During the course of their lives many vertebrates live and forage in environments characterized by different salinities and must therefore respond to changes in salt intake. This is particularly true for numerous species of migratory waterbirds, especially those that routinely commute between saltwater and freshwater wetlands throughout their annual cycle and/or within a season. These birds have evolved a suite of morphological, physiological and behavioural mechanisms to successfully maintain osmoregulatory balance. However, relatively little is known about the impacts of salinity on the distribution, physiological performance and reproductive success of waterbirds. Here I review the current knowledge of the physiological and behavioural mechanisms through which waterbirds cope with contrasting salinities and how some of the adjustments undertaken might interfere with relevant aspects of their performance. I argue that, because of their strong reliance on wetland ecosystems for foraging and breeding, waterbirds may be particularly vulnerable to climate-induced changes in salinity, especially in arid or semiarid tropical areas where increases in both temperature and salinity may affect their body condition and, ultimately, survival prospects. I conclude by offering some suggestions for future research that could take us beyond our current level of understanding of avian osmoregulation.

A key topic in foraging ecology is whether a particular prey type is consumed because it is more abundant or easier to catch, or because there is a specific preference for it. The great tit Parus major is an ideal species for studying this topic. Although it is traditionally regarded as a caterpillar specialist, in certain periods, e.g. during the breeding season, or areas, such as the Mediterranean forests, the great tit seems to show a preference for spiders. We conducted food choice experiments with captive birds to ascertain which of these two main prey types (caterpillars vs. spiders) was preferred outside the breeding season when there was an opportunity to prey on both food types. In conclusion, we found that, regardless of any variation in the supply-demand ratio and the amount of food available, Mediterranean great tits showed a preference for spiders.

Bird migration is usually performed in several consecutive flights, interrupted by stopovers when birds rest or replenish their fuel loads. As a result, migrants must decide when and where to land. Here, we studied the effects of meteorological conditions (wind and rain) and age (used here as a indicator of bird experience) on the probabilities of sedge warblers Acrocephalus schoenobaenus landing at a stopover site in northern Iberia. Data were collected over three consecutive years at a ringing station during the autumn migration period. We used reverse-time capture-mark-recapture models to estimate seniority, γ (i.e., the probability that an individual at time t was already present in the population at time t - 1), as an indicator of landing decisions, since 1- γ represents the probability of recording new individuals (i.e. recent landings). We ran 14 models with the above mentioned variables, four of which were best supported by the data. In these, only rain showed a significant positive effect on γ, indicating that birds of any age class avoid flying during rainfall and prefer to interrupt their migration. These results are similar to those obtained from an analysis of day-to-day variation in first captures that was used to validate the usefulness of capture-mark-recapture models. They suggest that CMR models can serve to study bird landing decisions during migration in some specific cases.

The population of little egrets Egretta garzetta in Spain is over 20,000 adult breeding birds, making it one of the largest in Europe. Apart from its population size and population trends, the parameters associated with the dynamics (e.g., survival) of the species in Spain are virtually unknown. Our aims were to develop models to assess (1) the colony growth rate, and (2) apparent survival rate of a colony of little egrets breeding in northern Iberia. We used capture-recapture data of little egrets ringed as chicks within the colony, of normally < 30 adult breeding pairs, over a 14-year period starting in 1999. Colony size was observed to be increasing in a linear tendency broken by specific catastrophic events: a very strong hailstorm in 2004 and a pair of peregrines Falco peregrinus that killed several adults in 2005. By 2012, the colony had still not reached the size that it was before the decrease, so it can be concluded that sporadic catastrophic events can have a significant effect on colony size and subsequently population size, especially in small colonies. Annual apparent survival (±SE) was constant and differed between age classes (first-years: 0.15 ± 0.05; adults: 0.78 ± 0.06). Our survival estimate was relatively high compared with other little egret populations, especially for adults. This result, however, may not necessarily apply to other colonies given our small sample size and the lack of data on other factors that also affect the dynamics of the study population.

The yellow-legged gull Larus michahellis is usually considered as an opportunistic species that depends on food derived from anthropogenic activity, such as garbage and fishery discards. However, although it has become a problematic species in many Mediterranean countries, there is still no information about its status in Tunisia. The aim of this work was to assess the differential use of marine and terrestrial resources by the yellow-legged gulls breeding in an urban area on Chikly Island. Dietary reconstructions were performed through the analysis of regurgitates and δ¹³C, δ³⁴S and δ¹⁵N of fledgling's feathers. Contrary to most Mediterranean breeding colonies, and to our expectations, the mixing model showed that yellow-legged gulls from Chikly are above all marine foragers. Whereas the Lake of Tunis was the principal source of food in 2005 and 2007, chicks from 2006 were fed mainly with prey from the Gulf of Tunis. Although the Gulf is located further from the breeding colony and has less fishing activity than the Lake, our study demonstrated that it is used as an alternative foraging habitat. The Bayesian mixing model approach proved to be a useful tool for evaluating temporal variations in the feeding ecology of the colony, which is a relevant information for the management of a wild species. This study also demonstrated the importance of isotopic variability among years for inferring diet diversity and food availability for the colony, thereby allowing demographic forecasts when trophic resources vary in abundance or the foraging habitat is disturbed.

How birds adapt to urban life is a key question in evolutionary and conservation biology since urbanisation is one of the major causes of habitat loss worldwide. Some species are able to deal with these anthropogenic changes but a shortage of nesting sites may preclude them from breeding in cities. We conducted a baseline survey of the cliff-nesting burrowing parrot Cyanoliseus patagonus around Bahía Blanca (Argentina), estimating a minimum total of 1,361 pairs breeding at 24 sites (colonies) in 2013. The species showed facultative colonial behaviour, colony size varying between 1 and 300 pairs. Most colonies (68%) and pairs (74%) occupied human-made substrates, mostly quarries but also water wells. Colony size was strongly correlated to the extent of both natural and anthropogenic nesting substrates, suggesting an ideal free distribution of pairs according to the availability of nesting resources. Anthropogenic substrates have certainly allowed population expansion in what is a rather flat landscape with a shortage of cliffs and ravines, as well as urban breeding by a large part (61%) of the surveyed population. This is currently one of the largest populations of burrowing parrots, a previously abundant species that is progressively threatened by persecution and nest poaching for the international pet trade.

We investigated nest building behaviour of great tits Parus major in relation to altitudinal temperature gradients in Lower Austria. We hypothesised that colder environments at higher altitudes would select for a nest construction that increases thermal nest insulation. We collected data on nest architecture from 11 nests and on nest components from 33 nests along an altitudinal range (390 m) in 2010 to 2012, and experimentally measured specific insulation quality in 11 highly variable nests. Highly insulated nests included significantly more feathers than less well-insulated nests. Despite significantly lower temperatures at high altitude than at low altitude sites before clutch initiation, nest insulation quality did not increase with altitude. Moreover, we found that the date of clutch initiation was positively correlated with altitude. Birds may adjust to lower spring temperatures at high altitude by delaying clutch initiation, thus avoiding the need to invest in gathering highly insulating material.

This paper studies the factors affecting passerine (Order Passeriformes) species richness in the Western Maghreb, a region at the southwestern border of the Palearctic reputed as a primary wintering ground for many common European birds. The effect of productivity, temperature, landscape structure and geographical location on bird richness was explored at 220 localities across Morocco. The models resulting from multivariate analyses supported the effects of productivity, temperature and landscape cover on bird richness, with higher numbers of species occurring in warm farmlands of the northwest. The most suitable areas for birds avoided the cold and arid expanses of the Atlas Mountains and the Sahara and overlapped with the most human-impacted sectors. Within these areas, we detected an interspersed distribution of sectors of high bird richness and low human incidence. These sectors can be used as priority targets for conservation programmes of common birds during the winter.

Studying various aspects of the biology of a species of conservation concern allows us to improve our understanding of, for example, how the particularities of the landscape matrix influence its occurrence. The Lower Vouga Lagoon in central-western Portugal offers an unusual diversity of natural and humanised biotopes in an agricultural-wetland complex mosaic. This study aimed to identify the factors that may influence the occurrence and abundance of a diurnal raptor, the marsh harrier Circus aeruginosus, in this kind of landscape. The marsh harrier is a top predator that is considered as an umbrella species, i.e. one whose conservation may also help preserve and promote biodiversity in general in its community. This study provides potentially valuable information on management and conservation strategies in both natural and agricultural areas. We found that natural habitats, such as reedbeds, are a key habitat for this predator, providing shelter, food and suitable nesting sites. Despite the general negative effect of human pressure on the occurrence of marsh harriers, the species seems to tolerate and even benefit from humanised environments, such as rice fields, which constituted the preferred foraging habitat during the non-breeding period. Nevertheless, the degree of disturbance should be carefully considered, since road density and agricultural machinery negatively influenced the presence of the species in the landscape, particularly during the breeding period. The preservation of the distinctive features of the studied mosaic is very important. It is also necessary to establish a conservation programme involving the local human community.

We compared the performances of the strip transect count method and the distance sampling method during colony surveys of large gulls to estimate the total number of nests. Ten colonies were surveyed by both methods. Nest detection probabilities varied from 0.519 ± 0.064 to 0.706 ± 0.049 and the average nest detection probability was 0.614 ± 0.015. Nest densities were highly variable, ranging from 77 nests/ha to 717 nests/ha. Estimates of the number of nests obtained by the strip transect count method averaged 9.3% lower than those obtained by distance sampling but by as much as 31% in some colonies. Underestimation by the strip transect counts increased at high nest densities (Kendall t = -0.556, P = 0.032). The strip transect method needed on average 6.5 observers per colony surveyed, whereas the distance sampling method required 1.4 observers per colony. In addition, the mean time spent per colony was 3 hours vs 1.7 hours for the strip transect and distance sampling methods respectively. Combining both these measures of effort, distance sampling required on average 87% less effort in the field than the strip transect method. We strongly advocate the use of distance sampling for surveys of large gull colonies.

We present data on home range sizes and spatial parameters of six non-breeding bearded vultures Gypaetus barbatus (one adult, four subadults and one juvenile) using Argos satellite telemetry in the Pyrenees (Spain-France) between 1999 and 2006. None of the birds left the Pyrenees during the tracking period and all individuals included supplementary feeding stations (SFS) in their home ranges. Home range areas reported here were smaller than those previously reported in South Africa and slightly larger than those reported in the Pyrenees and the Alps. Overlap between home ranges and SFS shows the importance of predictable sources of food, especially for inexperienced juvenile birds. Satellite telemetry facilitates improved insight into the bearded vulture's spatial ecology and behaviour, which is key for the conservation of this threatened species.

This paper explores the numerical trends of winter ring recoveries of the European robin Erithacus rubecula in Spain to determine whether the number of extra-Iberian individuals has decreased in recent decades. Results show that despite the increasing numbers of ringed and controlled robins, the number of recoveries of individuals of northern origin has decreased since the 1970s. This pattern is congruent with the northwards retreat of the wintering grounds of some partially migratory bird species that may be due to global warming.

The Eurasian scops owl is one of the least known European nocturnal raptors. The species is declining throughout its distributional range, thus giving concern for its conservation status. We investigated seasonal shifts in its habitat use and diet in central Italy, where scops owl is a resident species in Central Tuscany. The owls used grasslands and human settlements during the breeding period, while woodlands were mainly used during the winter. The main prey species in the diet during the warm period were grasshoppers (Orthoptera, Tettigoniidae), whereas shrews (Soricomorpha) constituted the main prey during the winter. Thus, protecting extensive grassland would not suffice to conserve resident populations of Eurasian scops owls and preservation of mature deciduous woodlands with trunk cavities is also recommended.

This section includes the abstracts of some of the PhD-Dissertations submitted in Spain during the 2013–2014 academic year as well as some others not published in earlier volumes of Ardeola. They are in alphabetical order by University where they were presented and, then, by year and alphabetical order of the author's surname.

^* This issue includes exceptionally two theses of the year 2014–2015. We believe it is important to provide this information in this volume instead of postponing its publication to 2015.

The Books Reviews section of Ardeola publishes reviews of the publications received and deposited in the library of SEO/BirdLife. Most reviews are solicited by editors to individual contributors, but additional reviews are always most welcome.

Reviews express the opinions of the individual reviewer. As such, they are subjetive assessments and do not necessarily reflect the opinions of the editors or any official policy of SEO/BirdLife.