Birds and Trees: Doing Research in SCENE’s woodlands

SCENE has been home to many research projects over the years. While many of these have been short studies focused on individual researchers’ interests, some study systems have provided a wealth of possibilities leading to decades of detailed and diverse research projects. One such system is the blue tit population inhabiting the woodlands around the research station. Masters student Simon Helfer has recently started to investigate breeding success in blue tits to try to find out what drives success in urban and rural breeders. In this month’s Behind the SCENE, Simon writes about the beginnings of his project.

Nest box 1 in the woodlands near SCENE. ©Simon Helfer
Nest box 1 in the woodlands near SCENE. ©Simon Helfer

Birds and Trees: Doing Research in SCENE’s woodlands

Walking through the woods around SCENE, you will almost certainly notice at least a few brown, cylindrical boxes hanging either from tree branches or from hangers fastened to the trees themselves. You may even notice the numbers painted on the front of each of them, and ask yourself, ‘How many of these are there?’ The answer, incidentally, is over five hundred. These nest boxes were first set up in the 1990s for the use of researchers working at SCENE who wished to study birds and bird behaviour. Over the intervening years they have spread out from SCENE, and now can be found stretching to the nearby Cashel Woods and even all the way to Kelvingrove Park in Glasgow’s West End.

The nest boxes have seen a number of experiments since they were first placed, as the woodlands around SCENE offered a chance to study the birds in a largely undisturbed environment. The woods provide a unique and highly valuable resource: they are mostly oak woodland, an environment that used to cover the majority of the British Isles, but has become increasingly rare.

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The facilities at the research station and the ecosystem of the surrounding woods make SCENE the perfect place for a series of experiments headed by Dr Barbara Helm and Dr Davide Dominoni, focusing on the effects of urbanisation on birdlife. This was done by placing nest boxes along an “urban gradient”, starting in the rural setting at SCENE, passing through the University’s Cochno Farm, and ending in Glasgow’s Kelvingrove Park. Institute researchers are looking at how factors such as air-, noise-, and street light-pollution and food availability affects breeding success, egg-laying and hatching times, behaviour, and overall health.

In the last year, two projects investigated the effects of the urban gradient on blue tits (Cyanistes caeruleus), looking specifically at diet, fledgling success — the number of chicks that leave the nest — and gene expression related to the immune system. Both projects found that the numbers of successfully reared chicks in Kelvingrove Park (urban) was dramatically lower compared to the nests up at SCENE (rural), with the birds living in Kelvingrove being over twenty times less successful than their counterparts in the rural setting. The reasons for this are still unknown; it’s possible that this is the result of a bad year, a lack of food availability and bad weather, combined with something about the urban ecosystem that has a detrimental effect on the chicks.

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My own work at SCENE will be following up on these projects, trying to identify the reasons that might be behind the decrease in fledgling success by looking into the available invertebrates and at the foraging behaviour of the adult birds in both the urban and rural environments.

I’ve just recently started the early stages of my fieldwork: monitoring invertebrate populations in the SCENE forests, specifically those living on the branches of oak and birch trees. The technique I’m using for this is known as ‘tree beating’, and involves placing a collecting frame underneath a selected branch and hitting or shaking the branch to dislodge the invertebrates living on them. Any fallen animals are then collected and taken back to the research station for identification. I actually started this process in early February, but have found very little: in my first week I collected four spiders, and since then the branches have been almost bare — not unexpected with the cold, wet, windy weather.

When the breeding season begins in late April, a team of researchers from the University will be monitoring the nest boxes at SCENE, looking for signs of activity. Once we know which boxes will have nests, the bulk of my research can begin. This means that I will be catching parental birds on the nest, and attaching small radio telemetric tags to their backs with the same sort of glue that is used to attach false eyelashes. This particular glue has been used in previous experiments, and has been shown to stick firmly to the bird, but eventually come off, allowing the bird to shed the tag without harm.

Radio-tagged birds can be tracked by a method known as triangulation: two people standing at separate locations will identify the tagged birds using a directional antennae and recording the compass bearing for the strongest signal every 20-30 minutes. By marking our locations using GPS, and using these positions and the signal directions, we can pinpoint the birds’ movements and see how far they are travelling to find food. By monitoring several birds in both habitats, we can then get an idea of the average distance that birds are travelling to forage in each ecosystem.

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The first part of my experiment — collecting invertebrates — should be able to tell me if there is a difference in food availability between rural and urban environments. My hypothesis is that it will be a lot lower in Kelvingrove than at SCENE, and so I’m expecting to see birds travelling much further to search for food for their chicks. This may result in the chicks getting less food throughout the day, which may in turn help to explain the poor fledgling success rate.

Young blue tits are normally fed a diet primarily made up of of caterpillars, but if their parents are struggling to find these in the city, they may be feeding their young on man-made foods (such as fat-balls or seed mixes), which may also be an important factor. I’m interested in conducting research that will have positive impact, and help to inform future research: can man-made food sources affect the health of the bird communities? Is it possible to tailor the foods we leave out to best suit the needs of the birds, especially as those needs change throughout the year?

For now, I’m looking forward to my fieldwork in the SCENE woodlands, collecting invertebrates and tracking foraging parents. Not a bad way to spend a Scottish spring — assuming the weather behaves itself!

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