California saw the highest number of approved mergers at eight, and Illinois came in second with six consolidations. During the first quarter of the year, the Golden State posted only one merger while Illinois saw five consolidations, according to the NCUA.

While each merger happens for a different reason, most occur to provide expanded opportunities for products and services for members of the merged credit unions, which helps to strengthen the credit union presence in the community, Rick Stanton, the California and Nevada Credit Union Leagues' vice president of media relations and data analysis, noted.

"Mergers also provide economies of scale that lead to more efficiencies and savings," he said. "Increased expense related to the ever-expanding burden of regulation compliance is of growing concern to all credit unions. Other one-off situations also present an opportunity for a credit union to evaluate their future path including a changing relationship with a primary SEG or the retirement of the CEO."

New York, Pennsylvania and Texas each had four approved credit union mergers by the end of the second quarter, and Michigan, Massachusetts, Louisiana and Minnesota each posted three mergers, according to the NCUA's Insurance Reports of Activity for April, May and June.

The NCUA reports for the second quarter also listed seven credit unions with more than $100 million in assets that received approval to consolidate with their larger counterparts.

During the first quarter, there were only two credit unions with more than $100 million in assets that received approval to merge, for a total of nine credit unions in the first half of the year.

At the end of the first half of 2014, the NCUA approved six credit unions with more than $100 million in assets to consolidate.

However, the NCUA cautions against defining the size of credit unions merging as a trend given the small numbers.

"The overwhelming majority of merging credit unions have assets below $50 million," John Fairbanks, public affairs specialist for the NCUA, said. "Our staff does not believe there is a material trend at this moment of substantially larger credit unions merging into other credit unions. One could reasonably note the larger consolidations are more likely due to strategic reasons, as opposed to the more pronounced safety and soundness issues that existed during the 2008-2009 era."

The NCUA, however, also follows the actual merger completions more closely than the approved mergers because some consolidations never occur.

At the end of this year's second quarter, there were 33 completed mergers, Fairbanks said. That tally was far below the 63 completed mergers at the end of 2015′s first quarter.

The NCUA determines completed mergers when credit unions, which had their consolidations approved earlier, do not file a 5300 Call Report at the end of a quarter.

During the second quarter, the largest merged credit union was the $505 million Premier Members Federal Credit Union in Boulder, Colo., into the $328 million Boulder Valley Credit Union. That merger was completed on May 1, and Boulder Valley Credit Union now manages more than $846 million in assets and serves nearly 65,000 members.

The second largest merged credit union of the second quarter was the $342 million Visterra Credit Union in Moreno Valley, Calif., which officially merged Aug. 3 with the $799 million Altura Credit Union in Riverside, Calif., creating the 37th billion dollar cooperative in the Golden State.

California also saw the third largest merged credit union, which was the $306 million Pacific Oaks Federal Credit Union in Camarillo, Calif., into the $1.7 billion Premier America Credit Union in Chatsworth, Calif. That consolidation was finalized on Aug. 1.

In Minnesota, the $190 million Lake State Credit Union in Moose Lake received NCUA approval to merge into the $419 million Members Cooperative Credit Union in Cloquet. That consolidation was completed on July 1.

In Massachusetts, the $171 million Industrial Credit Union in Boston merged with Webster First Federal Credit Union in Worcester on May 31, which now manages $831 million in assets and serves more than 67,000 members.

In addition, the $200 million Educational Credit Union in Topeka, Kan., secured NCUA approval to merge with the $265 million Quest Credit Union also based in Topeka. The merger is expected to be finalized in April 2016, according to Educational Credit Union's website.

And the $170 million Air Line Pilots Association Federal Credit Union in Burr Ridge, Ill. received approval from the NCUA to consolidate with the $1 billion Connexus Credit Union in Wausau, Wis. That consolidation was approved by members of Air Line Pilots Association Credit Union on July 8.

Though it's unknown whether the number of consolidations of credit unions with more than $100 million in assets will continue to increase during the second half of the year, a consultant noted in a June CU Times story that he expects to see more large cooperatives merging that are based in metropolitan areas.

Glenn Christensen, president/CEO of the CEO Advisory Group, a M&A consultancy in Kent, Wash., said he expects more consolidations among credit unions in the $500 million to $1 billion asset range to achieve the scale needed to compete in large metropolitan regions.

Nevertheless, among the 71 credit union mergers approved by the NCUA during the second quarter, about 95% were under $50 million in assets.

The federal agency green-lighted 53 mergers for expanded services, seven for poor financial condition, four for lack of sponsor, two for poor management, two for lack of growth and three for the inability to find a new CEO.