In some of the burglaries, the firearms were targeted and in other burglaries they were taken among other items.
In the most recent firearms burglary, thieves smashed their way into a locked gun cabinet in a house at Kauri and stole a .22 rifle and a .45 lever action gun, and some boxes of .45, .22 and 9mm ammunition.
In June, a 12 gauge shotgun with 30 inch blue barrel and a camouflage semi-automatic 12 gauge shotgun were taken from a Dargaville property.
The two guns had not been locked away.
During the annual cannabis blitz Operation Lucy, 40 of the 112 firearms seized nationally were discovered in Northland.
Northland police operations manager Inspector Marty Ruth said police were concerned at the number of firearms falling into the hands of criminals and urged people to report those who held weapons without a licence.
"We are concerned by the number of firearms we find when executing search warrants and we need to get illicit firearms out of the hands of criminals for the safety of everyone."
He said 40 guns reported stolen in a year was not excessively high.
Firearms owners must lock their guns away as required by law, Mr Ruth said.
If a licence holder was a firearms collector or had a military style semi-automatic weapon or pistol, then recovered firearms could be traced back to the owner, as the firearms were specifically registered to the owner. However, the bulk of firearms such as .22 rifles and shotguns were not registered.
The number of weapons offences in Northland has fluctuated over the past three years, with 327 offences in 2011 rising to 369 the following year, and dipping to 333 in 2013.
