Sparrows solve problems more quickly in larger groups

For many animals, living with others has obvious benefits. Social animals can hunt in packs, gain safety in numbers or even learn from each other. In some cases, they can even solve problems more quickly as a group than as individuals. That's even true for the humble house sparrow - Andras Liker and Veronika Bokony from the University of Pannonia, Hungary, found that groups of 6 sparrows are much faster at opening a tricky bird feeder than pairs of birds.

After ruling out several possible explanations, the duo put the speedy work of the bigger flock down to their greater odds of including boffin birds. Individual sparrows vary greatly in terms of their skills, experiences and personalities. Larger groups are more likely to include the sharpest bird brains, or several diverse individuals whose abilities complement each other.


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The importance of pre-thicket conifer plantations for nesting Hen Harriers Circus cyaneus in Ireland

Auteurs: MARK W. WILSON, SANDRA IRWIN, DAVID W. NORRISS, STEPHEN F. NEWTON, KEVIN COLLINS, THOMAS C. KELLY, JOHN O'HALLORAN
Bron: IBIS Volume 151 Issue 2, Pages 332 - 343
Abstract: Hen Harriers Circus cyaneus are threatened across much of their range and their conservation requires appropriate habitat management. The locations of 148 Hen Harrier nests found in the Republic of Ireland during national breeding surveys in 2000 and 2005 were used to assess nest-site selection. The distribution of these nests was compared to distributions of randomly located points to investigate selection at the scale of the nest-site and landscape. The main nesting habitats selected were pre-thicket stage of first and, particularly, second rotation plantations, mostly of exotic conifers.
There was no evidence that the area of post-closure plantations negatively affected Hen Harrier nest distribution. There was a positive correlation across study areas between changes in numbers of Hen Harrier nests between 2000 and 2005 and changes in the area of pre-thicket second rotation plantations over the same period. The overall effect of plantation forests on breeding Hen Harriers in Ireland therefore appears to be positive.
However, this study did not consider the effects of plantation habitats on breeding success. Improved grassland was strongly avoided as a nesting habitat.
Furthermore, after controlling for the influence of nesting habitat on nest location, landscapes with a high percentage cover of improved grassland were also avoided. Further agricultural intensification of grassland in areas where Hen Harriers breed is likely to have a negative impact on this species.
These results are required for the development of management strategies for the conservation of this species.

Diet specificity is not associated with increased reproductive performance of Golden Eagles Aquila chrysaetos in Western Scotland

Auteurs: D. P. WHITFIELD, ROBIN REID, PAUL F. HAWORTH, MIKE MADDERS, MICK MARQUISS, RUTH TINGAY, ALAN H. FIELDING
Bron: IBIS, Volume 151 Issue 2, Pages 255 - 264
Abstract: Amongst raptor species, individuals with specialized diets are commonly observed to have higher reproductive output than those with general diets. A suggested cause is that foraging efficiency benefits accrue to diet specialists. This diet specificity hypothesis thus predicts that diet breadth and reproductive success should be inversely related within species. We highlight, however, that a prey availability hypothesis also makes the same prediction in some circumstances. Hence, when high diet specificity results from high encounter rates with an abundant, preferred prey, then prey availability may affect reproductive success, with diet specialization as an incidental correlate.
Using three insular study areas in western Scotland, we examine diet specificity and reproductive success in Golden Eagles Aquila chrysaetos. Diet breadth and breeding productivity were not negatively related in any of our study areas, even though birds with specific diets did tend to have a higher incidence of preferred prey (grouse and lagomorphs) in the diet. Indeed, in two study areas there was evidence that diet generalists had higher breeding productivity. Our results therefore failed to support the diet specificity hypothesis but were consistent with the prey availability hypothesis.
We highlight that although many other studies are superficially consistent with the diet specificity hypothesis, our study is not alone in failing to provide support and that the hypothesis does not provide a generic explanation for all relevant results. Diet specificity in predators can be at least partially a response to prey diversity, availability and distribution, and benefits associated with different prey types, so that being a generalist is not necessarily intrinsically disadvantageous.
We suggest that the available evidence is more consistent with variation in prey abundance and availability as a more influential factor explaining spatial and temporal variation in breeding productivity of 'generalist' species such as the Golden Eagle. Under this argument, prey abundance and availability are the main drivers of variation in reproductive output. Diet specificity is a consequence of variation in prey availability, rather than a substantial cause of variation in reproductive success.

Birds Can 'Read' Human Gaze

We all know that people sometimes change their behavior when someone is looking their way. Now, a new study reported online on April 2nd in Current Biology shows that jackdaws—birds related to crows and ravens with eyes that appear similar to human eyes—can do the same.

"Jackdaws seem to recognize the eye's role in visual perception, or at the very least they are extremely sensitive to the way that human eyes are oriented," said Auguste von Bayern, formerly of the University of Cambridge and now at the University of Oxford.


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