Often, if the primary prey species is migratory, then the peregrine will be, too. The migratory instinct also is related to latitude, so that the instinct increases from north to south, and from west to east. Migration occurs in late September and early October, with many birds migrating from the tundra areas of Canada as far south as Costa Rica and Central America. Most hunting is done in the early day or in late afternoon, with juveniles tending to forage earlier in the day than the adults. Even though females tend to take larger prey than do males, males and females frequently hunt cooperatively.
Man poses the greatest threat through shooting and the taking of eggs by oologists.
These relatively harmless parasites are often deterred by dust and water bathing. The greatest health threat is DDE, the breakdown product of DDT, a chlorinated hydrocarbon used world-wide as a pesticide in the 1950s and 1960s. A ban on DDT was not instigated by the Environmental Protection Agency until 1972, and many other countries soon did the same. DDT is still used in many countries where the peregrine winters, and so continues to be a threat. Most peregrine populations are censused by a simple count method.