no kernel in sunflower seeds...why?

Anyone elses sunflowers have empty seeds?

I'm beginning to harvest some...the black oil seed seem fully developed but the large heads of white with grey stripe apparently did not all get pollinated.
This is the third year in a row I've noticed that only the outer inch or so of the large seed head has fully developed seeds.

In the past I've had to cover them to keep the goldfinches off and usually could tell when to cover by when a few seeds were missing.  Now they don't seem interested.

These are nice large heads, planted early and we do have pollinators, bumblebees and other bees.
Maybe they flowered too early? fewer pollinators?

Some of the seeds look full but are easily squished and some are just flat....less than half have seeds (I've spot checked and they feel solid.)

The outer ring pattern is usually poor pollination, the florets open from outside in over a week or so and if bees don't visit consistently through that window the inner ones miss out. Not much you can do really other than hope for good bee activity during flowering. My large-headed ones always have a thinner centre than the small oil types.

We have something similar going on here but with chokecherries. They bloom and seem to have adequate pollinators during that time but just a few berries per cluster. Years ago the chokecherries were very prolific on this farm, as many as you wanted to pick. Would say the last time I found any number was about 12 years ago. The bushes look healthy and they bloom as always but no fruit.

I grew Hidatsa heirloom sunflowers here for about 10 years, unfortunately my stored seed suddenly lost viability and with this my seed source. I will say sunflowers like space, the biggest heads usually had the most elbow room. Sunflowers are a wonderful plant and the seed placement in the heads is magical. I miss my heirloom sunflowers.

thank you both!
I think I'll try planting them later next year or stagger the plantings and see if it makes a difference in how well pollinated.
We do not have the number of bumblebees that we've always had in the past...honey bees in the neighborhood but not in big numbers.

I remember years ago I had (nanking?) cherry bushes that bloomed great but way too early for anyone to be around to pollinate...I would rarely get a handfull of fruit.

Now I'm thinking we have fewer goldfinches also...no flocks like we see other years.

We have cardinals though...
Just now we were watching several eating elderberries right outside the window....I planned to let the berries go this year anyway...maybe they will do some planting for us.