Tree Sparrows - Range & Distribution
Tree Sparrows Passer montanus are the scarcer cousins of the more familiar House Sparrows Passer domesticus and were once widespread and common in the UK. However, since the 1970s Tree Sparrow populations have crashed, dropping by 96% and while numbers have stabilised today for every Tree Sparrow today there were perhaps around 20 in the 1970s.
Tree Sparrows - the big picture
On a global scale the Tree Sparrow has an extensive range within the Palearctic and Oriental regions – extending from the Iberian Peninsula and the British Isles in the west to as far as Japan in the east. To the north, their range extends into Russia and Siberia to a latitude of about 70°N and to the south to the north Mediterranean coast to Tibet and then south through Indochina and Indonesia. There have been recent expansions of their range to the southeast and southwest.
The Tree Sparrow is absent from the Middle East and the Indian peninsula but small populations have been introduced to Australia and the USA in the late 1800s.
Both Tree and House Sparrows show a preference for built-up environments in close association with man. However, where their ranges overlap the larger House Sparrow tends to be dominant with the Tree Sparrow displaced to more rural habitats, though there are exceptions to this rule elsewhere in their ranges. Altitude, it is suggested, also plays a part in the range of both Tree and House Sparrows.
An adult Tree Sparrow - photo by Simon West
Tree Sparrows in the British Isles
In Britain, the Tree Sparrow is a rural bird at the northwestern edge of its range that has undergone a massive population decline. (See the adjacent graph from BTO data) As a result the Tree Sparrow is on the UK Red List of species of greatest conservation concern.
The causes of this decline are as yet largely unknown but agricultural intensification is believed to be a primary driver. While Tree Sparrow breeding success has not declined with the population it seems instead that survival beyond the nest has been the critical point of decline.
A BTO graph showing the massive decline in the Tree Sparrow population since the 1970s
Our Hertfordshire Tree Sparrows
In the early 1970s Tree Sparrows were a widespread and common species in Hertfordshire recorded in 90% of the county’s tetrads with breeding confirmed or probable in most tetrads. Since that time the Tree Sparrow population has mirrored the national trend with a sharp crash such that now only the Tyttenhanger breeding colony remains.
While the work of the Tree Sparrow Project has stabilized the population the breeding colony remains very small with an average of 5-10 pairs breeding per year. The colony is one of only three known colonies in the southeast of England with one at Romney Marsh in Kent and another at Beddington Farmlands in south London. Both the populations of these other colonies have recently nose-dived, one as the result of development on the site.
The Dramatic Change in Tree Sparrow Breeding Distribution in Hertfordshire
1967-1973
Widespread & common
2008-2012
Just the Tyttenhanger colony remains