Spiking buildings to avoid house martin (Delichon urban) nesting: is it a good choice?

We tested the effectiveness of installing spikes (® EcoPic E-5) on building eaves and windows to avoid the nesting of house martins. We found that spikes cannot prevent the nesting or reduce colony size. The first year after installing the spikes the colony may be partially affected. However house martins are able to overcome the spikes in the next years and rebuild the nests even on the spikes. We conclude that spikes are ineffective as a deterrent system.