Field grasshopper singing on rocks in Picos de Europa

Field grasshopper singing on rocks in Picos de Europa

Observation - Field grasshopper singing on rocks in Picos de Europa - Global. Description: Lots of these small field grasshoppers sat around on boulders singing in late pm sunshine at round 1500m in the Picos de Europa mountains in Spain. A Chorthippus I think, but don't know how to separate C. brunneus, mollis, biguttulus and other lookalikes

Lots of these small field grasshoppers sat around on boulders singing in late pm sunshine at round 1500m in the Picos de Europa mountains in Spain. A Chorthippus I think, but don't know how to separate C. brunneus, mollis, biguttulus and other lookalikes (to me), or maybe only the songs separate them for sure? This Swiss site has good pics, http://www.orthoptera.ch/arten/category/chorthippus but I can't find good location info to know which sp. is likely in the Picos.