Post-fledging dependence period, dispersal movements, temporary settlement areas, and causes of mortality in saker falcons from Central Europe

We are currently aware of home-range sizes and mortality rates during the post-fledging dependency period (PFDP), as well as the migration routes and wintering sites of many raptors. In comparison, the period of natal dispersal is significantly understudied, including survival rates and information on the temporary settlement areas (TSA). Despite their importance, these data are unavailable for most raptor species, though they are crucial for more effective species protection and more efficient financing of nature conservation. Using satellite telemetry, we monitored twelve young saker falcons (Falco cherrug) from fledging through the start of dispersal, and continued monitoring until their deaths. None of them died during the PFDP, but only one survived the natal dispersal period, reached adulthood and joined the breeding population. Their PFDP lasted 47 days (median, hereinafter), and they occupied home ranges of 81 and 23 km², calculated using the 100% and 80% minimum convex polygon (MCP) methods, respectively. Monitored individuals exhibited two distinct dispersal movement/behaviour patterns: seven individuals dispersed over long (>500 km) distances, and five others over short (<100 km) distances from their natal areas. During these movements, ten individuals established 21 TSAs. These were occupied for 28 days and covered 981 and 278 km², according to the 100% and 80% MCP, respectively. The finding that only one individual survived to adulthood contrasts with the increasing population trend in Slovakia and may be a consequence of the survival impacts of tagging. However, at least half of all documented mortality was attributable to human-induced causes, including at least one-third of deaths being caused by overhead power lines. This highlights the need to eliminate or at least try to reduce all types of anthropogenic mortality, such as electrocution, hunting, and/or poisoning, as much as possible immediately, if we want to reverse negative population trends in many birds of prey and to preserve them in the long term.