What is the most reliable immediate visual check to separate the Orange-headed Tanager from the male Western Tanager?

Answer

The Orange-headed Tanager's body is consistently blue-gray, never solid yellow

The Orange-headed Tanager's body is consistently blue-gray, whereas the male Western Tanager has a clean, bright yellow body, making the body color difference the most reliable immediate separation.

What is the most reliable immediate visual check to separate the Orange-headed Tanager from the male Western Tanager?
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