| Global loss and destruction of coastal wetlands have had a severe impact on the migration and breeding of many shorebirds.Wetland restoration and management are basic methods to improve birds’habitat use and reproduction.However,different wetland management methods’effects on bird reproduction are inconsistent.Previous studies have found that large areas of Suaeda salsa and dried-out abandoned fishponds in the Liaohekou Nature Reserve provided essential breeding habitats for shorebirds,such as Kentish plovers.However,a large-scale wetland restoration project of"Fishponds restoration"was carried out within the nature reserve,creating a large area of bare flat habitat in the coastal zone in 2019.The impact of this wetland restoration on the spatial distribution,nest selection,and corresponding fitness（such as egg camouflage）of local ground-nesting birds needs to study.This study carried out the reproductive monitoring of shorebirds in the wetland restoration and surrounding area of Liaohekou Reserve from 2018 to 2021.The spatial distribution,habitats utilization,and egg camouflage of breeding birds were compared by recording the distribution of breeding nests,habitat types,nest material composition,and egg camouflage before and after wetland restoration and combined with the spatial analysis of habitat changes during the restoration.The total wetland restoration area was 5075.9 ha in the nature reserve from 2019to 2020.During wetland restoration,the area of bare flats,the primary breeding habitat of shorebirds,increased from 406.62 ha to 3005.01 ha.In turn,the area of Building facilities decreased from 2881.53ha to 121.59 ha.Furthermore,the fragmentation degree of bare flats decreased,such as the patch density of bare flat decreased from 8.08/100ha to 5.97/100ha.Four species of shorebirds nested in the nature reserve,with the number of nests of Kentish plovers（Charadrius alexandrines）,Little terns（Sterna albifrons）Pied avocet（Recurvirostra avosetta）,and Eurasian oystercatcher（Haematopus ostralegus）are 303,193,68 and 14,respectively.Wetland restoration led to 74%（n=172）of birds nesting in the restored bare flat habitat,which significantly lower the aggregation degree of shorebird nests regionally with the nearest neighbor distance of Kentish plover and Little terns increased,and the aggregation index decreased significantly.However,Pied avocet and Eurasian oystercatcher’s closest neighbor distance and aggregation index did not change significantly.The effect of wetland restoration on nesting habitat use of different birds was inconsistent.Kentish plovers’use of bare flat habitats increased significantly from 64%（n=188）to 70%（n=92）during wetland restoration.However,wetland restoration had no effect on nesting habitat selection for Little terns because all of them nested in bare flat habitats（n=188）.Wetland restoration has a significant impact on nest material selection for Kentish plovers（?~2=19.86,df=3,P<0.01）with the proportion of rocks increased and the proportion of grasses and mud decreased.Furthermore,the wetland restoration also significantly affected nest material selection for Little terns（?~2=12.77,df=3,P<0.01）,with the proportion of grasses and rocks increased and the proportion of shells decreased.By analyzing the picture characteristics of microhabitats such as bird eggs and nest materials,we found the pattern energy difference between eggs and background of Kentish plovers and Little terns did not change significantly during the wetland restoration.This result suggested that the wetland restoration did not increase the egg camouflage of these two main breeding shorebirds（Kentish plovers and Little terns）.In conclusion,we believe that the project of"Fishponds restoration"dramatically influences the habitat selection,nest material exploitation,and spatial distribution of breeding shorebirds.The bare flat is the preferred habitat for many shorebirds to nest after wetland restoration.It increases the density of birds in the restoration area,promoting the decrease of the nest clusters for the spatial distribution of birds.On the one hand,the change in spatial distribution reflects the increase in habitat availability,which is beneficial to the reproduction of shorebirds.Still,the decline in nest density on the reproductive success rate of shorebirds that tend to breed in clusters and benefit from aggregative nest defense needs to be further explored.In addition,wetland restoration also impacts the use of nest materials of shorebirds.Still,it does not improve the camouflage of nests primarily because of the common use of well nest camouflage in these two birds.Finally,our study confirmed the wetland restoration of"Returning ponds to beaches"is greatly helpful for the nesting of most shorebird species（e.g.,Kentish plovers）,which will benefit the population conservation of breeding shorebirds. |
