Soaring is better than flapping for birds big and small

Small migrating birds save energy as they fly. Large birds, such as storks, save energy on the flight to their wintering grounds by soaring through the air on thermal currents. Until now, however, we knew nothing about the flight patterns of small migrating songbirds, such as whether they flap their wings or soar and whether these styles of flight allow them to save energy. Now, a team of scientists at the Max Planck Institute for Ornithology in Radolfzell, Ben-Gurion-University of the Negev, and Hebrew University of Jerusalem have tracked the movement of European bee-eaters (Merops apiaster) along the Africa-Eurasia migration flyway with the help of tiny radio transmitters.

Lees meer: SciendeDaily

Bird-Brained? Birds' Personalities Are Correlated With Their Hormone Levels

Any dog or cat owner will agree that animals have personalities but it may come as a surprise to many to learn that birds also do. As an example, individual birds vary in their levels of curiosity, with distinctions being made between “fast” and “slow” explorers. A considerable body of research has examined the differences between fast and slow birds but the levels of stress hormones (glucocorticoids) have not previously been investigated, although these hormones are known to be important in a number of aspects of bird behaviour.

Lees meer: ScienceDaily

How birds see magnetic fields - An interview with Klaus Schulten

It’s now winter in Europe and many small birds are well on their way to warmer climes, migrating over large tracts of land in search of better weather. Along the way, they keep their course with a remarkable supersense – the ability to sense magnetic fields.

Lees meer: Not Exactly Rocket Science | Discover Magazine

Experimental evidence for interference competition in oystercatchers, Haematopus ostralegus. II. Free living birds

Auteurs: Anne L. Rutten, Kees Oosterbeek, Simon Verhulst, Niels J. Dingemans, Bruno J. Ens
Bron: BEHAVIORAL ECOLOGY, Volume 21, Issue 6 p. 1261-1270
Abstract: Field studies of interference competition in free-living animals have relied on natural fluctuations in forager density, which are often confounded with other factors. We therefore experimentally studied interference in the wild, capitalizing on 2 cockle beds in an isolated bay that were exploited by a population of individually marked oystercatchers. We successfully increased forager density by chasing birds from one cockle bed, leaving the other cockle bed as the only nearby alternative. The density increase was most pronounced on the eastern cockle bed where food stocks were poorer and initial feeding densities were lower compared with the western cockle bed. Oystercatchers residing on this eastern bed suffered a significant decline in intake rate when bird density was experimentally increased, providing evidence of interference. “Refugee” birds, that is, the birds that were displaced from their home bed, experienced an even stronger reduction in intake rate compared with the residents and compared with their intake rate on their “home bed,” probably partly due to the fact that the refugee birds were forced to feed on an unfamiliar cockle bed. The fact that disturbance at 1 site influenced both the refugees and the local resident birds indicates that human disturbance (an important conservation issue) has an effect that extends beyond the site where the disturbance takes place. The benefits and costs of site fidelity and interference competition are likely to play an important role in understanding animal distributions and how they change in response to environmental perturbations, including human disturbance of foraging sites.

Experimental evidence for interference competition in oystercatchers, Haematopus ostralegus. I. Captive birds

Auteurs: Anne L. Rutten, Kees Oosterbeek, Jaap van der Meer, Simon Verhulst, Bruno J. Ens
Bron: BEHAVIORAL ECOLOGY, Volume 21, Issue 6 p. 1251-1260
Abstract: Interference competition, the immediately reversible decrease in per capita foraging success with increasing forager density, has important implications for the distribution of foragers. Theoretical models predict the strength of interference at different prey densities for birds differing in dominance. Observational studies have been used to validate the theoretical predictions, but there is reason to believe that these nonexperimental studies suffer from confounding factors. We therefore manipulated forager density of oystercatchers Haematopus ostralegus foraging on live cockles Cerastoderma edule (low density: 1 bird per 50 m2 and high density: 2 birds per 50 m2) in a unique experimental facility closely mimicking natural feeding conditions. In the high-density situation, the intake rate was on average reduced by 36% compared with the interference-free intake rate. However, this effect depended on status with intake rate of subordinates being more strongly reduced than intake rate of dominants (-45% vs. -25%). We could not investigate all possible mechanisms, but we observed that birds actively avoided each other, possibly to avoid kleptoparasitism. Our experiment shows that the decline in intake rate with increasing density of conspecifics is at least partly due to direct interactions between birds and possibly also to indirect interactions via prey depression but not to an unidentified confounding factor that covaries with intake rate and bird density, as may have been the case in nonexperimental field studies.

What Male Owls Want: Big Spots

"What nice spots you have" could apparently be a barn owl pickup line. A new study found that female barn owls with larger spots seem to up their sexy quotient, and have greater success in mating.

Perplexingly, the same trait — large dark spots on the tips of the white feathers covering the owl's body — appears to hurt male barn owls' reproductive success.

Lees meer: LiveScience

Long-tailed Tits help close kin

The Long-Tailed Tit has unusual breeding behaviour with failed breeders often assisting with the raising of a brood belonging to a pair that is closely related to them. A new study throws light on this arrangement.

If a pair fails early in the season they may try to breed again, but if it is too late for this, then the failed breeders may help out another closely related pair by bringing food. Individuals seem to be able to recognise their kin by their contact calls.

Lees meer: Birdwatch

Researchers Crack Cuckoo Egg Mystery

Researchers at the University of Sheffield have discovered that cuckoo eggs are internally incubated by the female bird for up to 24 hours before birth, solving for the first time the mystery as to how a cuckoo chick is able to hatch in advance of a host´s eggs and brutally evict them.

Published September 22, 2010 in the journal Proceedings of the Royal Society of London, Series B, the research shows that internal incubation allows the cuckoo chick to hatch before its nest mates, evict them, and monopolise the food brought by the foster parents.

Although previous studies have suggested early hatching is achieved partly through the cuckoo producing a small egg which develops faster, it has long been suspected that there might be another reason for this.

Lees meer: ScienceDaily

Night Light Pollution Affect Songbirds' Mating Life, Research Suggests

In today's increasingly urbanized world, the lights in many places are always on, and according to a report published online on September 16 in of Current Biology, a Cell Press publication, that's having a real impact on the mating life of forest-breeding songbirds.

"In comparison to chemical and noise pollution, light pollution is more subtle, and its effects have perhaps not received the attention they deserve," said Bart Kempenaers of the Max Planck Institute for Ornithology in Germany. "Our findings show clearly that light pollution influences the timing of breeding behavior, with unknown consequences for bird populations."

The researchers investigated the effects of artificial night lighting on dawn song in five common forest-breeding songbirds. In four of those five species, males near street lights started singing significantly earlier in the morning than did males in other parts of the forest.

Lees meer: ScienceDaily

Communication across territory boundaries: distance-dependent responses in nightingales

Auteurs: Philipp Sprau, Tobias Roth, Rouven Schmidt, Valentin Amrhein, Marc Naguib
Bron: BEHAVIOURAL ECOLOGY, Volume 21, Issue 5, p. 1011-1017
Abstract: In communication, vocal signals are often used for long-range signaling. Yet, little experimental evidence is available on the role of territorial signals across territory boundaries and their effectiveness at different propagation distances. In many songbird species, song overlapping and rapid broadband trills are used and perceived as agonistic signals, yet they differ in their propagation distance. Trills degrade quickly over distance, suggesting that their agonistic function may decrease faster over distance than that of song overlapping. Here, we tested whether different signaling distances of a rival affect singing responses of a territorial male and whether such distance effects differ when a rival uses rapid broadband trills or song overlapping. We exposed male nightingales (Luscinia megarhynchos) to songs of simulated rivals broadcast from 2 distances outside their territories. Each subject was exposed either to a moderate alternating playback without trills or to an agonistic playback, that is, to an alternating playback with trills or to an overlapping playback without trills. Irrespective of the treatment, males sang more songs containing trills in response to near than to far playback. As expected, males responded more strongly to the 2 agonistic treatments than to the moderate treatment. However, males did not clearly decrease responsiveness to playback containing trills broadcast from afar. This indicates that trills maintain their agonistic function even at distances at which information encoded in frequency bandwidth is degraded. Taken together, our results show that information encoded in signals used for resource maintenance is important also in communication across territory boundaries. 

Why It's OK for Birds to Be Gay

In greylag geese, nearly a fifth of all long-term couples are composed of two males. They're not alone: More than 130 bird species are known to engage in homosexual behavior at least occasionally, a fact that has puzzled scientists.

After all, in evolutionary terms same-sex mating seems to reduce the birds' chances of reproductive success. But that's not necessarily so, according to a new study. In a given species, the sex with lighter parental duties tends to mate more, period — whether with the same or the opposite sex.

Lees meer: LiveScience

Eggshells Look More Colorful Through the Eyes of Birds

Birds see a more colorful world than we do, especially when it comes to their eggs, a new study suggests.

Unlike humans, birds can see ultraviolet (UV) light, and they have four – rather than three – color receptors in their eyes, allowing them to better distinguish between hues.

Now researchers have shown that while most of the color variation in eggshells can be seen by humans and birds alike, a swath of hues that our eyes miss may play an important role in avian life. For instance, we are oblivious to the UV pigment that may help birds differentiated between their own eggs and those of another species.

Lees meer: LiveScience

Population overlap and habitat segregation in wintering Black-tailed Godwits Limosa limosa

Auteurs: Jose A. Alves, Pedro M. Lourenco, Theunis Piersma, William J. Sutherland, Jennifer A. Gill
Bron: BIRD STUDY, Volume 57, Issue 3 August 2010, pages 381-391
Abstract:

Capsule Distinct breeding populations of migratory species may overlap both spatially and temporally, but differ in patterns of habitat use. This has important implications for population monitoring and
conservation.

Aims To quantify the extent to which two distinct breeding populations of a migratory shorebird, the Black-tailed Godwit Limosa limosa, overlap spatially, temporally and in their use of different habitats during winter.

Methods We use mid-winter counts between 1990 and 2001 to identify the most important sites in Iberia for Black-tailed Godwits. Monthly surveys of estuarine mudflats and rice-fields at one major site,
the Tejo estuary in Portugal in 2005-2007, together with detailed tracking of colour-ringed individuals, are used to explore patterns of habitat use and segregation of the Icelandic subspecies L. l. islandica and the nominate continental subspecies L. l. limosa.

Results In the period 1990-2001, over 66 000 Black-tailed Godwits were counted on average in Iberia during mid-winter (January), of which 80% occurred at just four sites: Tejo and Sado lower basins in
Portugal, and Coto Donana and Ebro Delta in Spain. Icelandic Black-tailed Godwits are present
throughout the winter and forage primarily in estuarine habitats. Continental Black-tailed Godwits are present from December to March and primarily use rice-fields.

Conclusions Iberia supports about 30% of the Icelandic population in winter and most of the continental population during spring passage. While the Icelandic population is currently increasing, the continental population is declining rapidly. Although the estuarine habitats used by Icelandic godwits are largely protected as Natura 2000 sites, the habitat segregation means that conservation actions for the
decreasing numbers of continental godwits should focus on protection of rice-fields and re-establishment of freshwater wetlands.

Warbler Fight Songs Follow Fashion While Love Songs Stick to a Few Classics

A team of researchers has found that chestnut-sided warblers possess two distinct cultural traditions in song variants that evolve independently -- one, used for territorial disputes that changes frequently, and another, used for romance that relies on a small unchanging sampling of classics. The findings suggest songbird culture is more complex than previously thought, the scientists say. The paper will be published in the journal The American Naturalist.

Lees meer: ScienceDaily

Predation Danger Can Explain Changes in Timing of Migration: The Case of the Barnacle Goose

Auteurs: Rudy M. Jonker, Götz Eichhorn, Frank van Langevelde, Silke Bauer
Bron: PLoS ONE 5(6): e11369. doi:10.1371/journal.pone.0011369
Abstract:
Understanding stopover decisions of long-distance migratory birds is crucial for conservation and management of these species along their migratory flyway. Recently, an increasing number of Barnacle geese breeding in the Russian Arctic have delayed their departure from their wintering site in the Netherlands by approximately one month and have reduced their staging duration at stopover sites in the Baltic accordingly. Consequently, this extended stay increases agricultural damage in the Netherlands. Using a dynamic state variable approach we explored three hypotheses about the underlying causes of these changes in migratory behavior, possibly related to changes in (i) onset of spring, (ii) potential intake rates and (iii) predation danger at wintering and stopover sites. Our simulations showed that the observed advance in onset of spring contradicts the observed delay of departure, whereas both increased predation danger and decreased intake rates in the Baltic can explain the delay. Decreased intake rates are expected as a result of increased competition for food in the growing Barnacle goose population. However, the effect of predation danger in the model was particularly strong, and we hypothesize that Barnacle geese avoid Baltic stopover sites as a response to the rapidly increasing number of avian predators in the area. Therefore, danger should be considered as an important factor influencing Barnacle goose migratory behavior, and receive more attention in empirical studies.

Lees meer: PLoS ONE

Robins can literally see magnetic fields, but only if their vision is sharp

Some birds can sense the Earth’s magnetic field and orientate themselves with the ease of a compass needle. This ability is a massive boon for migrating birds, keeping frequent flyers on the straight and narrow. But this incredible sense is closely tied to a more mundane one – vision. Thanks to special molecules in their retinas, birds like the European robins can literally see magnetic fields. The fields appear as patterns of light and shade, or even colour, superimposed onto what they normally see.

Katrin Stapput from Goethe University has shown that this ‘magnetoreception’ ability depends on a clear image from the right eye. If the eye is covered by a translucent frosted goggle, the birds become disorientated; if the left eye is covered, they can navigate just fine. So the robin’s vision acts as a gate for its magnetic sense. Darkness (or even murkiness) keeps the gate shut, but light opens it, allowing the internal compass to work.

Lees meer: Not Exactly Rocket Science | Discover Magazine

7,000 Miles Nonstop, and No Pretzels

In 1976, the biologist Robert E. Gill Jr. came to the southern coast of Alaska to survey the birds preparing for their migrations for the winter. One species in particular, wading birds called bar-tailed godwits, puzzled him deeply. They were too fat.

“They looked like flying softballs,” said Mr. Gill.

At the time, scientists knew that bar-tailed godwits spend their winters in places like New Zealand and Australia. To get there, most researchers assumed, the birds took a series of flights down through Asia, stopping along the way to rest and eat. After all, they were land birds, not sea birds that could dive for food in the ocean. But in Alaska, Mr. Gill observed, the bar-tailed godwits were feasting on clams and worms as if they were not going to be able to eat for a very long time.

Lees meer: NYTimes.com

Cold-blooded mothers: Magpie parents seem to induce mortality of 'unwanted' chicks

Human parents often pay more attention to a few favored children among all of their offspring. It has already been known that birds do it too, and it may result in some baby birds dying in the nests. According to the recent discoveries published in Journal of Avian Biology, the top journal in the field of ornithology, one of our famous garden birds, magpies, also favor some of their nestlings, but in a fairly strange and unique manner.

Lees meer: Biology News Net

Loop migration in adult marsh harriers Circus aeruginosus, as revealed by satellite telemetry

Auteurs: Klaassen RHG, Strandberg R, Hake M, Olofsson P, Tottrup AP, Alerstam T
Bron: JOURNAL OF AVIAN BIOLOGY, Volume: 41, Issue: 2, Pages: 200-207
Abstract: Loop migration among birds is characterized by the spring route lying consistently west or east of the autumn route. The existence of loops has been explained by general wind conditions or seasonal differences in habitat distribution. Loop migration has predominantly been studied at the population level, for example by analysing ring recoveries. Here we study loop migration of individual marsh harriers Circus aeruginosus tracked by satellite telemetry. We show that despite a generally narrow migration corridor the harriers travelled in a distinct clockwise loop through Africa and southern Europe, following more westerly routes in spring than in autumn. We used the Normalized Difference Vegetation Index (NDVI) to identify potential feeding habitat in Africa.
Suitable habitat seemed always more abundant along the western route, both in spring and autumn, and no important stopover site was found along the eastern route. Observed routes did thus not coincide with seasonal variation in habitat availability. However, favourable habitat might be more important during spring migration, when the crossing of the Sahara seems more challenging, and thus habitat availability might play an indirect role in the harriers' route choice.
Grid-based wind data were used to reconstruct general wind patterns, and in qualitative agreement with the observed loop marsh harriers predominantly encountered westerly winds in Europe and easterly winds in Africa, both in autumn and in spring. By correlating tail- and crosswinds with forward and perpendicular movement rates, respectively, we show that marsh harriers are partially drifted by wind. Thus, we tentatively conclude that wind rather than habitat seems to have an overriding effect on the shape of the migration routes of marsh harriers. General wind conditions seem to play an important role also in the evolution of narrow migratory loops as demonstrated for individual marsh harriers.

Migratory Behaviour Affects the Size of Bird Brains

Researchers at Centre for Ecological Research and Forestry Applications (CREAF, a Universitat Autònoma de Barcelona-affiliated centre) shed new light on the evolution of brain size in birds. Scientists have known for some time that migratory birds have smaller brains than their resident relatives. Now a new study looks into the reasons and concludes that the act of migrating leads to a reduced brain size. Authors point to the fact that the causes could be due to a need to reduce energetic, metabolic and cognitive costs. To reach these conclusions, scientists reconstructed the evolutionary history of one of the most numerous orders of birds, the passeriformes, a group which includes swallows, tits and crows.

Understanding brain evolution is something that has interested scientists since the times of Charles Darwin, who considered that the large size of a human brain went hand in hand with the exceptional cognitive capacities of our species. One of the classic explanations is the protective brain theory, which suggests that a large brain -- in comparison to body size -- makes learning easier. This protects individuals from changes in the environment, such as those produced by changes in season. In the case of birds however not all species respond to seasonal changes in the same way. Migratory birds avoid these changes by travelling to less inhospitable places when conditions worsen. This is the strategy followed by swallows or cuckoos. Resident bird species stay in the same area throughout the year and face strong environmental fluctuations. Tits and crows belong to this group.

Lees meer: Science Daily

Reaching independence: food supply, parent quality, and offspring phenotypic characters in kestrels

Auteurs: Pablo Vergara, Juan A. Fargallo, Jesus Martinez-Padilla
Bron: BEHAVIORAL ECOLOGY, 2010 21(3):507-512; doi:10.1093/beheco/arq011
Abstract: The duration of the postfledging dependence period (PFDP) is supposed to be modulated by the parent offspring conflict: Offspring should extract the highest levels of parental investment, although parents may respond by setting fixed limits to the level of investment or by raising the costs of attempts to extract additional investment. In this context, longer PFDPs are expected in nests tended by higher quality parents and in dominant siblings. We explored these hypotheses with a combination of experimental and correlative results. First, we food supplemented offspring during the PFDP to study whether food supply during fledging, an indicator of parental quality, has an effect on the PFDP duration in the Eurasian kestrel. We found that the PFDP was longer in food-supplemented nests. Second, we measured the duration of the PFDP over 3 years under different environmental conditions to explore whether the quality of parents and nestling phenotype were correlated with the duration of PFDP. Correlative results suggest that fledglings raised by higher quality parents and in the year with poorer food conditions showed longer PFDP. Furthermore, male fledglings showing grayer coloration in the rump (an index of competitive capacity) have longer PFDPs than browner males. Overall, our results suggest that parent, rather than offspring characteristics, can modulate the PFDP duration mediated by food conditions, although more colored nestlings stay in the nest territory for longer periods.

Dutch Wadden Sea May Become Bottleneck for Wading Bird

The Dutch Wadden Sea, due to a decline in food resources, may become a bottleneck in the annual cycle of a wading bird known as the knot.

This has been revealed by PhD research by Casper Kraan. He studied two subspecies of the knot, the Calidris canutus islandica and the Calidris canutus canutus.

"It appears that neither species is able to fatten up properly in the Wadden area any more," says Kraan. He conducted his research at the Royal Netherlands Institute for Sea Research (NIOZ) and will be awarded a PhD by the University of Groningen on 26 April 2010.

The islandica breeds on the Canadian and Greenland tundra and then flies to the Wadden area to overwinter. The canutus breeds in Siberia and uses the Wadden Sea to fatten up for the last stage to western Africa. Kraan: "Although the two subspecies have different strategies, they have the same problem -- declining food resources."

Lees meer: Science Daily

Preservation of winter social dominance status in Brent Geese Branta bernicla bernicla within and across winters

Auteurs: Maud Poisbleau, Noel Guillon, Herve Fritz
Bron: JOURNAL OF ORNITHOLOGY, DOI 10.1007/s10336-009-0437-8
Abstract: Dominant and subordinate individuals in a group may benefit from the stability of the social dominance organisation, avoiding excessive waste of time and energy in aggressive interactions and reducing injury risks. Nevertheless, the likely evolutionary incentive for individuals to become, and furthermore to stay, dominant may destabilise such dominance hierarchies. In this context, the relative importance of fixed (e.g. sex, morphological size) and fluctuating (e.g. body condition, mating status, reproductive success, social unit size) traits influencing the establishment and preservation of dominance relationships could play a key role in group structure. We investigated the relative role of fixed and fluctuating traits on social status in Dark-bellied Brent Geese Branta bernicla bernicla which form large fairly unstable groups both within and across winters. We compared individual dominance scores of ringed Brent Geese during four consecutive winters. Brent Geese conserved their dominance score within a given winter irrespective of their age but were generally unable to conserve it across consecutive winters. As winter dominance scores correlated best with social unit size, dominance status thus appeared to be mostly a by-product of a fluctuating trait: breeding success in the previous summer. When we considered only adults that had the same social unit size during two consecutive winters, we observed a significant preservation of dominance scores. This result suggests that a fixed trait such as sex or morphological size may still play a role in setting dominance status.

Advanced departure dates in long-distance migratory raptors

Auteurs: Ondine Filippi-Codaccioni, Jean-Pierre Moussus, Jean-Paul Urcun, Frédéric Jiguet
Bron: JOURNAL OF ORNITHOLOGY, online DOI 10.1007/s10336-010-0500-5
Abstract: Evidences for phenological changes in response to climate change are now
numerous. One of the most documented changes has
been the advance of spring arrival dates in migratory birds. However,
the effects of climate change on subsequent events of
the annual cycle remain poorly studied and understood. Moreover, the
rare studies on autumn migration have mainly concerned
passerines. Here, we investigated whether raptor species have changed
their autumn migratory phenology during the past 30
years at one of the most important convergent points of western
European migration routes in France, the Organbidexka pass,
in the Western Pyrenees. Eight out of the 14 studied raptor species
showed significant phenological shifts during 1981–2008.
Long-distance migrants displayed stronger phenological responses than
short-distance migrants, and advanced their mean passage
dates significantly. As only some short-distance migrants were found to
delay their autumn migration and as their trends in
breeding and migrating numbers were not significantly negative, we were
not able to show any possible settling process of
raptor populations. Negative trends in numbers of migrating raptors
were found to be related to weaker phenological responses.
Further studies using data from other migration sites are necessary to
investigate eventual changes in migration routes and
possible settling process.

Territorial reactions of male Yellowhammers (Emberiza citrinella) toward a specific song structure

Auteurs: Thibaud Gruber, Laurent Nagle
Bron: JOURNAL OF ORNITHOLOGY, Online, DOI 10.1007/s10336-010-0502-3
Abstract: Male songbirds assess their rivals by listening to their songs and, in some species, are especially sensitive to certain parts of the song. Yellowhammers (Emberiza citrinella) sing songs with different structures consisting of an initial phrase of stereotyped and repeated notes in a trill, and a terminal phrase, present or not, which consists of low or high frequency whistles that we called elements. We analyzed 1,055 songs from 25 different males and found that four different structures could be distinguished in a French Yellowhammer population. We found that the frequency ranges of the elements were more constant across individuals than the ranges of the notes, and among them, the low frequency element was nearly twice as conserved as the high frequency element. Then, in the wild, we tested the territorial responses of males to the four different structures and found that the full song structure, which is composed of the initial phrase followed by a high frequency element and a low frequency element, induced stronger territory defence responses from the males than any of the other structures. As only the structure containing the initial phrase and the low frequency element also induced a strong response, we propose that the main element responsible for the enhanced reaction of the males is the low frequency element, which is consistent with the fact that it is more conserved than the other constituents.

Why don't female purple sandpipers perform brood care? A removal experiment

Auteurs: Elin P. Pierce, Lewis W. Oring, Eivin Røskaft, Jan T. Lifjeld
Bron: BEHAVIORAL ECOLOGY, Volume 21, Number 2, p. 275-283
Abstract: In most monogamous sandpiper species, females share parental care
but leave the brood earlier than males, a feature unusual among
birds in general. In the purple sandpiper (Calidris maritima),
females almost always leave the brood at hatching and never share
brood care. Males perform uniparental brood care from hatching
until well after fledging. In this paper, we report the
results of a mate-removal experiment conducted on the purple sandpiper
in high Arctic Svalbard and discuss the implications for the
evolution of their mate desertion strategy. By removing males
from nests near hatching, we tested 2 hypotheses: 1) Males assume
brood care because females, who always have a net benefit from
deserting, have a fixed brood desertion strategy, whereas males
do not; 2) females desert the brood because they cannot perform
uniparental brood care as well as males and/or because they
are under physiological stress at hatching due to egg laying and
incubation activities hypothesis). We found that when experimentally
deserted, most female purple sandpipers assumed brood care. Parental
behavior and the growth and survival of the chicks suggested
that the attending females were not under physiological stress
after hatching and did not seem less able than males to
perform brood care. Thus, we found no support for either hypothesis.
We suggest that uniparental brood desertion is a consequence
of strong selection for uniparental brood care in this
species and that the actual sex roles may result from rather marginal
differences between the sexes in the fitness consequences of
care and desertion.

Do Highly Modified Landscapes Favour Generalists at the Expense of Specialists? An Example using Woodland Birds.

Auteurs: Hinsley Shelley A., Hill Ross A., Bellamy Paul, Broughton Richard K., Harrison Nancy M., Mackenzie Julia A., Speakman John R., Ferns Peter N.
Bron: Landscape Research Oct2009, Vol. 34 Issue 5, p509-526
Abstract: Demands on land use in heavily populated landscapes create mosaic
structures where semi-natural habitat patches are generally small and
dominated by edges. Small patches are also more exposed and thus more
vulnerable to adverse weather and potential effects of climate change.
These conditions may be less problematic for generalist species than for
specialists. Using insectivorous woodland birds (great tits and blue
tits) as an example, we demonstrate that even generalists suffer reduced
breeding success (in particular, rearing fewer and poorer-quality
young) and increased parental costs (daily energy expenditure) when
living in such highly modified secondary habitats (small woods, parks,
farmland). Within-habitat heterogeneity (using the example of Monks Wood
NNR) is generally associated with greater species diversity, but to
benefit from heterogeneity at a landscape scale may require both high
mobility and the ability to thrive in small habitat patches. Modern
landscapes, dominated by small, modified and scattered habitat patches,
may fail to provide specialists, especially sedentary ones, with access
to sufficient quantity and quality of resources, while simultaneously
increasing the potential for competition from generalists

Predators and bird declines

The findings of a new study on the impact of predators on bird prey, which looks at declining species, shows that for most there is no link between increasing predator numbers and falling populations.

The biggest ever analysis of songbirds and their predators, published today (8 March) in the Journal of Applied Ecology, looked at the role of predators in the decline of species such as Bullfinch and Yellowhammer.

The results show that while a small number of associations may suggest significant negative effects between predator and prey species, for the majority of the songbird species examined there is no evidence that increases in common avian predators or Grey Squirrels are associated with large-scale population declines.

Lees meer: Birdwatch

Bird wing shapes changing

New research suggests that the shape of birds’ wings can change over time in response to changes in the environment, especially the fragmentation of forest habitats.

André Desrochers of the Center for Forest Research at Laval University, Quebec has found that as Canada’s vast boreal forest has been cut down over the past century, birds that live in the mature woodlands have developed more pointed wing tips.

Lees meer: Birdwatch

A magnetometer in the upper beak of birds?

Iron containing short nerve branches in the upper beak of birds may serve as a magnetometer to measure the vector of the Earth magnetic field (intensity and inclination) and not only as a magnetic compass, which shows the direction of the magnetic field lines. Already several years ago, the Frankfurt neurobiologists Dr.Gerta Fleissner and her husband Prof. Dr. Günther Fleissner have discovered these structures in homing pigeons and have, in close cooperation with the experimental physicist Dr. Gerald Falkenberg (DESY Hamburg), characterized the essential iron oxides."After we had shown the system of dendrites with distinct subcellular iron-containing compartments in homing pigeons, immediately the question was posed whether similar dendritic systems may be found in other bird species, too", as Gerta Fleissner, the principal investigator, comments. Meanwhile they could describe similar candidate structures in the beaks of various avian species. X-Ray-fluorescence measurements at DESY demonstrated that the iron oxides within these nervous dendrites are identical. These findings were published few days ago in the high-ranking interdisciplinary online journal PlosOne.

Lees meer: Biology News Net

Migrants travel flexibly

A new study shows that migrating birds are able to keep their travel dates flexible, and can respond to the effects of climate change by leaving earlier. However this doesn’t mean that birds will always arrive earlier.

The research, published online in Current Biology, reveals that Pied flycatchers which migrate don’t necessarily reach their destination earlier as they may experience travel delays due to harsh weather conditions on the final leg of their journey through Europe.

Lees meer: Birdwatch

Life-history and ecological correlates of population change in Dutch breeding birds

Auteurs: Chris A.M. Van Turnhout, Ruud P.B. Foppen, Rob S.E.W. Leuven, Arco Van Strien, Henk Siepel
Bron: BIOLOGICAL CONSERVATION Volume 143, Issue 1, Pages 1-266 (January 2010)
Abstract: Predicting relative extinction risks of animals has become a major challenge in conservation biology. Identifying life-history and ecological traits related to the decline of species helps understand what causes population decreases and sets priorities for conservation action. Here, we use Dutch breeding bird data to correlate species characteristics with national population changes. We modelled population changes between 1990 and 2005 of all 170 breeding bird species using 25 life-history, ecological and behavioural traits as explanatory variables. We used multiple regression and multi-model inference to account for intercorrelated variables, to assess the relative importance of traits that best explain interspecific differences in population trend, and to identify the environmental changes most likely responsible. We found that more breeding birds have increased than decreased in number. The most parsimonious models suggest that ground-nesting and late arrival at the breeding grounds in migratory birds are most strongly correlated with decline. Increasing populations are mainly found among herbivores, sedentary and short-distance migrants, herb- and shrub-nesting birds and large species with a small European range. Declines in ground-nesting and late arriving migrant birds suggest that agricultural intensification, eutrophication and climate change are most likely responsible for changes in Dutch breeding bird diversity. We illustrate that management strategies should primarily focus on the traits and causes responsible for the population changes, in order to be effective and sustainable.

Lees ook: Wetenschapsagenda

Birds Follow Their Noses During Migration

Birds largely rely on their sense of smell to navigate on their long migration routes. Indeed, the “third sense” has been shown to be a more important for them than orientation based on the sun and the earth’s magnetic field. Exactly how birds navigate on their migration routes has not yet been fully clarified. How does a bird develop an “internal map”? How does it find its way back to last year’s nest?

Adult migratory birds are clearly able to remember migration routes. Even if they end up flying over unknown terrain, they still manage to find their way to the right place. Researchers at the Max Planck Institute for Ornithology in Radolfzell and their colleagues at the universities of Princeton, Pisa and Copenhagen have established in a field study that odours considerably facilitate bird migration and act as a more important navigational cue than the sun and the earth’s magnetic field.

Lees meer: ScienceDaily

Where Do Puffins Go in the Winter?

A recent increase in winter mortality in Atlantic puffins could be due to worsening conditions within the North Sea, according to new findings published in the scientific journal Marine Biology. The study used geolocation technology to track puffins from the Isle of May National Nature Reserve, home to the largest colony of puffins in the North Sea. The puffin population on the Isle of May has declined by 30% in recent years.

The research team included scientists from the Centre for Ecology & Hydrology and the British Antarctic Survey and was led by Professor Mike Harris, Emeritus Research Fellow at the Centre for Ecology & Hydrology, who has studied puffins for 37 years.

Professor Harris said, "Modern technology has come to the aid of the puffin just when it was needed. The quarter of a million puffins that breed in northeast Britain head out to sea during the winter and we previously thought that they stayed in the North Sea. We now know that some make long trips into the Atlantic during winter. This is vital new knowledge which should help us explain recent declines in puffin numbers."

Lees meer: ScienceDaily

Some Birds Listen, Instead of Look, for Mates

Looks can be deceiving, but certain bird species have figured out that a voice can tell them most of what they need to know to find the right mate.

Andrew DeWoody, a Purdue University associate professor of forestry and natural resources, found that the higher the pitch of a male bird's song, the more genetic diversity that bird has, making him a better mate for breeding. His study was published Dec. 2 in the early online edition of PLoS Biology.

"If you have a diverse set of genes, that can translate into physiology and morphology diversity as well," DeWoody said. "Animals that are heterozygous, or have genetic diversity, are often bigger, stronger or can run faster."

Lees meer: ScienceDaily

Arctic Tern migration revealed

The migration route taken by Arctic Terns through the Atlantic Ocean has been revealed for the first time thanks to small tracking devices that were attached to several birds.

Researchers from Greenland, Denmark, the United States, Great Britain, and Iceland have successfully mapped the incredible migratory movements of the Arctic Tern. They attached small geolocation devices, weighing 1.4 g, to the legs of 11 Arctic Terns at breeding colonies in Greenland and Iceland and then retrieved them when the birds returned after their migration down to the southern hemisphere.


The migration routes of the Arctic Tern, southbound migration
(yellow line) and northbound (white line). The fuel stop in the North
Atlantic is the small circle, and the wintering sites at Antarctica are
the large circle. Areas particular rich in biological productivity are
indicated by yellow and green colours. Image: Greenland Institute of
Natural Resources

Lees meer: Birdwatch

Birds Favor Most Promising Offspring

Parasites can lessen a young bird’s chance of survival. If parents can detect signs of infection early, they may cut their losses by reducing their efforts to feed and care for parasitized broods—thus saving energy for healthy offspring or future breeding attempts.

A new study suggests that such parental vetting begins even before eggs hatch.

Lees meer: LiveScience