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Abstract from BTO Research Report No 237:

Henderson, I.G.

Birds Eye Walls: Partnership for Sustainability.
Progress report on the use of pea fields by birds.

Executive summary

1. As part of Birds Eye Wall’s Partnership for Sustainability programme, the BTO launched a breeding season survey of birds on 21 farm sites in the east of England, and an intensive study of Skylarks on five East Anglian farms. The purpose was to investigate the potential of pea crops to be managed productively and in a manner that may prove beneficial to wildlife (here birds).

2. For the extensive survey, volunteer ornithologists surveyed pairs of fields (one pea field and one cereal field per pair), with each field-pair located on a different farm. Observers made up to six visits to their farm plot between March and August, and on each visit they walked around the perimeter of each field recording all birds seen or heard on both the field and boundary. On fields they recorded birds within distance band categories of 0-5, 5-10, 10-20 and over 20 m from the field boundary.

3. During the intensive studies, two observers made records of Skylark activities to ascertain whether this species was using pea fields to nest in or to forage in, and understand how these activities might corresponded to the seasonal shift in crop growth from March to August.

4. The extensive survey revealed that a greater number of species and a greater abundance of most types of species were recorded on pea fields compared to cereal fields. In March however, bare soil was avoided by most species, but much greater use was made of the sparse or developing pea crops from April to June (the key phase). As a consequence, farming activities before April were unlikely to have much affected the birds using the pea fields. However, crops rolled several weeks after drilling would clearly pose some threat to ground nesting clutches of Skylarks and possibly Lapwings.

5. Thrushes, finches and buntings occurred at higher densities nearer field boundaries, and would probably benefit from field margin conservation strips. From intensive studies, Skylarks would only use marginal strips where these occurred on open boundaries between two fields (e.g. beetle banks).

6. Skylarks breeding on peas appeared to continue into June and possibly July, thereby potentially raising more offspring than on cereals. However, when not tied to a breeding site, birds used pea fields much less frequently and often foraged beyond the pea-field boundary. Overall, the mosaic created by pea crops, cereals and other crop types on rotational farms may help to maintain both foraging and breeding habitat for longer over the summer season.

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