These references support the bird-identification logic used in this guide and are useful for cross-checking field marks.
House Finch, All About Birds (Official, Cornell Lab of Ornithology) - Official Cornell Lab species guide used for field-mark, habitat, and behavior checks.
Purple Finch, All About Birds (Official, Cornell Lab of Ornithology) - Official Cornell Lab species guide used for field-mark, habitat, and behavior checks.
Tricky Finches Tip Sheet (Official, Cornell Lab of Ornithology) - Detailed comparison resource for House Finch, Purple Finch, and Cassin's Finch.