New Nesting Records and Breeding Ecology Observations of Rufous-legged Owls in the Mediterranean Temperate Forest of Central Chile

ABSTRACT The Rufous-legged Owl (Strix rufipes) is the southernmost Strix owl species and its breeding ecology remains little known. We report new observations on the species' breeding ecology, including clutch size, egg size, duration of the incubation and nestling periods, and nestling diet. We conducted our observations on nests found during the summers of 1999 through 2004 in a forestry landscape of central Chile, dominated by Monterey pine (Pinus radiata) plantations with intermixed fragments of native southern beech (Nothofagus) forests. Clutch size was two eggs (n = 2 nests), with one egg larger than the other (mean = 48.8 × 40.1 mm). The incubation period was 30 d and the nestling period 34 d. We analyzed 10 pellets from nestling owls and identified 45 prey items, mostly dominated by large beetles, grasshoppers, and rodents (native and exotic). This information, though based on a limited number of nests, provides baseline ecological data that can inform future studies.

Does Habitat Diversity Modify the Dietary and Reproductive Response to Prey Fluctuations in a Generalist Raptor Predator, the Eurasian Buzzard Buteo buteo?

Predators can modify their diet and demography in response to changes in food availability and habitat quality. I tested the prediction that some species can change their predation pattern, between specialist type and generalist type, depending on the complexity of habitat structure. It was hypothesized that their dietary response is stronger in diversified habitats than in simplified ones, but the opposite tendency occurs in the case of reproductive response. The nestling diet and breeding success of the Eurasian Buzzard Buteo buteo, the abundance of its main prey (the common vole Microtus arvalis), and that of the most important alternative prey group (passerines) were estimated over ten years in two types of agricultural habitat in western Poland, i.e., in the diversified habitat of small fields and the simplified habitat of large fields. The vole abundance was higher in large fields, but the abundance of passerines was greater in small fields. The frequency of voles in the Eurasian Buzzard nestling diet was higher in large fields than in small fields and increased with the abundance of this prey in crop fields. However, no difference in the relationship between the vole frequency in the diet of Eurasian Buzzards and the abundance of voles was found between the two habitat types. The breeding success of Eurasian Buzzards was dependent on the vole abundance, but this relationship did not differ between the two field types. It seems that the pattern of dietary and reproductive response of Eurasian Buzzards depends on the actual availability of individual prey species, which can be modified by habitat quality, rather than on relative prey abundance.

Trophic links of the song thrush (Turdus philomelos) in transformed forest ecosystems of North-Eastern Ukraine

The diet spectrum of the song thrush (Turdus philomelos Brehm, 1831; Passeriformes, Turdidae) was studied with the aim of supporting the population of the species in transformed forests of North-Eastern Ukraine. Four forest ecosystems were surveyed: three model sites in oak woodlands with different stages of recreational digression, and the fourth model site in a pine-oak forest. A total of 45 invertebrate taxa with the dominance of Insecta (64.6%, n = 1321), Oligochaеta (16.7%), and Gastropoda (12.0%) were revealed in the diet of the song thrush. At the level of orders, Lepidoptera (66.2%) was dominant. In the qualitative structure of the song thrush nestling diet, the highest number of taxa (40.5–59.1%) was represented by phytophages. Phytophagous species also comprised the majority of the consumed prey items (44.7–80.3%). Environmental conditions are an important factor, affecting the diet composition of birds. The most favourable foraging conditions for the thrushes were revealed in natural protected areas. The analysis has shown a fairly even foraging efficiency of the thrushes in all the studied sites. The highest biodiversity indices were found in a protected area of the National Nature Park “Homilshanski Forests”. The results of the research indicate an important role of T. philomelos in the population management of potentially dangerous agricultural pests.

Influence of agricultural intensification on prey availability and nestling diet in Tree Swallows (Tachycineta bicolor)

Over the last decades, aerial insectivorous birds have been declining in both North America and Europe. Those declines have been hypothetically attributed to a decrease in prey availability caused by agricultural intensification, but empirical evidence remains scarce. Here, we quantify the effect of landscape composition on the abundance and diversity of potential prey of Tree Swallows (Tachycineta bicolor (Vieillot, 1808)) and on nestling diet in southern Quebec, Canada. We collected food boluses from nestlings and compared their composition with spatiotemporally corresponding samples from traps on farms distributed along a gradient of agricultural intensification. The diet of nestlings was mostly composed of Diptera, both in biomass and abundance, but by mid-June, these decreased with increasing proportions of intensively cultivated crops within 500 m of the nests. Trap catches for Diptera and all arthropods combined followed the same trends. Yet, the associations between Diptera subgroups (Nematocera, non-schizophoran Brachycera, Schizophora (Calyptratae), and Schizophora (Acalyptratae)) and landscape composition differed between traps and boluses, suggesting that prey selection was altered by agricultural intensification. Our results suggest that agriculture can alter the availability of preferred prey for aerial insectivores, and further studies should evaluate the impact of prey availability to explain the decline of aerial insectivores.

Stream acidification and reduced aquatic prey availability are associated with dietary shifts in an obligate riparian Neotropical migratory songbird

Streams and their surrounding riparian habitats are linked by reciprocal exchanges of insect prey essential to both aquatic and terrestrial consumers. Aquatic insects comprise a large proportion of total prey in riparian habitats and are opportunistically exploited by terrestrial insectivores; however, several species of songbirds are known to preferentially target aquatic prey via specialized foraging strategies. For these songbirds, reduced availability of aquatic insects via stream acidification may result in compensatory changes in provisioning during the nesting period, thereby influencing both adult and nestling diet composition. In this study, we used DNA metabarcoding to test the hypothesis that an obligate riparian Neotropical migratory songbird, the Louisiana Waterthrush (Parkesia motacilla), expands its diet to compensate for the loss of preferred aquatic prey taxa (primarily pollution-sensitive Ephemeroptera, Plecoptera, and Trichoptera) as a result of stream acidification. Our results revealed that both adult and nestling waterthrush exhibited an increase in dietary richness and niche breadth resulting from the consumption of terrestrial prey taxa in acidified riparian habitats. In contrast, compensatory dietary shifts were not observed in syntopic Neotropical migrant species known to primarily provision terrestrial prey taxa. In addition to providing support for our hypothesis that waterthrush compensate for stream acidification and aquatic prey limitations by expanding their diet, our findings highlight the vulnerability of Louisiana Waterthrush to anthropogenic disturbances that compromise stream quality or reduce the availability of pollution-sensitive aquatic insects.

First information concerning nestling diet in the Bare-necked Fruitcrow Gymnoderus foetidus

Despite being widespread throughout most of the Amazon, the Bare-necked Fruitcrow Gymnoderus foetidus is poorly known and nestling diet is undocumented. I report herein the first observations on the nestling diet in this cotinga.A pesar de tener una amplia distribución en la mayor parte de la Amazonía, el Cuervo Higuero Cuellopelado Gymnoderus foetidus es poco conocido y la dieta de los polluelos no se ha documentado. En esta nota reporto las primeras observaciones sobre la dieta de pichones de esta cotinga.