Condition of large brood in Bonelli's Eagle Hieraaetus fasciatus

Capsule Young body condition is affected by the interaction of environment (rainfall) and brood size.

Aims To investigate factors affecting offspring condition using levels of urea in plasma.

Methods We used generalized linear mixed models (GLMMs) with the levels of urea in plasma as the dependent variable and laying date, brood size, sex and year as the explanatory ones.

Results Brood size had a significant effect on offspring condition only during a year of adverse weather (heavy rainfall). During this period, young from broods of two were in poor condition compared with single broods. Conversely, brood size had no effect in the other two years analysed. Neither sex nor laying date had a significant effect on young condition. Offspring condition was not related to first-year survival.

Conclusion There is a trade-off between reproduction (brood size) and offspring condition only in years of adverse environmental conditions.     

Simultaneous effects of age and territory quality on fecundity in Bonelli's Eagle Hieraaetus fasciatus

Several factors that interact with a bird's age are likely to affect breeding performance. Because of habitat heterogeneity, individuals of different subpopulations may experience different probabilities of breeding, depending on the habitat that they occupy. The aim of this work is to test the hypothesis that age and territory quality independently affect breeding performance. We analysed data on breeding biology and fecundity at 298 breeding sites of Bonelli's Eagle Hieraaetus fasciatus in Andalusia from 1980 to 2000. Our data confirmed that age and territory quality simultaneously affect reproductive output. After controlling for the effect of year and age, breeding performance varied among territories. Independently of territory quality, the age of breeding birds affected the number of fledged young and variance in productivity.     

Causes of death in different areas for Bonelli's Eagle Hieraaetus fasciatus in Spain

The Spanish Bonelli's Eagle populations have decreased markedly because of high mortality. We recorded 424 cases of dead eagles between 1990 and 1998 in Spain which after cross-comparison corresponded to 377 individuals. Electrocution (55% of deaths), followed by direct persecution (26%) were the main causes of death. No differences in the cause of death were found between sexes. Non-adult eagles mostly died of electrocution whereas adults were mainly the victims of persecution. A log-linear model showed that these differences were associated with a difference in the spatial distribution of age classes, rather than to age or experience per se. Persecution was the main cause of death in breeding areas and electrocution in non-breeding areas. There were differences between regions: electrocution was the main cause in Catalonia and Central Spain (50% and 86% respectively) whereas direct persecution was the main cause in Levant and Northern Spain (52% and 43% respectively). We recommend that steps are taken in order to reduce eagle mortality, taking into account the differences between regions and areas.     

Breeding performance, age effects and territory occupancy in a Bonelli's Eagle Hieraaetus fasciatus population

Bonelli's Eagle Hieraaetus fasciatus is one of the most endangered birds of prey in Europe. Despite mounting interest and research, several questions regarding the conservation implications of territory occupancy and site-dependent population regulation remain insufficiently explored for this species. Here, we report on a 12-year study of the territorial structure of a Bonelli's Eagle population in southeastern Spain. No signals of population decline were found in the breeding population, as mean annual productivity was stable and the presence of mixed-age pairs in the population decreased with the years. However, the average proportion of subadults occupying territories was larger than that observed in other Spanish populations. Contrary to the predictions of a despotic distribution model, we found no significant relationship between occupancy rates and breeding parameters. Our results showed significant variations in productivity attributable to differences in the quality of individuals (i.e. mixed versus adult pairs), but no variability among territories per se (i.e. caused by habitat heterogeneity). Moreover, coexistence with intraguild species did not have any significant effect on productivity, although the proximity of Eagle Owls Bubo bubo affected the occupation rate of territories. Finally, our population does not appear to experience site-dependent population regulation, as a positive relation between mean annual productivity and density was found. The threat posed by changes in land use in the study area leads us to suggest that strict protection of current territories is necessary to ensure population persistence, and we suggest that a significant population increase is only likely if new or deserted territories become available.     

Population size,breeding performance and territory quality of Bonelli's Eagle Hieraaetus fasciatus in eastern Spain

Capsule A five-year monitoring study is described of overall population stability and differential reproductive success in relation to habitat heterogeneity.

Aims To assess the effect of the altitude and orientation on laying date and breeding performance, and analyse the effect of territory quality as a likely factor that could be regulating the population.

Methods We monitored a population of 28–33 pairs, from 2002 to 2006, counting a total of 131 breeding attempts.

Results Territories located at lower altitude showed higher mean fecundity than those located at higher altitude. The mean laying date was February 18 ± 16 days. Laying date was positively correlated with nest altitude, the coastal pairs laying earlier than those in mountainous regions. Pairs located at lower altitudes showed higher mean fecundity than those located at higher altitudes. There was no preference in mean orientation either in breeding performance or in relationship to nest altitude. We did not find a difference in breeding performance between territories classed as being at high density and those classed as being at low density.

Conclusion The population has remained stable since the first national census was conducted 17 years ago. Our results could be explained in the light of the Habitat Heterogeneity Hypothesis. We suggest a differential reproductive success in relation to habitat heterogeneity.     

Isolation and characterization of microsatellite markers in Bonelli's eagle (Hieraaetus fasciatus)

To obtain polymorphic molecular markers for population genetics and conservation studies in Bonelli's eagle populations, we screened a partial genomic library enriched for microsatellites with di‐ and tri‐nucleotide motifs [(GT) (CT) (AAC) and (GCC)]. A total of 15 polymorphic markers were obtained. The number of alleles ranged from two to eight. These markers will be very useful for paternity tests and population structure studies as well as for evaluating the outcome of conservation programs.     

Physical, environmental and human factors influencing productivity in Bonelli's eagle Hieraaetus fasciatus in Granada (SE Spain)

We analysed the productivity of the Bonelli's eagle Hieraaetus fasciatus in relation to 26 variables that account for physiography, level of human presence, land-use, climate, laying date, and nest orientation, in the province of Granada (SE Spain), where a stable population exhibits the maximum productivity value for the species in Europe. Productivity positively correlated with cliff availability within territories and closeness of nest site to SE orientation. Cliff availability permitted some pairs to choose the best nest site orientation, thereby favouring high productivity. Nests in the preferred orientation (SE) had 35% higher productivity than those towards non-preferred orientations. Higher productivity in the best orientation nests might be related to warmer conditions. High productivity in the study area could offset the main problem for Bonelli's eagle conservation in Europe, that is, the high preadult and adult mortality. Actions required to ensure the recovery of neighbouring populations must focus on the preservation of high cliff availability and the diminution of preadult mortality in southeastern Spain. This would favour restocking of the decreased northern populations by the juvenile dispersion.     

Factors influencing the decline of a Bonelli's eagle Hieraaetus fasciatus population in southeastern Spain: demography, habitat or competition?

We investigated three possible causes of territory desertion among Bonelli's eagles Hieraaetus fasciatus in Murcia (southeastern Spain): low demographic parameters, low habitat quality and competition with Golden eagles Aquila chrysaetos. From 1983 to 1997, we surveyed a Bonelli's eagle population. Abandoned and occupied territories were compared to find differences in demographic parameters (flight rate, productivity and mortality) or habitat characteristics. Mortality was significantly higher in abandoned territories. Abandoned territories also had larger areas of forest and extensive agriculture, while occupied territories had more shrublands. Competition with Golden eagles was not a determinant of territorial abandonement but interacted with human persecution of the species. Management implications are discussed.     

Status and ecology of the Bonelli's Eagle,Aquila fasciatus,in the Pentadaktylos Mountain Range,Cyprus (Aves: Falconiformes)

The Bonelli's Eagle is endangered in Europe, and the Cyprus population is estimated to be the 4^th largest in Europe. During 2011 and 2012, ten active nests were confirmed in Pentadactylos Mountains with 8 additional sites meriting further investigation. Observations suggest a varied opportunistic diet largely based on Black Rat (Rattus rattus). Lowland wetland sites are confirmed as important foraging grounds. Bonelli's Eagle is under a variety of anthropogenic threats in Pentadactylos Mountains most significantly hunting and poisoning, evidence for which are discussed.     

Limited prospecting behaviour of juvenile Eagle Owls Bubo bubo during natal dispersal: implications for conservation

Capsule Features of the breeding population and temporary settlement area influence the behaviour of Eagle Owls Bubo bubo prospecting for breeding sites during natal dispersal.

Aims To understand how prospecting behaviour during natal dispersal is affected by (i) the main characteristics of the breeding and dispersing portions of the population and (ii) main prey availability.

Methods We explored the ten-year dynamics and characteristics of radio-tagged breeders and dispersers of an Eagle Owl population.

Results During the first years following natal dispersal there was little prospecting behaviour of nesting sites and birds remained mainly within non-breeding settlement areas, bordering the sector occupied by the breeding population. Settlement areas had an abundant food supply, and low intraspecific competition and mortality. We suggest that these features of the settlement areas may reduce the willingness of individuals to search for breeding sites and may have the potential to impact on the viability of breeding populations.

Conclusion From a conservation perspective, the lengthy use of the temporary settlement areas by juvenile Eagle Owls suggests that the sites should be considered as important as the breeding areas when planning conservation strategies. Reducing juvenile mortality in settlement areas may represent an overlooked conservation strategy for long-lived species and may have a crucial effect on the viability some animal populations.     

Movements by juvenile and immature Steller's Sea Eagles Haliaeetus pelagicus tracked by satellite

Twenty‐four juvenile Steller's Sea Eagles Haliaeetus pelagicus were tracked via satellite from natal areas in Magadan, Kabarovsk, Amur, Sakhalin and Kamchatka. Nestling dispersal occurred between 9 September and 6 December (n = 24), mostly 14 September–21 October, and did not differ among regions or years. Most eagles made stopovers of 4–28 days during migration. Migration occurred 9 September–18 January, mostly along previously described routes, taking 4–116 days to complete (n = 18). Eagles averaged 47.8 km/day excluding stopovers; 22.9 km/day including stopovers. The mean degrees of latitude spanned during migration was: Kamchatka, 2.1; Magadan, 11.6; Amur, 7.3; and Sakhalin, 1.1. Eagle winter range sizes varied. Eagles concentrated in 1–3 subareas within overall winter ranges. The mean size of the first wintering subareas was 274 km², the second 529 km², and the third 1181 km². Second wintering areas were south of first wintering areas. Spring migration started between 2 February and 31 March. Two eagles from Magadan were tracked onto summering grounds, well south of their natal areas. Both had early and late summering areas. One bird was followed for 25 months. It initiated its second autumn migration in the first half of October and arrived on its wintering grounds on 26 December. The second autumn migration covered 1839 km (20.9–22.4 km/day). Unlike its first winter when it used two subareas, this bird used only one subarea in 1998–99, but this was located near wintering areas used in 1997–98. It left its wintering ground between 13 April and 13 May, and arrived on its summering grounds between 7 June and 8 July. Unlike most satellite radiotracking studies, data are presented from a relatively large number of birds from across their breeding range, including new information on eagle movements on the wintering grounds and during the second year.     

First description of migration and wintering of adult Egyptian Vultures Neophron percnopterus tracked by GPS satellite telemetry

Capsule Over two years birds showed high territorial and high winter site fidelity in the Sahel.     

Embryonic, larval and juvenile development of the roughskin sculpin,Trachidermus fasciatus (Scorpaeniformes: Cottidae)

Embryonic, larval and juvenile development of the catadromous roughskin sculpin,Trachidermus fasciatus, were described using eggs spawned in an aquarium. The eggs, measuring 1.98–2.21 mm in diameter, were light reddish-yellow and had many oil globules, 0.05–0.18 mm in diameter. Hatching occurred 30 days after spawning at 2.3–11.3°C. The newly-hatched larvae, measuring 6.9–7.3 mm BL, had a single oil globule, 9–10+25–26=34–36 myomeres and 6 or 7 large stellate melanophores dorsally along the gut. The yolk was almost resorbed, number of pectoral-fin rays attained 16–17, and two parietal, one nuchal and four preopercular spines were formed, 5 days after hatching, at 8.2–8.4 mm BL. The oil globule disappeared, and one supracleithral spine was formed, 11 days after hatching, at 8.9–9.5 mm BL. Notochord flexion began 15 days after hatching, at 9.7–10.3 mm BL. A posttemporal spine was formed 20 days after hatching, at 10.7–10.9 mm BL. The first dorsal fin spines (VII–VIII), second dorsal fin and anal fin rays (18–19, 16–18, respectively) appeared 23 days after hatching, at 12.0–13.7 mm BL. The pelvic fin spine and rays (I, 4) were formed and black bands on the head and sides of the body began to develop 27 days after hatching, at 13.8–15.8 mm BL. Newly-hatched larvae swam just below the surface in the aquaria. Preflexion larvae (8.9–9.5 mm BL), in which the oil globule had disappeared, swam in the middle layer, while juveniles (13.8–15.8 mm BL) began swimming on the bottom of the aquaria. Swimming behavior observed in the aquaria suggested that the fish started to change to a demersal existence at the juvenile stage.     

Recording movement and activity pattern of a White-tailed Sea Eagle ( Haliaeetus albicilla ) by a GPS datalogger

For the first time, we measured the home range size and activity pattern of a White-tailed Sea Eagle (WTSE) by GPS telemetry. Positions were recorded three times a day and the activity pattern were continuously recorded by two acceleration sensors. From July to January, we obtained 475 positions and calculated a 95% kernel home range of 4.53 km² and a 95% minimum convex polygon of 8.22 km², indicating a rather small area explained by an optimal habitat and by the much more precise location method used here compared to reports in the literature. Biorhythmic analysis of activity data revealed nearly no night-activity, high day-activity with no fixed daily pattern and a strong 24-h period of activity. The stability and synchronisation between the eagle's activity and the environmental 24-h period was evaluated by calculating the degrees of functional coupling (DFC) and the harmonic part (HP). Mostly, DFC was 100% (meaning that the different physiological and behavioural functions are completely synchronised to each other and to the environmental 24-h period) and the few incursions of the DFC we assumed to be caused by clinically relevant lead intoxications. The agonal stage of the WTSE was indicated by a daily decreasing activity level and HPs and highly modified day–night relationship, and decreasing DFCs at the beginning and at the end of dying process, representing changes in the activity structure. The underlying reason for the behavioural changes was found to be a lethal lead intoxication due to an oral ingestion of particles of rifle ammunition. The new technology of a combined GPS receiver and an acceleration sensor allows the automatic measuring of positions and activity of wild animals at a very precise level over prolonged periods which cannot be achieved by manpower.     

The importance of growing up: juvenile environment influences dispersal of individuals and their neighbours

Dispersal is a key ecological process that is strongly influenced by both phenotype and environment. Here, we show that juvenile environment influences dispersal not only by shaping individual phenotypes, but also by changing the phenotypes of neighbouring conspecifics, which influence how individuals disperse. We used a model system (Tribolium castaneum, red flour beetles) to test how the past environment of dispersing individuals and their neighbours influences how they disperse in their current environment. We found that individuals dispersed especially far when exposed to a poor environment as adults if their phenotype, or even one‐third of their neighbours’ phenotypes, were shaped by a poor environment as juveniles. Juvenile environment therefore shapes dispersal both directly, by influencing phenotype, as well as indirectly, by influencing the external social environment. Thus, the juvenile environment of even a minority of individuals in a group can influence the dispersal of the entire group.     

Irruptive movements and breeding dispersal of snowy owls: a specialized predator exploiting a pulsed resource

Mobility and irruptive movements have been proposed as mechanisms that could allow some diet specialists to inhabit and breed in environments with highly unpredictable resources, like the arctic tundra. The snowy owl, one of the main avian predators of the tundra, is known to specialize on lemmings during the breeding season. These small mammals are also well known for their tremendous spatial and temporal variations in abundance. We examined the spring (pre‐breeding, from March to June) movements of snowy owls by tracking 9 breeding females in the Canadian Arctic for up to 3 yr with satellite transmitters. We used state‐space modeling to assess searching behavior and measure breeding dispersal distances. We also ascertain lemming abundance at some of the sites used by the marked owls. Tracked owls displayed searching movements for extended periods (up to 108 d) and traveled over large distances (up to 4093 km) each spring. The distance between furthest apart searching areas in a given year averaged 828 km (range 220 to 2433 km). Settlement date, distance between searching areas, traveled distance and the duration of prospecting movements were longer in the year where density of lemmings recorded in the eastern High‐Arctic (Bylot Island) was lowest. Nonetheless, snowy owls settled in areas where local lemming abundance was relatively high. Individual breeding dispersal distance between consecutive years averaged 725 km (range 18 to 2224). Overall, the high mobility of female snowy owls allowed these diet specialists to behave as irruptive migrants and to sustain their reproductive activities during consecutive years even under highly fluctuating resources.     

Behaviour controls post-settlement dispersal by the juvenile bivalves Austrovenus stutchburyi and Macomona liliana

Post-settlement dispersal is a key process affecting the population dynamics of many soft sediment benthic invertebrates. Despite its importance, few studies have quantified those factors that influence juvenile dispersal. In a laboratory flume, we examined the effects of three flow velocities and two substrate types on the dispersal of two common intertidal bivalves: the deposit-feeding wedge shell Macomona liliana and the suspension-feeding cockle Austrovenus stutchburyi. Juveniles of three size classes (<2, 2-4 and 4-8 mm shell length) were added to cores of defaunated natural sediment or glass beads. We recorded the number of bivalves remaining in cores versus those recovered downstream either on the flume floor, in bedload traps or in a plankton net at the end of the working section of the flume after 48 h at three freestream velocities (4.8, 11.0 and 16.6 cm s⁻¹). At flow speeds of 4.8 cm s⁻¹, <5% of individuals were recovered outside the cores for both species. At higher flows, the dispersal mode (crawling, bedload or in suspension) and frequency of dispersal differed markedly between species. Austrovenus dispersed primarily by crawling in the low flow treatments. The frequency of dispersal increased substantially (2-6×) between 11.0 and 16.6 cm s⁻¹, and most Austrovenus were found in bedload traps at the highest flow. At the highest flow, twice as many Austrovenus individuals left the glass bead treatment as from the natural sediment. The number of dispersing Macomona also increased with increasing flow from the natural sediment, but numbers dispersing from glass beads were similar for the two higher flows (11.0 and 16.6 cm s⁻¹). Macomona dispersal mode was associated with size; smaller size classes were collected in the bedload traps and the plankton net in approximately equal proportions, while only a small proportion of the largest size class were collected in the plankton net. In contrast to flume dispersal experiments with live bivalves, most dead Austrovenus did not move at the highest flow speed, while most dead Macomona were transported at the highest flow speed. The live-dead comparisons, in conjunction with our primary experimental results, imply that there are active behavioural components to both water column and bedload transport. Our research emphasises that both species actively influence post-settlement transport in response to both substrate type and flow regime, and that bedload transport, often categorised as a passive transport process, is also greatly influenced by active behavioural processes.