The Haweswater Study
Prior to 2004 the Haweswater population had been monitored sporadically in 1989, 1998 and 2002. From 2004 on it has been surveyed annually by the RSPB.
Methodology
The surveys have always used singing males as the recording unit. Our knowledge of the behaviour and ecology of the species has increased markedly since 1989 particularly as a result of colour ringing studies in Glen Clunie and Glen Esk in northeast Scotland. We now know there is a much higher incidence of second brood attempts than previously thought and that territory boundaries can change between broods. Males can also sing from a variety of song posts including from outside their own territories.
In the light of this new knowledge it is possible that some double counting may have occurred in the earlier surveys. This was particularly as a result of a survey period that extended in to the second brood period and could have assumed discreet additional territories, which were infact already identified. Also, recording was not always at first or last light when males are almost guaranteed to sing, often simultaneously and appear much more likely to be in their own territories. Hence an overestimate of numbers might have occurred through daytime recording.
Since 2004 monitoring has been limited to roughly half an hour before and after first light and from the middle of April to the end of the third week in May. Because of the generally linear distribution of breeding pairs along crags in Lake District valleys, a point count method by which the observer positions himself in the same series of positions in the valley from year to year, lends itself well to a systematic and repeatable survey method with the aim of recording simultaneously singing males where territories are adjacent
Study Area
In the Haweswater area Ring Ouzels breed on the high crags and gullies of the main valleys emanating from the southern aspect of the High Street ridge at the head of the reservoir at Mardale Head. Additionally, Swindale, a valley immediately to the south is also included. For survey purposes this area is split into 12 sections corresponding to different catchments or distinct topographical features as detailed in Figure 2.
Figure 2. Haweswater Study Area (red dots show location of point counts)
Results
Because of possible over-counting as detailed above, a re-evaluation of the past Haweswater surveys has been undertaken. This involved identifying an absolute minimum number of territories that would be expected in each catchment within the study area in order to safely rule out any chance of double counting. If, in the three surveys prior to 2004 the number of recorded territories in any catchment exceeded the expected minimum, the expected minimum has been used as the total. This makes this data comparable with the more rigorous method and analysis used in the present annual monitoring scheme.
The re-evaluated data suggests all study sectors combined should hold a minimum of 16 territories but that when analysed at catchment level the best years held at least 14 definite territories. Using 14 as the peak total to strip out any risk of double counting, the population has undergone a 50% decline by 2008 but with decline only starting in 2006. An intensive study at Glen Clunie in Aberdeenshire begun in 1998 showed a stable population until and including 2001 after which it had shown a 56% decline by 2005 (Sim et al 2005). The re-evaluated Haweswater results suggest decline may have begun later here. However the 2009 results suggest a recovery back to former levels. Results of nine years of survey are presented in Figure 3.
Figure 3: Number of territories located by singing male 1989-2009 expressed as a percentage of the minimum number of territories (16) in the Haweswater study area.
The data without re-evaluation as shown in Figure 4, suggests a larger magnitude of decline and a much earlier beginning. The maximum number of singing males in anyone one year prior to re-evaluation was 23 in 1998. Seven in 2008 represented a 70% decline from this maximum but the recovery in 2009 to 13 brings that back to a 43% decline.
Figure 4: Number of territories located by singing male 1989-2009 expressed as a percentage of the maximum number of territories (27) in the Haweswater study area.
The Buttermere Survey
This survey was first carried out in 2009 by Dave Shackleton and Chris Hind. As yet there is insufficient data to assess trends. It is hoped to repeat it on an annual basis.
Methodology
As for Haweswater
Study area
Ring Ouzels are found throughout the study area of approximately 9.9 km sq. The study area comprises the catchment of Wanscale Beck which is split into upper and lower sectors and the catchment of Gatesgarthdale Beck (see Figure 5). Territories are spread in a linear pattern along lines of precipitous crags except for one in an old slate quarry.