Is the sigma 300 600mm f 4 dg os sports long enough for birds?

Here is what the site says about that.

From Sigma 300-600mm f/4 DG OS Sports: Sigma 300-600mm f/4 DG OS Sports: A zoom lens by Sigma for Full frame cameras, 300-600mm f/4. A constant f/4 super-telephoto zoom for wildlife and sport. Specs - Maker: Sigma - Focal length: 300-600mm (zoom) - Maximum aperture: f/4 - Made for: Full frame sensors - Mounts: Sony E, L-Mount - Stabilised: yes - Autofocus: yes What it frames like - On full frame (Sony E, L-Mount): as marked, 300-600mm. - On APS-C (Sony E, L-Mount): ...

From Sigma 60-600mm f/4.5-6.3 DG OS HSM Sports: Sigma 60-600mm f/4.5-6.3 DG OS HSM Sports: A zoom lens by Sigma for Full frame cameras, 60-600mm f/4.5-6.3.

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