Winter feeding grey partridges on the fringe

We want to encourage more people to feed partridges on hill farms to provide emergency food sources to help survival in severe winters. © Phil Warren/GWCT

BACKGROUND

In the UK, grey partridge numbers have declined by 93% between 1970 and 2018 and the species has been red-listed as a Bird of Conservation Concern since 1990. Declines have chiefly followed intensification of cereal production. Grey partridges are also found on hill farms in northern England, but numbers here are susceptible to high mortality during severe winters and poor breeding in wet summers. Grey partridges in the UK are mainly associated with lowland cereal farms, but they are also found on marginal hill farms in northern England where they frequent rough grasslands created by low-intensity sheep farming. Here, availability of winter food, particularly in years with prolonged snow, appears a major limiting factor, with birds lost from formerly occupied habitats following the severe winter in 2009/10. Winter feeding is a widely adopted component of wild partridge management in lowland cereal systems. However, in the uplands, although winter feeding occurs, it is largely targeted at pheasants and feeders are often in woodlands, which are generally avoided by partridges. To investigate whether food shortages in winter limited partridge survival, we experimentally increased the provision of supplementary food over two winters. We hypothesized that feeding would improve over-winter survival and breeding productivity.

We selected 10 study plots in Upper Teesdale, County Durham, which were paired in relation to their size and altitude. Plots were on average 2.1km². A low level of winter feeding was already present, with partridges using 17 feed hoppers provided by the local wild pheasant shoot. These were all mapped and we then randomly assigned the increased feeding treatment to one of the paired plots and a network of feed hoppers were installed. We aimed to provide two hoppers for each known autumn covey present, with 57 hoppers provided in the first winter (2010/11), increasing to 76 in the next (2011/12). Owing to the presence of grazing livestock, all hoppers were fenced to exclude sheep and cattle. Feeding was undertaken between November and May, with hoppers checked weekly and filled where necessary. At each visit, partridge use was assessed through recording sightings of birds and searches for their droppings around the hopper.

We surveyed partridges across all study plots at dawn or dusk in spring (March, repeated in April) and again in summer (August, repeated in September) using a callplayback method. The surveyor played an audio recording of a calling male from a vehicle at 10 vantage points along a four-kilometre route along minor roads and tracks through each study plot. At each stop, the observer listened for calls of responding birds and mapped all encounters.

Grey partridges were attracted to feed hoppers, with birds using them a median of 31 days (range 2-104 days) after hoppers were installed, with 96% of hoppers used in the first year, and all were used in the subsequent year. We found no differences in over-winter survival between feeding treatments or years, which averaged 62% (see

TABLE 1

Grey partridge over-winter survival, breeding productivity and spring and summer densities in relation to feeding treatment

Site 2010/11 2011/12 Treatment mean Control mean Treatment mean Control mean (+ se) (n=10) (+ se) (n=10) (+ se) (n=10) (+ se) (n=10)

Over-winter survival 0.61 (0.16) 0.73 (0.22) 0.67 (0.13) 0.46 (0.18) Breeding productivity (chicks/ hen) 5.2 (0.8) 4.2 (1.7) - (mean brood size) 6.2 (0.5) 5.4 (2.0) - Spring densities (birds km²) 6.9 (1.7) 3.2 (1.4) 10.6 (1.8) 4.4 (1.7) Summer densities (birds km²) 20.0 (5.8) 11.5 (5.1) 8.9 (2.4) 2.4 (1.9) KEY FINDINGS

Neither over-winter survival nor breeding success differed in relation to winter feeding. However, the study coincided with two mild winters with little snow and the provision of supplementary food may be more important in more severe winters with prolonged snow.

Philip Warren David Baines

Table 1). No differences in breeding productivity (chicks per hen and mean brood size) between feeding treatments were recorded in 2011, with no chicks raised to fledging in either feeding treatment in 2012 when chick hatch coincided with the wettest June since 1910. Spring densities were 2.3 times higher on the increased feeding plots and densities increased between years by 54% on increased feeding plots and by 38% on controls. Similarly, summer densities were 2.1 times higher on increased feeding plots, declining between years by 56% on increased feeding plots and by 79% on controls.

We expected feeding to increase over-winter survival, but the study coincided with two of the mildest winters (2010/11 and 2011/12) in the past 30 years, with only 15 days and two days with snow greater than 10 centimetres recorded each year. This was in stark contrast to the previous severe winter (2009/10) where 39 consecutive days of snow were recorded. It is therefore likely that the provision of supplementary food is more important to grey partridges in winters with prolonged snow when natural food sources are inaccessible to foraging birds.

Our aspirations in northern England are to encourage further farmers and gamekeepers to feed partridges on hill farms to provide emergency food sources to help survival in severe winters. Grey partridges in the study area have struggled to recover following the severe winter 10 years ago, and this has been exacerbated by a succession of poor breeding seasons caused by untimely wet weather just after chick hatch in mid-June. Filling this winter hungry gap and increasing survival in severe winters will mean that fewer chicks will need to be reared to offset adult mortality. This will buy partridges occupying the hill fringes key time while longer-term land-use based solutions are sought through agri-environment schemes.

Grey partridges have struggled to recover following severe winters and a succession of poor breeding seasons caused by wet weather just after chicks hatch in June. © Laurie Campbell