Harrier (bird) in the context of "Birds of prey"

The white-tailed eagle (Haliaeetus albicilla), sometimes known as the "sea eagle", is a large bird of prey, widely distributed across temperate Eurasia. Like all eagles, it is a member of the family Accipitridae (or accipitrids) which also includes other diurnal raptors such as hawks, kites, and harriers. One of up to eleven members in the genus Haliaeetus, which are commonly called sea eagles, it is also referred to as the white-tailed sea-eagle. Sometimes, it is known as the ern or erne (depending on spelling by sources), gray sea eagle and Eurasian sea eagle.

While found across a wide range, today breeding from as far west as Greenland and Iceland across to as far east as Hokkaido, Japan, they are often scarce and spottily distributed as a nesting species, mainly due to human activities. These have included habitat alterations and destruction of wetlands, about a hundred years of systematic persecution by humans (from the early 1800s to around World War II) followed by inadvertent poisonings and epidemics of nesting failures due to various manmade chemical pesticides and organic compounds, which have threatened eagles since roughly the 1950s and continue to be a potential concern. Due to this, the white-tailed eagle was considered endangered or extinct in several countries. Some populations have since recovered well, due to governmental protections, dedicated conservationists and naturalists protecting habitats and nesting sites, partially regulating poaching and pesticide usage, as well as careful reintroductions into parts of their former range.

The Accipitridae (/ˌæksɪˈpɪtrɪdiː, -deɪ/) is one of the four families within the order Accipitriformes, and is a family of small to large birds of prey with strongly hooked bills and variable morphology based on diet. They feed on a range of prey items from insects to medium-sized mammals, with a number feeding on carrion and a few feeding on fruit. The Accipitridae have a cosmopolitan distribution, being found on all the world's continents (except Antarctica) and a number of oceanic island groups. Some species are migratory. The family contains 256 species which are divided into 12 subfamilies and 75 genera.

Many well-known birds such as hawks, eagles, kites, harriers and Old World vultures are included in this group. The osprey is usually placed in a separate family (Pandionidae), as is the secretary bird (Sagittariidae), and the New World vultures are also usually now regarded as a separate family or order. Karyotype data indicate the accipitrids analysed are indeed a distinct monophyletic group.

The red kite (Milvus milvus) is a bird of prey in the family Accipitridae, which also includes many other diurnal raptors such as eagles, buzzards, and harriers. The species currently breeds only in Europe, though it formerly also bred in west Asia and northwest Africa. Historically, it was only resident in the milder parts of its range in western Europe and northwestern Africa, whereas all or most red kites in northern mainland Europe wintered to the south and west, some also reaching western Asia, but an increasing number of northern birds now remain in that region year-round. Vagrants have reached north to Finland and south to Israel, Libya and the Gambia.

In ornithology, the facial disc is the concave collection of feathers on the face of some birds—most notably owls—surrounding the eyes. The concavity of the facial disc forms a circular paraboloid that collects sound waves and directs those waves towards the bird's ears. The feathers making up this disc can be adjusted by the bird to alter the focal length of this sound collector, enabling the bird to focus at different distances and allowing it to locate prey by sound alone under snow, grass, and plant cover.

Other bird species, such as harriers, have less prominent facial discs. In harriers, the related term facial ruff refers to feathers around the neck that are raised in response to noise, essentially enlarging the facial disc and improving hearing.