Resultados de investigación

Increasing water extraction and climate change combine to increase the impact of droughts in Mediterranean wetlands. Natural wetlands are being increasingly transformed into artificial wetlands, notably ricefields and aquaculture ponds. Since waterbirds are highly dependent on aquatic resources throughout their life cycles, changes in wetland habitats can significantly affect their use and movements. Studies relying on count data can highlight the importance of artificial wetlands for waterbirds, but analysis of movements using GPS tracking data facilitates a full assessment of their value compared to natural wetlands. We used GPS-tracking to study the habitat use of nesting black-headed gulls, Chroicocephalus ridibundus, in the iconic Doñana wetlands in Spain. In this area, the flooding of remaining natural wetlands has been reduced by overextraction of groundwater and by prolonged drought, whereas adjacent fish ponds have maintained stable water levels. We tagged 65 adults, and studied habitat selection of nesting birds (n = 30 bird-years), combining flooding information from Landsat images with land-use maps. Size of colonies, fledging success and proportion of tagged birds that nested all increased in years of higher rainfall. In the wetter 2024, when flooded natural marshes were available, gull home ranges shifted to include those areas. When away from the nest, fish ponds were the preferred habitat in 2022 and 2023, and natural marshes in 2024. Although ricefields are used by gulls in winter they are almost unused during the nesting period. In the driest year 2022, home range sizes were smallest. But due to successive drought years, availability of freshwater habitats was even lower in 2023, and gulls responded to rainfall events by flying up to 54 km to exploit other, distant, temporarily flooded, agricultural habitats. The importance of artificial wetlands for waterbird conservation can be easily overestimated from count data alone. The value of extensive fish ponds as a breeding habitat depends on maintaining the availability of natural marshes as a foraging habitat. This requires reducing impacts from groundwater extraction. Given recent abandonment of aquaculture, some fish ponds should be restored into natural marshes, This work was funded by the European Union and Agencia Estatal de Investigación (PCI2021-121938/AEI/10.13039/501100011033), in the frame of the collaborative international consortium PAIRWISE financed under the ERA-NET AquaticPollutants Joint Transnational Call (GA N° 869178). This ERA-NET is an integral part of the activities developed by the Water, Oceans and AMR Joint Programming Initiatives. Yingjun Wang was funded by the Chinese Scholarship Council. Víctor Martín-Vélez was also funded with a Margarita Salas grant 2022 from funding Next Generation EU, This work contributes to the Institut de Ciències del Mar "Severo Ochoa Centre of Excellence" accreditation CEX2024-001494-S funded by AEI 10.13039/501100011033 of the Spanish Ministry of Science and Innovation, Peer reviewed

All versions are available at DOI 10.5281/zenodo.15792050, Peer reviewed

All versions are available at DOI 10.5281/zenodo.15792050, Peer reviewed

All versions are available at DOI 10.5281/zenodo.15792050, Peer reviewed

Maps showing all different kind of impacts on the Mediterranean Sea

Mapes sobre diferents tipus d’impactes en tot el Mar Mediterrani. Dades primàries (mapes) associades a un article acceptat per la revista Scientific Reports (2018). Publicat a: https://doi.org/10.1038/s41598-018-33237-w, Dades primàries (mapes) associades a un article publicat a la revista Scientific Reports, 2018, vol. 8. http://doi.org/10.1038/s41598-018-33237-w

Files contain information on flight parameters obtained from lesser kestrel (Falco naumanni) commuting flights or foraging trips (depending on the variable) and the mean values of those parameters per 6-hour interval. Data were collected using high-frequency GPS-dataloggers to track individual lesser kestrels from two breeding colonies in southern Spain. The study was conducted throughout the breeding season of 4 consecutive years (2011-2014). For additional information contact Jesús Hernández-Pliego, email: jhpliego@ebd.csic.es, Peer reviewed

Tri-axial accelerometry has proved to be a useful technique to study animal behavior with little direct observation, and also an effective way to measure energy expenditure, allowing a refreshing revisit to optimal foraging theory. This theory predicts that individuals should gain the most energy for the lowest cost in terms of time and energy when foraging, in order to maximize their fitness. However, during a foraging trip, central-place foragers could face different trade-offs during the commuting and searching parts of the trip, influencing behavioral decisions. Using the lesser kestrel (Falco naumanni) as an example we study the time and energy costs of different behaviors during the commuting and searching parts of a foraging trip. Lesser kestrels are small insectivorous falcons that behave as central-place foragers during the breeding season. They can commute by adopting either time-saving flapping flights or energy-saving soaring-gliding flights, and capture prey by using either time-saving active hovering flights or energy-saving perch-hunting. We tracked 6 lesser kestrels using GPS and tri-axial accelerometers during the breeding season. Our results indicate that males devoted more time and energy to flight behaviors than females in agreement with being the sex responsible for food provisioning to the nest. During the commuting flights, kestrels replaced flapping with soaring-gliding flights as solar radiation increased and thermal updrafts got stronger. In the searching part, they replaced perch-hunting with hovering as wind speed increased and they experienced a stronger lift. But also, they increased the use of hovering as air temperature increased, which has a positive influence on the activity level of the preferred prey (large grasshoppers). Kestrels maintained a constant energy expenditure per foraging trip, although flight and hunting strategies changed dramatically with weather conditions, suggesting a fixed energy budget per trip to which they adjusted their commuting and searching strategies in response to weather conditions, Peer reviewed

Global Positioning System (GPS) tags are nowadays widely used in wildlife tracking. This geolocation technique can suffer from fix loss biases due to poor satellite GPS geometry, that result in tracking data gaps leading to wrong research conclusions. In addition, new solar-powered GPS tags deployed on birds can suffer from a new “battery drain bias” currently ignored in movement ecology analyses. We use a GPS tracking dataset of bearded vultures (Gypaetus barbatus), tracked for several years with solar GPS tags, to evaluate the causes and triggers of fix and data retrieval loss biases. We compare two models of solar GPS tags using different data retrieval systems (Argos vs GSM-GPRS), and programmed with different duty cycles. Neither of the models was able to accomplish the duty cycle programed initially. Fix and data retrieval loss rates were always greater than expected, and showed non-random gaps in GPS locations. Number of fixes per month of tracking was a bad criterion to identify tags with smaller biases. Fix-loss rates were four times higher due to battery drain than due to poor GPS satellite geometry. Both tag models were biased due to the uneven solar energy available for the recharge of the tag throughout the annual cycle, resulting in greater fix-loss rates in winter compared to summer. In addition, we suggest that the bias found along the diurnal cycle is linked to a complex three-factor interaction of bird flight behavior, topography and fix interval. More fixes were lost when vultures were perching compared to flying, in rugged versus flat topography. But long fix-intervals caused greater loss of fixes in dynamic (flying) versus static situations (perching). To conclude, we emphasize the importance of evaluating fix-loss bias in current tracking projects, and deploying GPS tags that allow remote duty cycle updates so that the most appropriate fix and data retrieval intervals can be selected., No

Global warming and direct anthropogenic impacts, such as water extraction, are largely affecting water budgets in Mediterranean wetlands, thereby increasing wetland salinities and isolation, and decreasing water depths and hydroperiods (duration of the inundation period). These wetland features are key elements structuring waterbird communities. However, the ultimate and net consequences of these dynamic conditions on waterbird assemblages are largely unknown. We combined a regular sampling on waterbird presence through the 2008 annual cycle with in-situ data on these relevant environmental predictors of waterbird distribution to model habitat selection for 69 individual species in a typical Mediterranean wetland network in south-western Spain. Species association with environmental features were subsequently used to predict changes in habitat suitability for each species under three climate change scenarios (encompassing changes in environment that ranged from 10% to 50% change as predicted by climatic models). Waterbirds distributed themselves unevenly throughout environmental gradients and water salinity was the most important gradient structuring the distribution of the community. Environmental suitability for the guilds of diving birds and vegetation gleaners will be reduced according to future climate scenarios, while most small wading birds will benefit from changing conditions. Resident species and those that breed in this wetland network will be also more impacted than those using this area for wintering or stopover. We provide here a tool that can be used in a horizon-scanning framework to identify emerging issues on waterbird conservation and to anticipate suitable management actions, Peer reviewed