Thanks Mick!
The reason you didn't see any other bunting other than Corn Bunting along the coastal routes you mention is nothing to do with having a guide ;.)
The fact is there aren't any really, except for Ortolan Buntings on autumn passage and these can be pretty discreet. Rock Bunting occurs inland - just some 4-5kms from where you were walking on the shale hills. You were on limestone. If you work north of villages like Barão de São João or Bensafrim and look for driveable (many) tracks taking you to higher ground they are straightforward to find - at least if you persevere a little! I think what throws most people to think they are only found in Monchique is the myth that they need rocky habitats. Along the coast from Luz - Burgâu - Salema - Sagres there are a lot of rocky places that look ideal - but the species is absent. However on the shale scrublands and thin woodland they can be fairly common, favouring areas with an element of bare ground or tracks - practically no rocky habitats in these areas though!
Autumn 2009 brought a record of a single Rock Bunting near Sagres, which is unusual as they appear to be extremely sedentary - staying in breeding habitat all year.
As for other buntings in the Algarve:
Reed Bunting - winter visitor in small numbers in reedbeds.
Snow Bunting - Rarity; 2 records - an old one from Meia Praia near Alvor Estuary and another in Dec. 1999 that I found at Vale Santo, Sagres with Skylarks.
Little Bunting - Rarity; 1 or maybe 2 birds in Nov and Dec 2009 at the ricefields at Nossa Senhora de Rosario, Estômbar, Silves.
Rustic Bunting - Rarity;1 at the same site same time as the Little above.
Ortolan Bunting - scarce but regular in dry grasslands in Sept and Oct throughout but especially on the Sagres peninsula - I have found groups of up to 40 inds occasionally although normally singles or single figures.
Cirl Bunting - fairly common resident in a few areas, mainly in the northern parts of Lagos, Vila do Bispo and Aljezur counties.
Corn Bunting - abundant in many areas all year with winter flocks in excess of 100 birds regular
Best wishes
Simon
http://algarvebirdman.com/