What determines prey selection in owls? Roles of prey traits, prey class, environmental variables, and taxonomic specialization

Abstract

Ecological theory suggests that prey size should increase with predator size, but this trend may be masked by other factors affecting prey selection, such as environmental constraints or specific prey preferences of predator species. Owls are an ideal case study for exploring how predator body size affects prey selection in the presence of other factors due to the ease of analyzing their diets from owl pellets and their widespread distributions, allowing interspecific comparisons between variable habitats. Here, we analyze various dimensions of prey resource selection among owls, including prey size, taxonomy (i.e., whether or not particular taxa are favored regardless of their size), and prey traits (movement type, social structure, activity pattern, and diet). We collected pellets of five sympatric owl species (Athene noctua, Tyto alba, Asio otus, Strix aluco, and Bubo bubo) from 78 sites across the Mediterranean Levant. Prey intake was compared between sites, with various environmental variables and owl species as predictors of abundance. Despite significant environmental impacts on prey intake, some key patterns emerge among owl species studied. Owls select prey by predator body size: Larger owls tend to feed on wider ranges of prey sizes, leading to higher means. In addition, guild members show both specialization and generalism in terms of prey taxa, sometimes in contrast with the expectations of the predator–prey body size hypothesis. Our results suggest that while predator body size is an important factor in prey selection, taxon specialization by predator species also has considerable impact.

The Effect of Oxygen Limitation on a Xylophagous Insect’s Heat Tolerance Is Influenced by Life-Stage Through Variation in Aerobic Scope and Respiratory Anatomy

“…For analyzing the scaling relationships between the traits, we used the general equation Y = aM b where Y is the air volume, a is a scaling coefficient, M is the body mass, and b is the scaling value (Huxley, 1932; LaBarbera, 1989). The slopes, i.e., b , were derived by using ordinary least squares regression estimates and then compared to the commonly used theoretical scaling values 1, 0.67, and 0.75 (Chown et al, 2007).…”

“…The slopes, i.e., b , were derived by using ordinary least squares regression estimates and then compared to the commonly used theoretical scaling values 1, 0.67, and 0.75 (Chown et al, 2007). When comparing air volume to mass, the value 1 reflects isometry and is often used as a null hypothesis in anatomy scaling studies (LaBarbera, 1989). The value 0.67 is also isometry that reflects surface area to volume geometry (Kozłowski et al, 2003).…”

Digital media and the modern-day pet trade: a test of the ‘Harry Potter effect’ and the owl trade in Thailand

“…These previous results are consistent with our findings. Owl species are top predators that play a key role in the ecosystems where they are found (Comay & Dayan 2018). Owl species with ranges in Thailand are also protected from trade under Thai wildlife laws; the continuing online trade, however reflects a lack of law enforcement or monitoring within the easily accessible virtual markets (Siriwat & Nijman 2018).…”

The biogeography of diet diversity of barn owls on Mediterranean islands

“…Prey selection on islands is limited by the presence of potential prey species and varies between individual islands. Although numerous factors can influence prey selection in owls (Comay & Dayan, 2018;Romano et al, 2020), we hypothesize that on islands the island's size, distance from the mainland and, as a proxy for urbanization, human population density also affect the pattern of the barn owl's prey composition. In this study, we present primary data on the diet of the barn owl on the Adriatic island of Korčula (Croatia) and include these results in a meta-analysis of available data on the barn owl diet across Mediterranean islands.…”