Overwintered colonies should be looked at now. Remove the winter cover and stow away until fall. The hive can be broke down to clean off the debris that is on the bottom board. This can be quite a bit, bring a box with you and put the debris in the box. Discard properly later.
Give the hive a reversal as I described in a previous post. Check the egg laying pattern of the queen. Sometimes it is not uncommon to find that you are queenless and a new queen should be installed as soon as possible.
If the queen looks good make sure there is a pollen patty on the top bars of every box. This makes sure that pollen is available to the bees on any level of the hive. It does not have to be a full patty, a 1/3 to 1/2 patty works. Replace as needed. There is natural pollen just starting to come in right now. But the bees have more than likely ransacked their stored up pollen, so pollen patties should be in place for a few weeks.