CHELI german Horacio
Food habits of the Magellanic horned owl (Bubo virginianus magellanicus) at southernmost Patagonia, Argentina
FORMOSO, ANAHÍ; TETA, PABLO; CHELI GERMÁN
JOURNAL OF RAPTOR RESEARCH
RAPTOR RESEARCH FOUNDATION INC
Lugar: Lawrence, Kansas; Año: 2012 vol. 46 p. 401 - 401
The Magellanic Horned Owl (Bubo magellanicus) is the largest owl of the Strigidae family in South America and mainly feeds on small mammals, but birds and insects. The aim of this work was to characterize the diet of the Magellanic Horned Owl in austral Patagonia using food-niche breadth (normal and standardized) and geometric mean mass of prey, and to compare our findings with those made on North Patagonia.We identified 1637 prey items, of which 853 (52.1%) were small mammals, 760 (46.4%) arthropods, 23 (1.4%) birds and 1 (0.1%) reptile (table 2). Among the small mammals, the most eaten species by the owl were: Abrothrix olivacea (31%), Eligmodontia morgani (22.27%), and Reithrodon auritus (13.8%). The introduced species accounted for 8.3% (lagomorphs) and 0.6% (Mus musculus). We found that the Magellanic Horned Owl preyed principally on small mammals, being the Sigmodontinae Subfamily (Crietidae Family) the most represented (52.1%), followed by arthropods (46.4%) being the Carabidae family the most represented. This high consumption on arthropods can be considered as occasional events in the feeding habits of Bubo magellanicus, since only three of the nine studied localities had arthropods remains. Furthermore, the three samples containing arthropods were collected during breeding season, while we collected an additional sample which had not arthropods remains. This results support the issue that these occasional events could be associated with breeding, seasons and prey availability. The consumption of lagomorphs in our study was scarce, although the density of hares is elevated in Patagonia but still they were present in almost all localities. This could be due to the small size of Magellanic Horned Owl which causes that the cost of capturing an adult lagomorph is too high. The high predation on small mammals is similar to those results found in most works carried out in Patagonia. In contrast, the low predation on lagomorphs is opposite to other, facts that could be an occasional event or caused by merging information. The most consumed rodents are the most available preys in the open areas where Bubo magellanicus principally hunts which is consistent with the findings in other works and would explain the low or no predation on forest preys. The high predation on R. auritus and E. morgani was also observed in North Patagonia, but the high predation on A. olivacea disagrees with these studies, species that was present in all the analyzed samples and has a wide and dominant distribution in the study area. We found two morphs of Ctenomys sp.: a bigger one and a smaller one. The bigger one could be assigned to the Ctenomys magellanicus species and the smaller. According to our results, the Magellanic Horned Owl in Austral Patagonia feeds principally on small mammals and occasionally takes other available prey items (such as lagomorphs, birds and arthropods).