Two species in competition often continue long-term in the same environment. This suggests they each have an "edge" which the other does not. In may cases being there first is a big edge. For example, plants consume nitrogen by absorbing it into their roots, making nitrogen unavailable to nearby plants.
Species in competition may directly interfere with each other. An example of this can be seen between the ant Novomessor cockerelli and red harvester ants, where the first interferes with the ability of the second to forage. It does this by plugging the entrances to their rival's colonies with small rocks.[2][3]
↑Pocheville, Arnaud 2015. The ecological niche: history and recent controversies. In Heams, Thomas; Huneman, Philippe; Lecointre, Guillaume; (eds) Handbook of Evolutionary Thinking in the Sciences. Dordrecht: Springer. pp. 547–586. ISBN 978-94-017-9014-7