Unravelling what is needed to save the ring ouzel

Guest blog by Dr. Innes Sim Conservation Scientist at the RSPB Centre for Conservation Science 

Why are ring ouzels declining?
The ring ouzel, sometimes known as the ‘upland blackbird’, is a species of thrush which breeds in the UK uplands and winters largely in North Africa. It’s a species of highest conservation concern, due to an estimated 58% population decline between 1990 and 1999, and a big decrease in breeding range (a 44% drop in the number of occupied 10 x 10km grid squares in the UK between 1970 and 2010). Yet, until recently, it was also one of the UK’s least-studied birds, with zero scientific papers published on the species between 1981 and 2001. So, this posed a real problem for conservationists: how to save a species about which virtually nothing was known?

Male (lower) and female (upper) ring ouzel

Glen Clunie study
In response to this lack of knowledge, in 1998 the RSPB and Grampian Ringing Group began a detailed study into what makes this species tick, based in Glen Clunie, Aberdeenshire. We counted the number of breeding pairs, monitored their breeding success, and measured their survival by individually colour-ringing nestlings and adults, and re-sighting them in subsequent years. This study, which continues to the present day, has provided intriguing insights into the key stages in the ouzel’s life-history. To cut a long story short, it looks like survival, especially of 1st year birds, has a major influence on the population trend in this species; when 1st year survival is high the population increases, but breeding numbers decrease when 1st year survival is low.

Glen Clunie study area

Tracking ring ouzel migrations using miniaturised trackers
As yet, it is unclear if the main factors limiting ouzel survival are operating on the breeding grounds, on migration routes or in the wintering areas. However, we know from ringing recoveries that UK-bred ouzels travel through France and Spain, on their way to and from their main wintering area in North Africa. Of ringed birds with known cause of death, 77% were illegally killed by hunters, mainly in south-west France. Thus, the distribution of ringing recoveries on migration may simply reflect areas with high hunting pressure, rather than important stopover sites. Hence, we require more precise information on ouzel migration routes, stopover sites and wintering areas. Recent advances in tracking technology mean that it is now possible to track migrant birds throughout their lives with increasing accuracy. The approximate migration route and wintering area of a single adult male ouzel tagged in Glen Clunie was revealed for the first time during 2013-14, using a 1.5g geolocator. See the paper here. Interestingly, this bird stopped off in south-west France for 18 days during October 2013, before completing its journey south to its wintering area in Algeria in a single day. This suggests that this part of south-west France may be an important stopover site for UK ouzels, and might therefore be an important area for future conservation action.

Ring Ouzel fitted with geolocator

Geolocators are a great first step in working out how birds move around on large scales. However, the location accuracy for these devices is relatively low (± 150km), so what we really needed was a device that would provide more accurate data on the locations of ouzels throughout the non-breeding period of their lives. Luckily, such a device became available in 2014 with the introduction of a 2g GPS tag with the potential to provide up to one fix/day throughout the year, to an accuracy of 10m. Thus, in 2015, we fitted 10 of these tags to adult male ouzels in Glen Clunie. This summer we will attempt to re-locate and catch any returning tagged birds, and download their data. Watch this space!

Ring Ouzel fitted with GPS tag

Return of the Super Ouzel?
This summer we will be back in Glen Clunie searching for a special ouzel, aka the Super Ouzel! This bird was ringed as a male nestling in Glen Clunie in June 2008, and has returned to breed here every year since, raising a minimum of 43 young. If he returns in 2016 he will be the new UK longevity record holder, so fingers crossed that he makes it back! See the RSPB’s Nature’s Home Super Ouzel article here.

Male super-ouzel