Belly-soaking: A behavioural solution to reduce excess body heat in the Kentish plover Charadrius alexandrinus

During nesting, many temperate and tropical shorebirds are exposed to direct solar radiation and face heat stress. The aim of our study was to determine whether belly-soaking (wetting of ventral plumage) contributes to reducing excess body heat in Kentish plovers Charadrius alexandrinus. We captured incubating plovers on sunny days at their exposed nests, and placed them inside cloth bags at ground level in exposed sites for 5 min. This produced an increase in the ambient temperature experienced by the plovers, as well as an increase in the body temperature of the plovers. We simulated belly-soaking by submerging the ventral parts in water for about 10 s immediately after removing the birds from the bag. The body temperature of the plovers was lowered after simulated belly-soaking. Our results indicate that belly-soaking is a behavioural strategy to quickly reduce body temperature in heat-stressed plovers. © Japan Ethological Society and Springer 2008.Peer Reviewe

Sex-related seasonal differences in the foraging strategy of the Kentish Plover

In species of birds with biparental care, each sex may have its own energy requirements and/or schedule for feeding, possibly leading the sexes to differ in foraging strategy. In estuaries, shorebirds such as the Kentish Plover (Charadrius alexandrinus alexandrinus) may forage on intertidal mudflats and in adjacent su- pratidal habitats during winter as well as during the breeding season. In this study, we analyzed the diet, use of foraging habitat, food-intake rate (biomass ingested per unit time), and time allocated to foraging by male and female Kentish Plovers at both seasons in an estuary near Cádiz, Spain, where intertidal mudflats and adjacent salt works are the main habitats for foraging. The plovers’ main prey was the ragworm (Nereis diversicolor), an intertidal polychaete that supplied more than 80% of the biomass consumed at each season. During the breeding season, both sexes increased their intake rate and decreased their daylight foraging time. By increasing the diurnal intake rate during the breeding season, the birds minimized their time spent foraging on the intertidal mudflats, allowing them to maximize the time for activities associated with breeding in the adjacent salt works. Therefore, the plovers solved the conflict between foraging on the mudflats and breeding in the salt works by shortening the foraging time on the mudflats, minimizing time away from the nesting areas. The sexes differed in the daylight time allocated to foraging, with females spending 2 hr less on foraging and concentrating their feeding activity into the central hours of low tideEn especies de aves con cuidado biparental, cada sexo puede tener sus propios requerimientos de energía y/o esquema de tiempo para la alimentación, lo cual podría conducir a diferencias en las estrategias de alimentación entre ambos sexos. En los estuarios, las especies de playeros como Charadrius alexandrinus pueden forrajear en fangos intermareales y en hábitats supramareales adyacentes tanto durante el invierno así como du- rante la época reproductiva. Aquí, analizamos la dieta, el uso de hábitat de forrajeo, la tasa de ingestión (biomasa ingerida por unidad de tiempo) y el tiempo dedicado al forrajeo por el macho y la hembra de C. alexandrinus du- rante ambas temporadas en una zona estuarina donde los fangos intermareales y las salinas adyacentes son las principales áreas de alimentación. La principal presa para C. alexandrinus fue un poliqueto (Nereis diversicolor), una presa intermareal que suplió más del 80% de la biomasa consumida en cada estación. Ambos sexos incremen- taron sus tasas de alimentación durante la época reproductiva, y disminuyeron sus tiempos diurnos de forrajeo. Por el incremento de la tasa de ingestión durante la época reproductiva, las aves minimizaron el tiempo que pasaron en los fangos intermareales, lo que les permitió maximizar el tiempo dedicado a las actividades de reproducción en las salinas adyacentes. Por lo tanto, el conflicto entre alimentarse en los fangos versus el desarrollo de las ac- tividades de reproducción (en las salinas), fue resuelto acortando el tiempo en los fangos, minimizando el tiempo fuera de las zonas de nidada. Hubo diferencias relacionadas con el sexo en el tiempo diurno dedicado al forrajeo: las hembras dedicaron dos horas menos a la alimentación y concentraron su actividad de alimentación en las horas centrales de la marea baja

Artificial wetlands as breeding habitats for shorebirds:A case study on Pied Avocets in China’s largest saltpan complex

Artificial wetlands such as coastal saltpans have replaced a number of coastal natural habitats worldwide and may have accommodated specific waterbird populations in the East Asian–Australasian Flyway (EAAF). The role of saltpans in the EAAF as foraging grounds for shorebirds is widely recognized, although their role as breeding grounds for waterbirds is very limited and contradictory. The Nanpu saltpans in northern Bohai Bay, China, are one of the largest saltpan complexes in the world. In this study, we monitored the nesting success (852 nests) of pied avocets (Recurvirostra avosetta) during three breeding seasons (2015, 2016, and 2018) in the Nanpu saltpans. The nest daily survival rate (DSR) was 0.970; hence, nest survival over the 27 exposure days was 44%. The apparent nest success was 51%. Surprisingly, 55% of nests failed during the laying period. Flooding and nest abandonment were the main causes of nest failure during both the laying and incubation periods. We found a strong positive relationship between the DSR and nest age, with nests that approached hatching having a greater probability of survival than freshly started nests. We also found a strong negative relationship between the DSR and precipitation, with the highest DSR observed for nests that experienced no precipitation. The DSR decreased over the course of the 71-days nesting season and followed a linear trend. The DSR was also density dependent and decreased slightly when nests were denser. A literature review showed that nest survival in the Nanpu saltpans was average compared with that of other studies and that nest success in artificial wetlands was significantly higher than that in natural wetlands or both habitats. Nevertheless, nest success decreased with the study date, suggesting that that breeding conditions for the pied avocet are worsening with time. The loss of saltpans could negatively affect the population of avocets and other ground-nesting waterbird species; therefore, conservation actions and research efforts should be strengthened to understand and conserve these functional wetlands for waterbirds

Urohidrosis as an overlooked cooling mechanism in long-legged birds

Behavioural thermoregulation could buffer the impacts of climate warming on vertebrates. Specifically, the wetting of body surfaces and the resulting evaporation of body fluids serves as a cooling mechanism in a number of vertebrates coping with heat. Storks (Ciconiidae) frequently excrete onto their legs to prevent overheating, a phenomenon known as urohidrosis. Despite the increasingly recognised role of bare and highly vascularised body parts in heat exchange, the ecological and evolutionary determinants of urohidrosis have been largely ignored. We combine urohidrosis data from a scientifically curated media repository with microclimate and ecological data to investigate the determinants of urohidrosis in all extant stork species. Our phylogenetic generalised linear mixed models show that high temperature, humidity and solar radiation, and low wind speed, promote the use of urohidrosis across species. Moreover, species that typically forage in open landscapes exhibit a more pronounced use of urohidrosis than those mainly foraging in waterbodies. Substantial interspecific variation in temperature thresholds for urohidrosis prevalence points to different species vulnerabilities to high temperatures. This integrated approach that uses online data sources and methods to model microclimates should provide insight into animal thermoregulation and improve our capacity to make accurate predictions of climate change’s impact on biodiversityinfo:eu-repo/semantics/publishedVersio

Metabolic plasticity for subcutaneous fat accumulation in a long-distance migratory bird traced by 2 H 2 O

The migrant black-tailed godwit (Limosa limosa) traditionally used natural wetlands in the Iberian Peninsula to prepare for migratory flights by feeding mainly in estuaries. In recent decades, this species has become increasingly dependent on rice fields, thereby relying on a plant-based diet for fuelling. Dietary fatty acids (FA) seem to be determinant to the composition of accumulated subcutaneous fat in migratory birds. It is still unclear whether metabolic plasticity allows for modification and/or synthesis of FA, contributing to a lipid profile that enables a successful migratory performance. Deuterated water was administered to captive black-tailed godwits submitted to two diets (fly larvae versus rice) and the incorporation of deuterium (2H) into subcutaneous triglycerides was analyzed by NMR. A recently developed localized biopsy method for sampling subcutaneous fat was employed with later successful release of all birds into the wild. The average chemical structure reflected mostly a mixture of saturated and monounsaturated 16- and 18-carbon FA, a profile frequently found in migrant birds. Significantly higher levels of polyunsaturated FA, as well as detectable levels of n-3 FA, were observed in fly-larvae-fed birds. Excess 2H-enrichments in FA revealed significantly higher rates of fractional de novo lipogenesis and FA desaturation capacity in rice-fed birds. This novel and non-lethal tracer method revealed the capacity of this species to alter its lipid metabolism to compensate for a poorer dietary lipid contribution. Because of its versatility, adapting this method to other scenarios and/or other migratory species is considered feasible and cost-effective.The authors acknowledge financial support from Fundacao para a Ciencia e Tecnologia (FCT) in the form of fellowships to I.V. (SFRH/BPD/90032/2012), P.M.A. (SFRH/BD/69238/2010), A.D.R. (SFRH/BD/74228/2010) and J.A.A. (SFRH/BPD/91527/2012) and research project EXCL/DTP-PIC/0069/2012. NMR data were collected at the UC-NMR facility that is supported by FEDER and FCT (RECI/QEQ-QFI/0168/2012, CENTRO-07-CT62-FEDER-002012) and Rede Nacional de Ressonancia Magnetica Nuclear (RNRMN).Peer Reviewe

How salinity and temperature combine to affect physiological state and performance in red knots with contrasting non-breeding environments

Migratory shorebirds inhabit environments that may yield contrasting salinity-temperature regimes-with widely varying osmoregulatory demands, even within a given species-and the question is: by which physiological means and at which organisational level do they show adjustments with respect to these demands? Red knots Calidris canutus winter in coastal areas over a range of latitudes. The nominal subspecies winters in salty areas in the tropics, whereas the subspecies Calidris canutus islandica winters in north-temperate regions of comparatively lower salinities and temperatures. In this study, both subspecies of red knot were acclimated to different salinity (28/40 ‰)-temperature (5/35 °C) combinations for 2-week periods. We then measured food/salt intakes, basal metabolic rate (BMR), body mass and temperature, fat and salt gland scores, gizzard mass, heat-shock proteins, heterophils/lymphocytes (H/L) ratio and plasma Na(+) to assess the responses of each taxon to osmoregulatory challenges. High salinity (HS)-warm-acclimated birds reduced food/salt intake, BMR, body mass, fat score and gizzard mass, showing that salt/heat loads constrained energy acquisition rates. Higher salt gland scores in saltier treatments indicated that its size was adjusted to higher osmoregulatory demands. Elevated plasma Na(+) and H/L ratio in high-salinity-warm-acclimated birds indicated that salt/heat loads might have a direct effect on the water-salt balance and stress responses of red knots. Subspecies had little or no effect on most measured parameters, suggesting that most adjustments reflect phenotypic flexibility rather than subspecific adaptations. Our results demonstrate how salinity and temperature affect various phenotypic traits in a migrant shorebird, highlighting the importance of considering these factors jointly when evaluating the environmental tolerances of air-breathing marine taxa

Population overlap and habitat segregation in wintering Black-tailed Godwits Limosa limosa

Distinct breeding populations of migratory species may overlap both spatially and temporally, but differ in patterns of habitat use. This has important implications for population monitoring and conservation. To quantify the extent to which two distinct breeding populations of a migratory shorebird, the Black-tailed Godwit Limosa limosa, overlap spatially, temporally and in their use of different habitats during winter. We use mid-winter counts between 1990 and 2001 to identify the most important sites in Iberia for Black-tailed Godwits. Monthly surveys of estuarine mudflats and rice-fields at one major site, the Tejo estuary in Portugal in 2005-2007, together with detailed tracking of colour-ringed individuals, are used to explore patterns of habitat use and segregation of the Icelandic subspecies L. l. islandica and the nominate continental subspecies L. l. limosa. In the period 1990-2001, over 66 000 Black-tailed Godwits were counted on average in Iberia during mid-winter (January), of which 80% occurred at just four sites: Tejo and Sado lower basins in Portugal, and Coto Dontildeana and Ebro Delta in Spain. Icelandic Black-tailed Godwits are present throughout the winter and forage primarily in estuarine habitats. Continental Black-tailed Godwits are present from December to March and primarily use rice-fields. Iberia supports about 30% of the Icelandic population in winter and most of the continental population during spring passage. While the Icelandic population is currently increasing, the continental population is declining rapidly. Although the estuarine habitats used by Icelandic godwits are largely protected as Natura 2000 sites, the habitat segregation means that conservation actions for the decreasing numbers of continental godwits should focus on protection of rice-fields and re-establishment of freshwater wetlands

Understanding how birds rebuild fat stores during migration: insights from an experimental study

Publisher's version (útgefin grein).Mechanisms underlying fat accumulation for long-distance migration are not fully understood. This is especially relevant in the context of global change, as many migrants are dealing with changes in natural habitats and associated food sources and energy stores. The continental Black-tailed godwit Limosa limosa limosa is a long-distance migratory bird that has undergone a considerable dietary shift over the past few decades. Historically, godwits fed on an animal-based diet, but currently, during the non-breeding period godwits feed almost exclusively on rice seeds. The latter diet may allow building up of their fuel stores for migration by signifcantly increasing de novo lipogenesis (DNL) activity. Here, we performed an experiment to investigate lipid fux and the abundance of key enzymes involved in DNL in godwits, during fasting and refueling periods at the staging site, while feeding on rice seeds or fy larvae. Despite no signifcant diferences found in enzymatic abundance (FASN, ME1, ACC and LPL) in stored fat, experimental godwits feeding on rice seeds presented high rates of DNL when compared to fy-larvae fed birds (~35 times more) and fasted godwits (no DNL activity). The increase of fractional DNL in godwits feeding on a carbohydrate-rich diet can potentially be enhanced by the fasting period that stimulates lipogenesis. Although requiring further testing, these recent fndings provide new insights into the mechanisms of avian fat accumulation during a fasting and refueling cycle and associated responses to habitat and dietary changes in a migratory species.Te authors acknowledge fnancial support from Fundação para a Ciencia e Tecnologia (FCT) in the form of fellowships to PMA (SFRH/BD/69238/2010), IV (SFRH/BPD/90032/2012) and JAA (SFRH/BPD/91527/2012) and research Project CGL2017-89009-P. NMR data were collected at the UC-NMR facility that is supported by FEDER and FCT (RECI/QEQ-QFI/0168/2012, CENTRO-07-CT62-FEDER-002012) and Rede Nacional de Ressonancia Magnética Nuclear (RNRMN). Tis study benefted from funding by the strategic program of MARE, fnanced by FCT (UID/MAR/04292/2019), and by FTC/MCTES to CESAM, (UID/AMB/50017 – POCI01-0145-FEDER-007638), through national funds.Peer Reviewe