UK sovereign base areas (SBAs) in Cyprus have become illegal bird-trapping "hotspots", according to research.
The RSPB and BirdLife Cyprus have been monitoring songbird-trapping operations on the island since 2002.
BirdLife Cyprus told BBC News that, in that time, the scale of bird-trapping had increased by 54%.
Although it is widespread, the charity said that some of the largest trapping operations were on UK soil.
These take place on the two British SBAs in Cyprus, at Akrotiri and Dhekelia, sites covering about 100 sq miles that are British sovereign territory and within which the UK maintains a permanent military presence.
Martin Hellicar from BirdLife Cyprus explained that in Dhekelia - in the south-east of the island - organised criminal gangs created "labyrinths" of acacia trees, irrigating the plantations and cutting corridors through them in order to set up long mist nets.
These operations often also use loudspeakers with recordings of bird calls in order to lure migrating birds into the almost invisible nets.
The songbirds are killed and sold to restaurants for the illegal but widely available Cypriot delicacy ambelopoulia.
"A dozen birds can fetch up to 80 euros," a spokesperson from BirdLife Cyprus told BBC News.
Because Cyprus is a key stopover on the migration route of many birds, including blackcaps and warblers, the trapping mainly takes place during the autumn.
The researchers estimate that, during the 2013 trapping season, 1.5 million birds were killed across Cyprus.
This latest estimate will be published in early 2014, as part of a report on bird-trapping in the country. It is based on a decade of survey data, where researchers measured the scale of the trapping and estimated how many birds would be caught in those traps.
BirdLife Cyprus said it was calling on the Ministry of Defence (MOD) to do more to tackle illegal bird trapping on its land.
A spokesperson from the MoD said it already took the issue "extremely seriously". It added that the SBA police, administered by the MoD, were conducting a continuing operation to combat trappers.
"We have worked closely with BirdLife Cyprus and on numerous occasions have invited them to observe our efforts to tackle this abhorrent illegal activity," the MoD told BBC News.
"Unfortunately, as long as there is still demand for these dishes then the activity is likely to continue, [but] the SBA authorities will continue to do all they can to try and stop it."
Andreas Pitsillides, who is chief inspector of the SBA police in Dhekelia, told the BBC that when his team carried out raids on these operations, they would often find between five and 10 20m-long mist nets in one location.
"[The trappers] have become professionals," Mr Pitsillides told the BBC.
"They have spotters, so when they see our police cars, and even our unmarked cars, they contact each other with mobile phones and leave the area. So it's very difficult to arrest them."
The charity also hopes that its latest findings will persuade the Cypriot government to "take action against the restaurants that are selling this illegal dish".