Garden CESs and Barn Owl Ringing in 2020

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As many Constant Effort Sites (CESs) couldn’t be operated in 2020 due to Covid-19, the British Trust for Ornithology (BTO) decided to pilot a garden Constant Effort Site (CES) scheme in 2020. Two members of Gower Ringing Group took part, Heather Coats and Cedwyn Davies, whose gardens are located in Crynant (Dulais Valley) and Briton Ferry.

This initiative reflects the fact that we know relatively little information about productivity and survival in garden bird populations in comparison with their rural counterparts. Much of this detailed information on common song birds of the wider countryside, including population trends, productivity and survival rates has been established through the ‘traditional’ CES network (of over 140 sites UK-wide). It was therefore a logical step to adapt CES methods for use in gardens.

CESs require nets to be set in standard positions and operated at least once during each of twelve 10 or 11-day periods across the summer. The garden CES protocol was adapted as follows:

  • Participants were allowed to artificially feed birds (on the proviso that food was kept constant).
  • There was no lower limit on predicted capture numbers (a minimum of 200 birds applies to the standard CES scheme).
  • There was no requirement to operate sites for more than a year (this is strongly encouraged for standard CES sites)

Participants were invited to complete 12 Garden CES sessions between 30 April and 2 September 2020.

Crynant Garden CES Results

Heather completed 11 of the 12 sessions, capturing 321 birds of 15 species. A breakdown is as follows:

She noted, “It was interesting to catch a juvenile blackcap since, although they breed nearby, none has been recorded in the garden. The number of blue tits was larger than expected even though they are a frequent visitor to the feeders. In general one would expect larger numbers of juveniles than adults in the summer which was not the case with siskins. This species breeds in Scots pine trees behind the garden and also in nearby forestry.” When restrictions on travel allowed, Heather was assisted by Dionne Jenkins, Alex McCubbin and Bethan Dalton, always  with strict social distancing in place.

Briton Ferry CES Results

Cedwyn adapted his usual ‘garden ringing’ set-up of a single 12-metre net, through adding a 9-metre net in front of the feeders and a 6-metre net parallel to a boundary hedge and away from the feeders for the purposes of his garden CES.

He also managed to complete 11 of the 12 sessions, capturing 344 birds of 18 species. A breakdown is as follows:

The more noteworthy captures were a whitethroat in the final CES, a female Bullfinch in CES 3 (“a species only seen when the apple blossom is on the trees“) and an adult male goldcrest in CES 10 (“having lived here for thirty-seven years this is the first time I have seen this species in the garden”).

Garden CES Conclusions

Both gardens resulted in good numbers of birds being captured, and both also produced some unexpected species.  We will await with interest how the BTO analyses the data and what it concludes with regard to the overall success of the scheme in Year 1.

Swansea, Gower and Neath Port Talbot Barn Owls

Cedwyn also runs an annual programme of barn owl monitoring taking in many sites in Swansea, Gower and Neath Port Talbot (NPT).

He reports that the initial period of ‘Lockdown’ restrictions had an adverse effect on barn owl box monitoring. In NPT monitoring did not commence until July, by which time a number of young birds had fledged and were flying strongly around the farm buildings at a number of sites. Cedywn notes however, “We managed to ring eleven birds at four farm sites in NPT and seven at three sites in the Swansea area,” so not such a bad year for this project overall.

Heather Coats & Cedwyn Davies


One of the birds ringed in 2020 (Cedwyn Davies)
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