Waterbird Breeding Research Articles

Relationships between breeding waterbird abundance, diversity, and clear water status after the restoration of two shallow nutrient‐rich Danish lakes

Abstract Breeding waterbird communities have suffered globally from the effects of anthropogenic changes in water quality (especially nutrient enrichment) in recent decades, but few studies have demonstrated the positive effects of restorative actions. Annual breeding waterbird surveys in the period 1977–2005 at two restored southern Danish lake basins (combining nutrient load reduction and biomanipulation) showed an up to five‐fold increase in abundance, and considerable changes in species richness and diversity, following restoration to clear water status in both lakes. Parallel surveys at a third lake, which retained clear water quality throughout, offering a form of natural ‘control', showed no such changes over the same time period. Consistent relationships between breeding waterbird abundance, species richness, and diversity with measures of water clarity (Secchi disc depth, chlorophyll a, and suspended matter) suggest that water clarity mainly drives the relationship; inverse relationships between these measures and total nitrogen and phosphorus were less consistent than for water clarity. The results suggest that an improvement in water clarity plays a key role in restoring breeding waterbird communities and suggest that breeding waterbirds can be indicators of the success of lake restoration projects, but more studies are needed to confirm their wider utility under a variety of conditions.

Avian-botulism risk in waterbird breeding colonies and implications for environmental water management

Avian botulism poses a significant risk to waterbird health in Australian wetlands. This paralytic, often fatal, disease occurs when birds ingest a neurotoxin produced by the bacterium Clostridium botulinum. Our current understanding of avian botulism comes largely from studies in the northern hemisphere, with many of these studies linking outbreaks of avian botulism with poor water quality. The Murray–Darling Basin provides the most important breeding habitat for colonial waterbirds in Australia, but the frequency of large-scale breeding events has declined, and waterbird populations are near record-low numbers. Avian botulism has the capacity to have significant impacts on waterbird recruitment if not managed appropriately. We propose that environmental water-management strategies that aim to maintain water quality through flow delivery to waterbird colonies could mitigate the risk of botulism outbreaks and contribute to waterbird population recovery.

Species Identification and Unlocking Hidden Genetic Diversity of Confiscated Slow Lorises (Nycticebus spp.) Based on Mitochondrial DNA Markers

Confiscated slow lorises (Nycticebus spp.) at Bangpra Water-Bird Breeding Center (BWBC) in Thailand provided an opportunity to demonstrate the application of noninvasive genetic approaches for species identification when morphology of the animals was ambiguous. The slow lorises at BWBC had been assigned to either N. bengalensis or N. pygmaeus, based on body size. However, the morphology of N. bengalensis is highly variable and overlaps with that of N. coucang (sensu stricto). Phylogenetic analysis of cytochrome b and d-loop mitochondrial regions placed all confiscated N. pygmaeus with the published sequences of N. pygmaeus and distinguished them from other Nycticebus. All other confiscated individuals formed a monophyletic clade, most individuals grouping with published N. bengalensis sequences from wild populations in Vietnam and distinct from Peninsular Malaysian and Sumatran N. coucang, Javan N. javanicus and Bornean N. menagensis. Six individuals within the N. bengalensis clade formed a separate subgroup that did not group with any reference material as indicated by phylogenetic and haplotype network analyses. Whether these trafficked individuals are undiscovered wild populations will require further investigation. Additional genetic studies of wild slow loris populations in different regions are therefore urgently required for reference to aid the protection and conservation of these threatened species.

Social attraction used to establish Caspian tern nesting colonies in San Francisco Bay

Conservation of colonial waterbird breeding populations often includes restoring historic nesting habitat or establishing new nesting habitat in protected areas. However, colonization of new or restored nesting habitat may be hindered by the lack of social cues from nesting conspecifics to attract prospecting birds. Social attraction, whereby decoys and colony sound recordings are used to mimic active nesting colonies, has been used successfully to establish waterbird nesting colonies throughout the world. We constructed islands, modified the substrate so that it was attractive to nesting Caspian terns (Hydroprogne caspia), and then used social attraction to establish nesting colonies within two managed ponds in San Francisco Bay, California where Caspian terns had not previously nested. During the 2015–2017 breeding seasons, we deployed decoys of adult Caspian terns, broadcasted colony sound recordings, and monitored Caspian tern response. Caspian terns formed nesting colonies within weeks of social attraction deployment at each of the two ponds in 2015, and the size of these colonies increased in each subsequent year of the study. In 2017, the final year of the study, we estimated a minimum of 501 breeding pairs between the two colonies, making them two of the three largest Caspian tern colonies in the San Francisco Bay estuary. In total, these two colonies produced 1343 nests and 531 fledglings over the three-year study period. Nest densities were low (mean: 0.29 nests/m2 of active colony area) compared to other studies, and greater than 80% of the modified island habitat remained unused by nesting Caspian terns in 2017, suggesting that there is additional space for future colony growth. The successful establishment of two of the largest Caspian tern nesting colonies in the San Francisco Bay estuary in just three years demonstrates the potential of using island construction and habitat modifications, combined with social attraction measures to establish waterbird nesting colonies.

A functional perspective for breeding and wintering waterbird communities: temporal trends in species and trait diversity

Waterbird communities are prone to strong temporal changes both seasonally and annually, but little is known about how this affects their functional diversity and community assembly. Detecting temporal trends in taxonomic and functional diversity within (alpha diversity) and between (beta diversity) communities in breeding and wintering seasons could give insight into the ecological processes driving those trends. In this study, we investigated trends in wintering and breeding waterbirds within and between eleven wetlands in Mediterranean Spain, using a 28‐year time‐series up to 2017. We assessed the temporal trends in taxonomic and functional diversity measures, and compared observed functional diversity values with null expectations, in order to explore the mechanisms driving community assembly. We found increases over time in species richness and in the occupied functional space for both wintering and breeding communities, indicating that species with distinct functional roles were added in both seasons. However, the distribution of the abundances in the functional space was different for breeding and wintering communities. Dissimilarity of species and functional traits decreased among wetlands, suggesting that some of the same functional traits were added to the different wetlands, increasing regional homogenization through time. This is reflected in increases over time in mean body mass, diet plasticity and in the importance of fish in waterbird diets, plus declines in the dietary importance of invertebrates and in plasticity of feeding strata. Furthermore, species composition between wintering and breeding communities, but not trait composition, has become more similar through time. Our results highlight that annual changes, and especially seasonal changes, in the composition of waterbird communities have different effects on their functional diversity, and are influenced by opposing community assembly mechanisms.

Breeding Population of Birds on Banifaror Island in the Persian Gulf

This research was conducted in Banifaror Island (26o06'51N 54o26'43E), in Persian Gulf from August 2009 to August 2012. The aim of this study is to provide a complete picture of the Present population of the breeding water birds in Banifaror. Total count method was used to obtain the census of the nests and breeding population of water birds. Forty one species of water birds were identified in this island, of which six species were breeder. Breeding population of Bridled Tern Sterna anaethetus was dominant. The maximum population of this species was 32340 pairs in 2009. Other breeder species were Lesser Crested Tern Sterna bengalensis, Swift Tern Sterna bergii, Caspian Tern Sterna caspia, Western Reef Heron Egretta gularis, and a small colony of White cheeked Tern Sterna repressa. The island has been suggested for to be classified as sensitive habitat for breeding water birds. This is the first record of the status of the breeding population of water birds on Banifaror Island.

Drone Monitoring of Breeding Waterbird Populations: The Case of the Glossy Ibis

Waterbird communities are potential indicators of ecological changes in threatened wetland ecosystems and consequently, a potential object of ecological monitoring programs. Waterbirds often breed in largely inaccessible colonies in flooded habitats, so unmanned aerial vehicle (UAV) surveys provide a robust method for estimating their breeding population size. Counts of breeding pairs might be carried out by manual and automated detection routines. In this study we surveyed the main breeding colony of Glossy ibis (Plegadis falcinellus) at the Doñana National Park. We obtained a high resolution image, in which the number and location of nests were determined manually through visual interpretation by an expert. We also suggest a standardized methodology for nest counts that would be repeatable across time for long-term monitoring censuses, through a supervised classification based primarily on the spectral properties of the image and a subsequent automatic size and form based count. Although manual and automatic count were largely similar in the total number of nests, accuracy between both methodologies was only 46.37%, with higher variability in shallow areas free of emergent vegetation than in areas dominated by tall macrophytes. We discuss the potential challenges for automatic counts in highly complex images.

Screening and application of microsatellite markers for genetic diversity analysis of captive eastern sarus crane Grus antigone sharpii Blanford, 1895 in Thailand.

The eastern sarus crane, Grus antigone sharpii, is distributed in the Indochina area, though it has become extinct in Thailand. The Thai government has tried to repopulate the cranes using wild individuals from Cambodia as initial breeding stock. Although captive breeding can reintroduce species back into the wild, the genetic diversity of the population is also important. This study aimed to screen microsatellite markers to investigate the genetic diversity of G. a. sharpii from two breeding facilities in Thailand and to assess its potential for future conservation programs. Eighteen microsatellite loci isolated from whooping crane (G. americana) and blue crane (Anthropoides paradisea) were screened in all captive reared cranes from Khao Kheow Open Zoo (n = 11) and Bangpra Water Bird Breeding Station (n = 17), Chonburi Province. Of 18 loci analyzed, 14 were found to be polymorphic, and 3 loci were in linkage disequilibrium. Apparent deviation from Hardy-Weinberg equilibrium was observed only at locus Gram8, resulting from the presence of a null allele. The average expected and observed heterozygosities from 10 loci analyzed are 0.61 and 0.64, respectively. The overall fixation index suggested that cranes from both facilities shared many common alleles (FST = 0.023, p < 0.05); in addition, Bayesian clustering analysis implied that cranes from two breeding facilities are homogeneous (K = 1). Our findings reveal high level of genetic diversity of the captive crane population in Thailand and suggest that the breeding stocks may be suitable for ensuring a sustainable breeding program in the future.

Decline in colonial waterbird breeding highlights loss of Ramsar wetland function

Water resource development on rivers significantly affects life cycles of species reliant on wetlands. However, assessing ecological impacts is often difficult because they are realised over long-time periods and large spatial scales, particularly on highly variable dryland rivers. Thirty percent of all Ramsar wetlands are in drylands. We examined the effects of diversions of water upstream on colonial waterbird breeding at the Narran Lakes, supplied by a highly variable dryland river. Narran Lakes is an important Ramsar-listed wetland in Australia for its provision of habitat for wetland fauna during key life history stages, including colonially breeding waterbirds. We use historical ibis breeding data over five decades (1970–2016) to determine the flow requirements for colonial waterbird breeding and modelled the impacts of water resource management options (current and restoration) on breeding. We identified thresholds (>154,000 ML in 90 days with a secondary threshold of >20,000 ML in the first 10 days) of river flow volume necessary to stimulate breeding. Water resource development reduced the frequency of large flows resulting in ibis breeding by 170%, from 1 in 4.2 years to 1 in 11.4 years. Restoration efforts by government to recover water for the environment was predicted to improve colonial waterbird breeding frequency associated with large flow events to 1 in 6.71 years, representing a 59% reduction from pre-development periods. Our framework has global application as a method for identifying long-term impacts of water resource development on key Ramsar wetland areas. This is important, as few mechanisms exist for assessing impacts and identifying restoration options on the listed criteria for many Ramsar wetlands.

The Far East taiga forest: unrecognized inhospitable terrain for migrating Arctic-nesting waterbirds?

The degree of inhospitable terrain encountered by migrating birds can dramatically affect migration strategies and their evolution as well as influence the way we develop our contemporary flyway conservation responses to protect them. We used telemetry data from 44 tagged individuals of four large-bodied, Arctic breeding waterbird species (two geese, a swan and one crane species) to show for the first time that these birds fly non-stop over the Far East taiga forest, despite their differing ecologies and migration routes. This implies a lack of suitable taiga refuelling habitats for these long-distance migrants. These results underline the extreme importance of northeast China spring staging habitats and of Arctic areas prior to departure in autumn to enable birds to clear this inhospitable biome, confirming the need for adequate site safeguard to protect these populations throughout their annual cycle.

Nutrient availability reduced in older rural impoundments in coastal Bay of Fundy, Canada

The Cumberland Marsh Region (CMR), located at the head of the Bay of Fundy, is an important area for waterbird foraging, and wetland restoration and creation. Wetland managers in the CMR have observed that waterbird usage is high when wetlands (impoundments) are newly created, but can decline upon impoundment aging—a phenomenon called wetland senescence that is not well understood. We examined surface water chemistry among newly created and older impoundments in the CMR during the summer months (when waterbird breeding and staging are important), and hypothesized that nutrient availability would be reduced in older impoundments if nutrient loadings were primarily of internal origin. Despite ample rainwater and proximate agricultural sources, macro and micronutrient concentrations in impoundment surface water were significantly higher in newly created impoundments ( 30 years) and impoundments 5–7 years in age. We suspect that impoundment creation has potential to generate high productivity levels, and older impoundments lack land-derived nutrients and may not sustain long-term nutrient availability when waterfowl brood foraging is important. More research is required to better understand wetland rehabilitation strategies that can help sustain nutrient availability, and inputs and pathways in impoundments.

Growth and Development of American White Pelican (Pelecanus erythrorhynchos) Chicks at Marsh Lake, Minnesota, USA

Abstract. The American White Pelican (Pelecanus erythrorhynchos) is an iconic waterbird breeding in the Prairie Pothole and Upper Midwest Regions of North America. Significant variation in recruitment occurs among years. However, mechanisms affecting recruitment, such as variation in size at hatching and chick growth, have not been quantified. In this study, size at hatching and growth rates of American White Pelican chicks were examined at Mash Lake, Minnesota, USA, during 2010–2012. On the day of hatch, the mass and lengths of tarsus, wing and culmen were recorded for the oldest chick in 2-egg nests. No difference was detected in skeletal size at hatching during 2010–2012, but mass of chicks was 11% lower in 2010 than in 2011. Growth rates for mass and wing did not differ between 2011 and 2012, but over 40% of the variation in absolute and instantaneous (relative) growth rates of tarsus was explained by year, with higher rates in 2011; in 2011, nest initiations were started later than other years. Littl...

Hnízdní avifauna vodních a mokřadních druhů ptáků na rybnících ve středním Pobečví v letech 1993-2002

Hnízdní avifauna vodních a mokřadních druhů ptáků na rybnících ve středním Pobečví v letech 1993-2002

Conservation Objectives for Wintering and Breeding Waterbirds in California's Central Valley

Author(s): Shuford, W. David; Dybala, Kristen E. | Abstract: Birds associated with wetlands have declined historically across North America from extensive habitat loss and degradation. Among the regions most affected is California’s Central Valley, where over 90% of the wetland base has been lost. Still, this region remains of continental importance to waterbirds. On-the-ground conservation efforts for all bird groups are the focus of the Central Valley Joint Venture, guided by a periodically updated implementation plan. To track progress toward goal attainment, that plan sets time-bound, quantitative conservation goals. Lacking robust data on the size and trends of populations of most species of waterbirds in the Central Valley, we set conservation goals for this group by selecting 10 focal species. These species are of heightened conservation concern or are otherwise representative of the habitat needs of Central Valley waterbirds. Given the great loss of historical habitat, we assumed focal species populations have declined by ≥ 50%. Hence, we defined population objectives for most focal species as increasing their current populations by 10% over 10 years and doubling them in 100 years. The corresponding habitat objectives are to increase wetlands or enhance suitable crops for waterbirds in proportion to the population objectives. These include an increase over 10 years of 7,948 ha (19,641 acres) of winter seasonal wetlands, 921 ha (2,276 acres) each of semi-permanent and summer seasonal wetlands, and 573 ha (1,416 acres) of strategically placed riparian forest. Agricultural needs include additional winter flooding of 15,160 ha (37,461 acres) of rice and 2,137 ha (5,281 acres) of corn. We distributed the habitat objectives across five planning regions, in some cases favoring proportionally larger increases in those regions with the greatest need. To maximize success, however, conservationists must take into account the specific needs of individual waterbird species, as a one-size-fits-all approach will not support the highest diversity of waterbirds.

A literature review of Algerian salt lakes: values, threats and implications

Chotts are salt lakes located in the arid regions of Northern Africa. These unique wetlands are recognized for their role in the migration and breeding of waterbirds and economic values generated from mineral extraction, agriculture and tourist activities. Despite their importance for flora and fauna biodiversity, they continue to face important threats due to human activities. This article consolidates a literature review of Algerian chotts from global to local importance. An in-depth view demonstrates the changes in land use of two large chotts in the southeastern region of Algeria: Chotts Merouane and Melghir. Land use images highlight a net expansion of agricultural lands, a decrease in grazing area around the lakes and a decrease of salt lake surface area. The local focus highlights the threats and changes of Algerian and Northern African chotts and proposes some perspectives for the future.

Effects of habitat change on breeding waterbirds in Arin (Sodali) Lake, Turkey

Effects of habitat change on breeding waterbirds in Arin (Sodali) Lake, Turkey

Variation in population trends and spatial dynamics of waterbirds in a boreal lake complex

Breeding waterbird populations were studied in a boreal lake system between 1986 and 2012 to find out whether there are differences in temporal trends and spatial variation between waterfowl, grebe, diver and gull species. The study was based on censusing all waterbirds in a lake complex of 45.75 km2 of water area and 290 km of shoreline length (scale 1:20,000), and the results were compared with the changes in water quality during the study period. The population density of species varied significantly between thewater bodies, showing thatwaterbird species prefer certain water bodies within the lake system. Spatial variation ofmanywaterfowl – gull species and diver – gull species pairswere similar probably due to heterospecific attraction or similarities in habitat preferences. The temporal density change of breeding ducks and grebes was high: seven of the eight most abundant species showed significant temporal density patterns, having either linear (negative) trend or non-linear (quadratic, first increase then decrease) population change. Pooled pair numbers of waterfowl species were first stable, but declined drastically by half between 2003/2004–2012. In contrast, two out of four gull species increased, and the Black-throatedDiver did not show any significant trend.Water clarity in the lake complex had decreased during the study period, which may have been one reason causing the population changes of waterbirds, because the increase in turbidity largely explained the negative trend of declining ducks.Climate changemay accelerate eutrophication, having, in turn a negative effect on waterbird populations.

Long-term trend of the waterbird community breeding in a heavily man-modified coastal lagoon: the case of the important bird area “Lagoon of Venice”

The aim of the paper is to examine the temporal and spatial changes observed over a 25-year period in the waterbird community nesting in the largest coastal lagoon around the Mediterranean; to examine driving factors for the observed changes; to address the most urgent conservation actions. Published sources and field surveys made between March and July were used to assess number of breeding pairs of the commonest waterbirds in 1990–1992, 2000–02 and 2012–14. The breeding waterbird community exhibited several changes in its structure, with an overall positive trend; the number of species increased from 14 to 25 and the mean yearly abundance increased from 6155 to 14,008 pairs. The diversity (H′) increased slightly, whereas similarity indices and nMDS ordination both highlighted clear differences between 1990 and 1992 and 2012–2014 communities. The increase in richness and abundance were mostly due to the immigration of birds from nearby wetlands, to the partial recovery of lagoon ecological conditions since the end of the 1980s and to the occurrence of suitable man-made habitats, such as fish farms, dredge islands and a constructed wetland. The fraction of the population nesting at artificial sites and fish farms increased from 50% in 1990–1992 till 80% in 2012–2014, highlighting the importance of artificial breeding sites in costal lagoons. At the opposite natural nesting habitats, such as saltmarshes and beaches are losing importance for breeding waterbirds, thus requiring urgent conservation measures.

Habitat Selection by Forster's Terns (Sterna forsteri) at Multiple Spatial Scales in an Urbanized Estuary: the Importance of Salt Ponds

Abstract. The highly urbanized San Francisco Bay Estuary, California, USA, is currently undergoing large-scale habitat restoration, and several thousand hectares of former salt evaporation ponds are being converted to tidal marsh. To identify potential effects of this habitat restoration on breeding waterbirds, habitat selection of radiotagged Forster's Terns (Sterna forsteri) was examined at multiple spatial scales during the pre-breeding and breeding seasons of 2005 and 2006. At each spatial scale, habitat selection ratios were calculated by season, year, and sex. Forster's Terns selected salt pond habitats at most spatial scales and demonstrated the importance of salt ponds for foraging and roosting. Salinity influenced the types of salt pond habitats that were selected. Specifically, Forster's Terns strongly selected lower salinity salt ponds (0.5–30 g/L) and generally avoided higher salinity salt ponds (≥ 31 g/L). Forster's Terns typically used tidal marsh and managed marsh habitats in proportion to ...

Improving Bullfrog Capture Methods in Areas Managed for Hawaii's Endangered Endemic Waterbirds

American bullfrogs were introduced to Hawaii’s wetlands from California in the late 1800s. As in other areas where American bullfrogs have been introduced, these voracious predators threaten Hawaii’s native fauna. Of particular concern are Hawaii’s federally endangered endemic waterbirds: the Hawaiian stilt, Hawaiian coot, Hawaiian gallinule, and Hawaiian duck. Wetland managers in Hawaii control bullfrogs for the benefit of these endangered waterbirds. The U.S. Fish and Wildlife Service manages several core wetlands on national wildlife refuges in Hawaii that are necessary for survival of the waterbirds. These refuges include bullfrog control as a management strategy. Unpublished studies on James Campbell National Wildlife Refuge have documented bullfrogs as a major predator of newly hatched endangered waterbird chicks. This refuge currently maintains a year-round bullfrog trapping program with increased effort in the spring during the peak of waterbird breeding. Existing trapping methods employ a simple fish-style funnel trap with red flagging used as an attractant. As part of an effort to improve efficacy of current bullfrog capture methods, we investigated the effectiveness of different attractants for the traps. In addition to the current attractant of red flagging, we tested light, bullfrog call acoustic recordings, and life-size bullfrog decoys. The results showed that most of the treatments were no more effective than the control (no attractant). If we can improve bullfrog trap yields, we expect greater chick survival for the endangered Hawaiian waterbirds.