David Element

Wildlife Photography

and Digital Video Images

____________________ Birds 25 - House Sparrows 1

                                             HOUSE SPARROW Passer domesticus (m)

                                             HOUSE SPARROW Passer domesticus (m)

                                             HOUSE SPARROW Passer domesticus (m)

                                             HOUSE SPARROW Passer domesticus (m)

                                               HOUSE SPARROW Passer domesticus (f)

• Many reasons have been postulated for the dramatic decline in the urban House Sparrow population. Amongst the most feasible are loss of habitat associated with the grubbing out of Privet hedges in cities, loss of suitable nesting and feeding sites due to modern house construction techniques, some form of epidemic due to viral infection or the insidious effects of chemicals, either from traffic, industry or agriculture. Bizarrely for such a formerly populous species the 'crash' could even be due to too much in-breeding (consanguinuity) although the Sparrow genome would need to be studied in some detail before this presumption could be qualified. This phenomenon would depend on the degree of natural variation and in-bred resistance to disease or climate change. Certainly the number of available insects for feeding young Sparrows appears to be much lower than it used to be. However, there is little evidence to suggest that the surviving Sparrows are unhealthy and there are no dead bodies lying about, suggesting that the breeding process is being affected, but with no obvious excess mortality amongst the survivors that manage to leave their nests. This evidence therefore tends to point against any epidemic and towards failed breeding due to other causes. Those experts who have studied this phenomenon in detail would be able to make the distinction between reduced clutch size/failure to lay as opposed to the development of initially healthy broods that starve in their nests prior to fledging. Sparrowhawks and domestic cats do take their toll, but as cats in particular have killed these birds in quantity for many years without causing a population crash these predators cannot be culpable all on their own. In the countryside altered farming practices (mainly post-Second World War) have certainly affected the wellbeing of a number of previously common and familiar rural bird species and the value of unstrimmed hedges or unsprayed set-aside or fallow land allowing access to untainted seeds and insects cannot be understated. Likewise, urban gardens with monocultured mown lawns present little of any value to wildlife. There does seem to have been some reversal to this trend recently, so hopefully the population will eventually climb back to earlier levels.

Links to 'ARKive' species accounts:

• For further information about the House Sparrow use the following link: http://www.arkive.org/species/ARK/birds/Passer_domesticus/

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