![]() ![]() A study based on BBS results from 1995 to 2006 found a negative correlation between the abundance of deer and Nightingales at a regional level, with the species declining the most where deer population increase had been greatest, and modelling suggested that deer alone could have caused a decline of 14% in Nightingales over this period ( Newson et al. The structural diversity of woodland can be readily reduced by suspending coppicing and rotational cutting, as well as by increased grazing pressure from deer ( Fuller et al. Scrub structure seems more important than its species composition, and the ideal habitat is probably a dome of increasing vegetation heights, with a crown of vegetation dense enough at the centre to create bare ground underneath, and a gradient of ground-cover towards the edges where the species can nest ( Wilson et al. Nests are built on or close to the ground, in a thick field layer that will provide cover for nests and a refuge for newly fledged young. A study based in Cambridgeshire found that territory distribution peaked on areas where scrub height varied between three and five metres ( Holt et al. Canopy height in territories occupied by Nightingales is usually less than four metres in height ( Wilson et al. Nesting Nightingales typically require closed-canopy scrub or young woodland, with bare ground under the canopy for feeding, but also area of low thick vegetation, generally associated with secondary succession and early regeneration after coppicing ( Hewson et al. There is strong evidence, however, that increased browsing by deer has had a negative effect on Nightingale numbers. The potential roles of predation and reduced food quality have been little studied ( Holt et al. Habitat deterioration on the wintering grounds may result in greater winter mortality or in birds arriving on the breeding grounds in poor condition ( Ockendon et al. Wintering habitat of British birds is being investigated by fitting geolocators to Nightingales ( Holt et al. Several hypotheses have been put forward to explain Nightingale decline and are the subject of ongoing BTO research: these include reduction in coppicing, maturing of scrubland and conifer plantation, an increase in deer and their browsing pressure, higher predation pressure, reduced food quality, pressures on migration and deterioration of conditions on the wintering grounds ( Fuller et al. Several studies have highlighted the benefit of habitat management for this species, involving coppicing and control of deer numbers to promote the heterogeneous vegetation structure that Nightingales need. ![]() Conditions on the wintering grounds, such as changes in habitat, are also likely to have carry-over effects into the breeding season. There is strong evidence that deer grazing is having a negative effect on Nightingale numbers. There has been a decline across Europe since 1980, although numbers have been relatively stable since c.1985 ( PECBMS: PECBMS 2020a>) this overall trend masks a stark contrast between severe decreases in southern and western Europe and increases in the east of the range ( PECBMS 2007). It is among a suite of species that winter in the humid zone of West Africa and correspondingly are showing the strongest population declines among our migrant species ( Ockendon et al. Though samples are too small to continue presenting a trend, CES suggested a sharp decline in productivity during the 1980s, perhaps because Nightingale nesting success may be adversely affected by cold and wet springs. This evidence has been sufficient to upgrade the status of Nightingale from amber to the red list of Birds of Conservation Concern in 2015 ( Eaton et al. 2015).ĭespite small and decreasing samples, it has proved possible to calculate a meaningful CBC/BBS trend. In 1976, over 71% of males were associated with woodland, especially coppice and young plantations, but by 2012 this had decreased to 37% and 55% of territories were then in scrub ( Hayhow et al. Unlike previous estimates, the 2012-13 estimates also accounted for detectability, so the decline since 1999 is believed to be higher than the figures suggest. Results from the most recent Nightingale Survey across Britain in 2012-13 indicated that further decrease has occurred since 1999, with 12 population estimates ranging from 5,094 to 5,938 territorial males ( Hewson et al. Atlas surveys in 2008-11 found a 43% reduction in occupied 10-km squares since 1968-72, with withdrawal especially from western parts of the range ( Balmer et al. The national survey of Nightingales organised by BTO in 1999 estimated the population at 6,700 (5,600-9,400) males, a marked range contraction since the previous survey in 1980, but only an 8% overall population decline ( Wilson et al. ![]()
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