Juan G. Navedo

Avian BMR in marine and non-marine habitats: a test using shorebirds.

Basal metabolic rate (BMR) is closely linked to different habitats and way of life. In birds, some studies have noted that BMR is higher in marine species compared to those inhabiting terrestrial habitats. However, the extent of such metabolic dichotomy and its underlying mechanisms are largely unknown. Migratory shorebirds (Charadriiformes) offer a particularly interesting opportunity for testing this marine–non-marine difference as they are typically divided into two broad categories in terms of their habitat occupancy outside the breeding season: ‘coastal’ and ‘inland’ shorebirds. Here, we measured BMR for 12 species of migratory shorebirds wintering in temperate inland habitats and collected additional BMR values from the literature for coastal and inland shorebirds along their migratory route to make inter- and intraspecific comparisons. We also measured the BMR of inland and coastal dunlins Calidris alpina wintering at a similar latitude to facilitate a more direct intraspecific comparison. Our interspecific analyses showed that BMR was significantly lower in inland shorebirds than in coastal shorebirds after the effects of potentially confounding climatic (latitude, temperature, solar radiation, wind conditions) and organismal (body mass, migratory status, phylogeny) factors were accounted for. This indicates that part of the variation in basal metabolism might be attributed to genotypic divergence. Intraspecific comparisons showed that the mass-specific BMR of dunlins wintering in inland freshwater habitats was 15% lower than in coastal saline habitats, suggesting that phenotypic plasticity also plays an important role in generating these metabolic differences. We propose that the absence of tidally-induced food restrictions, low salinity, and less windy microclimates associated with inland freshwater habitats may reduce the levels of energy expenditure, and hence BMR. Further research including common-garden experiments that eliminate phenotypic plasticity as a source of phenotypic variation is needed to determine to what extent these general patterns are attributable to genotypic adaptation.

Assessing the role of multiple environmental factors on Eurasian Spoonbill departure decisions from stopover sites

Understanding the factors driving departure decisions from stopover sites is critical when predicting the dynamics of bird migration. We Investigated the Interactive effects of wind, tidal characteristics, and precipitation on the departure decisions of the Eurasian Spoonbill Platalea l. leucorodia from a major coastal stopover locality in northern Iberia. Most departing Spoonbills (>80%) crossed an adjacent mountain range to follow a direct route over Inland Iberia, while the remainder made a detour following an Indirect coastal route along the coast of the Iberian Peninsula. During four consecutive autumns, we daily monitored departing Spoonbills leaving along these two routes. The birds taking the Inland route, crossing unsuitable habitats and needing therefore higher fuel-loads, departed preferentially under favourable tailwind conditions (TWC). This represented a significant increase in distance covered and/or a decrease in energy spent per unit time. Moreover, Spoonbills taking the inland route often departed during spring tides. For the indirect coastal route, TWC did not affect the onset of migration but bird departures increased with neap tides. Precipitation and date were negatively correlated with departures towards both routes, whereas Spoonbill density at the stopover had a positive effect. Our findings provide empirical support for the role that wind assistance may play for Spoonbills to resume migration.

International importance of Extremadura, Spain, for overwintering migratory dabbling ducks: a role for reservoirs.

Many migratory waterbird populations are in decline and loss of natural wetlands is one of the main causes.However, some speciesmay respondpositively to artificial wetland recreation. In Extremadura (south-west Europe), several large reservoirs were created for irrigation since the 1960s and some comparatively small reservoirs were built from the late 1990s onwards close to rice fields. Here we analyse the abundance of wintering dabbling ducks (Anas spp.) in Extremadura before (1991–1994) and after (2007–2010) the creation of these new reservoirs in order to address the current importance of the area for this guild within the East Atlantic Flyway (EAF). A mean of 25,277 dabbling ducks wintered in the study area during 1991–1994, increasing to 46,163 individuals during 2007–2010. After controlling for environmental variables, Northern Pintail Anas acuta, Common Teal A. crecca and Northern Shoveler A. clypeata experienced significant increases in the area between both periods, and only Eurasian Wigeon A. penelope suffered a significant decrease. Mallard A. platyrhynchos and Gadwall A. strepera populations did not show any significant trend. The large older reservoirs experienced overall population decreases between the two periods, with four new reservoirs holding more than 35,000 wintering dabbling ducks. Our results reflect an overall improvement in habitat conditions, driven by the creation of reservoirs near to rice fields that could have resulted in a partial redistribution of wintering dabbling ducks in the EAF. The area emerges as one of the most important wintering sites for dabbling ducks in southern Europe, regularly exceeding two of the Ramsar Convention criteria for the conservation of several populations. The protection of these new reservoirs by legal mechanisms would guarantee the existence of a large functional wetland area, which could also mitigate the loss of natural wetlands for populations using the EAF.

Latitudinal-related variation in wintering population trends of greylag geese (Anser Anser) along the Atlantic flyway: A response to Climate Change?

The unusually high quality of census data for large waterbirds in Europe facilitates the study of how population change varies across a broad geographical range and relates to global change. The wintering population of the greylag goose Anser anser in the Atlantic flyway spanning between Sweden and Spain has increased from 120 000 to 610 000 individuals over the past three decades, and expanded its wintering range northwards. Although population sizes recorded in January have increased in all seven countries in the wintering range, we found a pronounced northwards latitudinal effect in which the rate of increase is higher at greater latitudes, causing a constant shift in the centre of gravity for the spatial distribution of wintering geese. Local winter temperatures have a strong influence on goose numbers but in a manner that is also dependent on latitude, with the partial effect of temperature (while controlling for the increasing population trend between years) being negative at the south end and positive at the north end of the flyway. Contrary to assumptions in the literature, the expansion of crops exploited by greylag geese has made little contribution to the increases in population size. Only in one case (expansion of winter cereals in Denmark) did we find evidence of an effect of changing land use. The expanding and shifting greylag population is likely to have increasing impacts on habitats in northern Europe during the course of this century.

Foraging Activity and Capture Rate of Large Nearctic Shorebirds Wintering at a Tropical Coastal Lagoon

Abstract. Winter foraging ecology of Marbled Godwit (Limosa fedoa), Long-billed Curlew (Numenius americanus), Whimbrel (Numenius phaeopus) and Willet (Tringa semipalmata) was studied in relation to conspecific density at Estero de Urías, a tropical coastal lagoon in northwestern Mexico. Specifically, the effect of ecological factors in relation to individual prey capture rates for Marbled Godwits and both Numenius spp. was examined. There was a consistent, inverse relationship between conspecific density and foraging activity, but the slope differed among species. The inverse relationship suggests that conspecific density was an important determinant of individual foraging behavior and habitat use across species. For Marbled Godwits, prey capture rate was positively correlated with conspecific density and water depth, but negatively correlated with tidal height, at least during spring tides. In contrast, for both Numenius spp., prey capture rate was significantly higher for territorial birds and tactile foragers, in the case of Curlews, but was independent of tidal conditions. When neap tides resulted in reduced foraging time budget, Marbled Godwits increased prey capture rate, but Numenius spp., did not. Differences in foraging mode, availability of preferred prey in relation to water depth, as well as handling time of prey, could drive these distinct patterns between godwits and both Numenius spp. These results support suggestions that the increased conspecific density during periods of neap tides might explain the reduced prey capture rate of individuals with less competitive ability, especially within large shorebirds showing a sparse foraging distribution.

Time Course and Metabolic Costs of a Humoral Immune Response in the Little Ringed Plover Charadrius dubius

Despite host defense against parasites and pathogens being considered a costly life-history trait, relatively few studies have assessed the energetic cost of immune responsiveness. Knowledge of such energetic costs may help to understand the mechanisms by which trade-offs with other demanding activities occur. The time course and associated metabolic costs of mounting a primary and secondary humoral immune response was examined in little ringed plovers Charadrius dubius challenged with sheep red blood cells. As was expected, the injection with this antigen increased the production of specific antibodies significantly, with peaks 6 d postinjection in both primary and secondary responses. At the peak of secondary antibody response, the antibody production was 29% higher than that observed during the primary response, but the difference was nonsignificant. Mounting the primary response did not significantly increase the resting metabolic rate (RMR) of birds, whereas the secondary response did by 21%, suggesting that the latter was more costly in terms of RMR. In spite of the fact that the primary response did not involve an increase in RMR, birds significantly decreased their body mass. This could imply an internal energy reallocation strategy to cope with the induced immune challenge. Last, we found that RMR and antibody production peaks were not coupled, which could help to conciliate the variable results of previous studies. Collectively, the results of this study support the hypothesis that humoral immunity, especially the secondary response, entails energetic costs that may trade-off with other physiological activities.

Storm petrel's breeding skipping in response to oil-spill pollution : Raising concerns over Zabala et al. (2011) methodological approach

Storm petrels breeding skipping in response to oil-spill pollution : Raising concerns over Zabala et al. (2011) methodological approach

Chilean Atacama site imperilled by lithium mining

Coral reefs are again in the spotlight, having suffered mass mortality over the past two years from global bleaching events. Before reef resilience runs out, researchers must move beyond lamenting corals’ lost pristine state and develop pragmatic solutions. In our view, these are likely to stem from a more diverse set of stakeholders than have participated so far. We must ensure that reefs can continue to provide wellbeing for millions of people in the future, despite widespread alterations in their biological state. Degraded reefs still have the potential to provide fisheries benefits, cultural value and other sources of revenue (such as tourism), although all of these are likely to be reduced. With 2018 designated the International Year of the Reef, fresh perspectives and approaches are needed (S. A. Hewlett et al. Harvard Bus. Rev. 91, 30; 2013). New recruits should come from a greater variety of sectors (such as development, health and governance) and from a wider set of disciplines (such as the social sciences — including psychology, economics, political science and geography) than today’s conservationists. Young scientists and researchers from the global south will be particularly important contributors. Gabby Ahmadia* World Wildlife Fund, Washington DC, USA. gabby.ahmadia@wwfus.org *On behalf of 14 co-signatories (see go.nature.com/2kwzqk7 for full list).

Dispersal of little egrets Egretta garzetta from northern Spanish Atlantic colonies

Summary. We studied the movements of little egrets Egretta garzetta from breeding colonies in northern Spanish Atlantic estuaries using sighting data of colour-ringed birds. Data on 304 resightings of 95 out of 457 little egrets ringed as chicks in two colonies on the southern Bay of Biscay were analysed. Most egrets (68.9%) were observed less than 50 km from their natal colonies and thus exhibited low dispersal, supporting the view that these birds belong to a resident population breeding along the coasts of the Bay of Biscay. Nearly all resightings (95.5%) occurred in estuaries across an east-west axis corresponding to the Atlantic coast of northern Spain and had a west-biased dispersal direction. We suggest that the recently formed northern Atlantic Spanish population is a consequence of a westward colonisation pattern originating in the French Atlantic colonies.