Predictors of Gull-billed tern (Gelochelidon nilotica) nest survival in artificial coastal saltpans, Bohai Bay, China.

Weipan Lei,Zhengwang Zhang,Fuxing Wu,Huw Lloyd

doi:10.7717/peerj.10054

Weipan Lei, Zhengwang Zhang + Show 2 more

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https://doi.org/10.7717/peerj.10054

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Abstract

BackgroundCoastal saltpans are a common supratidal human-modified wetland habitat found within many coastal landscape mosaics. Commercial salt production and aquaculture practices often result in the creation of exposed coastal substrates that could provide suitable breeding habitat for waterbird populations; however, few studies have quantified waterbird breeding success in these artificial wetlands.MethodsHere we examine the nesting behavior of the Gull-billed tern (Gelochelidon nilotica) breeding in the Nanpu coastal saltpans of Bohai Bay, Yellow Sea, China over three consecutive nesting seasons (2017–2019) by using nest survival model in Program MARK.ResultsThe results revealed that nest survival of Gull-billed terns in coastal saltpans (0.697) was higher than previously published estimates from other regions, with an estimated daily survival rate (DSR) of 0.982 ± 0.001 (±95% CI). High nest survival was mainly attributed to low levels of human disturbances and low predation rates, while exposure to strong winds, flooding and silting were the main factors causing nest failure. Model-averaged estimates revealed that eggs laid in nests located on ‘habitat islands’ with feather or clam shell substrates were most likely to hatch. Initiation date, nest age, clutch size and quadratic effects of nearest-neighbor distance, nearest distance to road and nearest distance to water were all significant predictors of nest success, but the nest survival declined overall from 2017 to 2019 due to the degradation and loss of breeding habitat anthropogenically caused by rising water levels.DiscussionCoastal saltpans represent an alternative breeding habitat for the Gull-billed tern populations in Bohai Bay, but conservation management should prioritize flood prevention to improve the extent and quality of breeding habitat, concurrent with efforts to create further ‘habitat islands’ with suitable nesting substrate.

Highlights

Human disturbance and land-use changes driven by tidal reclamation have resulted in the loss and degradation of coastal wetland ecosystems globally (Delany et al, 2009; Hoegh-Guldberg & Bruno, 2010)
We identified a 60-day nesting season for Gull-billed tern at our Bohai Bay study site, which began on 9 May and ended on 7 July, resulting in 59 daily intervals for estimating the daily nest survival
We assumed that the average incubation period of Gull-billed tern at Bohai Bay was 24 days, which resulted in average nest survival of 64.7%

Summary

Introduction

Human disturbance and land-use changes driven by tidal reclamation have resulted in the loss and degradation of coastal wetland ecosystems globally (Delany et al, 2009; Hoegh-Guldberg & Bruno, 2010). Artificial wetlands are rapidly expanding, caused by commercial enterprises such as salt production, and are creating a combined landscape mosaic of both anthropogenic and natural origins that can provide alternative or supplemental breeding and foraging habitats for waterbird species (Houston et al, 2012; Bluso-Demers et al, 2016; Rocha et al, 2017; Lei et al, 2018; Barnagaud et al, 2019). Salt production creates ‘habitat islands’ that can serve as breeding habitats for a small number of waterbird species (Britton & Johnson, 1987; Yasué, Patterson & Dearden, 2007; Chokri & Selmi, 2011) This has led some authors to suggest that adequate conservation management of saltpans could provide complementary habitat to help alleviate some of the impact on waterbirds caused by the loss of natural wetlands (e.g., Masero, 2003; Béchet et al, 2009; Rocha et al, 2017). Coastal saltpans represent an alternative breeding habitat for the Gullbilled tern populations in Bohai Bay, but conservation management should prioritize flood prevention to improve the extent and quality of breeding habitat, concurrent with efforts to create further ‘habitat islands’ with suitable nesting substrate

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