Hints on how to separate these similar Neotropical species? (1 Viewer)

In preparation for my trip to Iwokrama later this month, I've been trying to brush up on my ID skills. I've found several species that may give me problems when trying to separate them in the field. Please give me some hints on how to tell them apart.

Scarlet Macaw vs. Red-and-green Macaw

These may not be too hard to separate when perched, but what's the best way to tell them apart whey they're in flight? Wing coverts or presence or absence of lines on face? Are the calls any different?

Marail Guan vs. Spix's Guan

I have no idea about how to separate these two, and I only have very limited experience with Spix's.

Ruddy Pigeon vs. Plumbeous Pigeon

I've read through the discussion about Arthur Grosset's Neotropical pigeon (link) which ( I guess) comes to the conclusion that pale eye=Plumbeous Pigeon. Is that also true for the subspecies at Iwokrama? (if it is a different one) I've been working on learning the voices, so those should help me if I encounter a vocalising one.

OK, listened to Boesman & read Hilty....
The pigeons: Eye colour is good, but (young?) Plumbeous can have reddish brown eyes. If I read Hilty correctly, Ruddy has rufous underwing coverts & underside of primaries, while in Plumbeous, they're grey. However, S of the Orinoco they're "almost indistinguishable" (although Plumbeous remains "greyer", and is larger...), which probably extends to Guyana... Sound is another difference: 4-note call of Ruddy is "an octave" higher and faster.
Macaws: median upper-wing coverts (yellow in Scarlet, green in Red-and-green) and lines in face (no: Scarlet, yes: R&G). The calls are different: Scarlet sound like a "voiceless" scratch compared to R&G which has a "ground tone" (Hilty calls it a falsetto).
Guans: Marail is smaller than Spix's, with shorter tarsi. Sound is a good clue: Spix's sounds goose-like (I'd say: flamingo-like), while Marail sounds more like a fouraging chicken...

the pigeons are a nightmare, depends where you are i think....

the macaws are easy - Scarlet has yellow in wing covs

no experience with Mareil Guan though - sorry

Hi Chris

I can't help, but will watch the thread with some interest. As you know I shall be following in your tracks a few days later. I have not long put my 'Hilty' book down. It's going to be my first Neo Tropical experience so I'm going to struggle. Never mind though, as I'm sure there are worse things to struggle with and once I get a little knowledge it will give me a good excuse to return to expand upon it. Enjoy your trip.

Best wishes

The main things have already been listed:

The Macaws: Facial-pattern is useful when perched, but of very little use in flight. Colour of the wing-coverts is good - as long as you remember that seeing green doesn't mean that it's a Red-and-Green Macaw, as the wing-coverts of the Scarlet are both green and yellow. See for example this Scarlet with rather limited yellow that originally had a mistaken ID attached:

http://www.birdforum.net/pp_gallery/showphoto.php/photo/70567/sort/1/cat/all/page/1

If seen together note size (Scarlet small) and hue of the red (deeper red in Red-and-Green). The last feature can sometimes be useful in flight where especially the tail of the Red-and-Green often appear almost maroon from above, where the tail of the Scarlet appear more of a "normal" red. Of course this is something one should use with care, as light easily can have an effect on this. Another hint is the tail-lenght (proportionally longer in Scarlet), but this require a fair level of experiance with the two species before really being useful. Their voices are very alike, but marginally coarser and deeper in the Scarlet.

The Guans: Spix's Guan is larger and longer-legged as noted by Xenospiza.

The Pigeons: Notoriously difficult. Eye-colour is useful (dark to pale in Plumbeous, dark in Ruddy). Other useful features are size (Plumbeous larger), bill-lenght (relatively shorter & finer in Ruddy) and hue (more vinaceous in Ruddy). Still, in the vast majority of situations the voice is best. Ruddy typically has a four-noted "whu-whu whuh-whuuh" that often is repeated over and over again. The voice of the Plumbeous varies geographically and I'm not quite sure about the vocalization in Guyana. Anyway, it range from being three-noted to four-noted in northern South America. Obviously, populations with the three-noted vocalization are easier to separate from the Ruddy. In areas where the Plumbeous has the four-noted song (as in Ruddy) one has to rely on pitch as it is clearly lower in the Plumbeous. Obviously, these vocalizations shouldn't be confused with the typical growling "purr-rr" many species in this genus have.