Topic
Branta
About: Branta is a research topic. Over the lifetime, 647 publications have been published within this topic receiving 14794 citations.
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Papers
TL;DR: It is proposed that declining forage quality (due to changing vegetation composition during succession) is a better explanation for this pattern than the classic explanation of predator control of herbivores at high levels of primary productivity.
Abstract: 1 The relationships between soil development, vertical vegetation zonation, vegetation succession and herbivory by Brent geese, Branta bernicla, were studied in a coastal salt marsh. We were able to analyse up to 100 years of salt marsh development by comparing sites where vegetation succession had progressed for-various periods of time. These data were related to a continuous daily record of high water levels measured since 1824. 2 Most elevational variation in edaphic conditions (and therefore vertical vegetation zonation) could be attributed to variation in height of the sandy subsoil, as rapid dune formation occurs on the beaches early in succession. In the intermediate part of this elevational gradient, the maximum annual increase of 1.2 mm of silt corresponded to an annual increase of 5.6 g N m(-2) in the topsoil (0-50 cm). The average sea level rise in this area over the last 170 years was 0.63 mm year(-1). A sedimentation model suggests that this has had strong effects on sedimentation and the annual inundation frequency in the mid-part of the elevational gradient, thus affecting vegetation zonation on the salt marsh. For the major part of the investigated transects, sea level rise has probably speeded up succession due to an increased rate of sedimentation. 3 The occurrence and dominance of all plant species were recorded in 3927 plots, and and for the 11 most common species response surfaces were calculated for their dependence on elevation and transect age. Most plant species were clearly separated along these axes. Most halophytic species, which were preferred by the geese, occurred early in succession and low on the gradient, where we observed the highest densities ge quality of Festuca I rubra increased towards the lower salt marsh. Other preferred forage species (Puccinellia maritima and Plantago maritima) were gradually displaced during succession by the tall grass Elymus athericus, especially in the mid-and upper salt marsh. Few geese grazed in areas where Elymus was dominant. 4 Herbivores first increased in numbers but then declined along a gradient of primary productivity. We propose that declining forage quality (due to changing vegetation composition during succession) is a better explanation for this pattern than the classic explanation of predator control of herbivores at high levels of primary productivity. This quality threshold hypothesis, as an alternative explanation of the exploitation ecosystem hypothesis, is expected to hold especially where smaller (quality-sensitive) herbivores such as geese are present. 5 Grazing by cattle in a 200-year-old part of the salt marsh led to the disappearance of Elymus athericus, to establishment of early successional halophytes and a return of Brent geese. Crazing by a larger herbivore therefore facilitated conditions for smaller herbivores by preventing the dominance of plant species that were good light competitors, and thus improved forage quality. Populations of these small herbivores could then become regulated by predators, although none was present at our site.
314 citations
TL;DR: Measurements of changes in body mass of incubating female Brent Geese, coupled to estimated flying costs showed that body reserves stored in the Wadden Sea were insufficient to accomplish both migration and successful breeding.
Abstract: Seasonal changes in body mass of Arctic-nesting Brent Geese are characterized by a depression in early April, followed by a sharp increase during pre-migratory fattening. Both male and female Brent Geese increased their body mass by 25-35% in the Wadden Sea in April/May. Paired females reach on average higher body masses than single females. Female Brent Geese that returned with offspring to the wintering quarters in western Europe had on average been heavier at spring departure from the staging grounds in the Wadden Sea, than those failing to raise offspring. This difference remained significant after correcting for body size (i.e. wing length). In males, corrected spring body mass had no effect on subsequent breeding success. Measurements of changes in body mass of incubating female Brent Geese, coupled to estimated flying costs (based on data on body mass, wing span and total wing area) showed that body reserves stored in the Wadden Sea were insufficient to accomplish both migration and successful breeding. Presumably the geese refuelled in the White Sea, in order to complete their spring migration and arrive on the breeding grounds in Taymyr in the condition necessary for successful breeding.
245 citations
TL;DR: It is concluded that long-distance dispersal events are likely to be rare and that northbound dispersal by endozoochory can only occur during spring if waterbirds feed on seeds that have not been depleted and remained frozen down or buried in sediments, or during moult- or post-moult migrations.
Abstract: We review whether migratory Anatidae, i.e., swans, geese and ducks, could be acting as vectors for dispersal of Zostera, Ruppia and Potamogeton propagules by endozoochory (carrying seeds in their guts). We list six prerequisites that must all be fulfilled, if successful dispersal should occur. Several Anatidae species feed on these macrophytes, and undertake rapid long-distance movements, making dispersal possible. We identify four problems, which in combination leads us to conclude that long-distance dispersal events are likely to be rare. (i) Most long-distance movements are out of phase with the reproductive efforts of the plants, and if birds arrive at sites when plants still bear seeds, they are likely to depart well after seed stocks have been depleted. (ii) Seed transport by birds will usually be uni-directional, from north to south on autumn migrations. (iii) Most of the gut contents of migratory birds are likely to have been discarded within 300 km of departure. (iv) In many cases, birds will arrive in habitats seriously different from those they departed, i.e., any seeds carried along will have low chances of surviving in their new site. We suggest that northbound dispersal by endozoochory can only occur during spring if waterbirds feed on seeds that have not been depleted and remained frozen down or buried in sediments, or during moult- or post-moult migrations. Moult migration takes place in summer in phase with the reproductive efforts of the plants. Also epizoochorous dispersal (external attachment) is subject to restrictions i, ii and iv.
187 citations
TL;DR: The efficacy of population management, disturbance, provision of alternative feeding areas, compensation and large‐scale stakeholder involvement and co‐management as options for resolving conflict based on the existing literature are reviewed and a framework of management advice for the future is presented.
Abstract: Swans, geese and some ducks (Anatidae) are obligate herbivores, many are important quarry species and all contribute to a variety of ecosystem services. Population growth and shifting ranges have led to increasing proximity to man and thus increasing conflicts. We review and synthesize the role of these birds as herbivores on agricultural land (cropland, rotational grassland and pasture) and other terrestrial habitats where conflict with human interests may occur. A bibliographic analysis of peer-reviewed papers (N = 359) shows that publication activity peaked in 1991-2000 in North America and 2000-2010 in Europe, and has decreased since. Taxonomic and geographical biases are obvious in research to date: Snow Goose Chen caerulescens was the most studied species (N = 98), and Canada Branta canadensis, Barnacle B. leucopsis and Brent geese B. bernicla all featured in more than 40 studies; most studies originated in northwest Europe or North America, very few have been carried out in Asia and European Russia. On the basis of nutrient/energy budgets of herbivorous waterfowl, it is evident that dense single-species crops (such as rotational grassland, early-growth cereals and root crops) and spilled grain in agricultural landscapes offer elevated energetic and nutritional intake rates of food of higher quality compared to natural or semi-natural vegetation. Hence, although affected by seasonal nutritional demands, proximity to roost, field size, disturbance levels, access to water, food depletion and snow cover, agricultural landscapes tend to offer superior foraging opportunities over natural habitats, creating potential conflict with agriculture. Herbivorous waterfowl select for high protein, soluble carbohydrate and water content, high digestibility as well as low fibre and phenolic compounds, but intake rates from grazing varied with goose body and bill morphology, creating species-specific loci for conflict. Crop damage by trampling and puddling has not been demonstrated convincingly, nor do waterfowl faeces deter grazing stock, but where consumption of crops evidently reduces yields this causes conflict with farmers. Studies show that it is difficult and expensive to assess the precise impacts of waterfowl feeding on yield loss because of other sources of variation. However, less damage has been documented from winter grazing compared to spring grazing and yield loss after spring grazing on grassland appears more pronounced than losses on cereal fields. Although yield losses at national scales are trivial, individual farmers in areas of greatest waterfowl feeding concentrations suffer disproportionately, necessitating improved solutions to conflict. Accordingly, we review the efficacy of population management, disturbance, provision of alternative feeding areas, compensation and large-scale stakeholder involvement and co-management as options for resolving conflict based on the existing literature and present a framework of management advice for the future. We conclude with an assessment of the research needs for the immediate future to inform policy development, improve management of waterfowl populations and reduce conflict with agriculture.
180 citations
TL;DR: In this paper, a K-sample capture-recapture model for an open population of animals, which allows for different identifiable age categories to have different survival and capture probabilities, is developed.
Abstract: A K-sample capture-recapture model for an open population of animals, which allows for different identifiable age categories to have different survival and capture probabilities, is developed. Explicit maximum likelihood estimators of population size and survival rates, together with their asymptotic variances and covariances, are given. A test of whether survival and capture rates are independent of age is shown to be of simple hypergeometric form. An illustrative example based on resighting data of neck-collared giant Canada geese (Branta canadergsis maxima) is presented. The relationship of this model to other capture-recapture and band-recovery models is discussed.
167 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2026 | 2 |
| 2025 | 3 |
| 2024 | 7 |
| 2023 | 8 |
| 2022 | 20 |
| 2021 | 5 |