Planning a four month long project with field work seems a little tricky...

Following on from the three ideas I had last week, I finally decided upon the idea which focusses on how urban noise influences parent-offspring communication. So I met up with Jenny again to discuss how it could be done...

Developing the Urban Noise and Parent-Offspring Communication idea

There is quite a bit in the literature about how urban noise and parent-offspring communication are related, with many studies looking at how urban noise influences chick begging calls and nestling success through observational (observing changes in breeding success along natural noise gradients) and experimental (manipulating noise levels at different nest boxes) studies. So what could I study...?

Noisy nests on fledgling calls?
One avenue I could consider is how a noisy nest would influence parent-offspring communication in the fledgling period. Communication is really important because fledglings are very vulnerable at this stage and still dependent on their parents for food. Moderate levels of noise in the nest could affect call development, as well as auditory development. It has also been suggested that perhaps changes to call structure (to avoid masking by urban noise in the nest) might have positive effects on signal transmission later in life, including the fledgling period (Leonard & Horn, 2008, Behavioural Ecology). But the reason this has not been done yet in the literature is because it is so tricky to carry out. Fledglings have a low survival rate (which means I would need to find a large number of nestlings to start off!) and they spread out over much greater area (than nestlings!), but working out how to record and measure the fledgling calls to their parents is probably the biggest challenge here!

I'm used to noisy streams, so I'll be fine in noisy urban areas?

Another avenue I could look into would be to see if birds that live in natural noisy environments (e.g. by streams) cope better with noise than those who live in quiet havens. Some birds who live by these natural noisy environments have changed some of their signal features, such as using more pure tones in the American dipper - which would reduce the effect of masking (Warren et al., 2005, Animal Behaviour). Also, I could look into whether birds in noisy urban environments cope with noise better than those is quiet rural environments.

After a bit more thinking, I got an idea of splitting my project into two:

Using BTO Nest Record Scheme and Noise Maps
In the UK, we are very fortunate in having so many passionate volunteers participating in bird surveying schemes, which allow us to understand changes in bird behaviour with changes in the environment at a national scale. One of the schemes by the British Trust for Ornithology, the Nest Record Scheme, consists of volunteers finding nests and documenting details of location, habitat and the nesting attempt over the breeding season. These data are vital for research as well as monitoring bird populations over time, allowing conservation concerns to be identified and addressed efficiently.

In accordance with Environmental Noise Directive (2002), DEFRA (Department for Environment, Food and Rural Affairs) conducted strategic noise mapping across England. Thus using these two datasets, I could investigate if the effects described in experimental studies can actually be detected across the national dataset. I could locate areas where noise and breeding success were likely to be related and identify the associated noise characteristics - amplitude, frequency etc.

Experimental manipulation 

Conducting an experimental manipulation, using the noise characteristics that have been found to have an effect from the above analysis, would allow me to test more explicitly whether or not it is indeed these noise characteristics that are resulting in the observed reduced breeding success, or whether it was some other environmental factor that covaried with these locations. This approach allows me to identify ecologically relevant noise characteristics (as there is no point in increasing noise levels indefinitely in experiments if they never occur in the real world) and then understand the biologically relevant relationship between these noise characteristics and breeding success - providing evidence for conservation action. 

But in order to do this experimental manipulation, I would need a licence to disturb breeding birds from Natural England, in accordance with the Wildlife and Countryside Act 1981, on which there is approximately a waiting time of 12 weeks (which would take me to at least early May - when the breeding season would have already started...). So whilst it is very exciting, the licence is very unlikely to come through in time. However, as both parts of the project could be stand-alone projects by themselves, I could still investigate the relationship between breeding success and urban noise - studying just the first part using Nest Record data and Noise Maps, being purely data analysis. But still fantastically cool!

Drivers of changes in mute swan populations

Before I left the meeting though, Jenny suggested that there might be another project I would be interested in, which would looking at mute swan populations and understanding the drivers behind their population change in recent years. In 1987, there was a ban on the use of lead fishing weights and since then, the population has at least doubled across Britain (Wood et al., 2019, Biological Conservation). It was thus suggested that this increase in population was due to this ban. However, as there are many other environmental variables (and because this is biology), it is unlikely ever to be this simple. So I would be working with amazing minds, Prof. Rhys Green and Dr Debbie Pain, in Cambridge, as well as Jenny, to disentangle this intriguing issue.

A pair of mute swans at the UEA Lake last night

On a related note, this project emphasises the importance of testing the effectiveness of regulation and conservation interventions. There is a real paucity of studies in the field looking at this and this means that downstream it will be very hard to justify the persistence of these actions. Whilst it can be suggested from inference that the mute swan population have increased due to the ban, there is little quantitative evidence (apart from Wood et al., 2019) evaluating this. There could be other factors leading to the increase and our ignorance of this could potentially be very costly for the populations we are supposedly trying to protect with our policies and legislations. Here, I must highlight the importance of Prof. Bill Sutherland and his teams' work (https://www.conservationevidence.com) trying to evaluate evidence behind conservation interventions to promote those that are most effective.

What next?
So very much like last week, I need to make my mind up between the two fantastic projects and then actually begin planning my work on them!