The merlin (Falco columbarius) is Britain's smallest falcon, a compact and swift predator of upland moorlands and coastal areas. Despite a relatively stable UK population, it faces ongoing pressures that make welfare and conservation monitoring important.
Merlins are specialist hunters of small birds, pursuing prey in fast, low-level chases across open ground. Meadow pipits form the primary prey on UK breeding grounds; skylarks, wheatears, and other small passerines also feature. Females (up to 230g) are notably larger than males (about 165g), typical of raptors where females must defend territories and defend nest sites. Merlins do not build nests — they use abandoned crow nests in heather, rock ledges, or cliff faces.
The UK breeding population is estimated at around 1,300 pairs, primarily in upland Britain including the Pennines, Wales, Scotland, and Northern Ireland. The species is amber-listed on the UK conservation list. Wintering birds from Iceland and Scandinavia augment the UK population in coastal habitats from October to March. Winter habitat includes coastal marshes, estuaries, and lowland agricultural areas where small bird flocks concentrate.
Illegal persecution: Merlins are Schedule 1 protected species and any intentional killing, injury, or disturbance at the nest is a criminal offence. Persecution on grouse moors — where merlins are sometimes seen as competitors — still occurs. Poisoning (particularly from carbofuran), shooting, and nest destruction are documented. The RSPB Investigations team and Police Wildlife Crime Officers investigate incidents.
Wind energy development: Merlins hunt in characteristic low-level flight patterns that increase collision risk with wind turbines. Impact assessments for upland wind farm proposals should include merlin surveys and apply appropriate avoidance mitigation.
Breeding disturbance: Merlins are sensitive to disturbance at nest sites. Schedule 1 protection means that deliberately approaching within disturbance distance of an occupied nest without a licence is an offence. BTO ringers and photographers must hold appropriate licences for proximity to nesting birds.
Merlin breeding success is linked to the availability of suitable nesting habitat (deep heather for ground-nesting) and prey abundance (dependent on unimproved upland habitats supporting pipit and lark populations). Heather management through controlled burning or cutting at appropriate scales benefits merlin habitat. Reversion of degraded moorland to heather dominance through reducing grazing pressure increases breeding territory availability.
Wintering merlins in coastal and lowland habitats face different challenges. Harsh weather periods reduce prey availability and hunting efficiency. Rodenticide contamination in prey species has been detected in raptors including merlins. Habitat availability in key wintering areas is affected by agricultural change. Protecting coastal and lowland habitats that support winter prey concentrations is important for merlin population support through the year.
← Back to Animal Welfare Hub