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125 results for “Waterbirds”

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Understanding arid‐region waterbird community dynamics during lake dry‐downs

These data were collected to explore changes in the bird community associated with Lake Ngami, Botswana, through successive drydown periods. Our analysis shows significant shifts, driven partially by changes in water level, in the species composition of the bird community over the period of study. The data set contains standardised half-hour point counts for the bird community of Lake Ngami, Botswana; and R code used for community-level analyses of the resulting time series. Counts were undertaken every 4 months from October 2007-July 2009. We used the data to test three theoretical predictions: simplification of the bird community over time due to a reduction in habitat area and concurrent niche loss; large fluctuations in densities of mobile, opportunistic species; and high variance in predator and prey abundance. Despite temporal variance in species accumulation, we observed no obvious simplification of the bird community over time. There were distinct but consistent groupings of abundance and composition across transitional stages in lake water levels. The data do show some rapid shifts in functional composition, such as loss of deepwater foragers; winners and losers also occurred within foraging guilds.

opencc-zeroAug 2021View details →

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Effects of released farmed mallards on species richness of breeding waterbirds and amphibians in natural, restored, and constructed wetlands

Common practices in current game management are wetland restoration and creation, as well as releases of quarry species. We studied the impact of releases of mallard ducklings on species richness of wild waterbirds and amphibians on three types of wetlands: natural, constructed and restored. Data on species richness, macrophyte cover and water characteristics (total phosphorous and pH) were collected at 32 sites in an agricultural landscape in southern Sweden. In total, 14 species of waterbirds were recorded, ranging from zero to seven per wetland and survey. Amphibians were present in 24 of the 32 wetlands; in total five species were found, ranging from zero to three per wetland. By using generalized linear modelling we found that wetland type best predicted waterbird species richness. Constructed wetlands had significantly more waterbird species, regardless of whether they were used for mallard releases or not. There were breeding amphibians in 62% of natural, 100% of restored and 77% of constructed wetlands. Breeding amphibians were present in 84% of wetlands without, and in 62% of wetlands with releases. However, included variables did not explain amphibian species richness in the wetlands. Releasing large numbers of mallards on a wetland and providing food ad libitum is likely to affect water quality, nutrient availability and predation pressure. Indeed, phosphorous levels were significantly higher in release wetlands, but no differences were found between wetland types.This means that mallard releases may increase nutrient loads in environments that are already eutrophied. However, in our study system releases did not influence species richness of waterbirds and amphibians locally. Constructing wetlands for mallard releases can thus have positive local effects on species richness.

opencc-zeroAug 2021View details →

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Seed dispersal by waterbirds: a mechanistic understanding by simulating avian digestion

Waterbirds disperse plant species via ingestion and egestion of seeds (endozoochory). However, our understanding about the regulating effects of seed traits, underlying mechanisms and possible (co)evolutionary processes is limited by our traditional reliance on data from feeding experiments with living waterbirds. Here, we overcome these limitations by developing and applying a new bioassay that realistically simulates digestive processes for Anseriformes waterbirds. We test three hypotheses: (1) seed survival and germination are most affected by mechanical digestion in the waterbird gizzard; (2) seed size, hardness, imbibition and shape regulate seed survival; and (3) plants growing in aquatic habitats benefit most from endozoochory by waterbirds. Experiments with 28,200 seeds of 48 plant species demonstrated species-specific seed survival that was entirely determined by digestion in the avian gizzard. Intestinal digestion did not affect seed survival but affected seed establishment (germinability and germination time) for 21% of the species. Large, hard seeds survived the simulations the best, in contrast to generally higher seed survival for smaller seeds during in vivo experiments. This mechanistically explains that small seeds escape digestive processes rather than being inherently more resistant (the 'escape mechanism'), while large seeds are retained until fully digested or regurgitated (the 'resistance and regurgitation mechanism'). Plants growing in wetter habitats had similar seed survival, but digestive processes stimulated their germinability and accelerated their germination more than for terrestrial plants. This indicates a relative advantage of endozoochory for plant species growing in wet habitats, possibly reflecting a co-evolutionary response related to dormancy breaking by gut passage. Simulating seed gut passage using a bioassay allowed establishing mechanisms and identifying relevant seed traits involved in seed dispersal by waterbirds. This information enhances our understanding of how animal species shape plant species distributions, which is extremely relevant now that current anthropogenic pressures already severely impact plant dispersal capacities.

opencc-zeroOct 2022View details →

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Data from: Sensitivity analysis of collision risk at wind turbines based on flight altitude of migratory waterbirds

This dataset contains information on the distribution of geese and swans and the three-dimensional flight trajectories. The former was obtained through vehicle field surveys, interviews, and a literature review. The latter was obtained using ornithodolites.

opencc-zeroMar 2023View details →

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Vessel traffic observations and associated waterbird surveys, March 2020 – February 2021, Roberts Point and Ogden Point, Victoria, BC, Canada

The coastal waters of southern British Columbia, Canada, encompass habitat of international conservation significance to coastal and marine birds, including sizeable areas designated in the early 1900s as Migratory Bird Sanctuaries (MBS) to protect overwintering waterfowl from hunting near urban centres. Two of these, Shoal Harbour (SHMBS) and Victoria Harbour (VHMBS), have seen significant marine infrastructure development in recent decades and experience considerable vessel traffic. We conducted a pilot study using shore-based observers to develop small-vessel baselines for the winter months when regional waterbird numbers are highest. During our surveys, we recorded considerable inter-site variability in vessel traffic characteristics, with one site (SHMBS) a source of nearly twice as many vessels in total as the other (VHMBS). For waterbirds, hourly 3-minute 'snapshot' surveys, combined with daily tallies of incidental observations, showed that community composition also varied by locality, with one site dominated by gulls (Laridae), cormorants (Phalacrocoracidae), and seaducks (Tribe Mergini), and the other by gulls, cormorants, and alcids (Alcidae). Our results demonstrate that fine-scale local variability must be taken into account when managing for vessel traffic disturbance of waterbirds, particularly at sites of high human population density and increasing coastal development. Results are in press in PLoS ONE (doi:10.1371/journal.pone.0283791).

opencc-zeroMar 2023View details →

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