The Cliff Swallow (Petrochelidon pyrrhonota) is a highly social avian species known for building intricate, gourd-shaped mud nests in large colonies. These long-distance migrants travel from North America to wintering sites across South America. The species is a strict insectivore, relying entirely on arthropods captured in flight. This specialization links their survival directly to the availability of aerial insect populations.
Primary Insect Prey
The diet of the Cliff Swallow is opportunistic, focusing on small, soft-bodied flying insects captured in large quantities. Analyses of stomach contents reveal a diverse menu, frequently encompassing over 80 different insect families. The most common orders consumed include flies (Diptera), true bugs (Hemiptera), beetles (Coleoptera), wasps, and winged ants (Hymenoptera). Swallows prefer insects that aggregate, such as swarming midges or emerging aquatic insects, which allows for highly efficient feeding. Nestling diets often show a higher concentration of larger, more energy-rich items, such as grasshoppers and certain types of beetles, delivered by the foraging parents.
Foraging Behavior and Hunting Techniques
Cliff Swallows acquire their prey through aerial hawking, capturing insects in continuous flight. They are highly social foragers, often hunting in large, dynamic flocks that can number from a few dozen to over a thousand individuals. This group behavior functions as an information-sharing network, allowing unsuccessful foragers to follow successful birds back to areas where dense insect swarms are located.
The birds typically forage high in the air, frequently 50 meters or more above the ground, taking advantage of thermal air currents that concentrate swarming insects. They also hunt lower to the ground, especially over water bodies, open fields, and pastures where insect activity is high. When feeding young, swallows collect numerous small insects in their throats to form a single food mass, or bolus, before returning to the nest to deliver the concentrated meal.
Seasonal and Regional Diet Shifts
The makeup of the Cliff Swallow’s diet is highly variable, shifting in response to seasonal cycles and local environmental conditions. During the breeding season, foraging effort is intense and focused on maximizing energy intake for both the adults and their broods. This period demands the highest volume of prey, causing parents to travel up to 6 kilometers from the colony site to find sufficient insect concentrations.
Regional differences in habitat also influence the diet. Colonies near coastlines or large bodies of water rely more heavily on aquatic insect emergences compared to inland colonies foraging over grasslands. Adverse weather conditions, such as sudden cold snaps or heavy rain, suppress aerial insect activity and force swallows to alter their hunting altitude. They may forage closer to the ground or briefly on the surface to target less-mobile terrestrial invertebrates like ants.