Selection of nesting habitat by Montagu's Harriers Circus pygargus and Hen Harriers Circus cyaneus in managed heaths

Abstract

Capsule Montagu's Harriers avoided tree plantations and selected plots with dense heath of intermediate height, while sympatric Hen Harriers preferred afforested or taller plots of heath. Aims To investigate relationships between vegetation structure and nest selection by Montagu's and Hen Harriers. Methods We defined three vegetation strata: upper, intermediate and lower. Height and cover of plant species in each stratum were recorded in a 9-m2 area centred on nests or unused random points. Statistical analysis was performed to reveal predictors for classifying plots (i) with a Montagu's Harrier nest, (ii) with a Hen Harrier nest and (iii) without a nest. Results Montagu's Harriers selected places where tree cover was less than 25%, the maximum height of the upper stratum was 1.87 m, and the cover of the intermediate stratum was greater than 75%. Hen Harriers nested either in plots where the upper stratum was higher than 1.87 m, or where tree coverage was greater than 25%. Conclusions To encourage the breeding of Montagu's Harriers, the planting of pine should be avoided and the heath should be rejuvenated before it reaches 1.80 m in height. For Hen Harriers, certain plots of heath higher than 2 m should be kept. In agricultural landscapes, patches of managed shrubland or heathland could help conservation of both species.