Green feathers: how birds garden

The first evidence of a non-human species cultivating ornamental plants has been discovered in Australia. Male bowerbirds, known for building elaborate bowers to attract females, propagate bushes that provide a nearby supply of decorative fruit.

Joah Madden of Exeter University carried out the research with colleagues from German and Australian universities. He says the spotted bowerbirds they studied in Taunton National Park, Queensland, are probably accidental gardeners, though intentional cultivation cannot be ruled out.

The bushes growing close to their bowers germinate from fruit gathered for display and later discarded nearby. The birds clear the area around the bower of grass and weeds, primarily to provide a better view for potential mates, so the ground is well suited for their favourite fruit shrub, Solanum ellipticum (known as potato bush, or bush tomato), to flourish.

Observations showed that birds did not originally select locations for their bowers that were already surrounded by Solanum plants – the bushes grew up around the bowers, which individual males maintain for up to 10 years.

Whether the cultivation is deliberate or the indirect result of decoration, it is the first known example of non-human growing of plants for use other than food, say the researchers. Although humans can eat bush tomatoes, intensive observation and examination of the birds’ droppings show that bowerbirds never eat them.

Different species of bowerbird, which range across Australia and Papua New Guinea, favour different decorative colours. The spotted bowerbird goes for white (such as bleached shells) and green (such as bush tomatoes).

The greener the fruit, the better. Males bring back the greenest bush tomatoes they can find to decorate their bower, and later, when the fruits shrivel and turn brown, they move them away to the cleared ground. The researchers found that fruit collected from plants growing within 10 metres of the bower were significantly greener in colour than those growing further away.

“Our observations of enhanced association between the bird and plant, yielding benefits to each, leading to co-evolutionary change in fruit colour, mirrors the processes suggested to have originated cultivation in humans,” they write in the journal Current Biology, where the study is published.

The symbiosis brings reproductive benefits for the male birds, because individuals with closer access to greener fruit have more success in mating. They may also reduce their exposure to marauding neighbours seeking to steal their decorations – a constant risk for bowerbirds – because they have to spend less time away from the bower searching for fruit.


Slimewatch: how mucus fights off a virus

Mucus often evokes a “Yuck!” reaction, but it provides vital protection for all the wet surfaces in the body. It allows nutrients and other vital molecules in, while keeping out germs.

Researchers at Massachusetts Institute of Technology studied the antiviral action of mucus and, in particular, the mucin molecules – long, threadlike proteins that are the main building blocks of mucus.

“Often, they’re regarded as inert scaffold elements, but the picture emerging is that they have an active function in the body’s defence system,” says Katharina Ribbeck, senior author of the study, which was published in the journal Biomacromolecules.

Greater understanding of mucins’ immune function could shed light on why some people are more susceptible to viral or bacterial infections, says Ribbeck. Mucin composition differs between individuals, and it varies with age, diet and the time of year.

Previous research showed that mucins are abundant in breast milk, helping to protect babies against viruses. To find out whether this antiviral role is more general, Ribbeck’s team tested mucins’ ability to block three viruses from entering cells.

The researchers coated a lab culture of human epithelial cells with a layer of gel made from purified mucins, then exposed them to three human viruses. All three were trapped in the mucin gel, and thus unable to infect the cells.

The study also showed that a high salt concentration makes the mucins less penetrable – a possible explanation for why gargling or rinsing the nasal passages with salt water often soothes cold or flu symptoms.

The researchers believe mucins would have the same protective effects against most viruses. Indeed, Ribbeck thinks mucins might make good antiviral additives to personal hygiene products. At least one cosmetic company uses purified mucins in upmarket skin creams, albeit for their moisturising properties, not their antiviral effects.


Fingerprints reveal medieval must-reads

An art historian at the University of St Andrews, Scotland, has developed a scientific technique to study the habits of medieval readers through their dirty books.

Kathryn Rudy uses a densitometer – an instrument that measures the optical density of a reflecting surface – to tell which pages have accumulated the most dirt and grease from readers’ fingers and are therefore likely to have been the most read.

Studying a dozen devotional manuscripts from the late Middle Ages, Rudy has concluded that people in that period were “as self-interested and afraid of illness as they are today”.

One of the dirtiest pages is a prayer to St Sebastian, whose arrow wounds (the cause of his martyrdom) were reminiscent of plague pustules. People hoping to ward off the disease would seek the saint’s divine protection. On the whole, prayers for the salvation of others were read less frequently than those for one’s own salvation.

Another finding is that readers often fell asleep before reaching or finishing compline, the night prayer in a medieval book of hours.

Rudy now plans to examine a wider range of manuscripts. “Although it is often difficult to study the habits, private rituals and emotional states of people, this new technique can let us into the minds of people from the past,” she says. “Religion was inseparable from physical health, time management and interpersonal relationships in medieval times.”


New sound software names that animal

An Australian company has developed what it says is the first sound recognition system for personal computers that can distinguish the calls of different birds and animals better than the trained human ear.

Experts from SoundID presented three technical papers at the Acoustics 2012 conference in Nantes last month. They say the system will allow “widescale acoustic surveys” – automated studies of animal populations, based on their calls – to become commonplace.

Wildlife researchers have built up a large backlog of high-quality digital recordings too extensive for analysis by human specialists. The SoundID system claims to process a year’s worth of recordings within days, with software using new mathematical techniques. It produces “sonograms” by breaking down sound into its spectral components, and then compares these with a library of reference sonograms for the sounds being searched. For example, in Queensland it picked up toads, bats and rare parrots at the same time, while trials with the dawn chorus recognised 40,000 calls from 15 bird species over one hour.

Unlike type-specific sound recognisers – such as those used to recognise human speech or bird calls – SoundID can be set to recognise any sounds, which need not be related, as long as reference sonograms are available. So, if a completely unexpected species turned up in a survey area, this would be missed (though the chances are a human expert could miss it too).

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