Effects of the winter beechmast crop on bird occurrence in British gardens

Capsule Woodland birds were significantly less likely to occur in gardens in years of high beechmast crop.

Aim To test the hypothesis that woodland species that feed on beechmast will have significantly lower occurrence rates at garden feeders in mast years.

Methods Weekly winter occurrence rates at garden feeders between 1970/71 and 1999/2000 for 40 species were analysed in relation to annual beechmast abundance, classified into low, medium and high years. A repeated-measures logistic regression model was used to assess whether beechmast abundance explained further significant variation additional to underlying seasonal and annual trends.

Results Seven species that commonly feed on beechmast showed significantly lower occurrence in gardens in years of highest beechmast abundance: Great Spotted Woodpecker Dendrocopos major, Woodpigeon Columba palumbus, Great Tit Parus major, Coal Tit Periparus ater, Nuthatch Sitta europaea, Jay Garrulus glandarius and Chaffinch Fringilla coelebs. Blackbird Turdus merula and Siskin Carduelis spinus, which showed similar significant patterns, are likely to take beechmast as elements of their diet. Pied Wagtail Motacilla alba was the only insectivorous species to show significant effects, but occurrence was lowest in years of intermediate beechmast abundance. For the latter species, this may have been due to confounding effects of temperature, but there were no such confounding effects of either temperature, or the number of bird feeders provided in gardens, for the other nine species.

Conclusion Use of artificial food sources by birds in gardens is influenced by resources in the surrounding countryside, suggesting that food provided in gardens may play a significant part in the population dynamics of these species, that population monitoring without consideration of the garden habitat may be deficient, and that volunteer-based garden bird recording may provide data that can be used as an indicator of changes in the wider countryside.     

Isolation and characterization of microsatellite loci in the threatened wild toad lily Tricyrtis flava (Liliaceae)

Twelve polymorphic microsatellite loci were isolated and characterized from the threatened toad lily Tricyrtis flava. The number of alleles ranged from three to 17, and the observed and expected heterozygosities ranged from 0.35 to 0.96 and from 0.50 to 0.93, respectively, in a population of T. flava. We also tested cross‐species amplifications of the markers in three other species of Trycyrtis sect. Flavae. Most of 12 markers developed for T. flava were successfully amplified in the species of sect. Flavae and will be useful for population genetic studies of these species.     

Bird predation selects for wing shape and coloration in a damselfly

Wing shape is related to flight performance, which is expected to be under selection for improving flight behaviours such as predator avoidance. Moreover, wing conspicuousness, usually involved in sexual selection processes, is also relevant in terms of predation risk. In this study, we examined how predation by a passerine bird, the white wagtail Motacilla alba, selects wing shape and wing colour patch size in males of the banded demoiselle Calopteryx splendens. The wing colour patch is intra‐ and intersexually selected in the study species. In a field study, we compared wings of live damselflies to wings of predated damselflies which are always discarded after predation. Based on aerodynamic theory and a previous study on wing shape of territorial tactics in damselflies, we predicted an overall short and broad wing, with a concave front margin shape to be selected by predation. This shape would be expected to improve escaping ability. Moreover, we predicted that wing patch size should be negatively selected by predation. We found that selection operated differently on fore‐ and hindwings. In contrast to our predictions, predation favoured a slender general forewing shape. However, the predicted wing shape was favoured in hindwings. We also found selection favouring a narrower wing colour patch. Our results suggest different roles of fore‐ and hindwings in flight, as previously suggested for Calopteryx damselflies and shown for butterflies and moths. Forewings would be more involved in sustained flight and hindwings in flight manoeuvrability. Our results differ somehow from a recently published work in the same study system, but using another population, suggesting that selection can fluctuate across space, despite the simplicity of this predator–prey system.     

The importance of key marginal habitat features for birds in farmland: an assessment of habitat preferences of Red-backed Shrikes Lanius collurio in the Italian Alps

Capsule Key marginal habitat features maintain their importance even when they occur at very low density.

Aims To assess the importance for breeding birds of key habitat elements, such as isolated shrubs, hedgerows and untilled vegetation patches.

Methods We investigated the habitat preferences of Red-backed Shrikes Lanius collurio in an agricultural environment where key habitat elements have been dramatically reduced. Based upon data from territorial maps, a fine-scale model of habitat preference was developed and the results of three different analytical approaches (binary logistic regression, multimodel inference and hierarchical partitioning) were compared.

Results The occurrence of Red-backed Shrikes was positively influenced by the extent of non-grazed/mown grassland, isolated bushes and hedgerows, and negatively influenced by woodland cover. The model highlighted the importance of bushes/hedgerows despite their very scarce occurrence in the study areas (overall, average cover only 7.94%). Breeding densities were rather low, but mean densities were slightly higher in pasture zones in which bushes/hedgerows availability was higher than elsewhere.

Conclusion These results confirm the crucial importance of these key marginal elements even in depauperated farmland landscapes. Maintaining and increasing their availability is a key management option for the encouragement of breeding Red-backed Shrikes, and potentially for other species which are also declining in these farmland habitats.     

Factors determining the occupation of Marsh Harrier Circus aeruginosus breeding grounds in a Mediterranean environment

Capsule Wetland occupation by breeding Marsh Harriers is influenced by wetland and vegetation area, distance to other wetlands where conspecifics are present and also by the characteristics and conditions of the vegetation such as predominant species and its height at the start of the breeding period.

Aims To determine factors influencing the probability of wetland occupation by Marsh Harrier in relation to wetland dimensions, vegetation and hydric conditions, and to determine the effect of the predominant helophyte species in the wetlands and its physical characteristics.

Methods Three hundred and thirty-two wetlands were monitored during a breeding season in NW Spain, a Mediterranean area that hosts 10% of the total number of breeding pairs of Marsh Harriers in Spain. The probability of wetland occupation for breeding in terms of wetland size and proximity, vegetation characteristics, human disturbance and also hydrological variables, was analysed using logistic regression.

Results One hundred and sixty-five pairs were located in 131 wetlands. Variables affecting occupation include vegetation composition and characteristics, wetland dimensions and distance to other occupied wetlands. Wetlands with the highest probability of being occupied were larger, with greater areas of marsh vegetation, taller vegetation, rush and reed communities as the predominant species and which were closer to another wetland occupied by Marsh Harriers.

Conclusions The dimensions and predominant species of helophyte vegetation, and size and location determine the occupation of wetlands as breeding grounds by Marsh Harrier. Changes in the natural supply of water and nutrients due to the implementation of intensive irrigation farming are likely modifying flora in wetlands and affecting the distribution and population size of Marsh Harriers in this region of Spain.     

Within-species variation among populations of the Carex flava complex as a function of habitat conditions

Background: Variable habitat conditions contribute to morphological variability that plays a substantial part in evolution of plants. Understanding the extent of phenotypic plasticity has important implication for assigning individuals to taxa.

Aims: I analysed morphological variability among populations within species of the Carex flava group and tested to what extent morphological variability was associated with habitat conditions.

Methods: A total of 571 specimens from 20 populations of four species from the C. flava complex were sampled in Poland and tested by Discriminant Function Analysis (DFA). The relationship between morphological characters and habitat factors was explored by means of the redundancy analysis (RDA).

Results: Variability of the generative and vegetative traits was fairly similar in Carex lepidocarpa, C. flava and Carex demissa, while it was somewhat higher in Carex viridula. The morphological traits were mostly related to soil organic matter content, calcium and carbonate, as well as to habitat fertility (C:N ratio), elevation and habitat disturbance. The results obtained do not support the separation of C. viridula var. pulchella from C. viridula var. viridula.

Conclusions: Phenotypic variability in the species of the C. flava complex is related to habitat conditions and this can lead to the differentiation of morphotypes within species.     

Close to the edge: predation risks for two declining farmland passerines

Data on the breeding success of two crop-nesting passerines, Skylark Alauda arvensis and Yellow Wagtail Motacilla flava , were collected in relation to linear features within and surrounding arable crops. Both species were found to experience high rates of nest predation with increased proximity to field boundaries, although the exact nature of the relationship differed with species and, in the case of Skylark, with boundary type. Most nest losses were attributable to predation. During 2006 video cameras deployed on Skylark nests showed that all recorded predation was by mammals of various species, and that these were most active in or around grass margins. The results suggest that further research is needed into ways of minimizing negative impacts of predation on Skylarks. Possible solutions discussed include concentrating Skylark Plots in the field centres away from grass margins and promoting Skylark Plots in fields without grass margins in future agri-environmental schemes.     

四川南充地区白鶺鴒的繁殖习性

2004年2~5月在四川省南充市嘉陵江中上游的河漫滩内对白鶺鴒(Motacilla alba)的繁殖习性进行了研究。结果表明:白鶺鴒2月开始繁殖;雌雄参与筑巢,营巢期7~10 d;主要雌鸟孵卵,孵卵期13~14 d,上午8:00~9:00时孵卵出现一次高峰;窝卵数(5.00±0.52)(n=16)枚,孵化率42.5%;雌雄参与育雏,育雏期15~16 d,下午18:00~19:00时育雏出现一次高峰,日育雏次数(112.9±48.6)(n=17),育雏时间间隔(5.60±5.34)min(n=1 584);雏鸟形态生长曲线呈“S”型。