The lack of available food during winter, often referred to as the ‘hungry gap’, has increased the use of hopper feeders to support game and farmland birds where natural food cannot. Our research has already shown that hoppers keep gamebirds in good body condition and benefit songbirds, but mysteries remained as to how much grain was being eaten by ‘unwelcome’ visitors, including nest predators such as rodents or corvids.
In January 2012 we began an ambitious camera-trapping experiment to address these questions and promote sustainable feeding. Based at three lowland farms that were home to pheasants, grey and red-legged partridges, we adapted their existing use of hopper feeders to trial a feeder comprising a spiral feed dispenser attached to the bottom of a drum, suspended within a cylindrical iron armature clad with wire sheep netting. At each site one feeder was set in cover along a hedgerow and another in the open in an adjacent field, 40 metres away in order to observe the effect of location and set motion-sensor cameras to capture images of any activity at each feeding point. This also allowed us to test further potential improvements, which are outlined below. In total, we studied 259 feeders during two years and two seasons (early and late winter), taking over 160,000 photographs.
Who is eating the grain?
Across all the data collected, 95% of the feeders were used by gamebirds and songbirds as intended, although non-target species appeared in 54% of photographs and consumed 67% of grain provided. We identified 47 different species at the feeders (33 birds and 14 mammals), with ten species accounting for 90% of the photographs. We also recorded six UK Biodiversity Action Plan (UK BAP) priority species: dunnock, yellowhammer, house sparrow, linnet, song thrush and starling.
Table: Estimation of the grain consumed per species category (%) in a week.
Does feeder location matter?
In the paired experiment, gamebirds, songbirds and rodents preferred feeders along hedgerows, presumably because of reduced exposure to predators, whereas a higher number of corvids were photographed in feeders in open fields. When we removed the feeder from the hedgerow to assess the impact this would have, we did not detect a significant increase in use of the feeder in the open field alone compared to feeders that were set along the hedge and in the open field simultaneously.
How long does it take to find the new feeder location?
As another potential solution, we changed the location of each feeder in order to test how long it took for gamebirds, songbirds and rodents to find the new location. We found that gamebirds and songbirds were able to locate a new feeder within just 1-3 days of relocation, whereas rodents needed 2-4 days. Changing location failed to stop mice or rats completely, although it did prevent them from becoming established beneath the feeders.
Does the use of scarecrows work?
In order to limit corvid visits to the feeders, we also trialled the use of rook’s carcasses as ‘scarecrows’ on the top of feeders to address how effective they were for deterring other corvids. Scarecrows reduced the number of corvids visiting feeders by 66%, but they also reduced songbird numbers by 77%, without affecting gamebirds. We cannot advise the use of scarecrows for this purpose until more research is undertaken in this area.
The increased use of feeders on estates looking to re-introduce and increase the numbers of grey partridges, pheasants and songbirds is very encouraging, but these results show that we need to improve the efficiency of hopper use in order to give our birds the best chance of survival. We are working with the University of Southampton (Engineering and the Environment) to explore improved hopper designs that might help to halt the food waste and control the access by non-target species.
- Sánchez-García, C., Buner, F. D. and Aebischer, N. J. (2015), Supplementary winter food for gamebirds through feeders: Which species actually benefit?. The Journal of Wildlife Management. doi: 10.1002/jwmg.889