From Birdguides and BBC

A new study has found that anthropogenic electromagnetic noise, emitted everywhere that we use electronic devices, has a negative impact on birds’ magnetic compasses. The work, which used robins as a study species at the University of Oldenburg, found that the birds could not use their compass when exposed to electromagnetic noise but, when shielded from it, soon regained their navigational abilities. The ‘noise’ is produced by equipment plugged into mains electricity supplies and through AM radio signals.

Prof Henrik Mouritsen (University of Oldenburg) said “They (birds) have their different compasses: a star compass, a sun compass and a magnetic compass”. It is thought that a built-in magnetic compass, which senses the Earth’s magnetic field, helps them to find their way. Prof Mouritsen told BBC News he stumbled across the fact that low frequency waves could be interfering with this by accident while studying European robins.

“The basic experiment we do in bird navigation research is that we put birds into an orientation cage,” he explained. “They are so eager to migrate, that they will jump in the direction in which they want to fly, and if you turn a static magnetic field in the horizontal plane they will start to jump in a different direction.

“That experiment has worked for more than 40 years in a number of locations. But here in Oldenburg, we couldn’t get that basic experiment to work until one day we got the idea to screen these huts on the inside with aluminium plates so the electromagnetic noise was reduced about 100 times.

“And suddenly the birds started to orientate.”

Over the course of the next seven years, he and his team carried out numerous experiments to look at how the weak electromagnetic field affected the behaviour of the robins. In essence, he found that birds exposed to electromagnetic “noise” between 50 kHz and 5 MHz lost all sense of direction. But when the field was blocked out, they found their bearings again.

Prof Mouritsen said that migratory birds flying over towns and cities, where there are more homes and businesses that use electrical devices, would be most affected – and they would probably resort to back-up navigational systems.

“The birds wouldn’t be completely lost because they have three different compasses: a star compass, a sun compass and a magnetic compass, and they work independently of each other. As long as it is clear they should be fine with their sun compass or star compass.”

These findings are particularly fascinating when considering the vagrancy of migratory birds. While the impact of electromagnetic noise is unlikely to be a primary cause of vagrancy, its potential to disrupt migrating birds — whether lost or following a more typical path — is evident if and when they pass through populated areas, where use of electronic devices is high, and there can be no doubt of its potential as a contributing factor. Further study on other migratory species would be useful in establishing the true extent of such problems.

Read more about the history of experiments at National Geographic and read the abstract at Nature

From Exeter University

Fishing vessels have a far bigger ecological footprint than previously thought, according to research which tracked the movement and behaviour of seabirds using GPS devices.

Scientists discovered that northern gannets change their behaviour in response to the presence of large vessels such as trawlers, suggesting each boat can significantly influence the distribution and foraging patterns of these and other marine predators.

Northern gannets are known to feed on discards from fishing vessels as well as diving for fish, and their population has been steadily increasing for decades. Studies have confirmed their use of fisheries waste by showing that the birds are eating fish that have come from far deeper than they are able to dive.

Scientists at the Centre for Ecology and Conservation at the University of Exeter and the Coastal & Marine Centre at University College Cork analysed GPS tracking data from 74 gannets from six breeding colonies around Ireland, and combined these with similar GPS tracking data from fishing vessels.

The information gathered revealed that gannet behaviour is influenced by fishing vessels at distances of up to 11km – the first estimate of the distance at which vessels start to affect these birds’ behaviour.

Dr Thomas Bodey of the University of Exeter, who led the study, said: “Our work suggests each fishing vessel has a substantial footprint, with the behaviour of seabirds affected within a 22km diameter circle surrounding it, much larger than we expected.”

By studying bird-boat interactions, the team also discovered that individual gannets can adjust their behaviour depending on whether the vessel is actively fishing or not, and also based on the type of fishing gear carried.

Dr Mark Jessopp of the Coastal & Marine Centre at University College Cork, a co-author of the work, added: “The fact that birds responded differently to boats depending on whether they were fishing or not, and the type of gear they were carrying, indicates just how finely attuned these animals are to the opportunities humans can provide”.

The findings help to understand the spatial influence of fisheries, which is critical to marine planning and policy – including shipping, offshore development, bycatch and fisheries themselves.

Co-author Professor Stuart Bearhop, also of the University of Exeter said: “We know that seabirds are facing many impacts within the marine environment, and we have tended to think that interactions with fishing boats were a localised phenomenon. Our work indicates that the scale of impact on these top predator’s behaviour is much broader.”

Gannets are the UK’s largest seabird, foraging up to 500 km from their colonies. They forage almost exclusively during daylight hours, with birds resting on the sea surface at night. They are visual foragers with no external nostrils and relatively small olfactory bulbs.

All fishing boats greater than 15 m in length must carry a GPS transmitter as part of the European Union Vessel Monitoring System.

The results of this study are published in Current Biology.

House martins, like their close relative the swallow, return each spring to their familiar mud nests, typically built onto our own homes and offices. Like the swallow, their return each year cheers us up as it reminds us that summer is coming. It is, therefore, somewhat surprising then that, for a bird that is so familiar to us, we know virtually nothing about what happens to house martins after they leave Jersey.

Recoveries of ringed birds from across France and on into North Africa have revealed a migration route south but we have no idea what happens to these birds once they cross the Sahara. House martins are rarely seen in Africa during our winter. There has only been one record of a ringed house martin from south of the Sahara, despite the many thousands of individuals to be fitted with rings in Britain each year (see tracking house martins).

It has been suggested that they remain on the wing and feed above the canopy of the equatorial rainforest, out of sight of human eyes.

However, what we do know is that house martin population in the UK may have declined by 15% over the last decade and may have fallen by as much as two-thirds longer term. In Jersey the house martin was (in 2011) Amber listed as it has shown a moderate breeding population decline (see report here). Since 2011 numbers have continued to decline alarmingly suggesting that it might be Red listed (severe decline in the Jersey breeding population size, of more than 50% over 20 years) when the list is next revised.

It is not clear how many house martins there are in Jersey as it has been difficult to survey them. What we can do is watch closely their colonies and see how they are faring each year and from year to year. If you have a colony on your house or other buildings and would like to record the birds please get in touch with Birds On The Edge by e-mail birdsote@gmail.com The BTO will be carrying testing survey techniques this year before starting a wider survey of house martins in the British Isles in 2015. We will feed Jersey’s results from this year into the national survey.

House martins and their nests are fully protected in Jersey. Please download guidelines here.

From BTO

Climate change is having dramatic effects on many of our species, and not always in obvious ways. A new study demonstrates that climate change disrupts natural relationships between species. Part II of The Intergovernmental Panel on Climate Change (IPCC) fifth assessment report, published at the end of March, reported that climate change is altering species’ distributions and populations with high confidence. However, what is less clear is how and why. Latest research led by the British Trust for Ornithology (BTO) shows that the main driver of change might actually occur through altered interactions between species, rather than direct responses to climate.

Each species shares an ecosystem with other species, some of which it might eat, and others that might eat it or compete with it. Scientists from the BTO and other partners of the Cambridge Conservation Initiative (CCI) found it was the effects of climatic changes upon the populations or activity of these other species which were responsible for many of the impacts observed, as they cascade through the food chain. For example, Arctic fox populations have been affected by declining lemming populations linked to changes in snow cover, and also by expanding red fox populations. Hungry Arctic foxes may look to other prey such as breeding wildfowl like brent goose and waders like sanderling  (they already feed on these birds during ‘lemming years’ – in Jersey we don’t see any young geese at all some years). In the UK, upland birds such as the golden plover are affected by increasing summer temperatures, which causes problems for their cranefly prey. These disruptions particularly affect predatory species, and appear to have worsened with climate change.

Dr James Pearce-Higgins of the BTO said, “Although it might be assumed that most species are responding directly to climatic changes, either as individuals move to keep within their favoured climate zone, or through survival and reproductive rates linked closely to these climatic variables, this does not account for the majority of impacts. Instead, the main impacts of climate change occur through altered interactions between species within an ecosystem.”

Importantly, as much conservation action is already about managing species’ populations, such as controlling invasive species or reducing predation risk, we already have the conservation tools in place to reduce the impacts of climate change on species. This understanding, therefore, provides hope that we can help the most vulnerable species adapt to climate change, providing the magnitude of climate change is not too great, and that conservation activity is sufficiently funded. For example, in the UK uplands, we can restore degraded peatland habitats to boost invertebrate cranefly populations, and increase their resilience to climate change. Whilst this work also helps identify the types of species’ most vulnerable to future climate change impacts, there remains a lack of information from the tropics, where most species’ occur, and where increased monitoring and research is essential.

“This study highlights a need to consider the often complex ecological relationships between species when assessing the impacts of climate change on wildlife.” says Jamie Carr of the International Union for Conservation of Nature, a co-author on the study. “Most research to date has focused on the direct impacts of changing conditions, which may mean that important emerging threats are being overlooked.”

The report can be seen here