DOI: 10.5061/dryad.6wwpzgn39
title: Data for: Mammalian predators and vegetated nesting habitat drive reduced protected area nesting success of Kentish plovers, Yellow Sea region, China

description: Protected areas provide essential habitats for wildlife by conserving
 natural and semi-natural habitats and reducing human disturbance. However,
 whether breeding birds vulnerable to nest predation can benefit from
 strict land management in the protected area is unclear. Here, we compare
 the nesting performance of two groups of a ground-nesting shorebird, the
 Kentish plover (Charadrius alexandrinus), in the protected area (Liaohekou
 Natural Reserve, hereinafter PA) and the control non-protected area
 (Non-PA) around the Liaohekou Natural Reserve, in the north of the Yellow
 Sea, China, and identify which environmental factors, such as nesting
 habitat and nest materials, influence the daily nest survival rate (DSR).
 We found similar nesting habitats in both study areas, dominated by bare
 land or Suaeda salsa grassland. However, DSR was lower
 in PA (0.91 ± 0.01) than in Non-PA (0.97 ± 0.01). Kentish plovers nesting
 in areas with vegetation cover experienced lower DSR than in bare lands in
 both areas, and nests built with materials of S.
 salsa sticks had the lowest DSR in the bare land. Data from
 infrared cameras confirmed relatively higher predator abundances and nest
 predation rates by nocturnal mammals, such as Eurasian badgers (Meles
 meles), in PA than in Non-PA, and this pattern was especially evident for
 plover nests located in S. salsa grassland. Our results
 suggest that Liaohekou Natural Reserve protected area may not necessarily
 provide safe nesting sites for Kentish plovers due to the abundance of
 generalist mammal nest predators. However, the PA includes about
 80% of the nests from both locations. This means the contribution of the
 total number of successful nests continues to be much higher within PA,
 with the benefit for the species that this brings in terms of
 conservation. The variation and mechanisms underlying differences
 in the nest predator communities of PA and non-PA deserve further study.
description: All the selected breeding
 habitats of Kentish plover were systematically searched for nests between
 May and July each year. When nests with at least one egg were found, a
 Handheld GPS (Garmin 62) was used to record its location. Each nest was
 photographed using a digital camera (Nikon J5) to record the nesting
 environment and the composition of nest materials. Eggs were floated to
 estimate the incubation stage following the technique by Hays &
 Lecroy (1971). Nests were inspected 1-2 times per week during the early
 incubation stage (&lt; 22 days after egg-laying) and at 1–2 days
 intervals after 22 days of incubation (26 days) (Que et al., 2015). We
 limited the time observers spent in proximity to each nest to no more than
 5 mins to minimize potential disturbances and the chances of nest
 abandonment. Nest fate was categorized as follows: (A) Failure: nests were
 considered to have failed when (1) eggs were observed being collected or
 destroyed by humans; (2) nests were considered predated when there was
 evidence of predation e.g., camera images, yolks, egg content remaining
 in/around the nests; (3) were washed away by water or buried by mud due to
 flooding events and bad weather; (4) were abandoned (i.e., nests in which
 eggs were still present but were cold for two nest-checking periods. (B)
 Success: nest fate was considered to be successful when: (1) at least one
 nestling left the nest, (2) all eggs disappeared within two days of the
 estimated date of hatching, and did not meet any of the four criteria for
 ‘failure as mentioned above. (C) Unknown: nest fate was considered unknown
 when: the above-mentioned failure and success judgment criteria could not
 determine the fate of the nests. Nests with unknown fate (4.2%, n = 12)
 were not included in the subsequent statistical analyses ( e.g., nest
 success rate). Nesting habitats were recorded as either
 vegetated or bare land (Fig. 2A, B). All the nests with at least 50%
 vegetation coverage within a 30 cm radius were classified as vegetated
 habitats. The vegetation covering the nests was mostly S. salsa (85.4%, n
 =82), while short reed (Phragmites australis) represented the other 14.6%
 (n = 14). We estimated nest concealment by assessing visual obstruction by
 vegetation in five directions (up, N, E, S, and W) (Zero (0) = no
 vegetation cover in all directions, 5 = shielded in all directions)
 following Burhans & Thompson (2001). Most plover nests were
 dominated by one particular suite of substrates shells, stones or plant
 materials (the latter of which mainly consisted of dead S. salsa stems. We
 categorized the nests from the digital photographs using these criteria.
 Nests classified as “others” were mainly composed of mud (Fig. 2C, D, E
 & F). In addition, for each nest we also recorded the closest
 distance to the nearest road, water edge, mudflat, coastline, and PA
 boundary, which were estimated from updated high-resolution satellite
 images (http://www.sasclouds.com) using Arc GIS (v 10.2). Due to the fact
 that some plover nests were located outside the PA, we used the negative
 value to represent the relative distance to the PA
 boundary.  The distance matrix between each nest was
 calculated using R package “geosphere”(version 1.5-14). The nearest neighborhood
 distance was defined as the shortest distance between conspecific nests
 during the active period. In addition, an annual aggregation index for
 each nest relative to the spatial distribution of all Kentish plover nests
 was calculated using the formula Σ exp (−dij) (with i ≠ j), where dij was
 the linear distance between nest i and j (Hernández-Brito et al.
 2020).
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