Window sill spikes like those are very rare in California - I figure that's because of the legal liability issues, should someone "accidentally" fall on them and then sue for injuries. I also doubt they are intended for pigeons, because pigeons would not normally roost so near the pavement. Plus, they could easily avoid the spikes - no so with the brush-like narrow spikes used in the Bay Area (like on BART) to deter the little poopers.