The presence of introduced Norway rats Rattus norvegicus has raised concerns for the fate of the large least auklet Aethia pusilla colony situated at Sirius Point, Kiska Island, Alaska. Previous studies have documented extreme interannual variation in least auklet reproductive success and potential drastic population declines, both of which have been attributed to the varying abundance of, and predation by, Norway rats. A diet study would resolve the uncertainty that remains about the role of rats in the auklet's reproductive failure and the colony's decline. Our main objectives here were to quantify the variation in diet of introduced Norway rats and assess predation on least auklets. Using stable isotope analysis we document wide variability in rat diet dependent on location and provide direct evidence that Norway rats are preferentially preying on least auklets at Sirius Point. In conclusion, we hypothesize that the observed wide variability in rat diet will contribute to the persistence of rats on Kiska long after auklets have been extirpated. The persistence of rats enabled by their foraging plasticity will increase their effects by creating ecological traps within which prospecting individuals will fall and be depredated. This has large conservation consequences as it suggests that when seabirds are extirpated recolonization by prospecting birds is virtually impossible and island ecosystems will continue to be negatively affected and altered as long as introduced predators, such as rats, remain within them.
Large-scale oceanographic processes are the main drivers of seabird breeding success, but small-scale processes, though not as well understood, can also be important. We compared the success of Tufted Puffins (Fratercula cirrhata) breeding at two subcolonies only 1.5 km apart on Triangle Island, British Columbia, Canada, 2002–2005. In addition, we used stable-isotope analysis to test the hypothesis that parental foraging strategies differed between the two subcolonies, potentially underlying the variation in breeding success. Success was concordant across years at the two sites but, overall, Tufted Puffins bred more successfully at Strata Rock than at Puffin Rock. They raised chicks in all four years at Strata Rock, but in only three years at Puffin Rock; in two of those three years, Strata Rock chicks were, on average, 60 g and 100 g heavier than Puffin Rock chicks just before fledging. Discriminant analysis of carbon and nitrogen stable-isotope ratios in egg yolk and chick blood in 2004 and 2005 indicated that parental foraging differed between the two subcolonies, with both spatial (δ13C) and trophic-level (δ15N) differences involved. Thus, our study demonstrates the existence of foraging asymmetries in a pelagic seabird at a small spatial scale (between subcolonies), complementing patterns found at larger scales (between colonies). Moreover, the foraging asymmetries were associated with inequalities in fitness measures. We conclude that small-scale processes—in this case, systematic differences in the foraging ecology of local groups—can interact with large-scale oceanographic processes to determine seabird breeding success.
Variation sous-coloniale du succès de reproduction de Fratercula cirrhata: Association avec l'écologie de la quête alimentaire et implications
Little is known about the Northern Naked-tailed Armadillo, Cabassous centralis (Miller, 1899). Here we present a new record of C. centralis in the Maya Mountain Massif of Belize, from camera-trap surveys covering an area of 200 km2 conducted yearly between 2002 and 2017 in lowland tropical broadleaf evergreen forest, and a dead specimen found adjacent to a highway. The record presented constitutes a range expansion of ca 65 km for C. centralis in Belize. This adds valuable data about a species for which the geographic distribution is poorly known.
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