This is the 475th most frequent Serbian word.
срни
"Срни" is the plural form of "срна," meaning "does" (female deer) in English.
The word 'срни' here refers to deer (plural form), animals that inhabit mountainous regions.
Срни су често присутне у планинама.
Deer are often present in the mountains.
In this context, 'срни' (spelled the same way as the noun) is part of the phrase, and could appear metaphorically or in a poetic sentence.
Црне боје облака срни су наговештај кише.
The dark colors of the clouds are an indication of rain.
Here, 'срни' again refers to deer in plural form, describing their uncommon nature during daylight.