Researchers call out to lovers of bird song

What happens when we hear a bird? That is the question at the heart of a new research project launched this week at the University of Aberdeen.

Lees meer: PhysOrg.com

Exterior nest-boxes may negatively affect Barn Owl Tyto alba survival: an ecological trap

Auteur(s): Klein, A (Klein, Akos), Nagy, T (Nagy, Tibor), Csorgo, T (Csorgo, Tibor), Matics, R (Matics, Robert)
Bron: BIRD CONSERVATION INTERNATIONAL 17 (3): 273-281 SEP 2007
Abstract: Nest-site reduction has played a significant role in the decline of Barn Owl Tyto alba populations throughout Europe and North America. Techniques of nest-site augmentation, involving the provision of nest-boxes, have been widely used in a range of species of conservation concern, including falcons, eagles, parrots, owls and cavity-nesting ducks.
A common method of Barn Owl conservation is the placement of nest-boxes on church towers. Despite the usefulness of nest-boxes, several studies have shown that there may be associated disadvantages and that nestboxes may even act as 'ecological traps'. The purpose of this research was to compare the survival rate of owlets hatched in nest-boxes with those hatched in the more "natural" environment of church towers.
Survival time analysis elucidated that owlets developing in nest-boxes had significantly lower survival than those hatched in church towers. This difference was most obvious after the parent-dependent period of the life history. Surprisingly, the length of time from hatching to the onset of winter had no effect on the survival of the owlets, even though the accumulation of sufficient body reserves and acquisition of hunting experience are thought to be important in determining survival during the critical first winter of life.
We propose possible causes for the negative effects of nest-boxes and recommend some modifications to the priorities of Barn Owl Action Plans, e.g. partial reopening of buildings instead of nest-box installation.
This paper emphasizes the importance of considering revision of Species Action Plans in the case of other endangered species where conservation is based on nest-site supplement (e.g. hornbills, cavity-nesting seabirds, European Roller Coracias garrulus, Little Owl Athene noctua, Saker Falcon Falco cherrug, White Stork Ciconia ciconia).

Ecologists Discover City Is 'Uber-forest' For Big Owls

Charlotte has a spooky secret: the North Carolina city is home to a robust population of very large barred owls -- a species long-believed by ornithologists to require old growth forest for survival. According to ecologists doing the most extensive field study ever done on the species, the owls see urban life as an upgrade on the old woods, and Charlotteans are not at all creeped out by the big birds that share their yards.

Lees meer: Science Daily

In Birds, Expecting To Mate Leads To Higher Fertilization Rates

From an evolutionary perspective, the primary task of an organism is to pass along its genes to future generations. Such genetic transmission is usually assumed to be instinctive. However, a new study shows that species also learn to adapt to their surroundings in order to increase their “reproductive fitness”-- the likelihood that they will successfully reproduce.

Lees meer: Science Daily

'Time-sharing' Tropical Birds Key To Evolutionary Mystery

Whereas most birds are sole proprietors of their nests, some tropical species “time share” together – a discovery that helps clear up a 150-year-old evolutionary mystery, says Biology professor Vicki Friesen.

Lees meer: Science Daily

Wings of the Albatross

Mooie special van National Geographic over de albatros met o.a. video en afbeeldingen over hun fenomenale zweeftechniek

Lees meer: Wings of the Albatross

Adult sex ratios in wild bird populations

Auteur(s): Donald, PF (Donald, Paul F.)
Bron: IBIS 149 (4): 671-692 OCT 2007
Abstract: Offspring sex ratios in wild bird populations, and the extent to which they vary from the equality expected by random genotypic sex determination, have received much recent attention. Adult sex ratios (ASRs) in wild birds, on the other hand, remain very poorly described, and many of the questions about them posed by Ernst Mayr in 1939 remain unanswered. This review assesses population-level sex ratio patterns in wild bird populations, with an emphasis on the ASR. A quantitative assessment of over 200 published estimates of ASR, covering species from a wide range of taxa, regions and habitats, supported Mayr's assertion that skewed ASRs are common in wild bird populations. On average, males outnumbered females by around 33%, and 65% of published estimates differed significantly from equality. In contrast, population-level estimates of offspring sex ratio in birds did not generally differ from equality, and mean ASR across a range of wild mammal species was strongly female-skewed. ASR distortion in birds was significantly more severe in populations of globally threatened species than in non-threatened species, a previously undescribed pattern that has profound implications for their monitoring and conservation. Higher female mortality, rather than skewed offspring sex ratio, is the main driver of male-skewed ASRs in birds, and the causes and implications of this are reviewed. While estimates of ASR in wild bird populations may be subject to a number of biases, which are discussed, there is currently no quantitative evidence that an ASR of one male to one female represents the norm in birds. A better understanding and reporting of ASRs in wild bird populations could contribute greatly to our understanding of population processes and could contribute much to theoretical and applied research and conservation.

Interactive effects of food and age on breeding in the Montagu's Harrier Circus pygargus

Auteur(s): Arroyo, BE (Arroyo, Beatriz E.), Bretagnolle, V (Bretagnolle, Vincent), Leroux, A (Leroux, Alain)
Bron: IBIS 149 (4): 806-813 OCT 2007
Abstract: We evaluated the direct and interactive effects of food and age on reproduction in the Montagu's Harrier Circus pygargus, to test whether variation in food supply was likely to affect age-specific breeding probability or success. Younger females were more frequently non-breeders than older females. When breeding, older females laid earlier, produced larger clutches, failed less often and had higher number of fledglings than younger females. Probability of breeding was higher, laying was earlier, and clutch size and number of fledglings per pair increased with increasing food abundance. A significant interaction between food and age was observed in both breeding probability and breeding performance: older females were more likely to breed than younger females when food abundance was low, and younger females performed less well in good food conditions than older females. Overall, differences between age groups were most marked in extreme food conditions, regardless of the quality of the conditions.

Earliest Birds Acted More Like Turkeys Than Common Cuckoos

The earliest birds acted more like turkeys than common cuckoos, according to a new report. By comparing the claw curvatures of ancient and modern birds, the researchers provide new evidence that the evolutionary ancestors of birds primarily made their livings on the ground rather than in trees.

Lees meer: Science Daily

For migrating sparrows, kids have a compass, but adults have the map

Even bird brains can get to know an entire continent -- but it takes them a year of migration to do so, suggests a Princeton research team.

Lees meer: Biology News Net

When Birds Get Lost, Experience Counts

Migrating adult songbirds that get lost or thrown off-course are much better at getting back on track than juveniles, thanks to internal navigational maps based on previous trips.

Lees meer: Live Science

Bird night attacks may be unique

Incidents of a seabird preying on colonies of another species at night may be unique to a remote islands archipelago.

Lees meer: BBC NEWS

Female lesser kestrel (falco naumanni) also accepts extra-pair copulation

Auteur: Penades, GC (Penades, Gustau Calabuig)
Bron: JOURNAL OF ORNITHOLOGY 148 (4): 563-564 OCT 2007
Abstract: The lesser kestrel (Falco naumanni) is considered a socially monogamous species in which extra-pair copulation occurs at a low rate. A wide study of extra-pair mating behaviour carried out on this species found that mated females do not solicit extra-pair copulation and reject all copulation attempts elicited by extra-pair males. In fact, the infrequent instances of extra-pair fertilization found were attributed either to re-mating after divorce, or polygyny. Here I describe an observation indicating that females also promote and accept promiscuous mating, attaining and consummating extra-pair copulation. I suggest the possibility that promiscuous behaviour could vary among different populations in this species, as it has not yet been reported, in spite of the extensive work performed in this respect.

'Nervous' Birds Take More Risks

Scientists have shown that birds with higher stress levels adopt bolder behaviour than their normally more relaxed peers in stressful situations

Lees meer: ScienceDaily

Birds Navigate Using Magnetic Compass-Vision

For decades, scientists have known that migratory birds use Earth’s geomagnetic field—along with light, stars, and other cues—to guide them on remarkably long journeys. But it is unclear just how birds sense this relatively weak field and use it for navigation.

Lees meer: Discover Magazine