White-crested or White-bellied Tyrannulet, South Brazil? (1 Viewer)

[tjbirder999]

I had brief views of this bird at Sao Francisco de Paula near Rio Grande do Sul, south Brazil. To me, it seems much closer to White-bellied Tyrannulet, which is an uncommon winter visitor to the area, though a local (who knows way more than me on local birds, but has yet to seen White-bellied) says he thinks it is White-crested. I only have poor distant photos, but hopefully enough to identify it. Any comments welcome.
Thanks,

Tom

 

[pbjosh]

There is also a third possibility - Straneck's Tyrannulet, which will also be possible in winter in that area. The amount of white crest shown probably eliminates Straneck's but I'm not 100% certain on that so I mention it.

Of the other two, there is a touch of olive wash to the back and the belly looks to have a bit of yellowish wash. I've looked at a lot of photos of this species trio, and it can be really hard to judge from just a photo or two, but I might lean towards White-crested also, when considering the slight clues in the photos and the fact that White-crested is the default choice in RGdS, basically.

When in the field I generally only log to species when I hear them vocalizing clearly and even then, between White-crested and White-bellied, if both are expected I really prefer to see them well and judge back and belly color as the vocalizations are similar - some still consider them conspecific (I believe HBW did not/does not have these split, actually).

 

[THE_FERN]

I had brief views of this bird at Sao Francisco de Paula near Rio Grande do Sul, south Brazil. To me, it seems much closer to White-bellied Tyrannulet, which is an uncommon winter visitor to the area, though a local (who knows way more than me on local birds, but has yet to seen White-bellied) says he thinks it is White-crested. I only have poor distant photos, but hopefully enough to identify it. Any comments welcome.
Thanks,

Tom

Hmm I'm no expert here but: the only reasonably clear distinction I can see between them is that the upper parts of white-bellied are uniform grey upper parts with little or no contrast between neck and back, and [stronger] yellow wash on underparts. The latter seems a bit variable.

I'd suggest yours is white-crested, mostly because the upper parts appear quite strongly "patterned" with a clear distinction between crown, neck and back. the unders are pale yellow (supports white-bellied) but this character seems quite variable.

I don't know if there's been more recent research, but AFAIK, jury's out on whether these really are 2 different species.

 

[THE_FERN]

some still consider them conspecific (I believe HBW did not/does not have these split, actually).

what's your view, and why?

[Edit]: you've clearly more experience of these than most of us...

 

[tjbirder999]

Thanks for your comments pbjosh and THE_FERN. It looks like it is probably White-crested, though best left as uncertain. I need to get more experience with these species.

Tom

 

[pbjosh]

what's your view, and why?

[Edit]: you've clearly more experience of these than most of us...

I'd be shocked if they weren't sister species, but I'm not sure I'd lump them. They do separate by habitat and largely by range when breeding, there are plumage differences even if not always always diagnosable, there are voice differences even if not always diagnosable, and one is a seasonal migrant and the other not. The one thing I'm not certain of is what happens in central Argentina (Cordoba province and at least a bit of San Luis province) in the hilly areas where they must be breeding at least near to each other. I've not spent enough time there or read enough to know how they separate out.