Unmanned aerial vehicle (UAV)-based communication system has become an emerging area to be developed recently as the capability of the UAV to communicate with other communication nodes with ease by moving freely in the air. Several wireless sensor network (WSN) systems utilize this advantage to improve the system performance by treating the UAV as a mobile sink node to collect the data from the source nodes. This way, the total number of the deployed sink nodes used will be reduced while still preserving an adequate system performance. However, several studies in the past only considered network performance in the term of packet delivery rate and throughput as the primary objective when designing a UAV-based communication protocol. The existing studies did not consider any attention on the energy consumption of the mobile nodes, even though this is a critical issue as most of the mobile nodes relies only on battery to move around and communicate with other nodes. In this paper, a novel data-link layer UAV-based communication protocol called NSL-MAC is proposed to improve the performance of the UAV-based data gathering system in WSN while still preserving minimum energy usage. The presented results in this study show a promising feature of the proposed MAC protocol in the term of packet delivery ratio of the network and energy consumption of the UAV, which can increase the network lifetime.