Birdhouse Great

Any bird experts know of this behaviour?
a little bird that has appeared in our garden,i'm not sure what he is but from the looks of the RSPB site it is a coal or a great tit.
We have been watching him for a few days, as he makes his way in and out of the birdhouse my daughter built.
We decided to go over yesterday and take a peek inside. I expected to see some evidence of nest building, but instead we saw the funniest thing. The bird house was 3/4 full of sunflower seeds, and nothing BUT sunflower seeds!
We love the idea that he is gathering these up from one specific place and bringing them to our birdhouse to woo a lady friend with his great stash- maybe he has a gal in mind that favours sunflower seeds?
I know nothing about birds and i wondered if anyone was familiar with this, or can enlighten me to the reasons behind this funny behaviour.
We live in a devlopment of houses in a rural seaside location, if that helps.
hello my dear ~ not too sure about this, but it could be that he's [?] just storing up, or its part of the mating game.
You can always email the BTO ~ this is the British Trust of Ornithology and they will probably be able to tell you wants taking place.
Hope this helps.
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