In recent years, more than 130 extinctions have been estimated to have occurred in the marine realm. Here we review this body of evidence and show that this figure may actually be overestimated by as much as 50%. We argue that previous estimates have not fully taken into account critical uncertainties such as naturally variable geographical distributions, and have misinterpreted documentary evidence. However, current evidence indicates that some sharks, rays and reef‐associated species, although not necessarily geographically restricted, are particularly vulnerable to anthropogenic impacts and now occur in very low numbers. Overestimating extinctions is of concern because it could reduce confidence in the credibility of the ‘extinct’ category in threatened species lists and, ultimately, be used to question the integrity of conservation and management policies. We suggest that when integrating future checklists of marine extinct species, there needs to be a more rigorous use of the terminology of extinction, and participation by specialists in each of the particular taxonomic groups involved.

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Estimating the population of burrow-nesting seabirds is a challenging task, as human presence in the colony creates disturbances and can damage burrows and occupants. Here, we present a novel method using aerial photographs taken with Unmanned Aerial Vehicles (UAVs) to estimate the population size of a burrow-nesting seabird, the Black-vented Shearwater (Puffinus opisthomelas), on Natividad Island, Mexico. Our results provide a census of burrows in the colony, with very low detection error (5.6%). This is greater accuracy compared to other methods based on extrapolating results from sample plots to total colony area. We then combined this burrow census with ground truth data on occupancy to estimate population size. We obtained a population estimate of 37,858 and 46,322 breeding pairs for 2016 and 2017 respectively. The proposed method provides a cost effective and repeatable approach for monitoring numbers of burrows occupied in a colony, thereby enabling easier and faster estimates of population trends. We suggest this method can be valid for other burrow-nesting species in habitats without dense vegetation cover.

de 2006 a febrero de 2007; se identificaron 40 especies, 3 de las cuales corresponden a nuevos registros. El área fue utilizada por, al menos, 25 000 aves acuáticas; 5 fueron las especies dominantes: 3 anátidos (Anas clypeata, A. platyrhynchos diazi y Oxyura jamaicensis), 1 ave playera (Limnodromus scolopaceus) y 1 gallareta (Fulica americana). Sobresalió por su abundancia A. platyrhynchos diazi, subespecie endémica y amenazada, ya que los 2 200 individuos observados representan el 4% de la población total estimada. Las especies mejor representadas mostraron una utilización espacial diferencial, con 3 patrones: 1) especies con distribución uniforme (A. clypeata y F. americana), 2) las agrupadas en una sola porción del humedal (A.p. diazi y O. jamaicensis) y 3) aquella con afinidad por 2 porciones del humedal (L. scolopaceus). La ciénega de Tláhuac es un humedal importante para la avifauna de la región; en ella ocurren, durante el invierno, 6 especies protegidas por el gobierno mexicano; sin embargo, existen factores antrópicos que ponen en riesgo su integridad y que hacen necesarias acciones de protección y conservación.Palabras clave: anátidos, aves playeras, gallaretas, humedales interiores, lago de Tláhuac.

Understanding the population dynamics of migratory animals and predicting the consequences of environmental change requires knowing how populations are spatially connected between different periods of the annual cycle. We used stable isotopes to examine patterns of migratory connectivity across the range of the western sandpiper Calidris mauri. First, we developed a winter isotope basemap from stable‐hydrogen (δD), ‐carbon (δ13C), and ‐nitrogen (δ15N) isotopes of feathers grown in wintering areas. δD and δ15N values from wintering individuals varied with the latitude and longitude of capture location, while δ13C varied with longitude only. We then tested the ability of the basemap to assign known‐origin individuals. Sixty percent of wintering individuals were correctly assigned to their region of origin out of seven possible regions. Finally, we estimated the winter origins of breeding and migrant individuals and compared the resulting empirical distribution against the distribution that would be expected based on patterns of winter relative abundance. For breeding birds, the distribution of winter origins differed from expected only among males in the Yukon‐Kuskokwim (Y‐K) Delta and Nome, Alaska. Males in the Y‐K Delta originated overwhelmingly from western Mexico, while in Nome, there were fewer males from western North America and more from the Baja Peninsula than expected. An unexpectedly high proportion of migrants captured at a stopover site in the interior United States originated from eastern and southern wintering areas, while none originated from western North America. In general, we document substantial mixing between the breeding and wintering populations of both sexes, which will buffer the global population of western sandpipers from the effects of local habitat loss on both breeding and wintering grounds.