Montagu's Harrier Circus pygargus
The first documented record of Montagu's Harrier in the county was of one shot at North Cotes, October 9th, 1935 (Lorand and Atkin (1989), and later it was reported that since 1949 the species had been seen almost annually, especially on The Wash. A pair attempted to breed at Saltfleetby in 1951, and another pair nested successfully at the Nene Mouth in 1956; no young fledged from either attempt. Two pairs bred in 1965 fledging two young after which single pairs bred in 1969 and 1980 before more regular breeding began from 1987 but even then nesting attempts were irregular until a small colony became established around The Wash from 2000 to 2011. After a spate of good years in 2000-2005 when an average of five pairs per year bred, RBBP records show an average of 0.4 pairs per year bred during the period 2013-2017; the most young reared in a season was only seven. Away from The Wash breeding pairs have appeared at inland sites with birds sometimes returning in the following one or two years but losses on migration mean that single pairs seldom survive at a locality for many years without replacement. The last successful nest in the county was in 2012 when an inland pair fledged four young and the last nesting pair was recorded in 2014 but the nest was predated soon after the chicks hatched. The first migrants appear in mid- to late April and most of the annual records refer to passage migrants many of which are 2CY or 3CY birds. The last records of the year are typically in September or early October, latest October 11th. The number of birds occurring has declined in line with the British population which peaked in 2007. No birds bred in Britain in 2020 for the first time in 40 years.
(Account as per new Birds of Lincolnshire (2021), included September 2022)