ecology

Woodland birds threatened by high deer numbers

New research from a team at the University of Nottingham has found that high populations of deer in UK woodlands are having a negative impact on woodland birds.

Dr Markus Eichhorn studied the factors behind the decline in species such as nightingale, marsh tit, willow tit and lesser-spotted woodpecker.

Breeding populations of these birds have suffered severe declines over the last 25 years, whilst the number of deer has doubled. The absence of large predators, such as wolf, lynx and bear, and reduction in hunting, are some of the reasons for deer population expansion.

Although deer do play a part in the health of woodland ecosystems, over-browsing can also have a negative effect. The researchers used laser technology to build 3D maps of woodlands. Comparing 40 woodland areas in England, the team found in areas of dense deer populations there was 68% less foliage near the ground compared with areas with fewer deer.

Dr Eichhorn suggests that if we want to encourage more woodland birds, then we need to take action to restore the woodland structures that they require. Replacing farmed venison with wild meat is one way that deer populations could be controlled.

This research was published in the Journal of Applied EcologyMore about this fascinating paper can be seen here.

Citation: Eichhorn, M. P., Ryding, J., Smith, M. J., Gill, R. M. A., Siriwardena, G. M. and Fuller, R. J. (2017), Effects of deer on woodland structure revealed through terrestrial laser scanning. J Appl Ecol. doi:10.1111/1365-2664.12902

Corvid Population Ecology Research Update

An update from Lucy Capstick, PhD researcher at the University of Exeter, on SBS’s corvid population ecology research study.

My PhD project (funded jointly by SongBird Survival and the University of Exeter, in collaboration with the Game and Wildlife Conservation Trust), investigating how variation in the ecology and behaviour of Magpies affects their impact on songbirds, is nearing completion. The final season of field work has just finished and over autumn and winter of this year the collected data will be analysed and consolidated.

This project has examined whether individual Magpies differ in the extent to which they predate songbird nests, particularly exploring potential differences between territorial and non-territorial birds. To this end the Magpie and songbird populations of a small mixed farm in Warwickshire have been observed and monitored through spring and summer for the past three years. The continuous use of the same site, a farm with management typical of much of the UK’s rural landscape, has allowed the development of a more detailed picture of the population ecology of both the Magpies and the songbirds. It has also made it possible to investigate variation between years, for example whether differences in weather conditions influence songbird nest success or Magpie food preferences.

magpie

In 2016, as in previous years, songbird nests were located in hedgerows on the field site and monitored in order to assess Magpie impact on the songbird population. However, experience gained in the past two years meant that in 2016 a larger sample of approximately 80 nests was found, and in 50 of these, the outcome (success/failure) was known. The nests found largely belonged to more common species, almost three quarters of nests were Blackbird, Dunnock and Wren, however Goldfinch, Yellowhammer and Whitethroat nests were also located. As well as finding individual nests the territories of songbirds were also identified by mapping singing males early in the season. This information will be related to our knowledge of the Magpie population to see if, for example, the presence of a Magpie territory affects songbird territory location and nest success.

Our understanding of the Magpie population has been developed using a number of techniques over the course of the project. In 2016, Magpies were trapped across the site using Larsen traps for the third consecutive year. Trapped birds were colour ringed so they were individually identifiable. In 2015 the rings were more successfully attached than in 2014, so there was less overwinter loss between 2015 and 2016 than the previous year. Of the 75 occasions Magpies were trapped in 2016, new birds were caught only 10 times, while on the other 65 occasions previously ringed birds were re-trapped. The trapping process was slightly less successful than in 2015 and camera observations of the traps suggested there were a number of occasions of previously trapped individuals returning to traps and, perhaps unsurprisingly, avoiding tripping the mechanism again. Nonetheless, this trapping programme alongside direct observation of individuals and early season identification of magpie nest sites meant it was possible to work out where active Magpie nests were.

As well as looking at how the Magpie population as a whole may relate to songbird nest success, this project also aimed to investigate how individual Magpies differ in their impact on songbirds, for example, are some individuals more likely to predate nests in their territories than others? This year variation in individual Magpie defence behaviour was investigated, largely through work carried out by a Master’s student from Newcastle University (Rebecca Liberty). A dummy Magpie was placed near active nests and the response of the territory holder, which ranged from mobbing the dummy to ignoring it, was recorded. This variation in response, alongside other information such as differences in trappability, may indicate differences in aggression between individuals which could be linked to predation behaviour.

6 - Predated nest

A predated nest. Photo: Lucy Capstick

Another way of examining possible difference in an individual’s predation behaviour is to use artificial nests. This is a recognised technique used to gain an understanding of the pattern of nest predation and the identity of nest predators without disturbing natural nests. Both old songbird nests and manmade nests were baited with real and wax-filled quail’s eggs and monitored by trail cameras (motion activated cameras). A predator attacking a wax egg will leave an imprint, such as a beak or bite mark, and can therefore be identified. The nests were set out in transects in areas with occupied Magpie nests and in areas where it was believed Magpie presence was reduced. This method was piloted in 2015 and used more extensively this year. Over the course of the spring and summer over 400 artificial nests were placed across the field site. It will therefore be possible to look at the impact of Magpie presence on predation, but also at differences between the territories of individual Magpies, and the effect of time of year, for example, is predation higher when Magpies have young in the nest? Preliminary analysis suggests Magpie predation is higher in certain locations and trail camera pictures also identified specific ringed Magpies predating multiple nests. This may indicate that certain individuals predate more.

Over the three years of this PhD project a range of field data, including that detailed above, has been collected. The task now is to look at the information about Magpie population ecology, habitat use and territorial behaviour in combination with that about the songbird breeding population to see if and how they interact. The project will collate information about Magpie distribution, movement and breeding at a wider landscape scale. At a finer scale individual differences between Magpies in terms of territory location and habitat, and behaviour will be examined. Predation of both real songbird nests and artificial nests will be looked at with relation to the Magpie population. As well as this field data, research of the scientific literature will help to build up a more general understanding of corvid predation of songbird nests, as it could be that some species are more vulnerable to predation by corvids or that their populations are less able to recover from breeding season losses. In general this type of research into the population ecology of predators and their prey species, and how they interact, may suggest a way to manage the UK’s countryside to benefit the prey species, such as threatened songbirds.

Hugh’s research paper published

The latest paper from SongBird Survival’s Keith Duckworth project has recently been published in Ibis.

PhD student Hugh Hanmer has been studying urban bird ecology and conservation with Professor Mark Fellowes and Dr Rebecca Thomas at the University of Reading. The primary focus of his PhD has been on the indirect effects of garden bird feeding, though other work has taken in nest boxes and domestic cat ranging across the urbanisation gradient.

Hugh’s recent paper investigates whether feeding birds increases local nest predation. Using the university’s suburban parkland campus as a study site, Hugh replicated a typical suburban garden. He set up artificial nests, containing quail eggs, either 5 or 10 meters away from feeding stations. A variety of feeder types were used (guarded/unguarded, peanut-filled/empty), and both the nests and feeding stations were monitored with camera traps to see which species visited them.

Hugh found that Eurasian magpies and grey squirrels were frequent visitors to unguarded feeders, and this resulted in a five-fold increase in predation rates of nests that were set up near these feeders. Eurasian jays also predated these nests, although they did not visit the feeders.

-parakeets-and-squirre

The researchers suggest that magpies and grey squirrels are attracted to the food, and then forage locally, increasing the chances of finding local nests, and that the Jays respond to the presence of the other species, rather than the presence of the food itself.

Irrespective of the behavioural underpinning, the result of providing food was increased nest predation.

Wildlife gardening is hugely popular in the UK, and we spend £200 million on bird food every year. But we need to ensure that we are doing the right thing for wildlife.

Hugh’s research has important implications for how we feed the birds in our gardens, to make sure we are benefiting song and other small bird populations.

Hugh suggests that feeders are placed as far away as possible from potential nests sites during the key nesting period in late spring. It’s also important to offer food which is less attractive to nest predators and more suitable for the birds we want to support. Finally, he advocates the use of feeder guards, even though this didn’t reduce predation. This is simply because the use of guards means that more food goes to the target beneficiaries, rather than helping grow local populations of squirrels and magpies!

For more information on how to benefit songbirds in your garden, visit the SongBird Survival website. To view Hugh’s full research paper, click here.

 

 

Saving Our Dawn Chorus

What is behind the continuing decline of our songbirds today? What are the underlying reasons and what potential solutions should be investigated?

SongBird Survival is committed to finding out the answers to these questions through commissioning quality scientific research into the issue.

In 2016, we produced a short film, presented by ecologist Katy Thomas, introducing SongBird Survival and looking at where the UK’s famous dawn chorus is heading.

Since the 1970s, populations of songbirds in the UK have crashed, and our dawn chorus is far less rich and diverse than it was in our parents’ and grandparents’ day.

Yellowhammer populations have declined by 55%, cornbunting numbers are down by 87%, whilst tree sparrows have suffered a rapid decline of 95%. These figures are shocking, but what is causing our small birds populations to crash? Loss of habitat? Predation? Intensification of farming?

SongBird Survival believes that research is the key to understanding why.

We fund high quality scientific research to investigate the drivers behind these population declines and promote evidence-based solutions to restore songbird numbers.

With your support we hope to draw attention to the plight of our song and other small birds. Your membership and donations help to fund our research programme and add weight to our work with other organisations. Together, we can save our songbirds before it’s too late.

To find out more about our research and objectives, watch our YouTube video.

SBS YouTube (2)

We partner with like-minded organisations to commission targeted research into areas where scientific evidence is currently sparse, inadequate or lacking.

To date we have partnered with the University of Exeter, the University of Reading, the Game & Wildlife Conservation Trust, and the University of St Andrews, in projects which examine the potential causes behind songbird population decline. Such research produces high-quality, peer-reviewed research papers, contributing to ornithological and ecological knowledge in the UK.

We have exciting future projects in the pipeline, and will be bringing you news of this very soon. In the mean time, further information about our current and past research programmes can be seen on our website.

SongBird Survival: Saving Songbirds With Science