River Thame Bird Atlas 2016-2020

by Nick Marriner (RTCT Trustee)

The River Thame flows for c.40 miles from its source North East of Aylesbury to Thame across into Oxfordshire until it meets the Thames at Dorchester. Its wider catchment covers 682km² bordered by the Chiltern escarpment to the south, Oxford to the east – a large area for a small organisation.

To help better understand some of the wildlife using the catchment, I set off with an ambition to produce a Bird Atlas to help the Trust answer some headline questions:

  • What bird species use the catchment to overwinter and/or breed?
  • Which areas have greatest range of bird species?
  • Which areas have the highest species density?
  • Where are the most important bird habitats?
  • What has changed in last 10 years since 2007-11 British Trust for Ornithology (BTO) Bird Atlas?
  • Does the catchment host any bird species of conservation priority?

With the fantastic support of the BTO, my son Luke and I spend 2 days mapping the catchment and setting up the 238 2km Tetrads that the catchment covers. We also set up a new Bird Track https://www.bto.org/our-science/projects/birdtrack account to host and store all of the data.

The plan was to replicate the methodology of the BTO 2007-11 Atlas Timed Tetrad Counts (2 visits to each Tetrad in the winter between November/February and 2 in the spring between April/July).

Not knowing quite how far I would get with this, and how many people would be interested in volunteering to cover a Tetrad or two, I set off in November 2016 with the support of 45 volunteers and we covered over 25% of the Tetrads in year 1. I have been bowled over with the support offered from local birders ever since.

In total 65 volunteers have been involved over the life of the project; we have had the ‘Beast from the East’, many more named storms, extreme flooding, heatwaves and the odd global pandemic to cope with. Despite all of this we managed to complete 946 survey visits and achieve 99% coverage of the catchment – an amazing achievement and I cannot thank everyone enough for their energy and enthusiasm.

Completed Tetrad coverage

Thanks also to the British Trust for Ornithology for their advice and help in setting the survey up and for helping adapt BirdTrack to enter and store our data.

The last visit was completed on the 30th July 2020 and with all of the data now in we have recorded 153 species and generated just shy of 28,000 records which gives a fantastic data set to work with.

Some rough calculations on the back of this show that collectively the team of volunteers has walked c.4,750km and been birdwatching for over c.3,000 hours! The data has also been shared with our two Environmental Records Centres (BMERC https://www.bucksmkerc.org.uk/ and TVERC https://www.tverc.org/cms/ ) and with BTO nationally.

Some basic analysis of the species records in the Tetrads shows our average number of species per Tetrad came in at 47, which is a very healthy number. As would be expected there is a wide range of species per Tetrad ranging from 84 to c. 30 with a strong showing in the 40/50 range.

It’s amazing to see how common both Red Kite and Buzzard are across the catchment, and great to see healthy distribution of farmland birds such as Yellowhammer and Linnet; local rarities such as Crossbill, Firecrest and Quail; winter roosts and a breeding population of Long-eared Owl, as well as well as one off records of birds such as Hawfinch, Pied Flycatcher and Waxwing.

Over the 4 years of surveying, we have been able to use data gathered to support several practical projects on the ground, which is even more exciting. These projects include securing 2 new Local Wildlife Site designations, at Waterstock and Ickford; delivering new wetland scrapes and fish pass habitat creation; supporting the fantastic new wetland project at Eythrope; helping to inform and design other wetland projects and engage many more landowners, including 2 new Farmer Clusters.

New scrapes at Waterstock

New scrape at Eythrope

The Atlas has further cemented our understanding of the locations of our key areas for wetland birds. The stretch of river and floodplain between Aylesbury Sewage Treatment Works (STW) and Eythrope, and the area from Shabbington to Waterstock, are emerging as the 2 key landscape-scale areas for birdlife in the catchment. In addition, the work has cemented our understanding or our local breeding Curlew, which along with a cluster on the River Ray, is the only breeding Curlew populations in Bucks. On the back of this the Trust is now a key member of the new Upper Thames Wader Group.

We are currently putting together a funding package to pay for analysis and mapping of the data, to create an atlas of these results that is accessible to all. We should have this completed by late 2021, when we hope it will be available as a download from the RTCT website.

The 4 years have flown by and it has been great fun working with all the volunteers to build the picture bird by bird, visit by visit, and Tetrad by Tetrad. The River Thame does not feature on many Bucks birders site lists of ‘go to’ places, but the Atlas has proved that its an under-watched area. The birds are out there if you go looking off the beaten track, which the volunteer bird team have demonstrated brilliantly.

Many thanks to everyone who have helped with the project from setting it up to carrying out the fieldwork, its much appreciated and has made a massive difference.