Few birds are as mysterious as the tree sparrow. This is the familiar house sparrow’s country cousin, easily recognised by its smart chestnut cap and distinctive white cheek with black collar mark. Unlike the house sparrow, both sexes look the same.

The mystery about the tree sparrow comes from its population which over the last century demonstrated a remarkable ability to increase and an equal propensity to crash. The early years of the 20th century were a time of expansion and population growth. Then in the 1930s and 1940s they disappeared from many of the areas they had recently colonised. In the early 1960s numbers started to grow once again until these attractive birds reached their peak of abundance in the early 1970s.

During the 1980s numbers started to fall. The British Trust for Ornithology’s Common Bird Census recorded an alarming 87% decline between 1972 and 1996. Tree sparrows suddenly became rare birds and once thriving colonies disappeared without trace.

Now there are signs that numbers are on the increase once again. Tree sparrows will come regularly to garden feeders, though usually only in rural situations, so keep an eye open for them. They will also readily adopt nest boxes, so if you have tree sparrows in your garden why not put up some boxes for them? They are sociable birds, so the boxes can be erected close together. With luck you might even manage to establish a colony of this enigmatic species.