Trees boost biodiversity on poultry farms, new research shows

Trees planted on poultry farms in Cumbria are providing benefits for biodiversity, new research for the Woodland Trust has shown.

The trees had originally been planted on ranges owned by or supplying Penrith-based The Lakes Free Range Egg Company to improve the health and welfare of the hens, boosting both the quality and quantity of eggs and making the farms more productive, but they have also become havens for wildlife.

Over the last five years biodiversity surveys have been carried out in spring and summer on nine ranges that supply the company. Three had established trees on them of more than eight years old, three had trees between four and seven years old and three had only had trees planted in the last two years.

The aim of the research, which was carried out for the Woodland Trust by Paul Arkle and Seumus Eaves of Cumbrian Farm Environmental Partnership with the ongoing support of LFREC CEO David Brass and his wife Helen, was to assess what wildlife used this tree habitat and how farmers could further enhance its value. 

Fifty-nine species of birds were recorded across all ranges, 12 of which are currently included on the Red List of Birds of Conservation Concern, including song thrush, tree sparrow and linnet. A further 11, such as meadow pipet and bullfinch, are on the Amber list. The average number of birds recorded was 327. The numbers of breeding pairs on the newly planted ranges increased over the survey period and decreased on the intermediate and established ranges after peaking in 2017.This is because as the trees become more established, the canopies start to merge and birds prefer the more open tree cover that is present during the earlier stages of the range planting schemes .

While this type of planting provides little benefit for butterflies, 14 species were recorded, all of which are considered common, with one exception. The Comma butterfly, whose main breeding and hibernating habitats are open woodland and woodland edges, appears to be continuing to spread throughout Cumbria, where suitable habitat conditions are present, after only being first recorded in the county in the early 1990s.

Small skipper butterflies were also seen. This species prefers open places with long grass, such as rough grassland, field margins and woodland glades. Like the Comma, it has also only recently been recorded in Cumbria but is beginning to spread quite widely in the county.

The composition of tree cover and ground vegetation on the planted ranges reflects the types of habitats used by Comma, Small skipper and other butterfly species. The planted ranges may be augmenting the spread of several butterfly species in Cumbria. This factor could also help to provide some resilience to climate change for butterfly species that are currently undergoing a northward shift in populations.

The surveys recorded 102 species of moth. The highest overall numbers were on the established ranges, and the average number appears to increase with the age of the trees. The open tree cover coupled with relatively diverse ground cover vegetation benefits a wide range of species including several threatened species including Grey Dagger, Sallow and Ghost moths.

Bats were recorded on all nine ranges each year. The most frequently recorded were Common and Soprano Pipistrelle. Foraging activity was greatest where invertebrate prey was most abundant, which corresponded to the areas with extensive tree cover. The bats spent an average of 40 minutes in new ranges and up to two hours on the others.

David Brass, chief executive of The Lakes Free Range Egg Company, which supplies woodland eggs to Sainsbury’s in support of the Woodland Trust, said: “It’s been fascinating seeing the results of these surveys each year. We already know the trees that we and our suppliers have planted bring a range of benefits to our farms in terms of poultry welfare and production, and we’ve always had anecdotal evidence of them attracting wildlife, noticing more birds in particular as we are out and about. 

“Having clear evidence of just how many species we are attracting, and the role being played in term of tackling climate change is fantastic. It is a pleasure and privilege to be able to plant trees, improving hen welfare and profitability whilst creating much needed habitat for wildlife.”

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