Poot M.,Bureau Waardenburg |
Fijn R.,Bureau Waardenburg |
Schoten H.,Vogelbescherming Nederland
Limosa | Year: 2016
On 21 February 2011 an aerial survey of Great Crested Grebes was carried out along the coast of Holland to assess how well the thousands of Great Crested Grebes can be counted from the air. The maximum number of grebes known to winter in this area is over 30 000 birds (about 10% of the total Northwest-European population), but variation between years is large. The area is thus far not protected and the species is not well covered in the yearly monitoring program of the Dutch government (mwtl). The count was conducted in a twin-engine airplane without bubble windows. The main survey design consisted of transects of 6 km length perpendicular to the coast in the concentration areas of grebes. Birds were recorded in four distance strips. Grebes are known to dive in response to an approaching, low-flying survey airplane. Consequently, relatively few birds were seen in the first distance band. If this is not taken into account the distance-dependent detection probabilities are overestimated. We present fi ve different estimates of total population size and consider that the best estimate (10 592,95%-C.1.4 510-25125) was achieved with a left truncation of the survey data, excluding the first distance band. Systematic observations of flying grebes from eight migration observation sites showed that the aerial survey was conducted well after the usual midwinter maximum of grebe presence. Furthermore, the winter of 2010/2011 was mild with probably relatively low numbers, possibly explaining why our population estimates were only 25-35% of the maximum number recorded along the Dutch coast.
PubMed | CIFOR, Jardin Botanico Joaquin Antonio Uribe, Red para la Mitigacion y Adaptacion al Cambio Climatico de la UNAD, Herbario Universitario and 63 more.
Type: | Journal: Scientific reports | Year: 2017
Tropical forests are global centres of biodiversity and carbon storage. Many tropical countries aspire to protect forest to fulfil biodiversity and climate mitigation policy targets, but the conservation strategies needed to achieve these two functions depend critically on the tropical forest tree diversity-carbon storage relationship. Assessing this relationship is challenging due to the scarcity of inventories where carbon stocks in aboveground biomass and species identifications have been simultaneously and robustly quantified. Here, we compile a unique pan-tropical dataset of 360 plots located in structurally intact old-growth closed-canopy forest, surveyed using standardised methods, allowing a multi-scale evaluation of diversity-carbon relationships in tropical forests. Diversity-carbon relationships among all plots at 1ha scale across the tropics are absent, and within continents are either weak (Asia) or absent (Amazonia, Africa). A weak positive relationship is detectable within 1ha plots, indicating that diversity effects in tropical forests may be scale dependent. The absence of clear diversity-carbon relationships at scales relevant to conservation planning means that carbon-centred conservation strategies will inevitably miss many high diversity ecosystems. As tropical forests can have any combination of tree diversity and carbon stocks both require explicit consideration when optimising policies to manage tropical carbon and biodiversity.
Nolet B.A.,Netherlands Institute of Ecology |
Gyimesi A.,Bureau Waardenburg
Journal of Ornithology | Year: 2013
Many migratory birds use a chain of stopover sites to fuel their migration. Under time-minimizing migration, fuelling time and giving-up density at stopovers are predicted to depend on fuelling conditions. Fluctuations in food accessibility likely lead to changes in fuelling conditions, which should in turn be reflected in fuelling time and giving-up density. During their migration, Bewick's Swans Cygnus columbianus bewickii refuel on belowground tubers of Fennel Pondweed Potamogeton pectinatus in shallow lakes. We studied giving-up density and stop-over use (expressed in bird-days) of Bewick's Swans at an autumn stopover site (Lauwersmeer, The Netherlands) during 1995-2008, as dependent on local environmental conditions. High water levels were hypothesized to restrict access to tuber stocks. High water levels at the stopover site were predicted to lead to higher giving-up densities and less bird-days spent at the stopover. Annual variation in giving-up densities and number of bird-days was strongly associated with year-to-year differences in initial tuber biomass density and number of days with high water levels. As predicted, giving-up density increased and bird-days decreased with the number of days with high water level. We conclude that, in line with time-minimizing migration, changes in fuelling conditions may lead to underuse of a stopover site. Underuse of stopovers by migratory birds has been reported before but only in the sense that more food was left at stopover sites than at wintering sites. In contrast, in our case, dealing with a given stopover site, more food is left behind in some years than in other years. © 2013 The Author(s).
Fijn R.C.,Bureau Waardenburg |
Hiemstra D.,Koartwald 13 |
Phillips R.A.,Natural Environment Research Council |
Van Der Winden J.,Bureau Waardenburg
Ardea | Year: 2013
Arctic Terns Sterna paradisaea have an exceptionally long-distance migration, annually travelling back and forth between the Arctic and the Antarctic. Birds from Greenland, Iceland and the USA were recently found to spend most of the non-breeding period in the Weddell Sea, a small part of the large Antarctic range of Arctic Terns. Based on ring recoveries and sightings of West European Arctic Terns in the Indian Ocean and Australian waters, we expected that terns from The Netherlands (the southern limit of the breeding range) inhabit different Antarctic regions during the non-breeding season to their conspecifics from Greenland. To find out, geolocators were deployed on seven Arctic Terns captured on the nest in 2011 in The Netherlands. All birds were recaptured in 2012 and five devices yielded information on migration routes. The tracked terns spent on average 273 ± 7 days away from The Netherlands, and visited known staging areas in the North Atlantic and the Benguela Current, on both the outward and return journey. Similar tracks were observed in the terns from Greenland. However, hereafter the terns from The Netherlands moved to a previously unknown staging area in the central Indian Ocean, between 20-40°N and 65-100°E, and spent most of the non-breeding season in the Southern Ocean between 35-150°E. One bird migrated as far as New Zealand. Eventually, all five birds spent the austral summer in Wilkes Land, Antarctica, before flying back to the breeding colonies with a small detour to the same North Atlantic staging area they visited on their southward migration. The total travel distance in the course of the non-breeding period was ∼90,000 ± 2000 km, which substantially exceeds previous estimates for this species. Our study revealed new offshore staging areas and a yet unknown route through three different oceans, the longest bird migration described thus far.
Lensink R.,Bureau Waardenburg |
Otteris G.,Ganzebloem 14 |
Van Der Have T.,Goudsbloem 55
Limosa | Year: 2013
In this paper the population development of non-indigenous species in the breeding avifauna of The Netherlands is described. Four categories of non-indigenous species are distinguished: (1) invasive alien species, which successfully breed, increase in numbers and expand their range; (2) other (non-invasive) alien species, which have established (successful) breeding attempt(s), but do not increase nor spread; (3) introduced geese and ducks, that are native as migrant and wintering species, but whose establishment as breeding birds is not natural, and (4) feral species, domesticated forms now successfully breeding in the wild, of which some are increasing and spreading. Presently 19 invasive species are recognized, of which 17 breed annually in the Netherlands, and two species of flamingo breed just across the Dutch-German border (table 1). Since the first invasive species were noticed in thei96os, the number of species involved has risen (Fig. 2). All species involved are residents and censuses of breeding and non- breeding birds yield similar estimates of annual increase (Tables 1,2, Fig. 2). Most have increased with more than 10% per year over the past decades, but rates of increase have slowed down for most species in the last 10 years (Fig. 1). More than 20 other non-indigenous species have made at least one breeding attempt in recent years (Fig. 3). The number of species involved is increasing per decade. In de past 30 years several geese and ducks that were hitherto known only as native winter visitors started to breed in the Netherlands. The first was Barnacle Goose (considered to have escaped from waterfowl collections), followed by Greater White-fronted Goose (released birds formerly used as hunting decoys). In recent years a few more species have followed (Tab. 3, Fig. 1). Among domesticated forms, a few decades ago only three species had significant feral populations: feral pigeon, feral duck and Mute Swan. An increase was noticed mainly among domesticated waterfowl (Table 4, Fig. 1). The increasing and expanding species share certain features: they are originally residents, and mainly herbivorous (Fig. 4). Piscivore or granivore feeding habits are less common, but some species with these habits have been successful. Migratory species and insectivores are lacking among the successful non-indigenous birds. Many successful species are common in the bird trade and hence well-represented in collections from which they can escape. In the near future more species can be expected to become successfully established in the wild.The ongoing climate change (Fig. 5) may help invasive species with a (sub)tropical origin. More detailed information about exotic species in The Netherlands can be found in Lensink etal. (2013b), at www.buwa.nl.
Menno Soes D.,Bureau Waardenburg |
Majoor G.D.,Jekerschans 12 |
Keulen S.M.A.,Mesweg 10
Aquatic Invasions | Year: 2011
Bellamya chinensis, an Asian snail species, is reported for the first time from the Netherlands. These records are also the first reports from Europe. The species is commercially sold for garden ponds and aquaria, from which they may have escaped or been released. It is anticipated that this species will become invasive in the Netherlands and beyond. © 2011 The Author(s).
Van Der Winden J.,Bureau Waardenburg |
Van Horssen P.W.,Bureau Waardenburg |
Poor M.J.M.,Bureau Waardenburg |
Gyimesi A.,Bureau Waardenburg
Ardeola | Year: 2012
Birds performing long-distance migration without substantial refuelling en route rely on fat reserves accumulated in the post-breeding, pre-migratory period. In order to fill a knowledge gap in the pre-migratory behaviour of purple herons Ardea purpurea, a species conducting a 3, 500-4, 000 km migration journey within 5-7 days, 12 adult and four juvenile purple herons were equipped with satellite transmitters in The Netherlands. The birds were followed during and after the breeding period until they departed for their migration. Based on the recorded positions, the location and the size of pre-migratory feeding areas were identified, as well as the duration herons used these sites. In addition, the location of and the distance flown to and from night roosts could also be defined. The results revealed that failed breeders started migration at the same time as successful breeders resulting in a longer pre-migratory period. After fledging, juveniles showed an initial "search period" before settling down at a final premigratory site, which resulted in later departure to Africa compared with adults. Most of the dusk- and daylight period (amounting altogether to 15-18 hours) was spent at the feeding sites. After breeding, most adults remained to use the same feeding areas but switched from sleeping in the colony to night roosts within feeding areas, likely to minimize the daily flight costs. Based on the daily foraging time, the pre-migratory period seems to be sufficient to deposit reserves for a migration journey of several thousand kilometres. Above this, our results generally highlight the importance of high-quality premigratory feeding areas for long-distance migrants without extensive stop-over periods.
Gyimesi A.,Bureau Waardenburg |
Lensink R.,Bureau Waardenburg
Wildfowl | Year: 2012
The Egyptian Goose Alopochen aegyptiaca was introduced as an ornamental species to parks in the Netherlands during the 20th century because of its exotic plumage. Escaped birds started to breed in the wild in 1967, and the species has now colonised most of the country. From the 1980s onwards the birds spread further to Germany, then to Denmark, while escapes from parks in Brussels established viable populations there and in France. This study summarises the latest available information on the numbers and distribution of free-living Egyptian Geese in the Netherlands and Europe. The population dynamics of the species were analysed to provide a better understanding of the development of the Dutch population over the past 40+ years, with special attention paid to the effects of culling, natural winter mortality and possible habitat preferences. Numbers breeding in the Netherlands were estimated at c. 10,000 pairs in 2010, and the total population at c. 45,000 individuals in winter 2010/11. Both breeding and non-breeding numbers increased exponentially (by 28% annually) from the establishment in the wild until 1999. However, the rate of increase has slowed in the last ten years, likely due to saturation of available breeding sites and an increase in culling activity. Within-season mortality in severe winters exceeded that during mild winters. The success of the Egyptian Goose in the Netherlands can likely be attributed to the abundance of freshwater areas available close to grasslands with few trees. Extrapolation up to 2010 of trends observed in Belgium and Germany until 2005 and 2006, respectively, suggests that these breeding populations together exceed 16,000 pairs, bringing the total numbers breeding in northwest Europe (including pairs in Britain, France and Denmark) to > 26,000 pairs. © Wildfowl & Wetlands Trust.
Van Der Winden J.,Bureau Waardenburg |
Poot M.J.M.,Bureau Waardenburg |
Van Horssen P.W.,Bureau Waardenburg
Ardea | Year: 2010
Large and heavy birds usually use soaring flight during long-distance migration or make regular stopovers en route for substantial refuelling. Purple Herons are large, long-distance migrants. Because of their size, large herons migrating southwards from Europe to Africa were expected to make one or more stopovers to refuel. However, data from seven Purple Herons, fitted with satellite transmitters, showed that the herons were able to cover the distance into the Sahel of about 4000 km within 5-7 days. One individual even flew 5600 km non-stop, mostly over sea. The herons migrated mostly at night and partly during the day with a high travel speed indicative of flapping flight. The herons made few diurnal stops in Europe and North Africa. Substantial 'stopover' time was limited entirely to a period of several weeks before departure, and after arrival south of the Sahara. We assume that this is energetically possible for birds with a maximum wing load of 4-5 kg body mass per m2 of wing surface. Larger wing loads as in storks or raptors prescribe soaring or refuelling with the consequence that most migratory journeys to African wintering grounds then take at least a month. The results emphasize the conservation importance of abundant and high-quality feeding habitat near the breeding areas for pre-migratory fuelling of this species. Furthermore, arrival habitat is likely to be more essential than previously expected. We suspect that the lack of suitable arrival habitat might explain the observed high adult mortality in dry Sahel periods better than 'winter' survival.