Bird feeders, where have the birds gone ?

For the last couple of months i have noticed quite a dramatic decline of the number of birds visiting my bird feeders, having had the feeders for about 9 months now i was wondering 

if it was the time of year ? or something else. I regular change the bird food and keep the feeders clean, and change the water in the bird bath.

Not sure whether the food was wrong for the time of year so i changed the food giving them a variety without success. Has anybody any ideas ? If so your comments would be most welcome.

I have Included a photo of a robin in the bird bath