Marsh harrier (Circus pygargus) is somewhat smaller than the very common hen harrier and the smallest of the harriers that appear more or less regularly in our country. With its wings outstretched, it measures between 39 and 50 cm, and the wingspan is from 96 to 116 cm. This is a slender raptor with very long and narrow wings and a distinctly long tail.
The male's back, head, neck, and chest are ash gray. The ash-gray is also the upper side of his wings and the middle of the upper side of the tail, which has broad brown-gray stripes on the sides; the tail is white. The gray of the wings is interrupted by a narrow, but pronounced black line in the middle of the wing, and the tips of his wings are entirely black. For the male marsh harrier, the brown-striped underside of the wing and the dark brown lines on the belly are also characteristic, which are noticeable only up close. Very old males may completely lose this striped pattern, and the gray parts of their bodies may take on a bluish tint.
The female has protective coloration, light and dark brown striped; only her tail is white. In color and pattern she is extremely similar to the female of the Pallid Harrier (Circus cyaneus). What distinguishes her from that one is only the darker stripe in the middle of the upper side of the wing (similar to the male) and especially the body shape. The female marsh harrier is somewhat more slender and has distinctly narrower wings.
For young individuals the reddish-brown underside of the body is not striped. The dorsal side of juvenile individuals is similar to that of the females.
The male and female marsh harrier often pair for life. They nest in May and June. The nest, made of grasses and twigs, is placed on the ground, preferably in the center of a large reed bed or marsh, but also in a meadow or shrubland. As reed beds shrink, the ideal nesting site for the marsh harrier disappears, but this species has managed to adapt, and many pairs today nest, for example on cropland fields, where they face a new threat – the excessive use of pesticides.
In our country it is regarded as a rarely observed species, which can be observed especially during migration, in spring and autumn. In winter we will wait in vain, as it waits for more favorable conditions at its wintering grounds in Africa.
Marsh harrier is active during the day, when we will most often observe it while foraging for food. Then it usually soars low over the ground, and when it spots prey it immediately turns and, with outstretched legs, dives onto it. It feeds mainly on small mammals and smaller birds, reptiles and large insects.
