Dark tree cavities – a challenge for hole nesting birds?

Holes provide the safest nest sites for birds, but they are an underutilized resource; in natural forests there are usually more holes than birds that could use them. Some bird species could be prevented from nesting in holes because of their inability to operate in the low light conditions which occur in cavities. As no visual system can operate in complete darkness some nest cavities could be too dark to be useable even by hole‐nesters. Thus, the light conditions within tree cavities could constrain both the evolution of the hole nesting habit, and the nest site choice of the hole‐nesting birds. These ideas cannot be tested because little is known about the light conditions in cavities. We took an opportunity provided by ongoing studies of marsh tits Poecile palustris and great tits Parus major breeding in a primeval forest (Bia?owie?a National Park, Poland) to measure illumination inside their nest cavities. We measured illuminance in cavities at daybreak, which is just after the parents commenced feeding nestlings. Only ca 1% of incoming light reached the level of the nest. Illuminance at nests of both species (median = 0.1–0.2 lx) fell within mesopic‐scotopic range, where colour vision is impaired. Measurements in model cavities showed strong declines in illumination with distance from the entrance, with light levels typically as low as 0.01 lx at 40 cm from the cavity entrance. Thus cavities can be very dark, often too dark for the use of colour vision, and we suggest that ‘lighting’ requirements can affect the adoption of specific nest sites by hole nesting birds. We discuss implications of the findings for understanding the adaptations for hole‐breeding in birds.     

Nest and foraging‐site selection in Yellowhammers Emberiza citrinella: implications for chick provisioning

Capsule Vegetation structure and invertebrate abundance interact to influence both foraging sites and nestling provisioning rate; when invertebrate availability is low, adults may take greater risks to provide food for their young.

Aims To investigate nesting and foraging ecology in a declining farmland bird whose fledging success is influenced by the availability of invertebrate prey suitable for feeding to offspring, and where perceived predation risk during foraging can be mediated by vegetation structure.

Methods Provisioning rates of adult Yellowhammers feeding nestlings were measured at nests on arable farmland. Foraging sites were compared with control sites of both the same and different microhabitats; provisioning rate was related to habitat features of foraging‐sites.

Results Foraging sites had low vegetation density, probably enhancing detection of predators, or high invertebrate abundance at high vegetation density. Parental provisioning rate decreased with increasing vegetation cover at foraging sites with high invertebrate abundance; conversely, where invertebrate abundance was low, provisioning rate increased with increasing vegetation cover.

Conclusions Vegetation structure at foraging sites suggests that a trade‐off between predator detection and prey availability influences foraging site selection in Yellowhammers. Associations between parental provisioning rate and vegetation variables suggest that where invertebrate abundance is high birds increase time spent scanning for predators at higher vegetation densities; however, when prey are scarce, adults may take more risks to provide food for their young.     

Black or white? Physiological implications of roost colour and choice in a microbat

Although roost choice in bats has been studied previously, little is known about how opposing roost colours affect the expression of torpor quantitatively. We quantified roost selection and thermoregulation in a captive Australian insectivorous bat, Nyctophilus gouldi (n=12) in winter when roosting in black and white coloured boxes using temperature-telemetry. We quantified how roost choice influences torpor expression when food was provided ad libitum or restricted in bats housed together in an outdoor aviary exposed to natural fluctuations of ambient temperature. Black box temperatures averaged 5.1 °C (maximum 7.5 °C) warmer than white boxes at their maximum daytime temperature. Bats fed ad libitum chose black boxes on most nights (92.9%) and on 100% of nights when food-restricted. All bats used torpor on all study days. However, bats fed ad libitum and roosting in black boxes used shorter torpor and spent more time normothermic/active at night than food-restricted bats and bats roosting in white boxes. Bats roosting in black boxes also rewarmed passively more often and to a higher skin temperature than those in white boxes. Our study suggests that N. gouldi fed ad libitum select warmer roosts in order to passively rewarm to a higher skin temperature and thus save energy required for active midday rewarming as well as to maintain a normothermic body temperature for longer periods at night. This study shows that colour should be considered when deploying bat boxes; black boxes are preferable for those bats that use passive rewarming, even in winter when food availability is reduced.     

Potential for marker-assisted selection for forest tree breeding: lessons from 20 years of MAS in crops

For the most part, molecular markers and detection of quantitative trait loci have been developed for forest tree species in view to performing marker-assisted selection (MAS). However, MAS has not been applied to forest trees until now. In parallel, some success stories of MAS in crop breeding have been reported. Recently, genotyping techniques have undergone a tremendous increase in throughput, moving the trend from MAS to genomic selection. We analyzed 250 papers reporting the use of MAS in plant breeding and found that the most popular schemes used were gene pyramiding and marker-assisted backcross manipulating a single or very few genomic regions which have a major impact on crop value. We reviewed theoretical and simulation studies to identify the parametric space in which MAS is expected to bring about significant advantages over phenotypic selection. Then, we tried to explain why MAS has not been applied to forest trees and discuss the opportunities offered by recent advances in these species.     

Dissection of complex traits in forest trees — opportunities for marker-assisted selection

Due to their long reproductive cycles and the time to expression of mature traits, marker-assisted selection is particularly attractive for tree breeding. In this review, we discuss different approaches used for developing markers and propose a method for application of markers in low linkage disequilibrium (LD) populations. Identification of useful markers for application in tree breeding is mainly based on two approaches, quantitative trait locus (QTL) mapping and association genetic studies. While several studies have identified significant markers, effect of the individual markers is low making it difficult to utilize them in breeding programs. Recently, genomic selection (GS) was proposed for overcoming some of these difficulties. In GS, high density markers are used for predicting phenotypes from genotypes. Currently small effective populations with high LD are being tested for GS in tree breeding. For wider application, GS needs to be applied in low LD populations which are found in many tree breeding programs. Here we propose an approach in which the significant markers from association studies may be used for developing prediction models in low LD populations using the same methods as in GS. Preliminary analyses indicate that a modest numbers of markers may be sufficient for developing prediction models in low LD populations. GS based on large numbers of random markers or small numbers of associated markers is poised to make marker-assisted selection a reality in forest tree breeding.     

Are there body size implications for the success of globally introduced land birds?

Verbal models have hypothesized a relation between body size and the successful introduction of animal species. This relation is largely based on studies of intrinsic rate of increase in what have been termed "colonizing" species. From these studies it has been predicted that introduction success should be negatively correlated with body size across taxa but positively correlated within closely related taxa. T examine this relation for globally introduced land birds. Introduced land birds are. on average, larger bodied than extant land bird species. Across species, families, and higher family nodes, global introduction success is significantly related to decreasing body size. However, within taxa there is a significant positive relationship between introduction success and body size. I discuss possible explanations for the observed relations and conclude that an indirect but genuine relationship between the introduction success of land birds and their body size is currently the most plausible.     

Leaf defoliation of tropical dry forest tree seedlings – implications for survival and growth

 The effect of herbivory on survival and growth of seedlings of four species, Cedrela odorata, Hymenaea courbaril, Manilkara chicle and Swietenia macrophylla, was studied in secondary dry forests in Guanacaste, Costa Rica. Potted seedlings were planted at two sites in a 2×2 factorial design, combining thinning to increase light levels at the forest floor, and trenching to reduce root competition around the planted seedlings. C. odorata and S. macrophylla were repeatedly severely defoliated by insects, while H. courbaril became less affected. M. chicle did not show any significant signs of defoliation and was not further analysed. Defoliation levels were generally higher in both thinned and trenched treatments, and also positively correlated with larger initial seedlings sizes. Decreased growth rates caused by defoliation were seen in S. macrophylla and C. odorata in the growing season. Defoliation of more than 50% in combination with abiotic factors, particularly drought, were sufficient to contribute to retarded seedling development and increased seedling mortality of C. odorata and S. macrophylla. Received: 10 April 1997 / Accepted: 26 June 1998     

Distribution of environmental performance in life cycle assessments—implications for environmental benchmarking

The International Journal of Life Cycle Assessment - Life cycle assessment (LCA) is considered a robust method to analyse the environmental impacts of products and is used in public and private...     

Determinants of tree species preference for foraging by insectivorous birds in a novel Prosopis–Leucaena woodland in Puerto Rico: the role of foliage palatability

The foliage palatability hypothesis predicts that avian insectivores will preferentially forage in tree species with the greatest abundance of their arthropod prey, which in turn are associated with the tree’s foliage nutrition and palatability. We tested this hypothesis in a novel Prosopis–Leucaena woodland in Puerto Rico by determining foraging preferences of five insectivorous bird species for six tree species (five alien, one native) and relating preferences to foliage arthropod biomass and leaf chemistry. The most frequently preferred tree species for foraging were the alien Prosopis juliflora (preferred by five bird species) and Pithecellobium dulce (preferred by four bird species). Both species had high foliage arthropod biomass, high N content, low lignin/N ratios, and low hemicellulose content. Compounds, previously known to affect herbivore responses to Albizia lebbeck and Leucaena leucocephala, may explain low arthropod biomass despite high N content in Albizia and avoidance of Leucaena by four bird species despite its high arthropod biomass. The native Bucida buceras had tough leaves with low N content, low arthropod biomass, and only one bird species showed a weak preference for foraging in it. Biomass of predaceous arthropods showed strong negative correlations with the ratios of lignin/N and hemicellulose/N. Some alien tree species had highly palatable foliage with high arthropod biomass and hence were preferred for foraging by avian insectivores as predicted by the foliage palatability hypothesis. High foliage palatability of some alien tree species may weaken the effect of enemy release in some novel plant communities.     

Sexual selection in an anadromous population of threespine sticklebacks — no role for parasites

Summary We examined the hypothesis that trematode parasites played a role in the evolution of the red colour of male threespine sticklebacks (Gasterosteus aculeatus L.) and whether the parasites affected female fitness. Parasites (blackspot disease) played no role either in determining the outcome of male—male competition for breeding territories or in female mate choice. Among males with territories, mating success was highly variable. Some males obtained over 3000 eggs (approximately 10 matings) whereas others received none. In 1 year of the 2 year study, males with the greatest amount of red nuptial coloration had the greatest mating success. Although male colour may sometimes affect female choice in this system, this preference has probably not evolved because of the Hamilton—Zuk mechanism of sexual selection. The parasites had small, but statistically significant effects on female fitness. Females with high parasite loads were in poorer condition and produced fewer eggs than less parasitized fish.     

Locomotion in degus on terrestrial substrates varying in orientation – implications for biomechanical constraints and gait selection

To gain new insights into running gaits on sloped terrestrial substrates, metric and selected kinematic parameters of the common degu (Octodon degus) were examined. Individuals were filmed at their maximum voluntary running speed using a high-speed camera placed laterally to the terrestrial substrate varying in orientations from −30° to +30°, at 10° increments. Degus used trotting, lateral-sequence (LS) and diagonal-sequence (DS) running gaits at all substrate orientations. Trotting was observed across the whole speed range whereas DS running gaits occurred at significantly higher speeds than LS running gaits. Metric and kinematic changes on sloped substrates in degus paralleled those noted for most other mammals. However, the timing of metric and kinematic locomotor adjustments differed significantly between individual degus. In addition, most of these adjustments took place at 10° rather than 30° inclines and declines, indicating significant biomechanical demands even on slightly sloped terrestrial substrates. The results of this study suggest that DS and LS running gaits may represent an advantage in small to medium-sized mammals for counteracting some level of locomotor instability. Finally, changes in locomotor parameters of the forelimbs rather than the hindlimbs seem to play an important role in gait selection in small to medium-sized mammals.     

Specificity of membrane specializations in mechanoreceptors of birds—A freeze-etching study

The detailed knowledge of the molecular process of mechanotransduction is still an unsolved question. The investigation of the intramembranous structure of the cutaneous mechanoreceptors may play an important role in elucidating this problem. In this relation, Herbst sensory corpuscles in ducks were studied for the first time using the freeze-etching and thin sectioning techniques. Herbst corpuscles have the basic structural components valid for most of the encapsulated mechanoreceptors in mammals: a capsule made of perineural cells, a lamellar complex of modified Schwann cells, surrounding the non-myelinated part of the receptor nerve fiber and its ending. Freeze-etching replicas reveal that the plasmalemmae of the capsule cells, modified Schwann cells and axolemmae of parts of the nerve fiber differ in both density and pattern of distribution of intramembranous particles (IMPs) as well as IMP size. On all the plasmalemmae the IMP density is higher on the P-face (2000–3300?µm^?2) than the respective E-face (800–1500?µm^?2). The axolemma of the ending of the receptor nerve fiber expresses higher density of IMPs than its shaft. The mean IMP size for all the plasmalemmae varies between 5.5 and 7.5?nm. Many tight junctions occur between the capsule cells. These results indicate that the non-myelinated axolemma as well as the plasmalemmae of other components of Herbst corpuscles are specialized in terms of content and distribution of IMPs. The IMPs may represent various kinds of mechanosensitive channel proteins or related membrane-bound proteins participating in the process of mechanotransduction.     

The population status of Capercaillie Tetrao urogallus in Scotland during winter 2015–16

Capsule: The population size of Western Capercaillie Tetrao urogallus in Scotland was estimated at 1114 individuals with 95% confidence intervals (CIs) of 805–1505.

Aim: To produce an updated estimate of Capercaillie population size in Scotland, with improved precision from, but retaining comparability with, previous surveys.

Methods: A random sample of 2?km long line transects was surveyed throughout the current range of the Capercaillie, during winter 2015–16, with sampling in three separate strata. Multi-covariate distance sampling was used to fit detection functions to the Capercaillie data, deriving national, regional and sex-specific estimates of density and abundance.

Results: Across 741 transects, 136 Capercaillie were recorded in 120 separate encounters, giving rise to a population estimate of 1114 individuals (95% CIs: 805–1505). This estimate is 13% lower than that from the previous survey in 2009–10 but the difference is not statistically significant. Most of the population (83%) was estimated to occur in Strathspey, with much smaller numbers in the rest of the range.

Conclusion: The Capercaillie population in Scotland remains at a critically low level. Further evidence of decline in edge of range subpopulations raises serious concern over the viability of Capercaillie in these areas, whereas numbers appear stable in the core of the range in Strathspey. The use of a revised survey design, with greater sampling in the core of the range, improved estimate precision.     

Dates of first arrival and song of birds during 1974–99 in mid-Deeside,Scotland

We studied the wing-length and body mass of the two populations of Reed Warblers (summer breeders and transients), and that of the resident Clamorous Reed Warbler, which exist in Israel. We found that, in all three groups, wing-length increases significantly with age for several years. Body mass also increased slightly (but significantly) with age. These differences were not caused by differential survival of juveniles, but appear to be a general phenomenon, possibly related to better nutrition of the adults. The autumn migration of transient Reed Warblers lasted from August until November, but no adults were captured during October and November, while 29.3% of the first-year birds were captured during these months. This suggests that adults can afford to start migration earlier, perhaps due to their greater experience.     

Nest‐site selection and breeding ecology of Sky Larks Alauda arvensis in Hungarian farmland

Capsule Nesting Sky Larks avoided arable fields and the vicinity of farm buildings, and preferred extensive and heterogeneous grassland, where nest success was 30%.     

Factors promoting polygyny in European birds of prey—a hypothesis

Summary Polygyny is known in at least nine (out of 36) European raptor (Accipitriformes and Falconiformes) and seven (out of 13) owl (Strigiformes) species that hunt mobile prey. The hypothesis put forward here suggests that abundant food supply and nomadic tactics of breeding dispersal are crucial factors promoting polygyny in birds of prey. The hypothesis predicts that: (1) polygyny is more common in rodent-eating birds of prey than in bird-eating ones; (2) polygyny is more frequent in good vole years than in poor ones; (3) the frequency of polygyny in vole-eating species should increase northwards in Europe, as the densities of voles in the peak phase increase in that direction; (4) the frequency of polygyny and harem size should be increased by supplementary feeding; and (5) polygyny is more common in nomadic birds of prey with annual pair bonds and weak territoriality than in resident birds of prey with longerterm pair bonds and stronger territoriality. A majority of the available data is consistent with predictions 1–3 and 5, but data on prediction 4 are scanty. Further studies on ringed birds of prey are needed to test the validity of the hypothesis.     

Oviposition site selection of a threatened moth <Emphasis Type="Italic">Eriogaster catax</Emphasis> (Lepidoptera: Lasiocampidae) in agricultural landscape—implications for its conservation

Shrubby field margins and hedgerows play an important role for many species of flora and fauna in agro-ecosystems, including those which are rare or endangered. A characteristic species of these semi-natural habitats in agricultural landscape is the Eastern eggar, Eriogaster catax (Linnaeus, 1758): a moth species threatened in many European countries. In this study we investigated the oviposition preferences of E. catax at host plant level in agricultural landscape in south-western Poland, near of the northern limit of the species distribution in Europe. In total we surveyed 796 host plants. Altogether we found 439 eggs batches or caterpillar webs of E. catax on 373 occupied plants. Most of them (92.3%) were on blackthorn Prunus spinosa, which was preferred host plant next to pear Pyrus spp. However, the most important predictor of the presence of egg batches were microclimatic conditions. We recorded that females preferred host plants exposed to direct sunlight and with south and west-facing slopes for oviposition and avoided those inside of the dense shrub canopy. Eggs were laid more often on the trunk and on the upper half of the host plant, however there was a significant difference in vertical and horizontal position of egg batches in relation to the position of the plant. Inside of the shrub canopy, eggs were laid in higher parts of host plant and closer to the trunk, than at the edge and on solitary plants. Based on our observations the management strategies for the habitats of the species are proposed and discussed.