habitat fragmentation (Yong et al., 2010). Another study examined the direct and indirect effects of habitat reduction on avian species loss from tropical forest fragments in Lago Guri, Venezuela. The researchers found that area reduction had a direct effect on species loss, but indirect effects, particularly those mediated through changes in herbivore abundances, were more significant. For example, species loss was slowed on islands with hyperdense howler monkeys and accelerated on islands with leaf-cutter ants but lacking howlers. These findings suggest that the loss of species from forest fragments is driven by active biotic processes, such as changes in trophic structure, rather than just a passive response to habitat reduction (Feeley and Terborgh, 2008). 8 Conservation Strategies 8.1. Habitat restoration and connectivity Habitat restoration and connectivity are critical strategies for mitigating the adverse effects of habitat fragmentation on bird populations. Restoration efforts should focus on maintaining native vegetation, deadwood, and other nesting structures within habitat fragments to support bird reproduction and survival (Marzluff and Ewing, 2001). Additionally, managing the landscape surrounding the fragments, known as the matrix, to resemble the native habitat can enhance the ecological function of these areas. This includes increasing foliage height diversity within fragments and designing buffers to reduce the penetration of undesirable agents from the matrix (Marzluff and Ewing, 2001). Furthermore, integrating urban parks into the native habitat system and anticipating urbanization to seek creative ways to increase and collectively manage native habitats are essential for long-term conservation success (Marzluff and Ewing, 2001). Improving landscape connectivity is equally important. Studies have shown that the effects of habitat fragmentation are most severe in the smallest and most isolated fragments, and these effects magnify over time (Haddad et al., 2015). Therefore, creating corridors and stepping stones that link isolated fragments can facilitate bird movement and gene flow, reducing the risk of local extinctions. For instance, small forest fragments can act as corridors and increase overall connectivity, benefiting the entire bird community (Bhakti et al., 2018). By enhancing connectivity, conservationists can help maintain ecosystem services and reduce extinction rates (Haddad et al., 2015).
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