====== Sparrow decline ======

Large declines of urban and suburban [[https://en.wikipedia.org/wiki/House_sparrow|house sparrow]] //(Passer domesticus)// populations have been recorded in many towns and cities across Europe. In London, sparrow numbers fell by 60% between 1994 and 2004. The cause(s) of the decline is still not resolved.

Prominent theories include:

  * Reduction in the availability of favoured food, either for adults or chicks or both.
  * Increased levels of pollution.
  * Loss of suitable nesting sites.Increased prevalence of disease.   
  * Increased levels of predation.

with other suggestions such as:

  * Mobile phone mast radiation.
  * Fibreglass loft insulation.

To date, no scientific research projects have proven any of the theories - either alone or in combination with others.

Since 2013 there are reports that the rate of decline [[http://bto-enews.org/NXI-1U2MD-7F3CUAWNA5/cr.aspx|has stabilised]] - recent anecdotal evidence suggests that in some areas (of the UK) the numbers may be increasing again.

More details here at the  [[https://www.bto.org/volunteer-surveys/gbw/about/background/projects/sparrows|British Trust for Ornithology]]

//Update April 2020.// Recent RSPB surveys suggest that sparrow numbers may be on the increase in the UK.  See:  [[https://www.theguardian.com/environment/2020/apr/02/house-sparrows-flocking-back-british-gardens-survey-shows|The Guardian]] April 2nd, 2020.

Note: In 2000, UK newspaper //The Independent// offered [[http://www.independent.co.uk/environment/nature/mystery-of-the-vanishing-sparrows-still-baffles-scientists-10-years-on-2056309.html|a prize of £5,000]] for a proper scientific explanation of the house sparrow's widespread disappearance - the prize remains unclaimed.

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Also see: [[content:life_sciences:zoology:cuckoo_decline|Cuckoo decline]] and [[content:life_sciences:zoology:bee_colony_collapse]]