Food and feeding ecology of Gull-billed terns (Gelochelidon nilotica) in Greece

Le régime de la Sterne hansel Gelochelidon nilotica a été étudié par analyse des pelotes de régurgitation dans trois zones humides de Grèce, le delta de l'Evros (1985-87), Alyki Kitrous (1989) et Messolonghi (1989). Dans la première localité, les insectes, et en particulier les Coléoptères, constituent les proies principales, les autres taxons (Mollusques bivalves, Crustacés, Poissons téléostéens, Reptiles, Mammifères) n'ayant qu'une importance secondaire. A Alyki, ce sont les Orthoptères qui prédominent. A Messolonghi, les crabes arrivent en tête, suivis par les insectes (Orthoptères et Coléoptères principalement), puis les proies de moindre importance (Arachnides, Amphibiens, Poissons téléostéens). Les indices de diversité trophique varient d'une année à l'autre dans le delta de l'Evros. Contrairement à ce qui a été suggéré antérieurement, la diversité du régime de la Sterne hansel est indépendante de la latitud

Comparación de los patrones de selección del lugar de nidificación de distintas especies rapaces simpátridas, como herramienta para su conservación

In this study the nest–site selection patterns of four tree–nesting sympatric raptor species in Dadia National Park (Greece) were compared in order to provide a sound conservation tool for their long–term management in the area. The species studied were the Black vulture (Aegypius monachus), the Lesser–spotted eagle (Aquila pomarina), the Booted eagle (Hieraaetus pennatus) and the Goshawk (Accipiter gentilis). Twenty–six variables illustrating the landscape context and vegetation structure of nesting sites were analysed. Multivariate–ANOVA and Discriminant Function Analysis were used to test for significant differentiations in nest–site characteristics among the species. The species studied were initially differentiated by geomorphology and distance to foraging areas. Once these were determined their nesting areas were established according to forest structure. Our results indicate that forest management should integrate the preservation of mature forest stands with sparse canopy and forest heterogeneity in order to conserve suitable nesting habitats for the raptors. Specific conservation me asures such as restriction of road construction should be implemented in order to protect the active nests and provisions should be made for adequate nesting sites for the Black vulture, which is sensitive to human disturbance. Key words: Sympatric raptors, Discriminant analysis, Nesting habitat separation, Conservation guidelines.En este estudio se han comparado los patrones de selección del lugar de nidificación de cuatro especies de rapaces simpátridas que construyen sus nidos en los árboles, en el Dadia National Park (Grecia), con el fin de obtener una buena herramienta de conservación para su gestión a largo plazo en esta zona. Las especies estudiadas fueron el Buitre Negro (Aegypius monachus), el Águila Pomerana (Aquila pomarina), el Aguililla Calzada (Hieraaetus pennatus) y el Azor Común (Accipiter gentilis). Se analizaron 26 variables que ilustraban el contexto paisajístico y la estructura de la vegetación de los lugares de nidificación. Se utilizaron el ANOVA multivariante y el Análisis de Función Discriminante para comprobar las diferencias significativas en las características de los lugares de nidificación según las especies. En primer lugar, las especies estudiadas se diferenciaron en cuanto a la geomorfología y la distancia a los lugares de alimentación. Una vez determinados ambos parámetros, se establecieron sus áreas de nidificación según la estructura forestal. Nuestros resultados indican que la gestión forestal debería integrar la conservación de zonas de bosque maduro con un dosel escaso y la heterogeneidad forestal, para conservar hábitats de nidificación adecuados para estas rapaces. Deberían tomarse medidas específicas de conservación tales como la restricción de construcción de carreteras, para la protección de los nidos activos y se debería proveer de lugares adecuados para la nidificación del buitre negro, que es muy sensible a la presencia humana. Palabras clave: Rapaces simpátridas, Análisis discriminante, Clasificación de hábitats de nidificación, Pautas de conservación

Breeding ecology of the avocet (Recurvirostra avosetta L.) in the Evros delta (Greece)

Volume: 36Start Page: 37End Page: 5

Winter diet of the Barn Owl (Tyto alba) and Long-eared Owl (Asio otus) in northeastern Greece: A comparison

Volume: 33Start Page: 160End Page: 16

Comparison of nest-site selection patterns of different sympatric raptor species as a tool for their conservation

In this study the nest-site selection patterns of four tree-nesting sympatric raptor species in Dadia National Park (Greece) were compared in order to provide a sound conservation tool for their long-term management in the area. The species studied were the Black vulture (Aegypius monachus), the Lesser-spotted eagle (Aquila pomarina), the Booted eagle (Hieraaetus pennatus) and the Goshawk (Accipiter gentilis). Twenty-six variables illustrating the landscape context and vegetation structure of nesting sites were analysed. Multivariate-ANOVA and Discriminant Function Analysis were used to test for significant differentiations in nest-site characteristics among the species. The species studied were initially differentiated by geomorphology and distance to foraging areas. Once these were determined their nesting areas were established according to forest structure. Our results indicate that forest management should integrate the preservation of mature forest stands with sparse canopy and forest heterogeneity in order to conserve suitable nesting habitats for the raptors. Specific conservation measures such as restriction of road construction should be implemented in order to protect the active nests and provisions should be made for adequate nesting sites for the Black vulture, which is sensitive to human disturbance

Mercury in feathers of Squacco Heron (<i>Ardeola ralloides</i>) chicks in relation to age, hatching order, growth, and sampling dates

We studied the relationships between mercury content of Squacco Heron (Ardeola ralloides) chick body-feathers and nestling age, hatching order (seniors-juniors) and growth parameters, and the date of feather sampling in the Aries Delta, northern Greece, in 1993 (n = 75 chicks) and 1994 (n = 80). Mercury levels were not significantly correlated with chick age in either year of the study. Most of the variability in mercury (90%) was found among broods, attributable to differential prey selection and/or foraging habitat and patch utilization by parents. Within broods, juniors had significantly higher mercury loads than seniors in 1993, but there was no significant difference between the two in 1994. Correlations of nestling weight and linear measurements corrected for chick age and mercury concentrations were never significant and explained small amounts of variability in chick growth. However, linear measurements corrected for age were significantly higher among seniors in 1993, when those nestlings had lower mercury loads than their siblings. Mercury levels were unaffected by the date of feather collection in 1993, but exhibited a significant increase over time in 1994. This can be attributed to a shift towards more highly contaminated habitats and prey types by foraging parents, resulting from seasonal changes in water level and vegetation cover in important foraging habitats. Feather collection from Squacco Heron nestlings late in the breeding season seems to be an appropriate method for biomonitoring mercury pollution in the Aries Delta. (C) 2000 Elsevier Science Ltd. All rights reserve

Patterns of postnatal growth in a small falcon, the lesser kestrel Falco naumanni (Fleischer, 1818) (Aves: Falconidae)

Following a dramatic decline, the lesser kestrel Falco naumanni global population has recently stabilised, although it is still fluctuating in several countries, including Greece. Nestling growth rates and size at fledging greatly influence future survival and reproductive success, and therefore the study of postnatal growth can aid the understanding of population dynamics and the conservation of avian populations. We quantified body mass and morphological traits in female and male lesser kestrel nestlings from a lowland Greek breeding population. Nonlinear mixed models were used to describe and compare growth trajectories. Growth in body mass, tarsus and bill reached asymptotic values before fledging and was best described by the logistic equation, whereas total length grew linearly beyond the fledging phase. Random variation was found in the asymptote in body mass, the inflection point in body mass, tarsus and bill lengths and the intercept in total length, being substantially higher between nests than amongst siblings, implying differences in parental quality between nests and also an even distribution of parental care amongst siblings. Random effects were not observed on the growth rate constant, supporting the hypothesis that it varies little within populations. Females were significantly heavier and had longer bills and total length than males, whereas males were similar to females in tarsus growth. Nonlinear mixed models allowed us to describe a stage of avian life vital for future survival and reproductive output and reveal variation between nests, nestlings and the sexes