This dataset contains information about local population densities of great tits, blue tits, marsh tits and nuthatches from a manipulation experiment. The time, location and bird species were recorded using a Passive Integrated Transponder (PIT) tag attached to each bird and the information recorded using a Radio Frequency Identification (RFID) antenna within the feeder. Population density was manipulated by programming automated feeders to only open for a specific set of individuals (creating low- and high-density treatments). Local population densities were recorded using automated bird feeders at six experimental and two control sites prior to and during the manipulation. The experiment took place in Wytham Woods, Oxfordshire, UK between January and March 2021, as part of a study on the effects of ecological factors on social structure and information transmission. The work was supported by the Natural Environment Research Council (Grant NE/S010335/1, The ecology of behavioural contagion in natural systems.) Full details about this dataset can be found at https://doi.org/10.5285/1a4dcbb3-c4fb-4bd4-acb3-d03932de9323