Movement strategies are one of the primary mechanisms underlying animal survival. Despite the impressive amount of studies on animal movement during successive stages in the life history in birds, little is known about the characteristics of movements during the post-fledging dependence period. Such a period represents a crucial phase of the life history during which individuals can show important displacements around the natal nest. Mere we present path search strategies employed by radio-tagged fledgling Eagle Owls Bubo bubo during the post-fledging dependence period (1962 locations from 41 tagged owlets). During the post-fledging dependence period, individuals show dynamic movement behaviours that might be related to the development of individuals' mobility and cognitive abilities. Immediately after leaving the nest, individuals focused their activities close to the nest, but after a few weeks individuals travelled further and faster, up to the moment that they started to disperse. At the time that the mobility of owlets was highest, their movements described straighter paths, Movement patterns were not affected by morphological- or physiological parameters of body condition. Between-sibling distances showed a significant interaction between sex and time: until 20 days after owlets left the nest, siblings were closer together, independently of the sex. Between-sibling distances increased with time as individuals became increasingly mobile; just before the start of dispersal, family units seemed to dissolve.

Several 19th and 20th century studies on Common Cuckoo Cuculus canorus brood parasitism suggest that Red-backed Shrikes Lanius collurio used to be one of its common hosts in central Europe. However, since the late 1960s parasitism ceased to occur in Red-backed Shrikes in Hungary. Using data from bird ringing records in the Czech Republic and Slovakia we evaluate whether this finding holds on a broader scale. We found a rapid decline in the parasitism rate, expressed as the frequency of Common Cuckoo chicks encountered in Red-backed Shrike nests, during 1964–2006. During the first decade of the study, on average 2.19% of Shrike nests contained a Cuckoo chick, while in the last decade Cuckoos occurred in 0.37% of the nests only. This suggests a six-fold decline over the study period. Parasitism rates showed strong regional variations which were positively related to the size of regional host populations. In addition to the high ability of Shrikes in discriminating Cuckoo eggs, as found in previous studies, we suggest that decreases in regional host population numbers might lead to host abandonment within a few decades. Whether these two factors work in tandem, or independently, remains to be answered.

Biometry of Iberian Dippers Cinclus cinclus has typically been addressed from a geographic perspective, often considering small local populations. In this work, we explored environmental correlates of among-population phenotypic variation in Dipper morphology throughout Iberia. We tested for effect of river slope, altitude, temperature and precipitation (summarized using Principal Component Analyses, PCA) on absolute and relative (controlling for tarsus length) wing length and tarsus length. We used data of 222 Dippers captured from 35 rivers in eight breeding areas in N and S Iberia. All biometric variables were larger for older birds and males, though tarsus length was not affected by age. Wing length was longer in S Iberia, even when controlling for tarsus length, All biometric variables co-varied negatively with one of the PCA components of abiotic factors, owing to large-scale environment differences between N and S Iberia (zone). The abiotic factors predicted mean tarsus length of birds within zones, with tarsus increasing with increasing river slope and decreasing temperatures and precipitation. Furthermore, Dippers from S Iberia were not larger but had longer absolute and relative wings than those from N Iberia. Altogether, these findings imply that the morphological diversification of Iberian Dippers is affected by the environment and that body size-wing length allometric relationship differs between N and S Iberia.

The tidal flats of the Bragantinian Peninsula in the tropical part of Brazil harbour wintering and migratory nearctic shorebirds in very high densities, whereas the benthic food supply is very low. In 2001 and 2002 a study was conducted on the habitat choice and distribution of shorebirds to investigate the formation of niches and the spatial distribution under the constraint of a limited food supply. We showed that shorebird densities were not correlated with a range of abiotic variables or with prey density within sites, but that between sites birds tended to select sites with peak prey densities. Two foraging guilds were differentiated: Whimbrel Numenius phaeopus, Willet Tringa semipalmata and Short-billed Dowitcher Limnodromus griseus preferred to forage in the water or on wet sand at the water's edge; while Red Knot Calidris canutus, Grey Plover Pluvialis squatarola, Ruddy Turnstone Arenaria interpres, Semipalmated Sandpiper Calidris pusilla and Semipalmated Plover Charadrius semipalmatus, were found predominantly on dry substrate. Although the birds showed species-specific preferences for characteristics defining microhabitats, niches were broadly overlapping. The results of our study suggest that, in case of a very low food supply, individuals might not be able to react to competition by niche segregation but might be forced to feed in a broad range of available niches.

The population of Baltic Dunlins Calidris alpina schinzii is very small and is declining rapidly. To optimize conservation efforts, knowledge about the location of staging and wintering sites is crucial. As part of intensive studies on Dunlins in Finland, Sweden, Denmark and Germany during the last 40 years, chicks and breeding adults have been marked, which has resulted in 110 recoveries during migration and winter. The majority of these recoveries are from western and northern Europe during the months immediately before and after the breeding season (21 February to 16 August), whereas there are only ten recoveries outside this period. Five of these ten recoveries, including four of six midwinter recoveries, are from N and NW Africa (Mauritania, Tunisia and Morocco). Given the relatively small probability of obtaining recoveries from these areas, the data indicate that the main wintering areas of the Baltic Dunlin are the estuaries in northern Africa, which it shares with other European and Nearctic populations of small-sized Dunlins breeding in Greenland, Svalbard, Iceland, Faeroe Islands, Ireland and Great Britain, The autumn migration period of the Baltic Dunlin is so short that the post-breeding moult must take place primarily at the wintering grounds. During spring and autumn, the Baltic Dunlin migrates well before the larger and much more numerous alpina subspecies, which breeds in arctic Eurasia. The recovery data suggest that the estuaries in the Baltic, the Wadden Sea, SE and S England, the Atlantic seaboard in France, and the Iberian Peninsula are of similar importance for the Baltic Dunlin as they are for the alpina Dunlins.

Different spatial distributions of food abundance and predators may urge birds to make a trade-off between food intake and danger. Such a trade-off might be solved in different ways in migrant birds that either follow a time-minimizing or energy-minimizing strategy; these strategies have been assigned to two sub-species of Bar-tailed Godwits Limosa lapponica that use the European Wadden Sea during northward migration. At the study area on Terschelling we recorded feeding site selection, time budgets and intake rates (prey/min) in the period that both lapponica (energy minimizer) and taymyrensis (time minimizer) sub-species were present (late April till the end of May 2007). Prey availability (number of prey/m²) was negatively correlated to the distance from cover. Based on resightings of colour-ringed Bar-tailed Godwits, taymyrensis was foraging closer to cover, and for a higher proportion of time than lapponica (67% vs. 33%). During the high tide period taymyrensis was also foraging on inland coastal meadows, Moreover, taymyrensis was more vigilant than lapponica, whereas lapponica showed more resting and preening behaviour. Lapponica had a higher instantaneous intake rate, but taymyrensis had a higher overall intake rate and the birds were more successful in taking larger prey items than lapponica. Supposedly, due to the increased foraging time and additional foraging on the inland meadows, the time-minimizing taymyrensis achieved a higher fuel deposition rate than lapponica. Taymyrensis shifted towards food-rich areas, apparently accepting higher predation risks, whereas energy-minimizing lapponica avoided predation danger by foraging further from cover.

We compared seasonal variations in body condition and fuel deposition patterns of five calidrid sandpipers at Chongming Dongtan (eastern China), a stopover site in the East Asian—Australasian Flyway. We tested the hypothesis that long-distance migrants show different body condition and fuel deposition patterns relative to those undertaking short-distance flights. Results indicated that the body condition and fuel deposition patterns of the sandpipers varied between the northward and southward migration seasons and between age-classes. Great Knots Calidris tenuirostris and Red Knots Calidris canutus migrate southwards on a long-distance nonstop flight from Chongming Dongtan to northwest Australia, while covering on the return flight a relatively short-distance between Chongming Dongtan and the north Yellow Sea region. Both species attained a significantly higher body condition at Chongming Dongtan during the southward than northward migration. Moreover, they showed a significant increase in body condition at Chongming Dongtan during northward migration stopover, which we see as a recovery from the long flight from Australia. In contrast, Red-necked Stints Calidris ruficollis and Long-toed Stints Calidris subminuta, employing series of relatively short-distance flights during migration, indicated no significant difference in departure body condition at Chongming Dongtan between seasons, nor significant increase in body condition during either migration stopover. Dunlins Calidris alpina on the other hand, showed a significantly higher body condition during northward than southward migration stopover, most likely in anticipation of the longer travelling distance after leaving Chongming Dongtan during northward migration. This study confirms that the body condition and fuel deposition patterns among shorebird species that undertake long-distance nonstop flights are different from those that undertake series of short-distance flights, suggesting that the comparison of body condition and fuel deposition patterns of calidrid sandpipers can be an important tool to understand their migration strategies.

Observations of departing Siberian-breeding Red Knots Calidris canutus canutus from their central staging site during northward migration, the Schleswig-Holstein Wadden Sea, Germany, in early June 2008, challenge the established notion that departing long-distance migrating waders only leave around sunset. During four days we scanned several thousand Red Knots for colour-ringed individuals and found a total of 20 different individuals that were previously ringed at either their main wintering site, the Banc d'Arguin in Mauritania, or at stopover sites on the Atlantic coast of France. Body masses of captured Red Knots in Schleswig-Holstein were higher than 200 g and hematocrite values showed an average of 58%, clearly indicating that they were ready for take-off. On all except one evening, we noted impressive departure movements during the incoming tide. On that exceptional evening a cold front thunderstorm passed over the area. Late the next morning, thousands of Red Knots departed during the incoming tide. We assume that the birds avoided taking off in adverse weather conditions and elaborate why Red Knots presumably traded off advantages from departing during twilight. We suggest that during spring migration, schedules are so tight that further delays decrease fitness, either because it would cause another full day of exposure to high predation risk by falcons, or because of conditions upon arrival on the tundra.

We studied abundance and feeding behaviour of wintering Sanderling Calidris alba at five beaches along the Belgian coast, and focused on the role of polychaete worms in their diet. On average 10.0 Sanderlings were present per km stretched beach, of which 87.8% were involved in foraging activities. Highest numbers of Sanderling occurred on the beach from 2 hours before to 4 hours after low tide. Detailed observations of individual birds revealed a mean pecking rate of 18.7 pecks per min. Birds exhibited several feeding modes, and we distinguished superficial pecking (mainly feeding on wreck) and probing for polychaetes. Feeding on wreck was observed frequently and throughout the tidal cycle. In contrast, probing for polychaetes was limited in time, and occurred primarily when the tide reached the upper intertidal zone, where peak densities of Scolelepis squamata were found. Based on our observations, we conservatively estimated that during each tidal cycle this benthic species may provide only 2.0–9.0% of a Sanderling's daily energy demand. Numbers of Sanderlings appeared to be lowest when capture rates on polychaetes were highest. We therefore suggest that polychaetes are of minor importance for Sanderlings foraging along Belgian beaches.

Cape Gannets Morus capensis are declining in numbers in all breeding colonies at the southern African west coast, potentially caused by deteriorating food availability. The behavioural responses of Individuals to changing conditions can provide insights into the mechanisms that drive population dynamics. We studied the relationship between parental provisioning behaviour and the breeding success of Cape Gannets breeding at Ichaboe Island (Namibia) in two years with different nesting success, to assess the potential role of variation in food availability in explaining variation in chick survival. in 2006/07 parents delayed the onset of breeding and visited nests at a lower frequency than in 2005/06, indicating that food availability was limited. Within the years Individual differences in provisioning rate but not in parental condition were associated with chick growth and survival. These associations remained present when controlling for seasonal changes. Predation, not starvation, was the main cause of mortality. Under poor conditions, as Indicated by long foraging trips, Cape Gannet parents left small chicks unattended, resulting in many being killed by Kelp Gulls Larus dominicanus. Long foraging trips were associated with reduced average breeding success, but impacted some parents more than others. Knowledge of the origin of this inter-individual variability is needed to predict how changes in food availability affect seabird population dynamics, which is one of the steps towards conservation of these birds.

We studied the impact of human disturbances on the feeding activities of Common Eiders Somateria mollissima wintering in Southwest Greenland. Eider activity and human disturbances (fast moving, open boats) were recorded during 9 days of observations in mid and late winter 2002. When most heavily disturbed, the feeding activity in the study area was reduced up to 60% on a daily basis. At the same time locomotion activity tripled. Logistic regression analyses showed that eiders attempted to compensate for lost feeding opportunities by rescheduling more feeding to periods where feeding conditions were relatively less profitable with respect to other variables. When undisturbed, eiders avoided feeding during high tide and intensified feeding at the start and at the end of the day, but these tendencies were levelled out if eiders were disturbed. When disturbed, the time interval and the distance to the last disturbance were both significant explanatory variables for the feeding activity. There was a cumulative effect of repeated disturbances on the feeding activity if disturbances were close in time and space (<1 h, <1 km). The day with the highest number of disturbances coincided with observations of nocturnal feeding the following night and may indicate that a critical threshold of disturbances was reached where eiders could not rely on a diurnal feeding strategy.

We studied the rate of predation on artificial and natural nests of Great Reed Warbler Acrocephalus arundinaceus in two contrasting vegetation types, reed Phragmites australis and reed mace Typha angustifolia beds. Reed provided thinner and taller stems to attach a nest to than reed mace, and reed mace provided more cover in late spring, but not in early spring. Nest density, the distance of nests from the water edge, and the timing of breeding differed considerably between vegetation types. However, there were no differences in survival rates of natural nests between both habitats. Artificial nests, on the contrary, were more frequently depredated in reed beds. Based on peck marks left on plasticine eggs, 74% of identified nest predators were large birds in both reed and reed mace beds. There was no correlation between the predicted predation rate of natural nests (derived from a logistic regression model using artificial nests) and the observed predation rate of natural nests, suggesting parental nest defence behaviour or subtle differences between actual nest sites and artificial nest sites might account for the observed discrepancy between natural and artificial predation rates. We suggest that interactions between vegetation structure, nest site choice and parental behaviour may have influenced nest predation rates in the Great Reed Warbler.

Nest site selection of the ground-nesting Montagu's Harrier was studied in a natural habitat in eastern Poland, the Chełm Calcareous Marshes (850 ha). All nests in the study area were placed in the sedge community Cladietum marisci. The water at nest sites was deeper, and the vegetation was higher, denser and broader-leaved than found at random points. Distance to the nearest meadows did not differ between nest sites and random points; all nests were placed over water, though. These data suggest a preference for nesting in wet places with older and higher vegetations growing in high density.

As part of a study on the core body temperature (T_b) of desert birds, we purposed to use temperature-sensitive implantable radio transmitters. Because of the difficulty in recapturing these birds, we needed to know if these electronic devices held their calibration over the duration of normal battery life (21 days). Our initial calibration at 40°C was consistently less than that of the manufacturer, although in some cases differences were small: deviations in temperature as predicted by the company's calibration and our own ranged from 0.1 to 1.7°C, We tested for drift in calibration and found that for the first 9 days of operation, most radio transmitters deviated by less than 0.5°C from the initial calibration. Differences between predicted and actual temperature became progressively larger with time, sometimes exceeding 2.0°C. If possible, we suggest that transmitters be calibrated, implanted, and then after taking data on T_b of the free-living bird, the transmitters should be recovered and recalibrated. If it is not possible to recapture birds, then our data suggest that Tb predicted by pulse periods are reasonable up to 9–12 days after the initial calibration but data recorded beyond this time period are potentially suspect.

Carotenoids are interesting in avian ecology due their dietary origin and the resulting environmental dependence of certain functions and traits such as plumage pigmentation and the immune system. Carotenoids are frequently assumed to be limited for birds, but data on availability is rarely collected. Thus, to understand the role of the carotenoids as mediators of trade-offs, additional information on the whole chemical pathway of carotenoids is needed. In conjunction with previous studies on carotenoid ecology and physiology of the Great Tit Parus major living in Swedish urban vs. rural environments, I here present data on 1) carotenoid concentration in two primary carotenoid producers, birch Betula verrucosa and oak Quercus robur and 2) vegetation cover on Great Tit territories. Previous studies found lower carotenoid concentrations in caterpillars and plumage pigmentation in urban compared to rural areas. Correspondingly, urban trees had significantly lower total carotenoid concentration in comparison to rural trees, but there was no environmental difference in the relative amount of lutein and zeaxanthin (Lut:Zx ratio) in sun-exposed leaves. Second, urban Great Tits had significantly more shade in their territories than rural birds, which may affect the leaves Lut:Zx composition. The results, taken together, show that the environmental difference in carotenoid concentration of caterpillars and Great Tit yellow breast coloration, may occur because urban trees synthesise less or have used up more carotenoids in response to environmental stress compared to rural trees. Thus, tracking carotenoid content in different steps of the food chain raises questions about how fine-scale environmental heterogeneity can affect optimal foraging behaviour and individual variation in carotenoid-dependent traits.