The number of migrating raptors counted at established watch-sites is used to study raptor migration ecology and to determine the conservation status of migratory populations of raptors. Among the behavioural and ecological studies, counts have been used to determine daily and seasonal timing of migration (phenology), species diversity, influence of weather conditions, relative use of flight patterns (e.g., soaring versus flapping flight) and to study flocking behaviour, interspecific interactions, roosting behaviour.
Raptors are secretive, low-density birds, whose populations can be logistically difficult and financially prohibitive to monitor. A particularly cost-effective method for population monitoring of these birds, is to sample regional, and even continental populations, at traditional migratory bottlenecks and concentration points. Long-term migration watchsite database has been used to track changes in raptor populations and migration behaviour, also in relation to climate change. One of the first conservation application of long-term database was an analysis of the annual ratios of juvenile and adult Bald Eagles (Haliaeetus leucocephalus) seen at Hawk Mountain (U.S.) before and after the widespread use of DDT in mid-20th Century North America. The same database, which now extends into the 21st Century, was also used to track the eventual recovery of Bald Eagle populations following bans on DDT in Canada and the United States in the early 1970s.
In Europe, there are different projects and ornithological stations conducting long-term monitoring of migrating raptors; among those: Falsterbo (Sweden), Strait of Gibraltar (Spain), Lindus (France), Batumi (Georgia).