Nesting Habitat and Nest Survival Data for American (Pluvialis dominica) and Pacific (P. fulva) Golden-Plovers on the Seward Peninsula, Alaska, 2012−2013

We systematically searched our study areas for nests from late May through late July by walking evenly spaced transects, approximately 20 m apart to ensure full overlap, and following adults exhibiting nesting behaviors back to their nests. Nest locations were recorded using handheld GPS units. We marked nests with small rock cairns located 2 m from the nest to enable the relocation of nests while avoiding the attraction of predators.

For each nest, we measured habitat characteristics within one quadrat (0.5 m × 0.5 m) centered on the nest site (to represent microhabitat at the nest) and a second quadrat at a paired point randomly selected from within a 350-m radius of the nest site (to represent habitat available in the territory, which is typically 10−50 ha in size). Within each quadrat, we estimated the percent cover and mean height of the following habitat components: alder (Alnus spp.), willow (>50 cm), dwarf willow (≤50 cm), dwarf birch, cinquefoil (Potentilla spp.), mountain-avens (Dryas spp.), ericaceous plants (Ericaceae), non-graminoid herbaceous plants, graminoids, moss, lichen, rock, and bare ground. We also estimated percent cover of water and detritus (i.e. leaf litter). We recorded cover using cover classes (0, 1–5, 6–25, 26–50, 51–75, 76–95, and 96–100%). We sampled habitat in late July and early August after nesting was completed to avoid disturbing nesting birds. Thus, measurements were more representative of mature seasonal growth of the vegetation than characteristics at the time of nest initiation or depredation, particularly for height of graminoid vegetation; however, measurements should index the relative height and cover of vegetation at selected vs. random sites given the directional increase in plant growth in this system (cf. Latif et al. 2012). Furthermore, relative comparisons should be minimally biased because of the highly synchronized breeding each season.

When we discovered a nest, we floated the eggs to estimate the incubation stage. We then monitored the nest every 4–7 days throughout incubation (24−29 days from laying of the last egg to hatching of the first until eggs were within 5 days of their earliest predicted hatch date, after which we visited them every 1–2 days until hatch occurred or the nest failed. We classified a nesting attempt as successful if at least one egg hatched or if pipped eggshell fragments were found in the nest cup. A nesting attempt was considered failed if (1) a depredation event was observed directly (only 2 of 45 depredation events); (2) eggs disappeared prior to the estimated hatch date and there was no sign of hatched eggshell parts or adults attending young (nest assumed lost to predation); or (3) eggs that had previously been incubated were found cold and abandoned in the nest cup with no sign of attending adults (nest abandoned).