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How trees can improve biodiversity on free-range poultry farms

David Brass in a woods holding a hen

Trees planted on poultry farms in Cumbria are providing benefits for biodiversity, new research has suggested.

The work evaluated how trees planted on farms that supply The Lakes Free Range Egg Company have made a difference to wildlife.

The Woodland Trust commissioned the research.

Trees were integrated on to ranges owned by or supplying The Lakes to improve health and welfare of birds. But they have also proven to improve wildlife habitats.

Over the past five years, biodiversity surveys have been carried out in spring and summer on nine poultry ranges.

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 by Paul Arkle and Seamus Eaves of Cumbrian Farm Environmental Partnership was to assess what wildlife used this tree habitat and how farmers could further enhance its value.

A poultry range
A poultry range ©CFEP-Paul Arkle

Birds

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.

Researchers said this was because as trees become more established, canopies start to merge, and birds prefer the more open tree cover that is present during the earlier stages of the range planting schemes.

Butterflies

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.

Moths

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

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.

‘Fascinating’

The Lakes’ Mr Brass, 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.”

Valuable foraging

Mr Arkle said: “There is no doubt that the combination of planted trees and structurally diverse ground cover vegetation creates areas of a woodland edge type habitat on the free-range hen ranges which benefits a range of wildlife species including birds, bats and their prey and particularly moths.

“The planting schemes provide valuable foraging sites for birds prior to the autumn migration or to build up energy reserves of overwintering species.

“As there are currently more woodland birds on the endangered list than of any other habitat, the planted ranges may be important in helping to conserve threatened bird species.

“This habitat may become increasingly important for populations of bird species that are shifting northwards in response to climate change, such as blackcap.”

High standards

Helen Cheshire, lead farming advocate at the Woodland Trust, added: “Today’s consumers expect food producers to meet high standards of animal welfare, deliver a safe and nutritious product and respect the natural environment.

“Integrating trees into free-range poultry production helps farmers achieve these standards. Trees on farms can improve animal health and welfare, as well as production – both in the quality and quantity of eggs.

“This management practice has led to the development of a premium market for woodland eggs – eggs laid by free-ranging hens with access to tree cover – and has been shown to improve a farmer’s income.