Mangrove forests attract many insectivorous birds. Bird density in West African mangroves in January–March 2014 is higher in Avicennia (21 birds/ha canopy) than in Rhizophora (11 birds/ha). The Palearctic species are dominant in the most northern mangroves (14–16°N), but further south resident birds become as numerous as migrants (11–12°N). The European Reed Warbler Acrocephalus scirpaceus is the most common winter visitor in West African mangroves between 12 and 16°N, with an estimated total of 4–6 million birds, which may account for 30–50% of the European population. The mortality of European Reed Warblers while crossing the Sahara desert in spring is higher when their Sudan-Guinean wintering areas have been drought-stricken in the preceding winter. European Reed Warblers wintering in mangroves suffer the same fate, because mangroves in the Sahel region massively die off in drought years.

To be able to set priorities in species conservation planning, we need to know how these species prioritize the environment themselves, i.e. what they consider to be better and worse sites. We present a unique and relevant case from tropical West-Africa based on 20 years of monthly counts of wetland sites spread along the 550 km long coast of Ghana. The Ghanaian Sanderling Calidris alba population increased almost fourfold from average monthly total counts of c. 1350 Sanderlings to 4850 during the study period. Interestingly, with this considerable increase, the sites with the larger numbers at the start of the survey showed the smallest relative increases during 20 years of monitoring. This pattern is consistent with a buffer effect and suggests that with an increasing overall population the best quality sites are filled up, so that additional birds will be forced to use lower quality sites. The preferred site in Ghana, a stretch of beach near the village of Esiama between the Amansuri-Ankobra estuaries, is now entirely unprotected. We argue that the site should be placed higher on the conservation agenda given the fact that up to 3.5% of the Sanderling population connecting Greenland with West- and southern Africa rely on this site.

Bird migration is generally scheduled to avoid other energetically expensive events in the annual cycle (e.g. moult) and seasons when survival can be difficult (e.g. northern winters). Purple Sandpipers winter at relatively high latitudes compared to other waders. It is suspected that the majority that winter in Britain and Ireland originate from Canada, but there is no primary evidence of their breeding grounds and migratory routes. These birds, characterised by their long bills, start to arrive in Britain and Ireland in late October/early November, after completing their post-nuptial moult at an unknown location. Fifty geolocators were attached to Purple Sandpipers in northern Scotland and southwest Ireland and we established for the first time their Canadian origin (Baffin Island and Devon Island), migration routes and post-nuptial moulting areas. Spring departure from Scotland and Ireland took place mainly in late May, followed by staging in Iceland and/or southwest Greenland before reaching the breeding grounds. Those that staged in Iceland departed earlier than those that flew directly to Greenland. Post-nuptial moulting areas were in southern Baffin Island, northern Quebec/Labrador (the Hudson Strait), and southwest Greenland. Migration from Baffin Island and Labrador took place during late October – early November, and during mid to late December from Greenland, usually in a single trans-Atlantic flight. Therefore, this migration was scheduled at a time when most other wader species are already on their wintering grounds. No birds staged in Iceland on the return trip. The flight from Baffin Island to Scotland and Ireland was accomplished in about 2.5 days at an average speed of about 1400 km per day. Freezing of coastal waters may be the reason for the eventual departure from the Hudson Strait. The more northerly route via Iceland, taken in spring by most birds, and the more southerly route in early winter were associated with seasonal shifts in the Atlantic low pressure systems (depressions) whose anti-clockwise wind-flows would have assisted flights.

We measured primary moult scores of 1051 Eurasian Golden Plovers Pluvialis apricaria staging in pastures in The Netherlands from 1978 to 2011. We hypothesized that moult may have advanced due to earlier breeding resulting from global climate change. At the same time, intensification of agricultural practices has changed the environment on which the Golden Plovers depend during migration and staging, which may have affected their condition and moult schedule.

Primary moult has advanced by 8 days from 1990 to 2011, without visible changes preceding 1990. This suggests that long-term changes in weather might have caused the change in moult timing. In the absence of the variable year, the North Atlantic Oscillating (NAO) index, averaged over September–October, significantly correlated with timing of moult. However, this was a weaker relationship than that of year and timing of moult. Apparently, year correlates better with relevant weather parameters than NAO. Because moult speed at the staging areas has not changed from 1978 to 2011, the birds must have started moult earlier. Advanced breeding has been shown to have occurred in several bird species breeding in northern temperate latitudes. Golden Plovers start to moult during breeding, and therefore we think that the advancement of moult has been the result of an earlier start of breeding and not of changes in agricultural practice in The Netherlands.

To help restore food availability for birds, arable field margins (extensively managed strips of land sown with grasses and forbs) have been established on European farmland. In this study we describe the effect of field margins on the diet of Eurasian Skylark nestlings and adults living on intensively managed Dutch farmland. We tested the hypotheses that field margins offer a higher diversity of invertebrate prey than intensively managed crops, and that the diet of nestlings receiving food from field margins will therefore be more diverse than that of other nestlings. Field margins had a greater variety of invertebrate prey groups to offer than the intensively managed crops. Coleoptera were the most frequently and most abundantly eaten prey group by both adults and nestlings. Together, Coleoptera, Diptera, Lepidoptera, Hymenoptera and Araneae accounted for 91% of the nestling diet. Nestlings ate larger prey items and a larger proportion of larvae than adults. Almost 75% of both adults and nestlings consumed plant material, perhaps indicating a scarcity of invertebrate resources. When provided with food from field margins, the mean number of invertebrate orders in the nestling diet increased significantly from 4.7 to 5.5 and the number of families from 4.2 to 5.8 per sample. Thus, birds that used field margins for foraging could indeed provide their young with more invertebrate prey groups than birds only foraging in crops and grassland.

Reproducing research results is one of the cornerstones of science. However, few biological findings are actually replicated. Here, we repeat a study done more than 35 years ago on social information use in Barnacle Geese. In the original study, models of Barnacle Geese were used to measure how they attracted wild Barnacle Geese (Drent & Swierstra 1977). Models were placed in different locations in a pasture and these models attracted many wild Barnacle Geese, providing strong evidence for the use of social information. 37 years later we repeated this experiment, using the same models, the same area and a similar research protocol. Despite an abundance of wild Barnacle Geese in the area frequently flying over the models, the models did not elicit a landing response. In line with the original study, we scored vigilance rates and abundance of geese. Comparing these data to previous records we found that total abundance increased but that vigilance rates were lower than previously recorded. The decreased vigilance suggests that the landscape has become safer or that competition between geese has intensified; both could explain a reduced use of social information. More generally, our study shows the importance of repeating experiments in ecology, especially in a rapidly changing world.

Chick body condition can be a sensitive indicator of local environmental conditions and has been shown to be correlated with chick survival. Designing a reliable index of chick body condition for a given species from a single measurement point requires knowledge about the extent of variation in body size, about chick age and about the relative sensitivity of the growth of different biometric measures to variation in environmental conditions. To gain this knowledge, we describe sex-specific variation in growth of several morphometric measures and body mass of Eurasian Spoonbills Platalea leucorodia. We repeatedly measured 35 chicks that grew up in small colonies on the island of Schiermonnikoog to derive detailed growth curves until fledging (based on the 12 surviving chicks) and to assess the extent of reduction in growth of starved chicks measured at least twice (n = 11) compared to those that survived. Growth curves until fledging were compared with biometric measurements of two to five week old chicks from (mostly) larger colonies of which hatching date was accurately estimated (n = 631). Growth of all measures, except the eighth primary, was sex-specific, with the most pronounced sex effect on the asymptotic values of tarsus length and body mass: adult males were predicted to become 17% heavier than females and to have 22% longer tarsi than females. Body mass and tarsus growth tended to be more reduced under food deprivation than (head-)bill and eighth primary growth. As an index of chick body condition, we propose to use the proportional deviation in body mass from the predicted body mass for a given age and sex. To do so, measurements of nearly fledged Spoonbill chicks should include at least eighth primary length to estimate age, tarsus length to estimate sex, and body mass as a measure that integrates age, sex and environmental effects.

Fishery discards in the Belgian part of the North Sea are a source of food for Herring Gulls Larus argentatus and Lesser Black-backed Gulls L. fuscus. To understand the importance of discards for local L. argentatus and L. fuscus populations, single-item discard experiments were performed at four offshore distances from the gullery of the Port of Zeebrugge, at four different stages of the breeding season (May to August 2011). We compared flock composition during discarding with the distribution of Herring and Lesser Black-backed Gulls, with respect to offshore distance from the colony as reflected by an 11-year (2002–2013) dataset of standardised ship-based surveys. Consumption of discards depended on the type of fish that was discarded, but prey selectivity by adults was reduced during the chick rearing stage. A generalised linear mixed model identified the number of scavengers following the vessel, the proportion of adults and of Herring Gulls in the flock and the frequency of food robbery events interacting with the stage of the breeding season as affecting the variation in flatfish consumption. Shifts in scavenger flock composition and discard consumption between stages of the breeding season are likely linked to variation in food requirements of the gull population along the season and to dispersal patterns towards the end of summer. Nutrient requirements of breeding adults peak during the chick rearing stage, making this a key period in terms of dependence of the breeding parents on discarded fish as food source.

We tested if Black-necked Grebe, a species in which both sexes undertake moult-migration, have an unbiased sex ratio at a moulting site in Europe, as previously found in North America and as was expected for a species with biparental care. For this we used a unique long-term dataset of 5821 grebes captured for ringing throughout the moulting seasons of 2006–2012 in the Odiel salt-marshes (SW Spain). The grebes were sexed and classified as adults (74%) or juveniles (26%). Birds ringed at Odiel were recovered over a wide area up to central Russia and south to the Canary Islands and Morocco. We report on a unique case of a strongly biased sex ratio in a moult-migrating bird species with biparental care, in which adult females were significantly more abundant than adult males in all 7 years (1.6–4.2 females per male). Biased sex ratios were not found among juveniles. Differences between North America and Europe in the sex ratios of adult Black-necked Grebes at moulting sites may be explained by the much larger American moulting sites, which would facilitate an unbiased sex ratio in North America, but not in Europe. Moulting sites in Europe may reach carrying capacity because of their smaller size, forcing the late migrating individuals (adult females and juveniles) to move longer distances to sites farther from breeding areas, such us the Odiel salt-marshes.

Eastern Curlews breed in Siberia in the boreal spring and summer and migrate to Australia in the austral spring and summer. The Eastern Curlew is notable for its very long, decurved bill; this sexually dimorphic characteristic represents approximately 25–30% of total body length. Female curlews have the longest bill of any wader. Diet and prey choice in relation to availability and profitability were examined over two non-breeding periods in Western Port in southern Australia. Diet was determined from direct feeding observations, examination of pellets collected at high-tide roosts (during daytime and night-time) and by following tracks of foraging curlews. Male and female curlews used the intertidal feeding areas differently: females used more sandy areas and males more muddy areas. This difference may be related to sexual dimorphism in bill length and could reflect substantial dietary differences. Tasselled Crab Pilumnus fissifrons was the most common prey, followed by Australian Ghost Shrimp Trypaea australiensis, Two-spined Crab Litocheira bispinosa and Sentinel Crab Tasmanoplax latifrons. The availability of prey was examined in aquaria through examination of burrowing behaviour and other activity patterns in relation to tidal movements and levels of daylight. Prey behaviour explained the greater consumption of male Ghost Shrimps and the differences in diet between day and night. More Ghost Shrimps and Sentinel Crabs and fewer Two-spined Crabs were taken during the day than during night. Prey choice was examined by measuring the calorific values of prey and potential prey species. Generally, curlews took the more energy valuable prey, but prey behaviour and prey availability mostly determined prey choice, not the energetic value of prey.