At least three smaller credit unions are in the course of merging.Many more mergers must be talked over as the mutual banking sector quickens an already speedy consolidation of "rats and mice" ADIs. APRA put the number of ADIs at 75 this week, and plenty remember the days when it was more than 700, only 30 years ago.Manly Warringah Credit Union will fold into Community First, the largest in Sydney but one of the less active on the merger front.Trading now as Northern Beaches, Manly Warringah has flopped around as a merger candidate for years.The CEO, David Thomas, wrote in the annual report "the difficult decision to merge whilst our relative position in the industry was strong was made in July."The net profit for Northern Beaches Credit Union was A$350,000. It made next to no profit in 2012, a loss in 2013 on the scale of the 2015 profit and only a small return in 2014. It has only around $100 million in loans.Talks with Police Credit Union fell through a few years ago, then members spurned a proposal from Sutherland Credit Union in 2013.Fire Brigades Employees Credit Union is the next in Sydney in talks for a hook up.A letter from chair Andrew McCready explained that the board was seeking a merger "with an organisation large enough to meet all those challenges, but small enough to maintain a focus on our members as people, most likely with another customer owned financial institution.""We strongly believe this merger will bring the economies of scale and the ability to offer," McCready said.The second party in this marriage is yet to be clear.It may have an energised, trade union-aligned workforce willing to some degree to double up with a credit union stake, but FBECU is no prize catch. Its yield, or profit, is not much more than three per cent, which is not much more than it pays out on term deposits.The firies' ADI had $4615 million in net assets at 2015.Meanwhile Country First credit union from Griffith, NSW will soon fold into Adelaide's Beyond Bank. Country First has around 3000 members and assets of $29 million.Were $200 million the threshold to jettison a mutual ADI into history another 40 would be set to fall.