Kentish plover capture histories

Global biodiversity loss is a major environmental concern. The wildlife on islands are particularly vulnerable to threats posed by alien predators, habitat loss and overexploitation. Effective conservation management of vulnerable species requires reliable information on vital population rates for all life stages and an understanding of key environmental drivers. However, demographic data are often not available for island populations before they decline or are extirpated. Here, we use Cormack-Jolly-Seber (CJS) models and 15 years of data for 1370 juveniles and 687 adults to estimate apparent survival for a genetically distinct resident population of Kentish plovers (Charadrius alexandrinus) on the island of Maio, Cabo Verde. We report two main findings. First, environmental conditions have a large effect on demographic performance since chicks that hatch during dry years experience a tenfold reduction in first-year survival compared to chicks that hatch during wet years. Second, female and male plovers in Maio are expected to live for 7.41 ± 0.69 (mean ± SE) years and 6.75 ± 0.64 years, respectively, due to relatively high annual survival among comparable-sized shorebirds. High adult survival thus could buffer the population against low reproductive success that this population has experienced over the last decade. Cabo Verde is typical of tropical islands with increased development that can impact native breeders and/or will accelerate habitat loss. Thus, more frequent droughts associated with climate change may exacerbate the prospects of native wildlife on many islands.

Methods
Data collection
Data collection followed a standard protocol developed to monitor the breeding ecology of plovers (Székely et al. 2008). When a Kentish plover nest was first found, the attending parents were captured at the nest with a funnel trap, and each bird was marked with a unique metal-colour ring combination. To minimise the risk of some breeders abandoning the nest upon capture, we only captured individuals on nests that had been incubated for at least 5 days. At some nests where the parents of the nest were already ringed, the metal-colour ring combination was read with binoculars or a spotting scope. The sex of adults was visually determined by sexual differences in plumage where females are drab brown, and males have black streaks on their forehead, eye stripe and around their neck. Chicks were ringed with one metal ring either at the nest at hatching or if encountered as a mobile juvenile after departing the nest. If juveniles survived and were recaptured as adults at a nest in a later year, they were marked with a full combination of colour-rings.