Birding bioculars must be handheld, neither too big nor too heavy.

Sharp or higher-end optics is indispensable because birding demands details.

For birds watching, one must focus quickly and so center focusing is better than individual focusing.

The binoculars we recommend for birding are ranked by suitability for birding with 1-5 stars.

5 star: 8x42 MZ roof prism, 10x42 MZ roof prism, 8x40 FB
4 star: 7x50 HG, 10x50 HG, 7x50 CB (LE FMC version)
3 star: 8x25 MZ roof prism, 7x50MS, 10x50 MS
2 star: 25/40x100 standard, 25/40x100 painted

Besides suitability, You should probably consider the cost performance of each model using the cost performance formula.