PMC

Hunting movements of Eleonora's falcons. (a) Direction of movements out of Alegranza (hunting incursions) and respective kernel density estimate (represented by the density line; 97% to an eastern direction). (b) Maximum distance reached in hunting incursions in relation to the wind direction (from where it was blowing). Different letters above boxplots indicate a statistically significant difference between wind regimes, and numbers inside boxes and/or above the median segments indicate the sample size (number of hunting incursions for each wind direction). The line within boxes indicates the median, the edges of the boxes the first (Q1) and third (Q3) quartiles, and the whiskers extend 1.5 times the interquartile range.

Wind regime and Eleonora's falcons’ hunting movements. (a) Average wind direction (arrows) and speed (m s⁻¹; represented by arrow length and colour) on days on which seeds were recovered from migratory bird prey and on each day prior, when migratory birds were also potentially migrating. The wind rose (at the bottom right) represents the circular histogram of wind direction (the direction from which it blows) and the speed corresponding to a geographical band ranging from the southern Iberian Peninsula to Alegranza (data locations indicated by asterisks; wind data were obtained from the National Centers for Environmental Prediction, NOAA). The black rectangle delimits the geographical area shown in panel (b), which includes Alegranza. TN, Tenerife; GC, Gran Canaria; FV, Fuerteventura; LZ, Lanzarote. (b) Eleonora's falcons’ hunting movements (lines) during the same periods as in panel (a). Data from each individual are shown in a different colour. Alegranza is represented as a grey polygon, and the dashed lines cross its centroid and delimit its four main geographical quadrants (NE, SE, SW and NW). (c) Photograph of an Eleonora's falcon holding its bird prey in the study area (photo: J. Palmero). (d) Photograph of a typical larder where hunted migratory birds are stored.