Weavers: Hunt for a Super Zoom lens

It's been a while since my last post so I do apologise for not sharing more of late. I've been doing loads of research for the ideal super zoom lens that can be used for wildlife and birds in flight. I've hired lenses in the past but I'm at a point where I want to rather invest in my own but at the same time looking for a balance between quality, functionality and price. At this point I'm leaning toward the Sigma 150-600mm Contemporary f/5.6 - f/6.3. I should have checked the weather before I hired one a couple weeks ago on possibly the worst weekend of the summer. It rained pretty much all weekend. I had just an hour before sunset on the Sunday when the rain had stopped and I could get out and test the lens. I drove out to Botanic Gardens in Durban and decided to practice with the weavers and a couple other water birds. Lighting was flat, cloudy and getting dark quick but I had to squeeze off a few shots before returning the lens the following morning. I had to shoot wide open and at high ISO to get relatively sharp eyes. I could have gone faster to get freeze frame wingtips but that would have meant too noisy images. In hind sight, I quite like the wing motion blur. Here are a few of the resultant images. Let me know what you think in the comments field below.

Click on the images for a better viewing experience