WOS Student Research Award 2021 winner – Luke Beckett for ‘Long-term population recovery of Dippers Cinclus cinclus in urban South Wales in relation to river quality and prey use.’

Luke Beckett’s submission: Globally recognised research from Wales has revealed how White-throated Dippers indicate the quality of river ecosystems through natural and anthropogenic effects on their distribution, abundance and life history. Obligate links to river production – specifically aquatic macroinvertebrates and small fish – have led to three bioindicator routes, specifically:  i) impaired prey availability (eg acidification); ii) bioaccumulation and biomagnification (eg PCBs, organochlorine pesticides, flame retardants); iii) passive trophic transfer (eg microplastics) (Ormerod et al. 1991; Morrissey et al. 2013; D’Souza et al. 2020).  So far, however, there has been no exploration of the capacity of Dippers to indicate improving water quality – such as the recovery of British rivers from gross organic pollution since the 1980s/90s (Vaughan & Ormerod 2012). BTO Atlas suggest that such recovery has occurred among Dippers along Britian’s urban rivers, but the processes are poorly understood.

The rivers of South Wales exemplify recovery from gross pollution and BTO Atlas data suggest that dippers have recolonised this region. To understand the processes involved, this study quantified  i) long-term trends in water quality using harmonised monitoring data; ii) prey available to Dippers in the S Wales valleys using benthic sampling and iii) Dipper diet using faecal analysis.  Given that important Dipper prey include pollution-sensitive mayfly nymphs and caddis larvae, it was hypothesised that recovery from gross pollution should lead to these taxa forming major components of prey use and availability.   

BTO Atlas data confirmed that Dipper occupancy in 10 x 10 km grid squares in Glamorgan expanded by 42% between 1968/71 and 2008/11 so that the species now occupies most suitable rivers throughout the region. Moreover, all the rivers analysed showed chemical trends consistent with recovery from gross pollution such as significantly increased dissolved oxygen (4/4 rivers) alongside significant decline in orthophosphate (4/4), nitrate (3/4) and Biochemical Oxygen Demand (2/4 rivers).Kick-sampling at 15 sites revealed over 27 taxonomic families throughout the Taff, Afan, Ogmore, Ely and Rhymney, where diverse macroinvertebrate communities now consist of clean-water mayflies, stoneflies, caddis larvae and fish such as bullheads (Cottus gobio).  Dietary analysis showed that over half of the biomass ingested by adult Dippers along these rivers comprised baetid and heptageniid mayflies, leuctrid/nemourid stoneflies and rhyacophilid or hydropsychid caddis larvae. Over 60% of the biomass in nestling diet came from limnephilid, rhyacophilid or hydropsychid caddis.

These data show how prey availability and prey use in Dippers along the S Wales valleys now match patterns in clean-water hill-streams, implying that invertebrate recovery has facilitated Dipper recolonisation. The study also implies that regulation, improved wastewater treatment and industrial contraction have aided the chemical recovery of rivers in South Wales with conservation benefit. While further studies should assess responses to emerging problems such as Combined Sewer Overflows and microplastics, these findings contribute to the understanding how Dippers respond to river restoration thereby adding an important dimension to their role as environmental indicators.

About 23-years old Luke.

Growing up in rural Shropshire meant I have always loved the outdoors and been fascinated by the natural world. As a youngster, I would find kingfishers and otters on the River Severn, enjoy views of barn owls from my window and record mammals, such as pole cat and fallow deer, on camera traps in nearby woodlands. This keen interest led to me reading Biological Sciences at Durham University, where I focused on ecology and wildlife conservation in my final year. Seeking a more applied understanding and skillset, I then undertook an MSc in Global Ecology and Conservation at Cardiff University.

Birds have always been a passion of mine and I wanted to dedicate my MSc research project to our avifauna. Therefore, I jumped at the opportunity when dipper expert Prof. Steve Ormerod put forward a project about a long-term population recovery and conservation success story of this charismatic bird. I have learned so much throughout the study and after long days in the field and painstaking faecal analysis in the laboratory, I’m just delighted to contribute additional knowledge on this iconic species.

Luke Beckett
Kick-sampling
Kick-sampling
Young Dipper (photo by Colin Baker)
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