Bird Navigation: Great Balls of Iron

Every year millions of birds make heroic journeys guided by Earth's magnetic field. How they detect magnetic fields has puzzled scientists for decades. Today, the Keays lab at the Research Institute of Molecular Pathology in Vienna has added some important pieces to this puzzle.

Their work, published in Current Biology, reports the discovery of iron balls in sensory neurons. These cells, called hair cells, are found in the ear and are responsible for detecting sound and gravity. Remarkably, each cell has just one iron ball, and it is in the same place in every cell. "It's very exciting. We find these iron balls in every bird, whether it's a pigeon or an ostrich" adds Mattias Lauwers who discovered them "but not in humans." It is an astonishing finding, despite decades of research these conspicuous balls of iron had not been discovered.

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Ecology Buys Time for Evolution: Climate Change Disrupts Songbird's Timing Without Impacting Population Size (Yet)

Songbird populations can handle far more disrupting climate change than expected. Density-dependent processes are buying them time for their battle. But without (slow) evolutionary rescue it will not save them in the end, says an international team of scientists led by the Netherlands Institute of Ecology (NIOO-KNAW) in Science this week.
Yes, spring started late this year in North-western Europe. But the general trend of the four last decades is still a rapidly advancing spring. The seasonal timing of trees and insects advance too, but songbirds like Parus major, or the great tit, lag behind. Yet without an accompanying decline in population numbers, it seems, as the international research team shows for the great tit population in the Dutch National Park the Hoge Veluwe.

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Baby Birds Blackmail Parents for More Food

Baby birds appear to be pretty helpless creatures, cheeping incessantly and stretching their featherless necks out of the nest to get food plopped directly in their mouths. But when hunger strikes and the nest’s cupboards are empty, what’s a baby bird to do? Certain species, like the pied babbler, have figured out a way for young birds to blackmail their caretakers in order to get more food.

All the adults in a pied babbler community share the burden of breeding and feeding their collective offspring. For the first few months of their lives, baby pied babblers rely completely on these adults to keep their tummies full.

Lees meer: Discover

The effect of group size on vigilance in Ruddy Turnstones Arenaria interpres varies with foraging habitat

Fuller, R. A., Bearhop, S., Metcalfe, N. B., Piersma, T. (2013), The effect of group size on vigilance in Ruddy Turnstones Arenaria interpres varies with foraging habitat. Ibis, 155: 246–257. doi: 10.1111/ibi.12020

Abstract

Foraging birds can manage time spent vigilant for predators by forming groups of various sizes. However, group size alone will not always reliably determine the optimal level of vigilance. For example, variation in predation risk or food quality between patches may also be influential. In a field setting, we assessed how simultaneous variation in predation risk and intake rate affects the relationship between vigilance and group size in foraging Ruddy Turnstones Arenaria interpres. We compared vigilance, measured as the number of ‘head-ups’ per unit time, in habitat types that differed greatly in prey energy content and proximity to cover from which predators could launch surprise attacks. Habitats closer to predator cover provided foragers with much higher potential net energy intake rates than habitats further from cover. Foragers formed larger and denser flocks on habitats closer to cover. Individual vigilance of foragers in all habitats declined with increasing flock size and increased with flock density. However, vigilance by foragers on habitats closer to cover was always higher for a given flock size than vigilance by foragers on habitats further from cover, and habitat remained an important predictor of vigilance in models including a range of potential confounding variables. Our results suggest that foraging Ruddy Turnstones can simultaneously assess information on group size and the general likelihood of predator attack when determining their vigilance contribution.

Blue Tits Provide Insight Into Climate Change, Bird Study Shows

Researchers believe that the size of birds' nests created in response to changing weather patterns may be partly to blame for reproductive failures over the last two years.

An article in the April edition of The Biologist, the Society of Biology's magazine, explains that birds produce different sized nests depending on the weather. Written by Dr Charles Deeming, senior lecturer at the University of Lincoln and a Fellow of the Society of Biology, the article explains that nests are far more than just a way to hold eggs and chicks.

Lees meer: ScienceDaily