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International audience; The density and distribution of Westland Petrel burrows was assessed over a 12-year period (2007–2019). During that time, burrow densityincreased while occupancy remained stable, commensurate with an annual population growth rate of 1.022 (95% confidence interval:0.971–1.076), as estimated using mark recapture data. From our surveys, we estimated a 2019 baseline population of ~6 200 breeding pairsand a world population of 13 800–17 600 individuals, covering around 95% of the population. Transects were conducted to establish thelocation and density of 17 petrel sub-colonies in rugged, untracked terrain in Paparoa National Park, West Coast, New Zealand. Major stormsin 2014–2018 caused widespread treefall and landslides, destroying breeding habitat throughout the species’ breeding range. Demographiceffects of the major and ongoing habitat loss may continue in the medium to long term, as birds re-establish burrows and partnershipsfollowing loss of their habitat. Our study illustrates the complex effects of climate-related disruption on the biology of a long-lived species.With a single nesting area in the West Coast region, climate change will likely have an ongoing influence on the species’ global population,since an increase in the frequency of severe weather events, including ex-tropical cyclones, is expected. However, current indications suggestthat the species has some flexibility to adapt and to occupy new areas following habitat disturbance.

Despite international waters covering over 60% of the world's oceans, our understanding of how fisheries in these regions shape ecosystem processes is surprisingly poor. Seabirds are known to forage at fishing vessels, with potential deleterious effects for their population, but the extent of overlap and behavior in relation to ships are poorly known. Using novel biologging devices, which can detect radar emissions to record the position of boats and seabirds, we measured the true extent of the overlap between seabirds and fishing vessels, and generated estimates of the intensity of fishing and distribution of vessels in international waters. During breeding, wandering albatrosses from the Crozet islands patrolled an area of more than 10 million square kilometers and as much as 79.5% of birds equipped with loggers detected vessels, at distances up to 2500 km from the colony, modifying their natural foraging behavior to attend boats. The extent of this overlap has widespread implications for bycatch risk in seabirds and reveals the areas of intense fishing throughout the ocean. We suggest that seabirds equipped with radar detectors are excellent monitors of the presence of vessels in the southern ocean, offering a new way to monitor fisheries. The method used opens new perspectives to monitor the presence of illegal fisheries and to better understand the impact of fisheries on seabirds. This article is protected by copyright. All rights reserved.