Fashion Found Fleeting in Birds

Females are thought to have simple desires in the animal kingdom — showy tail feathers, big horns, maybe a catchy song — so males tend to exaggerate such ornaments to outdo their competitors.

But now it seems trendiness plays a role. What is sexy among male songbirds on the Great Plains, whether it be flamboyant plumage or a large beak, changes depending on what females consider fashionable that year, new research shows.

These findings shed new light on how the battle of the sexes can ultimately shape a species.


Lees meer: LiveScience

Selection of nesting habitat by Montagu's Harriers Circus pygargus and Hen Harriers Circus cyaneus in managed heaths

Auteur(s): Cormier, Jean-Paul, Fustec, Joelle, Pithon, Josephine, Choisy, Patrice
Bron: BIRD STUDY, Volume 55, Number 1, 1 March 2008 , pp. 86-93(8)
Abstract:

Aims To investigate relationships between vegetation structure and nest selection by Montagu's and Hen Harriers.

Methods We defined three vegetation strata: upper, intermediate and lower. Height and cover of plant species in each stratum were recorded in a 9-m² area centred on nests or unused random points. Statistical analysis was performed to reveal predictors for classifying plots (i) with a Montagu's Harrier nest, (ii) with a Hen Harrier nest and (iii) without a nest.

Results Montagu's Harriers selected places where tree cover was less than 25%, the maximum height of the upper stratum was 1.87 m, and the cover of the intermediate stratum was greater than 75%. Hen Harriers nested either in plots where the upper stratum was higher than 1.87 m, or where tree coverage was greater than 25%.

Conclusions To encourage the breeding of Montagu's Harriers, the planting of pine should be avoided and the heath should be rejuvenated before it reaches 1.80 m in height. For Hen Harriers, certain plots of heath higher than 2 m should be kept. In agricultural landscapes, patches of managed shrubland or heathland could help conservation of both species.

Diffuse, short and slow migration among Blue Tits

Auteur(s): Anna L. K. Nilsson, Thomas Alerstam, Jan-Åke Nilsson
Bron: JOURNAL OF ORNITHOLOGY, Online First, DOI 10.1007/s10336-008-0280-3
Abstract: The knowledge of migration systems in long-distance regular migrants is in many cases extensive. Our understanding of the migratory characteristics of partial migrants, on the other hand, is far more rudimentary. We investigated migratory characteristics of partially migratory Blue Tits Cyanistes caeruleus using ringing recoveries of Swedish birds, to answer questions about geographic migration patterns, age-specific migrations, migration speeds and synchrony of movements. Median migration distance of Swedish Blue Tits was 82 km, with a main autumn direction in the sector between S and W (large directional scatter). Northerly and southerly populations did not differ in migration directions or distances, suggesting chain migration to be the general pattern. A larger proportion of adult Blue Tits remained near the breeding grounds during winter than was the case for juveniles. Some of the migrating birds (17%) seemed not to return in spring but stayed to breed closer to the winter area. Swedish Blue Tits show an exceptionally slow migration speed (median 13 km/day), among the slowest speeds recorded for any migrant bird. The Blue Tit represents an extreme case of diffuse, short and slow bird migration.

Rat Invasions Causing Seabird Decline Worldwide

Invasive rats on ocean islands are threatening the survival of many of the world's seabirds, according to a new report.

The global analysis found that non-native rats have been observed preying on roughly a quarter of all seabird species, often with disastrous consequences.

The voracious rodents attack bird nesting colonies, eating eggs, chicks, and sometimes even adult birds.

Now 102 of 328 recognized seabird species are considered threatened or endangered by the World Conservation Union, with predation by invasive species ranking among the top dangers.

Lees meer: National Geographic

Tropical winter habitat drives natal dispersal of young migratory birds

A new study by scientists at the Migratory Bird Center at the Smithsonian's National Zoo shows that the factors determining where birds settle and nest in the first breeding season depends on the habitat they used during their first winter in the tropics. The determining factor in where a bird settles for its first breeding season relative to its hatching site—also known as natal dispersal—was previously unknown.

By studying American redstarts, National Zoo scientists have shed light on the phenomenon that has important implications for rates of genetic differentiation. The study was published online in the Feb. 18 issue of the Proceedings of the National Academy of Sciences.

Lees meer: Physorg.com

Foraging ecology and reproductive biology of the Stonechat Saxicola torquata : comparison between a revitalized, intensively cultivated and a historic

Auteur(s): Emmanuel Revaz, Michael Schaub, Raphaël Arlettaz
Bron: JOURNAL OF ORNITHOLOGY, Online First DOI 10.1007/s10336-007-0269-3
Abstract: An effective strategy to reintegrate biodiversity within otherwise intensively cultivated agroecosystems is to create set-aside and wildflower areas. It remains largely unknown, however, whether the ecological performance of an agroecosystem revitalized in this manner is comparable—from a species' population biology perspective—to traditionally exploited farmland. To address this question we compared, during two successive years, the trophic ecology and breeding performance of an insectivorous, indicator passerine (the Stonechat Saxicola torquata) in a revitalized intensively cultivated farmland (RIC) and a traditional, extensively cultivated farmland (TEC) in southern Switzerland. The chicks' diet and prey abundance did not differ between the RIC and TEC, with orthopterans, caterpillars (Lepidoptera) and coleopterans predominating (approx. 80% of diet biomass). Although Stonechat pairs initiated more broods in TEC than in the RIC, reproductive success (number of fledglings/territory × year) did not differ significantly between the TEC and RIC. The chicks' condition (body mass) was slightly better in TEC than in RIC, while no such effect could be shown for chick constitution (tarsus length) in either year. The inter-site (RIC vs. TEC) variation fell well within the inter-annual variation of breeding parameters, indicating that environmental stochasticity could be a greater determinant of reproductive output and young quality than agroecosystem type. Although in need of replication, these results suggest that incentives for setting aside farmland and creating wildflower areas within agroecosystems may not only enhance plant and invertebrate diversity, as has been demonstrated earlier, but can also support functioning populations of vertebrates situated at higher trophic levels along the food chain.

Parent-offspring conflict over duration of parental care and its consequences in tawny owls Strix aluco

Auteur(s): Peter Sunde
Bron: JOURNAL OF AVIAN BIOLOGY (OnlineEarly Articles).
doi:10.1111/j.2008.0908-8857.04194.x
Abstract: In species defending territories, fitness of newly independent juveniles could depend on phenotypic quality or early access to vacant resources as a result of rapid dispersal. In the first case, parent-offspring conflict will arise when parents cease feeding maturing offspring while these still demand provisioning. In the latter case, the young should decide when to stop begging to search for vacant territories. I radio-tracked 72 juvenile tawny owls from independence to sexual maturity to investigate whether parents or offspring decided the timing of the onset of independence and compare effects of age versus date of independence on survival and reproductive status. Juvenile owls stopped begging when 90–123 d old. This was synchronous within broods, independent of gender or age rank. Independence age of cross-fostered young varied across foster nests but was independent of hatching nest. After independence, young roosted in their parents' territory for 18 d on average before dispersal. This suggests that juvenile owls would rather extend dependency than disperse early. As predicted from this behaviour, age of independence had a positive influence on survival and reproductive status at maturity, whereas there were no effects of date of independence.

Migrating birds detect latitude and longitude, but how remains a mystery

Eurasian reed warblers captured during their spring migrations and released after being flown 1,000 kilometers to the east can correct their travel routes and head for their original destinations, researchers report online on January 31st in Current Biology, a publication of Cell Press.

The new evidence suggests that the birds have true navigation, meaning that they can identify at least two coordinates that roughly correspond to geographic latitude and longitude

Lees meer: Biology News Net

It's OK to Feed Birds

Keep feeding the birds over winter: that's the message from research by the University of Exeter and Queen's University Belfast. The study shows for the first time that the extra food we provide garden birds in winter makes for a more successful breeding season in the spring.

Lees meer: Science Daily - LiveScience

White storks Ciconia ciconia eavesdrop on mating calls of moor frogs Rana arvalis

Auteur(s): Kristīne Igaune, Indriķis Krams, Tatjana Krama, Jadviga Bobkova
Bron: JOURNAL OF AVIAN BIOLOGY (OnlineEarly Articles)
Abstract: Mating calls of animals are often detected by unintended receivers which use sexual signals to obtain information about the signaller. We investigated whether white storks Ciconia ciconia can eavesdrop mating calls of moor frogs Rana arvalis.
White storks are dependent on moor frog abundance in early breeding
season. Interspecific eavesdropping by predators is common and well
documented in tropical anurans, whereas it is less known in temperate
zone. We compared the frequency of approaches of white storks to
loudspeakers when frog calls and the song thrush Turdus philomelos
songs were simultaneously played back using the later as controls. The
loudspeaker broadcasting the calls of male moor frogs clearly attracted
white storks at 22 out of 84 nests. The bird songs attracted white
storks in only one case. In 19 cases birds left the nest for unknown
reasons which were considered as potential foraging movements. The
results of this field experiment report a new case of eavesdropping on
acoustic signals showing that advertisement calls of temperate moor
frogs are an important stimulus for white storks.

Large-scale climatic phenomena and timing of breeding in a local population of the Osprey in southern Finland

Auteur(s): T. Solonen
Bron: JOURNAL OF ORNITHOLOGY online article 29 January 2008
Abstract: The effects of large-scale climatic phenomena on the timing of breeding in the Osprey Pandion haliaetus were studied during 1981–2006 in a small local population of about 20 pairs near the southern coast of Finland. The timing of breeding was estimated on the basis of the wing length of the largest young within the brood. The wing lengths were plotted against the date of the measurement to get a linear regression model characterizing the average developmental stage of broods in relation to date. This model was used when converting the measurements to correspond to the median date of all the measurements. Large-scale climatic phenomena were characterized by the winter and monthly indices of the North Atlantic oscillation (NAO). A significant positive relationship between the winter NAO index and timing of breeding in the Osprey, as indicated by the wing length of the largest young in the brood, was found. The relationship was even stronger when only the monthly value of January was considered. These relationships seemed to be linked with consequent earlier ice melting after mild winters. The results indicate prominent effects of large-scale climatic phenomena and that they can be monitored with relatively modest effort.