The expansion of coffee farming across Central America is linked to a noticeable drop in the share of invertebrates in the diets of forest birds. This finding comes from research conducted in Costa Rica and reported by the University of Utah.
Fieldwork took place at the Las Cruces biostation, where former forested land has transformed into a landscape now comprising about half coffee plantations, a fifth grasslands, and several other outbuildings. Forest cover has diminished to roughly twenty percent of the area. The surrounding farmland is saturated with pesticides, fertilizers, and fungicides, all of which can reduce the invertebrate prey that local birds rely on for nourishment.
To understand what these birds eat, researchers analyzed the diet using radioisotope analysis on 170 feathers drawn from four species. Each food category carries a distinct isotope signature, enabling scientists to trace back what the birds consumed. In addition, the movement of 49 individual birds was tracked with radio beacons to map habitat use and foraging patterns.
The study shows that habitat plays a decisive role in shaping avian diets. Specifically, three of the four species studied consumed markedly fewer invertebrates when inhabiting coffee-dominated landscapes. The Silver-throated tanager and the White-throated thrush were observed to obtain about half as much invertebrate biomass in coffee plantations as they did in intact forest habitats. Meanwhile, resident species such as the Yellow-nosed thrush, which can persist across small home ranges, face a tougher choice: adapt to feeding on fewer caterpillars, worms, and other insects, or risk local extinction if those resources disappear.
In light of these findings, the researchers highlight the importance of strengthening forest reserves to safeguard biodiversity amid ongoing agricultural expansion.
Ancient scientists have explored the idea that food additives might influence cognitive performance in mice, a line of inquiry that underscores the broader interest in how diet and environment affect animal biology and behavior.