I feel like calling these photos "taken by a chicken" is fairly misleading. The photos are taken automatically when a chicken wanders in front of a motion detector.
To test the claim with a similar example, let's say I run a red light which triggers a red light cam to take a picture of me and my car. I don't think I can claim that I took that photo, or that it is a selfie.
To test the claim with a similar example, let's say I run a red light which triggers a red light cam to take a picture of me and my car. I don't think I can claim that I took that photo, or that it is a selfie.