The Willow Tit – Our Most Threatened Resident Bird

Back from the Brink special: discover the willow tit, our most threatened resident bird

Willow Tits in the UK have nosedived a dramatic 94% loss in population since the 1970s and have disappeared completely from an estimated 50% of their previous breeding range. The most noticeable losses are in the southern parts of England, especially the south-east where they are now considered locally extinct. Generally in the rest of the country, Willow Tit populations are sparse, though post-industrial areas such as north Wales, Durham, Wigan and the Dearne Valley seem to be their remaining strongholds.

The geography of their population gives us some information about the drivers of their decline in the UK. The south-east of England, for example, is becoming hotter and drier. Willow Tits often favour damp scrub or young woodland, as this provides a suitable micro-climate where they can excavate nest holes in rotting deadwood and forage for insects which are abundant in these humid environments. The drying out of these habitats is reducing the availability of invertebrates for food, but also available nest sites – Willow Tits insist on excavating a new nest hole every year and therefore need enough soft wood to be able to do this.

(c) Ian Butler

Southern parts of the country also generally have more arable landscapes, where dense thickets of scrub with bramble, hawthorn and elder are not a common occurrence. Willow Tits have fairly large territory sizes and therefore quite low breeding densities, meaning that young will have to travel further across the landscape to find their own territory when they are ready. To do this sustainably there needs to be a well-connected landscape of hedgerows and scrub, with many larger areas of damp mature scrub / young woodland.

In contrast, the post-industrial areas in the north of England and Wales often exhibit this network of dense scrub corridors, many developed as a remnant of the now disused railway and canal routes which served the coal industry. Many of these industrial transportation routes were closed pre-1980s and the vegetation was no longer maintained, leading to a rapid development of early colonising species (elder, birch, bramble). These are favoured species for Willow Tit as they rot off quickly and provide an abundance of nest sites safe from predators (as they are often surrounded by a foot of bramble). The added bonus is that these corridors continue for miles, following the old routes of railways and canals which crisscrossed the landscape. The suitable species mix and well-connected landscape allows sustainability for Willow Tit populations in these areas.

(c) Ian Butler

The problem is, they are still in decline. Whilst the post-industrial areas supported Willow Tits well for many years, the problem with vegetation is that it matures. The lack of periodic management intervention has meant that scrub and young woodland is developing into mature woodland, and with that, the habitat dries out and a larger canopy shades out the important under-story species where Willow Tits find refuge. In addition, more mature wooded areas attract competition for Willow Tits – Blue and Great Tits often out-compete the Willows for food and nest sites. Great Spotted Woodpeckers also increase in numbers in mature areas and will actively predate Willow Tit young and eggs.

Human intervention also has a part to play. Scrub clearance and making areas look “tidy” often comes at a cost to Willow Tit habitat, removing deadwood and clearing bramble to make way for low-biodiversity “amenity” grassland to housing developments.

The Back from the Brink Willow Tit project in the Dearne Valley is actively using science to underpin the management interventions needed to restore Willow Tit habitat. A radio tracking programme where Willow Tits were GPS located for a week gave us new information about the areas they spent more time in and where they flew straight through. It also showed us that they will travel further than we anticipated when foraging around their breeding territory.

A range of habitat works has been ongoing across sites in the Dearne Valley all in partnership to solidify the type of management needed so it can be continued beyond the end of the project. Selective thinning of mature woodlands will help to re-establish under-story species and create more diverse woodland habitat; planting key species such as elder, alder and hawthorn to establish new habitat and enhance the connectivity of the landscape; strapping deadwood to trees to increase availability of nest sites; and visiting landowners to provide advice on how they can better manage to encourage Willow Tits.

Surveys of the Deane Valley have been completed in 2015, 2018, 2019 and a further survey will be completed in 2020 to monitor the population, particularly in areas where management work has been done. We would always encourage people to report sightings of Willow Tits, whether it is in their garden or local greenspace. Local records are invaluable as it enables us to target areas with Willow Tits which may be missed on surveys.

Whilst the Willow Tit may still be the UK’s most threatened resident bird, there is still hope as numbers increased in the Dearne Valley in 2019 from 2018. The information gathered from research in this project will help to inform best practice guidance for land managers in the future, as long-term management and monitoring will be crucial for the survival of this species.

 

Sophie Pinder 

Living Landscape Project Officer - Back from the Brink

 

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