Causes of change

There is little evidence explaining either the demographic or ecological drivers of the decline in this species, although low survival between breeding seasons has been identified as a major cause of national decline.

Further information on causes of change

Long-term surveys coordinated by the Ring Ouzel Study Group confirm that declines have occurred throughout the British range (Sim et al. 2010).

British & Irish bird observatory data show a decline in spring passage Ring Ouzels at western locations during 1970-98 that matches the estimated UK breeding decline, but no decline at eastern observatories where most birds are of Fennoscandian origin (Burfield & Brooke 2005). These authors infer that, since these populations winter together, the reasons for decline among UK breeders must lie on the breeding grounds or on passage: they also point out that UK birds are more exposed to hunting pressures, particularly in southwest France.

It has proved difficult to establish any reasons for decline that are linked to the breeding grounds (Buchanan et al. 2003). In southeast Scotland, however, the breeding sites that are still occupied tend to be those at higher altitude and that have retained extensive cover of heather (Sim et al. 2007b). In the same study, it was shown that declines were greatest in years following warm summers on the breeding grounds and also greater two years after high spring rainfall in Morocco: these results suggest that the population decline could be linked to reduced food supplies, and consequently higher rates of natural mortality, in autumn and winter (Beale et al. 2006). Large areas of apparently suitable juniper scrub, with abundant berries but no wintering Ring Ouzels, exist in the Atlas Mountains, however (Green et al. 2012).

Low survival between breeding seasons is apparently a major national cause of decline (Sim et al. 2010). Within Glen Clunie, however, Sim et al. (2011) found that varying combinations of demographic factors produced each year-to-year decline, with reduced early-season productivity, rates of re-nesting and first-year survival all playing a part. A two-year experimental study found that the provision of supplementary food during the breeding season did not have an effect on reproductive success or post-fledging survival suggesting that invertebrate food availability was not a problem at this site, although the authors caution that the study area has intensive predator control so the results may only be directly relevant in similar areas (Sim et al. 2015).

Information about conservation actions

The main cause of the decline may be related to low survival between breeding seasons, and the research has not identified any clear causes of decline that are linked to the breeding grounds. Therefore, the options for taking immediate conservation action to benefit Ring Ouzels in Britain appear limited.

However, low post-fledging survival is one of the possible causes of decline which could occur on the breeding grounds. Variation in chick condition was smaller in territories with better habitat (greater grass and sedge cover and less bracken) (Davies et al. 2014); hence increased grass cover may help ensure a greater proportion of chicks are in good condition to survive immediately after fledging. Juveniles forage on invertebrates in grassland during June to mid-July, but then switch to feed mostly on berries on heather moorland until early September, so a wider variety of habitats may be needed later in the summer to support fledged young prior to migration (Sim 2012).