Spatial and temporal distributions of resources and habitats often influence breeding systems. These influences are particularly relevant in those species that exhibit variable breeding systems. We studied such a species, the Penduline Tit Remiz pendulinus. This small passerine bird has sequential polygamy by both sexes, and evidence suggests intense sexual conflict between males and females over care. We estimated habitat structure by scoring the vegetation important for nest building and foraging in the immediate surroundings of the nest. Using four principal components we show that sites with more abundant vegetation are occupied earlier than sites with sparse vegetation. However, habitat structure does not predict mating success or reproductive success, and it neither predicts which parent (the male, the female or both) deserts the clutch. We therefore suggest that habitat structure does not have a direct effect on reproductive success or on the resolution of sexual conflict in Penduline Tits. Specific aspects of habitats, such as food and nest material availability, remain to be tested.

A field study at the Dutch IJsselmeer on colonial nesting of Great Crested Grebe Podiceps cristatus over four breeding seasons focused on the phenomenon of breeding aggregation. Grebes settled in two types of habitat: ‘Bulrush’ and ‘Reed’. Pairs in Bulrush nested later in the season, and therefore produced smaller clutches, compared to pairs breeding in Reed. Breeding pairs showed high variability in the timing of arrival, nest building and egg laying (‘laying date’). Pairs that started nest building early in the season took more time to produce a clutch. They also produced larger clutches, but experienced more egg loss, compared to pairs breeding later in the season. Corrected for laying date, year and habitat, there was no effect of coloniality, as measured by nearest neighbour distance, on clutch size and egg loss. I conclude that colonial breeding in the Great Crested Grebe results from suitable habitat progressively filling-up with breeding pairs, without accruing any reproductive advantages.

Systematic sex-related differences in size and plumage are informative of sex-specific selection pressures. Here, we present an analysis of sexual dimorphism in body size and plumage of Black-tailed Godwits Limosa limosa limosa from a breeding population in The Netherlands. Molecular methods were used to unambiguously assign the sex of captured birds. To quantify breeding plumage, we developed nine plumage scores. These scores describe the intensity of orange in the breast plumage, the extent of black bars on the belly, the coverage and number of breeding feathers on the back, the conspicuousness of the white eye stripe, the extent of white plumage on the head, the percentage of orange colour in the bill and the percentage of white and black spots covering the neck. Most females were structurally bigger, and had a greater body mass. Nonetheless, we found a greater overlap in bill length between the sexes than expected on the basis of literature data: biometrics alone are not sufficient to correctly discriminate between the sexes. Black-tailed Godwits are sexually dimorphic mostly with respect to the amount of white spots on the neck, females being of lighter colour than males. In addition, females showed fewer black bars and less orange on the breast, had more white in the head and fewer and a smaller extent of breeding feathers on the back. Interestingly, we found a genotypic polymorphism on the sex-related CHD1 gene on the Z chromosome, commonly used for molecular sexing in birds. Males of the less frequent genotype had significantly more white in their plumage and had fewer black bars on their breast, while in females no differences between the two genotypes were found.

We studied the development of breeding plumage in 641 Ruff Philomachus pugnax males during spring in 2004–2006 in southern Belarus with special emphasis on the growth rate of ruff and tuft feathers, which are the most colourful and spectacular parts of the male plumage. During northward migration, male Ruffs arriving in the end of March or early April showed a mixture of winter and striped feathers. The first adults with fully developed breeding plumage were recorded in the last 10 days of April and the proportion of individuals with breeding plumage gradually increased through spring. However, individuals with at least traces of winter or striped plumage were caught during the whole study period. Birds did not shed the whole winter plumage at once, which is typical for Ruff males in western Europe. Immature (second year) birds were less advanced in developing breeding plumage than adults. Only 20% of all 55 trapped second-year males were in full breeding plumage. During the main migration period there were no annual differences in the growth rate of breeding plumage feathers. Ruff lengths increased 1.6 mm/day in adults and 1.5 mm/day in second-year males, whereas the tuft grew 1.1 mm/day in adults and 1.0 mm/day in immatures. Although growing rates of ruff and tuft feathers were similar in immatures and adults, immature males started to moult into breeding plumage later than adults, resulting in less developed breeding plumage when they departed to the breeding grounds. As second-year males had lower body mass and slower body mass increase than adults, it was proposed that energetic constraints during migration are the main reason of delayed moult into breeding plumage in immature birds.

The Netherlands holds internationally important numbers of Black-tailed Godwits Limosa limosa, and reports of a substantial population decline have prompted concern. One way of narrowing the list of possible causes of this decline is to identify the demographic processes responsible. For this reason, we conducted a survival analysis for the period 1960 to 2000 based on dead recoveries of godwits. Although declining sample sizes and falling reporting rates reduced the precision of estimates in later years, we concluded that adult survival had dropped significantly in the late 1990s from 0.77 to 0.40. Data were too sparse to estimate juvenile survival in this period. Apart from this sharp drop, we found no evidence of long-term trends in either first-year or adult survival. We found no evidence for effects on survival estimates of shifts in the spatial distribution of recoveries or in the reported causes of death. These large-scale analyses of birds recovered dead complement more intensive mark-resighting studies at individual sites. Given the falling reporting rates of dead birds and consequent loss of precision of survival estimates, intensive mark-resighting programmes have an increasingly important role to play in the study of survival rates.

In shorebirds, the prevalence of successive clutching and types of associated breeding strategies differ among species, environments and individuals. Although several studies have examined successive clutching behaviour in holarctic species, little research has been conducted in the tropics. To assess the full range of reproductive strategies and better understand breeding constraints in tropical environments, we characterised successive clutching behaviour in 54 and 79 colour-banded Malaysian Plovers Charadrius peronii over two years in the Gulf of Thailand. We also examined monthly changes in clutch size, clutch volume, prey availability and breeding success because temporal variability in breeding conditions can affect the prevalence, timing of, and parental role-division between successive clutches. Short intervals between clutches, successive monogamy, high within-season site fidelity, double-brooding, and complete biparental care were general characteristic of successive clutching behaviour. We did not detect any declines in clutch size, clutch volume, prey availability and reproductive success during the course of the breeding season. For Malaysian Plovers, the stable and progressively favourable prey supply and weather conditions, lack of migration, and intense competition for breeding habitats may have contributed to a breeding system constrained more by habitat availability than by time. In these environments, pairs may retain mates and breed multiple times during the long breeding season.

Hybrid zones provide a unique opportunity to study the dynamics of isolation barriers. Pre-zygotic isolation through assortative or conspecific mating is thought to be an important aspect of reinforcement and speciation. Although assortative mating has received much attention and nearly a hundred theoretical models have been published, there is a large gap between theory on the one hand and empirical data on the other. To fill this gap, I carried out a meta-analysis on 58 studies which were identified as suitable for the analysis. Most studies had been carried out in the field (n = 52), and six were based on mate choice experiments. Fifty-three studies used plumage scores and five used genetic evidence to assess parental types. I found no correlation between the magnitude of effect sizes and date of publishing (r = 0.181, P = 0.174, n = 58). A fixed effects model without any underlying model structure showed a heterogeneity of Q_total = 5454.6 (df = 57; P < 0.001) and a significant mean effect size of 0.47 (95% CI 0.46–0.48). The results of the meta-analysis indicate that there is a significant effect of medium strength of assortative mating in avian hybrid zones. By partitioning the data, I found that effect sizes were very large in mate choice trials, and medium in observations in nature. Based on the inspections of the CIs of the mean effect sizes, assortative mating appeared strongest in Passeriformes and Charadriiformes hybrid zones. Further, assortative mating was stronger in narrow hybrid zones compared to wider ones but I found no difference between stable and moving zones.

Pre-migratory and migratory movements of Montagu's Harrier Circus pygargus, a long-distance migrant, are poorly documented by ring recoveries and observations. In the present study, we tagged 10 adult Montagu's Harriers in NE Spain with satellite transmitters and tracked their movements until their arrival on the wintering grounds. To identify the end of the breeding season and the onset of the migration based on our satellite-telemetry data we developed and applied a statistical approach, defining the time period between these two events as the pre-migratory stage. We then compared habitat preferences during the breeding season and the pre-migratory stage. The duration of the pre-migratory stage averaged 42 days, with harriers leaving the breeding areas between 4 June and 27 July, and the onset of the migration taking place between 25 July and 4 September. Staging areas used during pre-migration were located at higher altitudes than the breeding grounds, and were characterized by the presence of shrublands and cultivated areas, mainly cereals. Montagu's Harriers' use of these sites is likely to be related to food availability: at higher altitudes, peak abundance of Orthoptera, their main prey source, occurs later in the season than in the lowland breeding area. Pre-migratory movements may also play an important role in the search for suitable breeding sites for future use.

In the present study we describe the morphometrics of 97 live Eurasian Griffon Vultures Gyps fulvus collected on the island of Crete (Greece) and a sex determination model on the basis of various field techniques and multivariate data analysis. We determined the sex of 49 individuals with sex-specific DNA markers and polymerase chain reaction using DNA extracted from blood samples. Adult birds were generally larger than young ones with the wing chord being the only significantly different character. Male Griffons were smaller than females for most body characters and significantly larger (c. 3–5%) for head length, head width, bill length and bill length including the cere. A stepwise discriminant function analysis showed a high predictive power in gender determination by classifying 94.1% of the individuals of known sex that was not reduced by a jackknife cross-validation technique.

Native to the Indo-African area, the Cattle Egret Bubulcus ibis is now a cosmopolitan species, still in great range expansion. The factors affecting breeding success of the species remain however poorly known, and here we investigate the breeding biology of the Cattle Egret in a new breeding population in the Soummam Valley (Petite Kabylie, Algeria). The installation chronology and nest site selection are described, and their effect on breeding success investigated. The nesting season lasted generally from the end of March to the end of July. Clutch size, number of hatched chicks and breeding success were low compared to other breeding areas in the Mediterranean. The first Cattle Egrets arriving at the colony in March selected the highest trees and the highest nest supports close to the trunk. With new arrivals during the course of the season, a gradual decrease was observed in the height of the nests which were progressively built away from the trunk. This selective behaviour allowed the first installed pairs to have a better breeding success. This phenomenon is discussed here within the framework of territoriality and the breeding advantages of being high ranking in the ‘territorial hierarchy’ for the individual.

Species may act simultaneously as competitor and predator for other species at the same trophic level. This is known as Intraguild Predation (IGP). Most research on this topic describes the final steps of this phenomenon, when one species suffers lost progeny or decreased numbers due to predation and competition by another species. However, little is known about the mechanism that regulates this interaction in previous steps. In this work two species of the same guild (Little Owl Athene noctua and Barn Owl Tyto alba) were selected to test the hypothesis that the hunting and social behaviour of the Little Owl would be conditioned by the presence of Barn Owls. Nine Little Owls were radio-tracked and monitored for nine months. 1223 fixes were obtained and 250 hours of listening were recorded. Moreover, during this time Barn Owls were detected 66 times screeching, hunting or flying in the same areas as the monitored Little Owls. The subsequent activity (movements and voices) of tagged and untagged Little Owls was observed during 30-minute periods. The results show that Little Owl behaviour was affected by Barn Owl presence. When Little Owls noted the presence of Barn Owls, they stayed quiet and silent, or alternatively, sought refuge in the branches of trees or in secure holes in buildings, resuming their activities minutes later, when the risk of predation was presumably lower. This behaviour may have enabled survival and successful breeding of Little Owl in close proximity to Barn Owls.

This study explores the relationship between richness of bird species and climate in Spain, distinguishing groups of species according to biogeographic type. Species richness proved to be related to temperature but in a different way for each of the biogeographic groups. While controlling for other variables, species richness initially increased with temperature, but dropped when temperature increased further. As this drop was less strong in southern species than in northern species, a positive relationship between the percentage of southern species and temperature emerged. Moreover, the percentage of southern species varied with human population density, altitude range and precipitation in a quadratic way.

Migratory movements of juvenile Purple Herons from the Camargue area in France were studied by satellite-tracking. Six juvenile birds were fitted with transmitters in early July 2004. Of these six, four successfully started migration in September. Tracked birds followed a western migratory route, heading out south-south-west, towards Spain, the Balearic Islands and then Algeria. They pursed their flight either south-west to the Moroccan Atlantic coast or straight to Mauritania, flying over the Sahara desert. Flight speed could be estimated for one of the birds and was about 40 kilometres per hour. The results of this study are consistent with previous ring recovery data and provide additional knowledge on the speed and departure date of juvenile Purple Herons during autumn migration.

Flock-fishing, i.e. when a tight group of birds moves in a coordinated way under more or less synchronous diving, is common in cormorants Phalacrocorax spp. and mergansers Mergus spp., but is said in the major handbooks not to occur in Great Crested Grebes Podiceps cristatus. The present communication reports repeated observations of such flock-fishing at a South Swedish lake during summer. Great Crested Grebes' dispersion in relation to diving activity within large aggregations on a nearby lake in late autumn — early winter is also described.

Adult penguins eaten at sea form a large proportion of the diet of giant petrels Macronectes spp. It is widely assumed that they are scavenged after being killed or injured by more agile predators such as fur seals Arctocephalus spp. We observed non-breeding Northern Giant Petrels M. halli hunting and killing Northern Rockhopper Penguins Eudyptes moseleyi offshore from a penguin colony on Nightingale Island, Tristan da Cunha. Penguins were killed at an average rate of 0.4 h^-1 spent hunting by petrels. The most successful technique was a stabbing vertical lunge as a penguin surfaced or swam close to the surface near a petrel, but some were caught when a petrel dropped onto a group of penguins from the air, or when penguins fell back into the sea after attempting to land. Petrels also tried to sneak up on penguins resting on the surface by swimming towards them while lying flat on the water, but none of these ‘stealth’ attacks was successful. Penguins killed were grasped by the hind-neck and held underwater for 5–6 minutes until they stopped struggling, and then were eaten. Only 18% of penguins caught were killed; the remainder were dropped before they were subdued, apparently because they were not grasped correctly. One Southern Giant Petrel M. giganteus also attempted to catch penguins, but was not successful. Our observations suggest that not all penguins recorded in diet studies of giant petrels are scavenged.

Spring staging is an important period influencing reproductive success for migratory birds. During this period, female geese must accumulate reserves for subsequent migration, egg laying and incubation. They may increase feeding opportunities by being guarded by dominant males protecting a large feeding area and providing feeding time, and/or having themselves a high dominance status. Using paired adults of Dark-bellied Brent Geese Branta bernicla, we tested if males had higher dominance scores than females, if larger individuals had higher dominance scores than smaller ones and if dominance ranks of paired partners were correlated. Our results supported the first and third predictions while, once controlled by sex, body size was not correlated with adult dominance status.

An individually colour-ringed House Martin Delichon urbica, molecularly confirmed to be a female, after attending a first brood in early July 2007, became engaged with two second broods at the same time, one with the original mate of the first brood. The two nests were at opposite sides of the same building and not within each other's sight. During simultaneous observations on 1 September, the female was feeding large nestlings at each of the two nests, alternating between bouts of repeated feeds. This behaviour by a female with perhaps below-average survival prospects (she had a slightly damaged wing tip and a low weight at first capture) can be interpreted as a case of helping relatives or polyandry.