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Foot-propelled diving comprises the primary locomotion-based feeding strategy for many birds, including families such as Phalacrocoracidae, Anhingidae, Podicipedidae, Gaviidae, and the diving ducks within Anatidae. While the morphology of specialized divers is well known, the corresponding morphology is less known for birds not as specialized but capable of diving, such as the coots (Rallidae, Fulica spp.). To compare the osteology of Fulica with other (non-diving) Rallidae, and with foot-propelled diving birds that are distantly related, we considered osteological characters, as well as the proportion of the hind limb bones and the femoral splay angle to construct a phylomorphospace, and to perform a comparative disparity analysis considering ecomorphologically relevant characters related to swimming and diving. Coots resulted to be significantly disparate from other Rallidae showing many traits of specialized foot-propelled divers, but only noticeable when compared with other rallids, as the degree of development of these traits is markedly less than in loons, grebes, or cormorants. This may correspond to a stabilizing selection of characteristics associated with a generalist morphology in Fulica. Studying adaptation in generalist taxa broadens our understanding of ecomorphologically significant features, thereby enabling us to generalize their evolutionary patterns. [ABSTRACT FROM AUTHOR]

Stoneworts (Charales) are green algae that represent an important food resource for many waterbird species in Europe and elsewhere. Browsing avian herbivores (e.g. swan, goose, duck and coot species) consume Charales plant vegetative parts, by head‐dipping, up‐ending or diving. A lower fibre content and longer growing season may make Charales as attractive to such herbivores as sympatric submerged higher plant species in some circumstances. Charales respond to environmental stress (e.g. drought) by producing abundant diaspores, in the form of oospores (sexual) and bulbils (asexual), both rich in starch, generating abundant food for waterbirds at critical stages in their annual migratory cycles. Waterbirds feed on these by diving (e.g. common pochard Aythya ferina and red‐crested pochard Netta rufina) or by filtering from the water column (e.g. dabbling duck species), ensuring dispersal of sexually produced and vegetative diaspores locally (because of predator swamping) and remotely (through endo‐ and ectozoochorous dispersal by long‐distance migratory waterbirds). Greater invertebrate density and diversity associated with Charales canopies enhances their attractiveness over other submerged macrophyte beds to diving predators [e.g. tufted duck Aythya fuligula, common pochard and Eurasian coot Fulica atra (hereafter coot)]. Fish fry preying on these invertebrates use such vegetation as predator cover, in turn providing prey for avian piscivores such as grebes and cormorants. Abundant Charales contribute to maintaining a transparent water column due to canopy density, nutrient effects, dampening of sedimentation/remobilisation of suspended matter and nutrients and allelopathic effects on other plants (especially phytoplankton). Shallow, relatively eutrophic waters can flip between clear‐water high‐biodiversity (where Charales thrive) and turbid species‐poor depauperate stable states (lacking Charales). Shifts between turbid conditions and rich submerged Charales beds have profound elevating effects on aquatic diversity, to which waterbirds show rapid aggregative responses, making them ideal indicator species of ecological change; in the case of Charales specialists (such as red‐crested and common pochard), indicators of the presence and abundance of these plants. Large‐bodied colonial nesting birds (e.g. cormorants, gulls, heron and egrets) aggregating along lake shores contribute high N and P loadings to water bodies sensitive to such external and internal inputs and can cause local eutrophication and potential loss of Charales. Despite variation from complete seasonal removal of Charales biomass to undetectable grazing effects by herbivorous birds, evidence suggests little effect of avian grazing on biomass accumulation or the stability of community composition (under otherwise stable conditions), but we urge more research on this under‐researched topic. We also lack investigations of the relative foraging profitability of different Charales organs to waterbirds and the degree of viability of gyrogonites (fertilised and calcified oospores), vegetative bulbils and plant fragments after passage through the guts of waterbirds. We especially need to understand better how much the carbonate armour of these organs affects their viability/dispersal via waterbirds and urge more research on these neglected plants and their relationships and interactions with other organisms in the aquatic biota. [ABSTRACT FROM AUTHOR]

North American bird populations have declined significantly since 1970 due to a variety of causes. We estimated long term changes in abundance of wintering waterbirds at Tomales Bay, Marin Co., CA, from 1992-2022. Average total waterbird numbers decreased 11.8%. The most concerning declines for taxa whose numbers in 1992 accounted for at least 5% of the combined numbers of waterbirds were for Surf Scoter (Melanitta perspicillata), Brant (Branta bernicla), Ruddy Duck (Oxyura jamaicensis), American Coot (Fulica americana), and Western (Aechmophorus occidentalis) and Clark's (Aechmophorus clarkii) Grebe. Of 29 taxa that we estimated trends for, 13 declined across our study period. Fourteen taxa had negative trends of ≥2% year–1 for at least 10 consecutive years, meeting the IUCN's Red List criteria for Near Threatened or higher. We accounted for two influencers of primary productivity in the bay: the Northern California Multivariate Oceanic and Climatic (MOCI) index and winter freshwater inflow. MOCI was included in the best model for six taxa while freshwater inflow was informative for eight taxa. A local wetland restoration project led to increases in three of the seven species we modeled. The dynamics of waterbird numbers on Tomales Bay are linked partly to herring but other local to global factors are important. [ABSTRACT FROM AUTHOR]

The study aimed to recognize whether the activity of a semi-aquatic invasive carnivore – the American mink Neovison vison – is related to the distribution of waterbird colonies. For this reason, we monitored mink occurrence in lake reedbeds and the fate of artificial nests imitating those of the great crested grebe Podiceps cristatus. The location of artificial nests in the grebe colony increased the probability of their survival compared to those placed outside the grebe colony. During the study, mink activity increased over time. In general, it was lower in colonies than outside of them, suggesting that the presence of natural nests does not increase the probability of mink occurrence in lake reedbeds. However, mink activity was negatively correlated with the distance from the lake shoreline and differed spatially according to the presence or absence of natural grebe nests. In grebe colonies, the probability of mink occurrence at greater distances from the lake shoreline was higher than outside, which can be explained by optimizing swimming effort while searching for prey. In conclusion, mink activity in colonies was lower than in areas with no waterbird nests, and nest location in a colony decreased predation risk by mink. [ABSTRACT FROM AUTHOR]

The Domaine de la Palissade is a 700-ha nature reserve located at the mouth of the Rhône river in southern France. Since 2006, the tidal wetlands have been sprayed with Bacillus thuringiensis israelensis (Bti) and water level fluctuations minimized to reduce mosquito nuisance. Aerial spraying of VectoBac® 12AS (32 ITU/ha) is carried out 10 to 23 times a year, whenever Ochlerotatus caspius and Oc. detritus larvae develop, covering between 611 and 1937 cumulated hectares. Long-term trends (2000–2013) in monthly abundance of 50 bird species were compared with two nearby nature reserves that served as controls. A significant decrease in abundance of eight species (from 1958 to 941 monthly counts) was attributed to mosquito control operations and more specifically to: (1) aircraft disturbance caused by aerial spraying in a proportion of 36%, affecting mostly ducks; (2) stabilization of water levels in a proportion of 34%, affecting mostly grebes; and/or (3) reduced food resources caused by Bti effects in a proportion of 30%, affecting mostly waders. The European coot, affected negatively by all three factors, suffered the highest decline. Alternatively, the lower water levels and higher salinity resulting from the reduced exchanges with the Rhône River had a positive impact on five species, mostly gull and shorebirds (from 201 to 280 monthly observations). Overall, this study suggests a 23% significant decrease in waterbird abundance due to mosquito control, in spite of the collaboration between site managers and the operator of mosquito control to minimize negative effects on the non-target fauna. [ABSTRACT FROM AUTHOR]

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In monogamous birds, pair bond maintenance is often dependent on previous breeding success and each parent's effort, because partners gain information about one another's quality and contribution to brood rearing. The asymmetries between mates in parental investment have been theoretically linked to a sexual conflict of interests. Year-to-year pair fidelity decisions in relation to birds' previous-year information about their mates, including territory quality and relative length of brood care, were explored in red‐necked grebes (Podiceps grisegena), a long-lived species with parent-fed young. Overall, mate retention was a major strategy (81.5% of pair-years). The probability of breakage/maintenance of a pair bond was not affected by previous-year hatching success, fledgling production, or territory quality in terms of food abundance for chicks. Reunited pairs bred earlier in the season than new pairs. In pairs that maintained bonds into the subsequent season, females typically terminated care 1–4 weeks before males. The male fidelity indicates that earlier brood abandonment by females may confer some fitness benefits to males and reflect coordination of reproductive effort at the behavioural level rather than exploitation of one partner by another. Significance statement: Pair-living animals deciding whether to keep their old mate for future breeding usually consider their previous reproductive success and the partner's effort. In some monogamous birds, often one of the parents leaves the brood before its mate, which is usually explained in terms of conflict between the sexes over parental care costs. I studied links between previous year's parental effort and mate retention in red‐necked grebes, a long-lived waterbird. Grebes showed high pair fidelity irrespective of recent breeding success. In pairs that stayed together, females typically terminated brood care earlier than their mates. The male fidelity indicates that the unequal duration of brood attendance can be interpreted as cooperation and not conflict, especially as departing females did not attempt a second brood, while male-only care after female departure was sufficient to raise the young. [ABSTRACT FROM AUTHOR]

Although interspecific interactions appear to be less competitive than intraspecific ones, interspecific territoriality is much more frequent and more stable than is commonly believed. When territorial interactions between competing species are repeated, discrimination between heterospecifics can allow for a more precise allocation of resources and risk. An example of such a strategic approach is the dear-enemy effect, according to which individuals are less aggressive to familiar than unfamiliar individuals. We investigated the occurrence of the dear-enemy effect in territorial interactions between two nonpasserine bird species: water rail, Rallus aquaticus , and little crake, Zapornia parva , which compete for food and nest site resources. We used a cross-species playback experiment where water rails received calls of strangers and neighbouring little crakes, while little crakes received calls of water rails in the same manner. In addition, each focal pair was exposed to control calls of little grebes, Tachybaptus ruficollis. In both species, territory holders produced more calls in response to heterospecific strangers than heterospecific neighbours, and the response to control stimuli was the weakest. Furthermore, little crakes often approached and attacked the loudspeakers and mostly when they heard the calls of stranger water rails. Our results indicate that both species were able to distinguish not only each other from the control species, but also specific individuals of the second species. In line with the dear-enemy effect, water rails and little crakes adjusted their territorial response according to the intruder's status, being most aggressive to heterospecific strangers. These findings suggest an adaptive territorial response to resource competition that is commonly confirmed among conspecifics but rarely between individuals of different species. • We studied the dear-enemy effect between two competing bird species. • Water rails and little crakes recognized specific individuals of the other species. • Both species responded with lower vocal intensity to heterospecific neighbours. • Stronger nonvocal response to stranger calls was observed only in little crakes. [ABSTRACT FROM AUTHOR]

Waterbirds are important indicators of wetland health, and understanding their status and trends is necessary for appropriate management and conservation. However, certain species are challenging to survey due to their sensitivity to disturbance and the difficulty of accessing their breeding habitats. This is especially true for colonially breeding marshbirds, for which a multi‐species survey protocol that maximizes accuracy of counts and minimizes disturbance does not exist. Small drone aircraft have shown promise for conducting accurate and low‐disturbance surveys of colonial waterbirds. However, complex marsh vegetation structures and the cryptic nature of some marshbird nests make them difficult to detect in aerial imagery. We used synchronous high‐resolution visible imagery (0.8–2 cm/pixel) and thermal‐infrared imagery (6–16 cm/pixel) captured from a drone to count nests of five species of marshbirds at eight colonies in Saskatchewan, Canada. We compared counts from the imagery to those obtained from traditional ground‐based surveys, generally considered the most accurate survey method for these species. The two types of imagery proved highly complementary, as heat signatures helped detect and confirm nests not easily spotted in the visible imagery, while the detailed visible imagery allowed species identification. For four species (Western Grebe Aechmophorus occidentalis, Franklin's Gull Leucophaeus pipixcan, Forster's Tern Sterna forsteri, and Black‐crowned Night‐Heron Nycticorax nycticorax), drone‐based counts (range 74–1524 nests per colony) were within 5% of ground‐based counts (range 75–1582), while for smaller Black Tern Chlidonias niger colonies (range 3–7 nests), counts from the two methods were always within one nest of each other. Furthermore, an assessment of flight behavior before, during, and after drone surveys found no significant evidence of disturbance by the drone. Our drone‐borne dual visible‐thermal camera approach proved promising for surveying colonial marshbirds and could potentially be implemented in a range of situations where wildlife subjects are difficult to survey with visible or thermal imagery alone. [ABSTRACT FROM AUTHOR]

Drone use in wildlife biology has greatly increased as they become cheaper and easier to deploy in the field. In this paper we describe a less invasive method of using drones and exploring their limitations for studying colonial nesting waterbirds. Western Grebes, like most colonial nesting waterbirds, can be very sensitive to human interaction. Using a 3DR Solo quad copter equipped with a high-resolution digital camera we were able to effectively map and monitor a Western Grebe breeding colony throughout the nesting period with a series of 6 flights. We were able to use drone collected aerial imagery to model nest survival while minimizing disturbance to the birds. However, we were not able to deploy the drone at all of our study sites. Our ability to effectively deploy the drone was hindered by the environmental and vegetation characteristics of a site. Drone technology can be a useful tool, especially when studying a species sensitive to human interaction. However, there researchers should carefully consider their species and study site to evaluate if a drone is the proper tool to meet their objectives. [ABSTRACT FROM AUTHOR]

This note describes interactions between four bird species during a predation attempt by Yellow-footed Gull (Larus livens) on an Eared Grebe (Podiceps nigricollis).The interactions among species were documented on video in a mangrove (Rhizophora mangle and Avicennia germinans) area of the Ensenada La Paz (a RAMSAR site) during winter in the southwest Gulf of California, Mexico on 2 February 2019. This is the first report that has documented an effective killing attempt in the Baja California Peninsula and the second in northwestern Mexico of Yellow-footed Gull predation on Eared Grebe. Additionally, kleptoparasitism attempts against the Yellow-footed Gull by a Great Blue Heron (Ardea herodias) and Turkey Vulture (Cathartes aura) are described and suggest that those species may include prey stolen from gulls (family Laridae) more regularly than presently known based on this opportune observation. [ABSTRACT FROM AUTHOR]

A great variety of waterbirds migrate across western Nevada, where places to rest or refuel are nearly non-existent. One exception is a little-known industrial pond complex at the Albemarle U.S., Inc. facility in Silver Peak. In this paper we analyzed 3 years (2014-2016) of near-daily counts to document the timing, abundance, and stopover biology of 73 species traversing one of the driest regions in North America. Average annual bird-use-days exceeded 350,000, of which 93% were contributed by species with affinities to highly saline habitats. Individuals of most species (total estimated 110,000-183,000) passed through within a day or so, although some Ruddy Ducks (Oxyura jamaicensis), Eared Grebes (Podiceps nigricollis) and American Avocets (Recurvirostra americana) made prolonged stays. We treat the most abundant species in detail and show that data from sites that can be monitored daily can complement studies from sites where daily censuses are not feasible. The Silver Peak ponds attract sufficient shorebirds to warrant consideration as a Site of Regional Importance in the Western Hemisphere Shorebird Reserve Network. [ABSTRACT FROM AUTHOR]

During surveys of the waterbirds of the Lake Bathurst wetland system on the Southern Tablelands of New South Wales, near Canberra (Australian Capital Territory) in most months from 1980 onwards, Hoary-headed Grebes Poliocephalus poliocephalus were found breeding on only six occasions. Nests were built along islands that formed only when Lake Bathurst and the neighbouring Southern Morass reached specific water depths. At higher and lower water levels, Grebes were present but did not breed. The maximum number of nests in a season was 985, much greater than any reported in the literature, but young were produced in only three seasons. Nest failures resulted from falling water levels, heavy rain (and associated rise in water level) or a wind-induced temporary rise in water level. Partial reflooding of the lake triggered late nesting, in April, but the nests were abandoned as the water level fell. High mobility, congregating at refilling wetlands and attempts to nest late in the season by this species may be responses to the ‘boom and bust’ scenario of inland wetlands. [ABSTRACT FROM AUTHOR]

A breeding pair of Australasian Grebes Tachybaptus novaehollandiae was monitored nearly daily between November 2010 and March 2011. This paper describes the responses of the adults to other waterbirds that came within 5 m of their brood, either provoked or unprovoked. Brood loss was rapid, with only one of five chicks surviving more than 3 weeks. Nine instances of brood-defence were recorded, mostly in the first 2 weeks after hatching, as well as one observation of a chick defending itself. The Dusky Moorhen Gallinula tenebrosa was the main species that prompted reactions from the adult Grebes. A Moorhen was seen trying to prey on Grebe chicks on one or probably two occasions, the first time this has been reported. A Purple Swamphen Porphyrio porphyrio was also attacked by the Grebes, and is a likely potential predator of grebe chicks. Ducks and cormorants were attacked or tolerated on different occasions. [ABSTRACT FROM AUTHOR]

Red-necked grebes ( Podiceps grisegena) are piscivorous waterbirds that breed on freshwater lakes in northwestern Canada and stop-over at the Great Lakes during autumn migration to molt feathers and replenish lipid and protein reserves. The objectives of this study were to (1) describe concentrations of, and correlations among, inorganic contaminants in a sample of autumn migrant red-necked grebes from the Great Lakes, (2) compare concentrations of inorganic contaminants to those in autumn migrant common loons from Schummer et al. (Arch Environ Contam Toxicol 62:704, ), (3) evaluate if the inorganic elements are negatively associated with lipid and protein reserves, and (4) determine if nutrient reserves and molt intensity were correlated. None of the 14 contaminants analyzed were above threshold levels known to cause acute health problems in piscivorous birds. Body masses of plucked birds were within the normal reported range. Lipid reserves varied positively with hepatic concentrations of arsenic, copper, iron, nickel, lead, and selenium and negatively with mercury and magnesium. Protein reserves variety negatively with hepatic concentrations of arsenic, calcium, nickel, lead, and zinc and positively with aluminum, cadmium, and iron. A negative correlation was observed between chest molt and lipid reserves but not between nutrient reserves and other feather tracts. The relationships between lipid reserves and both mercury and selenium were consistent with current research on other piscivorous waterbirds at the Great Lakes and justify continued work to determine interactions of these contaminants in waterbirds that breed, stage, and winter in the region. [ABSTRACT FROM AUTHOR]

Grebes (Aves: Podicipedidae) are a threatened family containing species that vary widely in demography. Podicipedidae includes several species that are either rare and confined to a single lake basin, or abundantly distributed across several continents. The most speciose genus, Podiceps, particularly the eared grebe lineage, best reflects this curious demographic pattern by representing the most abundant of extant grebes, several critically endangered species, and a recently extinct species. Here, we obtained genetic data from 3 mitochondrial markers to make phylogenetic and population genetic inferences about the eared grebe clade. Using DNA from tissue, feather, skin, and toe pads, our sampling encompassed all species and subspecies, including the extinct Colombian Grebe ( Podiceps andinus) and migratory and resident populations of the North American Black-necked Grebe ( P. nigricollis californicus). Bayesian inference yielded novel insights into the dynamics of this group, particularly the recent ecological isolation and incipient speciation of the Colombian and Junin ( P. taczanowskii) grebes, as determined from limited genetic divergence and rapid evolution of plumage color and bill shape (elongation, deepening of the culmen). DNA barcode and cytochrome b distances supported these inferences. Population genetic and divergence time analyses further revealed that the abundance of the North American Black-necked Grebe is likely associated with mid-Pleistocene dispersal from South America followed by late Pleistocene expansion during a time when hypersaline lake habitat accommodated large populations of staging birds. In conclusion, the demographic variation among species in the eared grebe group can be explained by recent ecological speciation of both a sympatric and an allopatric nature. Future investigation is warranted to determine whether this pattern of speciation and associated rapid phenotypic divergence can be extended to other grebe taxa. Los Podicipedidae son una familia amenazada que incluye especies que varían enormemente en su demografía. Los Podicipedidae incluyen varias especies que o son raras y están confinadas a una única cuenca de un lago, o están distribuidas abundantemente a lo largo de varios continentes. El género Podiceps, que es el que contiene más especies, particularmente el linaje 'con penachos', es el que mejor refleja este curioso patrón demográfico, pues incluye las especies actuales más abundantes, varias especies en peligro crítico y las especies recientemente extintas. En este estudio, obtuvimos datos genéticos a partir de tres marcadores mitocondriales para hacer inferencias filogenéticas y de genética poblacional sobre los Podiceps con penachos. Usamos ADN proveniente de tejidos, plumas, piel y almohadillas de los dedos para abarcar a todas las especies y subespecies, incluyendo la especie extinta P. andinus y las poblaciones residentes y migratorias de P. nigricollis californicus. Las inferencias bayesianas brindaron nuevas ideas sobre la dinámica de este grupo, particularmente sobre el aislamiento ecológico reciente y la incipiente especiación de P. andinus y P. taczanowskii, determinada por una divergencia genética limitada y la rápida evolución del color del plumaje y la forma del pico (elongación y profundización del culmen). El código de barras de ADN y las distancias del cytochrome b apoyan estas inferencias. La genética poblacional y los análisis del tiempo de divergencia revelan adicionalmente que la abundancia de P. nigricollis californicus está probablemente asociada con una dispersión a mediados del Pleistoceno desde América del Sur seguida por una expansión a fines del Pleistoceno durante un período en que el hábitat hipersalino del lago soportó grandes poblaciones de aves. En conclusión, la variación demográfica entre las especies de Podiceps con penachos puede explicarse por especiación ecológica reciente de naturaleza tanto simpátrica como alopátrica. Es necesario realizar futuras investigaciones para determinar si este patrón de especiación y de divergencia fenotípica rápida asociado puede extenderse a otros taxa de los Podicipedidae. Palabras clave: especies incipientes, expansión demográfica, filogenia, forma del pico, Podicipedidae [ABSTRACT FROM AUTHOR]

The aim of the present study was to determine the concentrations of nonylphenols (NPs) and 4-t-octylphenol (4tOP) in the muscles, liver, and kidneys of selected waterbird species. Three species with different feeding habits were selected, i.e., greater scaup (Aythya marila), great crested grebe (Podiceps cristatus), and great cormorant (Phalacrocorax carbo) to investigate the potential effects of diet on the level of contaminants tested. The determination and quantification of analytes were performed using gas chromatography with mass spectrometric detection (GC-MS). The highest NP concentrations were noted in the kidneys of greater scaups and great crested grebes (208.3 and 160.8 μg kg−1 ww, resp.), which were six to fourteen-fold higher than those in the muscles (15.0 and 25.6 μg kg−1 ww, resp.) and livers (22.9 and 13.8 μg kg−1 ww, resp.) of these species. In greater scaups, the mean concentration of NPs in the livers was lower than in the muscles, while in great crested grebes, it was the opposite and higher concentrations were noted in the muscles. The mean concentrations of NPs in the muscles and livers of great cormorants were at similarly low levels (12.5 and 9.7 μg kg−1 ww, resp.). The concentrations of 4tOP in all samples were low, ranging from

Background: We describe the first occurrence in the fossil record of an aquatic avian twig-nest with five eggs in situ (Early Miocene Tudela Formation, Ebro Basin, Spain). Extensive outcrops of this formation reveal autochthonous avian osteological and oological fossils that represent a single taxon identified as a basal phoenicopterid. Although the eggshell structure is definitively phoenicopterid, the characteristics of both the nest and the eggs are similar to those of modern grebes. These observations allow us to address the origin of the disparities between the sister taxa Podicipedidae and Phoenicopteridae crown clades, and traces the evolution of the nesting and reproductive environments for phoenicopteriforms. Methodology/Principal Findings: Multi-disciplinary analyses performed on fossilized vegetation and eggshells from the eggs in the nest and its embedding sediments indicate that this new phoenicopterid thrived under a semi-arid climate in an oligohaline (seasonally mesohaline) shallow endorheic lacustine environment. High-end microcharacterizations including SEM, TEM, and EBSD techniques were pivotal to identifying these phoenicopterid eggshells. Anatomical comparisons of the fossil bones with those of Phoenicopteriformes and Podicipediformes crown clades and extinct palaelodids confirm that this avian fossil assemblage belongs to a new and basal phoenicopterid. Conclusions/Significance: Although the Podicipediformes-Phoenicopteriformes sister group relationship is now well supported, flamingos and grebes exhibit feeding, reproductive, and nesting strategies that diverge significantly. Our multi- disciplinary study is the first to reveal that the phoenicopteriform reproductive behaviour, nesting ecology and nest characteristics derived from grebe-like type strategies to reach the extremely specialized conditions observed in modern flamingo crown groups. Furthermore, our study enables us to map ecological and reproductive characters on the Phoenicopteriformes evolutionary lineage. Our results demonstrate that the nesting paleoenvironments of flamingos were closely linked to the unique ecology of this locality, which is a direct result of special climatic (high evaporitic regime) and geological (fault system) conditions. [ABSTRACT FROM AUTHOR]

The levels of 16 organochlorine pesticides (OCPs) were measured in egg samples of the great cormorant, great-crested grebe, grey heron, little egret, black-crowned night heron and in their prey being bleak, roach, pumpkinseed, goldfish and frogs from Lake Kerkini, NE Greece. Concentrations of most OCPs differed among most bird and prey species. DDTs predominated in all species, contributing to about 80% of the total OCPs in most sample types. Moving up the food chain, the relative contribution of DDTs increased whereas of ∑HCHs and ∑Cycls (cyclodienes) decreased. Regarding trophic transfer, all OCPs exhibited bioconcentration but, in contrast, compounds such as Υ-HCH, endrin, heptachlor, heptachlor hepoxide, α-, β-endosulfan and endosulfan sulfate showed low or no biomagnification. No correlations were found between either bioaccumulation (BAF) or biomagnification factors (BMF) and lipid content of biota. Nevertheless, there was a significant relationship between logKow (the octanol-water partition coefficient) and BAF of all OCPs. OCP bioaccumulation patterns at Lake Kerkini are probably governed by the chemical properties of compounds and their metabolic ways in biota. The levels of OCPs were too low to have adverse biological effects to the waterbirds. The great cormorant, pumpkinseed and Rana frogs are suggested as the most suitable bioindicators for monitoring OCPs at Lake Kerkini due to the highest concentrations of most compounds and showing the greatest bioaccumulative properties. [ABSTRACT FROM AUTHOR]

Abstract: Southern Mediterranean lagoons are among the more vulnerable systems regarding human activities (e.g. agriculture, tourism, urbanization) leading to eutrophication. We analyse the relationship of waterbirds with locally measured or modelled environmental variables (nutrient load, fish production, jellyfish blooms) related with this process, in the Mar Menor lagoon (Murcia, SE Spain), and discuss the potential value of birds as indicators of the trophic status of the wetland. We use GLMs to relate the biomass of the five most abundant and representative waterbird species to these variables, accounting for the potential influence of external factors affecting their population at higher biogeographical scales. A significant effect of such factors was only found for Great Cormorant, which biased the positive response of the piscivore guild to nutrient load (NLD). Red-breasted Merganser appeared relatively insensitive to nutrient enrichment, although declined in the long term. The remaining species responded positively, NLD being a significant predictor of their biomass when a 2-year lag was allowed, although this variable alone had a low explanatory power except for the Coot. When homogeneous temporal phases were defined, grebes could be identified as early warners of eutrophication, and Coot as late-stage ones. The increase of piscivores along a period of declining fish catches could reflect a shift in fish community composition or structure that favours their feeding preferences. The interactive role of jellyfish, buffering temporally the loading of nutrients, may also be related to these changes. [ABSTRACT FROM AUTHOR]

The article focuses on the limnological and topographical analyses of 32 lakes of the Strobel Meseta in Argentina. It investigates the link between the lake type and use by aquatic birds in general, as well as the endemic hooded grebe (Podiceps gallardoi). It mentions the assessment conducted to the overlap between trout aquaculture and critical habitat for waterbirds.

The article discusses a study which examined how Hardstern Bulrush (Schoenoplectus acutus) impacts wave attenuation through its clonal growth characteristics. Nest placement and nesting success in colonial nesting grebes and other over-water nesting waterbirds are influenced by the predictable growth patterns. The researchers constructed an artificial nesting colony to experimentally test how location with respect to wave-exposure affects nest structural integrity in grebes. Environmental components and human disturbance influence waves.

The Mar Menor is the largest coastal lagoon in the Western Mediterranean and it is an important site for wintering and breeding waterfowl. During recent decades several hydrological and land-use changes in the watershed have increasingly threatened the conservation of the lagoon due to the development of urban areas, tourism and agriculture. A dynamic system model has been developed at the watershed scale to estimate the annual load of nutrients reaching the Mar Menor-associated wetlands. At present, mean annual loadings of approximately 2000 tonnes of nitrogen and 60 tonnes of phosphorus are delivered to the lagoon. The simulation results emphasize the role of heavy rainfall events and floods in the formation of the total nutrient load. The composition of aquatic bird communities has been used to assess the nutrient impact on the lagoon food-web. The Great Crested Grebe is apparently the species most closely dependant on local trophic conditions. The related Black-necked Grebe, that dominates the waterbird community of the lagoon, plays a similar role, but its more opportunistic response to changes in food resources, reduces its indicator value. The abundance of the two species of grebes seems to closely track the nitrogen load curve, especially during the first phase of enrichment, suggesting the existence of a direct trophic relationship. In the following phase, jellyfish blooms coincide with the bird decline. Jellyfishes seem to have a buffering effect towards nutrients, determining a bottom up limitation to other trophic compartments. In recent years, this buffering capacity has probably been overloaded, favouring the growth of new food resources available to the grebes. Unlike grebes, Mergus serrator, a typical piscivorous bird, does not seem to be affected positively by eutrophication since it shows a long-term stability in numbers or even a slight decline. Since this suspected decline would parallel a long-term reduction of fish catches, the species could be regarded as a potential indicator of habitat deterioration. [ABSTRACT FROM AUTHOR]

More than two-thirds of the human population of Alaska resides in the south-central portion of the state, where its continued growth is likely to affect some wildlife populations negatively. To assess changes in waterbird populations in this region, we compared counts of Common Loons (Gavia immer), Pacific Loons (G. pacifica), and Red-necked Grebes (Podiceps grisegena) made on Matanuska-Susitina Valley lakes. In general, the number of lakes occupied by loon or grebe pairs decreased between 1987 and 1999. Decreases in the number of lakes occupied by Common Loons were less drastic in the northwest region of the study area than in the southeast region; human development is greater in the southeastern portion of our study area. Contrary to lake occupancy, the percentage of lakes that fledged Common Loon chicks remained stable between years. Because the human population is expected to continue to grow, proactive management of lake use and lakeshore development, coupled with monitoring of loon and grebe occupancy and productivity, is needed to ensure the persistence of these waterbird populations in the lower Matanuska-Susitna Valley. [ABSTRACT FROM AUTHOR]

A Northern Goshawk (Accipiter gentilis) was twice observed hunting over the sea, close to shore, for small grebes (Podiceps spp.). Neither predation attempt was successful. Attacks on marine birds on the sea by goshawks are very rarely reported. [ABSTRACT FROM AUTHOR]

A list of unverified sightings of several bird species from early February to early March 2010 is presented including American waterbirds such as the Piedmont Grebes, a Pacific Diver, and a Common Elder all observed in Ireland.