ブラジルシギダチョウ 対 アオアシシギダチョウ

The most reliable field mark to separate Brazilian Tinamou from Grey-legged Tinamou is the leg color: Grey-legged Tinamou has distinctive slate-grey legs, while Brazilian Tinamou does not show this feature. In addition, Grey-legged Tinamou males have a dark crown and both sexes show a rusty neck and upper back with a scaly brown-black body, while Brazilian Tinamou lacks these specific head and neck contrasts. Habitat can also help: Brazilian Tinamou is found in moist lowland Amazonian forest, while Grey-legged Tinamou prefers white-sand forests and dry shrubland. Size is slightly helpful, as Brazilian Tinamou is heavier, but this is hard to judge in the field. Focus on leg color, head pattern, and habitat context for the best separation.

1. Leg color is the top field mark: Grey-legged Tinamou always shows slate-grey legs, visible if the bird is walking or standing. Brazilian Tinamou lacks this feature.
2. Head and neck pattern: Grey-legged Tinamou males have a dark crown, while females have a fully rusty head. Both sexes show a rusty neck and upper back, which is not described for Brazilian Tinamou.
3. Body and wing pattern: Grey-legged Tinamou has a scaly brownish-black body and wings; females have additional markings on back and wings. Brazilian Tinamou does not have these specific scaly or marked patterns described.
4. Eye color: Grey-legged Tinamou has a pronounced black eye, which may stand out in good light. No such feature is noted for Brazilian Tinamou.
5. Tail: Both species have a small, hidden tail typical of Crypturellus; tail shape is not diagnostic.
6. Habitat context: If found in white-sand forest, dry shrubland, or poor-soil Amazonian habitats, Grey-legged is much more likely. In classic moist lowland rainforest, especially away from white-sand patches, Brazilian is favored.
7. Behavior: Both are shy and ground-dwelling, but Grey-legged is noted as particularly discreet and a weak flyer. This is not a reliable separation in the field.
8. Size: Brazilian Tinamou is heavier (422.5g) but both are small tinamous; size is rarely useful unless birds are side-by-side.
9. Sex differences: Only Grey-legged Tinamou shows strong sexual dimorphism in head pattern (dark crown in males, rusty head in females). Brazilian Tinamou does not have sex-specific head color described.
10. Juvenile/immature marks: No age-specific upperwing or flight pattern differences are described for either species; do not rely on these for separation.
11. Barring and scaly pattern: Grey-legged Tinamou can be confused with Variegated Tinamou due to scaly pattern, but between these two, only Grey-legged shows this scaly brown-black effect.
12. Voice: No vocal differences are described; do not use voice for separation.
13. Distribution overlap: Both can occur in northern Brazil, but Grey-legged's range is patchier and more tied to white-sand and dry habitats.
14. Crown color: If you see a tinamou with a dark crown (male) or a fully rusty head (female), suspect Grey-legged.
15. When in doubt: If leg color is visible and not slate-grey, and the bird is in humid lowland forest, Brazilian Tinamou is more likely.

Brazilian Tinamou is the heavier of the two, with an average body mass of 422.5g [wikidata], while no specific mass is given for Grey-legged Tinamou, but it is described as a small tinamou [wikipedia]. Both are small, ground-dwelling birds, but the difference in weight is subtle and rarely diagnostic in the field unless seen side-by-side. Height for Grey-legged Tinamou is 28–31 cm, but direct comparison for Brazilian Tinamou is not available. Use structural and plumage differences over size.

There are no detailed notes on age-specific upperwing patterns or juvenile flight marks for either species, so focus on adult plumage. Grey-legged Tinamou males have a prominent dark crown, while females have a fully rusty head; both sexes show a rusty neck and upper back, with a scaly brownish-black body and wings. Females also have markings on their backs and wings. The Grey-legged Tinamou's legs are slate grey, which is unique among these two. Brazilian Tinamou lacks mention of any strong head or neck color contrast and does not have the slate-grey legs. Both species have a small, hidden tail typical of Crypturellus tinamous. If you see a tinamou with a rusty neck and grey legs, it's Grey-legged; if these are absent, Brazilian is more likely.

Both species are ground-dwelling and secretive, rarely seen in the open. Grey-legged Tinamou is described as a weak flyer and very discreet, often remaining inconspicuous in dense foliage. There is no behavioral trait noted for Brazilian Tinamou that would reliably separate it from Grey-legged Tinamou in the field.

Brazilian Tinamou is found in tropical moist lowland forests of Amazonian South America, favoring humid, dense forest. Grey-legged Tinamou, in contrast, is a specialist of Amazonian white-sand forests and dry shrubland up to 500m, often in fragmented and poor-soil habitats with low canopies and dense undergrowth. If you are in classic humid Amazonian terra firme, Brazilian is more likely; in white-sand or dry shrubland, especially with low canopy, Grey-legged is favored.