I was out to the Kugelbake area to shoot some common terns. Unfortunately the wind direction was from south-east so it was rarely seen from front when the terns flew up from the water after they picked a fish as they mostly get up against the wind.

Common tern

First day I used the D500 with my Nikkor 200-400 and the hit rate of the AF-C was pretty good, although not all pictures got sharp. On Sunday I used the Sigma 150-600 under brighter conditions than Saturday. However the AF-C hit rate – having the same settings in the camera – was rather poor compared to the day before. Whenever the contrast behind the birds was more than sky or water, the Sigma very quickly lost focus and was not able to pickup on the bird again, no matter what I did. I tried nearly all combinations (Single point, multi points, group and 3-D) but compared to the Nikkor it was a poor performance.

Common tern