invasive species

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

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Regional dialects in songbirds

A fascinating citizen science project has successfully mapped the distribution of dialects in yellowhammers (Emberiza citrinella) in both New Zealand and the UK.

Yellowhammers, like us, have regional dialects, with differences in their song depending on the region that they live. A familiar farmland bird in the UK, the species was introduced to New Zealand over 100 years ago, and this has provided researchers with a unique opportunity to investigate two completely isolated populations.

The Yellowhammer Dialects project used citizen science volunteers to record yellowhammer song in the field. This allowed the project to access lots of data from across a very large area, which was then compared with historic recordings from archives. All this information was then used to accurately map the composition and distribution of different dialects in the two countries.

Researchers found an interesting difference in dialect between the populations of yellowhammers, with New Zealand yellowhammers sing nearly twice as many different dialects than yellowhammers in the UK.

They explain this result by suggesting that New Zealand yellowhammers have retained song structures which were originally from the UK, but have subsequently been lost in the mother country, perhaps due to the widespread decline in yellowhammers in the UK.

The yellowhammer dialect system may be the avian equivalent of a phenomenon already noted in human languages, in which ancient words or structures are retained in expatriate communities.

A fascinating finding, and one which will hopefully be complemented by further results in the near future; after the success of this project, the researchers have decided to host sister projects in both Switzerland and Poland.

The full research paper can be found here.