Introducing heterogeneous mobile devices, such as mobile phones into the large scale sparse wireless sensor networks is a promising research direction. These devices acting as mobile sinks offer many benefits to the network. For instance, they help to improve scalability, maintain load balance, conserve energy, prolong network lifetime and implement commercially. The paper investigates the impacts of different features and behavior of mobile sinks on the hybrid wireless sensor networks. Analysis and simulation results show that, instead of deploying mobile sinks as much as possible, choosing appropriate number, transmission range, velocity and gathering mode of the sink nodes can significantly decrease the average end-to-end data delivery delay and improve the energy conservation. The comparisons of performance metrics between fixed sinks and mobile sinks are also made in sparse networks along with the results that mobile sinks can bring higher data success rate and energy balance. Ca...