The death, resignation, bankruptcy or expulsion of a sitting Councillor can cause a by-election to occur.
A notorious example occurred in August 1961 when a vacancy triggered the second by-election in under a year which had a turnout of only 3.65% of voters, prompting Mayor Dove-Myer Robinson to label the light turnout "...absolutely disgraceful.
[2] Two future Mayors of Auckland (John Allum and Dove-Myer Robinson) entered the council via by-elections in 1920 and 1952 respectively.
Between 1986 and 2010 municipal elections in Auckland were held via a Wards system of local electoral districts.
[3] The following is a list of by-elections held to fill vacancies on the Auckland City Council: Key