Stick insects expand territory after being eaten by birds

May 28, 2018, Kobe University

It's commonly assumed that when insects are eaten by birds, they and their unborn young have no chance of survival. However, a team of Japanese researchers hypothesized that the eggs within insect bodies can pass through birds undigested. They tested this hypothesis with stick insects, known for their hard eggs, and found that some eggs are excreted unharmed and successfully hatch. Stick insects cannot travel very far by themselves, so being eaten by birds could even contribute to expanding their habitat.

The research team was led by Associate Professor Kenji Suetsugu (Kobe University Graduate School of Science), Associate Professor Katsuro Ito (Kochi University), and Associate Professor Takeshi Yokoyama (Tokyo University of Agriculture and Technology). The findings were published in the online edition of Ecology on May 28.

Plants cannot move around, so they have developed various ways to distribute their seeds. The most common is seed dispersal by animals, who eat the fruits and excrete the seeds whole. For many birds, insects are also one of their main food sources. If insect eggs can pass through birds unharmed, we could say that insects, just like plants, are using the birds as a means of long-distance transport.

To achieve this, several conditions must be met: the eggs must be strong enough to pass through digestive tracts unharmed, the insect young born from these eggs must be able to fend for themselves, and the eggs must be viable without fertilization. Stick insects fulfil these conditions. The insect eggs are only fertilized just before the eggs are laid, using sperm stored within the seminal vesicle. However, females of many stick insect species are parthenogenic, enabling them to produce viable eggs without fertilization. In addition, like plant seeds, stick insect eggs have a very hard shell. They lay these eggs by scattering them on the surface of the ground, and after hatching the young locate suitable plants for food by themselves.

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Wail, Chuck, Snort: Rock Hyraxes Sing Complex Songs

Small mammals called hyraxes "sing" long and complex songs to announce their territory. New research shows these songs are never repeated and have regional dialects, because neighbors tend to steal each other's special vocal twists.

"We aren't claiming they have a language," study researcher Arik Kershenbaum, of the University of Haifa, in Israel, told LiveScience. "But they are showing some of the characteristics that are essential for true language."

The rock hyrax is a small, sturdy mammal that lives in Africa and the Middle East and, strangely enough, is a relative of the elephant. It eats plants and possibly bugs and lives in small groups, usually dominated by one male. This male has a tendency to stand up and shout — singing songs that are complex and can go on for "a number of minutes," Kershenbaum said.

The songs also seem to be a form of self-advertisement, kind of like birdsong.

Read on:  http://www.livescience.com/19743-rock-hyrax-song-dialect.html

Nightingales quarrel at eye level

Male nightingales that sing to defend their territory quarrel more at eye level, say scientists.

During night-time singing bouts, males are known to interrupt each other's calls and rapidly change their songs.

Researchers wanted to investigate whether the birds tried to gain a height advantage by moving higher up in their chosen trees.

They found that the birds were actually more aggressive when singing from branches that were at the same height.

The findings, published in journal PLoS One, surprised the researchers.

"We expected nightingales singing from higher song posts to appear more threatening to their rivals," said Dr Valentin Amrhein from the University of Basel, who was the senior author of the study.

Alongside their colleagues from the Netherlands Institute of Ecology, the scientists theorised that the birds' positions could have a significant effect on how "threatening" their calls were.

Dr Amrhein explained that higher branches were thought only to be accessible to the fittest and most dominant birds, because taking up a loftier post increased threat of predators and reduced protection from the elements.

The team believed, therefore, that males singing from higher positions would represent more of a threat to their rivals, and elicit more of a defensive response from other males.

Read on:  http://www.bbc.co.uk/nature/17403241

Experienced Male Nightingales ‘Show Off’ To Protect Territories

Male song birds sing to attract mates and to deter other males from their territory and it is well known that the solo repertoire of many male song bird species increases with age and experience. However, new research published in BioMed Central’s open access journal Frontiers in Zoology has examined the songs sung by male nightingales in response to recordings which mimicked an invading male and suggests that older males are less threatened by intruders resulting in less song matching.

Researchers from Freie Universität Berlin observed the behavior of male nightingales in Treptower Park in response to playback of prior recordings of nightingale songs. Males in their first breeding season are recognizable by pale tips to their secondary feathers and tertials, and individual nightingales could be tracked by color coded leg rings. Five of the one-year olds returned for a second year and were again tested with playback of recorded nightingale songs.

The length of the song (three seconds) and, if the male chose to sing before the recorded ‘intruder’ finished its song, the amount of overlap (approximately two seconds after the recording started) did not differ between the two age groups. Nor did these values alter for the birds followed over two seasons. However, there was a difference in song matching. Song matching (repeating the song that was just played) is thought to signal aggressive intent or at least provide a warning that the interloper is encroaching on established territory. While most of the one year olds tended to match songs with the recorded intruder, older birds matched songs less often, and birds in their second year overlapped songs more frequently than in the previous year. Additionally, one year old nightingales used a third less individual songs than two-year olds (127 compared to 179).

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