Yossi Leshem

DIFFERENTIAL USE OF THERMAL CONVECTION BY SOARING BIRDS OVER CENTRAL ISRAEL

Abstract Maximum altitudes of soaring migration for White Pelicans (Pelecanus onocrotalus), White Storks (Ciconia ciconia), Lesser Spotted Eagles (Aquila pomarina), and Honey Buzzards (Pernis apivorus) were measured in central west Israel and compared to the upper boundary of thermal convection and thermal intensity as predicted by the convection model ALPTHERM. The model predictions of upper boundary of convection explained at least 20% of the variance in maximum altitudes of migration for each species studied. Each species used thermal convection differently. White Pelicans, with the largest wing loading, used 54% of the thermal boundary layer, as calculated by dividing the maximum flight altitude by the modeled thermal depth. White Storks and Lesser Spotted Eagles used 69% and 65%, respectively; Honey Buzzards, with the lowest wing loading, used 95% of the thermal boundary layer. Mean lift rate of convection had a stronger effect on maximum altitudes of flight or the proportion of the thermal boundary layer used by Lesser Spotted Eagles and Honey Buzzards, than it did on storks and pelicans. Honey Buzzards, which combine flapping with soaring flight, were not confined to the thermal boundary layer. Changes in migration altitudes within a species and differential use of thermal convection between species were related to a combination of upper boundary of thermal convection, average lift rate, migratory behavior, wing loading, topography, and additional local meteorological conditions. Uso Diferencial de la Convección Térmica por Aves que Realizan Vuelos Planeados Elevados Sobre Israel Central Resumen. Se midieron las alturas máximas de planeo elevado durante la migración al oeste de Israel central para Pelecanus onocrotalus, Ciconia ciconia, Aquila pomarina y Pernis apivorus, y se compararon con el límite superior de la convección y la intensidad térmica predicho por el modelo de convección ALPTHERM. Las predicciones del límite superior de convección del modelo explicaron al menos el 20% de la varianza en alturas máximas de migración para cada especie estudiada. Cada especie utilizó la convección térmica de una forma diferente. Pelecanus onocrotalus, la especie con la mayor carga alar, utilizó el 54% de la capa térmica límite, lo que se calculó dividiendo la altura máxima de vuelo por la profundidad térmica modelada. Ciconia ciconia y A. pomarina usaron el 69% y 65% de la capa térmica límite, respectivamente; P. apivorus, la especie con menor carga alar, utilizó el 95%. La tasa promedio de fuerza ascensional de convección tuvo un efecto más marcado en las alturas máximas de vuelo o la proporción de la capa térmica utilizada en A. pomarina y P. apivorus que en P. onocrotalus y C. ciconia. Pernis apivorus, que combina el aleteo con el vuelo planeado, no estuvo confinada a la capa térmica límite. Los cambios en las alturas de migración dentro de una especie y el uso diferencial de la convección térmica entre especies estuvieron relacionados con una combinación del límite superior de la convección térmica, la tasa promedio de fuerza ascensional, el comportamiento migratorio, la carga alar, la topografía y condiciones meteorológicas locales adicionales.

Der Zug des Weißstorchs (Ciconia ciconia): eine besondere Zugform auf Grund neuer Ergebnisse

To formulate a comprehensive plan for the conservation of the White Stork (Ciconia ciconia) in conformity with the “Bonn Convention”, along the eastern migration route from the breeding grounds across Israel into the staging areas in northeastern Africa, it was essential to investigate the entire process of migration, including resting behaviour as well as the energetic and ecological aspects. Our approach employed satellite tracking (of 75 individuals), observations of storks in aviaries by methods including magnetic resonance imaging (MRI) and spectroscopy (MRS) (12 birds over 15 months), and extensive field studies. The main result of the investigation is that the White Stork exhibits, at least on the eastern route, a particular mode of migration not previously described in this form for any bird species, with the following characteristics: (i) very rapid travel from the breeding region into the North African staging areas, normally with flight periods every day, lasting about 8–10 hours and separated by 14–16 hours of rest. The ca. 4600-km distance to latitude 18°N is covered in an average of 18–19 days by both young and adult storks. (ii) Rest periods of a whole day or even several days are the exception, and their occurrence seems to be prompted by external circumstances rather than prescribed in the endogenous migration program. (iii) Body mass and fat deposition are low during the outward (and the homeward) journey and peak in midwinter, which is interpreted as an adaptation to unpredictable conditions in the winter quarters. (iv) There is no discernible hyperphagia during migration; instead, on the outward journey the storks evidently feed mainly to meet their immediate needs when in eastern Europe, more opportunistically when approaching the Mediterranean Sea, and practically not at all in Israel. According to this observation and the comparison of body weights in Sachsen-Anhalt and Israel, it is likely that storks lose weight on the outward trip and do not regain it until they reach Africa. We call the migration mode of the White Stork, which travels predominantly in gliding flight, the MSOM type (from “mostly travelling every day”, “seldom inserting whole-day rests”, “opportunistically feeding” and “moderate or no fat depots developing”), and distinguish it from the types ILHB (for intermittently migrating) and NNHB (migrating non stop) (see Discussion). The results of this study, in particular regarding fat deposition and state of breast musculature, are based substantially on MRI and MRS; these methods, tested here in a pioneering long-term study of a bird species living in the wild, have proved extremely useful and show great promise (see following paper). Für ein umfassendes Schutzkonzept für den Weißstorch (Ciconia ciconia) im Rahmen der „Bonner Konvention“ entlang der Ostroute von den Brutgebieten über Israel bis in nordostafrikanische Zwischenziele war es erforderlich, den genauen Zugablauf, das Rastverhalten sowie Fragen der Zugenergetik und Zugökologie zu untersuchen. Wir bearbeiteten die Fragen mit Hilfe der Satelliten-Telemetrie (75 Individuen), der Untersuchung von Störchen in Volieren einschließlich der Magnet-Resonanz-(MR-)Tomographie und -Spektroskopie (MRS) (12 Vögel, über 15 Monate) sowie umfangreicher Freilandstudien. Das Hauptergebnis der Untersuchungen ist: Der Weißstorch zeigt — zumindest auf der Ostroute — einen eigenartigen, bisher von keiner anderen Vogelart in dieser Form beschriebenen Zugmodus mit folgenden Charakteristika: 1) sehr zügiges, normalerweise tagtägliches Wandern vom Brutgebiet bis in die nordafrikanischen Zwischenziele, wobei täglich etwa 8–10 Stunden gewandert und 14–16 Stunden gerastet wird. Die rund 4 600 km bis zum 18. Breitengrad werden von Jung- wie Altstörchen im Mittel in 18–19 Tagen bewältigt. 2) Ganz- oder gar mehrtägige Rast wird nur ausnahmsweise eingeschoben und scheint eher durch äußere Umstände erzwungen als im endogenen Zugprogramm vorgegeben zu sein. 3) Körpermasse und Fettdeposition sind während des Wegzugs (und des Heimzugs) niedrig und erreichen Gipfelwerte im Mittwinter, die als Anpassung an unvorhersagbare Bedingungen im Winterquartier gedeutet werden. 4) Zugzeitliche Hyperphagie ist nicht erkennbar, vielmehr nehmen Störche während des Wegzugs Nahrung in Osteuropa wohl v. a. zur Deckung des Unterhaltsbedarfs auf, zum Mittelmeer hin mehr opportunistisch und in Israel so gut wie gar nicht. Dadurch und aus dem Vergleich von Körpermassen in Sachsen-Anhalt und Israel wird wahrscheinlich, dass Störche auf dem Wegzug an Masse verlieren, die dann erst in Afrika wieder aufgefüllt wird. Wir bezeichnen den Zugmodus des überwiegend im Gleitflug wandernden Weißstorchs als MSOM-Typ (von „Meist täglich wandernd“, „Selten ganze Rasttage einlegend“, „Opportunistisch Nahrung aufnehmend“ und „Maximal Mittelmäßige Fettdepots bildend“) und stellen ihm die Typen ILHB (für intermittierend ziehend) sowie NNHB (nonstop wandernd) gegenüber (s. Diskussion). Die Ergebnisse dieser Arbeit, v. a. über Fettdeposition und Brustmuskelzustand, beruhen ganz wesentlich auf der MR-Tomographie und MR-Spektroskopie, die hier in einer Lang-zeit-Pilotstudie an einer wild lebenden Vogelart zum Einsatz kam und sich als sehr nützlich und vielversprechend erwies (s. die nachfolgende Arbeit).

Does nest box location and orientation affect occupation rate and breeding success of Barn Owls Tyto alba in a semi-arid environment?

Abstract. To date, nest orientation and location in hole-nesting birds have been studied mainly in temperate regions and in diurnal cavity breeders. Here we studied the effect of exposure, orientation, and habitat on nest box occupation and breeding success of Barn Owls in a semi-arid environment. The occupation of nest boxes varied with exposure and orientation. A higher percentage of occupation and more Barn Owl nestlings per breeding attempt were found in nest boxes located in the shade than in the sun, and in those facing east/north rather than other directions. The temperature in the nest boxes varied, being lowest in those located in the shade and in those facing east. Nest boxes located in crop fields fledged more young per breeding attempt than those located in date plantations. We suggest that the higher nest box occupation and number of nestlings fledged was probably due to the lower temperatures in those boxes, an important factor in a hot/arid environment, although alternative explanations are also considered.

Diets of Urban Breeding Barn Owls (Tyto alba) in Tel Aviv, Israel

Abstract Examination of 193 whole pellets and a number of partial pellets of a pair of Barn Owls (Tyto alba) in Neve Shiret, a neighborhood of Tel Aviv, Israel during the 2005 and 2006 breeding seasons revealed a total of 711 prey specimens. Six species of small mammals comprised 99.3% of the diet with a frequency of occurrence of 100% in pellets. Levant voles (Microtus socialis guentheri) (48.1%) and house mice (Mus musculus) (32.9%) were the most common prey species. The Barn Owl pair hunted in croplands adjacent to an urban residential area.

Diets of Barn Owls Differ in the Same Agricultural Region

Abstract We studied the diet of 20 Barn Owl (Tyto alba) pairs breeding in three habitats (alfalfa fields, date plantations, and villages) in the same agricultural region in the Jordan Valley, Israel. Small mammals, particularly three rodents (Levant voles [Microtus socialis guentheri], house mouse [Mus sp.], and Tristrams jird [Meriones tristrami tristrami]), comprised 73 to 88% of the 3,544 prey items taken by Barn Owls in the three habitats. Frequencies in number and biomass of the rodent species differed among habitats. The number of bird species, their frequencies, and biomass in the diet were higher in villages than in the other two habitats, and were related to the higher diversity of birds breeding in villages. The frequency of birds in the diet was negatively correlated with distance from the village to open fields. Differences in the diet of Barn Owls among the three habitats most likely reflected differences in the distribution and abundance of the prey items in each habitat.

USING A CONVECTION MODEL TO PREDICT ALTITUDES OF WHITE STORK MIGRATION OVER CENTRAL ISRAEL Research Note

Soaring migrants such as storks, pelicans and large birds of prey rely on thermal convection during migration. The convection model ALPTHERM was designed to predict the onset, strength, duration and depth of thermal convection for varying topographies for glider pilots, based on atmospheric conditions at midnight. We tested ALPTHERM predictions as configured for two topographies of central Israel, the Coastal Plains and the Judean and Samarian Mountains in order to predict altitudes of migrating white storks (Ciconia ciconia). Migrating flocks of white storks were tracked with a motorized glider, to measure maximum altitudes of migration during spring 2000. A significant positive correlation was found between the maximum daily altitudes of migration measured and the predicted upper boundary of thermal convection for the Coastal Plains and Samarian Mountains. Thirty-minute predictions for the Coastal Plains and Samarian Mountains correlated positively with measured maximum migration altitudes per thermal. ALPTHERM forecasts can be used to alter flight altitudes in both civil and especially military aviation and reduce the hazard of serious aircraft collisions with soaring migrants.

BREEDING SUCCESS OF THE EURASIAN KESTREL (FALCO TINNUNCULUS) NESTING ON BUILDINGS IN ISRAEL

EXITO REPRODUCTIVO DE FALCO TINNUNCULUS AL NIDIFICAR EN EDIFICIOS EN ISRAEL Medimos el exito reproductivo de individuos de la especie Falco tinnunculus que nidificaron en edificios en tres localidades: ciudades grandes, ciudades pequenas y pueblos pequenos. Debido a que estos halcones cazan principalmente en campos abiertos y alimentan a sus polluelos principalmente con pequenos mamiferos, el exito reproductivo de las parejas que nidifican en las ciudades puede ser reducido ya que la abundancia de presas es menor en areas urbanas. Encontramos que tanto el numero de volantones por pareja como el porcentaje de parejas que fueron exitosas produciendo por lo menos un volanton, fueron menores en las ciudades que en los pueblos. Los nidos en edificios en los tres tipos de localidades pueden proveer mayor proteccion ante depredadores incluso en areas rurales, debido a que la mayoria de los depredadores evita los edificios habitados por humanos. Nuestro hallazgo de que el exito reproductivo de halcones que se rep...

THE EFFECT OF DIFFERENT NEST TYPES ON THE BREEDING SUCCESS OF EURASIAN KESTRELS (FALCO TINNUNCULUS) IN A RURAL ECOSYSTEM

EL EFECTO DE DIFERENTES TIPOS DE NIDO SOBRE EL EXITO REPRODUCTIVO DE FALCO TINNUNCULUS EN UN ECOSISTEMA RURAL Estudiamos la tasa reproductiva de Falco tinnunculus en diferentes tipos de nido artificiales y naturales en una region rural de Israel. Los nidos se clasificaron en tres tipos: (1) nidos grandes artificiales de tipo cerrado (i.e., cajas de nidificacion), (2) nidos pequenos artificiales de tipo cerrado (i.e., cajas de nidificacion) o (3) nidos naturales de tipo abierto (i.e., nidos en palmas datileras Phoenix dactylifera). El exito reproductivo fue menor en las cajas de nidificacion grandes: el porcentaje de los nidos en que los huevos eclosionaron fue el mas bajo, al igual que el tamano de la parvada, el numero de pichones que abandonaron el nido por puesta de la pareja y el porcentaje de productividad de los huevos. Un numero significativamente menor de parejas fueron exitosas en las cajas de nidificacion grandes en producir al menos un volanton que en los otros dos tipos de nido. Esto posibleme...

The importance of micro-habitat in the breeding of Barn Owls Tyto alba

Capsule Habitat parameters associated with 706 Barn Owl (Tyto alba) nesting boxes in Israel were analysed. Pairs bred in 259 of the boxes. The intensity of agricultural practices at nestbox sites were shown to have only a weak effect on aspects of Barn Owl breeding in this region.

Feeding specialization of urban Long-eared Owls, Asio otus (Linnaeus, 1758), in Jerusalem, Israel

Abstract The diet of Long-eared Owls (Asio otus) that breed and hunt within the grounds of a bird-ringing station located in a large city park in Jerusalem, Israel, was investigated. 13 species of bird were the most common prey group (91% by number) with a frequency of occurrence of 99% in pellets, with House Sparrows, Passer domesticus, and Blackcaps, Sylvia atricapilla, as the most frequent prey species (22% and 17% by number). 29% of the bird specimens found in pellets had been ringed at the ringing station. The frequency of residential and migratory passerines caught by Long-eared Owls and ringed at the ringing station was similar, whereas more migrants were captured and ringed during the spring than summer. A comparison of bird species that were hunted relative to their frequency in the habitat revealed that the owls caught more Sylvia warblers than expected. Long-eared Owls in this study most probably specialised on birds because of the abundance of passerines and the lack of small mammals.