Nest survival of the Two-Banded Plover (Charadrius falklandicus) population in Northern Chubut Province, Patagonia Argentina

D'AMICO, V.; SANDERCOCK, B.; HEVIA, G.; GALINDO-ESPINOSA, D.; BERTELLOTTI, M.

Washington

Conferencia; North American Ornithological Conference; 2016

The Two-Banded Plover (Charadrius falklandicus) is an endemic shorebird to southern South America including the Falkland Islands. Their global population is estimated between 46,000-140,000 individuals. Although the Two-Banded Plover conservation status is listed as Least Concern by the IUCN, population trends, demography and migratory patterns are poorly known. Current efforts to monitoring Two-Banded Plover at northern Chubut Province, Patagonia, Argentina, have provided information on their breeding biology at two beaches with different levels of human disturbance. In this study, we hypothesized that Two-Banded Plover nest survival will vary between sites due to differences in human disturbance. Our objectives were to: 1) estimate annual nest survival, 2) describe causes of nest failure. The study site was located at two beaches in Puerto Madryn, Argentina (42°S, 65°W). Parana beach have high levels of human disturbance from recreational activities? circulation of all-terrain vehicles and cars, pedestrians with dogs, bike riders, and fishermen ?, while Las Canteras have low levels of disturbance as only pedestrians use this beach. Fieldwork was carried out between early October and late December 2012. Surveys were conducted by foot using the nearest road track, along one to six kilometers length transects depending on beach size. We located nests by observing parental behavior (i.e., listening their alarm vocalizations or watching them flush from the nest). We recorded spatial coordinates of each nest with a handheld GPS unit. We also recorded spatial position for each nest using three habitat variables distance to the high tide line, distance to the road track, and distance to the nearest con-specific nest. We floated eggs to estimate hatching dates, and nests were monitored three to five days per week to verify success (at least one egg hatched) or failure. Causes of nest failure were: 1) human impact, 2) flooding, 3) abandoned, 4) predation, and 5) unknown. We build encounter histories for nest survival and analyze competing models with RMark package in R. We standardized the earliest date a nest was found, 2 October, as day one of the nesting season for both sites, and estimated the DSR (Daily Survival Rate) from the beginning of incubation. We found a total of 45 nests during 2012, throughout an 89-day nesting season from 2 October to 29 December ?last day a nest was found active?. We used valid encounter histories for 41 nests (22 at Las Canteras and 19 at Parana) as four nests had an unknown fate. The most common cause of nest failure at Parana beach was human impact, where all-terrain vehicles trampled eggs (80%, n=7), followed by predation (20%, n=2). By contrast, at Las Canteras the most common cause was flooding by extraordinary high tides (50%, n=3), followed by parental abandonment (33%, n=2) and human impact (17%, n=1). The DSR was highest in Las Canteras (0.983; 95% CI = 0.963 ? 0.992; n = 22), than in Parana beach (0.966; 95% CI = 0.937 ? 0.982; n = 19). Since this two beaches are important for the locally Two-Banded Plover breeding population, the implementation of management actions (for instance, symbolic fencing) to protect breeders and their nests from harmful levels of human disturbance, are urgently need it.