Home range, territoriality and habitat selection by the Dupont´s Lark Chersophilus duponti during the breeding and postbreeding periods
Published: Volume 52(1), June 2005. Pages 133-146.
Aims: Home ranges, habitat use and selection of Dupont´s Lark Chersophilus duponti during the breeding and postbreeding periods were analysed using radiotagged birds. Location: Layna, central Spain (Soria, 41º05´N, 1º50´W; 1200 m a.s.l.).
Methods: A total of 32 birds were radiotagged (22 males, 4 females and 6 juveniles) and monitored nearly daily from April 1st to September 1st. The following variables were measured (1) home ranges using the Minimum Convex Poligon, MCP, (2) core areas using the kernel 80 % density estimator, (3) the distance between successive daily locations, and (4) the degree of overlap of between individuals and periods in home ranges and core areas using Cole´s Index of Concordance. The use and selection of vegetation formations was studied on an individual basis comparing the percentage of bird locations and random points in each vegetation unit. The selection of habitat structure was measured along transects within the birds´ home ranges and compared to that measured along random transects outside home ranges.
Results: Home ranges (mean, 8.1 ha), core areas (3.7 ha) and the distance between successive daily locations (around 120 m) did not differ between age-sex classes, or between periods in either sex. Juveniles showed larger core areas and movements than adults during the post-breeding period. Overlap between neighbouring males, as well as between juveniles and adults during the postbreeding period, was scarce in comparison with the overlap between members of the same pair or the overlap between the periods. Two males (9.1%) changed their home ranges during the breeding period, and the only fledgling captured near its nest stayed within paternal home range until at least 1 month old. The density in the study area was 1.0 males/10ha. Dupont´s Lark positively selected Genista pumila shrubs and negatively Genista scorpius shrubs, dry pastures and cereal fields. There were no differences between sexes, nor between periods among adults. Selection by juveniles differed from adult selection during the postbreeding period, using dry pastures more frequently than Genista pumila shrubs. Birds positively selected areas of high pillow-shape shrub cover at ground level, avoiding those of high tall-shrub cover at ground level. A binary logistic regression model including only pillow-shaped shrub cover at ground level as explanatory variable, correctly predicted 76% of home ranges, as confirmed by jacknife re-sampling estimation.
Conclusions: Three main conclusions can be drawn from a conservation perspective: (1) the species´ territorial behaviour and strict habitat selection make it highly vulnerable to habitat changes, imposing careful habitat management; (2) management should also regard the marginal habitats used by juveniles; (3) the low density found in one of the best areas for the species in Iberia supports the low estimates of the Spanish population of the Dupont´s Lark made in previous studies.