Vicente Garza

Is the European population of Dupont's Lark Chersophilus duponti adequately estimated?

Capsule Our estimate using mapping is less than previously reported using transects.

The role of extensive cereal crops, dry pasture and shrub-steppe in determining skylark Alauda arvensis densities in the Iberian peninsula

Abstract Density and habitat selection of skylarks Alauda arvensis L. were studied in 65 localities of central and southern Iberia. Density was analysed in relation to climatic and geographic variables, as well as to habitat type, by means of linear regression models. Habitat selection was assessed by analysing the relationship of the species’ presence with vegetation structure using logistic regression. When all localities were considered, density of breeding skylarks was associated to altitude. During winter, skylark range increased and abundance was related to habitat type. Skylark winter density in dry pasture was 10–20 times higher than in any other habitats. Differences between winter and spring density presented a pattern similar to that found in winter and maximum values were reached in dry pasture. Summer and winter skylark presence showed an association to pasture and shrub

Short-Term Effects of a Wildfire on the Endangered Dupont's Lark Chersophilus duponti in an Arid Shrub-Steppe of Central Spain

Abstract. In Europe, Duponts Lark Chersophilus duponti is a threatened open-habitat bird. Prescribed burning has sometimes been proposed for its conservation, but without evidence of its effectiveness. To evaluate the short-term effects of a summer wildfire on this species, we performed several transect counts in the burnt and unburnt parts of a shrubsteppe in central Spain. The same transects were counted within a three-year interval prior to the fire and were repeated during the first two springs after the fire. We also measured the vegetation during the first two springs after the fire. In the burnt area, we observed a decrease of about 85–100% in Duponts Lark abundance, and about 7–15% in the control area. The disappearance of the scrub cover after fire and its slow regeneration, as well as the large increase in grass cover during the second year, may explain the decrease in this habitat-specialist bird species. Fire should be avoided in areas occupied by the Duponts Lark, as its negative effects in the short-term may cause local extinctions. However, prescribed burning may be used in neighboring areas to create new open habitats that may be subsequently colonized by this species.

The non-breeding distribution of Dupont's Lark Chersophilus duponti in Spain

Summary In this paper, we analyse the non-breeding distribution of Dupont’s Lark, one of Europe’s most threatened and least known passerines, using breeding and wintering censuses, published and unpublished records of individuals outside their breeding areas, and data on radio-tagged individuals and field observations. Results suggest that most breeding Dupont’s Larks remain around the breeding sites during the non-breeding season, including those populations from areas with harsh winter weather conditions. The probability of winter presence of Dupont’s Larks in breeding areas was significantly correlated with population size, but the altitude of the locality studied did not influence winter presence. Records outside breeding areas indicate that part of the population moves some distance after breeding, occupying lower sites and principally those with agrarian substrates. We also found several records far from well-known breeding areas during the breeding period. Our results suggest that Dupont’s Lark seems to be a partial migrant, wintering in breeding areas in large numbers (probably the adult fraction of the population) but with some part of the populations moving to other areas. The movements are short-distance in most cases, although medium- and long-distance dispersive movements were also detected. We discuss the implications of these results for the design of specific conservation measures for the species.

Wind farms affect the occurrence, abundance and population trends of small passerine birds: The case of the Dupont's lark

Handling Editor: Ailsa McKenzie Abstract 1. The assessment of the effects of wind farms on bird populations is commonly based on collision fatality records. This could undervalue the effect of wind farms on small-sized birds. We evaluate the effect of wind turbines on occurrence, abundance and population trends of a threatened small passerine species, the Dupont’s lark Chersophilus duponti. To our knowledge, this is one of the first studies addressing the effect of wind farms on population trends using time-series data from multiple wind farms. 2. We estimated population trends by fitting a switching linear trend model with the software trim (Trend & Indices for Monitoring data). We used multiannual data surveys of five populations in the presence of wind farms and nine in their absence (2008–2016 period). Furthermore, we fitted a logistic and a negative binomial regression model to test the effect of wind farm proximity on species occurrence and abundance in 2016, respectively. We incorporated local connectivity and habitat availability estimates in both models as predictors. 3. Results showed a negative trend overall, but that was significantly more regressive in the presence of wind farms: 21.0% vs. 5.8% average annual decline in the absence of wind farms. 4. Dupont’s lark occurrence and abundance in 2016 were negatively affected by measures of population isolation and positively affected by the distance to wind farms. 5. These results highlight the negative effect of isolation and wind farm proximity on Dupont’s lark population parameters. Taking into account the metapopulation structure exhibited by the species in the study area, this work established a 4.5-km threshold distance from wind farms, beyond which Dupont’s lark populations should be unaffected. 6. Synthesis and applications. This work highlights the negative impact of wind farms on small-sized birds and provides a 4.5-km threshold distance that should be taken into account in the design of future wind energy projects. Moreover, we suggest an analytical approach based on population trends, species abundance and occurrence variation in relation to wind farms, useful for the assessment of wind farm impacts on small-sized birds.

Climate, isolation and intraspecific competition affect morphological traits in an endangered steppe bird, the Dupont’s Lark Chersophilus duponti

ABSTRACT Capsule: We assess biometric variation in the threatened Dupont’s Lark along a wide fraction of its distribution area analysing the largest data set for this bird species available to date, comprising a 28-year period and including birds captured in Spain, Morocco and Tunisia. Aims: To analyse Dupont’s Lark morphology evaluating five potential sources of divergence: (I) sexual dimorphism, (II) macro-regional differences, (III) climate, (IV) isolation and (V) intraspecific competition. Methods: Multivariate analysis was used to summarize biometric data. Sexual dimorphism and macro-regional divergence were assessed by generalized linear mixed models. Climate, isolation and intraspecific competition effects on phenotype were explored by means of model averaging. Results: Sexes differed in wing shape suggesting a sexual selection pressure on males for aerial displays. Males showed longer bills after controlling for body size. We found an increasing Spain < Morocco < Tunisia trend in body size and bill length and volume. Tunisian populations showed more pointed wings than Moroccan and Iberian ones. Maximum temperature increased bill size as predicted by Allen’s rule. We found support for Bergmann’s rule in relation to temperature in the breeding season and water availability. Intraspecific competition was associated with more rounded wing shapes suggesting a pressure related to breeding display performance. Isolation reduced wingtip pointedness. Conclusion: We found convincing results for wing morphology variation in relation to intrasexual competition, as males seem to be subjected to a sexual selection pressure for aerial display and this adaptation strengthens when intraspecific competition increases. We also found solid support for Allen’s rule, with results suggesting that bill size plays an important role in the bird’s thermoregulation, which does not occur in the case of tarsus. Although Bergmann’s rule is not supported in relation to minimum annual temperature, we found a relationship with thermal conditions in the breeding season, as well as water availability.