BIOMETRICS & PARTRIDGES - PARTRIDGE COUNT SCHEME | The long-term index of grey partridge pair density (see Figure 1) shows that
sites that have participated in the PCS prior to 1999 (long-term sites) recorded an average 13% decline in breeding density, giving a national average spring density of 5.9 pairs/100ha (250 acres), while new sites (joining since 1999) recorded a smaller decline of 1%, remaining at an average of three pairs/100ha (250 acres). The warm, dry May fostered hope of a good summer for partridges. This was
literally washed away when heavy rainstorms fell in mid-June at the peak of the grey partridge hatching period and continued for several weeks. East Anglia and the south- east were especially hard hit. Into July and August, Scotland and northern England were wetter than average, although the second half of August became more settled and warmer, particularly in East Anglia and the south-east. The difficult harvest and problems with access to the ground for counting resulted in the PCS receiving 512 autumn counts, 20% fewer than were returned in autumn 2015 (see Table 1). The total number of partridges recorded nationally this autumn was 20,900. Nationally, the average autumn density reached 16.7 birds per 100 hectares, down from the 19 birds per 100 hectares in autumn 2015. Despite poor productivity on many individual farms and shoots, the national
average Young-to-Old ratio (YtO) was 2.1 chicks per old bird. Late broods may well have helped cushion the effects of the wet early summer. Productivity was similar to that in the damp summer of 2015 (2.2 YtO), well below the 2.5 YtO average of 2013-2014, but nowhere near as bad as the 1.2 YtO following the terrible summer of 2012. Southern England and the Midlands recorded large falls in productivity (-24% and -21%) compared with 2015. Only Scotland recorded a large improvement in productivity. Thankfully, despite the downpours during and after hatching, all regions (excluding Wales) exceeded the 1.6 YtO required for a stable population. In the wider countryside where less effective action is taken for grey partridges, the effects of this summer are thought to be generally worse for grey partridge numbers. Adverse summer weather cannot be prevented and could be something
partridges will face more regularly in the future. It should be appreciated that this summer’s productivity could have been much worse for PCS members if they did not have chick-food-producing habitat and management in place to minimise losses. More farms and shoots throughout the country (not just those involved in the PCS) need to address this aspect of the grey partridge lifecycle and implement management if they are to improve brood survival – in both good years and bad.
BACKGROUND
Partridge counts can offer valuable insight into how well your partridges breed, survive and benefit from your habitat and management provision throughout the year. Each count (spring and autumn) is easy to carry out and helps assess the previous six months without the need for continual monitoring. How to count: Record what partridges you see – using binoculars helps when examining each pair or covey. Spring: Ensure winter coveys have
broken up and breeding pairs have formed – typically in February and March. Record all pairs and any single birds. Autumn: Wait until most of the harvest has finished – ideally between mid-August and mid-September. Record adult males, adult females and young birds in each covey separately. Don’t assume a covey is two adults and some young. In a high 4WD drive around fields and then criss-cross the whole field to check the entire area using the tramlines to minimise crop damage.
www.gwct.org.uk/pcs
TABLE 1 Grey partridge counts
Densities of grey partridge pairs in spring and autumn 2015 and 2016, from contributors to our Partridge Count Scheme Number of sites
(spring) Region 2015 2016
South East
Midlands Wales North
Scotland N Ireland Overall
85
192 133 2
163 91 -
666 86
177 123 2
142 92 1
623
Spring pair density (pairs per 100ha)
2015 2016 Change (%)
1.6 5.6 3.2 5.2 4.7 2.6 -
4
1.8 5.2 3.2 0.7 4.4 2.5 5.9 3.7
12.5 -7 0
-87* -6
-3.8 -
-7.5
Number of sites Young-to-old ratio (autumn)
(autumn) 2015 2016 98
174 120 1
157 89 -
639 66
134 104 1
127 79 1
512 2015 2016
2.1 2
2.4 1.1 2.2 2.1
2.2
1.6 2
1.9 0
2.3 2.7 2
2.1
Autumn density (birds per 100ha)
2015 2016 Change (%)
12.8 22.2 16.8 35.6 25
11.7 -
19.0
12.6 18.8 12.4 2.9
23.2 11.7 20
16.7 -6
-15 -26
-92* -7 0 -
-14
* Small sample size. The number of sites includes all those that returned information, including zero counts. The young-to-old ratio is calculated from estates where at least one adult grey partridge was counted. The autumn density was calculated from estates that reported the area counted.
www.gwct.org.uk GAME & WILDLIFE REVIEW 2016 | 31
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