Worcestershire Record No. 26 April 2009 pp. 40-42

Steve Davies

During the breeding season of 2007, I conducted a territory mapping study of Corn Buntings at Wick Grange Farm near Pershore (Davies 2007) in order to attempt to ascertain the number of male Corn Buntings holding territory on this intensive farm. A total of 8 males were assigned to territories on Wick Grange Farm, with an additional single male holding territory on neighbouring Glenmore Farm.

With the kind permission of wildlife friendly farmer Tom Meikle, who runs Wick Grange Farm, I was able to make a repeat study in 2008 to identify any decline or increase in the number of Corn Bunting territories between years using the results from 2007 as an index. Rob Kings from Glenmore Farm was also keen to know if Corn Buntings were present on his farm in 2008 and also allowed me access to his land.

Due to the rotation of crops within the study site I expected the locations of territories to differ between years. It was fortunate that I had recorded the territorial males on Glenmore Farm in 2007 because I had a datum point from which to monitor a larger sample of the local population. This would also allow for any movement of birds between farms due to changes in cropping/stock regimes. I would be able to record birds present on both farms. As long as I followed the same survey route as in 2007 (see Fig.1) this would be valid.

Population trends calculated for this species by the British Trust for Ornithology (BTO) suggest a drastic long-term population decline of 89% between 1970-2005. Of great concern is the short-term trend, again derived from BTO sources, of 39% between 1994-2006 (RSPB 2007). These trends highlight the continuing decline of Corn Buntings on UK farmland, despite the species being in the UK Biodiversity Action Plan (BAP) to reverse the declines of lowland farmland birds.

Consistency of methodology is the key to making accurate comparative studies between two sets of data. Therefore, the same survey techniques were employed as in 2007, with territory mapping using song registrations of male Corn Buntings to assign territory. Simultaneous song registrations would again be the strongest evidence of individual territories. I recorded the songpost type and its location as this would aid my recognition of individual territories on each visit and would prove to be a valuable tool when assigning territories.

All other Corn Bunting activities were also recorded on a simple map of the study area according to BTO Common Bird Census (CBC) protocol. The methodology requires five visits for a single target species (Bibby et.al) made during the breeding season. The route taken in both years is shown in Fig.1.

Duplicating last year’s recording visits, four territory mapping sessions were carried out between 7 and 11 am in the morning during the peak period of bird activity and were of 2-2½ hours duration. One evening visit was made commensurate with last breeding seasons study (see Table 1). Each visit consisted of a walk around the study site following the same route taken in 2007 which gave good audio and visual acuity, ensuring all areas of the study site were covered. The open nature of the fields alongside the farmtracks allowed an adequate field of view to pinpoint the source of any song registrations with the aid of a good quality pair of 8x42 binoculars. This was proven last year by the registration of the singing male on Glenmore Farm at a distance of approximately 300m (Davies 2007). Windy, wet weather was avoided, as this reduces bird activity.

 Table 1.The dates and times of the recording visits

All territory mapping visits were to be made during the peak period of breeding activity between the end of May and the middle of August. This may seem to contradict CBC methodology which advises that territory mapping should be completed no later than the middle of July (Bibby et.al 2000). The methodology has to be tweeked slightly owing to the breeding biology of Corn Buntings. They nest late in the season and are known to be double or treble brooded(Harrison 1975), with young still in the nest as late as September.

I have dispensed with a description of the species in this article and advise the reader to look up my article in No. 23 of Worcestershire Record (Davies 2007) or Mullarney et.al (1999) should you need to know what a Corn Bunting looks and sounds like!

The data from all five mapping visits were transferred onto a master copy for analysis. Each Corn Bunting song activity was designated a visit letter: A, B, C, D, or E. Once transfer of data was completed, clusters of registrations were used to assign territories according to CBC conventions (Bibby et.al 2000).See Fig.2.

Clusters of registrations suggest that there were a minimum of seven male Corn Buntings holding territory in the study area, with the single registration near Hopney Cottages making a tentative eighth

A variety of songpost types selected by males were noted; telegraph wires, isolated trees, hedgerows, hedgerow trees, concrete fence posts and wooden stumps.

The majority of song registrations were recorded from areas where the principal habitat components were wheat, barley, hedgerows and field margins. Brown & Grice (2005) consider wheat and barley to be the optimal crop types for nesting Corn Buntings in the U.K. Comparison of territories in relation to crop types can be made between the two years of the study by comparing the summary of territories (see Fig.2) and crop map (see Fig.3) for 2008 with their counterparts from 2007 (see Figs. 4&5).

I will reiterate the criteria to apply when assigning territoriality.

1. The incidence of simultaneous registrations (on visit B simultaneous registrations were recorded of two and four males respectively, giving a total of 6).
2. Those birds that were of sufficient distance from other singing males as to be considered holding separate territory.
3. The use of a particular songpost on more than one occasion.
4. The consistency of the route taken on each survey visit.

It would appear that there has been a decline of one Corn Bunting territory in 2008. One less male may seem small beer, but when you consider that this is a Red-listed species of conservation concern (RSPB 2007), and when the results compared with those of 2007  an 11% decline is shown we must be very concerned indeed. No comprehensive mapping study of the site for Corn Buntings has been carried out before the 2007 study other than a representative from the RSPB taking a walk around Wick Grange Farm some years ago, and reported four males singing. On a cautious note I would say that numbers have increased since the RSPB visit due to the planting of wildflower field margins on Wick Grange Farm which provide nest sites and the vital resource of plentiful invertebrates for provisioning nestlings. The Recorders field visit in June 2007(Worcestershire Record 2007) produced an extensive list of grassland Lepidoptera from the wildflower margins, and from my own observations over the past two years Lycaniidae and Satyridae butterflies are present in large numbers.

Rob Kings at Glenmore Farm has entered the Countryside Stewardship Scheme and has created beetle banks. Rob also intends to leave field margins to improve the farmland habitat for the species. With game crop present in some of his fields, an additional resource benefits farmland granivores during winter enhancing overwinter survival. This is good news for Corn Buntings given their small population size and their sedentary behaviour. Donald (2002) gives a mean natal dispersal of just 2.4km from an albeit small sample of recovered UK ringed birds, therefore it is vital to expand these isolated islands of optimal habitat to prevent the disappearance of this species so that they do not follow the depressing trend found throughout the U.K and Ireland.

As I have completed my second breeding season study of Corn Buntings at these farm sites, I am pleased to report the continuing presence of “the fat bird of the barley”. It is difficult for somebody born in the 1960s, such as myself, to comprehend the scale of the decline of Corn Buntings, a species once considered a farmland pest (Shrubb 2003). The most similar decline that I have physically been aware of is that of Tree Sparrow Passer montanus (long-term trend 1970-2005 decline of 93%/short-term trend 1994-2006 decline of 97%(RSPB 2007)) once a ubiquitous bird of farmland habitats in Worcestershire and suffering a more disastrous population crash than the subject of this study. It’s not all doom and gloom: if Corn Buntings keep a toehold in this part of the county there is always the chance of a recovery, thanks to the sympathetic farming practices going on. I look forward to recording Corn Buntings again in 2009.

I would like to thank Tom Meikle and Rob Kings for allowing me to carry out this study on their farms, and for their keen interest in farmland birds.