Magpies coexist peacefully with Canberrans for about two-thirds of the year, crammed together in the city by its tree-lined streets and leafy parks.

Starting last month, the relationship grows more strained as the birds begin to swoop their neighbours and drive them out of their territory.

Cyclists have started taking precautions with cable ties protruding from their helmets, as nesting season turns urban-dwelling magpies into aggressive protectors of their fledglings as early as July and until as late as November each year.

ACT government senior ranger Nadia Rhodes has been in town for 13 swooping seasons, and, like many, has memories of being swooped walking to school. She's starting to receive phone calls from people wanting advice.