Landscape features influencing gene flow and connectivity of an endangered passerine.

Dispersal of individuals and gene flow are crucial aspects to maintain genetic diversity and viability of populations, especially in the case of threatened species. Landscape composition and structure may facilitate or limit individual movement within and among populations. We used a landscape genetics approach to assess the connectivity patterns of the threatened Dupont's lark (Chersophilus duponti subsp. duponti), considering their genetic patterns and the landscape features associated with its gene flow in Spain. We analysed the genetic relatedness based on 11 species-specific polymorphic microsatellites on 416 Dupont's lark individuals sampled across peninsular Spain between 2017 and 2019, covering most of the European distribution of the species. To assess the relationship between the landscape composition and the species gene flow, we estimated genetic distance at the individual level (Dps). Next, we built a set of environmental surfaces from two time periods (years 1990 and 2018), based on factors such as land use and topography, influencing individuals' movement. We then obtained resistance surfaces from an optimization process on landscape variables. Landscape genetics analyses were done for single and composite surface models for each year separately. Our findings from both time points show that scatter or mosaic-structured vegetation composed by low agricultural and tree cover and high presence of sclerophyllous shrubs favoured Dupont's lark dispersal, while dense and continuous tree cover, as well as areas of intensive agriculture, were limiting factors. Our results suggest the importance of steppe habitat patches for the species' establishment and dispersal. In addition, our results provide key information to develop conservation measures, including conserving and restoring steppe habitats as scattered and/or mosaic-structured vegetation that could warrant the connectivity and persistence of Dupont's lark populations.

Increased density of conspecifics caused niche contraction in a multispecific passerine assemblage.

Competition is a prominent mechanism driving population dynamics and structuring community assemblage, which can be investigated by linking shifts in species' ecological niche and the densities of sympatric species because the ecological release from competitive constraints is a density-dependent process. In this work we determine how a steppe passerine community segregates their ecological niches and evaluate the role of competition in inducing changes in the ecological niche of species. We built multidimensional ecological niches (with Gaussian kernel density estimators) using data on the habitat features used by 10 bird species collected from seven sites in the natural steppes of Central Spain over 2 consecutive years. We computed distance and niche similarity metrics to explore the ecological niche partitioning of the bird community. Next, we ran multivariate linear regression models to evaluate the effects of conspecific and heterospecific density (as proxies of intraspecific and interspecific competition, respectively) on niche breadth and/or position of the three most abundant species. We found low niche overlap in the community assemblage but varying levels of niche similarity among pairs of species, which could increase the likelihood of current competition operating in the community. However, we found no effect of heterospecific density on niche breadth or position, although conspecific density was negatively related to niche breadth. Contrary to predictions of competition theory, increased density of conspecifics caused niche contraction. Our results from a multispecies system contribute to advanced knowledge of the biotic mechanisms structuring wildlife communities within the framework of ecological niche theory.

Wind farm noise shifts vocalizations of a threatened shrub-steppe passerine.

Wind energy has experienced a notable development during the last decades, driving new challenges for animal communities. Although bird collisions with wind turbines and spatial displacement due to disturbance have been widely described in the literature, other potential impacts remain unclear. In this study, we addressed the effect of turbine noise on the vocal behaviour of a threatened shrub-steppe passerine highly dependent on acoustic communication, the Dupont's lark Chersophilus duponti. Based on directional recordings of 49 calling and singing males exposed to a gradient of turbine noise level (from 15 up to 51 dBA), we tested for differences in signal diversity, redundancy, and complexity, as well as temporal and spectral characteristics of their vocalizations (particularly the characteristic whistle). Our results unveiled that Dupont's lark males varied the vocal structure when subject to turbine noise, by increasing the probability of emitting more complex whistles (with increased number of notes) and shifting the dominant note (emphasizing the longest and higher-pitched note). In addition, males increased duration and minimum frequency of specific notes of the whistle, while repertoire size and signal redundancy remain constant. To our knowledge, this is the first study reporting multiple and complex responses on the vocal repertoire of animals exposed to turbine noise and unveiling a shift of the dominant note in response to anthropogenic noise in general. These findings suggest that the Dupont's lark exhibits some level of phenotypic plasticity, which might enable the species to cope with noisy environments, although the vocal adjustments observed might have associated costs or alter the functionality of the signal. Future wind energy projects must include fine-scale noise assessments to quantify the consequences of chronic noise exposure.

European population trends and current conservation status of an endangered steppe-bird species: the Dupont's lark Chersophilus duponti.

BACKGROUND: Steppe-birds face drastic population declines throughout Europe. The Dupont's lark Chersophilus duponti is an endangered steppe-bird species whose European distribution is restricted to Spain. This scarce passerine bird could be considered an 'umbrella species', since its population trends may reveal the conservation status of shrub-steppes. However, trends for the Spanish, and thus European, population of Dupont's lark are unknown. In this work, we evaluated Dupont's lark population trends in Europe employing the most recent and largest compiled database to date (92 populations over 12 years). In addition, we assessed the species threat category according to current applicable criteria (approved in March 2017) in the Spanish catalogue of threatened species (SCTS), which have never been applied to the Dupont's lark nor to any other Spanish species. Finally, we compared the resulting threat categories with the current conservation status at European, national and regional levels. METHODS: We fitted switching linear trend models (software TRIM-Trends and Indices for Monitoring data) to evaluate population trends at national and regional scale (i.e. per Autonomous Community) during the period 2004-2015. In addition, the average finite annual rate of change ( λ ¯ ) obtained from the TRIM analysis was employed to estimate the percentage of population size change in a 10-year period. A threat category was assigned following A1 and A2 criteria applicable in the SCTS. RESULTS: Trends showed an overall 3.9% annual decline rate for the Spanish population (moderate decline, following TRIM). Regional analyses showed high inter-regional variability. We forecasted a 32.8% average decline over the next 10 years. According to these results, the species should be listed as 'Vulnerable' at a national scale (SCTS). At the regional level, the conservation status of the species is of particular concern in Andalusia and Castile-Leon, where the species qualifies for listing as 'Endangered'. DISCUSSION: Our results highlight the concerning conservation status of the European Dupont's lark population, undergoing a 3.9% annual decline rate. Under this scenario, the implementation of a wide-ranging conservation plan is urgently needed and is vital to ensuring the conservation of this steppe-bird species. The role of administrations in matters of nature protection and the cataloguing of endangered species is crucial to reverse declining population trends of this and other endangered taxa.