Hardangervidda IBA: En smak av Arktis i Sør-Norge

Sjøorre

Mye av Hardangervidda IBA er vernet. I 1981 ble Nordens største nasjonalpark etablert, noe som skulle hjelpe til å bevare et unikt og storslagent fjellområde sør i landet. Dessverre betyr det ikke at de siste tiårene har vært uten problemer for fuglene som lever der.

Hardangervidda er et gedigent høgfjellsplatå, faktisk det mest omfangsrike i Europa. Fjellområdet deles av fylkene Hordaland, Buskerud og Telemark. Landskapet sentralt og øst på vidda domineres av flatt eller bølgende terreng med et mylder av små og store vann. Områdene i vest, samt områdene nord for selve nasjonalparken, er mer kuperte. I nasjonalparkens randområder i vest stuper fjellene ned i de dype vestlandsfjordene.

Fjellfugler i tilbakegang

Hardangervidda ble tidlig valgt ut som et «Important Bird and Biodiversity Area» (IBA) av NOF. Artssammensetningen er karakteristisk for det arktiske biomet, og Hardangervidda er også en av landets viktigste hekkeområder for den globalt truete dobbeltbekkasinen. Bestanden i IBAet er anslått til 100–200 par, men kan godt være betydelig større. Heilo er en karakterart i fjellområdet, mens jaktfalk, sjøorre og temmincksnipe finnes i mindre antall på en del lokaliteter. Det kan også nevnes at Hardangervidda er det sørligste hekkeområdet for tundrasædgås (underarten rossicus av sædgås Anser fabalis) i Europa.

Dessverre viser nyere undersøkelser at flere av Hardangersviddas karakterarter har vært i tilbakegang de siste 20 årene, noe som sammenfaller med negative bestandstrender for flere av våre fjelltilknyttede fuglearter over store deler av landet. Ved å sammenligne hekkefaunaen i et område på 1250 moh. i Eidfjord kommune i 2010 og 2011 med registeringer gjort 30 år tidligere, fant Byrkjedal og Kålås (2012) indikasjoner på en urovekkende tilbakegang hos en del vanlige arter. Nedgangen var på om lag 40 % for heipiplerke, 65 % for steinskvett og hele 85 % for lappspurv. Mulige habitatendringer på hekkeplassen og negative faktorer på overvintringsplassen er ansett som mulige årsaker.

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Solar tracking gives scientists tools to follow small animals

( 21 June 2017; Photo: Hana Londoño Oikawa)

Keeping tabs on wild birds has long been a low-tech proposition. While radio collars and satellite tags became standard for tracking big mammals, binoculars and notebooks have remained critical for following most twittering, flittering birds.

The holdup has been battery weight. To bleep the signals that reveal an animal’s location, transmitter tags require power. But for birds that weigh no more than a few pennies, even a watch battery can be too much to bear. Add in the need for recapture every few days to replace those batteries, and the dream of automated animal tracking becomes a logistical nightmare.

Now, new, lightweight tracking tags are making small animal tracking feasible. During field testing at the NRS’s Hastings Natural History Reservation, it’s given scientists a whole new perspective on the acorn woodpeckers (Melanerpes formicivorus) they’ve watched for decades. The birds turn out to be a lot more sly and strategic than researchers had long believed.

“You’d think that after almost 50 years of study, we’d know all there was to know about acorn woodpeckers. But this technology is helping us to answer questions we couldn’t answer before,” says Eric Walters, a biology professor at Old Dominion University, Virginia.

Woodpecker families are weird

These scarlet-capped birds are head-scratchers, all right. For starters, their family structure is among the most peculiar in the avian world. Several related birds of one sex (often sisters), typically breed with an unrelated set of several related birds of the opposite sex (often brothers).

Another puzzler surrounds the life choices of young woodpeckers. Where most fledglings leave the nest to found their own families, young “helper” woodies may linger at home for a decade.

“The question we had is, why? There must be some benefit to staying at home,” Walters says. “Do they spend their time at home helping to feed their siblings and store acorns? Or are they like teenagers in the basement watching TV all day and doing nothing?”

Game of Granaries

Walters suspected the answer lies in a young woodpecker’s thirst for territory. Like the fictional nobles in “Game of Thrones,” birds will do anything to conquer their own kingdom. Their goal is to secure a good granary tree, which houses the acorn stash critical to a woodpecker family’s survival.

A massive granary tree affords a woodpecker family plenty of advantages. They’re more likely to survive harsh winters, raise surviving chicks, and ensure the triumph of their own bloodlines.

Good granaries are tough to come by. It takes an age to build one — the hole for one acorn might take ten minutes to excavate, and large granaries may hold tens of thousands of acorns. Competition to secure the biggest granaries and their surrounding territory is fierce.

Gang wars

A granary goes up for grabs only after all breeders of one sex in a family group have died or left. When a breeding spot opens up, birds from other families battle over the succession.

Successful combatants don’t show up alone. Instead, groups of siblings from other territories duke it out.

“It’s like a gang war,” says graduate student Natasha Hagemeyer, who is studying woodpecker dispersal at Hastings with Walters.

Clashes may last for days, with foes hunting one another through the trees, grappling in midair, falling to the ground, and hammering one another with their powerful bills.

Grievous injuries aren’t uncommon. “One had a toenail torn out and bled profusely. Another got some of its wing feathers ripped away; it disappeared within a week,” Hagemeyer says. But the potential spoils — the chance to breed — are worth any cost.

Waiting in the wings

When a rare vacancy does open up, aspiring replacements are ready. “When we caught a breeding bird to band, other birds thinking it was gone would move in and start challenging for that territory within ten minutes,” Walters says.

How neighboring birds figured this out was a mystery. “We almost never see them off territory,” Hagemeyer says.

Previous studies done with radio transmitters indicated young birds do go on longer forays off their own family’s domain. “But when you radio track on foot with handheld antennas, you can only follow one bird at a time. To follow a set of siblings, you need a one-to-one ratio of people and birds. It rapidly becomes infeasible. And if an animal wants to be sneaky, like going into an enemy’s territory, you can spook them, making tracking just about impossible,” she says.

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When estimating extinction risk, don’t leave out the males

(Physorg 21 June 2017; Photo: Luke Eberhart-Phillips)
Extinction risk for some species could be drastically underestimated because most demographic models of animal populations only analyse the number and fertility of females, dismissing male data as ‘noise’.

An international team of researchers, including a PhD student and a professor from the Milner Centre for Evolution at the University of Bath, found that population growth in birds was very sensitive to the ratio of males to females in a population, called the adult sex ratio (ASR), which has previously been shown to affect mating behaviour.

The researchers have published their findings in the prestigious science journal, Proceedings of the National Academy of Sciences.

Species with a high number of males in a population tend to be polygamous: the females typically breed with several partners in one season, leaving the males to do most of the care for their offspring. However, with a large number of males competing for fewer females, a male biased population can also lead to increased aggression and harassment of females which can reduce survival rates.

Conversely, species with a higher number of females to males have lower parental investment by fathers which can also adversely affect survival of offspring. Where numbers of each sex were evenly balanced, parents cooperated more in care of their young and breeding pairs tended to be monogamous.

The researchers looked at why an unbalanced sex ratio should develop in some birds. They studied the survival and breeding behaviour of 1,259 wild Snowy Plovers in north-western Mexico over a seven year period, a species that is typically male biased. The team found that whilst a similar number of males and females hatched, males had higher survival rates at all stages of life, but particularly at the juvenile stage, when individuals are independent of their parents but not fully grown.

These findings could impact the conservation of endangered species, since ignoring the sex ratio of a population could miscalculate the survival rates and therefore underestimate the vulnerability of species to extinction.

Professor Tamás Székely, from the Milner Centre for Evolution at the University of Bath, said: “Our research has shown that population growth is very sensitive to changes in the survival of the limiting sex. A biased sex ratio either way can compromise population stability – too many males increases violence, whereas too many females leads to less cooperation between parents which reduces the survival of offspring.

“Current extinction models only take numbers of females into account – our research shows this approach could drastically underestimate extinction risk and states that males should also be part of the equation.”

Luke Eberhart-Phillips, PhD student at Bielefeld University (Germany) and first author of the paper, said: “Our research shows that in Snowy Plovers the population is male-biased due to sex differences in survival of young individuals, rather than at birth or during adulthood.

“Therefore, the evolution of different mating systems – whether polygamous or monogamous – could be a consequence of innate sex differences in survival. In mammals, population sex ratios are typically female biased, whereas in birds, these sex ratios are usually male biased. “Based on our results, one could speculate that sex differences in survival during early life are driving these large-scale patterns and the evolution of breeding behaviours.”

Trash-picking seagulls excrete tons of nutrients

(SD, Duke University 21 June 2017)

At least 1.4 million seagulls feed at landfills across North America, which aside from the nuisance it might pose, is also a threat to the health of nearby waters, a new Duke University study finds.

“We estimate these gulls transport and deposit an extra 240 tons of nitrogen and 39 tons of phosphorus into nearby lakes or reservoirs in North America each year through their feces,” said lead author Scott Winton, a 2016 doctoral graduate of Duke’s Nicholas School of the Environment.

The added nutrients contained in the birds’ droppings can contribute to extensive algal blooms that rob surface waters of much of the oxygen needed to sustain healthy aquatic animal life — a process known as eutrophication.

Oxygen depletion and algal toxins that result from the blooms can have far-reaching ecological and economic impacts, including fish kills, increased costs for local governments, and reduced recreational or fishing values in affected waters.

“It costs local U.S. governments an estimated $100 million a year in nutrient offset credits to address or prevent the problem and maintain nutrient levels at or below the total maximum daily load threshold for water quality,” said Mark River, a doctoral student at Duke’s Nicholas School, who conducted the research with Winton.

The scale of the problem and the cumulative cost of dealing with it may be even larger than the new study suggests, said Winton, who is now a visiting postdoctoral fellow at ETHZurich, a science and technology university in Switzerland.

“We estimated and mapped a landfill-gull population of 1.4 million based on documented sightings reported in the eBird Citizen Science database. But the actual population is probably greater than 5 million,” Winton said. “That means the amount of nutrients deposited in the lakes, and the costs of preventing or remediating the problem, could be substantially higher.”

Winton and River published their study, which is the first to look at the transport of nutrients into surface waters from seagulls at landfills, on June 15 in the journal Water Research.

They conducted the research at landfills near two major drinking water reservoirs — Jordan Lake and Falls Lake — that serve the Raleigh-Durham region of North Carolina. Nitrogen and phosphorus loading data from these two lakes were then scaled up to estimate total loading at water bodies near landfills across North America using a well-established model for measuring the nutrient transport of carnivorous birds.

The findings are applicable to lakes and reservoirs in other parts of the world, as well.

“The idea that gull feces can be a major water quality problem may sound comical — until you look at data from an individual lake,” Winton said. “In Jordan Lake, for instance, we found that a local flock of 49,000 ring-billed gulls deposit landfill feces containing nearly 1.2 tons of phosphorus into the lake annually.”

That amount, he said, is equivalent to roughly half of the total phosphorus load reduction target established for the New Hope Creek watershed of Jordan Lake. Offsetting this added phosphorus costs local governments about $2.2 million annually — largely through long-term programs aimed at reducing other sources of inflowing nutrients such as urban stormwater or agricultural runoff.

Reducing the size of the gull flocks may also be an option worth pursuing, Winton said. Reducing the size of open landfills, and covering trash more quickly after it is dumped, are among the ways managers can reduce the gulls’ easy access to a food supply and encourage a flock to disperse to other feeding habitats.

“There’s a decent history of local governments implementing gull management at landfills because of fears about airplane strikes or because of the nuisance factor to nearby communities,” Winton said. “It might be cost-effective to pursue some of these non-lethal mitigation methods to reduce nutrient loading, as well.”

Paradise saved: some of world’s rarest birds rebound on Pacific islands cleared of invasive predators

tutururu1.jpg

(Shaun Hurrell 20 June 2017; Photo: Marie-Helene Burle)

Five remote Pacific islands are once again safe havens for four of our world’s rarest bird species following the success of one of the most ambitious island restoration projects ever implemented

Just two years after ambitious efforts by a team of international conservation organisations to rid French Polynesia’s Acteon & Gambier island groups of invasive mammals began, five of six targeted islands are now confirmed as predator-free—a ground-breaking one thousand hectares in total. Early signs already indicate that rare birds found nowhere else in the world (endemic) and other native plants and animals are recovering as the remote islands return to their former glory.

The Polynesian Ground-dove Alopecoenas erythropterus (locally known as Tutururu) is one of the rarest birds on the planet with fewer than 200 individuals left. Predation and competition by destructive, non-native (invasive) mammals in French Polynesia have driven this and other rare, endemic bird species to the brink of extinction. The species is listed by BirdLife International as Critically Endangered on the IUCN Red List—a category that signals an extremely high risk of extinction within our lifetimes.

“The Acteon Gambier island group is home to the last viable population of Polynesian Ground-dove, a species once much more widespread in the Pacific”, said Steve Cranwell, BirdLife International’s Invasive Species Manager. “This bird’s remaining predator-free habitat was so small that without this intervention, a cyclone, prolonged drought, or accidental rat or avian disease introduction could trigger extinction”.

Introduced mammalian species alone are believed to be responsible for 90% of all bird extinctions since 1500. Early human explorers introduced invasive species such as rats to the remote Acteon & Gambier islands (and thousands more around the world), upsetting the natural balances of the islands and threatening the native plants and wildlife that evolved without defences against land predators.

Operation Restoration

Combining resources, expertise, equipment, and logistical skills, a coalition of NGOs, BirdLife International, SOP Manu (BirdLife Partner, French Polynesia) and Island Conservation—together with the support of the government of French Polynesia, landowners, other partners and local volunteers—voyaged over 1,500 km to six of French Polynesia’s remote islands—Vahanga , Tenarunga, Temoe, Kamaka, Makaroa and Manui to complete the challenging project in 2015.

The project required years of planning and fundraising (including a cooperation with Rovio, the maker of Angry Birds), involved nine permits, 165 helicopter flight hours, three ships transporting hundreds of tonnes of equipment and donated bait from key partners Bell Laboratories and Tomcat, as well as 31 personnel from six countries (from three continents) who endured extraordinary weather and sea conditions during 12-day journeys to and from the islands. The prospect of a brighter future for the Tutururu and other native island species made the operations well-worth the effort.

“After extensive monitoring, a survey in April has confirmed great success on five of the six islands”, reported Dr David Beaune, Director SOP Manu. “This is a tremendous achievement that will provide a permanent solution to the alarming declines of native species on these islands due to predation and competition from invasive species”.

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Birds of all feathers work together to hunt when army ants march

ruddy_woodcreeper.jpg
(SD, Drexel University 19 June 2017)
Army ants scare up a lot of food when they’re on the move, which makes following them valuable for predator birds. But instead of competing and chasing each other off from the ant “raids,” as scientists had thought, birds actually give each other a heads up when the ants are marching, according to a new Drexel University study.

For more than a decade — from 2005 until 2016 — Sean O’Donnell, PhD, a professor in Drexel’s College of Arts and Sciences, observed army ant “raids” and the birds that follow them. He hoped to find out whether birds really were aggressive toward each other during the ant marches or whether they actually cooperated to access the food (other insects and bugs) that ants rustle out of hiding.

After observing 74 swarms in Costa Rica, it seems birds are much more likely to play nice with each other.

“Overall, the results strongly supported facilitation — species help each other to exploit shared resources,” O’Donnell said of his study that was recently published in Biotropica.

In watching for the raids and the flocks that “attend” them, a key to avian cooperation may be what are termed “bivouac-checking” birds. These are birds that perch near the sites where army ants make their nests (bivouacs) and watch to see where and when the ants move. Birds that fall into that category include the ocellated antbird and the blue-diademed motmot.

The prevailing thought has been that these specialized birds liked to keep the ant colonies they watched to themselves, not allowing other species to horn in on their finds.

But a frequent high diversity of species in flocks following the ant columns showed O’Donnell that birds that didn’t specialize in tracking army ants (like the migrant species Kentucky warbler) were allowed to join and hunt.

So when bivouac-checking birds see the movement of the columns and take off, other birds take the cue. They either know birds like the ocellated antbird follow ant columns or recognize vocalizations the specialized birds make when chasing the colonies.

“Birds may use each other as a way of finding army ant raids, which are very hard to locate in the forest because they are widely spaced and the ants are mobile,” O’Donnell said. “Observations suggest some birds are attracted to other birds at raids, and birds may even follow each other when moving among raids of different ant colonies.”

However, there did seem to be some bullies.

O’Donnell noticed some pairs of species were almost never found in flocks together despite, independently, being ant-chasers. That indicated that these bird species might chase each other off as competition, or just avoid each other entirely. Pairs that seemed to be unable to be around each other included the blue-throated toucanet and the brown jay, as well as the wood thrush and the white-eared ground sparrow.

“These antagonistic pairs were often species of very similar body size or feeding behavior,” O’Donnell explained. “Perhaps these species do compete very strongly at army ant raids.”

All in all, finding that birds largely work together to forage at army ant raids seems to demonstrate that cooperation is a better survival strategy than trying to keep food from the raids for their own species.

“Having other birds around may be an advantage because there are more eyes and ears to detect predators,” O’Donnell said. “If the raid is hard to monopolize, and food is very abundant there, then the costs of allowing other birds to attend may be low, further favoring positive species interactions.”

Climate change risk for animals living in prime conditions

bird

(Physorg, University of Exeter 13 June 2017)

Animals living in areas where conditions are ideal for their species have less chance of evolving to cope with climate change, new research suggests.

The study examined whether birds might be able to evolve to adapt to changes to the natural environment within their range – the geographical area where the birds nest, feed, migrate and hibernate over the course of their lifetimes.

It found that populations that experienced both the most favourable conditions, usually at the centre of their species’ range, and toughest conditions found at the very edges of the range had the lowest evolutionary potential. The populations that displayed the greatest potential to evolve with changing conditions were found living between the two extremes, the study showed.

The research team, including scientists from the University of Oviedo, University of Málaga, Doñana Biological Station, the University of Exeter and the University of Western Australia, studied data on 12 European bird species.

“We were surprised to find reduced evolutionary potential among birds living in the centre of a species’ range,” said co-author Dr Regan Early, of the Centre for Ecology and Conservation on Exeter’s Penryn Campus in Cornwall.

“The reasons for this are not clear, but high levels of competition in prime areas might lead birds with certain traits to survive – meaning little genetic variety in the population and consequently little scope for evolution.

“We found that populations of birds on the edge of a species’ range – like those in the centre – had a reduced ability to evolve,” said lead author Dr Jesus Martinez-Padilla, of the University of Oviedo.

“This is probably because they already live in tough conditions for their species. As climate warms, these populations will probably have to move or die out. This is what might happen to populations of the Pied Flycatcher in southern Europe. These populations have little genetic variation compared to northern populations, so they won’t be able to adapt to a changing climate. The birds living in places neither the best nor the most hostile environmental conditions – appear to have the best evolutionary potential.”

“Evolution could prolong the period in which these populations are able to survive in situ as conditions worsen, or allow these populations to evade local extinction altogether”, Dr Regan Early pointed out.

Understanding the likelihood that evolution may occur could improve our understanding of how species will respond to climate change, the scientists say.

The paper, published in the journal Proceedings of the Royal Society B, is entitled: “Evolvability meets biogeography: evolutionary potential decreases at high and low environmental favourability.”