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Ferrying, the behaviour in which waterbirds transport their offspring on their backs while in the water, is a captivating behaviour that wildlife photographers and filmmakers frequently highlight in calendars, wildlife documentaries, magazines and nature photography books. In the avian research sphere, however, only a handful of studies have investigated this behaviour, leaving much remaining to be understood about its evolution. One pattern that appears to emerge at a cursory glance is that the species that ferry tend to also be diving species. We sought to build a dataset of species that ferry and compare its occurrence to five ecological factors: diving, coloniality, territoriality, parental care type, and clutch size. Finally, we found that ferrying has originated at least four times within Anseriformes and has also been lost in two separate lineages of waterfowl. We suggest that a variety of avian life history factors may have influenced the evolution of ferrying behaviour and should be the focus of future research on this topic. [ABSTRACT FROM AUTHOR]

The Titicaca grebe (Rollandia microptera) is a poorly studied endangered species, only found in the Lake Titicaca watershed of Peru and Bolivia. Population surveys undertaken in the early twenty‐first century suggested that the species had declined in number by >70%. We conducted a population survey of the grebe between March and August 2022 in Peru and Bolivia, using both maximum entropy and Bayesian occupancy models to estimate factors affecting habitat suitability for the grebe. We conducted surveys between March and August 2022 in Peru and Bolivia. Contrary to the International Union for Conservation of Nature (IUCN) population estimates of <1,000 individuals, there are likely tens of thousands of individual grebes. The population estimation was sensitive to the type of model used. Distance from shore and fishing intensity were the most significant factors influencing grebe populations. The Reserva Nacional del Titicaca, the only protected area in the lake, covers some of the most suitable Titicaca grebe habitat across its entire range. The population of the Titicaca grebe is significantly higher than previous estimates, but we do not recommend a change to its conservation status because of the lack of conservation efforts for this species, and the long‐term risks associated with global warming and fisheries bycatch. [ABSTRACT FROM AUTHOR]

We estimated the abundance of Eared Grebes (Podiceps nigricollis) on Great Salt Lake (GSL) during 2009-2021 to determine how many Eared Grebes are on GSL throughout the year. Eared Grebes numbers averaged ~250,000 daily during the spring migration (April and May). During summer and winter, few Eared Grebes were on GSL, but they reappeared during the fall staging period when Eared Grebe numbers averaged 968,000 in September, 320,000 in October, and 524,000 in November. Our aerial counts underestimated the total number of Eared Grebes on GSL but still provided an accurate index for how their numbers vary throughout the year. From 2012 through 2021, 582 Eared Grebes were collected from GSL for another study, but the carcasses were analyzed for this study to determine morphological changes related to migration. Males outnumbered females, and adults were 4 times more common than juveniles. Males weighed 7% more than females, while adults and juveniles did not differ in mass. When Eared Grebes first arrived on GSL during August, they weighed 330-350 g, but mean body mass increased to 525 g by 16 October. In December, mean body mass declined to 474 g, liver mass by 72%, stomach mass by 56%, and stomach contents by 87% to reduce wing loading during migration. The morphological changes that we observed on GSL were similar to those observed among Eared Grebes on Mono Lake, California. [ABSTRACT FROM AUTHOR]

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]

A helminth fauna study of 398 waterfowl specimens belonging to 43 species living in southern Karelia wetlands (northwestern Russia) was conducted. This is the first time when data on the species composition and the infection of birds that are definitive hosts of Bilharziella polonica Schistosomatidae have been obtained. Bilharziella polonica has been recorded only in seven bird species, namely in the mallard, the Eurasia-n teal, the common goldeneye, the tufted duck, the northern shoveler, and the red-necked grebe; the infestation of the latter is noted in northwestern Russia for the first time. Of the bird species examined, this study describes the role of trematoda-infected birds in maintaining the focus of cercariosis, also known as "swimmer's itch," a disease pathogenic for humans. The data presented in our study indicates that the tremat-ode development cycle occurs successfully in the environment of Karelia. [ABSTRACT FROM AUTHOR]

Understanding the drivers of conflict and coexistence in human–wildlife relations are critical to conservation. This study sought to understand th varying attitudes of local indigenous people towards wildlife, focusing on the Titicaca Grebe (Rollandia microptera), an endangered endemic species found in Lake Titicaca and surrounding waters in the Altiplano of Peru and Bolivia. We used an ethnobiology approach to understand which demographic, sociocultural, and economic factors influenced (a) attitudes and local ecological knowledge (LEK) towards the grebe and (2) their effects on Indigenous–wildlife conflict or coexistence. We used a qualitative, semi-structured questionnaire to interview 221 individuals over six months in villages surrounding Lake Titicaca. Participants primarily consisted of locals from the Aymara, Quechan, and Uro Indigenous groups. We found that most individuals expressed apathy towards the grebe, with a significant minority being hostile towards it. Hostility was concentrated amongst fishers and was driven by economic concerns. Knowledge of the grebe was low in the general population, but higher amongst fishers. There was, however, widespread willingness to conserve the grebe amongst the general population, particularly when informed that the grebe is endemic to the Altiplano. This small environmental education intervention suggested increased positive attitudes and a willingness to conserve the grebe. Non-homogenous perspectives towards the grebe were held within and between indigenous groups, suggesting the need for future research into intra-indigenous group dynamics in indigenous–wildlife relations. Future conservation work on the Titicaca Grebe should focus on reducing grebe-fisher conflict, both real and perceived, and on educating people on the grebe's endemic status. [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]

In birds, pre-hatching calls are part of the communication behavior between parents and offspring, and may serve multiple functions. The Clark's Grebe (Aechmophorus clarkii) has a wide distribution in Mexico, and in 2015 we monitored a reproductive colony in the lagoon of Zumpango in central Mexico. We describe and measure the pre-hatching calls of two individuals from two different clutches. Eggs were about 22–25 days old. We obtained 5.16 minutes of recordings, with 81 calls made up by a frequency-modulated note and with an average call duration of 8.05 milliseconds and a peak dominant frequency of 828.20 Hertz (max 870.40; min 771.38). Calls were emitted at intervals of 1.38 seconds. This is the first description of pre-hatching calls in the Clark's Grebe, a poorly studied waterbird in Mexico. [ABSTRACT FROM AUTHOR]

To investigate the feeding behavior of the Western Grebe (Aechmophorous occidentalis), I observed the actions of one kept in a laboratory pool and fed fish of various sizes and in varying numbers during four trials per day. The grebe consumed fish under 4 cm in length underwater but brought all fish longer that 5 cm to the surface so they could be oriented for swallowing headfirst. The Western Grebe is likely gape-limited in its choice of fish and can only ingest prey that can be swallowed easily. [ABSTRACT FROM AUTHOR]

In 2022 two new colonies of Pallid Swift Apus pallidus were found in Brig VS and Geneva. For the first time a Red Kite Milvus milvus bred in the canton Ticino. The populations of Greylag Goose Anser anser (124 broods), White Stork Ciconia ciconia (887 broods), Great Cormorant Phalacrocorax carbo (3438 broods), Bearded Vulture Gypaetus barbatus (26 broods) und Short-toed Snake-eagle Circaetus gallicus (11 broods) have increased again in 2022. High breeding numbers were registered for Spotted Crake Porzana porzana (25 territories), Little Crake Zapornia parva (8 territories) und Zitting Cisticola Cisticola juncidis (12 territories), a low number for Corncrake Crex crex (16 singing males). Rare breeding records or reports of territories were found for: Common Eider Somateria mollissima (2 broods), Common Goldeneye Bucephala clangula (1 brood), Ferruginous Duck Aythya nyroca (1 brood), Black-necked Grebe Podiceps nigricollis (2 broods), Baillon's Crake Zapornia pusilla (1 territory), Eurasian Dotterel Eudromias morinellus (2 breeding pairs), Common Snipe Gallinago gallinago (1 territory), Mediterranean Gull Larus melanocephalus (1 brood), Mew Gull L. canus (1 breeding pair), Western Marsh-harrier Circus aeruginosus (3 broods), Moustached Warbler Acrocephalus melanopogon (1 territory), Subalpine Warbler Sylvia cantillans (1 brood), Spectacled Warbler S. conspicillata (1 territory), Tawny Pipit Anthus campestris (5 territories) and Citrine Wagtail Motacilla citreola (1 territory). An Arctic Tern Sterna paradisaea bred again together with a Common Tern S. hirundo. No territories were found for Grey Partridge Perdix perdix and Ortolan Bunting Emberiza hortulana. [ABSTRACT FROM AUTHOR]

The gut microbiota promotes host health by maintaining homeostasis and enhancing digestive efficiency. The gut microflora in wild birds affects host physiological characteristics, nutritional status, and stress response. The relict gull (Larus Relictus, a Chinese national first-class protected species) and the black-necked grebe (Podiceps Nigricollis, a secondary protected species) bred in the Ordos Relic Gull National Nature Reserve share similar feeding habits and living environments but are distantly related genetically. To explore the composition and differences in the gut microbiota of these two key protected avian species in Erdos Relic Gull National Nature Reserve and provide a basis for their protection, 16S rRNA gene high-throughput sequencing was performed and the gut microbial diversity and composition of the relict gull (L. Relictus) and black-necked grebe (P. Nigricollis) was characterized. In total, 445 OTUs (operational taxonomic units) were identified and classified into 15 phyla, 22 classes, 64 orders, 126 families, and 249 genera. Alpha diversity analysis indicates that the gut microbial richness of the relict gull is significantly lower than that of the black-necked grebe. Gut microbe composition differs significantly between the two species. The most abundant bacterial phyla in these samples were Proteobacteria, Firmicutes, Fusobacteria, and Bacteroidetes. The prominent phylum in the relict gull was Proteobacteria, whereas the prominent phylum in the black-necked grebe was Firmicutes. The average relative abundance of the 17 genera identified was greater than 1%. The dominant genus in the relict gull was Escherichia-Shigella, whereas Halomonas was dominant in the black-necked grebe. Microbial functional analyses indicate that environmental factors exert a greater impact on relict gulls than on black-necked grebes. Compared with the relict gull, the black-necked grebe was able to use food more efficiently to accumulate its nutrient requirements, and the gut of the relict gull harbored more pathogenic bacteria, which may be one reason for the decline in the relict gull population, rendering it an endangered species. This analysis of the gut microbial composition of these two wild avian species in the same breeding grounds is of great significance, offers important guidance for the protection of these two birds, especially relict gulls, and provides a basis for understanding the propagation of related diseases. [ABSTRACT FROM AUTHOR]

Birds foraging under water are collectively called diving birds. For example, the brown dipper, little grebe, common cormorant, tufted duck seen in rivers, ponds and lakes are classified into this category. Of course, penguins and shearwaters are typical of diving birds very familiar with us. High diving performance of the diving birds is expected to be useful for improving the performance of the current ships and developing new underwater vehicles. In this review article, the drag coefficient of the diving birds is introduced because it is one of key parameters for designing ships and underwater vehicles. [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]

A specimen of the Least Grebe (Tachybaptus dominicus bangsi) from San Francisco de la Sierra, Baja California Sur, Mexico, collected 6 April 2022, was 36 km north of the oasis of San Ignacio, where the species breeds and site of the previous northernmost records on the peninsula. The bird's occurrence on a small isolated pond yet coming into breeding condition highlight the species' opportunism, possibly critical to its survival on the arid Baja California peninsula where freshwater oases suitable for the Least Grebe are few. [ABSTRACT FROM AUTHOR]

Summary: The Lake Titicaca Grebe Rollandia microptera is a poorly studied endemic species found in the Lake Titicaca watershed of Peru and Bolivia. Multiple surveys from the early 2000s indicated that the species was suffering a rapid population decline with an unknown cause. At the same time as these surveys, reports emerged that there was an increase in burning of the totora wetlands which are thought to be the primary habitat for the Lake Titicaca Grebe. However, since 2003, no work has been published either on the current population of the Lake Titicaca Grebe, or the extent of the totora wetlands in the Lake Titicaca region. This paper used satellite data to monitor the change in extent of habitat potentially suitable for the Lake Titicaca Grebe to determine whether habitat loss is likely to be a major driver of population declines in this species. We found that the extent of potentially suitable wetland remained stable between 2001 and 2020, though there are more local regional trends of change in extent of totora. We also found that multiple areas exist that might support Lake Titicaca Grebe populations, but where ornithological knowledge is lacking. We suggest no change to the IUCN status of the Lake Titicaca Grebe, but recommend that further fieldwork is required to monitor the species' current population, especially in previously unstudied but potentially habitable areas. [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]

Copyright of Ornitologia Colombiana is the property of Asociacion Colombiana de Ornitologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

The populations of White Stork Ciconia ciconia, Great Cormorant Phalacrocorax carbo, Eurasian Scopsowl Otus scops, Short-toed Snake-eagle Circaetusgallicus and European Bee-eater Merops apiaster have increased again in 2021. High breeding numbers were registered for Spotted Crake Porzanaporzana (22 territories), Purple Heron Ardeapurpurea (15 pairs), Zitting Cisticola Cisticola juncidis (11 territories) and Common Rosefinch Carpodacus erythrinus (52). Rare breeding records or reports of territories were found for: Ferruginous Duck Aythya nyroca (1), Common Teal Anas crecca (1), Black-necked Grebe Podiceps nigricollis (2), Eurasian Dotterel Eudromias morinellus (1), Mediterranean Gull Larus melanocephalus (1 brood), Western Marsh-harrier Circus aeruginosus (3), Greenish Warbler Phylloscopus trochiloides (1 territory), Cetti's Warbler Cettia cetti (2), Subalpine Warbler Sylvia cantillans (1) and Spectacled Warbler S. conspicillata (1). For the first time since its reintroduction, a pair of Bearded Vultures Gypaetus barbatus has nested in Ticino. The number of breeding records of Red-crested Pochard Netta rufina, Tufted Duck Aythya fuligula and Gadwall Anas strepera was considerably lower than in previous years. The Corncrake Crex crex population was very low. An Arctic Tern Sterna paradisaea bred again together with a Common Tern S. hirundo. [ABSTRACT FROM AUTHOR]

The use of a netgun combined with other techniques facilitated the live capture of the Western Grebe Aechmophorus occidentalis occupying a shallow water harbor, with boat traffic, and abundant underwater structure. Transportability and adaptability rendered the netgun an effective tool, in this constrained environment. Haul-out structures such as nests were absent and grebes remained either swimming or floating, throughout their duration. Therefore, in-water access was imperative. Upon capture, grebes were then kept in captivity, to conduct in-laboratory investigations. An undertaking such as this has not been reported before. No grebes were injured during this procedure and capture rate was considered good. [ABSTRACT FROM AUTHOR]

Copyright of Revista de Biologia Marina y Oceanografía (RBMO) is the property of Universidad de Valparaiso, Facultad de Ciencias del Mar and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Understanding important factors for breeding Eared Grebes (Podiceps nigricollis) is essential for its conservation. We aimed to study the impact of some factors on nests and breeding success in this species in fishponds (S Poland). Number of Eared Grebe nests were counted on particular carp ponds. Pond size, vegetation cover, number of nests in colonies of associated gull or tern species, and age of stocked common carp (Cyprinus carpio) were determined for all ponds with nests. We also investigated the relationship between nest size, material used to construct them and clutch size. Number of Eared Grebe nests positively correlated with number of breeding pairs of associated colonial species (terns or gulls). Selection of the breeding site by the Eared Grebe can be explained by appropriate nest protection by large colonies of associated species (Whiskered Tern Chlidonias hybrida and Black-headed Gull Chroicocephalus ridibundus). Nest size was not related to clutch size. A negative relationship between breeding success and number of nests of Eared Grebe was found. Food is a not limiting factor for the Eared Grebe on fishponds with extensive production, and presumably other factors such as weather conditions may explain the low breeding success of this species. [ABSTRACT FROM AUTHOR]

Copyright of Revista Musical Chilena is the property of Universidad de Chile and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Field Ornithology is the property of Resilience Alliance and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

The Hooded Grebe is an endangered and endemic species of Podicipediformes of Argentina. Many aspects of this bird's biology are still unknown including the uropygial gland. This is the first morphological and histochemical description of the uropygial gland for this species in a comparative context. The uropygial gland of these birds had parallel arranged lobes with a kidney‐like shape, a conical papilla and a feather tuft in a sub‐terminal position. The lobes were composed of tubular adenomers with a straight course that lead to secondary chambers. The capsule and connective tissue around the adenomers had elastic fibres. It showed a positive reaction to AlcianBlue/Periodic Acid Schiff and several lectins indicating the presence of glycoconjugates. The uropygial gland of the Hooded Grebe shares morphological characteristics with other aquatic species (e.g. secondary chambers) and the presence of glycoconjugates might suggest protective functions against microbes as previously proposed. The sub‐terminal position of the feather tuft is a unique characteristic of this species indicating that this position leaves the tuft in a dorsal location and could be involved in parent‐chick recognition mediated by odour transmission. Further studies are needed to increase our knowledge on some behavioural aspects of this species related to the biochemical composition of the uropygial secretion. [ABSTRACT FROM AUTHOR]

Clear Lake is a large (176.7-km²) natural lake in northern California, USA. An estimated 1000 pairs of Western Grebes (Aechmophorus occidentalis) and Clark's Grebes (A. clarkii) nested on the lake prior to massive applications of the pesticide dichlorodiphenyldichloroethane (DDD) to kill the Clear Lake gnat (Chaoborus astictopus) during 1949-1957. Biomagnification of DDD was implicated as the cause of several mass mortality events of grebes and short-term reproductive failure in the 1950s, although other factors such as mercury (Hg) poisoning may have contributed. Successful nesting resumed in 1960 and increased gradually, with up to 165 nests in 1967 but fewer through 1976. Subsequent surveys revealed up to 390 nests annually during 1992-1995 and up to 2675 nests annually during 1996-2010. We conducted 7-29 nest surveys annually during 2010-2019 and found a mean of 3123 nests per year. The annual number of nests varied dramatically (range 898 to 5936) and was unrelated to water level. The grebes nested at 28 sites in Clear Lake and 9 sites in associated wetlands, with proportionately more nests on Clear Lake and fewer nests in adjacent wetlands during years with low water level. Western Grebes attended 84.9% of the nests and Clark's Grebes attended 15.1%. During years with low water, there were proportionately more open water nests, which were anchored to submergent vegetation farther from shore and in deeper water than marsh nests, which were more densely placed in emergent vegetation closer to shore in shallower water. Brood surveys along the perimeter of the lake at the end of each breeding season revealed considerable variation in the number of young (1-599, ... = 153.9), young per nest (0.00025-0.118, ... = 0.04), and productivity ratio of young to adults (0.0006-0.252, ... = 0.07). Reproductive success was unrelated to water level. Wind-generated waves were a major cause of nest failure, destroying up to 35% of a year's nests. Predation on eggs was also a major cause of nest failure. American Crow (Corvus brachyrhynchos) was the dominant predator during the day (84% of predation events), and northern raccoon (Procyon lotor) was the dominant predator at night (98% of predation events). Nocturnal predation by mammals occurred most frequently when water level was high because nests were placed closer to shore and were more accessible. The grebes' breeding population has recovered since DDD biomagnification during the 1950s and may be larger due to 2 introduced fish species competing for plankton with benthic larvae of the Clear Lake gnat, which previously transferred large quantities of biomass from aquatic to terrestrial ecosystems during emergence. However, the grebes' reproductive success remains lower at Clear Lake than at several other breeding localities. The bioaccumulation and biomagnification of toxic chemicals and the periodic reductions of prey fish from hypoxic areas of the lake during periods of intense cyanobacterial and algal blooms may reduce reproductive success. [ABSTRACT FROM AUTHOR]

In 2008, we investigated the relationships between the hatching success of the Little Grebe Tachybaptus ruficollis with egg laying onset, nest diameter, as a proxy of nest size, and egg weight, as a proxy of egg size, in an artificial wetland in Mazandaran Province, northern Iran. The first egg was laid on April 23 and the last chick hatched on July 27. From 118 eggs on 25 nests, we recorded a total of 72 hatchlings (hatching rate: 61%). A generalized linear model (GLM) revealed that while egg size and nest diameter were not significant factors predicting hatching success, egg laying onset predicted significantly the hatching success as early breeders were likely to produce less hatchlings than late breeders. Further studies will be necessary to elucidate the underlying mechanisms of such results. [ABSTRACT FROM AUTHOR]

This study established cloacal temperature (TCl) cut-off values to diagnose hypothermia in near shore seabirds rescued along the coast of California. All birds died when TCl was < 38.2 °C. When Aechmophorus grebes were excluded, 100% died when TCl was < 38.4 °C. Mortality increased 2-3× when TCl was lower than receiver operating curve-determined criteria for diagnosing hypothermia based on attitude: < 38.8 °C for mixed species, < 39.1 °C for Common Murres Uria aalge, and < 38.2 °C for Aechmophorus grebes. Reductions in TCl as small as 1.0 °C had significant physiologic effects. [ABSTRACT FROM AUTHOR]

Communication is generally assumed to be the domain of conspecific signallers and receivers that produce reliable signals and respond adaptively. However, interactions between coexisting species can be surprisingly complex, suggesting that animals not only perceive but also selectively respond to signals produced by other species. Many species respond to the vocalisations of heterospecifics, but it is usually difficult to separate actual vocal recognition from the response resulting from misidentification. We controlled this bias in a playback experiment with two sympatric Rallidae species, the water rail (Rallus aquaticus) and little crake (Zapornia parva). Both focal species produced more calls and little crake additionally approached the speaker more often in response to calls of each other than to calls of closely related but non‐sympatric spotted crakes (Porzana porzana) or the sympatric but non‐competing little grebes (Tachybaptus ruficollis). By contrast, when responding to each other's calls water rails produced fewer loud calls than during the conspecific treatment suggesting that focal birds were merely announcing their presence, whereas little crakes produced mainly alarms suggesting that they communicated with the mated partner to warn it rather than with the heterospecific intruder. We conclude that focal Rallidae species could distinguish not only their calls from those of conspecifics, but also each other's calls from those of other sympatric and phylogenetically related species. [ABSTRACT FROM AUTHOR]

Grebe syndrome is a rare genetic condition characterised by short limb dwarfism. It is transmitted by autosomal mode of inheritance. There are no associated anomalies and the affected child has normal intelligence and normal life span. This syndrome has a very low incidence and needs to be differentiated from other forms of short limb dwarfism since treatment options may vary. We have described here a severely affected case of the same with review of literature. [ABSTRACT FROM AUTHOR]

The effects of season, location, species, and sex on body weight and a comprehensive array of blood chemistry and hematology analytes were compared for free-ranging western (Aechmophorus occidentalis) and Clark's (Aechmophorus clarkii) grebes. Birds (n = 56) were collected from Puget Sound, WA, and Monterey Bay and San Francisco Bay, CA, from February 2007 to March 2011. The data supported generalization of observed ranges for most analytes across Aechmophorus grebe metapopulations wintering on the Pacific coast. Notable seasonal and location effects were observed for packed cell volume (winter 6% greater than fall; winter California [CA] 5% greater than Washington [WA]), total white blood cell count (CA 3.57 × 103 cells/µL greater than WA), heterophils (WA 10% greater than CA), lymphocytes (winter 19% greater than fall), heterophil to lymphocyte ratio (fall 5.7 greater than winter), basophils (CA greater than WA), plasma protein (WA about 10 g/L [1.0 g/dL] greater than CA), plasma protein to fibrinogen ratio (winter about 15 greater than fall), potassium (CA 2 mmol/L greater than WA), and liver enzymes (alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase: WA greater than CA). Within California, season had a greater effect on body mass than sex (mean winter weights about 200 g greater than fall), whereas within a season, males weighed only about 80 g more than females, on average. These data give biologists and veterinarians quantitative reference values to better assess health at the individual and metapopulation level. [ABSTRACT FROM AUTHOR]