Diet composition of the Marsh Owl Asio capensis at the Merja Zerga coastal lagoon, northwestern Morocco

Abstract

The diet of the Marsh Owl Asio capensis (family Strigidae) was examined at Merja Zerga coastal lagoon and wetland on the Gharb Plain, northwestern Morocco. The analysis was carried out on several small batches of regurgitated pellets, collected in January to July 2023, totalling 110 pellets which contained a total of 411 prey items. We identified 20 prey species belonging to 10 families and representing four classes. By number of prey items, mammals comprised 50.1% (representing 6 species) of the consumed prey, insects 45.3% (8 species) and birds 3.2% (4 species); amphibians were represented by a single species (Saharan frog Pelophylax saharicus). The Algerian mouse Mus spretus was the most frequently consumed prey species (26.3% of prey items), followed by the taurus scarab Onthophagus taurus (24.3%) and the North African gerbil Gerbillus campestris (15.6%). As percentage biomass in the pellets, rodents were by far the most important component in the Marsh Owl diet at 92.1%, with three species dominating: North African gerbil (31.9%), black rat Rattus rattus (30.2%) and Algerian mouse (24.4%); the house mouse Mus musculus contributed only 5.6% of prey biomass. The opportunistic nature of the foraging strategy of the Marsh Owl was evidenced by its consumption of large numbers of low-energy prey types.