Individual study: Depletion rates of hawthorn Crataegus monogyna, blackthorn Prunus spinosa and dog rose Rosa canina fruit in hedges at Monks Wood, Cambridgeshire, England
Croxton P. J. & Sparks T. H. (2004) Timing of berry depletion rates of three common hedgerow shrubs. Agriculture, Ecosystems and Environment, 104, 663-666
Late and reduced frequency of hedgerow cutting is generally recommended to enhance the berry crop and lengthen the duration of friut availability for wildlife. A study was undertaken to examine the availability of berries (mostly eaten by birds and small mammals) throughout the winter of three common woody hedgerow species in the UK; hawthorn Crataegus monogyna, blackthorn Prunus spinosa and dog rose Rosa canina, thus guiding when best to undertake hedgerow cutting.
The study was undertaken at the experimental site at Monks Wood, Cambridgeshire, eastern England. Berry-bearing branches of hawthorn, blackthorn and dog rose were marked on unmanaged bushes up to 2 m above ground level. Those branches selected were considered to be typical of the berry load of each autumn of the study i.e. 1998, 1999 and 2000.
Eash autumn/winter, an average of 23 hawthorn, 17 blackthorn and 44 dog rose branches were monitored. Berries on each branch were counted and recorded at weekly intervals from the beginning of October until either all the berries were gone, or until a final count at the end of February. Only counts of hawthorn berries were carried out in winter 1998/1999. Berries of all three species were counted in the winters of 1999/2000 and 2000/2001.
The total number of monitored berries ranged from 400 to 1,400 per species per winter. There was variation in their consumption and depletion both. Hawthorn berries had largely gone by early December, whilst blackthorn and dog rose fruit remained available until January.
Hawthorn: Berries were consumed rapidly in October with only about 10% remained at the beginning of December in both 1998/1999 and 1999/2000. In 2000/2001, 35% of the crop still remained on 1 December, but exploitation continued steadily until 19 December after which consumption dropped.
Blackthorn: In winter 1999/2000, berries remained virtually untouched until mid-November with over 70% left on 1 December. Exploitation then continued steadily with the crop depleted by mid-January. The 2000/2001 crop was rapidly consumed from early October with only 50% remaining by mid-November. Use then practically ceased with only a further 10% taken over the next five weeks. Consumption then resumed with depletion by the end of January, perhaps due to the appearance of migrating thrush Turdus flocks.
Dog rose: Consumption of dog rose hips was similar between the two winters occurring at a slow, steady rate from the start of October until 1 December, at which time 75% of the crop remained in 1999/2000 and 60% in 2000/2001. From December exploitation was rapid with the hips gone by the third week of January.
Conclusions: The findings support the generally accepted notion in the UK that to maximize availability of the berry crop for wildlife, hedgerow cutting should be undertaken in January when most berries have been eaten or have dropped. The variation in ripening times and preference of different bird ans small mammal species for different berries demonstrates that if planning new plantings of hedges for wildlife, mixed hedgerows extend the provision of winter food resources.
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