Human-modified Landscapes Research Articles

Land-use homogenization reduces the occurrence and diversity of frugivorous birds in a tropical biodiversity hotspot.

Understanding how human-modified landscapes maintain biodiversity and provide ecosystem services is crucial for establishing conservation practices. Given that responses to land-use are species-specific, it is crucial to understand how land-use changes may shape patterns of species diversity and persistence in human-modified landscapes. Here, we used a comprehensive data set on bird distribution from the Brazilian Atlantic Forest to understand how species richness and individual occurrences of frugivorous bird species responded to land-use spatial predictors and, subsequently, assess how ecological traits and phylogeny modulated these responses. Using Bayesian hierarchical modeling, we reveal that the richness of frugivorous birds was positively associated with the amount of native forest and negatively with both agriculture and pasture amount at the landscape scale. Conversely, the effect of these predictors on species occurrence and ecological traits was highly variable and presented a weak phylogenetic signal. Furthermore, land-use homogenization (i.e., the conversion of forest to pasture or agriculture) led to pervasive consequences for forest-dependent bird species, whereas several generalist species thrived in deforested areas, replacing those sensitive to habitat disturbances.

Negative effects of human disturbance and increased aridity on root biomass and nutrients along the regeneration of a tropical dry forest in the context of slash-and-burn agriculture

Biomass is an important indicator of the ability of tropical forests to deliver ecosystem services, but little attention has been given to belowground biomass and its drivers in human-modified landscapes. Here, we investigated the belowground biomass and nutrient concentration/stocks (C, P, and N) across regenerating forest stands with varying ages (10–76 years old) and old-growth forests in the Caatinga dry forest (northeastern Brazil) in the context of slash-and-burn agriculture. Belowground biomass ranged from 1.89 ± 0.33 Mg ha−1 to 17.53 ± 2.28 Mg ha−1 (mean ± SE) across regenerating forest stands and averaged 8.33 ± 1.59 Mg ha−1, with no differences compared to old-growth stands. However, regenerating stands exhibited a higher root/shoot ratio with biomass concentrated in the superficial soil layer and in large-sized roots, regardless of the successional stage. Root nutrient concentration and stocks were highly variable across forest stands with fine roots supporting a higher concentration of N and P, while regenerating stands supported lower nutrient stocks as compared to old-growth forests. Finally, precipitation and chronic disturbance emerged as the most important drivers of belowground biomass and nutrient concentrations/stocks, while aboveground biomass played a negligible role. Our results indicate that, in human-modified landscapes of tropical dry forests, belowground biomass and nutrients play important roles in ecosystem functions in regenerated forests after slash-and-burn agriculture. Forest resilience and provision of ecosystem services (e.g., nutrient cycling) appear to be very sensitive to increased aridity and exploitation of forest resources.

Ethnoprimatology reveals new extended distribution of critically endangered banded langur Presbytis femoralis (Martin, 1838) in Pahang, Malaysia: Insights from indigenous traditional knowledge and molecular analysis.

The banded langur (Presbytis femoralis) is a critically endangered primate, which within Malaysia has not been known to extend significantly outside the state of Johor. Traditionally, distribution studies on this highly threatened primate have relied on conventional methods such as DNA identification, live counting, and camera trapping. However, ethnoprimatology offers an alternative approach to data collection, involving the active participation of indigenous and local communities possessing valuable knowledge and experience with local primate species. This study employed an integrated approach incorporating ethnoprimatology by utilizing pooled local expert opinion, local surveys, interviews, and fecal DNA analysis, resulting in a novel distribution range for the banded langur. The combination of expert opinions revealed this species' most optimistic distribution scenario across Johor and Pahang, inhabiting various ecosystems, including lowland forests, peat swamps, and human-modified landscapes. Further interviews and surveys conducted within the Orang Asli community in Tasik Chini and Tasek Bera have provided additional support for the revised distribution, documenting occurrences of banded langur utilization in indigenous practices, such as food consumption, cultural beliefs, medicinal applications, and craftsmanship. Phylogenetic analysis demonstrated genetic differentiation between populations in Johor and Pahang, with the populations in the southern part of Peninsular Malaysia likely serving as ancestral sources for other populations. Consequently, this study not only elucidated the updated distribution of banded langur through DNA records and direct observations but also established the efficacy of ethnoprimatology as a precursory tool for uncovering the present distribution patterns of other primate species in Malaysia.

Community-managed forests can secure forest regrowth and permanence in human-modified landscapes

Deforestation can impair ecosystem functions, reduce biodiversity, and accelerate climate change. One strategy proposed to decrease deforestation and promote recovery of degraded areas involves community management of forests: entrusting local communities to manage forest reserves. However, the effectiveness of this strategy remains poorly understood. Here, we assess the impact of community forest management in the Village Land Forest Reserves (VLFRs) of the Greater Gombe Ecosystem (GGE), Tanzania, using Landsat satellite images from multiple dates (2006, 2013, and 2021) to assess the extent to which 16 VLFRs promoted forest regrowth and permanence. We detected a 66 % forest cover increase in VLFRs but a 22 % decrease in identified areas not under any form of protection (unprotected area) in the village land. The Before-After-Control-Impact (BACI) statistical analysis showed that assigning an area as a VLFR was associated with a 24.3 % forest-cover gain compared to unprotected village land (β = 0.243, SE = 0.0761, P<0.001). Patrolling by local community members, following village regulations, has a positive impact (β=0.04, 95% CI: [0.02, 0.06]) on promoting forest cover persistence. Nonetheless, of land reforested between 2006 and 2013 in the VLFRs, 11 % suffered re-clearing by 2021. Ensuring further forest regeneration and persistence of these reserves thus requires additional measures.

Effective dispersal patterns in prairie plant species across human-modified landscapes.

Effective dispersal among plant populations is dependent on vector behaviour, landscape features and availability of adequate habitats. To capture landscape feature effects on dispersal, studies must be conducted at scales reflecting single-generation dispersal events (mesoscale). Many studies are conducted at large scales where genetic differentiation is due to dispersal occurring over multiple generations, making it difficult to interpret the effects of specific landscape features on vector behaviour. Genetic structure at the mesoscale may be determined by ecological and evolutionary processes, such as the consequences of vector behaviour on patterns of gene flow. We used chloroplast haplotypes and nuclear genome SNP surveys to identify landscape features influencing seed and pollen dispersal at a mesoscale within the Rogue River Valley in southern Oregon. We evaluated biotic and abiotic vector behaviour by contrasting two annual species with differing dispersal mechanisms; Achyrachaena mollis (Asteraceae) is a self-pollinating and anemochoric species, and Plectritis congesta (Caprifoliaceae) is biotically pollinated with barochoric seeds. Using landscape genetics methods, we identified features of the study region that conduct or restrict dispersal. We found chloroplast haplotypes were indicative of historic patterns of gene flow prior to human modification of landscapes. Seed dispersal of A. mollis was best supported by models of isolation by distance, while seed-driven gene flow of P. congesta was determined by the distribution of preserved natural spaces and quality habitat. Nuclear genetic structure was driven by both pollen and seed dispersal, and both species responded to contemporary landscape changes, such as urban and agricultural conversion, and habitat availability.

Human habitat modification, not apex scavenger decline, drives isotopic niche variation in a carnivore community.

Top carnivores can influence the structure of ecological communities, primarily through competition and predation; however, communities are also influenced by bottom-up forces such as anthropogenic habitat disturbance. Top carnivore declines will likely alter competitive dynamics within and amongst sympatric carnivore species. Increasing intraspecific competition is generally predicted to drive niche expansion and/or individual specialisation, while interspecific competition tends to constrain niches. Using stable isotope analysis of whiskers, we studied the effects of Tasmanian devil Sarcophilus harrisii declines upon the population- and individual-level isotopic niches of Tasmanian devils and sympatric spotted-tailed quolls Dasyurus maculatus subsp. maculatus. We investigated whether time since the onset of devil decline (a proxy for severity of decline) and landscape characteristics affected the isotopic niche breadth and overlap of devil and quoll populations. We quantified individual isotopic niche breadth for a subset of Tasmanian devils and spotted-tailed quolls and assessed whether between-site population niche variation was driven by individual-level specialisation. Tasmanian devils and spotted-tailed quolls demonstrated smaller population-level isotopic niche breadths with increasing human-modified habitat, while time since the onset of devil decline had no effect on population-level niche breadth or interspecific niche overlap. Individual isotopic niche breadths of Tasmanian devils and spotted-tailed quolls were narrower in human-modified landscapes, likely driving population isotopic niche contraction, however, the degree of individuals' specialisation relative to one another remained constant. Our results suggest that across varied landscapes, mammalian carnivore niches can be more sensitive to the bottom-up forces of anthropogenic habitat disturbance than to the top-down effects of top carnivore decline.

Proximity to natural forests failed to rescue a declining agroforestry tree species

The conservation of species in human-modified landscapes such as agroforestry systems is central to global conservation and sustainable use of biodiversity. Understanding the dynamics of key species in agroforestry systems is important for predicting the sustainability of these systems. However, the population dynamics of agroforestry tree species are often unknown, and planning for the management of these systems is generally grounded on the untested assumption that the tree component will persist over time. Here, we developed an integral projection model for Vitellaria paradoxa (Sapotaceae), one of the most important tree species in traditional agroforestry systems in West Africa. We collected three years of demographic data from six populations around the Pendjari Biosphere Reserve in Benin to parameterize this model and test the effect of populations’ proximity to natural habitats on the short- and long-term dynamics of V. paradoxa. However, models suggest that V. paradoxa populations are projected to decline at a yearly rate of 10.6% and within the next two decades, this tree will be locally extinct. We found a significant positive effect of proximity to natural forest on the long-term population dynamics, but this failed to save populations from decline. Elasticity analyses show that the best strategy to slow down such a decline includes preserving the largest mature trees. However, traditional management systems that protect shea butter trees in agroforestry systems are now replaced by increasing tree cutting to produce firewood, charcoal and carve out mortars and pestles. The decline of this key agroforestry tree poses a broader threat to long-term sustainability of agroforestry systems.

Anthropogenic activities facilitate temporal overlaps and spatial partitions among sympatric canids in a human-modified landscape of Bulgaria

Mammalian carnivores (order Carnivora) occupy higher trophic levels in many terrestrial ecosystems, shaping community structures via direct predation and trophic cascades. The interference competition among sympatric carnivores (i.e., aggression and killing) has a major role in the intraguild interactions in which the large-dominant predators typically constrain behaviors and resource use patterns by exploitative (i.e., resource) competitions as well as the survival of smaller subordinate species by interference (i.e., direct) competitions. The free-roaming dog, Canis lupus familiaris, has been introduced worldwide and the species affects regional biodiversity, including native carnivore species. Using camera trapping, we investigated the temporal and spatial overlaps between the free-roaming dog and two wild canids, the golden jackal (Canis aureus) and the red fox (Vulpes vulpes), in different landscapes of central Bulgaria. We predict their interference interactions, namely that the dog, as the largest competitor, suppresses the golden jackal with intermediate body size, and, in turn, the golden jackal suppresses the smaller red fox. In mountainous forest landscapes where the free-roaming dog was absent or scarce, the golden jackal and red fox partitioned their diel activities, while there were moderate levels of spatial overlap. In agricultural lowlands where dogs were abundant and anthropogenic disturbances were relatively high, all three canids were primarily nocturnal with high temporal overlap, probably owing to human activities (e.g., hunting) in the daytime. The golden jackal was spatially separated from the dog, whereas the red fox spatially overlapped with large dogs. Our results indicated that, in human-modified landscapes with scattered forests and shrubs, spatial partitioning between the free-roaming dog and the golden jackal at fine spatial scales facilitates their sympatry by decreasing the probability of direct encounters. Furthermore, our findings also indicate that spatiotemporal interactions between the golden jackal and the red fox can change in association with various human disturbances, e.g., landscape modifications, human activities, and the introduction of dogs.

The relative influence of landscape features on maternity roost and hibernaculum selection in temperate bats

Many animal life-history stages center around residences (nests, roosts, etc.) where the availability of resources within an optimal range can affect fitness. Understanding factors influencing residence selection is fundamental for efficient management or recovery plans. Many bat species use permanent roosts during different periods of the year, and while most conservation plans aim to protect these roosts, the availability of suitable habitat near the roosts (e.g., foraging habitat) is also critical to consider. We evaluated the importance of landscape features at multiple scales surrounding seasonal bat roosts in two regions (north and south) of Québec (Canada), using data from participatory science and government databases. In the human-altered environment of south Québec, bats selected maternity roosts with high anthropogenic cover and water edge density at the 150 m and 2 km scales, respectively. Conversely, roost selection in north Québec, a forested area, could not be explained by any landscape features. In winter, fewer bats used hibernacula located in heavily human-modified landscapes—opposite to the trend observed with maternity roost selection. Our study demonstrates how considering landscape features at the appropriate temporal and spatial scales can promote more efficient conservation for bats.

Long-term change in the tree community of a tropical forest remnant surrounded by human-modified landscapes

Long-term change in the tree community of a tropical forest remnant surrounded by human-modified landscapes

Brown bear digging decreases tree growth: Implication for ecological role of top predators in anthropogenic landscapes.

Large carnivores have recently increased in number and recolonized in human-dominated landscapes; however, their ecological roles in these landscapes have not been well studied. In the Shiretoko World Heritage (SWH) site, brown bears have recolonized a previously abandoned mosaic landscape of natural forests and conifer plantations after land abandonment. We previously reported that the bears had recently begun to dig for cicada nymphs in association with the creation of larch plantations. As a result, this digging activity decreased soil nutrients. To deepen the understanding of the novel ecological role of brown bears within human-modified landscapes, we examined the impacts of brown bear digging on the growth of larch trees. We found that brown bear digging decreased fine root biomass of larch, soil water, and nitrogen availability. Brown bear digging negatively affected needle nitrogen content, but not carbon isotope ratios, a water stress index of trees. Tree ring data suggest that digging negatively affected the radial growth of larches. The results imply that digging decreases tree growth due to limited soil nitrogen uptake. Our findings indicate that the ecological roles of large carnivores may differ between natural and anthropogenic landscapes.

New threats in the recovery of large carnivores inhabiting human-modified landscapes: the case of the Cantabrian brown bear (Ursus arctos)

Understanding mortality causes is important for the conservation of endangered species, especially in small and isolated populations inhabiting anthropized landscapes where both natural and human-caused mortality may hinder the conservation of these species. We investigated the mortality causes of 53 free-ranging brown bears (Ursus arctos) found dead between 1998 and 2023 in the Cantabrian Mountains (northwestern Spain), a highly human-modified region where bears are currently recovering after being critically threatened in the last century. We detected natural traumatic injuries in 52.63% and infectious diseases in 39.47% of the 38 bears for which the mortality causes were registered, with 21.05% of these cases presenting signs of both infectious diseases and traumas. More specifically, almost 30% of the bears died during or after intraspecific fights, including sexually selected infanticide (10.53%). In addition, primary infectious diseases such as infectious canine hepatitis, distemper, clostridiosis and colibacillosis caused the death of 15.79% of the bears. The number of direct human-caused deaths (i.e., shooting, poisoning, snare) decreased over the study period. This study also reveals three new mortality causes triggered by pathogens, two of which—Clostridium novyi and verotoxigenic Escherichia coli—not previously described in ursids, and the other one, canine distemper virus, never reported in brown bears as cause of death. New management strategies for the conservation of Cantabrian bears, which are urgently needed due to the rapid expansion of the population, should consider the mortality causes described in this study and must promote further research to elucidate how the high prevalence of infectious diseases may threaten the current recovery of the population.

The bii4africa dataset of faunal and floral population intactness estimates across Africa’s major land uses

Sub-Saharan Africa is under-represented in global biodiversity datasets, particularly regarding the impact of land use on species’ population abundances. Drawing on recent advances in expert elicitation to ensure data consistency, 200 experts were convened using a modified-Delphi process to estimate ‘intactness scores’: the remaining proportion of an ‘intact’ reference population of a species group in a particular land use, on a scale from 0 (no remaining individuals) to 1 (same abundance as the reference) and, in rare cases, to 2 (populations that thrive in human-modified landscapes). The resulting bii4africa dataset contains intactness scores representing terrestrial vertebrates (tetrapods: ±5,400 amphibians, reptiles, birds, mammals) and vascular plants (±45,000 forbs, graminoids, trees, shrubs) in sub-Saharan Africa across the region’s major land uses (urban, cropland, rangeland, plantation, protected, etc.) and intensities (e.g., large-scale vs smallholder cropland). This dataset was co-produced as part of the Biodiversity Intactness Index for Africa Project. Additional uses include assessing ecosystem condition; rectifying geographic/taxonomic biases in global biodiversity indicators and maps; and informing the Red List of Ecosystems.

Agricultural landscape composition alters ant communities in maize fields more than plant diversity enrichment

Abstract. Pasaribu DN, Rizali A, Tarno H, Priawandiputra W, Johannis M, Buchori D. 2024. Agricultural landscape composition alters ant communities in maize fields more than plant diversity enrichment. Biodiversitas 25: 205-213. Fragmented natural habitats in human-modified landscapes play a crucial role in conserving biodiversity. Ants, as keystone species, are integral to terrestrial ecosystems, making it essential to comprehend the factors influencing their survival. This study investigates the impact of agricultural landscape composition and plant diversity enrichment (flowering plants) management on shaping ant communities in maize (Zea mays L.) fields. The research occurred in maize fields surrounded by other crops, semi-natural habitats, and housing areas in Malang District, East Java, Indonesia. The four agricultural areas were divided into control and treatment plots, considering landscape composition parameters, particularly Class Area (CA) and the Number of Patches (NP), measured within a 500 m radius. The landscape around the maize fields was characterized by manually digitizing land use. Six types of plant diversity enrichment were employed in this study: wild cosmos (Cosmos caudatus), white buttercup (Turnera subulata), sunflower (Helianthus annuus), long bean (Vigna unguiculata), ornamental bean (Arachis pintoi), and coral vine (Antigonon leptopus). The study was divided into the dry season (April-July 2022) and the wet season (September-December 2022). Ant sampling was conducted using pitfall traps and, based on generalized linear models, revealed that plant diversity enrichment management did not affect species richness, abundance, or composition of ants. Landscape composition positively influenced ant species richness but negatively impacted species composition, particularly the number of semi-natural habitat patches. Maize crop age also positively influenced ant species richness but negatively affected beta diversity. Wet season was also found to have a negative effect on beta diversity. In conclusion, the proportion of semi-natural habitats in agricultural landscapes and crop age contribute significantly to species richness and species composition of ants.

Size records and demographics of an Eastern Painted Turtle (&lt;i&gt;Chrysemys picta picta&lt;/i&gt;) urban population near the northern limit of the species’ range in eastern Canada

Understanding variation in demographics and life history across species ranges and differing landcover types is valuable for conservation planning. We examined the population demographics of a small urban population of Eastern Painted Turtle (Chrysemys picta picta) in New Brunswick, Canada, near the northern limit of the species’ range. We captured turtles using hoop traps and by hand during four sampling periods. We estimated that our population included 17 females, nine males, and 29 juveniles in late summer 2015 using Jolly-Seber population size estimates. We captured several very large females at our study site; 5/17 females (29%) were larger than previous size records for the subspecies. Growth rates for juveniles were greater than most populations of Eastern Painted Turtles reported elsewhere. Growth rates at our site were significantly greater for smaller (younger) turtles and for females compared to males. Overwinter survivorship estimates were 100% from late summer 2014 to spring 2015. Active season (2015) survivorship was 100% for females, 89% for males, and 93% for juveniles. We speculate that the large body sizes found at our study site were achieved through high survivorship and larger growth rates compared to other areas reported previously. Our data supports previous findings that body size of Painted Turtles increases with latitude, and additionally, growth may have been enhanced by increased nutrient levels common in human-modified landscapes.

Recovery of the reproductive functional diversity of edible fruit plant assemblages along the regeneration of a Caatinga dry forest

The ability of dry forests to deliver ecosystem services of both local and global relevance depends on the capacity of those forests to recover from constant disturbances in human-modified landscapes. Here we examine the effects posed by biomass, chronic human disturbances and aridity on the recovery of reproductive functional diversity by edible fruit plant assemblages following slash-and-burn agriculture in a Caatinga dry forest, in northeastern Brazil. The edible fruit plant assemblages were described across 24 forest stands, including regenerating stands of varying age (4 to 50 yr old) and old-growth stands, adopting a large set of reproductive traits as floral sizes, reproductive systems, and pollination systems. Such a chronosequence covered a gradient relative to aboveground biomass, aridity, and chronic anthropogenic disturbances (CAD). We observed that edible fruit plant assemblages across both regenerating and old-growth forest stands exhibited similar taxonomic diversity scores. This pattern is also figured in the recovery of reproductive traits, which is relatively fast as regenerating forest scores are generally similar or higher to those in old-growth forests. Generally, regenerating forest stands support more specialized reproductive traits and strategies than old-growth forest stands [e.g., edible fruit plants with very large flowers (>30 mm), specialized pollination systems, large fruits (>1.5 ≤3.0 mm), and medium-sized seeds (>0.6 ≤1.5 cm). However, the functional diversity of specialist reproductive traits decreased with increases in the levels of biomass and aridity, isolated, but was also impacted by the interactive effect. Considering the effects of biomass, CAD or aridity individually, we observed that biomass itself was responsible for most of the effects (42.8%), while 52.3% of the reproductive traits were negatively affected by CAD or aridity, which seems to be a major force against the recovery.

Brown bear food habits in natural and human-modified landscapes in West-European Russia

Brown bear food habits in natural and human-modified landscapes in West-European Russia

Elevated litterfall phosphorus reduces litter and soil organic matter pools in exotic-dominated novel forests in Singapore

Abstract The estimation of leaf litter turnover is often limited to early-stage decomposition using unrepresentative models and litter types. In tropical secondary forests, particularly exotic-dominated novel forests, the characterisation of litter turnover remains poor. This study estimated the annual turnover of in-situ leaf litter across four forest successional types in Singapore using a Weibull residence time model. Litter turnover and nutrient dynamics diverged between young secondary and old-growth forests. In particular, within novel forests, annual phosphorus return via leaf litterfall was three times that of primary forests, while the mass loss of in-situ leaf litter was highest among all forest successional types, estimated at 92.8% annually with a mean residence time of 176 days, resulting in a litter pool size a third that of primary forests. Our findings suggest that tree species composition and species-specific effects shaped the observed variations in litter turnover and nutrient dynamics across forest successional types and forest stands, whereas tree species richness, canopy structure, soil nutrient levels, and microclimate were found to be non-predictors. Taken together, our study provides an insight into litter turnover in human-modified tropical landscapes increasingly characterised by novel forests, potentially leading to a reduction in surface litter and soil organic carbon pools.

Effect of landscape attributes on the occurrence of the endangered golden-headed lion tamarin in southern Bahia, Brazil.

The golden-headed lion tamarin (Leontopithecus chrysomelas) is an endangered primate that occurs exclusively in the Atlantic Forest of southern Bahia, Brazil. Its geographic range has been severely reduced by deforestation and its populations are restricted to a human-modified landscape consisting primarily of Atlantic forest fragments and shade cacao (Theobroma cacao) agroforestry, locally known as cabrucas. In the last 30 years, there has been a 42% reduction in the geographic range and a 60% reduction in the population size of L. chrysomelas, with only 8% of its habitat represented by protected areas. Thus, we investigated the occurrence of L. chrysomelas in forest fragments and cabrucas based on interviews and using playback census, and evaluated the influence of landscape attributes on its occurrence. The occurrence was measured using a Generalized Linear Model using a set of 12 predictor variables, including fragment size and elevation. L. chrysomelas inhabited 186 (38%) of the 495 forest fragments and cabrucas. Most inhabited habitat patches (n = 169, 91%) are in the eastern portion (ca. 70 km wide region from the Atlantic coast to inland) of its geographic range. The remaining (n = 17, 9%) are in the western portion of the distribution, between 70 and 150 km from the Atlantic coast. Our models indicate a higher occurrence of L. chrysomelas in the eastern portion of its geographic range, where the landscape exhibits lower land cover diversity, greater functional connectivity, lower altitudes (<400 m), and is primarily composed of forest fragments and cabrucas with a higher core percentage. In contrast, we observed a lower occurrence of L. chrysomelas in the western portion, where the landscape is more diverse and heterogeneous due to anthropogenic activities, such as agriculture and livestock. We urge the establishment of ecological corridors via reforestation of degraded areas in the western portion of the range. This increase in habitat availability and suitability in the west together with the protection of the forests and cabrucas in the east would increase our chances of saving L. chrysomelas from extinction.

The effects of anthropogenic noise and urban habitats on song structure in a vocal mimic; the gray catbird (Dumetella carolinensis) sings higher frequencies in noisier habitats

In urban and human-modified landscapes, animals face novel selection pressures resulting from differences in habitat structure and increased anthropogenic noise. Urban noise pollution can negatively impact songbirds because low-frequency noise often masks portions of birds’ mating signals and reduces signal transmission. Previous research has demonstrated that the songs of birds in more urban habitats have structural differences that can enhance signal transmission when noise is present. The majority of these studies have focused on species that deliver short, stereotyped songs and have limited repertoires. Gray catbirds (Dumetella carolinensis, family: Mimidae) sing long bouts containing imitated, improvised, and invented song elements, and therefore may have an increased ability to vary songs in response to noise. We hypothesized that aspects of developed habitats including loud anthropogenic noise and changes to land cover would impact catbirds’ song structural parameters, including song minimum, peak, and maximum frequency, frequency bandwidth, and entropy. We recorded and processed songs from 42 male catbirds and analyzed over 18,000 song elements from sites along an urban gradient from western Virginia to the Washington, DC metropolitan region. We quantified the urban intensity at each site-centroid based on percent canopy cover, percent impervious surface, and noise level. Song features such as minimum, maximum, and peak frequency increased significantly as noise levels increased, demonstrating that catbirds in noisier areas sing higher frequency songs compared to individuals in quieter habitats. Land cover variables also significantly predicted certain song features such as maximum frequency (impervious surface) or entropy (canopy cover). These structural differences in catbird song can limit the negative effects of environmental noise-masking, even for their long song bouts, and suggest that vocal mimics respond to anthropogenic noise. Future studies could investigate repertoire size and composition along an urban gradient and if these structural differences lead to functional consequences for the songs of vocal mimics.