This I wrote 6 years ago in a thread:
4 x 4, I am not sure if this is needed, but can be an advantage because some streets in the mountain are a little bit rough e.g. to El Yeso.
From Santiago to Cayon del Maipo some inexpensive Cabanas not far from Santiago. They are not difficult to find.
In Cayon del maypo e.g. is Refugio de Aleman a nice hut from German Adino Club. The chief is from England.
Around the hut is possible to see some birds, but in opposite of the hut is an protected area ( small fee for entry ).
El Yeso is good for Diadem Sandpiper Plover, but also Bairds Sandpiper, South American Snipe, Crag Chilia, Dark Billed Cynclode, Grey flaked Cynclode and so on.
But in the mornig are different birds in the rock area along the lake.
From Larva ( 2.700 m altitude ) are some hikes for birding also with chance for Condor, but also Montain Caracara, White Side Hillstar, Rufous Naped Ground Tyrant and at the mountain nearby I saw also Black faced Ibis.
Farellones ( almost 2.500 m ) has bushes and trees where is possible to see different kind birds.
There are accomodations from the Andino Club, but very basic ( for me it was enough, I had a sleeping bag with me ).
Lampa reserve ( 30 km north of the airport ) is worth to see, even if it is dry and you have no chance to see Painted Snipe, but also herons, ducks, coots and some waders are there.
La Campana national park is not to far from Santiago and there are 6 or 9 endemic birds of Chile.
Rio Clarillo reserve is very near to Santiago.
It is a big suprise in this dry area with very rare vegation and you will in the forest area in the reserve ( ask for the entrance time, not sure 8 a.m ? ).
Good place for Giant Hummer, but also Moustached Turca, White-throated Tupaculo, Dusky Tupaculo and at the picnic place in front the entry also Chilean Pigeon.