International Journal of Molecular Zoology 2024, Vol.14, No.2, 97-110 http://animalscipublisher.com/index.php/ijmz 103 The ability to disperse and colonize new habitats is also influenced by species-specific traits and landscape structure. A study on the demographic responses of birds to forest fragmentation found that ground- or open-nesters and species with specific nesting requirements are more vulnerable to fragmentation due to their limited dispersal abilities (Sodhi, 2009). Additionally, the presence of secondary growth habitats adjacent to fragments can facilitate movement and colonization, as observed in Amazonian mixed-species flocks, where adjacent second growth served as immigration corridors, mitigating some negative effects of isolation (Rutt et al., 2020). 5.3 Inter-species interactions Habitat fragmentation can alter inter-species interactions, affecting community dynamics and ecosystem functions. Fragmentation often leads to changes in species composition and abundance, which can disrupt established interactions such as predation, competition, and mutualism. For instance, a study on Amazonian mixed-species flocks found that fragmentation led to the collapse of these complex social networks, with significant reductions in species richness and attendance, and altered space use patterns (Rutt et al., 2020). Such disruptions can have cascading effects on ecosystem processes, including seed dispersal and insect herbivore control, particularly in tropical regions where these interactions are more pronounced (Bregman et al., 2014). Furthermore, fragmentation can exacerbate inter-species competition and predation pressures. A review of the consequences of forest fragmentation for bird populations highlighted that reduced fragment size and increased edge effects can lead to higher predation rates and competition from edge-dwelling species, further stressing already vulnerable populations (Lampila et al., 2005). These changes in inter-species interactions can ultimately influence the survival and reproductive success of bird species, contributing to population declines and local extinctions in fragmented landscapes (Korfanta et al., 2012). Therefore, understanding and mitigating the impacts of fragmentation on inter-species interactions is crucial for the conservation of bird communities and the maintenance of ecosystem functions. 6 Mechanisms of Extinction in Fragmented Habitats 6.1 Increased predation and competition Habitat fragmentation often leads to increased predation and competition among bird species. The creation of forest edges, where forests abut non-forested habitats, results in harsher microclimates and greater penetration of generalist predators such as crows and magpies, which are more common in disturbed areas. This phenomenon, known as the 'negative edge effect', elevates predation rates on smaller vertebrate species, including birds (Sodhi, 2009). For instance, studies have shown that nest predation rates are significantly higher in fragmented landscapes, with predators like raccoons, snakes, and flying squirrels contributing to the increased predation pressure (Hoover, 2006). This elevated predation can severely impact bird populations by reducing the number of successful nests and, consequently, the number of fledglings. Morgan et al. (2022) studied the relationship between forest structure and predator control variables with the abundance of native birds, nectarivores, and insectivores. The study found that in areas with high predator control intensity, the abundance of native birds, nectarivores, and insectivores significantly decreased, indicating that increased predation pressure is a major factor leading to the reduction of these bird populations. Additionally, the abundance of nectarivores and insectivores was positively correlated with native forest cover and negatively correlated with exotic forest cover, further demonstrating the importance of competitive pressure in fragmented habitats (Figure 3). The research emphasizes the necessity of considering predation and competition factors in forest management and conservation strategies to effectively mitigate the negative impacts of habitat fragmentation on bird diversity. Moreover, the loss of large-sized predators in fragmented habitats can lead to a process called 'meso-predator release', where smaller omnivorous species become more abundant and further elevate predation rates on smaller vertebrates (Sodhi, 2009). This increased competition for resources and space can exacerbate the negative impacts on bird populations. For example, in fragmented bottomland forests, the presence of raccoons and other predators has been shown to significantly reduce the reproductive success of bird species like the prothonotary warbler
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