Raptor Nest Decorations Are a Reliable Threat Against Conspecifics

The discovery of messages in raptors’ nests has raised the possibility that many bird species encode signals into these structures, with seemingly decorative flourishes actually full of meaning.

Among black kites, scraps of white plastic are used to signal territorial dominance. To other kites, the scraps are a warning sign. To humans, they hint at an unappreciated world of animal communication.

“It’s probably very common that other bird species decorate their nests in ways compatible with what we found,” said Fabrizio Sergio, a biologist at the Doñana Biological Station in Spain. “And not only birds, but fish and mammals.”

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Biological clock ticks slower for female birds who choose good mates

In birds as in people, female fertility declines with age. But some female birds can slow the ticking of their biological clocks by choosing the right mates, says a new study.

Female birds become progressively less fertile as age takes its toll, said co-author Josh Auld of the National Evolutionary Synthesis Center in Durham, North Carolina. Older females lay fewer eggs, and they lay them later in the season -- at a time when less food is available for their chicks, he explained.

But despite abundant evidence of fading fertility in females, scientists know little about the role played by their mates. "The thought was that males didn't matter," Auld said.

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Songbird’s Sex Hormone Surges at Sight of Flowers

As summer heats up, the sight of blooming thistles may give male goldfinches a testosterone kick.

Thistle flowers could signal to American goldfinches that the seeds the songbirds prize for baby food and parent food will soon be abundant, proposes Thomas Luloff of the University of Western Ontario in London, Canada. And in lab setups, male goldfinches housed among blooming Canadian thistles underwent physiological changes that indicate the birds got the “breed now” message from the combination of summery heat and thrilling thistles, Luloff reported January 6 at the annual meeting of the Society for Integrative and Comparative Biology.

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How seabirds share their habitat

When different species of seabirds share a habitat with limited sources of food, they must differ in their feeding habits. This specialisation is known by biologists as an "ecological niche." Researchers at the Max Planck Institute for Ornithology in Radolfzell have investigated how flexible these ecological niches really are. They discovered that the preying habits of diving seabirds are very different, both in location and timing, within species as well as between different species.

Ecological niches are not inflexible; they are affected by different habitats and the need to avoid competition with neighbours or evade predators, and also lead to different forms of behaviour within a single species.

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