Insectivorous birds contribute to the provision of ecosystem services to humans in both human-dominated and natural ecosystems around the world. Natural predation of invertebrate populations is a prime example of one of the key ecosystem services provided by farmland birds in agricultural landscapes. Yet, it is unknown how many invertebrates are consumed by common farmland bird species such as Oriental Magpie-Robin (Copsychus saularis) and Yellow-vented Bulbul (Pycnonotus goiavier), which are abundant in oil palm plantations of Southeast Asia. Therefore, this study estimated the amount of insects consumed by these birds through a feeding experiment. From an assessment of 50 captured birds (25 individuals for each species), the average daily insect consumption of Oriental Magpie-Robin was estimated at 15.03 g/bird, which is slightly higher than Yellow-vented Bulbul (11.67 g/bird). These findings indicate that the potential of the two focal species to suppress insect populations might be limited by body weight and prey preferences. This study demonstrates the advantages of maintaining biodiversity, particularly farmland birds as biological control agents. Future estimates of pest insect consumption in oil palm plantations could potentially be based on the daily insect consumption by both bird species.