Consumption of arthropods by hummingbirds in the Sierra Madre de Chiapas, Mexico

Abstract

An organism's morphological features can determine the type of prey they consume due to adaptive advantages in capturing them, for example, the shape and length of the bill in birds. Hummingbirds have been considered specialists in nectar consumption. However, they have been documented to also be important insectivores in ecosystems. In this study, we evaluated arthropod consumption by hummingbirds in relation to their bill and capture strategies. We theorized that hummingbirds with short-medium bills (9-11 bill length to body mass cube root ratio) capture a higher proportion of non-flying arthropods, as they have a lower linear speed of closure of the bill tip relative to the base, while species with long bills (13-14) capture mainly flying arthropods. The study was conducted in El Triunfo Biosphere Reserve, Chiapas, southeastern Mexico from 2015 to 2016, where seven hummingbird species that captured arthropods, their strategies of capture, and the type of prey consumed were recorded. We also analyzed the stomach contents (n = 72 stomachs) collected in the Sierra Madre de Chiapas. We calculated the frequency of occurrence of arthropods and their diversity, as well as the breadth of the feeding niche and the bill-prey relationship of 15 hummingbird species. The Green-throated Mountain-gem ( Lampornis viridipallens) and Rivoli's Hummingbird ( Eugenes fulgens) presented the highest richness of arthropod consumption. Arthropod prey belonged to eight orders, where Hymenoptera and Diptera were the most frequent. The most recorded capture strategies were on the substrate in sustained flight (37.5%) and hovering in sustained flight (33.3%). A positive association was found between the type of arthropods consumed and the morphological traits of the hummingbirds, non-flying arthropods were captured by hummingbirds with short-medium bills, while hummingbirds with long bills captured flying arthropods. Morphological adaptations for food resource use are a trait that determines food selection, capture, and handling success.