BTO Breeding Nightingale Survey 2012
Harry Green
BTO Worcestershire Regional Representative
In 2012 BTO organised national Nightingale survey, following on from previous surveys during the last 40 years. The 2012 survey aimed to investigate distribution and population change; habitat associations; and the proportion of males that are paired. The earlier surveys aimed for complete national coverage whereas the 2012 survey was based on tetrads pre-selected by BTO.
The Nightingale is a declining summer immigrant to Britain which is at the north-western edge of its range. Worcestershire is now on the very edge of that range and the distribution here has retracted to the southern parts of the county in the last forty years, although occasional birds turn up elsewhere. Numbers are now low. This means that records from Worcestershire are particularly useful in following future changes.
The 2012 survey was based on tetrads where Nightingales had been recorded during the previous ten years, and in the 1999 survey, as well as additional sites occupied since 2007 and identified from County Bird Reports, BTO Atlases, BirdTrack records, and local knowledge
The survey
The Basic survey was made between 27th April & 14th May 2012 and involved two early morning visits (between one hour before sunrise and 0830hrs). There was also an Optional Nocturnal Survey made between 18th May & 4th June to help determine the number of paired/unpaired males, and ideally this involved two nocturnal visits (between midnight and 0300hrs). This part of the survey was based on the fact that Nightingale males tend to stop singing when they find a mate and start to nest. Unpaired males sing on into the summer.
First survey period: 27th April to 14th May
1. two daytime visits to every priority tetrad
2. two daytime visits to as many non-priority tetrads as possible
3. additional daytime visits welcome, to any tetrad.
Second survey period: 18th May to 4th June
1. two nocturnal visits to as many occupied priority tetrads as possible
2. two nocturnal visits to as many occupied non-priority tetrads as possible
3. additional daytime or nocturnal visits welcome, to any tetrad
Results
Although the survey was based firmly on designated tetrad coverage other records were provided by several observers. The summary in table 1 shows all these records. Some additional records may have been submitted to BTO via BirdTrack. The BTO Report on the survey has not yet been prepared but when it is the final figures may be slightly different from those shown in table 1..
Most of the tetrads selected for the 2012 survey were covered by surveyors. However, a serious problem was caused by the awful wet and cold weather during the survey period. This made surveying and recording difficult for observers, especially those relying on evenings or weekends for surveying, and it also suppressed Nightingale song. Nocturnal visits designed to check whether males were paired on not were particularly difficult.
| Tetrad | 10 km square | Tetrad type in survey | Tetrad allocated
Yes or no | Total or not done (nd). | Casual records | Likely tetrad total |
| SO66D | SO66 | Priority | no | nd | ||
| SO74H | SO74 | Priority | yes | 0 | 0 | |
| SO74U | SO74 | Priority | n | nd | ||
| SO74W | SO74 | Priority | yes | 0 | 0 | |
| SO74X | SO74 | Priority | yes | 0 | 0 | |
| SO74Z | SO74 | Priority | yes | 0 | 0 | |
| SO75C | SO75 | Priority | no | nd | ||
| SO75N | SO75 | Priority | no | nd | ||
| SO76K | SO76 | Priority | yes | 0 | 0 | |
| SO76R | SO76 | Priority | yes | 0 | 0 | |
| SO77V | SO77 | Priority | yes | 0 | 0 | |
| SO83H | SO83 | Non Priority | yes | 0 | 0 | |
| SO83T | SO83 | Non Priority | yes | 0 | 2+5 | 7 |
| SO83Z | SO83 | Non Priority | no | nd | 4 | 4 |
| SO83L | SO83 | Priority | yes | 0 | 0 | |
| SO83V | SO83 | Non priority | y | 0 | 0 | |
| SO83W | SO83 | Priority | no | nd | ||
| SO83X | SO83 | Priority | yes | 1 | 1 | |
| SO84F | SO83 | Priority | yes | 0 | 0 | |
| SO84K | SO83 | Priority | yes | 0 | 0 | |
| SO84L | SO84 | Non Priority | no | nd | ||
| SO84R | SO84 | Non Priority | yes | 1 | 1 | |
| SO84S | SO84 | Non Priority | y | 1 | 1+1 | 3 |
| SO84V | SO84 | Non Priority | no | nd | ||
| SO84X | SO84 | Non Priority | yes | 0 | 2 | 2 |
| SO84Y | SO84 | Non Priority | yes | 0 | 0 | |
| SO84B | SO84 | Priority | yes | 0 | 0 | |
| SO84J | SO84 | Priority | yes | 0 | 0 | |
| SO84T | SO84 | Priority | yes | 0 | 0 | |
| SO84W | SO84 | Priority | yes | 5 | 1+4+1 | 6 |
| SO86A | SO86 | Priority | yes | 0 | 0 | |
| SO86D | SO86 | Priority | yes | 0 | 0 | |
| SO87B | SO87 | Priority | yes | 0 | 0 | |
| SO93E | SO93 | Priority | yes | 0 | 0 | |
| SO94A | SO94 | Non Priority | yes | 0 | 0 | |
| SO94E | SO94 | Non Priority | yes | 0 | 0 | |
| SO94S | SO94 | Non Priority | no | nd | ||
| SO94D | SO94 | Priority | yes | 0 | 0 | |
| SO96I | SO96 | Non Priority | no | nd | ||
| SP04U | SP04 | Priority | yes | 0 | 0 | |
| SP06Y | SP06 | Priority | yes | 0 | 0 | |
| SO83P | SO83 | Casual records | 1 | 1 | ||
| SO85L | SO85 | Casual records | 1 | 1 | ||
| SO84N | SO84 | Casual records | 2 | 2 | ||
| Totals | 8 | 28 best estimate overall |
Table 1. Shows the list of tetrads in the survey and the results. There are also records from three tetrads that were not selected for the survey.
Table 2 shows the number of singing male nightingales counted in previous surveys compared with the 2012 survey. The figures for 1998 are from a local survey (not part of a national survey). Otherwise 1976, 1980, 1999 and 2012 were all BTO National Surveys. The column designated “1999 plus later casual records so a guess at likely count if no change. Tetrads selected from this list formed 2012 survey sites” suggests the totals that might have been expected in the 2012 survey if there had been no changes in population or distribution. The ‘estimated guess’ was about 60 singing males. In fact in 2012 only 28 singing males were recorded. There may have been unreported males elsewhere in the county, and the bad weather may have led to under-recording. However it seems likely that the Worcestershire Nightingale population has continued to decrease and birds are now only found in relatively small areas in the south of the county with occasional solitary birds singing elsewhere. It will be interesting to see the results of the full national survey.
BTO surveys and other data show a slow decline in the distribution of Nightingales in England extending over many years with a slower reduction in overall numbers. Likely causes are pressures on migration and in winter quarters, perhaps compounded by habitat loss in Britain such as disappearance of over-grown hedges, scrubby places and woodland coppice management. The increasing numbers of deer are also reducing habitat quality and cold wet springs may be reducing nesting success. This is a summary from http://blx1.bto.org/birdtrends/species.jsp?s=nigal&year=2012 where there are many references to publications.
The provisional results and maps for the new BTO Atlas show a staggering national loss between 1995 and 2008 of 53%.
A series of reports for Worcestershire have been published in Worcestershire Record perhaps most easily found by visiting the web site www.wbrc.ork.uk and searching Worcestershire Record for Nightingale.
In view of the changes in Worcestershire it will be well worth recording nightingales every year in the future. Please enter your records on BirdTrack or send them to Worcestershire County Bird Recorder, or send them to me. Please remember Nightingales are now scarce birds so please take care not to cause disturbance to the birds or damage to habitat when they are found.
| 10x10 km squares (or part thereof) forming BTO Worcestershire | 1976
BTO survey | 1980
BTO Survey | 1998
Local survey | 1999
BTO survey | 1999 plus later casual records so a guess at likely count if no change. Tetrads selected from this list formed 2012 survey sites | 2012
Sample tetrad survey plus allocated tetrads. Squares designated by a dash indicates no tetrad surveyed |
| SO 56 | 1 | 0 | 0 | - | - | |
| SO 66 | 0 | 0 | 0 | 1 | 1 | - |
| SO 73 | 2 | 0 | 4 | 6 | 1 | - |
| SO 74 | 6 | 3 | 11 | 12 | 11 | 0 |
| SO 75 | 2 | 0 | 0 | 2 | 3 | 0 |
| SO 76 | 1 | 0 | 0 | 1 | 1 | 0 |
| SO 77 | 0 | 0 | 0 | 0 | 1 | 0 |
| SO 83 | 1 | 0 | 2 | 4 | 11 | 13 |
| SO 84 | 2 | 9 | 7 | 16 | 17 | 14 |
| SO 85 | 0 | 0 | 0 | 0 | 0 | 1 |
| SO 86 | 3 | 5 | 0 | 1 | 2 | 0 |
| SO 87 | 1 | 0 | 0 | 1 | 1 | 0 |
| SO 93 | 0 | 0 | 0 | 0 | 5 | 0 |
| SO 94 | 10 | 14 | 9 | 6 | 5 | 0 |
| SO 95 | 50 | 24 | 0 | 0 | 0 | - |
| SO 96 | 2 | 8 | 0 | 2 | 2 | 0 |
| SO 97 | 0 | 0 | 0 | 0 | 0 | - |
| SP 03 | 6 | 6 | 8 | 6 | 0 | - |
| SP 04 | 0 | 1 | 0 | 0 | 1 | 0 |
| SP 05 | 1 | 10 | 0 | 0 | 0 | - |
| SP 06 | - | - | 1 | 1 | 1 | 0 |
| SP 07 | - | - | 0 | 0 | 0 | - |
| SP 13 | - | - | 0 | 0 | 0 | - |
| SP 14 | - | - | 0 | 0 | 0 | - |
| Totals | 88 | 70 | 42 | 59 | 63 | 28 |
| BTO survey report totals. | 92 | 66 | NA | NA | NA | NA |
Table 2. Numbers of Nightingales recorded in 10x10 km squares during the BTO 1976 and 1980 surveys; reported in 1998 (local survey); recorded in 1999 BTO survey; and reported during the 2012 sample survey. The national survey report totals in 1976 and 1980 differ from the county totals because some records were probably sent directly to BTO and there was confusion over boundaries between Herefordshire and Worcestershire
Acknowledgements
Very many thanks to all who counted, or attempted to count, singing Nightingales in 2012 for the BTO Survey and to birdwatchers who provided additional records, especially Rob Prudden who gathered records from several sources.
Images
01. BTO
02. Nightingale. Ray Bishop
