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Mystery of millions of migrating birds dropping dead from US skies

Experts are struggling to explain a mystery mass die-off of migratory birds in the southwestern US that biologists have described as “devastating”.

Flycatchers, swallows and warblers are among the species “falling out of the sky” across New Mexico, Colorado, Texas, Arizona and as far north as Nebraska, according to Martha Desmond, a professor at New Mexico State University (NMSU).

Scientists began investigating the phenomenon in late August after ”a large number of dead birds” were found at the US army’s White Sands Missile Range and White Sands National Monument in New Mexico, CNN reports.

“We know this is a very large event, hundreds of thousands and maybe even millions of dead birds, and we’re looking at the higher end of that,” Desmond told the US news channel.

The biologist says that a number of the species are “already experiencing huge population declines, and then to have a traumatic event like this is devastating”, reports New Mexico-based newspaper Les Crucas Sun News.

According to witnesses, “some birds have been displaying unusual behaviour before dying”, with species normally seen in shrubs and trees spotted on the ground looking for food and chasing insects, says The Guardian.

Some biologists have suggested that the wildfires raging across the West Coast of the US could be to blame. One theory is that the smoke has affected the birds’ migration patterns, forcing them to fly inland over the Chihuahuan desert, where there is little food or water.

“They’re literally just feathers and bones,” said Allison Salas, a graduate student at NMSU who has been collecting carcasses. “Almost as if they have been flying until they just couldn’t fly anymore.”

Other possible explanations put forward include a recent “cold snap” in the Mountain States that could have worsened conditions for the birds, and droughts that have depleted insect populations in the southwest.

Any of these weather events “may have triggered birds to start their migration early, having not built up sufficient fat reserves”, according to The Guardian.

Another theory is that the smoke from the wildfires may have damaged their lungs.

“It could be a combination of things. It could be something that’s still completely unknown to us,” said Salas.

As efforts to unravel the mystery continue, scientists are urging people living in the affected areas to log any sightings of dead birds on the iNaturalist social network.

More on Mystery of millions of migrating birds dropping dead from US skies

Reference: theweek.co.uk 7 hrs ago: 16/09/2020

World's oldest sperm found perfectly preserved after 100m years

Perfectly preserved sperm dating back 100 million years has been found trapped in amber

The sperm - roughly 50 million years older than the previous oldest fossil record - belonged to an ostracod, a class of small crustacean that has been in existence for 450 million years. It was found in modern-day Myanmar.

Based on the fossil record and the behaviour of modern ostracod, the male used their fifth limb to transfer extraordinarily long but immotile sperm into the female.

The sperm was enormous too, being about 4.6 times the length of the female's body.

"This is equivalent to about 7.3m (23ft) in a 1.7m (5.5ft) human," said Dr Renate Matzke-Karasz of the Ludwig Maximilian University of Munich.

Sadly for the two little critters, they were enveloped by tree resin while in the throes of passion.

This resin fossilised into amber, preserving not just the lovers but dozens of other ostracods.

Researchers from the Chinese Academy of Sciences were able to use X-rays to obtain high-resolution images of the remarkably well-preserved soft parts of the ostracods.

These images provided direct evidence of the male clasper, the sperm pumps, the hemipenes (they had two penises) as well as the female's eggs and seminal receptacles (they had two of these as well) which contained the giant sperm.

Fascinatingly, research has revealed that sexual behaviour in ostracods, which features a wide number of morphological adaptations, has remained pretty much unchanged over the past 100 million years.

There are a number of conflicting theories about what the evolutionary value of such long sperm would be, according to Dr Matzke-Karasz.

"For example, experiments have shown that in one group, a high degree of competition between males can lead to a longer sperm life, while in another group, a low degree of competition also led to a longer sperm life," she added.

Whatever the mechanism, the findings reveal "that reproduction with giant sperm is not an evolutionary extravagance on the brink of extinction, but a serious long-term advantage for the survival of a species," Dr Matzke-Karasz concluded.

Reference: 2 hrs ago: 15/09/2020

The secret war going on between woodpeckers

Researchers monitoring woodpeckers using radio tags have made the startling discovery that the birds are going to war with each other. According to direct observations and, crucially, data collated from these radio tags, the birds fight battles which last for days at a time over new territory, with individual engagements sometimes lasting for ten hours.

In some cases woodpeckers will wait for years to build a war-fighting coalition before launching an invasion targeting a "granary", a structure built by the birds in which they stuff acorns into thousands of holes pecked into the bark of oak trees. Although woodpeckers sometimes breed in monogamous pairs, field studies have shown that they also form breeding collectives - generally made up of three males and two females - known as a coalition.

These coalitions form the basis for the battles according to the study published in the journal Current Biology. "When you're approaching a big tree with a power struggle from far away, you'll first hear a lot of acorn woodpeckers calling very distinctly, and see birds flying around like crazy," explained the first author of the study, Dr Sahas Barve.

Usually these wars begin when acorn woodpeckers inhabiting a high-quality territory die, and rivals attempt to capture the vacant spot. "When you get closer, you can see that there are a dozen or more coalitions of three or four birds fighting and posturing on branches," added Dr Barve, who is currently a postdoctoral fellow at the Smithsonian National Museum of Natural History.

"One group has to beat all the others to win a spot in the territory, which is really, really rare in animals - even in fantasy novels it usually boils down to one army against the other," the self-described bird nerd added.These battles can be frenetic and challenging to directly observe amid the chaos of the birds rapidly flying around.

Fortunately, Dr Barve and his team used new radio telemetry technology to track the birds' locations using tags strapped to the birds backs, allowing the team to monitor their movements and see how much time was spent fighting and where the combatants were travelling from. Usually the war-fighting coalitions are formed of groups of non-breeding brothers or sisters from neighbouring territories. Some of these birds return day after day and fight for ten hours at a time.

"We didn't think it could be that long because they have to be away from their home territory," said Dr Barve. "When do they eat? We still don't know." He and his team hypothesised that the woodpeckers would fight the hardest for territories closest to their current home, but found that actually more complex social cues might have been at play as the birds built up their coalitions.

"These birds often wait for years, and when there's the right time and they have the right coalition size, they'll go and give it their all to win a really good territory," said Dr Barve. The complex social behaviour even extended to observers - with dozens of additional birds of the same species often coming to watch the battles, some travelling more than 3km to do so for an hour or more - potentially gathering intelligence on their rivals.

Acorn woodpeckers have tight social networks, according to the researchers, and the spectators are "probably as interested in the outcome as the fighter is, although the warriors benefit more directly," Dr Barve added. "They potentially have friendships, and they probably have enemies," he added.

"With our radio tag data, we can tell when two birds are at the same place at the same time. The next step is to try and understand how their social networks are shaped, and how they vary across the year."

Reference: Sky News: Alexander Martin, technology reporter 20 hrs ago: 08/09/2020