Willow Coppice – an Important Habitat for Birds?

Mike Wareing’s farm at Shottle has two fields of Willow planted as short rotation coppice. It is grown as a perennial crop, harvested every three years. On the third year Willow rows are reduced to ground level. Originally the intention was to provide a fuel source under contract, but the financial viability of the crop is now in some doubt. It is with this uncertainty in mind that it was felt important to provide initial observations from ringing in the Willow crop. The intention is to highlight the crop’s useful role as a safe refuge and feeding area for migrant and resident bird species. Initial sampling during July, August and September from 2002 to 2005 has produced promising results.

The study area has only involved one of the two fields of Willow coppice. The two areas are separated by open fields, which predominate the surrounding landscape. Neighbouring fields contain arable and mixed farming practices with livestock including cattle and sheep. There is limited tractor access to the fields of Willow. The fields stand out as shrub or woodland amongst mainly a two-dimensional landscape with occasional trees and small isolated mature woodland pockets. Ringing activities have been along this tractor access ride with mist nets strung together in one 64 metre line through the Willow crop.

Willow growth is rapid with up to three metre of dense annual growth out of each plant common. The new growth restricts visibility into the field and acts as a barrier to avian predators such as Sparrowhawks.

During August the Willow coppice has a high density of insect damage to the leaves. This occurs from June but does not appear to significantly affect crop productivity. Damage to the Willow leaves at Shottle is from the larvae of a Chrysomelid beetle, Plagiodera (Phyllodecta) vulgatissima, commonly known as the Blue Willow Beetle. The shiny coloured chrysomelids are slightly smaller than a ladybird and easily monitored as they readily fall from the Willow. In August beetles were collected and counted. Three sample counts averaged 84 beetles per square metre. Tucker and Sage (1999) considered as a general guide that counts below 100/sq metre do not produce significant damage. In August the whole field looks Autumnal in appearance with damaged brown leaves due to defoliation from chrysomelid larvae. The presence of such an abundance of insects in the Willow coppice is clearly a valuable food source for breeding, moulting and migrating birds.

General observation of the birds ringed in the sample study (0.1% of the whole field) have produced the following interesting records:

• Over 20 species of insect eating birds ringed on each occasion

• Large numbers of birds were ringed with over 150 birds ringed on each session from a 48 metre run in a corner of one field (0.1% of the field)

• On 4th August 2005, of 170 ringed in the coppice, 102 (60%) were in moult, including 32 Long tailed tits barely able to fly.

• Seven warbler species were handled including both Reed Warbler and Sedge Warbler considered rare at the site.

• The field has been used as a roost site for bird species including over a 1000 Swallows for a short period each July.

Willow was planted in an area of low existing wildlife value. Its rides and links with hedgerows and field margins have since provided a site with a high wildlife value and a valuable refuge and feeding area for birds. In a site/habitat worthy of further study we suggest regular monitoring of bird species using the short rotation crop throughout May to September as a Constant Effort Site. (Thank you to Paul Mabbott for identifying the beetle)

G. P. Mawson.

P.S. A sibling beetle Plagiodera Versicolora has become very common in S.E. England in recent years but doesn’t seem to be in our Willow fields as yet.