Morphological divergence among Spanish Common Crossbill populations and adaptations to different pine species

Crossbills (Loxia spp.) provide a classical avian model of ecological specialization on food resources. Previous studies have suggested that morphometric, genetic and vocal diversification among Common Crossbill Loxia curvirostra populations is better explained by ecological distance (use of different conifers) than by geographical distance, indicating that populations have diverged adaptatively. We tested for adaptive divergence in Iberian crossbills using bill and body size measurements of 6082 crossbills from 27 sites, each consisting of a dominant or single pine (Pinus) of four possible species. Crossbills using different pines differed significantly in body size and bill size and shape. There was no correlation between geographical and morphological distance among sampling sites, consistent with the hypothesis that the morphological divergence of Iberian crossbills is shaped by their ecological differences (foraging on alternative conifers) rather than geographical distance. However, for unknown reasons, Common Crossbills foraging on Pinus sylvestris in Iberia have on average much smaller bills than Parrot Crossbills Loxia pytyopsittacus feeding on the same pine species in northern Europe. The extent to which crossbills specialize on Iberian P. sylvestris remains to be established. Specialization on conifers with overlapping geographical distributions may be facilitated by matching habitat choice of crossbills as a function of their local intake rates.     

Breeding origins and pattern of migration of Bluethroats Luscinia svecica wintering from Iberia to Senegal as revealed by stable isotopes

Capsule: Stable isotope analyses reveal some degree of migratory connectivity of Bluethroat populations wintering from Iberia to West Africa.

Aims: To identify the probable breeding origins of Bluethroats wintering from Iberia to Senegal.

Methods: Bluethroat feathers (P1) were sampled from individuals at their wintering areas. These feathers were then analysed for stable H isotopes (δ²H). We assigned individual Bluethroats to approximate geographic origin using likelihood-based assignment procedures.

Results: We observed spatial segregation between different Bluethroat populations. At wintering sites north of the Sahara Desert, Bluethroats wintering to the west came from further west origins than those which overwintered to the east. Bluethroats from central-eastern Europe overwintered either within the circum-Mediterranean region or in Senegal. We found no clear evidence supporting a sub-Saharan wintering range for birds breeding in Iberia (Luscinia svecica azuricollis subspecies).

Conclusion: North of the Sahara Desert, we found what might be a parallel migration pattern. The apparent lack of Luscinia svecica namnetum Bluethroats in Senegal suggests to some extent some kind of leap-frog migration between some Luscinia svecica cyanecula populations and the L. s. namnetum subspecies.     

Assessing the impact of extreme flooding on survival in a southern European population of White-throated Dippers Cinclus cinclus

Capsule: There were only weak effects of winter flooding episodes on apparent annual survival of a White-throated Dipper breeding population in northern Iberia.

Aims: To test whether extreme winter flooding episodes affected survival in a breeding population of White-throated Dippers Cinclus cinclus.

Methods: Dippers were ringed during the breeding seasons of seven consecutive years on rivers in northern Iberia. Cormack–Jolly–Seber models were used to estimate apparent annual survival in relation to flooding during the winter periods.

Results: We obtained weak evidence for an effect of flooding during the winter on the surveyed population. Two of the six winters were characterized by having an exceptionally high discharge. Our models showed that survival in the subsequent breeding period tended to be lower, although models assuming constant survival were equally well supported.

Conclusion: Extreme flooding in winter may affect survival of some White-throated Dippers in northern Iberia, but its impact at the population level seems to be weak.     

Speckle interferometry applied to pharmacodynamic studies: evaluation of parasite motility

The work reported here describes the application of the optical technique known as dynamic speckle interferometry to evaluate the motility of nematode parasites exposed to different anthelmintic drugs. This technique, a well proven tool for assessing the time evolution of different phenomena, is here successfully used to quantify parasite motility in pharmacodynamic assays. The characterization of the pharmacological properties of anthelmintic drugs is critical to optimize their use in parasite control. Besides, the evaluation of nematode motility is a relevant indicator of the pharmacodynamic effect of anthelmintic drugs. The application of this approach to study the motility of Haemonchus contortus (used as a model of nematode parasites) larvae exposed to different drugs is presented, showing its usefulness.Abbreviations ABZ albendazole - BZD benzimidazole - IVM ivermectin - LVM levamisole     

Optimal sampling design to survey riparian bird populations with low detection probability

ABSTRACT

Capsule: Linear censusing and occupancy models based on fixed sampling points are alternative widely used techniques to determine bird densities in riparian ecosystems, although it cannot be always properly executed.

Aims: The aim is to assess the survey efficiency for river birds using occupancy models in contexts of impaired visibility owing to dense vegetation along the banks.

Methods: We tested whether increasing sampling periods within each survey unit (point) at occupancy models would result in increasing detection probability values. We used two approaches in order to identify the ‘best’ design for White-throated Dippers Cinclus cinclus along forested river stretches: minimizing survey effort of standard single-season site occupancy modelling and exploratory power analysis.

Results: With a detection probability of 0.26 (i.e. much lower than in previous studies), a design with 60 sites surveyed 10 min 6 times a year would be the option to survey White-throated Dippers in forested habitats if an acceptable power is required. Simulations further revealed the consistency of the results.

Conclusion: We provide guidelines to establish a cost-effective survey design for any long-term monitoring citizen-based programme of a White-throated Dipper population when detection probabilities are low. A strength and novelty of the method is to take advantage of advanced probabilistic approaches (e.g. GRTS) to select the survey sites providing, among other major interests, a spatially balanced geographic coverage.     

Foliole movement and canopy architecture of Larrea tridentata (DC.) Cov. in Mexican deserts

Summary The creosote bush (Larrea tridentata) is a common desert perennial with bifoliate, amphistomatic, divaricate leaves. The leaves can vertically close their folioles and vary their profile with respect to direct solar radiation. Field data from different Mexican deserts showed a significant correlation between foliole aperture and mean foliole inclination: in plants in which folioles were more open, the foliole surfaces were less vertical. In a series of field experiments in the Chihuahuan Desert, foliole aperture varied significantly with the water-status of the plant and the hour of the day. In moist plants, folioles opened in the early morning and closed in the afternoon. Water-stressed plants showed significantly lower foliole apertures. A simulation of the light interception patterns of the plants showed that foliole closure in water-stressed individuals reduces direct radiation interception by around 24%. Most (64%) of the reduction in interception was due to the vertical inclination of the photosynthetic surfaces induced by foliole closure in the water-stressed plants. The rest (36%) of the reduction in interception was due to differential self-shading between foliole pairs, which was higher in the closed folioles of the water-stressed plants, but operated more towards the early hours of the day.