Lincolnshire’s Changing Woodland Bird Population

The dawn chorus in a British woodland is a national treasure to be cherished and preserved. From early spring the birds of the local woodlands put on a special show, often missed by most people, who are still tucked up in bed. Even for someone like myself, the problems of pillow separation anxiety, can be a significant hurdle to witnessing one of nature’s best kept secrets.

As the first glimmer of light heralds the start of the day, the woodland birds start to sing. In my experience it is usually the blackbird and robin that start the proceedings, with short bursts of sub-song as a prelude of the full repertory to come. The dawn chorus has been happening in Lincolnshire woodlands for millenniums. During this time it is likely that there has always been low level change as natural populations of birds slowly change. However, within the last thirty years, the dawn chorus has changed in our woodlands and probably more rapidly than it has ever done before.

On a local level, noise and light pollution can have a dramatic effect; with some birds, such as robins singing throughout the night, creating a common phenomenon in towns and cities. On a national level, climate change is surely having an effect with new species adding their calls to the chorus; whilst other more familiar songs are slowing fading, to be lost from our local woodlands.

Preserving something as intrinsic as the woodland dawn chorus may seem an impossible task. The density and structure of Lincolnshire woodlands have changed little in the last 30 years, whilst levels of woodland planting and management for wildlife are probably significantly higher than they have been in the previous 100 years. Yet, despite this, a significant number of our common woodland bird species are showing dramatic declines.

Two former common woodland species are the marsh and willow tits, now notably both in decline within Lincolnshire. A small population of Willow Tit can still be found in Belton Park, Whisby Nature Reserve, Laughton Forest and on the south Humber Bank. Marsh Tit distribution remains wider spread across the county with the species still being found at Belton Park, the Limewoods and Haverholme Park. Willow tits are constrained by their breeding habitat, requiring areas of decaying timber and wetter woodlands to excavate their nest holes – this may be a reason why they have shown such a significant decline in Lincolnshire. Willow tit has now become so rare, that it has been added to the list of species recorded by the rare breeding bird panel (RBBP). The recent BTO atlas 2007-11 record the willow tit as having a 50% population decline between 1988 and 2011, making this the 6th largest contraction across all species. Such figures emphasise the fact that willow tit, now a very rare breeding bird in Lincolnshire, is in serious trouble. Only time will tell how long the species will be retained as part of the Lincolnshire avifauna.

A former Lincolnshire migrant, once commonly found in garden, parks and open woodland, the spotted flycatcher has declined significantly over the last 40 years. Birds generally arrive in the county during the first half of May and throughout the breeding season maintain an even distribution across the county (recorded from 55 locations during the breeding season in 2012). However, it is the density of birds that is cause for alarm: now, where birds were once common, just single pairs remain, with birdwatchers having to actively seek them out. As a long distant migrant there are other factors to consider when trying to determine the reason behind such a long-term decline, with changes effecting the wintering grounds surely contributing?

Woodcock is the only species of wading bird in Britain and Ireland that is adapted to breed in woodland. The nocturnal habits and cryptic nature of this species makes it challenging to monitor the breeding numbers, and therefore the population estimates for Lincolnshire are difficult to quantify. During 2012 the Lincolnshire Bird Club received records of roding males from just three sites (Laughton Forest, Twyford Wood and Chambers Farm Wood), which clearly represents a massive under estimation of the county’s breeding population. Preliminary analysis of the results of the 2013 national BTO/GWTC survey found this species was encountered at just one third of woodlands surveyed. Initial comparisons with surveys undertaken in 2003 suggests a decline in overall site occupancy of around 8% in the last 10 years, with sustainable populations linked to only the larger woodlands. During winter it is estimated that up to 1.5 million individuals may be present in Britain and Ireland; mostly originating from northern Europe and western Russia. In Lincolnshire, this annual migration is best witnessed at coastal sites such as Gibraltar Point, Saltfleetby-Theddlethorpe Dunes and Donna Nook, where migrants can be recorded flying in from the sea during October. Cold weather movements can be just as impressive, with a recent record of 44 at Gibraltar Point on February 7th 2012 – a significant count.

The disappearance of lesser spotted woodpeckers from Lincolnshire’s woodland has been a long and steady affair and many individual birdwatchers now struggle to record this species on an annual basis. Although only eight sites recorded this species in 2012, they may not be quite as scarce as it appears, as they are an inconspicuous species except for a short period in early spring. A wide variety of woodland types may be used and consequently it is likely that the number of breeding territories is under recorded. However, the latest BTO Atlas 2007-11 maps clearly show the decline, and with the species population so thinly spread across the county it is difficult to picture how they will recover.

Following a long period of decline the nightjar has over the past ten years shown a steady increase in breeding numbers in Lincolnshire. This recovery is probably due to habitat, demonstrating that with the correct management, certain species can respond. In 2012 a maximum count of 32 singing males was recorded at the two Lincolnshire breeding sites. Unfortunately, birds seem reluctant to expand into new areas, leaving the species with a very fragmented distribution across the county. One can only hope that once the population is at a sustainable level, then birds will start to explore new sites.

In Lincolnshire, the woodlark is a scare semi-resident and summer migrant. They are early breeders and singing males can be recorded on their breeding site from late February. In 2012 breeding activity was recorded at 11 sites, almost double the number recorded in 2011 (with 17 territories at the principle site, Laughton Forest). Increases have occurred where suitable habitat has become available, especially within forest plantations and more recently on arable farmland. Interestingly, population declines are also suspected in some areas; however, that may not simply reflect changes in the availability of suitable breeding habitat, instead factors outside of the breeding season may be implicated.

In Lincolnshire, the nuthatch above all other species has demonstrated that it is not all doom and gloom in the woodlands. Remarkably the sedentary nature of the nuthatch has not stopped the species slow move north, with the bird virtually unrecorded in the 1970’s, yet by the end of 2010 every patch of deciduous or mixed-woodland now holds breeding birds. They are an easy species to record, and I have recorded their distinct call in isolated churchyards and even in a species rich hedgerow in an arable landscape. As with the species in decline, it is difficult to assess the reason behind the nuthatches success, and whether such success is at the expense of other species, particularly the Lesser Spotted Woodpecker?

With all species of woodland birds, it is difficult to pinpoint any one factor effecting population change. It is likely that in most cases there is a combination of factors that are contributing to change.

The following points represent what are considered to be the key contributing factors ffecting woodland birds:

  • Changing woodland structure – changes to woodland caused by either management and/or local grazing or browsing (e.g. by deer).
  • Woodland fragmentation – the fragmentation of woodland, along with the sedentary nature of some species is likely to effect local populations.
  • Invertebrate populations – changes in the local invertebrate population will effect food resources for some species.
  • Predation – possible increases in the level of predation from a wide source including birds of prey, crows, great spotted woodpeckers and grey squirrels causing the loss of nests and nestlings.
  • Inter- species competition – similar species competing for the same resources may be a contributing factor (e.g. great spotted and lesser spotted woodpeckers).
  • Recreational use – on a local level recreational use (e.g. paintballing and mountain biking) may have a negative impact on woodland breeding birds.

On a national level, changing conditions for long distant migrants in their wintering grounds (e.g. habitat and climate) and available food resources during migration also may impact on breeding success.

The management of woodlands for birds must provide both nesting and feeding resources for priority species, whilst maintaining a sustainable woodland and incorporating other management objectives. Appropriate management of the canopy and scrub layers can offer many benefits to different species. Additional grazing is a traditional woodland management method, although the influence of deer (which are clearly increasing in Lincolnshire), is surely having an effect on woodland structure, although how this is effecting bird population is difficult to quantify.

Accurate and repeatable monitoring of our local woodland birds is key to providing the correct conservation management for their future. The joint BTO/JNCC/RSPB breeding bird survey (BBS) was launched in 1994 with the aim of monitoring population change of our most common birds. The Lincolnshire Bird Club (as a partner member of the BTO) has actively supported the implementation of the BBS in Lincolnshire, including the annual publication of selected species graphs in the bird clubs annual report. To date between 60-70 active BBS squares are monitored in Lincolnshire, and it is hoped that this number of squares will increase to help build a more accurate picture of the state of Lincolnshire birds. Anyone wanting to contribute to this important survey work should contact their local BTO representative (full details are available on the inside cover of the annual Lincolnshire Bird Club report).

For the dawn chorus to remain as a part of our local woodland, it is essential that we manage our woodlands to ensure that they are fit to support a full assemblage of woodland species, so that further generations can enjoy it in its fully diversity.

Andrew Chick – September 2014

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