Field moon

A medium-sized and light-weighted bird of prey is 46–47 cm long, wingspan 97–118 cm. ^[4] Like other members of the genus , it is distinguished by long wings and a tail, due to which it slowly and silently moves low above the ground. Females look noticeably larger than males — their weight is 390–600 g, while males weigh 290–390 g. ^[5] The color also has pronounced sexual dimorphism . In an adult male, the upper body, throat, goiter and “cap” on the head are ash gray; the belly, facial disc, and nails are white. A clearly visible white lumbar spot. There is a clear border between the dark top and the light bottom, which distinguishes the male of this bird from the steppe moon close to it. The wings are long and relatively narrow, with black endings of the primary wing and a dark stripe along the rear edge. The female field moon above is dark brown with ocher-reddish spots on the coverts, below is light ocher with dark streaks (teardrop-shaped on the chest and longitudinal on the belly). Three longitudinal dark stripes are clearly visible on the underside of the wing of the females, and three transverse stripes on the undertail. In the first year of life, young birds look like mature females, differing from them in a redder shade of the lower part and fewer speckles, especially on the belly, as well as wide red borders of the feathers of the back. The iris in yellow birds is yellow, in young grayish-brown. The legs are long, yellow ^{[6] [7] [8]} .

Vocalization is a rattling two-syllable screech and a high jerky scream ^{[6] [9]} . The female, when feeding the male, emits a ringing whistling squeak “pi”, and in case of anxiety, a sharp rattling scream “Ki-ki-ki ... ki-ki-ki ...”, which at the end becomes more and more loud. The male’s voice is more demonstrative, melodic - high jerky “check-ek-ek-ek ...”. In the mating season, the male can make quick “laughing” sounds “chuk-uk-uk-uk”, reminiscent of the cry of a small gull ^[4] .

Allocate 2 subspecies of the field moon. Nominal subspecies C. c. cyaneus (Linnaeus, 1766) lives in Europe and Asia . Subspecies C. c. hudsonius (Linnaeus, 1766), characterized by a darker plumage, nests in North America .

Range

Field harrier nests in the northern hemisphere from forest tundra in the north to the steppe zone in the south. In Eurasia, distributed throughout from west to east. In Scandinavia and on the Kola Peninsula, found south of 70 ° C. w. in Norway , 68 ° C. w. in Sweden , 62 ° C. w. in Finland and the Murmansk region . In the interval between the White Sea and the Yenisei basin in Western Siberia, it occurs south of 67 ° C. sh., in Eastern Siberia approximately south of 67 ° N. w. The southern border of nesting runs through the north of the Iberian Peninsula , the southern border of the Alps , the Carpathians , the northern coast of the Black Sea , Crimea , Transcaucasia , the Volga Region and the Urals in the region of 52 ° C. sh., Northern Kazakhstan up to the 52nd parallel, Altai , Northern Mongolia , Northeast China and northern Primorye . Outside the mainland, there are British , Orkney , Hebrides , Shantarsky and possibly on Sakhalin ^[8] . In North America, nests in the north to northern Alaska , northern Saskatchewan , southern Quebec , Newfoundland and Labrador ; in the south to Baja California , southern Texas , southern Missouri , West Virginia , southeast Virginia, and North Carolina ^{[10] [11]} .

The populations of Northern and Eastern Europe , Asia, and northern North America are completely migratory, the rest are partially migratory or dispersing. In the case of migration, they winter in Western Europe south of Scotland and Southern Sweden (some individuals reach North Africa ), in Asia from Western Asia and the Middle East in the west to the Korean Peninsula , the Gulf of Japan and the islands of the East, and in America south of the Canadian provinces of British Columbia and New Brunswick to Panama , Colombia and Venezuela in South America . Sometimes found in the Greater Antilles ^[12] .

Habitats

It inhabits predominantly open landscapes. In the forest zone it is found at the edges, clearings, burns, moss swamps, along the outskirts of fields, in meadows of river valleys. In the nesting period, the most preference is given to small cuttings 3-5 years old, densely overgrown with nettles , fireweed and raspberry bushes ^[6] . Less commonly, it settles near shrubbery. In the north of the range it lives in the forest-tundra , in the south in the steppe or prairies . It is found in the mountains up to 3200 m above sea level ^{[13] [14]} .

Puberty in males and females occurs at the age of one year ^[15] . Most males are monogamous , although in some cases there are cases of polygyny - one male can serve up to five females per season. Females are monogamous ^[16] . In the case of migration, the field harrier arrives at nesting sites in March – May ^[12] , in central Russia in the first half of April, when the first large thaw areas appear ^[9] . Field moons often nest in loose colonies of 15–20 pairs ^[17] . With a high population density, the distance between neighboring nests varies between 0.5–2.0 km, in other territories 2–10 km ^[6] . During the breeding season, the moon carefully guards its territory, driving away other birds from the nest and attacking even humans ^[18] .

During courtship of the female, the male performs acrobatic studies in the air, flying high in the sky and spinning, falling down ^[18] . As a place for building a nest , a small glade is chosen, usually not far from the water and at a distance of 10-200 m (less often up to 600 m) from the vast open space - fields, meadows, swamps or river valleys ^[6] , where birds hunt feed. The nest is a relatively flat building with a shallow tray, woven from dry thin twigs and lined with grass stems ^[9] , which is located directly on the ground, in thickets of tall grass or on water - in the latter case willow bushes sticking out of the water, sedge hummocks or other bases of plant origin ^[15] . The diameter of the nest is usually 500-600 mm, height 250-300 mm, the diameter of the tray 150-200 mm ^[9] . The female is mainly engaged in construction, while the male is involved in the extraction of feed ^[17] . For perching, birds use small elevations - stumps, fence posts, etc. ^[13]

Eggs are laid once a year, in mid-May - early June ^[17] . The masonry consists of 3–7 (usually 3–5) eggs of white color with a bluish tint and sometimes with a rare brownish-ocher staining. The size of the eggs is (40–53) x (32–39) mm ^[6] . Almost all the time, one female incubates ^[8] . However, it may leave the nest on the male for several minutes ^[17] . The incubation period is approximately 31–32 days; hatched chicks are covered with white with a grayish-ocher hue down. The male, during the incubation period and the first time after the hatching of the chicks, is engaged in the extraction of feed, which is dumped from above into the nest, while the female is engaged in feeding the young. About two weeks after the birth of the offspring, the male leaves the nest, and in the future, the female is engaged in the upbringing of the chicks ^[16] . Around the age of 35 days, the chicks leave the nest, after which they disperse ^[8] . In Russia, flying chicks can be seen in mid-July ^[9] . Departure for winter apartments begins in August, although the bulk departs in September. During migration they fly on a wide front.

It feeds mainly on mouse-like rodents - voles , hamsters , mice ; in areas of plenty, they can make up to 95% of the total diet ^[19] . For example, in many parts of America, the main food is Pencilvian voles ( Microtus pennsylvanicus ) ^[15] . In addition, they hunt a variety of amphibians , reptiles and insects . Hares , shrews ( Sorex ), ground squirrels ( Spermophilus ) and some birds are caught. Occasionally it feeds on carrion ^[14] . During the hunt, they fly low and silently above the ground, looking for prey.

• Vertebrates of Russia: Field Lun
• Club of researchers of Russian feathered predators - Field lun (Circus cyaneus)
• Ecological Center Ecosystem - Field Harrier
• Animal Diversity Web - Circus cyaneus
• US Department of Agriculture, Forest Service - Circus cyaneus