Several questions? Why 10 seconds shutter delay? 1second is enough to dampen mirror slap.

IS needs to be off since you're on tripod. IS motors on tripod will produce motion on tripod.

What metering did you use? Should have been on Spot not Matrix or even center weighted. After you get the focus you want, turn focus to manual. Your scene has multiple complicating factors that could shift focus so hot the bird you want with a small spot.

ISO is probably maxed out for those cameras but don't think that is the problem.

If you want to do small birds, you need a bigger lens or good teleconverter

RCBlank - the EXIF data from the bird house is incomplete in that DPP shows ISO-0 which is not correct. DPP also cannot show the focus point to assess the results verses the point of focus.

The two birds flying by the orange barrier is hard to say what is going on. You have continuous focus active, but the focus point does not fall on either of the birds. You have aperture at f/8, ISO-800, and shutter at 1/5000. I have the same f/4 non IS version of this lens. I'd suggest two items:

1. Unless you need a larger depth of field or less light, set the aperture at f/5 for all shooting scenarios.

2. For a non IS enabled zoom on a cropped sensor, use a shutter 1/400 for hand holding or faster based on light and / or freezing action of the scene.

I purchased the tripod ring / collar for this lens to use with a monopod or tripod. This is an annoying extra expense, but I find the collar on the lens very useful when using support such as a monopod or tripod.

Both photos look heavily cropped with the birdhouse being additionally processed based on the truncated EXIF data. To better answer what to do to different, we'd have to see the original. Your distance to subject may be the issue which is harder to gage from the cropped / processed examples.