Amelia Page

Lancaster Environment Centre (Bailrigg) | Year 3 | Degree: Ecology & Conservation

Is dipper phenology affected by climate

Climate change has led to altered phenology in passerine birds. The aim of this study is to see if a Cumbrian population of white-throated dippers (Cinclus cinclus) has been affected by changes in temperature and river flow caused by rainfall extremes. Resources used included long-term data sets of the dipper population, temperatures and river flow. Non-parametric statistical tests were used such as Kruskal-Wallis tests and Spearman’s Rank. A Dynamic Harmonic Regression model was created and a phase shift calculated for the temperature changes. The dipper population declined significantly and the first laying date advanced eight days between the two periods of study. However, there were limited links found between the population changes and the climatic variables. Some associations were found but were not statistically significant. It was found that the phenology of this dipper population was unlikely to have been significantly affected by the changes in climate. Reasons for this include weaknesses in the data and analysis, or that the dippers have begun adapting to changing climatic conditions.

Amelia Page

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Amelia Page

Lancaster Environment Centre (Bailrigg) | Year 3 | Degree: Ecology & Conservation

Is dipper phenology affected by climate

Choosing My Project: My favourite things to learn about in my degree have been animals, their populations, and behaviour. Thus, I wanted to complete a dissertation involving an animal population. My advisor, Dr Wlodek Tych, specialises in time series and long term data sets. I was inspired to see how an animal population had changed over time in relation to climate change. Dr Stuart Sharp provided the data on a dipper population he has studied. Dippers are a family of unique birds - the only aquatic songbirds.

Literature Review: In my research, I found multiple papers written about Norwegian dipper populations. These showed interesting results - milder winters were associated with increased breeding behaviours and population growth. Warmer temperatures reduced ice formation, making conditions more favourable for the birds. However, increased river flows directly affected their habitats and low-lying nests. Hydrological extremes affected the availability of macroinvertebrate prey, reduing their reproductive performance. These studies predicted that changing climate and environmental extremes could have disastrous effects on dipper populations. Globally, dipper populations are declining. However, the Norwegian studies contradict this, as the populations generally benefitted from the warming temperatures. Could Norway be an anomaly, or would the UK follow a similar pattern?

My Data: Dr Stuart Sharp provided the dipper data from his long-term data set based near the village of Sedbergh, Cumbria, in the Yorkshire Dales National Park. This dipper population had been studied in two periods: from the years of 1958 to 1966, and then again from 2003 onwards. Temperature data was taken from Newton Rigg Historic Weather Station, run by the Meterological Office. Flow data was accessed through the National River Flow Archives. The majority of the flow data came from a site at Killington, but for the older data set a site at Caton was used instead and scaled accordingly. Non-parametric tests used included Kruskal-Wallis, Spearman's Rank, and a Dynamic Harmonic Regression.

Summary of Results: Between the two time periods studied, the dipper population declined significantly, and the breeding dates advanced. This is similar to many other studies on bird phenology. Unexpectedly though, there were no significant differences between climatic conditions and dipper breeding patterns.

Conclusions: Contrary to the hypothesis, climate did not have a significant effect on the dipper population and breeding patterns. This could be due to the small samples of inconsistent data and use of non-parametric tests. Furthermore, evidence of climate change can be hidden by normal weather fluctuations. Alternatively, the lack of any noticeable shift in the dipper's population and behaviours could suggest that the birds have begun adapting to changing climate conditions, preventing them from experiencing negative effects on breeding. Further research could investigate more weather conditions, multiple dipper populations and effects of land use change.

A Dynamic Harmonic Regression of monthly temperatures.

Sedbergh, Cumbria.

Egg laying dates changed significantly between the two study periods.

Brood population against river flow.

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