In the PC Carnivores games, the Wind Indicator is in the bottom left corner and the Compass is in the bottom right corner. In the mobile games, the two indicators were combined together for compactness.
The Wind Indicator indicates which way the wind is blowing. This determines the likelihood of an animal detecting you by scent. If the wind is blowing towards you, your scent is being blown away from the animal and you will be less likely to be detected; on the other hand, if the wind is blowing away from you, your scent is being carried directly to the animal so it will sense you more easily. The Wind Indicator also indicates the strength of the wind.