Search

Contains fulltext : 252382.pdf (Publisher’s version ) (Open Access) Europe’s highest densities of breeding Mallards (Anas platyrhynchos) are found in the Netherlands, but the breeding population there has declined by ~30% since the 1990s. The exact cause of this decline has remained unclear. Here, we used an integrated population model to jointly analyze Mallard population survey, nest survey, duckling survival and band-recovery data. We used this approach to holistically estimate all relevant vital rates, including duckling survival rates for years for which no explicit data were available. Mean vital rate estimates were high for nest success (0.38 ±0.01) and egg hatch rate (0.96 ±0.001), but relatively low for clutch size (8.2 ±0.05) compared to populations in other regions. Estimates for duckling survival rate for the three years for which explicit data were available were low (0.16-0.27) compared to historical observations, but were comparable to rates reported for other regions with declining populations. Finally, mean survival rate was low for ducklings (0.18 ±0.02), but high and stable for adults (0.71 ±0.03). Population growth rate was only affected by variation in duckling survival, but since this is a predominantly latent state variable, this result should be interpreted with caution. However, it does strongly indicate that none of the other vital rates, all of which were supported by data, was able to sufficiently explain the population decline. Together with a comparison with historic vital rates, these findings point to a reduced duckling survival rate as the likely cause of the decline. Candidate drivers of reduced duckling survival are increased predation pressure and reduced food availability, but this requires future study. Integrated population modeling can provide valuable insights into population dynamics even when empirical data for a key parameter are partly missing. Methods We built an Integrated Population Model (IPM) and fitted parameters with four datasets: (1) population survey data, (2) nest survey data, (3) duckling survival data, and (4) annual band-recovery data. Our study area covers the entire country of the Netherlands, as all data were collected as part of national monitoring programs or citizen science projects. We limited our analyses to the years 2003-2020 due to a limited sampling effort in the years before 2003 for most datasets. Population survey data. Breeding bird populations have been monitored in the Netherlands as part of a national Breeding bird Monitoring Program (BMP) starting in 1984 (Boele et al. 2014). BMP is based on intensive territory mapping in fixed study plots carried out by well-trained volunteers and professionals who follow a standardized protocol. Territory mapping is based on a large, and annually constant, number of field visits (5-10 between March and July depending on species) in which all birds with territorial behavior (e.g., pair bond, display, nests) are recorded on maps. Species-specific interpretation criteria are used to determine the number and exact locations of “territories” at the end of the season. The counts of 1990 constitute the index baseline. Index values for the following years are then calculated as the relative difference between that year’s counts and those of the reference year (Sovon 2019). Nest survey data. Nest data for Dutch Mallards were retrieved from the National Nest Record Scheme (Bijlsma et al. 2020). Mallard nests are mainly reported as ‘bycatch’ during nest surveys of grassland-breeding waders. To calculate clutch size and egg hatch rate, incomplete clutches were excluded by using only successfully hatched nests. In total, there were 4415 observations of clutch size with a range of 149-402 nests observed annually. For egg hatch rate per successful clutch, we calculated for each year the total number of eggs laid and the number of eggs hatched in nests where at least one egg had hatched. In total 2383 nest observations were available, with the number of observations ranging between 54 and 282 nests per year. Duckling survival data. We used data for Mallard females with broods collected through a citizen science project to estimate annual duckling survival rates. Contributors to this project were asked to report brood size and brood age on a mobile application specifically developed for this purpose. From 2018 onward, contributors were asked to make repeated observations of the same broods to allow for the calculation of duckling survival. We therefore used data for the years 2018-2020, as only for these years were there enough repeated observations of broods to estimate duckling survival. The final dataset included 2825 observations of 1212 broods distributed over the three years. Adult band-recovery data. Annual survival of post-fledgling birds was estimated using data for Mallards that were banded between 2003 and 2020 and were later recovered and reported dead. In the Netherlands, Mallards are banded mostly in traditional duck decoys (Karelse 1994). Since the year 2000, 20133 Mallards have been banded, of which 1233 were recovered dead (Buijs and Thomson, 2001, van Noordwijk et al. 2003). We only included Mallards that were banded in the breeding season (March-July) to exclude winter migrants that breed in other countries. This dataset included 2615 Mallards, of which 203 were recovered dead. 20 mei 2022

AIM: In many species, density‐dependent effects on reproduction are an important driver of population dynamics. However, it is rarely considered that the direction of density dependence is expected to vary over space and time depending on anti‐predator behaviour and predator community. Aggregation may allow for effective group mobbing against avian nest predators while aggregation may also attract mammalian predators, causing negative density dependence. We aim to quantify spatial variation in the effect of conspecific breeding density on nest survival in a mobbing bird species (Eurasian oystercatcher; Haematopus ostralegus) and identify whether this variation in density dependence can be explained by the predator community. LOCATION: Country‐wide (The Netherlands). METHODS: We integrated reproductive data with breeding territory maps of Eurasian oystercatchers and occupancy maps of avian and mammalian predator species across the Netherlands for a 10‐year period. RESULTS: Spatial variation in the composition of the predator community explained the effects of neighbour density, showing decreasing nest survival when both conspecific density and mammalian dominance increased. Also, heterospecific density (from breeding godwits and lapwing) has an additional effect on the oystercatcher nest survival. Strikingly, this pattern did not extend to mammal‐free island populations. MAIN CONCLUSIONS: Our study provides evidence that both the strength and sign of density dependence can vary spatially within species, implying that it is dangerous to generalize results from a single local population to large‐scale management implications and modelling exercises. The study also suggests that conservation actions that aim to attract breeding birds should be prioritized in areas with fewer mammalian predators, but this idea requires further testing on island populations.

International audience; The GBAR experiment aims to measure the gravitational acceleration of antihydrogen H̅. It will use H̅+ ions formed by the interaction of antiprotons with a dense positronium cloud, which will require about 1010 positrons to produce one H̅+. We present the first results on the positron accumulation, reaching 3.8±0.4×108 e+ collected in 560 s.

Rapid declines in breeding wader populations across the world have prompted the development of a series of conservation tools, many of which are designed to influence productivity. Across western Europe, efforts to reverse population declines are typically limited by high levels of nest and chick predation, and managing this predator impact has been a major research focus in the last two decades. A workshop held at the 2019 International Wader Study Group conference aimed to synthesise current understanding of predator management tools and to use expert knowledge to identify and prioritise important knowledge gaps in this area. Here we review the four predator management tools that were described (predator diversion, exclusion, lethal control and headstarting), together with insights into the potential responses of mammalian predators to these management tools. The expert assessment of important areas for future work highlighted the need to: (1) increase our knowledge of predators and their responses to management interventions; (2) ensure our science connects to policy, practitioners and members of the public; and (3) establish clear and consistent goals for the future of breeding wader populations to inform the development and deployment of these management tools.

Additional file 1. Additional figures and tables.

Physical review letters 126(14), 141802 (2021). doi:10.1103/PhysRevLett.126.141802, Published by APS, College Park, Md.

Greppel-plasdrassen worden gezien als een voor boeren aantrekkelijke en voor vogels effectieve maatregel om een beter leefgebied voor weidevogels in het moderne agrarische landschap te creëren. Maar of ze daadwerkelijk het broedsucces vergroten en er meer kuikens vliegvlug worden, is nog niet aangetoond. In OBN-onderzoek werd dat in 2019 op drie plaatsen in Nederland voor de kievit onderzocht.

Timing of activity can reveal an organism's efforts to optimize foraging either by minimizing energy loss through passive movement or by maximizing energetic gain through foraging. Here, we assess whether signals of either of these strategies are detectable in the timing of activity of daily, local movements by birds. We compare the similarities of timing of movement activity among species using six temporal variables: start of activity relative to sunrise, end of activity relative to sunset, relative speed at midday, number of movement bouts, bout duration and proportion of active daytime hours. We test for the influence of flight mode and foraging habitat on the timing of movement activity across avian guilds. We used 64 570 days of GPS movement data collected between 2002 and 2019 for local (non‐migratory) movements of 991 birds from 49 species, representing 14 orders. Dissimilarity among daily activity patterns was best explained by flight mode. Terrestrial soaring birds began activity later and stopped activity earlier than pelagic soaring or flapping birds. Broad‐scale foraging habitat explained less of the clustering patterns because of divergent timing of active periods of pelagic surface and diving foragers. Among pelagic birds, surface foragers were active throughout all 24 hrs of the day while diving foragers matched their active hours more closely to daylight hours. Pelagic surface foragers also had the greatest daily foraging distances, which was consistent with their daytime activity patterns. This study demonstrates that flight mode and foraging habitat influence temporal patterns of daily movement activity of birds. We thank the Nature Conservancy, the Bailey Wildlife Foundation, the Bluestone Foundation, the Ocean View Foundation, Biodiversity Research Institute, the Maine Outdoor Heritage Fund, the Davis Conservation Foundation and The U.S. Department of Energy (DE‐EE0005362), and the Darwin Initiative (19-026), EDP S.A. ‘Fundação para a Biodiversidade’ and the Portuguese Foundation for Science and Technology (FCT) (DL57/2019/CP 1440/CT 0021), Enterprise St Helena (ESH), Friends of National Zoo Conservation Research Grant Program and Conservation Nation, ConocoPhillips Global Signature Program, Maryland Department of Natural Resources, Cellular Tracking Technologies and Hawk Mountain Sanctuary for providing funding and in-kind support for the GPS data used in our analyses.

Aansluitend op de in eerder onderzoek vastgestelde aantrekkelijkheid van greppelplasdrassen voor weidevogels, is onderzocht of deze plasdrassen ook een effect hebben op de overleving van kievitskuikens tot vliegvlug. In drie weidevogelrijke gebieden (Alblasserwaard, Eemland en Fries/Gronings grensgebied) zijn circa 10 gezinnen met greppel-plasdras en 10 zonder plasdras vergeleken, waarbij per gezin de moeder en één of twee kuikens waren gezenderd. Anders dan verwacht kon geen effect op de overleving van kievitkuikens worden aangetoond. Het voorjaar was koud en droog, de predatiedruk groot, mogelijk is dit van invloed geweest. Opvallend was de overall matige conditie van zowel kuikens als adulte vrouwtjes, hetgeen indiceert dat er voor de kievit een generiek probleem is, waar plasdrassen in de huidige vorm geen verbetering in brengen. Er zijn sterke aanwijzingen dat de greppel-plasdrassen een te geringe invloed op de gewasgroei hadden (te weinig groeionderdrukking) en daarmee onvoldoende habitatverbetering opleveren voor kieviten. Additioneel is verkend of greppel-plasdrassen de emissie van broeikasgasemissies kunnen beperken. Dit blijkt niet of nauwelijks aan de orde te zijn. Op de plasdras zelf mag enige verlaging van emissie worden verwacht, maar op gebiedsniveau niet, omdat plasdrassen slechts op een beperkt deel van weidevogelgebieden betrekking hebben.

Collision of birds with wind turbines is an important negative effect of wind energy generation. Assessments of the potential numbers of bird collisions are required prior to the construction of wind farms. Collision rate models (CRMs) are used as a tool to estimate numbers of collision victims for wind farm initiatives. In the past couple of decades various CRMs have been developed. These models are all based on the theoretical calculation of collision probabilities (theoretical models). In this paper we introduce an empirical model, the Flux Collision Model (FCM), in which actual knowledge of species (group)-specific collision probabilities collected in existing wind farms on land is used to calculate collision rates for planned wind farms. An important quality of the FCM is that it provides a means to use empirical information to assess collision rates in Environmental Impact Assessments (EIAs) for wind farm initiatives. In addition, no detailed information on bird behaviour close to the rotor is needed, as this information is already incorporated in the empirical collision probability. In two case studies, one offshore and one on land, we compare and discuss the use and performance of the empirical FCM and the theoretical SOSS Band model for predicting collision rates of birds at wind farm initiatives. To date, no actual collision rates are known for the offshore situation. Accordingly, in the FCM, collision probabilities derived from wind farms on land were used. Nevertheless, in the offshore case study, the results of the FCM were comparable with those of the SOSS Band model. Basic sensitivity analyses for both the FCM and the SOSS Band model showed that purely theoretically both models are equally sensitive to changes in avoidance rates. However, because lower values for avoidance are applied in the FCM (wind farm avoidance) than in the SOSS Band model (overall avoidance), in practice the effect of realistic variation in avoidance rates on the resulting collision rates is much smaller for the FCM than for the SOSS Band model. Our results show that the FCM provides a valuable addition to the existing suite of (theoretical) CRMs. The predictive value of the theoretical SOSS Band model is constrained by the limited availability of knowledge on species (group)-specific (wind turbine) avoidance rates, which is not the case for the FCM. By contrast, the reliability of the empirical FCM is determined only by variation in the availability and quality of information on species (group)-specific collision probabilities. The choice of which CRM to use (theoretical or empirical) seems not to depend on the location of the wind farm initiative as being offshore or on land, but on the availability and reliability of species (group)-specific information in existing wind farms. The availability of a reliable collision probability supports the use of the FCM, while the availability of information on (overall) avoidance rates in the absence of a species (group)-specific collision probability supports the use of a theoretical CRM like the SOSS Band model. Synthesis and applications. The predictive power of collision rate models relies in the first place on the quality of the input information, and second on the theoretical details of the model calculations. Although the FCM is less dependent on measurements of avoidance rates, an urgent need remains to obtain information on actual collision rates and corresponding collision probabilities as well as avoidance rates in existing wind farms both offshore and on land in order to accurately determine the impact of wind energy on bird populations.

Many plants and invertebrates rely on internal transport by animals for long-distance dispersal. Their dispersal capacity is greatly influenced by interactions with the animal's digestive tract. Omnivorous birds adjust their digestive tract morphology to seasonally variable diets. We performed feeding trials in waterfowl to unravel how changing organ size, in combination with seed size, affects dispersal potential. We subjected captive mallards to mimics of summer (animal-based), winter (plant-based), and intermediate diets, and analyzed gut passage of seeds before and after the treatment (trials 1 and 2). To test the effect of gut morphology on seed digestion, we measured digestive organ size after euthanasia. Three hours before euthanasia, differently sized seeds were fed to test how seed size affects gut passage by determining their relative position in the digestive tract (trial 3). Trials 1 and 2 showed that intact seed passage was lower in the plant-based than in the animal-based diet group. Retention time changed only within groups, decreasing in the animal-based, and increasing in the plant-based diet group. No post-diet differences in organ size were detected, probably due to large between-individual variation within groups. Digestive tract measures did not explain variation in seed survival or retention time. Trial 3 revealed that small seeds pass the digestive tract rapidly, while large seeds are retained longer, particularly in the gizzard. Differential retention in the gizzard, the section where seeds can be destroyed, is likely why larger seeds have a lower probability to pass the digestive tract intact. Our results confirm that rapid, flexible adaptation to diet shifts affects seed digestion in waterfowl, although we could not conclusively relate this to organ size. Large interindividual variation in digestive efficiency between mallards feeding on the same diet may provide opportunities for seed dispersal in the field throughout the annual cycle.