Merlin population trends and threats
In the UK, widespread declines since the late 19th century are thought to be caused by human persecution, habitat loss and increased disturbance.
Changes in merlin populations
Little is known of the past population changes of this species across Europe. In common with most other raptors, it suffered from the effects of organochlorine pesticides in the 1950s and 1960s, but overall, any decreases and their causes are poorly understood.
From the 1950s, merlins were badly affected by organochlorine pesticides, resulting in an all-time population low by 1960 of about 550 pairs. It was only in the early 1980s that the population showed any signs of recovery.
Merlins are a Red status bird with a 94 per cent increase, but they are still at threat. This is the case even though the trends are on the up.
Despite a major reduction in the levels of pesticide contamination since the mid-1980s, the merlin is still the most heavily-contaminated species of raptor in the UK. The population recovery has been slow, and has been hampered by habitat loss, primarily due to afforestation and overgrazing.
Illegal killing and egg collecting
Pesticide contamination no longer causes concern, though the northern populations carry inexplicably heavy mercury loads.
Recreational disturbance pressure is a concern in some areas.
Site specific conservation measures for the merlin are relatively ineffective, because of its low population density. Instead, general land use policies for upland areas need to include a provision for the birds and ensure that key feeding and nesting requirements are not compromised.
Of particular importance are sympathetic management of heather moorlands and adjacent low intensity agricultural land, and sympathetic management of forests in areas where the birds nest in trees.
Vigilance against illegal killing and egg-collecting continues to be important in curbing this unnecessary source of mortality. Monitoring the presence of mercury and other environmental contaminants in the birds continues.