It can be a bit of a struggle to do much gardening during January and February. Whilst the intention may be there often the weather is against us. If you can bear to get out in the garden/allotment now though is the perfect time for getting the structure in place.
Trees can be pruned (with the exception of stone fruit such as plums, cherries, peaches etc) as can fruit bushes, raspberry canes, blackberries and tayberries etc. Branches which have been pruned can be stacked in a corner out of the way. Beetles will be one of the first to use the wood, boring into it. Then solitary bees may nest in the logs. Any hollow stems will also be used by solitary bees and other insects such as lacewings.