WaderTales: a taste of Scotland

What happens when Black-tailed Godwits cannot cross the Atlantic?

Observations from Tiree by John Bowler and others gave a unique insight into what happens if northerly winds set in at migration time. Here is the blog.

ORGOLO

Here are four more uniquely-Scottish WaderTales blogs to read:

scottish-wadertalesEstablishing breeding requirements of Whimbrel  focuses on the different habitat needs of adults and chicks in Shetland.

Oystercatchers: from shingle beach to roof-tops details significant declines in Scotland, at least partly explained by predation. An increasing number have now taken to nesting on roofs.

UK Dotterel numbers have fallen by 57% presents the results of an RSPB survey that was published in Bird Study.

Prickly problems for waders explains how SNH are trying to deal with introduced Hedgehogs in the Outer Hebrides, where they are a major problem for breeding waders.

And here are another six which may well appeal to Scottish birdwatchers:

  • NEWS and Oystercatchers focuses on the waders that  winter on coasts, instead of estuaries. It was written to promote the 205/16 coastal survey run by BTO.
  • A place to roost discusses the importance of safe, high-tide roosts, especially in terms of energetics. What are waders looking for?

There are 40 WaderTales blogs. The intention is to add one or two new blogs each month. You can sign up to receive an e-mail notification when a new one is published.


GFA in IcelandGraham (@grahamfappleton) has studied waders for over 40 years and is currently involved in wader research in the UK and in Iceland.  He was Director of Communications at The British Trust for Ornithology until 2013 and is now a freelance writer and broadcaster.

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Black-tailed Godwits and Volcanic Eruptions

Around 360 earthquakes were detected in Iceland in the week beginning 4 December, which is pretty normal. Earthquakes can give hints about impending volcanic eruptions so they’re important to Icelanders –  and, by implication, to Icelandic waders too.

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In the long term, volcanic ash provides the nutrients that improve fertility, as you can read in How volcanic eruptions help waders, but short-term effects can be seriously negative. This was what Tómas Gunnarsson discovered when he went out to count godwit broods at what should have been the height of the 2011 breeding season. He found only two pairs that showed signs of having broods. Was the Grímsvötn eruption between 21 and 28 May to blame?

Assessing producivity

Iceland hosts internationally important breeding populations of several wader species, including almost the entire population of the islandica subspecies of Black-tailed Godwits. For several years, wader biologists in Iceland have been monitoring the breeding performance of Black-tailed Godwits in the Southern Lowlands, by counting pairs with broods along a 198 km transect. Their theory was that breeding performance would be better in warm years because of the advantages of early nesting in warm springs.

graphWith six years of data, a team drawn from the universities of Iceland, Aveiro (Portugal) and East Anglia (UK) have published a paper in the BOU Journal IBIS, which fouses upon the relationship between spring temperature and the number of Black-tailed Godwit broods. In the top graph, taken from the paper, it is clear that there is a lot of variation in productivity, with the lower graph showing a strong association between mean May temperatures and the number of Black-tailed Godwit pairs with chicks. What stands out is  the outlier for 2011 (open dot), which is excluded from the calculations that produce the regression line. For the five other years R² = 0.94, indicating a very close link between May temperature and productivity, as predicted. Using the mean temperature for May 2011, the number of pairs of godwits with chicks that might have been expected to have been seen in 2011 is about 25 – rather than just two.

The full methods can be viewed in this paper:

Effects of spring temperature and volcanic eruptions on wder productivity. Tómas Grétar Gunnarsson, Lilja Jóhannesdóttir, José A Alves, Böðvar Þórisson & Jennifer A Gill. IBIS (2017) DOI: 10.1111/ibi.12449

The ash effect

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Eyjafjallajokull in 2010

We all remember the eruption of Eyjafjallajökull in 2010. This produced copious amounts of ash, most of which was blown south to mainland Europe, disrupting air travel. Grimsvötn, which erupted in May 2011, was less famous but actually depositied a lot more ash in Iceland, especially in the Southern Lowlands.

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Ash  covered pools and clogged insect traps

On dry days, fieldworkers working in this study area used face masks to protect their respiration, as simply walking through vegetation disturbed large amounts of ash into the air. A layer of ash was frequently observed covering pools in wetlands and traps for invertebrate sampling were often clogged with ash. Short-term negative effects of volcanic dust on birds have been reported previously, probably acting through increased invertebrate mortality, and the low count of successful broods in the warm summer of 2011 seems to bear this out.

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An alarming parent godwit

By monitoring breeding Black-tailed Godwits in southern Iceland, the wader scientists have shown that volcanic activity can have a major impact  on bird productivity. Productivity was back to what appears to be normal (when corrected for mean temperature) by the next summer. The lack of recruitment in 2011 seems to have been reflected in a slight decrease in the counts of Black-tailed Godwits in the United Kingdom in the winter 2011/12 (as measured by WeBS counts), with a resumption in what is generally an upward population trend in 2012/13.

The rapid recovery of productivity in the year following the volcanic eruption (2012) indicates that the negative effects of the incident seem to be have been short in duration. Whimbrels in the same region were also affected by volcanic activity in the summer of the 2011 eruption (Katrínardóttir et al. 2015). In the long-term, the effects of volcanic activity on waders in Iceland are most likely to be positive, as volcanic dust recharges vegetated land with nutrients and buffers pH. Densities of waders across Iceland are generally higher where volcanic dust inputs are higher (Gunnarsson et al. 2015).

singleThis study shows how annual variation in productivity can vary greatly in response to rare and extreme events. As expected for a long-lived species, effects of a single year of very low productivity were short in duration and probably had a limited effect on the population growth rate. The pronounced effect that spring temperature has on annual variation in productivity is likely to be a more significant factor in the future population trajectory of waders, given the ongoing and rapid warming of Arctic and Sub-arctic regions.

Effects of spring temperature and volcanic eruptions on wder productivity. Tómas Grétar Gunnarsson, Lilja Jóhannesdóttir, José A Alves, Böðvar Þórisson & Jennifer A Gill. IBIS (2017) DOI: 10.1111/ibi.12449


GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton