Migration of the Common Redstart (<em>Phoenicurus phoenicurus)</em>:a Eurasian songbird wintering in highly seasonal conditions in the West African Sahel

Some species of long-distance migrant birds are thought to follow spatiotemporal patterns of high food availability during the non-breeding season, a strategy termed "itinerancy," instead of being sedentary in one specific site. We tracked the migration of a small Eurasian songbird, the Common Redstart (Phoenicurus phoenicurus), using archival light-level geolocators. The birds showed a distinct counterclockwise loop migration from northern Europe. Fall migration passed west of the Mediterranean Sea and along the northwest African coast before the birds made an abrupt change of direction at the southern edge of the Sahara toward the winter area farther inland in the West African Sahel. Spring migration was more direct: north to the Iberian Peninsula and back to northern Europe. The birds spent more time in only one winter site than they do during the breeding season in northern Europe, and they generally showed no signs of itinerancy-except for one bird that probably avoided an exceptional drought. Their arrival on the winter grounds was well timed with peak vegetation greenness, assumed to reflect food availability, but vegetation greenness declined rapidly during their stay, and resource availability was relatively low throughout most of the non-breeding season. Despite the highly seasonal conditions in the wintering area, itinerancy is apparently not an optimal strategy for the Common Redstart, possibly because of timing constraints. Alternatively, food availability may not be closely linked to vegetation greenness

Prey diversity is affected by climate and differs between age classes in the Red-backed Shrike (Lanius collurio)

When breeding, food availability is essential for optimal reproductive output and is po-tentially one of the main factors limiting breeding success, especially in single brooded long-distance migratory birds. In this study, we examined the diet (as a measure of prey availability) of two Red-backed Shrike (Lanius collurio) populations in Denmark, based on more than 11,000 prey items covering seven years. We found a negative correlation be-tween prey diversity and temperature, indicating that Red-backed Shrikes feed on pre-ferred prey items in warmer summers (low diversity) while forced to feed on a larger vari-ety of species in colder summers. Adults had a more diverse diet and generally fed on smaller prey items than did young birds. Thus, age-and environment-related differences must be taken into account when describing the diet of the Red-backed Shrike. Direct nest observations produced different results for diet composition than did nest and pellet samples, underlining the importance of using different methods in diet assessments. De-tailed knowledge on limiting factors on the breeding grounds, such as food availability, is crucial for mitigating population declines of vulnerable species, such as the Red-backed Shrike

Autumn migration and wintering site of a wood warbler Phylloscopus sibilatrix breeding in Denmark identified using geolocation

Abstract Background Basic knowledge of detailed spatiotemporal migration patterns is lacking for most migratory bird species. Using the smallest available geolocator, we aim to map autumn migration and wintering areas of north European wood warblers Phylloscopus sibilatrix and compare the spatiotemporal pattern with recoveries of individuals ringed across Europe. Results A tracked wood warbler migrated south-south-east to sub-Saharan Africa in Sudan and then west-south-west to winter in Côte d’Ivoire. The timing and route fits well within the distribution of ring recoveries although the westward movement after the Sahara crossing is not revealed by the ring recoveries, but only few recoveries south of Sahara exist. Conclusions The surprising westward movement south of the Sahara supplements the overall pattern revealed by ring recoveries and aids our understanding of the connectivity and site dependence in this generally declining species

Informing a hydrological model of the Ogooué with multi-mission remote sensing data

Remote sensing provides a unique opportunity to inform and constrain a hydrological model and to increase its value as a decision-support tool. In this study, we applied a multi-mission approach to force, calibrate and validate a hydrological model of the ungauged Ogooué river basin in Africa with publicly available and free remote sensing observations. We used a rainfall–runoff model based on the Budyko framework coupled with a Muskingum routing approach. We parametrized the model using the Shuttle Radar Topography Mission digital elevation model (SRTM DEM) and forced it using precipitation from two satellite-based rainfall estimates, FEWS-RFE (Famine Early Warning System rainfall estimate) and the Tropical Rainfall Measuring Mission (TRMM) 3B42 v.7, and temperature from ECMWF ERA-Interim. We combined three different datasets to calibrate the model using an aggregated objective function with contributions from (1) historical in situ discharge observations from the period 1953–1984 at six locations in the basin, (2) radar altimetry measurements of river stages by Envisat and Jason-2 at 12 locations in the basin and (3) GRACE (Gravity Recovery and Climate Experiment) total water storage change (TWSC). Additionally, we extracted CryoSat-2 observations throughout the basin using a Sentinel-1 SAR (synthetic aperture radar) imagery water mask and used the observations for validation of the model. The use of new satellite missions, including Sentinel-1 and CryoSat-2, increased the spatial characterization of river stage. Throughout the basin, we achieved good agreement between observed and simulated discharge and the river stage, with an RMSD between simulated and observed water amplitudes at virtual stations of 0.74 m for the TRMM-forced model and 0.87 m for the FEWS-RFE-forced model. The hydrological model also captures overall total water storage change patterns, although the amplitude of storage change is generally underestimated. By combining hydrological modeling with multi-mission remote sensing from 10 different satellite missions, we obtain new information on an otherwise unstudied basin. The proposed model is the best current baseline characterization of hydrological conditions in the Ogooué in light of the available observations