Breeding Population Dynamics of Relict Gull (Larus relictus) in Hongjian Nur, Shaanxi, China

Simple Summary Long-term population monitoring is critical for informing the management and conservation of endangered species and for understanding population dynamics in response to changes in habitat suitability. We investigated breeding pairs and breeding islets of the Relict gull throughout Hongjian Nur from 2001 to 2020. We also analysed correlations between the breeding population and the breeding habitat, aiming to understand how environmental factors affect the breeding population. Our results suggest that the breeding population and breeding islets have been in an unstable status, and they show a positive correlation. Habitat restoration can be used as a compensatory method for breeding population restoration in Hongjian Nur in the future. Hongjian Nur is an important breeding and stopover area for the globally endangered Relict gull (Larus relictus). This is where the species was first found in 2000. The breeding population of this species was monitored over the long term by directly counting nests from 2001 to 2020 in Hongjian Nur, Shaanxi, China. Our results suggest that breeding pairs increased rapidly, from 87 nests in 2001 to 7708 nests in 2010; at this point, the breeding population accounted for more than 85% of the global total, and was at the highest value during the past two decades. Subsequently, breeding pairs continued to decrease dramatically and reached a minimum number of 2054 nests in 2015, approximately 70% less than at their peak. In view of this situation, breeding islets were restored in 2014 and 2017, and the breeding population recovered slowly. Due to the changing ecological environment, breeding islets showed the same instability as the breeding population. Our conclusions support previous research, highlighting the importance of water level.