The BOS conducted a survey of Yellowhammers in the first 2 weeks of July 2018 to determine their population abundance, distribution and breeding status. We surveyed an additional 45 1km squares in the BOS survey area, along with 18 covered by our annual Summer Random Square Survey (SRSS) - see BOS Map.

The survey went very well with a significant increase of the coverage across the region compared to our normal annual SRSS. Nationally, Yellowhammers have been declining, so we needed to survey them across our area to determine if their population locally is declining at the same rate. A short presentation on the results was given to BOS members as part of our normal monthly meetings. You can view the presentation by selecting this link: Yellowhammer 2018 Survey Summary of Results.

The survey detected breeding in 82% of survey squares, with an average breeding density of 5.8 pairs per km² (85% confidence interval range 4.8 – 6.7 pairs). This gives a total population estimate of 4,900 – 6,800 pairs across the 1200km² of the BOS area. The full findings of the survey are presented in this document: A Survey of Yellowhammers in the Banbury Area in 2018.

Background

Yellowhammers are one of our common and widespread resident birds of the farmed countryside.  Sadly, their numbers have declined over recent decades and they are Red-listed in the latest “Birds of Conservation Concern 4”.  We are able to monitor their changing fortunes though our annual surveys (Winter and Summer random square surveys and the BTO’s Breeding Bird Survey (BBS)). However, we are lacking more detailed information on their distribution and density across the BOS study area, therefore we carried out a specific Yellowhammer Survey during 2018.

In England, Yellowhammers have declined by 26% from 1993 to 2015, and 33% locally, based on a linear trend from the BOS summer breeding surveys. The situation is even worse for the period 1977-2015, with a 62% national and 76% local decline in abundance based on our Winter Random Square Survey. Thus, it appears that Yellowhammers in the BOS area have been just as affected by environmental changes as those across England, hence our interest in performing a more detailed study.

Male Yellowhammers are easy to locate and identify during the breeding season.  Their song – described as “a little bit of bread and no cheese” is easily recognisable with a bit of practise, and their canary yellow head plumage is highly distinctive.  They also have a long breeding season, extending from April through to August, during which the male sings quite regularly.  This means the Yellowhammer is a bird we can survey relatively late into the breeding season, well after many other birds have completed breeding. Our SRSS breeding surveys show that Yellowhammers breed right across the BOS (in over 90% of survey squares), so there is a very good chance of finding them on this survey.

Survey Method

Our aim was to obtain the best estimates of the number of breeding pairs of Yellowhammers per square km and a total population count. This was not going to be an exact science but sufficient to give a good approximation to the numbers present.

We carried out the survey in the first two weeks of July, each survey taking one hour and covering a 1km x 1km square.  The survey took place within the period 06:00 – 11:00 or 17:00 – 20:00, thus avoiding the “lull” in activity around the middle of the day. Each survey square was chosen randomly from those squares we know have reasonable access for fieldwork and are potentially suitable habitat for Yellowhammers. The squares were only surveyed once.

Plan to walk a route around your square in advance, making use of rights of way, to determine where the best places are for potential breeding birds. Listen out for the Yellowhammer’s song and scan hedgerows and trees to locate the singing male.  You will probably locate most birds by song, but keep using your eyes and ears, and note down all yellowhammers seen.

All you need to record is the total number of Yellowhammers seen in your given square and counts of the birds categorised by activity: Singing males, adult carrying food or number of adult pairs seen. We will use the numbers in these categories to try and assess the number of potential breeding pairs. We also ask you to make an estimate of the percentage of the square you managed to survey.

Please record on the survey form the following information:

• Your Name and the date you performed the survey
• The survey square number (OS Grid Reference)
• The total number of Yellowhammers you have seen
• Number of Singing Males – exclude alarm or other calls. Singing males are usually perched on the top of a tree, bush or hedge.
• Number of Adult Pairs seen – e.g. 3 pairs = 6 birds in total
• Number of Adults carrying food

Please try and avoid double counting, i.e. record a bird in only one of the 3 categories: singing, pair or carrying food. We do not require you to go hunting for nests and the general advice is to try and not to disturb the birds on your survey.

Sample Survey Form Results