Performance improvement in wireless sensor networks (WSNs) through the use of reconfigurable cluster heads is addressed in this paper. The performance of a WSN is limited by the scarce on-board power in each sensor node. Since the sensed data in the WSN is transmitted to a sink from node to node in a multi-hop fashion, elimination of the redundancies in the data and aggregation of the data from multiple sources can improve the throughput and lifetime of the network. This, in practice, is infeasible because the aggregation to be performed depends on the requirements of the end user/application and is either unknown at the time of deployment or changes over time. In this paper, the problem of implementing dynamic data aggregation in WSNs is addressed through the design of reconfigurable cluster heads (RCHs) using Field Programmable Gate Arrays (FPGAs). Our results demonstrate that different data aggregation algorithms can be efficiently implemented on the RCHs in run-time. Such an implementation provides the necessary flexibility demanded by applications, while resulting in significant reduction in the query processing time and the overall power consumption in the network.