While traditional, motionless scarecrows do work against “pest birds” (e.g. crows and blackbirds), the effect is almost always temporary. ... Researchers have learned that those with realistic facial features and brightly colored clothes are slightly better at shooing away birds.

Do scarecrows scare crows away?

Stationary scarecrows may keep the crows away for a short period of time, but they quickly become used to them. Moving scarecrows around every few days does help, but this can be labor intensive. Modern scarecrows use technology to keep the birds away.

What will scare a crow away?

Highly reflective Mylar® tape or bird tape, hung in streamers or twisted and strung to make a temporary fence can frighten crows away. Devices with reflective surfaces that spin or flap in the breeze can frighten crows.