ヨーロッパヤマウズラ 対 ベニハシガラス

The most reliable field mark to separate Grey Partridge from Red-billed Chough is overall coloration and bill/leg color: Grey Partridge is a rotund, earth-toned gamebird with a small, pale bill and legs, while Red-billed Chough is a sleek, crow-like bird with glossy black plumage, a long, curved red bill, and red legs. Juvenile Grey Partridges are yellow-brown and lack the adult's face and belly markings, but never show the black gloss or red bare parts of the chough. In flight, Grey Partridge shows short, rounded wings and a whirring, low flight, while choughs have long, broad wings and a buoyant, acrobatic flight style. Even at a distance, the chough's black plumage and distinctive bill shape are unique among European birds.

1. Bill color and shape: Red-billed Chough has a long, slender, downcurved red bill (orange in juveniles), while Grey Partridge has a short, stout, pale bill. This is diagnostic at all ages.
2. Leg color: Chough legs are bright red (pink in juveniles), never seen in partridge, which has dull, pale legs.
3. Plumage color: Chough is entirely glossy black with a greenish sheen; Grey Partridge is never black, instead showing grey, brown, and rufous tones with a rusty face and chestnut flanks.
4. Juvenile confusion: Young partridges are yellow-brown and lack strong facial or belly markings; juvenile choughs are black with less gloss, orange bill, and pink legs. No brown or earth tones in chough at any age.
5. Flight style: Partridge flies low and fast with short, rounded wings, usually only briefly when flushed. Choughs have long, broad wings, soar and glide, and perform aerial acrobatics.
6. Tail shape: Chough has a wedge-shaped, longer tail; partridge has a short, squared tail.
7. Size and jizz: Chough is longer, more slender, and upright; partridge is compact, squat, and ground-hugging.
8. Habitat: Partridge in lowland fields, meadows, and farmland; chough on cliffs, uplands, and sometimes old buildings in open country.
9. Group behavior: Choughs are often in noisy, active flocks; partridges in small, quiet coveys.
10. Vocalizations: Chough's "chee-ow" is loud and ringing; partridge's "kieerr-ik" and "rick rick rick" are harsher and less musical.
11. Face pattern: Partridge adults have a rusty face and dark belly patch (smaller in females); chough has a plain black face with a red bill.
12. Sex differences: Both species show little sexual dimorphism in the field, but female partridges have a smaller belly patch and duller plumage.
13. In-hand marks: Partridge females have two transverse bars on the tertiary coverts ("cross of Lorraine"), males only one; not visible in the field.
14. Seasonal changes: Choughs retain black plumage year-round; partridges only show yellow-brown tones as juveniles, quickly gaining adult pattern.
15. Common pitfalls: At a distance, a chough's black shape and flight may be mistaken for a crow, but never for a partridge. Partridges are never seen soaring or on cliffs, and never appear black or have red bare parts.

Grey Partridge is a compact, chunky bird, typically 29–31 cm in length with a wingspan of 45–48 cm. Red-billed Chough is noticeably larger and more elongated, at 39–40 cm long with a wingspan of 73–90 cm. Despite the chough's larger size, their average mass is similar (partridge up to 455 g, chough around 287.5–310 g), but the chough appears lighter and more agile due to its proportions and flight style. Partridges are ground-dwelling and appear squat, while choughs are more upright and crow-like.

• Juvenile/immature birds: Young Grey Partridges are yellow-brown overall, lacking the adult's rusty face and dark belly patch. Juvenile Red-billed Choughs are glossy black but with less sheen than adults, and have an orange bill and pink legs (not red). No age of chough is brown or earth-toned like a partridge.
• Adults: Grey Partridge adults are greyish with a rufous face, chestnut flanks, and a dark belly patch (smaller or duller in females). Their wings are brown with no gloss. Red-billed Chough adults are entirely velvet-black with a greenish gloss, a long, curved red bill, and red legs. No partridge shows black plumage or red bare parts at any age.
• Flight views: Grey Partridge in flight shows short, rounded wings and a compact body, with no strong contrast or gloss. Choughs in flight show long, broad wings, a wedge-shaped tail, and all-black coloration with a striking red bill visible at close range.

Grey Partridge is a ground-dwelling, secretive bird, often seen walking or crouching in open fields and only flying when flushed, usually for a short distance with rapid, whirring wingbeats. Red-billed Chough is highly aerial, often seen performing acrobatic flight maneuvers, soaring, and gliding along cliffs or over open ground. Choughs are gregarious and often feed or fly in noisy groups, while partridges are more likely to be seen in small, quiet coveys on the ground.

Grey Partridge prefers lowland farmland, grassy fields, and open country, especially near crops or hedgerows. They are rarely found in mountainous or rocky areas. Red-billed Chough is strongly associated with coastal cliffs, upland pastures, and mountainous regions, and only locally in lowland areas where old buildings provide nest sites. If you see a bird in a rocky coastal or highland setting, chough is far more likely; in arable fields or lowland grassland, partridge is expected.

Grey Partridge gives a harsh, high-pitched "kieerr-ik" and a repeated "rick rick rick" when flushed. Red-billed Chough has a loud, ringing "chee-ow" call, much clearer and more musical than any partridge sound. The chough's call carries far and is often given in flight or when perched on cliffs. Partridge calls are more likely heard at close range and are less resonant.