Is the bone tissue of ring-billed gulls breeding in a pollution hotspot in the St. Lawrence River,Canada, impacted by halogenated flame retardant exposure?

Bone metabolism is a tightly regulated process that controls bone remodeling and repair in addition to maintaining circulating calcium and phosphate levels. It has been shown that certain organohalogen contaminants may adversely impact bone tissue metabolism and structure in wildlife species. However, exceedingly few studies have addressed the bone-related effects of organohalogen exposure in birds. The objective of the present study was to investigate the associations between markers of bone metabolism and structural integrity, and concentrations of established and current-use halogenated flame retardants (FRs) in ring-billed gulls (Larus delawarensis) nesting in a known FR hotspot area in the St. Lawrence River (Montreal, Canada). Bone metabolism was assessed using plasma calcium and inorganic phosphate levels, and alkaline phophatase activity, while bone (tarsus; trabecular and cortical sections) structure quality was examined using the percentage of bone tissue comprised in the total bone volume (Bv/Tv) and bone mineral density (BMD). Bv/Tv and BMD of the tarsus tended (not significant) to be positively associated with circulating calcium levels in male ring-billed gulls. Moreover, concentrations of FRs in male bird liver (brominated diphenyl ether (BDE)-154, -183, -201, and -209) and plasma (BDE-209) were negatively correlated with trabecular and cortical BMD of the tarsus. These correlative associations may suggest light demineralization of bone tissue associated with FR exposure in male ring-billed gulls. Present findings provide some evidence that bone (tarsus) metabolism and mineral composition may be impacted in high FR-exposed (mainly to PBDEs) ring-billed gulls breeding in the highly urbanized Montreal region.     

Mercury bioaccumulation and risk to three waterbird foraging guilds is influenced by foraging ecology and breeding stage

We evaluated mercury (Hg) in five waterbird species representing three foraging guilds in San Francisco Bay, CA. Fish-eating birds (Forster's and Caspian terns) had the highest Hg concentrations in thier tissues, but concentrations in an invertebrate-foraging shorebird (black-necked stilt) were also elevated. Foraging habitat was important for Hg exposure as illustrated by within-guild differences, where species more associated with marshes and salt ponds had higher concentrations than those more associated with open-bay and tidal mudflats. Importantly, Hg concentrations increased with time spent in the estuary. Surf scoter concentrations tripled over six months, whereas Forster's terns showed an up to 5-fold increase between estuary arrival and breeding. Breeding waterbirds were at elevated risk of Hg-induced reproductive impairment, particularly Forster's terns, in which 48% of breeding birds were at high risk due to their Hg levels. Our results highlight the importance of habitat and exposure timing, in addition to trophic position, on waterbird Hg bioaccumulation and risk.     

Partitioning of Cd and Pb in the blood of European blackbirds (Turdus merula) from a smelter contaminated site and use for biomonitoring

Blood composition is commonly measured to assess exposure to and effects of metals on birds. In most of passerine species, only small volumes of blood may be sampled safely (<500 μL), which limit the measure of several markers of health status and chemical residues. Here, we documented the partitioning of Cd and Pb in the blood of European Blackbirds Turdus merula in order to propose usable relationships between whole blood concentrations (for which toxicological benchmarks exist) and those measured in the erythrocytes. Sixty-two blackbirds were trapped along a pollution gradient (smelter of Metaleurop Nord, Northern France). Blood was sampled and Cd and Pb concentrations were measured both in whole blood and in the erythrocytes only. Birds coming from the most contaminated sites exhibited high residues for both Cd and Pb. We assessed that 73% and 99% of Cd and Pb, respectively, were associated to erythrocytes. Strong linear relationships, that were not influenced by neither the age nor the sex, were established between whole blood residues and those of erythrocytes for Cd and Pb (adj-R² = 0.78 and 0.93, respectively). Present findings are promising to optimize the use of small blood samples in order to investigate several responses relative to wildlife health status.     

An improved method to study the impact of pesticide sprays on small song birds

Abstract

Four test groups of small songbirds (Zebra Finch, Poephila guttata) were sprayed in a chamber with varying concentrations of fenitrothion. Exposure levels were assessed by monitoring air concentrations, deposits of the active ingredient (AI) on glass plates and droplets/cm² on Kromekote® cards. All indices of exposure were linearly correlated and the mean AI deposit on glass plates for the four groups tested were equivalent to 38, 51, 139 and 255 g/ha or 14%, 18%, 50% and 91% of the highest permissible emitted rate for broadscale forest spraying in Canada. Significant depression in body weights and brain acetylcholinesterase levels were noted only for the highest exposure group. Fenitrothion residues in blood were detectable only at the highest exposure level, and in liver at the two higher levels. Carcass and feather residues were much higher than those in blood and liver, and were detectable at all exposure levels but the residues did not increase linearly with exposure. For one of the spray groups, we were able to compute an equivalent acute oral dose based on matching acetylcholinesterase inhibition.     

Human appropriation of net primary production as determinant of avifauna diversity in Austria

The relationship between land-use induced changes in production ecology and avifauna diversity was analysed using a GIS land cover dataset on a 0.25 km × 0.25 km grid covering Austria's national territory. Considering only aboveground processes, the “human appropriation of net primary production” (HANPP = potential NPP − NPP_t), actual NPP (NPP_act), harvest (NPP_h) and NPP_t (= NPP_act − harvest) were recalculated based on existing datasets. Elevation as well as indicators of land cover heterogeneity and landscape heterogeneity were also considered. Correlation analyses were performed between these potential determinants of avifauna diversity and breeding bird species richness data as well as the percentage of endangered breeding birds included in the Austrian red list. Four spatial scales—0.25 km × 0.25 km, 1 km × 1 km, 4 km × 4 km and 16 × 16 km, were analysed. It was shown that breeding bird species richness was more strongly correlated with production ecological indicators and elevation than with heterogeneity indicators. A residual analysis in which the effect of elevation (a proxy for climate) on species richness and its potential determinants was removed confirmed the importance of the availability of trophic energy (NPP) for bird diversity patterns. The results support the species-energy hypothesis, thus confirming the notion that HANPP could be a useful pressure indicator for biodiversity loss.     

Estimating the complexity of bird song by using capture-recapture approaches from community ecology

Repertoire size, the number of unique song or syllable types in the repertoire, is a widely used measure of song complexity in birds, but it is difficult to calculate this exactly in species with large repertoires. A new method of repertoire size estimation applies species richness estimation procedures from community ecology, but such capture-recapture approaches have not been much tested. Here, we establish standardized sampling schemes and estimation procedures using capture-recapture models for syllable repertoires from 18 bird species, and suggest how these may be used to tackle problems of repertoire estimation. Different models, with different assumptions regarding the heterogeneity of the use of syllable types, performed best for different species with different song organizations. For most species, models assuming heterogeneous probability of occurrence of syllables (so-called detection probability) were selected due to the presence of both rare and frequent syllables. Capture-recapture estimates of syllable repertoire size from our small sample did not differ significantly from previous estimates using larger samples of count data. However, the enumeration of syllables in 15 songs yielded significantly lower estimates than previous reports. Hence, heterogeneity in detection probability of syllables should be addressed when estimating repertoire size. This is neglected using simple enumeration procedures, but is taken into account when repertoire size is estimated by appropriate capture-recapture models adjusted for species-specific song organization characteristics. We suggest that such approaches, in combination with standardized sampling, should be applied in species with potentially large repertoire size. On the other hand, in species with small repertoire size and homogenous syllable usage, enumerations may be satisfactory. Although researchers often use repertoire size as a measure of song complexity, listeners to songs are unlikely to count entire repertoires and they may rely on other cues, such as syllable detection probability.Communicated by A. Cockburn     

A dynamic hydrological Monte Carlo simulation model to inform decision-making at Lake Toolibin,Western Australia

Lake Toolibin, an ephemeral lake in the agricultural zone of Western Australia, is under threat from secondary salinity due to land clearance throughout the catchment. The lake is extensively covered with native vegetation and is a Ramsar listed wetland, being one of the few remaining significant migratory bird habitats in the region. Currently, inflow with salinity greater than 1000 mg/L TDS is diverted from the lake in an effort to protect sensitive lakebed vegetation. However, this conservative threshold compromises the frequency and extent of lake inundation, which is essential for bird breeding. It is speculated that relaxing the threshold to 5000 mg/L may pose negligible additional risk to the condition of lakebed vegetation. To characterise the magnitude of improvement in the provision of bird breeding habitat that might be generated by relaxing the threshold, a dynamic water and salt balance model of the lake was developed and implemented using Monte Carlo simulation. Results from best estimate model inputs indicate that relaxation of the threshold increases the likelihood of satisfying habitat requirements by a factor of 9.7. A second-order Monte Carlo analysis incorporating incertitude generated plausible bounds of [2.6, 37.5] around the best estimate for the relative likelihood of satisfying habitat requirements. Parameter-specific sensitivity analyses suggest the availability of habitat is most sensitive to pan evaporation, lower than expected inflow volume, and higher than expected inflow salt concentration. The characterisation of uncertainty associated with environmental variation and incertitude allows managers to make informed risk-weighted decisions.     

The evolutionary continuum of limb function from early theropods to birds

The bipedal stance and gait of theropod dinosaurs evolved gradually along the lineage leading to birds and at some point(s), flight evolved. How and when did these changes occur? We review the evidence from neontology and palaeontology, including pectoral and pelvic limb functional morphology, fossil footprints/trackways and biomechanical models and simulations. We emphasise that many false dichotomies or categories have been applied to theropod form and function, and sometimes, these impede research progress. For example, dichotomisation of locomotor function into ‘non-avian’ and ‘avian’ modes is only a conceptual crutch; the evidence supports a continuous transition. Simplification of pelvic limb function into cursorial/non-cursorial morphologies or flexed/columnar poses has outlived its utility. For the pectoral limbs, even the classic predatory strike vs. flight wing-stroke distinction and separation of theropods into non-flying and flying—or terrestrial and arboreal—categories may be missing important subtleties. Distinguishing locomotor function between taxa, even with quantitative approaches, will always be fraught with ambiguity, making it difficult to find real differences if that ambiguity is properly acknowledged. There must be an ‘interpretive asymptote’ for reconstructing dinosaur limb function that available methods and evidence cannot overcome. We may be close to that limit, but how far can it be stretched with improved methods and evidence, if at all? The way forward is a combination of techniques that emphasises integration of neontological and palaeontological evidence and quantitative assessment of limb function cautiously applied with validated techniques and sensitivity analysis of unknown variables.