It's winter and the sun is setting over the waving reeds in front you.

A few small, black dots begin to fly in: Common Starlings.

They're joined by more and more coming from left, right and centre, until thousands of starlings come together as one, and suddenly you're watching a breathtaking murmuration. With so many thousands of birds dancing through the winter sky above you, it's easy to be fooled into thinking the species is doing rather well. Sadly, this couldn't be further from the truth.

The stark facts are that between 1995 and 2016, Britain's breeding population of Common Starling crashed by a staggering 51 per cent. Just let that sink in. It means that there are now only half as many starlings in Britain than when I started watching birds with my dad during the mid-1990s. The situation in England is even worse: we saw an 87 per cent decline between 1967 and 2015. Starlings no longer nest in large parts of Wales and southern England.

Back to that murmuration – many of the starlings you're watching above your head will have travelled here to escape the winter freeze in countries to the north and east. In those places too, numbers are falling, and we're seeing fewer of these birds arriving each year. It means that the large winter gatherings we're used to seeing are becoming smaller. Are the days of starling murmurations numbered?

Starling murmeration

This is where the scientists at the RSPB Centre for Conservation Science come in. We're trying to discover just what is driving starling declines in the UK and find solutions to improve the prospects for one of our best-known birds. The thing is, despite it happening all over the country, no one knows exactly what is causing the decline. 

So what do we know? The latest research combining the most recent British Trust for Ornithology (BTO) survey, nest records and ringing data show that the birds seem to be mostly breeding successfully. I've personally helped scientists and volunteers monitor the breeding colony at Hope Farm RSPB, our arable farm just outside Cambridge, and have seen first-hand that starlings are producing plenty of chicks. This means the problem is occurring away from the species' breeding grounds. And this is the tricky part. Just where are starlings going when they're not breeding? What problems do they face when they get there? There are many lines of enquiry. Could the problem lie with the loss of an important food source, predation, changing agricultural practices, or something else?

Looking at different breeding populations around Europe, some are doing well and increasing, but others, like here in Britain, are declining. Backing up the theory that the problem is away from the breeding grounds, it appears the declining and increasing populations use different wintering grounds.

We have seen that in the first few weeks after fledging, Eurasian Sparrowhawks and cats prey heavily on young Common Starlings. However, once the fledglings have gained some experience of the world, and realise the danger of predators, the losses decrease dramatically. 

Research from other scientists involving laboratory studies shows that pollutants, including anti-depressants (from our sewage systems) and flame retardants, badly affect starlings, but it's less clear whether wild starlings are exposed to them. What all of this research, from the RSPB and from others, shows is that it's likely that the starling's shocking decline is caused by a combination of factors. We just need to find out exactly what.

As we think that the issues are occurring away from species' breeding grounds, we first need to find out where starlings head to once the chicks have fledged and breeding is over. We believe this is key to understanding the decline. This led scientists to pilot a pioneering citizen science project during summer 2018; this was funded by Natural England through its Action for Birds in England programme (AfBiE).

The problem with traditional radio-tracking technology is that it's difficult to follow birds such as starlings that disperse quickly. Indeed, we've struggled to track Common Starlings successfully in previous studies, and it was clear we needed to try something new. For this project, we trialled new tracking equipment that will hopefully improve our success.

 Young starlings are too mobile for researchers to track on their own (colour-ringed birds have been seen 40-50 miles away from where they were originally captured), but this was considered a much more manageable challenge for larger groups of volunteer trackers. The idea was tested by fitting 25 young birds in Bristol with radio tags and then tracking them with portable receiver stations placed in the homes and cars of local volunteers.

There were two aims to this project. Firstly, to shed some light on where the starlings go to after breeding, the habitats they use and the threats they face. Secondly, we wanted to see if a project like this is a viable option to track starlings which could potentially be carried out on a larger scale. Could further expansion of the volunteer network help build a more complete picture of starling behaviour?

So next time you're watching that Common Starling murmuration, as well as being mesmerised by the balletic aerial dance above your head, remember that those birds are in trouble, and scientists are trying hard to find out what's wrong, before it's too late. 

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