A new study by Wild New Forest has highlighted dramatic and rapid changes in New Forest woodland bird populations. The study focussed on 21 woodland bird species, mostly small songbirds, in the largest block of contiguous woodland in the central New Forest. Detailed survey work was conducted in 2022 and the data compared to those collected by the same observers (Russell Wynn and Marcus Ward) using the same methods in 2009-11, to assess how woodland bird distribution and abundance has changed over the last decade.
The New Forest survey area included a variety of woodland types, including ancient woodland dominated by Oak and Beech, riverine woodland dominated by Alder, and non-native conifer plantations as shown above.
Although the total number of birds recorded remained relatively stable, there were clear differences between species depending on their migration strategy; in most cases, the observed New Forest trends mirrored regional and national trends. Two of our long-distance migratory songbirds, Wood Warbler and Willow Warbler, showed the steepest declines, with Wood Warbler now sadly on the verge of extinction as a New Forest breeding bird. However, other songbirds such as Blackcap and Chiffchaff have markedly increased over the last decade, probably due to different migration strategies that buffer them against negative impacts such as predation and habitat loss.
Wood Warbler is one of the biggest losers, and is at risk of imminent extinction as a New Forest breeding bird.
Encouragingly, most of the resident bird species included in the study show stable or increasing trends, with some previously scarce birds such as Firecrest now becoming common and widespread, facilitated by a milder climate. There is also tentative evidence that some species, including the highly protected Woodlark, are benefitting from recent habitat restoration work that has been conducted by Forestry England, including removal of non-native conifers and stream restoration. However, long-term plans to remove most of the non-native conifers from the New Forest will inevitably have negative future impacts on species such as Goldcrest, Crossbill, and Siskin that are closely tied to these tree species.
Woodlark is benefitting from ongoing habitat restoration work, particularly removal of non-native conifers from heathland sites.
The intention is to repeat the survey every five or ten years to assess future change and provide underpinning data and evidence to inform future forest management. The executive summary of the report is provided below, and a PDF of the full report can be accessed at the following link (the report also includes appendices containing links to videos of several of the surveyed bird species in their preferred habitats):
Executive Summary
A resurvey of woodland passerine and near-passerine birds was conducted in the central New Forest in 2022, with the aim of repeating surveys conducted in 2009-11 to assess decadal change. Breeding abundance and distribution trends were primarily obtained via a roving survey in the May-June period, covering a block of woodland centred on Bolderwood and Rhinefield that covers nearly 40 km2. This was supplemented by a monthly survey that provided information on temporal distribution and detectability of target species through the year. Both surveys were effort-based, with the same two experienced observers using pre-determined transects over consistent time periods.
A total of 21 species were surveyed, of which nine increased, eight decreased, and four were broadly stable (see Table 1). The total number of birds recorded during the roving survey remained relatively stable at around 2500 birds, with an insignificant increase of just 8% between the 2009-11 and 2022 survey periods. However, this overall result masks major differences between species with different migration strategies, with all but one of the long-distance summer migrants showing decreasing trends, the two medium/long-distance summer migrants showing moderate increasing trends, and most of the resident species showing stable or increasing trends; in most cases these survey results are consistent with regional and national trends.
Table 1: Summary of the conservation status of 21 woodland breeding bird species that are the focus of this survey. Species are subdivided into three sections: long-distance summer migrant species, medium/long-distance summer migrant species, and resident and short-distance migrant species, as described in Section 3 of the full report. BOCC5 = UK conservation status as listed in Birds of Conservation Concern 5 (Stanbury et al., 2021); UK trend = BTO/JNCC/RSPB Breeding Bird Survey (BBS) 10-year trend from 2010-2020; SE Trend = BBS 10-year trend from 2010-2020 (note that for relatively data-poor species such as Tree Pipit and Crossbill this trend has been replaced with the equivalent trend for England); Central NF Trend = decadal trend from 2009-11 to 2022 in the central New Forest survey area; Confidence = confidence level for the observed Central NF Trend. Further details of survey methodology are provided in Section 2 of the full report.
Of the long-distance summer migrants, the dramatic decline of Wood Warbler is of particular concern, having gone from an average of 105 territories in 2009-11 to no more than two or three singing males recorded in the survey area in 2022. Cuckoo, Willow Warbler, and Garden Warbler are also showing moderate to major decreasing trends. Perhaps surprisingly, all four of these species appear to be decreasing more rapidly in the New Forest than regionally or nationally, whereas Tree Pipits appears to be declining less rapidly, potentially due to increased availability of suitable habitat through establishment of clearfell following removal of non-native conifers.
In contrast, most resident and medium/long-distance migrant species including Blackcap, Chiffchaff, Firecrest, and Siskin, are increasingly abundant and widespread in the central New Forest, while others such as Marsh Tit and Crossbill appear to be at least stable and possibly increasing (the latter two in contrast to declining regional and national trends, which may reflect the relative stability of their New Forest habitats compared to those in the wider countryside). The survey did throw up some surprises, including major increasing trends for Spotted Flycatcher and Bullfinch that contrast with decreasing regional and national trends.
There is some evidence that habitat restoration work may be benefitting resident and short-distance migrant species that are showing increasing trends; this includes Woodlark benefitting from heathland restoration through removal of non-native conifers, and Grey Wagtail benefitting from stream restoration through increased availability of natural wetland habitat. However, ongoing removal of non-native conifers as part of the Forest Design Plan will likely have negative impacts for species that are reliant upon that habitat for nest sites and food, including Goldcrest, Crossbill, and Siskin.
Overall, the data presented in this study show a complex and fast-changing picture for the woodland bird assemblage in the New Forest; the next resurvey is scheduled for 2030, and will no doubt reveal further changes and surprises!
Comments