Hi Alejandro,
This second photo leads me in the same directon as before. Most Swifts (incl. Andean) have very weak legs. This means that they usually rest with their bodies touching the surface. Andean Swallow is rather striking, it being shiny white and dark brown (actually, in the field it appears white and black). Also, the pattern is different; i.e. underparts all white (incl. throat), except for the dark flanks and a band on the lower belly (at the legs). It would be the first (and lowest ever) record of Andean Swift at Pantanos de Villa. I am however, 99.9% certain it isn't a swift. I have to agree with Tim on Cliff Swallow, though I cant remember ever having seen one (juv. or ad.) with such a heavily speckled chest. This was what initially lead me to say Purple Martin. Females of this species are indeed speckled below & they often have the collar (though usually broader). However, jizz is wrong, and throat & forehead seems to have slight brownish hue (unlike the grey in female Purple). So, as said before, I agree with Tim: Cliff Swallow. It would be an juv./imm, due to (among others) the relatively pale forehead and throat. I would still like to hear a few comments on the heavily speckled chest, though.
If you want to see Andean Swifts, the place closest to Lima would be on the upper parts of the Santa Eulia road (it is often seen near the White-cheeked Cotinga site).
Yet again; it is indeed a very nice photo, and I am quite sure we have solved the ID now. Some of these ID's can be quite hard, especially as the current field guide to the birds of Peru is of questionable quality. It is very nice to see photos from that region. Brings back many memories of great birding and nice people. I can (and will) highly recommended Peru to anybody :t:
Regards, Rasmus.