マユダチペンギン 対 マカロニペンギン

The most reliable field mark between Erect-crested and Macaroni Penguins is the shape and position of the yellow crest: Erect-crested shows a short, erect crest that rises sharply above the eye, while Macaroni's crest starts from the forehead and sweeps back horizontally. Both are large, robust crested penguins with black upperparts and white underparts, but subtle differences in bill size, facial skin, and crest structure help separate them. Immature birds are trickier, as both lack full crests, but Macaroni immatures show a duller bill and underdeveloped plumes. In the field, context and colony location can also help, but focus on head pattern and crest shape for the best separation.

1. Crest shape and position (adults): Erect-crested Penguin's yellow crest is short, thick, and stands erect above the eye, giving a bushy, upright look. Macaroni Penguin's crest starts at the forehead and sweeps back horizontally, never standing up above the eye. This is the single most reliable mark in close views.
2. Crest origin: On Erect-crested, the yellow stripe begins above the eye; on Macaroni, it starts at the center of the forehead and extends back.
3. Bill size and structure: Both have large, thick bills, but Erect-crested males are especially robust-billed. Macaroni's bill is orange-brown and bulbous, with a patch of pinkish bare skin at the base extending to the eye, which is more prominent than in Erect-crested.
4. Facial skin: Macaroni Penguin shows a distinct patch of pink bare skin from the bill base to the eye, often visible at close range. This is less evident or absent in Erect-crested.
5. Iris color: Macaroni has a red iris, which can be seen in good light. Erect-crested's iris color is not described as distinctive.
6. Immature birds: Macaroni immatures have a smaller, duller brown bill, dark grey chin and throat, and lack a full crest (just scattered yellow feathers). Erect-crested immatures are not well described but likely lack a full crest as well; separation at this age is difficult and may not be possible without close examination.
7. Upperwing pattern: No distinctive differences in upperwing or flight pattern are described for either species at any age; do not rely on this in flight views.
8. Plumage gloss: Both species' black upperparts show a bluish sheen when fresh and may appear browner when worn; this is not a useful separation mark.
9. Sexual dimorphism: Both species show slight size and bill differences between sexes, but these are subtle and not reliable for field ID.
10. Colony context: If seen breeding on the Bounty or Antipodes Islands, Erect-crested is expected. Elsewhere in the Subantarctic or Antarctic, Macaroni is more likely. However, vagrancy is possible, so always check crest shape.
11. Behavior: Both species show similar social and agonistic behaviors; do not use behavior alone for separation.
12. Size: Erect-crested is on average heavier, but overlap is extensive; do not use size unless birds are together.
13. Leg and foot color: Macaroni has pink legs and feet, but this is not described for Erect-crested and may not be diagnostic.
14. Vocalizations: No distinctive vocal differences are described; do not rely on voice for separation.
15. Seasonal variation: Both species undergo weight changes with breeding and moult, but this does not aid identification.

Both species are among the largest crested penguins, with considerable overlap in length and mass. Erect-crested Penguin is slightly heavier on average (males up to 6.38 kg, females 5.4 kg [wikipedia]), making it the largest crested penguin, while Macaroni Penguin averages about 5 kg (4.985 kg [wikidata]), with males reaching up to 6.4 kg before moult. Both reach similar lengths (up to 70 cm), so size alone is not a reliable field mark unless birds are side by side.

• Juveniles/Immatures: Both species lack fully developed crests when young, but Macaroni immatures have a duller brown bill, dark grey chin and throat, and only scattered yellow head feathers. Erect-crested immatures are poorly described, but likely have reduced crest as well, making separation challenging at this age. No distinctive upperwing or flight pattern differences are described for either species at any age.
• Adults: Erect-crested Penguin has a broad, bright yellow eyebrow-stripe that extends over the eye and forms a short, erect crest, standing up prominently. Macaroni Penguin's yellow crest starts at the center of the forehead and sweeps back horizontally to the nape, not standing erect above the eye. Macaroni also shows a patch of pinkish bare skin from the bill base to the eye and a red iris, while Erect-crested's facial skin is less described. Both have black upperparts with a bluish sheen (when fresh) and sharply demarcated white underparts.

Both species breed in dense colonies and show typical crested penguin social behaviors, including bill-jousting and mutual displays. Macaroni Penguins are noted for their elaborate visual and vocal displays, especially during the breeding season, including the 'ecstatic display' with loud braying and head waving. Erect-crested Penguin's behavior is less well documented, but likely similar given their close relationship. No major behavioral differences are noted that would help with field separation.

Erect-crested Penguin breeds only on the remote Bounty and Antipodes Islands of New Zealand, occasionally as a vagrant to other Southern Hemisphere coasts. Macaroni Penguin has a much wider breeding range, from the Subantarctic islands to the Antarctic Peninsula. If seen breeding on the Bounty or Antipodes Islands, Erect-crested is expected; elsewhere in the Subantarctic or Antarctic, Macaroni is more likely. Both species nest in large, rocky colonies, sometimes with other seabirds.