Long Tailed Tits

There seems to be a great reduction in numbers of Long Tailed Tits this year.

For the last five/six winters we have had a flock with 12-16 LTT regularly visiting all winter, three or four times a day.

This year there is one LTT who visits regularly in a mixed tit flock. 

 We have five/six pairs of siskins, and all the normal visitors (including a coal tit that were missing most of last year) but just this single LTT.

 Do you know any reason for this decline.

 Feed mainly nuts and seeds (lot of sunflower hearts this year to help them along)