The breeding status of the Merlin Falco columbarius in Britain in 1993–94

Abstract

Earlier this century there were widespread reports, but little detail, of declining Merlin populations in Britain. A partial survey in 1983–84 resulted in an estimate of 550–650 breeding pairs. Local studies have since reported increases, decreases and stability in Merlin populations. Against this background the RSPB organized the second breeding survey of Merlins in Britain during 1993 and 1994, to estimate the population and assess regional trends. This survey located 796 breeding pairs of Merlins and estimated a further minimum of 24 pairs from areas previously well surveyed, 53% of the known breeding range. For the remainder of the range an extrapolated estimate of 471 pairs with 95% confidence limits of 288–680 pairs was calculated following survey of 36 10-km National Grid squares. A number of checks were made on survey efficiency and accuracy. It is recommended that a rounded figure of 1300 ± 200 pairs of breeding Merlins be used as the revised population estimate for Britain. In all areas where comparisons were made between surveys, Merlins have increased or remained stable. Reasons for this are discussed, as is the logic behind the species being retained in the revised UK Red Data Bird list. © 1998 British Trust for Ornithology.