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Grass silage as a new source of winter food for declining farmland birds - BD1455

There is increasing evidence that lack of winter food is a factor limiting the densities of seed-eating farmland birds in pastoral-dominated landscapes. Ryegrass (Lolium) can produce abundant, large seeds on fertile soils but is rarely allowed to flower. In a small-scale trial, plots of final cut silage left in situ over winter produced large amounts of grass seed and attracted large numbers of feeding buntings throughout the winter. Silage grass yields the following spring were reduced by an average of 14%, although natural reseeding increased yield on some plots.

Leaving final cut silage in situ over winter has great potential as a future agri-environment measure aimed at farmland birds on livestock farms. However, it is unclear how seed yield will vary between grass varieties in relation to field closure date and inputs of inorganic fertilizer. We propose a series of small-plot experimental studies to investigate the influence of closure date on seed production in a range of widely grown perennial, Italian and hybrid ryegrass varieties. The project will also assess the attractiveness to foraging birds of 0.5ha blocks of ryegrass allowed to set seed and remain in situ overwinter. The importance of grass seed in the winter diets of granivorous birds will be assessed through the microscopic examination of seed fragments in faecal samples. Agronomic costs of leaving ryegrass in situ overwinter will be assessed, along with three sward restoration techniques. It may be possible to extend the productive life of ryegrass swards through the adoption of sward restoration techniques that promote natural reseeding and germintaion of ryegrass seed.
1. To assess the effects of closure date and inorganic fertilizer application on seed yield for a representative range of early, intermediate and late heading varieties of perennial and Italian ryegrasses.

2. To assess the utility of uncut grass silage as a winter food resource for priority farmland birds and to quantify associated agronomic costs, and specifically:

(a) To assess the usage of seeded perennial ryegrass by granivorous farmland birds in winter.

(b) To assess the importance of grass seed in the winter diets of granivorous farmland birds.

(c) To assess the agronomic costs of leaving ryegrass in situ over winter on intensively-managed farmland.

(d) To assess the utility of three approaches to sward restoration (mechanical removal of dead litter, sheep grazing and cattle grazing).
Project Documents
• FRP - Final Report : BD1455 - final report (revised)   (598k)
Time-Scale and Cost
From: 2006

To: 2009

Cost: £168,722
Contractor / Funded Organisations
Royal Society for Protection of Birds, National Institute of Agricultural Botany
Environmental Protection              
Nature conservation              
Wildlife conservation