Silvery Grebe - plumage difference (1 Viewer)

the Opus entry http://www.birdforum.net/opus/Silvery_Grebe shows two images that are quite different. The geographic info indicates that the two should belong to different subspecies, but is the plumage difference caused by subspecies, age, or time of year?

thanks
Niels

According to Birds of the High Andes, the northern form has a white throat and drab plumes, the southern a grey throat and yellow plumes – as the pictures show!

I found two forms mentioned ("northern" & "southern") the northern looking like the first image. They do look very different. Future split?

Thanks :t:

I have edited the entry accordingly.

Cheers
Niels

halftwo said:

I found two forms mentioned ("northern" & "southern") the northern looking like the first image. They do look very different. Future split?

Click to expand...

Who knows! I guess that mostly depends on what happens in the area of overlap if such an area exists (unfortunately, I need books on SA birds).

Cheers
Niels

Taken from the taxonomic notes in the excellent Birds of Chile (Jaramillo, Burke and Beadle):-

"Silvery Grebe: Two well marked forms occur in Chile, nominate occipitalis in the centre and south, and the altiplano juninensis in the north. Southern occipitalis is migratory, moving north in the winter, at which season it is mainly coastal, while juninensis is apparently sedentary. The differences between the two are marked, and more obvious than has been generally portrayed. In plumage juninensis is much closer to the flightless Junin Grebe of Peru than it is to occipitalis. Fjeldsa and Krabbe (1990) describe differences in vocalisations between them which match our observations. Our study of specimens and live birds suggests that juninensis changes little in its facial pattern while occipitalis has marked breeding and non-breeding plumages. Differences in plumage, seasonal change in appearance, migratory tendency, voice and habitat suggest that the two are better classified as species."

Here's a couple of my photos of the two forms taken in the Austral winter, the group of juninensis was taken in the stunning Lauca NP in the extreme north of Chile while the (non-breeding) occipitalis was taken at Potrerillos in the Andes above Mendoza, central Argentina