Derek Gruar introduces the 2019 report from the bird ringing and monitoring that takes place at Paxton Pits

The British Trust for Ornithology (BTO) has used Constant Effort Site (CES) bird ringing to monitor the abundance, breeding success and survival of 24 common breeding songbirds since 1986. Paxton Pits Nature Reserve is one of over 140 sites across the UK that contributes data to this programme.

Monitoring is carried out by qualified volunteer bird ringers during the breeding season, with twelve visits between May and early September where the same nets are set for same standard length of time for each visit. At Paxton, we monitor the site with eight mist-nets totalling 140 metres in length that are set between 5.30-11.30am. 

The results are used to measure changing population sizes (comparing the number of adult birds caught each year) whilst the ratio of juvenile to adult captures provides a measure of breeding success. In addition to ringing new birds we also record data for all birds we recapture; those of adult birds ringed in previous years are used to estimate annual survival rates. 

Some birds ringed in 2019. L-R House Sparrow, Bullfinch, Reed Warbler.


In 2019, we conducted 15 bird ringing sessions at “The Sanctuary” at Paxton Pits Nature Reserve. The first session was in early January and our standard CES monitoring began in May and continued until late August. 2019 proved to be another improvement on the previous two CES seasons. Post CES we managed to successfully target late summer migrants on three visits in September. The final session of the year was a demonstration event where visitors from the Friends of Paxton group were invited join us during the ringing session. Sadly, the poor weather in autumn prevented any further visits.

Over the year, mild winter conditions were replaced with cold and wet weather in late spring. We were fortunate that conditions had improved by the time the start of the 2019 CES ringing season was due. Fine and dry weather in May enabled resident species to raise broods with Blue Tits, Long-tailed Tits and Robins making up the most of the early season catches. June however was quite wet which seemed to affect breeding warbler numbers, especially Blackcaps which were surprisingly absent. The record warmth of July seemed to suit Phylloscopus warblers with a record combined catch of Willow Warbler and Chiffchaff on 21st July. Late summer saw an increase in thunderstorms and in August numbers of birds ringed were steady rather than spectacular. The highlight was the number of fledged Bullfinches. 

Overall, we succeeded in conducting ringing sessions on eleven of the twelve allocated time periods. A total of 346 new birds were ringed of 23 different species. This was a further improvement on 2018 as bird populations at Paxton seem to be recovering after the poor year in 2017. An average of 34 new birds ringed per visit is just above the 10 year mean.

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