We tracked three juvenile and 14 adult Marsh Harriers Circus aeruginosus from southern Sweden via satellite to investigate migration strategies. Four individuals were tracked for at least two years. All three juveniles and four of the adults made west-oriented pre-migratory movements well before the onset of autumn migration, and trans-Saharan migrants visited post-migratory stopover areas in tropical Africa. By these movements, the harriers presumably exploit short-term regional variation in food abundance. Autumn and spring migration occurred in a relatively narrow corridor, without distinct differences between sexes in timing, speed, distance, and duration of migration, except that females tended to migrate faster in spring than did males. Juveniles migrated shorter distances than adults, and migration speeds were lower. Spring migration was similar to autumn migration in terms of speed and duration. Juveniles did not cross the Sahara Desert and three birds, one female and two juveniles, wintered in Europe, which is in accordance with a recent increase in the number of (juvenile) Marsh Harriers wintering in northwestern Europe. All birds that crossed the Sahara wintered in tropical West Africa. Harriers showed site fidelity to breeding, wintering and stopover areas. The overall migration speed of Marsh Harriers was similar to that of Ospreys Pandion haliaetus and Honey Buzzards Pernis apivorus, two other trans-Saharan migrants. Ospreys use fly-and-forage migration to promote resulting speed, whereas Honey Buzzards are particularly apt to exploit thermal soaring. How Marsh Harriers balance foraging versus travelling to accomplish their rapid migration speeds remains to be resolved.

We studied annual and geographical variation in the proportion of breeding non-adult (<4.5 years old) Spanish Imperial Eagles Aquila adalberti in relation to the species' recent demographic recovery. The proportion of non-adult breeders in the populations studied increased significantly during 1983–2004 in parallel with the population increase. Non-adult pairs were more often associated with ‘young’ territories (occupied recently) than with territories that had already been occupied for longer time (mostly used by adult pairs). Adult pairs produced significantly more chicks than mixed adult— non-adult pairs, which in turn had a higher productivity than pairs in which both male and female were non-adult. Adult pairs attempted breeding more often than non-adult pairs, and clutch and brood size were larger. The poorest reproductive output was found in pairs with non-adult males. These differences were not associated with differences in fledging rates. Once the influence of territories was controlled for (comparing the productivity between adult pairs and non-adult pairs present in the same territory) the age effect on productivity was significant. Our results emphasise the important role which the recruitment of non-adult birds into the breeding population may have played in the recent population recovery of the Spanish Imperial Eagle.

The timing of breeding and the chicks' fledging condition are major fitness-relevant traits in the Great Tit Parus major. Yet, the proximate mechanisms relating these traits to differential survival and recruitment are largely unknown. We analysed the range use of Great Tit family groups during the first 20 days after fledging, i.e. the period of post-fledging dependence, in relation to the juveniles' body condition. Radio-telemetry and colour marks were used to track 25 families with 107 chicks. The post-fledging home-ranges of families with fledglings of good condition (average body mass 19 g) were c. 3 times larger than of those with poorly nourished (average 15 g) young. The rate of movements exceeding 50 m per hour was also positively correlated to the chicks' mean fledging mass. We hypothesise that the fledglings' body condition resulted in large differences in flight performance, and consequently, spatial behaviour of the family groups. The slow movements and the close grouping of chicks of poor body condition likely increase their vulnerability to predation. In the late season, fledglings of poor condition had significantly lower food intake rates compared to those of good condition. We suggest that the relevance to survival and thus, fitness of the fledglings' physical condition, is via the behavioural and metabolic competence, which in turn may affect flight performance, range use, energy intake rate, and ability to escape predation.

The ability of animals to survive habitat loss is likely to be dependent not only on the proximity of alternative habitat but also on the ability of individuals to relocate. Here, we examine influences on the settlement behaviour of Redshank Tringa totanus following winter intertidal habitat loss resulting from the construction of a barrage at Cardiff Bay, on the Severn Estuary, UK. Results supported previous studies showing that the species is highly faithful to its wintering sites. Redshank were reluctant to leave Cardiff Bay in the first winter following habitat loss: birds used the site at all tidal stages for eight days after barrage-closure and thereafter continued to roost there. Birds moved at most 19 km, the distances that individuals moved being inversely related to their age, indicating that young birds were less attached to the bay and so more plastic in their response to change. Settlement also appeared to be influenced by prior knowledge — notably, one site previously only used nocturnally by ‘Cardiff Bay’ birds was used diurnally post-closure despite being heavily disturbed during the day. Birds initially ranged more widely following their displacement, but over the three winters post-closure, became increasingly concentrated into one recipient site, just 4 km from the bay. It is suggested that individuals' fidelity to Cardiff Bay post-closure and lack of knowledge of alternative foraging sites would have been to their detriment.

The Black-tailed Godwit Limosa limosa is a characteristic breeding wader of wet grasslands in The Netherlands which has suffered a strong population decline since the 1960s. Low breeding success has been implicated as the main driver of this decline and here we examine whether changes in adult survival could also have played a role. Adult godwits were colour-ringed and resighted from 2002 through 2005 at four study sites in The Netherlands. Apparent adult survival was estimated in program MARK using Burnham's model for both live resightings and dead recoveries. In addition, nest site fidelity was estimated at two of the sites by recording the distance between nest locations in successive years. Apparent adult survival was 0.93 (SE 0.03) in one study area and 0.81 (SE 0.04) in the other three sites. Overall apparent adult survival was 0.83 (SE 0.03). These values are similar to estimates from the 1970s and 1980s. Nest site fidelity was higher in the site with highest survival (median distance between nests in successive years: 49 m vs. 252 m in the other site), suggesting that the difference in apparent survival may result from differences in emigration rates. Thus, our results suggest that current adult survival is not different from rates 30 years ago, and therefore do not point to reduced adult survival as the driver behind the current population decline of Black-tailed Godwits.

To get a better understanding of the current population decline of Black-tailed Godwits in The Netherlands, we determined reproductive parameters in two Dutch breeding populations over the period 2002–2005 and investigated the relationship between reproductive output and timing of breeding. Annual median laying dates ranged from 14 to 25 April, and median hatching dates from 11 to 28 May. Sites differed in laying dates but not in hatching dates. Daily survival rate of nests was positively correlated to nest age and was affected by year and by the interaction of year and site, but not by laying date. The number of eggs hatching per successful nest also did not depend on laying date. Maximum chick survival (maximum estimate of the number of chicks fledged divided by the number of chicks hatched from the nest) and the probability of raising at least one chick to fledging declined significantly with hatching date, resulting in a decline of reproductive output with laying date. Minimum chick survival correlated negatively with cumulative minimum temperature during the first week after hatching. Duration of rainfall during the chick-raising period did not affect chick survival. Our estimates of reproductive output were lower than found in previous studies, and in most years reproductive output was too low to compensate for adult and juvenile mortality. Five possible proximate causes for the seasonal decline in chick survival are discussed: parental quality, weather conditions, food availability, predation pressure and mowing of the grassland habitat.

Sexual selection may play an important role in the evolution of carotenoid-based signals. According to the parasite-mediated sexual selection hypothesis, organism health, parasite resistance and the expression of ornaments are linked. While some studies have analysed the expression of male carotenoid-based ornaments in relation to parasites and immune system capacities, few studies have focused on carotenoid-derived colour patches expressed in both sexes. We analysed the relationships between endoparasite (blood and systemic parasites) loads, haematological values and the components of red mask colour in wild European Goldfinches Carduelis carduelis, a species with a carotenoid-based facial mask in both sexes. Both, males and females were assessed for immune quality and face mask expression. Face mask coloration was sexually dichromatic, males have less orange masks than females. The yellow component of the mask showed less intensity in females infected with Haemoproteus blood parasites. The total leukocyte count was inversely correlated to the yellow component of the mask in females, suggesting that mask colour reflects the immune status of females during the breeding season. Isospora infection appeared to limit the UV reflection of the red mask of females.

Gull-billed Terns Gelochelidon nilotica wintering in Guinea Bissau mainly fed on fiddler crabs Uca tangeri and were occasionally seen feeding on fish and locusts. As fiddler crabs have a low energy content, terns need a large gross intake to meet daily energy demands. Fiddler crabs also have a low ratio of digestible flesh to exoskeleton, and therefore tern food intake may be limited by gut capacity. Activity budgets of Gullbilled Terns feeding on fiddler crabs showed that a considerable part of the time was spent resting. The duration of resting intervals increased with energy intake and was positively correlated with the metabolisable energy content of the crab eaten, suggesting that resting periods were required for a proper digestion. The poor quality of fiddler crabs was offset by high capture rates. So daily energy expenditure of the terns could easily be met by feeding on fiddler crabs. Even when resting pauses were included in foraging time, foraging for only 1.5 hours on fiddler crabs satisfied the terns' daily energy demands. Instead, feeding on energy-rich fish would require about 2.5 hours to satisfy daily energy demands. Compared to the more specialised piscivorous Little Tern Sternula albifrons and Sandwich Tern Sterna sandvicensis, capture rate of fish was poor in Gull-billed Terns. From an energetic point of view, wintering Gull-billed Terns feeding on fiddler crabs seem to have an easy living in Guinea Bissau.

The timing, duration and pattern of the poorly documented wing moult in the Eurasian Stone-curlew Burhinus oedicnemus were described and related to the breeding cycle. Between 1998 and 2007, 141 birds were trapped in the Taro River Regional Park (Parma, Italy) both while incubating and during the post-breeding season. The timing of primary moult was estimated according to the method of Underhill & Zucchini (1988) and Underhill et al. (1990). Primary moult was very slow and overlapped most of the breeding season, beginning in early May and ending in October. Secondary moult was much more irregular and was not completed within a single moult cycle. Innermost and outermost secondaries were more likely to be shed than those at the centre of this tract. Juvenile secondaries were not shed during the first winter. The study provides the first detailed analysis of wing moult in the Eurasian Stone-curlew and suggests some useful ageing criteria based on the pattern of secondary moult. The extensive overlap between breeding and moulting is relatively uncommon compared to other waders. This could be interpreted as a way to maximize breeding success through renesting potential (up to 4 attempts), i.e. by spreading the cost of moult over a prolonged time period. A between-species comparison using independent contrasts was consistent with this hypothesis: species with a prolonged breeding season also showed considerable overlap in the timing of primary moult and breeding activities.

We investigated breeding patch fidelity and between-year territory movements in relation to breeding success and habitat characteristics in a colour-ringed urban population of the Common Redstart Phoenicurus phoenicurus. In 1996–2004, 111 marked adults (59 males and 52 females) produced 60 recapture events (41 in males and 19 in females) from 39 individuals (29 males and 10 females). Redstarts showed moderate between-year breeding patch fidelity of 46.3% males and 31.1% females returning. However, 56.1% of males and 47.4% of females shifted territory within the study area between consecutive seasons. Most of the Redstart males moved to an adjoining territory, whereas females on average moved further (197 vs. 331 m). We suggest that local experience is important for territory choice in males, whereas females use other cues, such as quality of nest cavities and mates, for dispersal decisions. We found no effect of breeding success (nest failure and number of fledglings) in the previous season on the probability of between-year territory shifts. However, Redstarts showed a tendency to switch territories towards areas with a higher proportion of tree cover and the latter could probably provide some advantage, e.g. supply of food and nest cavities, lower competition and predation rates.

The growth of Whiskered Tern Chlidonias hybrida chicks was investigated in Lake Grand-Lieu, western France. Body mass, tarsus, culmen and wing lengths of 33 chicks from 19 nests held in enclosures were measured at intervals of 2–3 days during the rearing period (0–20 days). The repeatability between two observers in chick body size measurements was generally high (overall 0.94), with the highest value for the wing length. Tarsus length and body mass increased fast and reached asymptotic values at about 14 (23.23 mm ± 0.18 SE) and 16 days (92.35 g ± 1.82 SE). The body mass growth rate (K, resulting from a logistic model) was 0.294 g day^-1 ± 0.016. The linear growth rate at age 3–9 days was 6.32 g day^-1 ± 0.28 SE. The standardized linear growth rate was 7.0% of adult body mass, which was in the range of values recorded for the closely related Black Tern Chlidonias niger (6.5–7.9%). The culmen and wing were still growing at fledging (age 20 days), asymptotic values had clearly not been reached. Before fledging, chicks were better aged by wing length (logistic model) than by any of the other body measurements. Given the geographic variation in bird morphometry, the applicability of our growth curves to disjoint populations of whiskered terns may be restricted. We encourage therefore new studies on chick growth in other European breeding populations.

Nest building requires parental investment and we should expect to find trade-offs between building and other behaviours or demands. For example, species breeding in temperate zones face the seasonal shift from spring to summer and might alter their nest construction in relation to environmental conditions as the season progresses. We quantified seasonal variation in the length of the nest building period, nest mass, composition, Hen Flea Ceratophyllus gallinae abundance and egg production in nestbox breeding Blue Tits Cyanistes caeruleus. The nest building period decreased seasonally, possibly indicating individual adjustment of optimal time of reproduction. Despite this, there was no seasonal trend in overall nest mass, although nest composition did change. The mass of the nests' moss base and Hen Flea abundance showed no seasonal variation, but there was a seasonal decline in the mass of the cup lining material, suggesting that female Blue Tits selectively adjust the cup lining component of their nests to reflect increasing ambient temperatures in order to create an optimal microclimate for the developing embryos and nestlings.

We report an observation of a wild New Caledonian Crow Corvus moneduloides manufacturing two tools from dry grass stems, and using them to extract lizards from the crevices of a fencepost. We recovered one of the tools and were able to examine the raw material from which tools had been manufactured. This confirms our earlier observations with animal-borne video cameras, where we inferred use of this hitherto undocumented tool material from frame-by-frame analysis of video footage.

We describe the use of subcutaneous passive integrated transponder (PIT) tags in nestling and adult Great Tits Parus major. We investigated whether subcutaneous PIT tags affected fledging success, winter condition, survival and/or recruitment. We found no negative effects of PIT tags on any of these measures either in juveniles or in adults. Subcutaneous PIT tags have the advantage that the risk of tag loss is negligible and that further data collection can be automated. The subcutaneous implantation of PIT tags provides a promising technique for researchers aiming at gathering short or long-term data without the need to handle or disturb small birds after implantation.