Trophic segregation of the Burrowing Owl and the American Kestrel in fragmented desert in Mexico

ABSTRACT

We analysed the diet of the Burrowing Owl (Athene cunicularia) and the American Kestrel (Falco sparverius) in a fragmented habitat and natural surroundings in the arid ecosystem of the Baja California peninsula, Mexico. Both small-sized raptors are considered in the same trophic guild, and as keystone species, interactions between them could be of interest for wildlife management in fragmented landscapes for agricultural activities. The diet analysis of these top predators could be a good monitor of prey abundance, some of which may be considered detrimental for agricultural activities. Prey frequencies in owl pellets were higher for arthropods (53.1%) and rodents (32.4%), but rodents were the most abundant item in terms of biomass (34.5%). Arthropods also showed higher relative frequencies in kestrel pellets (36.4%), but reptiles were the second in order of importance (28.4%) and contributed the most (64.7%) to the total prey biomass. The biomass contribution (66.1%) of vertebrates in the diet of the Burrowing Owl was lower than for the American Kestrel (95.6%) in a fragmented habitat area. Most prey types were present in the diet of both raptors, but we found significant differences in the biomass contributions of each category. Reptiles and rodents were the prey items that contributed most to the differences in the raptors’ diets, in terms of biomass (33% and 20.3%, respectively). Close nesting surroundings (0.5 km and 1 km radius) evidenced a higher proportion of natural vegetation in the kestrel’s (50.6% and 38.9%, respectively) than in owl’s potential home range (25.8% and 16.4%). The differences in diet suggest some degree of niche partitioning of these species likely due to the more flexible owl’s nesting habitat requirements and to the extended nocturnal activity of the species. These results reflect the capability of being complementary species, both exploiting some pests that are harmful for agriculture, and evidencing the importance of both species as regulators of agro-ecosystems in the peninsula of Baja California.

KEYWORDS:

• Athene cunicularia
• diet
• Falco sparverius peninsularis
• lacertilians
• orthopterans
• segregation

Acknowledgements

To Abelino Cota-Castro, Tomás Avendaño, Carlos Palacios-Cardiela, Armando Falcón-Brindis and Raquel López-Bolaños for their assistance both in the field and laboratory. To Carmen Guzmán-Cornejo, Pablo Yorio and Fernando Martínez for valuable technical advice.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

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Additional information

Funding

MGF received a scholarship (779015/616368) from Consejo Nacional de Ciencia y Tecnología. RRE received financial funding for the research from Consejo Nacional de Ciencia y Tecnología-Centro de Investigaciones Biológicas del Noroeste.