PELLETS AND PREY REMAINS AS INDICATORS OF THE DIET OF TWO SYMPATRIC SKUAS (AVES: STERCORARIIDAE) ON KING GEORGE ISLAND, ANTARCTICA

South Polar skua (Stercorarius maccormicki) and Brown skua (Stercorarius antarcticus lonnbergi) have opportunistic feeding habits and are the dominant predators in terrestrial Polar regions. These skuas exploit a wide range of food items, including marine organisms, other birds, and even garbage. In the present study, we compare the diets of these two skua species during the breeding season, using pellets and prey remains collected within their territories. The samples were collected at six sites in Admiralty Bay, on King George Island, Antarctica. We identified eight different items, which we classified as “penguin”, “flying bird”, “skua”, “fish”, “gastropod”, “krill”, “egg” and “marine debris”. In the first breeding season (2008/2009), penguins and flying birds were the food resources more abundant for both skua species, and their diet composition was similar. In the second breeding season (2010/2011) South Polar skua exploited more fish and flying birds than Brown skua; the latter exploited more eggs and penguins. Our findings corroborate those of previous studies, demonstrating that in sympatry South Polar skua exploit more fish than Brown skua. The diet of South Polar skua also varied between breeding seasons, reflecting the opportunistic foraging behavior of these skuas. As in other studies, we recorded that skua is a food resource for both skua species, but it was more common in the diet of South Polar skua. Marine debris was recorded only in the samples of Brown skua. Birds are important food items for both skuas, although significant differences were found in the diets of these sympatric species, with shifts in the composition of the diet probably reflecting fluctuations in the abundance of prey populations, which are known to be common at Admiralty Bay, although more data will be needed to confirm this link.

An asynchronous Mesozoic marine revolution: the Cenozoic intensification of predation on echinoids

Predation traces found on fossilized prey remains can be used to quantify the evolutionary history of biotic interactions. Fossil mollusc shells bearing these types of traces provided key evidence for the rise of predation during the Mesozoic marine revolution (MMR), an event thought to have reorganized global marine ecosystems. However, predation pressure on prey groups other than molluscs has not been explored adequately. Consequently, the ubiquity, tempo and synchronicity of the MMR cannot be thoroughly assessed. Here, we expand the evolutionary record of biotic interactions by compiling and analysing a new comprehensively collected database on drilling predation in Meso-Cenozoic echinoids. Trends in drilling frequency reveal an Eocene rise in drilling predation that postdated echinoid infaunalization and the rise in mollusc-targeted drilling (an iconic MMR event) by approximately 100 Myr. The temporal lag between echinoid infaunalization and the rise in drilling frequencies suggests that the Eocene upsurge in predation did not elicit a coevolutionary or escalatory response. This is consistent with rarity of fossil samples that record high frequency of drilling predation and scarcity of fossil prey recording failed predation events. These results suggest that predation intensification associated with the MMR was asynchronous across marine invertebrate taxa and represented a long and complex process that consisted of multiple uncoordinated steps probably with variable coevolutionary responses.

Endangered predators and endangered prey: Seasonal diet of Southern Resident killer whales

Understanding diet is critical for conservation of endangered predators. Southern Resident killer whales (SRKW) (Orcinus orca) are an endangered population occurring primarily along the outer coast and inland waters of Washington and British Columbia. Insufficient prey has been identified as a factor limiting their recovery, so a clear understanding of their seasonal diet is a high conservation priority. Previous studies have shown that their summer diet in inland waters consists primarily of Chinook salmon (Oncorhynchus tshawytscha), despite that species’ rarity compared to some other salmonids. During other times of the year, when occurrence patterns include other portions of their range, their diet remains largely unknown. To address this data gap, we collected feces and prey remains from October to May 2004–2017 in both the Salish Sea and outer coast waters. Using visual and genetic species identification for prey remains and genetic approaches for fecal samples, we characterized the diet of the SRKWs in fall, winter, and spring. Chinook salmon were identified as an important prey item year-round, averaging ~50% of their diet in the fall, increasing to 70–80% in the mid-winter/early spring, and increasing to nearly 100% in the spring. Other salmon species and non-salmonid fishes, also made substantial dietary contributions. The relatively high species diversity in winter suggested a possible lack of Chinook salmon, probably due to seasonally lower densities, based on SRKW’s proclivity to selectively consume this species in other seasons. A wide diversity of Chinook salmon stocks were consumed, many of which are also at risk. Although outer coast Chinook samples included 14 stocks, four rivers systems accounted for over 90% of samples, predominantly the Columbia River. Increasing the abundance of Chinook salmon stocks that inhabit the whales’ winter range may be an effective conservation strategy for this population.

European Hamster at the edge: declining in nature and rare in owl pellets

Over the last decades, the European Hamster (Cricetus cricetus) has been declining in many parts of its European range. Due to the lack of recent information on the occurrence and status of the European Hamster in the south-western Carpathian Basin west of the Danube, we used information gathered from prey remains in Common Barn-owl (Tyto alba) pellets. In spite of considerable sampling effort, we retrieved only few hamster remnants. Two skulls were found in Podolje (Croatia) in 2007 and 2016, respectively. Further five hamsters were retrieved from pellets collected in 2017, 11 km to the northwest in Udvar (Hungary). In Sátorhely, 5 km north from Udvar, one roadkill male was found on 27.07.2019. Testimonies from local inhabitants confirmed the current presence of the European Hamster in the area. Our results suggest the presence of a small isolated population in the border area of Croatia (UTM 10 km grid square CR27) and Hungary (CR18, CR19). This small isolated population is on the south-western limit of the range of the species. We presume that the population requires conservation attention because of its isolated position at the edge of the species’ range, its small size and low abundance. We call for a transboundary action by nature conservation authorities in Croatia and Hungary.

Raptor Prey Remains

Are you curious about the remains of an animal you have found? This compilation of the most likely found body parts of animals eaten by raptors will help you identify your discovery. Including over 100 species of bird and mammal prey of raptors such as sparrowhawks, peregrines and hen harriers, this photographic guide highlights the common feathers, fur and other body parts found at raptor nests, roosts, plucking posts and other opportunistic spots. Discovering what raptors eat is an important part of confirming their feeding ecology and how this might change over time, vary on a local level or in response to changing prey populations, as well as dispelling myths and assumptions about what certain raptor species eat. Diet studies are vital for the conservation of raptor species; the more we know about what they need for survival the more we can predict and plan long-term for the protection and survival of raptors that may be vulnerable and in decline. This is the first book to show in detail the actual parts of a bird, mammal or other animal that you are likely to find in a garden, woodland or beneath a raptor roost. As more people take an interest in raptors and watch species such as peregrines via webcams and through watch groups, there is greater opportunity for finding prey remains. This book provides the first and most important step in identifying a prey species.

Friend or Foe? Orb-Weaver Spiders Inhabiting Ant–Acacias Capture Both Herbivorous Insects and Acacia Ant Alates

The orb-weaver spiders Eustala oblonga (Chickering) and Eustala illicita (O. Picard-Cambridge) (Araneae: Araneidae) inhabit the ant-defended acacias Vachellia melanocerus (Beurling) and Vachellia collinsii (Safford) (Fabales: Fabaceae), respectively, in Panama. These spiders do not capture patrolling Pseudomyrmex ants but exploit their plant-protection services to escape predation. What effect the spiders have on the ant-acacia mutualisms is unknown. They may provide an additional layer of plant defense by capturing flying herbivorous insects in their webs. Alternatively, the spiders may disrupt the ant–acacia mutualisms by capturing alate acacia ants during nuptial flights. We evaluated these two hypotheses by sampling insects flying through acacia foliage and by identifying prey remains in webs. The proportions of insects captured on sticky card traps and in webs varied with taxonomic order and ecological role. Herbivorous insects greatly outnumbered other groups captured on sticky cards and were captured in spiders’ webs in both acacia species but made up a minority of prey remains in webs. Instead, insect predators and parasitoids made up the majority of prey remains and were comprised primarily by alate ant mutualists of the host acacias. These results provide indirect support for both hypotheses and suggest that the spiders potentially both benefit and harm their host ant-acacia mutualisms. The net effect of spider exploitation, however, is unclear and is likely based on both the effectiveness of plant protection from herbivory provided by the spiders relative to that provided by acacia ants, as well as the overall proportion of the ant reproductive caste the spiders actually capture.

Diet of the Lesser Spotted Eagle (Clanga pomarina) in Amvrakikos Wetlands National Park, Greece

The diet of the lesser spotted eagle (Clanga pomarina) was studied in the area that is now the Amvrakikos Wetlands National Park during the Spring periods of 2000 and 2002 by analysis of pellets and prey remains found at two active nest sites, in two different territories. Among 155 prey items collected, in terms of biomass, the diet was 43% reptiles, 30% birds, 24% mammals, 3% amphibians and 1% arthropods. The most important prey taxa were brown rat (Rattus norvegicus) at 19%, water snakes (Natrix spp.) at 11% and moorhen (Gallinula chloropus) at 11% composition. Despite a wide availability of semi-natural and agricultural habitats around the immediate nesting areas, the species seems to have invested in foraging largely on water-dependent animals. The species maintained only one or a maximum of two pairs in the wider region during the study, this being at the southwestern margin of its global breeding range. Conservation insights and recommendations are presented.