Bruno J. Ens

Bruno J. Ens
Sovon, Dutch Centre for Field Ornithology · Department of Research

Dr.

About

248
Publications
43,961
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
7,191
Citations

Publications

Publications (248)
Article
Full-text available
To understand the social organization of species, we propose that it is necessary to unify three partial descriptions of social systems based on competition for limiting resources: adaptive distribution theory, life-history theory, and mating systems theory. Here, we illustrate what insights can be gained by applying such a framework to the study o...
Article
Full-text available
1. Climate change encompasses changes in both the means and the extremes of climatic variables, but the population consequences of the latter are intrinsically difficult to study. 2. We investigated whether the frequency, magnitude and timing of rare but catastrophic flooding events have changed over time in Europe's largest estuary. Subsequently,...
Article
Full-text available
Animal-borne sensors enable researchers to remotely track animals, their physiological state and body movements. Accelerometers, for example, have been used in several studies to measure body movement, posture, and energy expenditure, although predominantly in marine animals. In many studies, behaviour is often inferred from expert interpretation o...
Article
Full-text available
Field studies of interference competition in free-living animals have relied on natural fluctuations in forager density, which are often confounded with other factors. We therefore experimentally studied interference in the wild, capitalizing on 2 cockle beds in an isolated bay that were exploited by a population of individually marked oystercatche...
Article
Full-text available
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...
Article
Full-text available
Understanding which factors cause populations to decline begins with identifying which parts of the life cycle, and which vital rates, have changed over time. However, in a world where humans are altering the environment both rapidly and in different ways, the demographic causes of decline may also vary over time. Identifying temporal variation in...
Article
Full-text available
To understand the consequences of anthropogenic and environmental changes for wildlife populations, it is important to study how individuals differ in their sensitivity to environmental change, and whether this depends on individual characteristics. An individual’s reproductive performance may provide an integrative, unidimensional proxy of an indi...
Article
Full-text available
Disturbance may impact individual birds and ultimately bird populations. If animals avoid disturbed sites this may prevent them from being disturbed directly but may also negatively impact their movement patterns and energy budgets. Avoidance is, however, challenging to study, as it requires following individuals over large spatial scales in order...
Article
Full-text available
1. Body condition is an important concept in behaviour, evolution and conservation, commonly used as a proxy of an individual’s performance, for example in the assessment of environmental impacts. Although body condition potentially encompasses a wide range of health state dimensions (nutritional, immune or hormonal status), in practice most studie...
Article
Full-text available
Shorebird populations, especially those feeding on shellfish, have strongly declined in recent decades and identifying the drivers of these declines is important for conservation. Changing food stocks are thought to be a key driver of these declines and may also explain why trends have not been uniform across Europe's largest estuary. We therefore...
Article
Full-text available
In many coastal areas, high numbers of recreationists may exceed ecological capacities. Careful monitoring of visitor flows is a first prerequisite for coastal area management. We show how AIS ship data can be translated into interpretable information on recreational boats and investigate whether AIS can provide monitoring information when compared...
Article
Full-text available
Individual variation in disturbance vulnerability (i.e. the likelihood that disturbance negatively affects an individual's fitness) can affect how disturbance impacts animal populations, as even at low disturbance levels some individuals could be severely affected and die. Individual variation in vulnerability can arise due to different responses t...
Article
Invasions of marine species are changing coastal food webs worldwide, impacting on trophic interactions between native species (e.g. predator−prey relationships). Here, the impact of 3 macrozoobenthic invasive species on food web structure and functioning at Balgzand (western Wadden Sea) is quantified by using ecological network analysis (ENA). The...
Article
Full-text available
Spatio-temporal variation in population dynamics of migratory populations is shaped by exposure to different environments during the annual cycle. Hence, exposure to similar environments should translate into synchrony in vital rates. Despite a wide-ranging breeding population, the Baltic/Wadden Sea flyway population of eiders (Somateria m. molliss...
Article
Full-text available
Assessing impacts of disturbance over large areas and long time periods is crucial for nature management, but also challenging since impacts depend on both wildlife responses to disturbance and on the spatiotemporal distribution of disturbance sources. Combined tracking of animals and disturbance sources enables quantification of wildlife responses...
Article
Full-text available
Local biodiversity trends over time are likely to be decoupled from global trends, as local processes may compensate or counteract global change. We analyze 161 long-term biological time series (15–91 years) collected across Europe, using a comprehensive dataset comprising ~6,200 marine, freshwater and terrestrial taxa. We test whether (i) local lo...
Article
Full-text available
Feeding specialization is a common cause of individual variation. Fitness payoffs of specialization vary with environmental conditions, but the underlying behavioral mechanisms are poorly understood. Such mechanistic knowledge, however, is crucial to reliably predict responses of heterogeneous populations to environmental change. We quantified spat...
Article
Full-text available
Anthropogenic disturbance can negatively affect an animal’s energy budget by evoking movement responses. Existing research focuses mainly on immediate displacement as a disturbance effect, since this can be easily observed in the field. However, effects on movement over longer timescales are poorly examined and it is largely unknown if and to what...
Article
In recent decades Oystercatchers have declined rapidly in the Netherlands. As part of the ‘Year of the Oystercatcher’, organized in 2008 to draw attention to the decline and initiate research into its causes, volunteer ringing groups were stimulated to colour-band Oystercatchers throughout the country. Furthermore, a website was developed (www. wad...
Article
Full-text available
Knowing the consequences of disturbance for multiple species and all disturbance sources is crucial to mitigate disturbance impacts in densely populated areas. However, studies that observe the complete disturbance landscape to estimate cumulative costs of disturbance are scarce. Therefore, we quantified responses, frequencies and energetic costs o...
Article
Full-text available
Recruitment and fate of all 1436 mussel and oyster beds of the Dutch Wadden Sea were studied for the period 1999–2013. Cox’s proportional hazard rate model with covariates such as orbital speed, exposure time and bed size and type showed that large, low-lying beds that experience a low orbital speed live longer. Yet the most striking result was tha...
Article
Full-text available
Context Place-based transdisciplinary research involves multiple academic disciplines and non-academic actors. Long-Term Socio-Ecological Research (LTSER) platform is one concept with ~ 80 initiatives globally. Objectives As an exercise in learning through evaluation we audited (1) the siting, construction and maintenance of individual LTSER platf...
Article
Full-text available
1.Changes in the frequency of extreme climatic events (ECEs) can have profound impacts on individual fitness by degrading habitat quality. Organisms may respond to such changes through habitat selection, favouring those areas less affected by ECEs; however, documenting habitat selection in response to ECEs is difficult in the wild due to the rarity...
Article
Full-text available
Background Ring wear and loss may have important consequences for mark-recapture studies that aim to estimate survival trends. Our study quantifies the rates of wear and loss from a long-running colour-ringing project of the Eurasian Oystercatcher (Haematopus ostralegus) in the Netherlands. Methods Our analysis included 8909 colour-ringed oysterca...
Article
Full-text available
The Sentinel satellite fleet of the Copernicus Programme offers new potential to map and monitor plant traits at fine spatial and temporal resolutions. Among these traits, leaf area index (LAI) is a crucial indicator of vegetation growth and an essential variable in biodiversity studies. Numerous studies have shown that the radiative transfer appro...
Article
Full-text available
Migratory connectivity describes linkages between breeding and non-breeding areas. An ongoing challenge is tracking avian species between breeding and non-breeding areas and hence estimating migratory connectivity and seasonal survival. Collaborative color-ringing projects between researchers and citizen scientists provide opportunities for trackin...
Conference Paper
Full-text available
Identifying the main drivers of population decline is challenging in migratory species, as they can be affected at different stages of the annual cycle that are geographically separated. Furthermore, the impact of environmental drivers at overwintering sites may not be directly apparent due to carry- over effects (COEs) to the reproductive season (...
Article
Climate warming challenges animals to advance their timing of reproduction [1], but many animals appear to be unable to advance at the same rate as their food species [2, 3]. As a result, mismatches can arise between the moment of largest food requirements for their offspring and peak food availability [4-6], with important fitness consequences [7]...
Article
Full-text available
Many subtidal predators undertake regular tidal migrations into intertidal areas in order to access abundant prey. One of the most productive habitats in soft bottom intertidal systems is formed by beds of epibenthic bivalves such as blue mussels (Mytilus edulis) and Pacific oysters (Crassostrea gigas). In the Dutch Wadden Sea, these bivalves might...
Article
Full-text available
Molluscivorous shorebirds supposedly developed their present wintering distribution after the last ice age. Currently, molluscivorous shorebirds are abundant on almost all shores of the world, except for those in the Indo-West Pacific (IWP). Long before shorebirds arrived on the scene, molluscan prey in the IWP evolved strong anti-predation traits...
Article
Foraging distributions are thought to be density-dependent, because animals not only select for a high availability and quality of resources, but also avoid conspecific interference. Since these processes are confounded, their relative importance in shaping foraging distributions remains poorly understood. Here we aimed to rank the contribution of...
Article
Full-text available
Phenotypic plasticity is a crucial mechanism for responding to changes in climatic means, yet we know little about its role in responding to extreme climatic events (ECEs). ECEs may lack the reliable cues necessary for phenotypic plasticity to evolve; however, this has not been empirically tested. We investigated whether behavioural plasticity in n...
Article
Full-text available
Arctic amplification, the accelerated climate warming in the polar regions, is causing a more rapid advancement of the onset of spring in the Arctic than in temperate regions. Consequently, the arrival of many migratory birds in the Arctic is thought to become increasingly mismatched with the onset of local spring, consequently reducing individual...
Article
Full-text available
The behavioural rhythms of organisms are thought to be under strong selection, influenced by the rhythmicity of the environment. Such behavioural rhythms are well studied in isolated individuals under laboratory conditions, but free-living individuals have to temporally synchronize their activities with those of others, including potential mates, c...
Article
Full-text available
The behavioural rhythms of organisms are thought to be under strong selection, influenced by the rhythmicity of the environment1-4. Such behavioural rhythms are well studied in isolated individuals under laboratory conditions1,5, but free-living individuals have to temporally synchronize their activities with those of others, including potential ma...
Article
Full-text available
Livestock grazing is often recommended to preclude the development of European salt marshes into a species-poor late-successional stage that is frequently dominated by Sea couch (Elytrigia atherica). It remains unclear, however, how grazing may be optimized for conservation management in order to maintain relatively high levels of biodiversity. To...
Article
Full-text available
Our study investigated how bird species richness and abundance was related to livestock grazing on salt, and brackish marshes, with an emphasis on songbirds, and shorebirds. Survey areas with a high percentage cover of tall vegetation were assumed to have experienced lower livestock grazing intensities than survey areas with a low percentage cover...
Article
Full-text available
On page 516, in the second paragraph of the subsection (b) Half-asymptote constant, and for a reason that it has proved impossible to discover, there is a significant error. The equation: log e half-asymptote constant = −24 77 + 6.307log e body mass + 5.030log e prey mass + 10.594 dummy variable oystercatcher = 1 is completely wrong and, instead, w...
Article
Full-text available
The number of Eiders Somateria mollissima wintering in the Dutch Wadden Sea has declined rapidly during the last two decades. Changes in the available food stocks are assumed to be an important cause of this trend. In order to extend the knowledge of the importance of particular food sources to wintering Eiders, data on distribution of Eiders obtai...
Article
Full-text available
De gaswinning vanaf de locaties Moddergat, Lauwersoog en Vierhuizen kan effecten hebben op het Natura 2000 gebied Waddenzee. Uit voorzorg vindt de winning plaats volgens het ‘Hand aan de kraan’ principe. In dat kader vindt een uitgebreide monitoring plaats van biotische en abiotische parameters, om te controleren of gaswinning vanaf de bovengenoemd...
Article
Full-text available
A comparison of spring migration between three populations of Barnacle Geese Branta leucopsis using GPS satellite transmitters With the help of GPS technology it has recently become possible to track individual birds on migration in great detail. In this study we use GPS satellite transmitters to compare spring migration of three populations of Ba...
Article
Full-text available
In this study we examined the effect of different livestock grazing treatments on breeding bird densities in a salt marsh habitat. To avoid an experiment on the large scale needed to directly measure grazing effects on bird densities, we followed a two-step approach. First, we measured vegetation micro-patterns (mosaic of lower vegetation and talle...