Early bird gets the better song

Mothers transfer the gift of music to the first eggs of their brood.

Birds that come from the earlier eggs in a brood are more likely to be better singers, scientists have found.

In most bird species, song is used by males to demonstrate their fitness to potential mates, and many studies have shown that the healthiest males tend to sing the longest, loudest and most complex songs.

Masayo Soma — who researches biolinguistics at the Riken Brain Science Institute, in Wako, Japan — and her colleagues wanted to find out if the order in which birds hatch affects their song. "I expected to detect age hierarchy in song, because older siblings are stressed less and obtain more resources growing up," says Soma.

Lees meer: Nature News

Insect shortage leaves sparrows starving

One of Britain's best-known birds may be declining because its chicks have too little to eat.

Too few insects in summer means young house sparrows in towns and cities are starving in their nests especially when parent birds are trying to raise important second and third broods.

Increased development, the popularity of ornamental plants like Leylandii, the removal of trees and the conversion of front gardens for parking may explain the loss of insects in urban areas, new research suggests.

Lees meer: The RSPB

Spring migration dynamics and sex-specific patterns in stopover strategy in the Wood Sandpiper Tringa glareola

Auteurs: Yoko Muraoka, Christian H. Schulze, Mihaela Pavličev, Gábor Wichmann
Bron: JOURNAL OF ORNITHOLOGY, DOI 10.1007/s10336-008-0351-5
Abstract: Due to being a virtually monomorphic wader species, migration dynamics and sex-related migration patterns in the Wood Sandpiper (Tringa glareola) have rarely been investigated. We captured spring migrants at an important stopover site in northeastern Austria. Birds were individually color-marked, and sex was determined by an analysis of DNA from tail feather material.
 Among temporary residents (birds seen again after day of capture), males migrated on average 3 days earlier than females. However, since sexes did not differ in fat score, the length of stay and the proportion of transients (birds not seen again after day of capture) and temporary residents, we suggest that males and females adopt similar migration strategies in the spring.
The large number of transients captured as well as shorter stopover durations in later temporary residents indicate that Wood Sandpipers minimize time at this stage of their northbound migration. Temporary residents earlier in the season exhibited lower fat stores than later ones. Nevertheless, since the fat stores of transients and temporary residents were similar even after the progress of the season had been accounted for, we assume that Wood Sandpipers may afford to exhibit individual flexibility in migration strategy and the use of stopover sites, especially early in the season. This variability may be a necessary adaptation to cope with possible varying environmental conditions at dynamic and unpredictable inland stopover sites.
After having reached North Mediterranean regions, mean body mass of spring migrants gradually increases during successive stopovers, indicating that Wood Sandpipers follow a 'hopping' migration strategy. This emphasizes the high conservation value of even small artificial mudflat pools as important stepping stones in order to maintain a continuous network of wetland habitats for this continental migrant.

Social learning of hunting skills in juvenile marsh harriers Circus aeruginosus

Auteurs: Ignacy Kitowski, Maria Curie-Sklodowska
Bron: JOURNAL OF ETHOLOGY, DOI 10.1007/s10164-008-0123-y
Abstract: The impact of social factors on the improvement of hunting skills of juvenile marsh harriers during their first autumnal migration were studied in SE Poland. While foraging with adult birds, juveniles performed more dives on prey both in terms of number of trials and rates. Hunting sessions of juveniles were more efficient in the presence of adults than in the absence of adults.
Juveniles hunting with adults and other juveniles could select adequate habitat patches in which access to prey is easier.
The role of vertical and horizontal transmission of information in the development of hunting skills in juvenile marsh harrier were confirmed because faster development of hunting ability was achieved in the social hunting after the end of their postfledging dependency period.

Longer guts and higher food quality increase energy intake in migratory swans

Auteurs: van Gils, JA; Beekman, JH; Coehoorn, P; Corporaal, E; Dekkers, T; Klaassen, M; van Kraaij, R; de Leeuw, R; de Vries, PP
Bron: JOURNAL OF ANIMAL ECOLOGY 77 (6): 1234-1241 NOV 2008
Abstract:
1. Within the broad field of optimal foraging, it is increasingly acknowledged that animals often face digestive constraints rather than constraints on rates of food collection. This therefore calls for a formalization of how animals could optimize food absorption rates.

2. Here we generate predictions from a simple graphical optimal digestion model for foragers that aim to maximize their (true) metabolizable food intake over total time (i.e. including nonforaging bouts) under a digestive constraint.

3. The model predicts that such foragers should maintain a constant food retention time, even if gut length or food quality changes. For phenotypically flexible foragers, which are able to change the size of their digestive machinery, this means that an increase in gut length should go hand in hand with an increase in gross intake rate. It also means that better quality food should be digested more efficiently.

4. These latter two predictions are tested in a large avian long-distance migrant, the Bewick's swan (Cygnus columbianus bewickii), feeding on grasslands in its Dutch wintering quarters.

5. Throughout winter, free-ranging Bewick's swans, growing a longer gut and experiencing improved food quality, increased their gross intake rate (i.e. bite rate) and showed a higher digestive efficiency. These responses were in accordance with the model and suggest maintenance of a constant food retention time.

6. These changes doubled the birds' absorption rate. Had only food quality changed (and not gut length), then absorption rate would have increased by only 67%; absorption rate would have increased by only 17% had only gut length changed (and not food quality).

7. The prediction that gross intake rate should go up with gut length parallels the mechanism included in some proximate models of foraging that feeding motivation scales inversely to gut fullness. We plea for a tighter integration between ultimate and proximate foraging models.

Aerial flocking patterns of wintering starlings, Sturnus vulgaris, under different predation risk

Auteurs: Claudio Carerer, Simona Montanino, Flavia Moreschini, Francesca Zoratto, Flavia Chiarotti, Daniela Santucci, Enrico Alleva
Bron: ANIMAL BEHAVIOUR, doi:10.1016/j.anbehav.2008.08.034
Abstract: To test the hypothesis that variation in aerial flocking behaviour is adaptively related to predation risk, we described and quantified the flocking patterns of starlings, approaching two urban roosts, which differed in predation pressure (by peregrine falcons, Falco peregrinus).
We predicted that the higher predation pressure in one of the roosts would be reflected in larger and more compact flocks, thought to be less vulnerable to predation than small flocks. Incoming flocks, not under direct attack, were observed during winter for 53 days.
We identified 12 flocking shapes. Significantly higher frequencies of compact and large flocks were observed in the roost with high predation pressure, while small flocks and singletons were more frequent at the roost with low predation pressure. Similar patterns were observed in both roosts when other flocks displayed antipredator behaviour, even when far away and in the absence of the predator at the focal roost.
This may indicate that social information passed between flocks affects flocking decisions. Predation success was higher at the roost with low predation. These results suggest that aerial flocking patterns are affected by predation risk and possibly by the behaviour of other flocks in response to direct attacks.

Distribution pattern of an expanding Osprey ( Pandion haliaetus) population in a changing environment

Auteurs: Mei-Ling Bai, Daniel Schmidt, Eckhard Gottschalk, Michael Mühlenberg
Bron: JOURNAL OF ORNITHOLOGY, DOI 10.1007/s10336-008-0345-3
Abstract: We studied the nest site selection and distribution pattern at landscape level of the German Osprey population, and demonstrated how to test the predictions of the ideal free distribution theory and its derivatives on such an expanding population. Information about the location and breeding success of each Osprey nest site between 1995 and 2005 was collected through a long-term monitoring programme. Data of land cover types were acquired from the administrations of each federal state and the CORINE Land Cover database.
The results showed that Ospreys preferred landscapes with more water bodies and forests. Such sites were also occupied earlier and had higher local population density. However, in the study period of 11 years, there was a gradual shift from forest-dominated landscapes to agricultural land-dominated landscapes.
The breeding success increased over time, with no difference in the breeding success between pairs nesting on trees and poles, whereas there was higher breeding success at nest sites surrounded by more agricultural land and less forest. The more efficient foraging in eutrophic lakes in agricultural landscapes was the most likely cause for the higher breeding success.
The distribution pattern of the Ospreys did not match the resource allocation, which deviated from the models tested. We suggested that the proximate cues used for nest site selection mismatched site quality due to anthropogenic environmental changes.

An artificial nest experiment indicates equal nesting success of waders in coastal meadows and mires

Authors: Pehlak, H; Lohmus, A
Source: ORNIS FENNICA 85 (2): 66-71 2008
Abstract:
Degradation of the distinct, diverse and abundant wader communities in Estonian coastal meadows has been recorded along with the ceasing agricultural management there. At the same time, the same species have been occupying adjacent inland mires.
This study examined the possibility that waders are switching their habitat due to increased nest predation in coastal meadows. However, no differences in the average daily survival rates of artificial nests were found between meadows and mires.
Data on real wader nests indicated that artificial nests reflect the fate of real nests. We suggest that meadows may have lost a past safety advantage and now the breeders are re-settling according to the current habitat quality. However, given the general
decline of waders, the temporally increasing populations of mire breeders are hardly self-sustaining. Therefore, attempts to restore coastal meadows are crucial for the Baltic Populations of several wader species.