Radars can be employed effectively in monitoring precipitation and tracking the migration of animals. In weather monitoring, radar systems are integral for detecting and analyzing rainfall patterns, providing real-time data on precipitation. Similarly, radars can be used in tracking animal migration by detecting their movements over landscapes. However, the identification of narcotics on passengers at airports or in aircraft typically relies on other methods, such as X-ray scanners or chemical detection technologies, rather than radar systems. Thus, the correct option is that radars can be utilized in only two out of the three mentioned activities.