Many people believe that the smallest bird in the Uk is a Wren, but it's common knowledge in the birding community that the Goldcrest is the smallest bird. There is however another species of similar size in the Uk and that is the rarer Firecrest, which in some cases have been known to be even smaller than the Goldcrest. Truth is though, they are both pretty much the same size and any particular individual bird has the potential of being smaller or bigger than the other. You may not see these birds that often but that doesn't reflect on their distribution as they are very common in the Uk and can be found on a variety of habitats, including your Garden. You just have to keep a keen eye out for them as they are very small and often flitter around in thick coniferous trees.