A real photo can look composited when parts of the scene seem lit or rendered differently.

In this case, the biggest cue is likely mismatched lighting: the birds and nearby grass appear to have hard, bright frontal light, while the foreground and background look softer and dimmer. When light direction, contrast, or brightness don’t seem consistent across the frame, viewers often read it as a cut-and-paste effect.

Exposure also matters. White birds against a darker background can easily become slightly overexposed, which wipes out feather detail. If the birds lose texture while the grass and ground still show detail, the subjects can look painted or artificial.

Flash can create a similar “diorama” look: a flash-lit subject against a naturally lit background often appears separated from the scene. Even without flash, a brief patch of sun on the birds under otherwise cloudy conditions can produce the same feel.

Heavy post-processing can add to it. Attempts to recover highlights or increase contrast may make the birds look flatter or less natural than the rest of the image.

So the likely causes are inconsistent-looking light, blown highlights on white feathers, and/or strong processing—not necessarily fakery.