1 Introduction

Habitat fragmentation results from various anthropogenic activities such as deforestation, urbanization, and agricultural expansion. It leads to the creation of habitat patches that are smaller and more isolated than the original habitat, disrupting ecological processes and species interactions. Fragmentation can alter the physical environment, increase edge effects, and create barriers to movement, which can have cascading effects on biodiversity and ecosystem function (Nally et al., 2000; Bregman et al., 2014; Rutt et al., 2020).

Globally, habitat fragmentation is recognized as a critical threat to biodiversity. Studies have shown that fragmentation affects species differently based on their ecological traits, such as habitat specialization, body size, and mobility (Nally et al., 2000; Bregman et al., 2014; Khimoun et al., 2016). For instance, tropical regions, which are biodiversity hotspots, are particularly vulnerable to fragmentation, leading to significant declines in bird populations and disruptions in ecological processes like seed dispersal and insect control (Korfanta et al., 2012; Bregman et al., 2014). In temperate regions, the impacts are more variable, with some species showing resilience while others decline (Ruiz‐Gutierrez et al., 2008; Bregman et al., 2014).

Understanding how habitat fragmentation affects bird behavior and extinction mechanisms is crucial for several reasons. Birds play vital roles in ecosystems as pollinators, seed dispersers, and predators of insects. Changes in their behavior and population dynamics can indicate broader ecological shifts and help identify critical areas for conservation (Korfanta et al., 2012; Amos et al., 2014; Bregman et al., 2014). Moreover, studying these effects can reveal the underlying mechanisms driving species declines and extinctions, such as reduced genetic diversity, altered species interactions, and increased mortality rates (Ruiz‐Gutierrez et al., 2008; Simberloff, 2008; Khimoun et al., 2016).

This study synthesizes existing knowledge and analyzes current research on the effects of habitat fragmentation on bird behavior and extinction mechanisms. Based on the ecological traits of birds and the specific characteristics of fragmented landscapes, it identifies how different bird species respond to fragmentation. The goal is to mitigate the negative impacts of habitat fragmentation on bird populations and enhance ecosystem resilience, providing a basis for habitat conservation strategies.

2 Theoretical Background

2.1 Concepts of habitat fragmentation

Habitat fragmentation refers to the process by which large, continuous habitats are divided into smaller, isolated patches, often due to human activities such as urban development, agriculture, and deforestation. This phenomenon results in the creation of habitat remnants surrounded by a matrix of different land uses, which can significantly alter the ecological dynamics within these patches (Sodhi et al., 2011; Mullu, 2016). Fragmentation is not merely the reduction in habitat area but also involves changes in habitat configuration, leading to increased edge effects and isolation of species populations (Didham, 2010) The matrix quality and surrounding landscape composition play crucial roles in determining the impact of fragmentation on biodiversity and ecosystem processes (Didham, 2010).

The effects of habitat fragmentation are multifaceted and context-dependent, varying with the spatial scale, time frame, and specific ecological traits of the species involved (Didham, 2010). For instance, fragmentation can lead to reduced patch size, increased edge effects, and greater isolation, all of which can negatively impact species richness and population densities (Didham, 2010). Additionally, the degree of fragmentation's impact can differ based on the type of habitat and the nature of the surrounding matrix, with some species being more resilient to fragmentation than others (Amos et al., 2014; Mullu, 2016).

2.2 Key theories on bird behavior and ecology

Bird behavior and ecology are profoundly influenced by habitat fragmentation, which can disrupt movement patterns, breeding success, and foraging behavior. One key theory is the concept of "functional connectivity", which refers to the ease with which birds can move across a fragmented landscape. Reduced connectivity can impede dispersal and gene flow, particularly for less mobile species, leading to population declines and reduced genetic diversity (Amos et al., 2014). Studies have shown that fragmentation effects are often species- and sex-specific, with some species and sexes being more affected by reduced connectivity than others (Amos et al., 2014).

Another important theory is the "edge effect", which posits that the edges of habitat fragments experience different environmental conditions compared to the interior, often leading to increased predation and parasitism rates. For example, increased nest predation and parasitism by cowbirds have been observed in more fragmented landscapes, negatively impacting the reproductive success of forest birds. Additionally, the "source-sink" dynamics theory suggests that fragmented landscapes can create population sinks, where local reproduction is insufficient to maintain the population without immigration from more intact habitats (Amos et al., 2014).

2.3 Mechanisms of extinction

Habitat fragmentation can drive species towards extinction through several mechanisms. One primary mechanism is the reduction in habitat area, which directly decreases the available resources and space for species, leading to smaller population sizes and increased vulnerability to stochastic events (Didham, 2010). Smaller, isolated populations are also more susceptible to inbreeding depression and genetic drift, which can reduce genetic diversity and adaptive potential (Amos et al., 2014).

Another mechanism is the disruption of ecological interactions, such as predation, competition, and mutualism. Fragmentation can alter food web dynamics, leading to trophic disruptions that affect resource consumption and species interactions (Martinson and Fagan, 2014). For instance, specialist herbivores are more vulnerable to fragmentation due to their reliance on specific host plants, while generalist species may be more resilient (Rossetti et al., 2017). Additionally, fragmentation can exacerbate the impacts of other environmental stressors, such as climate change and invasive species, further increasing the risk of extinction (Didham, 2010).

3 Causes of Habitat Fragmentation

3.1 Natural causes

Natural causes of habitat fragmentation include geological and climatic events that alter the landscape over time. Volcanic activity, for instance, can create isolated forest fragments, as observed in Hawaiian forests where volcanic eruptions 153 years ago led to the formation of distinct forest patches. These patches vary in size and structural features, which in turn affect the richness of native and exotic bird species. Smaller fragments tend to be dominated by native species, while larger fragments host a mix of native and exotic species, demonstrating the long-term ecological impacts of natural fragmentation events (Flaspohler et al., 2010).

Additionally, natural disturbances such as wildfires, hurricanes, and landslides can lead to habitat fragmentation. These events can create a mosaic of habitat patches with varying degrees of connectivity and quality. For example, in the western United States, natural disturbances are common in forested landscapes, and their interaction with anthropogenic fragmentation can influence bird populations differently compared to more stable regions. In these dynamic environments, natural predators and other ecological factors play a significant role in shaping bird community responses to fragmentation.

3.2 Human-induced causes

Human activities are a major driver of habitat fragmentation, often resulting in more severe and widespread impacts compared to natural causes. Deforestation for agriculture, urban development, and infrastructure projects leads to the creation of isolated habitat patches. In the Brazilian Atlantic forest, for instance, human-induced fragmentation has significantly affected bird species, with certain species showing marked declines in fragmented habitats compared to continuous forests. This highlights the need for conservation strategies that consider species-specific responses to human disturbances (Anjos et al., 2011).

Moreover, habitat fragmentation due to human activities can disrupt ecological processes and lead to population declines. In the midwestern United States, forest fragmentation has been linked to increased nest predation and parasitism, resulting in lower reproductive success for migratory birds. This suggests that fragmented landscapes may act as population sinks, relying on immigration from more intact habitats to sustain bird populations. Conservation efforts should focus on preserving large, unfragmented core areas to mitigate these negative effects (Coddington et al., 2023).

3.3 Global patterns of fragmentation

Globally, habitat fragmentation exhibits distinct patterns influenced by both natural and human-induced factors. Tropical regions, in particular, are highly sensitive to fragmentation, with significant impacts on bird species and ecosystem functions. A study spanning five continents found that tropical bird communities are more severely affected by fragmentation compared to temperate regions. Insectivores and large frugivores, for example, show a marked decline in fragmented tropical habitats, which can disrupt key ecological processes such as seed dispersal and insect herbivore control (Bregman et al., 2014).

In contrast, temperate regions may exhibit more resilience to fragmentation, with less pronounced impacts on bird community structure. However, even in these regions, fragmentation can lead to long-term demographic changes. In the Usambara Mountains of Tanzania, long-term studies have shown that fragmentation reduces survival and population growth rates for various bird species, indicating that the effects of fragmentation can persist long after the initial habitat loss. This underscores the importance of considering both immediate and long-term impacts of fragmentation in conservation planning (Korfanta et al., 2012).

4 Behavioral Changes in Birds due to Habitat Fragmentation

4.1 Altered migration patterns

Habitat fragmentation significantly impacts the migration patterns of birds. Fragmented landscapes often create barriers that disrupt traditional migratory routes, forcing birds to alter their paths. This can lead to increased energy expenditure and higher mortality rates during migration. For instance, studies have shown that birds from fragmented landscapes exhibit higher resistance to boundary-crossing and increased dispersal success compared to those from continuous habitats, suggesting that fragmentation forces birds to adapt their migratory behaviors to navigate through human-modified landscapes (Cornelius et al., 2017). Additionally, the disruption of migratory routes can lead to changes in the timing of migration, which can affect breeding success and survival rates (Lampila et al., 2005).

Moreover, the fragmentation of habitats can lead to a reduction in the availability of stopover sites, which are crucial for migratory birds to rest and refuel. This can result in longer and more strenuous migrations, further impacting the birds' overall fitness and survival. The altered migration patterns can also lead to changes in the distribution of bird populations, with some species becoming more localized and others expanding their ranges in search of suitable habitats (Bregman et al., 2014). These changes can have cascading effects on the ecosystems that these birds inhabit, as they play critical roles in processes such as seed dispersal and insect population control.

4.2 Changes in mating behaviors

Habitat fragmentation can also lead to significant changes in the mating behaviors of birds. Fragmented habitats often result in smaller, isolated populations, which can reduce the availability of mates and increase the likelihood of inbreeding. This can lead to changes in mating strategies, such as increased mate searching and altered courtship behaviors. For example, studies have shown that pairing success is closely associated with fragmentation, indicating that birds in fragmented habitats may have to invest more effort in finding and securing mates (Lampila et al., 2005).

Additionally, the reduced availability of suitable nesting sites in fragmented habitats can lead to increased competition for these sites (Figure 1), further influencing mating behaviors. Coddington et al. (2023) studied the capture rates of adult breeding birds and fledglings with different nesting strategies in primary forests, and forest fragments before and after isolation. The study found that habitat fragmentation had the greatest impact on open-cup nesting birds and the least impact on cavity-nesting birds. The research emphasizes the negative effects of forest fragmentation on bird diversity and population structure, particularly for species that rely on open nesting environments.

Furthermore, habitat fragmentation can affect the social structure of bird populations, leading to changes in mating systems. In some cases, birds may shift from monogamous to polygamous mating systems in response to the altered availability of mates and resources. This can have significant implications for reproductive success and population dynamics. For instance, increased nest predation and parasitism in fragmented habitats can reduce reproductive success, leading to changes in the timing and frequency of breeding attempts. These changes in mating behaviors can ultimately impact the genetic diversity and long-term viability of bird populations in fragmented landscapes (Khimoun et al., 2016).

4.3 Modification of feeding habits

Habitat fragmentation can lead to significant modifications in the feeding habits of birds. Fragmented habitats often result in changes in the availability and distribution of food resources, forcing birds to adapt their foraging strategies. For example, studies have shown that fragmentation can lead to a decline in the prevalence of insectivores and large frugivores, particularly in smaller habitat fragments (Bregman et al., 2014). This suggests that birds may need to shift their diets or foraging behaviors to cope with the altered availability of food resources. Additionally, the increased edge effects in fragmented habitats can lead to changes in the types of prey available, further influencing feeding habits (Rossetti et al., 2017).

Moreover, habitat fragmentation can impact the feeding efficiency of birds by increasing the time and energy required to locate and capture food. This can lead to changes in foraging behaviors, such as increased foraging range and altered foraging techniques. For instance, birds in fragmented landscapes may need to spend more time foraging in less optimal areas, which can reduce their overall feeding efficiency and impact their fitness and survival (Korfanta et al., 2012). Additionally, the changes in plant and insect communities in fragmented habitats can lead to shifts in the diet composition of birds, with potential consequences for their nutritional status and reproductive success (Coddington et al., 2023). These modifications in feeding habits can have cascading effects on the ecosystems that these birds inhabit, as they play critical roles in processes such as seed dispersal and insect population control.

5 Impact on Bird Populations

5.1 Population dynamics and genetic diversity

Habitat fragmentation significantly impacts the population dynamics and genetic diversity of bird species. Fragmentation often leads to smaller, isolated populations, which can result in reduced genetic diversity due to inbreeding and genetic drift. For instance, a study on the Worthen's sparrow (Spizella wortheni) found that despite high genetic diversity, the species' nomadic behavior might be a key factor in maintaining gene flow across fragmented landscapes, suggesting that behavioral adaptations can mitigate some negative genetic impacts of fragmentation (Canales-Delgadillo et al., 2012). Similarly, research on woodland birds in central Victoria, Australia, demonstrated that fragmentation impedes gene flow in less mobile species, leading to reduced genetic connectivity and potential long-term genetic consequences (Amos et al., 2014).

Luther et al. (2020) compared the diversity and abundance of birds inside and outside forest fragments (the scattered forest patches left after deforestation) by setting up bird nets at different locations. The study aimed to assess the impact of forest fragments on bird communities. The results indicated that forest fragments significantly affected bird diversity and habitat patterns, with lower bird diversity and abundance typically observed at the fragment edges compared to the fragment interiors and continuous forests (Figure 2). These findings underscore the importance of preserving continuous forests and reducing forest fragmentation to maintain biodiversity.

Moreover, the effects of fragmentation on genetic diversity can vary significantly among species. A comparative study on eight tropical bird species revealed that habitat specialists are more adversely affected by fragmentation than generalists, indicating that ecological traits play a crucial role in determining a species' genetic response to habitat fragmentation (Khimoun et al., 2016). This finding underscores the importance of considering species-specific traits in conservation strategies to maintain genetic diversity and population viability in fragmented landscapes.

5.2 Dispersal and colonization abilities

Dispersal and colonization abilities are critical for the survival of bird populations in fragmented habitats. Fragmentation can create barriers to movement, reducing the ability of birds to disperse and colonize new areas. For example, a study on a Neotropical rainforest bird (Pyriglena leucoptera) found that individuals from fragmented landscapes exhibited higher resistance to boundary-crossing and increased dispersal success compared to those from continuous forests, suggesting that birds can adapt their dispersal behavior to fragmented environments (Cornelius et al., 2017). However, not all species exhibit such adaptive behaviors. Research on tropical forest birds in Panama showed extreme variation in flight capabilities among species, with some unable to traverse even short distances between fragments, highlighting the importance of maintaining connectivity to support dispersal and colonization (Moore et al., 2008).

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 (Hoover, 2006). These combined effects of increased predation and competition can lead to a decline in bird populations and increase the risk of local extinctions.

6.2 Reduced reproductive success

Habitat fragmentation can also lead to reduced reproductive success in bird populations. Fragmentation often results in smaller and more isolated patches of habitat, which can negatively impact the breeding success of birds. For example, studies have shown that nest predation and parasitism by cowbirds increase with forest fragmentation, leading to lower reproductive rates in fragmented landscapes. In some cases, the reproductive rates are so low that populations in fragmented habitats become sinks, relying on immigration from more extensive, unfragmented areas to sustain their numbers (Ruiz‐Gutierrez et al., 2008).

Additionally, fragmentation can disrupt the breeding activity of birds. Research has indicated that there is less breeding activity and fewer young birds in forest fragments after isolation compared to before isolation (Coddington et al., 2023). This reduction in breeding activity can be attributed to factors such as increased nest predation pressures and reduced recruitment of juveniles. For instance, in the Biological Dynamics of Forest Fragments Project near Manaus, Brazil, the proportion of actively breeding birds significantly decreased after fragment isolation, highlighting the negative impact of fragmentation on reproductive success (Coddington et al., 2023). These reductions in breeding activity and reproductive success can contribute to population declines and increase the risk of extinction in fragmented habitats.

6.3 Vulnerability to environmental changes

Bird populations in fragmented habitats are more vulnerable to environmental changes due to their reduced ability to move between habitat patches and adapt to changing conditions. Fragmentation can limit the movements of birds, making it difficult for them to find suitable habitats and resources. For example, studies have shown that landscape composition and configuration influence the movements of forest birds, with open areas acting as barriers to movement (Bélisle et al., 2001). This limited mobility can prevent birds from escaping unfavorable conditions or finding new breeding sites, increasing their vulnerability to environmental changes.

Furthermore, habitat fragmentation can lead to smaller home ranges and reduced foraging efficiency, which can negatively impact the physiological condition and reproductive success of birds. For instance, male northern saw-whet owls nesting in fragmented landscapes with low forest cover exhibited higher levels of chronic stress and lower provisioning rates, leading to reduced reproductive success and higher variation in the physiological condition of their young (Hinam and Clair, 2008). These factors can make bird populations in fragmented habitats more susceptible to environmental changes, such as climate change or habitat degradation, further increasing the risk of extinction.

7 Case Studies in Fragmentation Effects

7.1 Case study 1: effects on tropical forest birds

Habitat fragmentation has profound effects on tropical forest birds, often leading to population declines and local extinctions. A study conducted in the Usambara Mountains, Tanzania, analyzed 22 years of mark-recapture data to assess how fragmentation influenced survival, recruitment, and realized population growth rate within 22 forest understory bird species. The study found significantly lower apparent survival and realized population growth rates in small fragments compared to larger ones, indicating that fragmentation effects persist long after habitat loss. The depressed demographic rates were observed across various feeding guilds, suggesting that fragmentation sensitivity is not limited to insectivores. The study concluded that future population persistence is uncertain even within large forest fragments in this biodiversity hotspot (Korfanta et al., 2012).

Another study focused on the White-ruffed Manakin (Corapipo altera) in southern Costa Rica, where researchers found significant differences in annual adult apparent survival rates between individuals in forest fragments and those in a larger forest reserve. The results indicated that forest fragmentation likely affects population dynamics, putting populations at risk of local extinction despite appearing to persist in fragmented landscapes. The study emphasized the need for conservation actions aimed at identifying and reducing sources of adult mortality to mitigate the effects of fragmentation on tropical birds (Ruiz‐Gutierrez et al., 2008).

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).

8.2 Legal and policy frameworks

Legal and policy frameworks play a pivotal role in bird conservation by providing statutory recognition and protection for critical habitats. Policies should prioritize the preservation and restoration of large, unfragmented "core" areas, as these regions are essential for maintaining viable bird populations. Legal measures can also support the management of the landscape matrix, ensuring that it is conducive to the survival of native bird species. For example, discouraging the maintenance of open lawns on public and private properties can help preserve native vegetation and nesting structures (Marzluff and Ewing, 2001).

Moreover, international and national policies should address the control of invasive species, which pose a significant threat to bird populations in fragmented habitats. Effective predator control measures can mitigate the impact of invasive mammalian predators on native bird communities (Morgan et al., 2022). Additionally, policies should promote the integration of urban parks into native habitat systems and encourage urban planners to consider the ecological function of fragments in their designs (Marzluff and Ewing, 2001). By implementing comprehensive legal and policy frameworks, governments can create a supportive environment for bird conservation and habitat restoration efforts.

8.3 Community involvement and education

Community involvement and education are essential components of successful bird conservation strategies. Engaging local communities in conservation efforts can foster a sense of stewardship and responsibility for protecting bird habitats. Educational programs that raise awareness about the importance of habitat connectivity and the detrimental effects of fragmentation can empower communities to take action. For instance, community-based monitoring programs that measure bird fitness and population trends can provide valuable data for conservation planning (Marzluff and Ewing, 2001).

Involving communities in habitat restoration projects can also enhance the effectiveness of these initiatives. Local knowledge and participation can help identify critical areas for restoration and ensure that conservation actions are culturally and socially appropriate. Additionally, community involvement can lead to the development of innovative solutions for habitat management, such as creating urban green spaces that mimic native habitats (Marzluff and Ewing, 2001). By fostering a collaborative approach to bird conservation, communities can play a vital role in preserving biodiversity and maintaining healthy ecosystems.

9 Concluding Remarks

The systematic review of the effects of habitat fragmentation on bird behavior and extinction mechanisms reveals several critical insights. Fragmentation significantly impacts bird species, particularly in tropical regions where the disruption of biotic processes such as seed dispersal and insect herbivore control is mostsevere. Experimental studies in the Amazon have shown that fragmentation leads to the collapse of mixed-species flocks, with significant reductions in species richness and attendance. In the box-ironbark forests of central Victoria, Australia, predictions of species vulnerability to fragmentation were found to be unreliable, highlighting the complexity of species responses to habitat changes. Additionally, fragmentation impedes dispersal and gene flow, particularly in less mobile species, leading to reduced genetic connectivity. The non-random loss of species and the formation of distinct edge and interior communities further underscore the profound impact of fragmentation on avian community structure. Long-term studies in Tanzania have demonstrated that fragmentation leads to lower survival rates and population declines across multiple species. Moreover, fragmentation reduces avian breeding activity, which is a fundamental mechanism contributing to ecosystem decay. Finally, increased nest predation and parasitism in fragmented landscapes result in lower reproductive success, turning some populations into demographic sinks.

Future research should focus on several key areas to better understand and mitigate the effects of habitat fragmentation on bird populations. First, there is a need for more comprehensive studies that integrate multiple species with varying mobilities and ecological traits to develop more accurate predictive models of species vulnerability. Longitudinal studies that track demographic rates over extended periods are essential to understand the long-term impacts of fragmentation on survival and reproduction. Additionally, research should investigate the role of landscape connectivity and the potential for secondary growth habitats to serve as corridors for species movement and gene flow. Understanding the drivers behind non-random species loss and the nested structure of fragmented communities can inform conservation strategies aimed at preserving taxonomic diversity. Finally, experimental studies that manipulate fragment size and isolation can provide valuable insights into the mechanisms driving species declines and extinctions.

Conservation efforts must prioritize the preservation and restoration of large, contiguous habitats to maintain viable bird populations and ecosystem functions. Strategies should focus on creating and maintaining habitat corridors to facilitate species movement and gene flow, thereby enhancing genetic connectivity and reducing the risk of local extinctions. Protecting large core areas of forest is crucial to mitigate the effects of edge habitats and ensure higher reproductive success. Additionally, conservation plans should consider the specific ecological requirements and mobility of different bird species to tailor interventions effectively. Collaborative efforts between researchers, policymakers, and local communities are essential to implement and sustain conservation initiatives that address the multifaceted challenges posed by habitat fragmentation. By adopting a holistic approach that integrates scientific research with practical conservation actions, we can better safeguard bird populations and the ecosystems they inhabit for future generations.

Acknowledgements

Thanks to each peer reviewer for the suggestions on this manuscript.

Conflict of Interest Disclosure

The authors affirm that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.

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