In recent years, Skylarks Alauda arvensis have undergone dramatic population declines in many European countries. Evidence exists for deteriorating conditions during the breeding season, but little is known about the situation during the rest of the annual cycle. Here we use two approaches to test if the Dutch breeding population of Skylarks consists of resident and/or migratory individuals. First, we present an analysis of ring recoveries from the Dutch Ringing Centre “Vogeltrekstation”. Out of 25 recoveries, 12 Skylarks were resident in winter, 10 migrated and three were classified as probable migrants. Resident birds were accompanied during winter by birds from northern and eastern Europe. Very limited natal and breeding dispersal recorded in the same dataset suggests that our results were not influenced by long dispersal distances. Next, we compared these results to a local radio-telemetry study in the northern Netherlands. During two different years we equipped a total of 27 Skylarks from a breeding population with radio-transmitters and followed them during the subsequent winter. Four birds were found to winter locally. Out of 23 individuals that we did not find in winter, 14 returned in the following breeding season to the study area, all with a working transmitter, suggesting that they wintered outside our study area. Two ring recoveries of birds from the same study population indeed showed migration to south-west Europe. Based on these two lines of evidence, we conclude local coexistence of a resident and a migrant strategy in Dutch Skylarks. The findings of our study are important for the planning of conservation efforts, as we can only protect this rapidly declining species when we know their behaviour and whereabouts throughout the entire annual cycle.

During the spring migration arctic-breeding geese pause in temperate and subarctic staging areas in order to deposit body reserves for breeding. Focusing on a single arctic stopover site in West-Spitsbergen, Svalbard, Norway (Vårsolbukta, 77°45′N, 14°24′E), behavioural strategies of Barnacle Geese Branta leucopsis were investigated and body condition and presence of individually marked birds recorded. Individuals using different staging areas earlier along the migration route (Helgeland and Vesterålen on the Norwegian mainland) and heading to different breeding colonies (the close-by Nordenskiöldkysten, and the distant Kongsfjorden) were compared during springs 2003–05. Birds in Vesterålen left the staging area earlier than those in Helgeland, and arrived earlier in Vårsolbukta as well. In Vårsolbukta, females gained body condition at a similar rate regardless of their colony affiliation, whereas males from Nordenskiöldkysten exhibited a smaller overall increase in condition compared to males from Kongsfjorden. The Kongsfjorden birds stayed for a shorter period (average 2.8 days) than those from Nordenskiöldkysten (average 4.0 days). Nordenskiöldkysten birds frequently left Vårsolbukta for short periods presumably visiting the breeding area in order to optimise nest initiation with respect to prevailing snow conditions. The date of final departure was also correlated with nest initiation date at Nordenskiöldkysten. No such relationship for the Kongsfjorden birds was found. We suggest that the geese adopt a ‘hopping’ strategy, using a network of stopover sites in Svalbard during spring with a last stopover at a buffer area in the proximity to the breeding area. For this vulnerable population it is important to identify the sites forming the links in this chain, and to establish their function and utilisation by geese during the vital prebreeding period.

Afro-Siberian Red Knots Calidris canutus canutus use the western Dutch Wadden Sea as a refuelling area during southward migration from Taimyr to West Africa. Here we document the decline of their food stocks in this area, based on a yearly large-scale benthic mapping effort, from 1996 to 2005. For each benthic sampling position, intake rate (mg/s, ash-free dry mass) was predicted by an optimal diet model based on digestive rate maximization. Over the ten years, when accounting for a threshold value to meet energetic fuelling demands, subspecies canutus lost 86% of its suitable foraging area. Over this period, the proportion of probable canutus in mist-net catches in July—August declined relative to overwintering islandica Knots. This suggests that canutus dropped even more in numbers than islandica, for which we showed earlier a food-explained decline in numbers. We discuss the possible causality between a decline in the quality of intertidal mudflats in the Dutch Wadden Sea and population declines of Knots in the West-African wintering quarters.

Iberia receives many dispersing, migrating and wintering Common Kingfishers Alcedo atthis. The majority of these individuals occur in coastal marshes. Between August and mid-October 2007 and 2008, Kingfishers were mist-netted at a tidal marsh in Txingudi, northern Iberia. They were especially abundant from August to September, indicating that Txingudi receives an influx of migrants from northern Europe or local birds dispersing from nearby natal areas. The population mainly consisted of juveniles (only 5.8% adults), the sex ratio was 1:1 and the timing of passage was similar between the sexes. Body mass controlled for body size was constant with time. The stopover duration was affected by sex, date (month of first capture) and a body mass/size ratio, here used as a proxy of fuel load. Females with a lower body mass/size ratio were more likely to remain for longer than those with higher ratios, but the opposite was found in males. Kingfishers captured in August were more likely to be already settled in the area than those first captured in September. Moreover, birds with short stopovers systematically lost mass, while birds that remained in the area for longer did not. These findings are discussed in the light of possible competition between newly arriving and already settled birds.

In evolutionary ecology, environmental monitoring and conservation management, reliable information on phenotypic and demographic traits in marine seabirds is highly wanted, but difficult to acquire. Therefore, freshly dead Common Guillemots Uria aalge (n = 149) incidentally drowned in salmon drift gill nets in the Baltic Sea, during October—November, were studied. We noted age, sex, moult pattern and fat status, and took morphometric measurements to compare with data from the Northeast Atlantic population. Only minor phenotypic differences were found. The birds had slightly longer wings than expected at the latitude where they were collected, probably due to their newly grown primaries and/or observer differences, rather than a genetic divergence. The Baltic Guillemot appears not to be a distinct subspecies, but only the marginal member of a deme. Ringing recoveries also suggest intermittent exchange of birds between the Baltic and the North Sea. Young birds did not seem to be over-represented in gill net bycatches. Our found age distribution — with a heavy dominance of adult birds, but few immature/juveniles — deviated from that reported earlier, and suggests that the population is more vulnerable to adult mortality through bycatch in gill nets than previously believed.

Adult birds usually display brighter plumage coloration than younger individuals. This difference may be either due to selection against less coloured yearlings or to an increase in coloration after their first complete moult. In this study, we examined age-related differences in carotenoid-based yellow ventral coloration of Great Tits Parus major. Cross-sectional analyses at the population level showed that older males are in general greener and more saturated in colour than yearling individuals. Longitudinal analyses using birds captured in subsequent seasons confirmed within-individual changes in coloration with age. Such increase in coloration might be the result of the development of better foraging skills with age- and hence, the individual ability to obtain enough carotenoid-rich sources at the time of moult-, or consequence of other factors indirectly associated with age. However, we cannot rule out the possibility that other factors (such as directional selection against less coloured individuals) operate additionally at the population level.

This study analyses habitat selection by male Little Bustards Tetrax tetrax of a central Spanish population within their display sites during two consecutive breeding seasons. The areas of sexual display sites were determined by applying minimum convex polygons (MCP) to locations of individual males throughout the 2001 and 2002 breeding seasons. Habitat selection was addressed by means of a compositional analysis. The effects of variables related to phenology and to the density of conspecifics were examined, assuming an ideal free distribution of organisms. The spatial distribution of display areas was also analysed. During both years male Little Bustards showed a significant preference for old and same-year fallows, these offering both shelter and food. Contrary to what was expected, individuals did not select lower quality habitats when conspecific density increased or when areas were occupied earlier, suggesting that the population was not saturated. Display sites were not clumped, showing that in this population the Little Bustard may not employ a lek mating system, even though certain requirements of an exploded lek system — the inclusion in territories of particular habitat types that females could potentially use — were met. Our results emphasise the importance of agrarian substrates in determining occupation by this species, a finding with direct implications for the conservation of populations given that the agrarian landscape is on a sufficiently large scale for management measures to be introduced.

Long-distance migratory bird species might face larger problems to adapt to local climate change in their breeding area than short-distance migrants. This study investigated the effect of climatic change on the timing of the breeding season of two wader species with contrasting migration strategies, the long-distance migratory Black-tailed Godwit Limosa limosa and the short-distance migrant Northern Lapwing Vanellus vanellus. We tested the hypothesis that a change in breeding schedule will be stronger in the Lapwing than in the Godwit. Our analyses are based on the ringing dates of around 35,000 Black-tailed Godwit chicks and 112,000 Lapwing chicks from 1960 to 2004 in The Netherlands. The results demonstrate that the Lapwing is breeding earlier than in the 1960s, independent of the species' direct response to warm early springs. In contrast, the Godwit does not exhibit earlier breeding dates other than a direct response to warmer springs. Our observations suggest that the Godwit is not able to advance breeding dates to cope with changes in its breeding habitat. This could mean the species is suffering lower breeding success than would have been the case if it had adapted, and this could be one of the reasons for the stronger decline in The Netherlands of the Godwit population than that of the Lapwing.

Meadow bird species in the Netherlands have shown a long-term decline in numbers. This has been generally attributed to agricultural intensification, but in addition an increase of disturbing elements may have played a role in the decline. In this review we compiled data from literature to explore to what extent breeding by meadow birds (Eurasian Oystercatcher Haematopus ostralegus, Northern Lapwing Vanellus vanellus, Black-tailed Godwit Limosa limosa) is limited by disturbing landscape elements. We considered elements that can be considered ‘view-obstructing’ (like trees or houses), and those that can be considered ‘flat’ (canal, road or railway). Our review shows that breeding birds keep a distance to both types of landscape elements, with distances ranging over 1 km for highways and village edges. Roads with high traffic intensity caused the largest disturbance. Eurasian Oystercatcher was most tolerant to the presence of landscape elements, and Black-tailed Godwit least tolerant.

As a first step to investigate the foraging ecology of the Plain Swift Apus unicolora the Canary Islands, we studied the food brought to the nestlings. A total of 12,800 aerial prey items were identified from 32 food boluses. 97.3% of the prey items were insects, most of which (96%) were from the orders Coleoptera, Diptera, Hemiptera and Hymenoptera. Other orders represented were Dermaptera, Ephemeroptera, Lepidoptera, Mecoptera, Psocoptera and Thysanoptera. Spiders made up 2.6% of the prey items. Prey sizes ranged from 0.5 mm (body length) to 9.7 mm (average 2.46 mm, SD 0.90). There was substantial variation in the prey types among the 32 food boluses, both at the level of orders and of families. Prey size was more similar among the boluses suggesting that prey size was more important than prey type to the swifts. The results are in agreement with previous studies of swift diets.

Following recent phylogenetic work, Rockhopper Penguins were suggested to consist of two or three species. For the Southern Rockhopper Penguin Eudyptes c. chrysocome, sexual dimorphism has not been studied in detail, and only a few previous studies on penguins have investigated sexual dimorphism in immatures and chicks. Using data in the literature, we examined whether the sexual dimorphism of adults varies among the three taxa of Rockhopper Penguins and then we investigated the most reliable measurements to sex adult Rockhopper Penguins. We observed that bill length is the most useful measurement to separate males from females. To allow for sex discrimination in the field, we also examined a large dataset of Southern Rockhopper Penguins from New Island, Falkland Islands, including adults sexed via observation of behaviour, and immatures and chicks sexed genetically. We found that male adults and immatures were larger than females in bill length and bill depth and, to a lesser degree, in flipper lengths. We thus derived discriminant functions from bill length and bill depth and correctly sexed 96.2% of adults and 91.8% of immatures. In newly hatched chicks, males had a longer bill than females, but sexing was only successful for 63.5% of hatchlings. Just before the crèche age (18 and 19 days) and after the pre-fledging moult (55 days and older), all morphological measurements of chicks were significantly different between sexes, and sex determination was successful for 68.2% and 84.3% of chicks in these age groups, respectively. Consistently among age groups, bill length was the most dimorphic character in this population.

A complete moult north of the Sahara has never been reported conclusively in the Reed Warbler Acrocephalus scirpaceus complex. During a ringing program carried out in the Smir marshes (northern Morocco) 140 adults and 292 juvenile Reed Warblers were examined during four autumns in the period 2004–2008. Of these birds, 8.9% of juveniles were either in active moult (n = 17) or had completed moult (n = 9) and 48.6% of adults were either in active moult (n = 32) or completely moulted (n = 22). At least some of the moulting birds were of local origin (i.e. Smir breeding population), since 14 males and one female were captured in autumn and later recaptured in spring showing signs of breeding activity, or captured in spring and recaptured moulting in autumn. Also, one juvenile captured in May was recaptured in November while moulting. Capture history of some moulting birds indicate that they over-winter locally and others most likely winter somewhere else in Morocco (i.e. north of the Sahara). Therefore, we report the discovery of a (partly) sedentary population of an as yet undescribed taxon of Reed Warblers in Smir marshes, Morocco. The relationship of these to the Eurasian A. scirpaceus and African A. baeticatus Reed Warblers remains to be investigated.

Greater Spotted Eagle Aquila clanga and Lesser Spotted Eagle Aquila pomarina are hybridising Eurasian raptors, but our knowledge of hybrid fertility is poor. Here, I present a case of interbreeding between a F1 hybrid spotted eagle male and a Lesser Spotted Eagle female in Estonia. The hybrid was first studied and ringed as a nestling in 1999, showing characters of both species. In 2009, the same bird was caught and, surprisingly, this ten-year-old individual had retained several immature characters. Again, characters of both species were recorded in the hybrid, as well as in his backcross-offspring. At the nest site level, the habitat of the hybrid's hatching site was intermediate but its nesting site was typical of A. pomarina. At the landscape level hatching and breeding sites resembled habitat typical of A. clanga in Estonia.

We investigated the breeding biology of the Brown Noddy Anous stolidus at its southern-most breeding locality, cold-temperate Gough Island (40°S) in the South Atlantic Ocean. We monitored 19 nests over three seasons for breeding schedules, and measured the growth of eight chicks and six fledglings during the 2005/06 breeding season. Across all seasons, egg-laying occurred between 2–12 December, mean incubation was 37 days and median hatch date was 15 January. Three late hatch dates suggest that replacement clutches can be laid if failure occurs early in the season. Chicks fledged after a mean of 46 days, but remained in the vicinity of the nest and were provisioned by adults for up to 11 days. Hatching success was 88%, fledging success 92% and breeding success 81%, which is higher than at most other sites. The size, chick growth-rates and pre-fledging fast displayed by Gough's Brown Noddies are similar to that of Brown Noddies breeding at other mid-latitude Atlantic locations. These similarities of these migratory noddy populations, as well as mirrored breeding schedules suggest a single mid-latitude Atlantic meta-population.

Tristan Thrushes or Starchies Nesocichla eremita are known to feed on seabird eggs. We show they are able to open the eggs of birds as large as small albatrosses. Starchies were involved in almost half of all egg losses by Great Shearwaters Puffinus gravis during the early incubation period in a small study colony at Inaccessible Island, South Atlantic Ocean. They also enter burrows to remove and kill petrel chicks up to at least 70 g. Starchies are thus potentially significant predators of seabird eggs and chicks, and may select against egg neglect and early cessation of brooding by burrowing petrels at the Tristan islands. Starchies previously were recorded killing adult White-bellied Storm Petrels Fregetta grallaria at Inaccessible Island. This behaviour now includes White-faced Storm Petrels Pelagodroma marina. It is likely that the Starchies hunt adult storm petrels directly, taking them from their burrows.