Dimitri Giunchi

Orientation of the pied flycatcher Ficedula hypoleuca: cue-conflict experiments during spring migration

Hierarchical relationships among different compass systems in long-distance migrants are still a matter for discussion because different studies have led to highly variable and apparently contradictory results. We carried out cue-conflict experiments during spring migration on pied flycatchers Ficedula hypoleuca (Passeriformes, Muscicapidae). Birds were exposed to a conflict between celestial and magnetic information by altering the polarized light pattern or magnetic field. The polarization pattern was shifted (±90°) with filters, whereas the magnetic field was altered (+90°) through Helmholtz coils. Birds were tested in modified Emlen funnels both before and after the cue conflict; during the tests, only the natural magnetic field was available. This protocol was designed to test whether the experimental birds recalibrated their magnetic compass on the directional information derived from the light polarization pattern when the region near the horizon was visible during the conflict. Contrary to this expectation, we did not record any significant shift in magnetic orientation after one or repeated exposures to the cue conflict. Our results support earlier studies, which suggest that the magnetic field is the primary compass cue during the migratory period.

On the use of pharmacological sterilisation to control feral pigeon populations.

The use of chemosterilisation for controlling feral pigeon populations was investigated by: (1) quantifying the reproductive activity of pigeons in two Italian cities; (2) testing the efficacy of nicarbazin, an anticoccidial drug with rapid and reversible effects on the reproduction of laying hens, on groups of paired pigeons maintained in open aviaries; and (3) simulating the effects of the use of nicarbazin on a hypothetical population, allowing for the reproductive productivity recorded in (1) and the efficacy of this drug as obtained in (2). Breeding attempts were recorded all year round in both study sites with a minimum peak in September-October, a maximum in March-July, but with active nests in winter too. In terms of the sterility activity of the drug, the results showed only a partial inhibition of reproduction of pigeons fed ∼38-82 mg nicarbazin day −1 (kg bodyweight) −1 (500 and 800 ppm in feed), which, according to the simulations, would produce only a fleeting reduction of their abundance in the field. Data do not seem to support the use of this drug as an effective control method for feral pigeons, and they cast doubts on the opportunity to make use of chemosterilants, which produce only partial and reversible effects. The use of this drug could perhaps be considered only as part of an integrated pest-management program, which necessarily has to include the reduction of carrying capacity of the urban environment.

Foraging flights of wild rock doves (Columba l. livia): a spatio‐temporal analysis

Abstract The first spatio‐temporal analysis of foraging flights of wild rock doves is here reported. Birds living in one of the last relatively pure demes of wild Columba livia in the Mediterranean region (Capo Caccia, NW Sardinia) were observed on their foraging routes and in the course of daily movements to and from the colonial site. Foraging sites were located by systematic searches of colour‐marked birds in the study area. The pigeons followed rather stable routes in reaching foraging sites, which are mainly located in agricultural fields up to around 19 km from the colonial site. In autumn, doves tended to reduce the extent of foraging flights, feeding almost exclusively on lenti‐scus fruits located near the colony. Foraging flights in spring and summer differed from those in autumn and winter in the patterns of daily activity, the number of birds moving, and the sizes of the flocks. The possible relationships between the spatio‐temporal characteristics of foraging flights and other aspects of the biology of rock doves, especially in the breeding season, are discussed.

A temporal analysis of the foraging flights of feral pigeons (Columba livia f. domestica) from three Italian cities

Foraging flights of feral pigeon populations may differ in occurrence and extent from town to town. In this paper, the annual pattern of such flights from three medium‐sized Italian cities (Venice, Parma and Lucca) is described and compared with that recorded for a Mediterranean population of wild rock doves from Sardinia. The data provide evidence of the similarity of these flights both within urban populations and between feral pigeons and wild rock doves. On the other hand, the presented results point to a noticeable flexibility of this behaviour, whose features seem finely adapted to the environmental features of an urban habitat and its surroundings. In particular, the distribution of food resources and of the annual trend of reproductive attempts appear to exert a leading role in shaping the characteristics of these flights.

A long term study on initial orientation in sand martins (Riparia riparia)

Over a period of 18 years sand martins (Riparia riparia) were displaced from their breeding colonies and released to investigate the relationship between distance of displacement and initial orientation. The results show significant homeward orientation at the shortest distances of displacement (7.1-18.2 km, series A), but not over longer distances (49-180 km, series B and C). Birds displaced over 49 km from their breeding colonies only seldom show homeward directedness, while pseudo-pooling and second order analysis of their directional choices seem to indicate the tendency to fly in a given compass direction. Possible causal factors that can induce this behaviour in sand martins are discussed, taking into account not only local biasing factors but also the existence of a so called preferred compass direction. These data show that sand martins are able to determine the correct homing direction inside a probably familiar area. The response over longer distances indicates difficulties in determining the appropriate homing course at takeoff.

New cue-conflict experiments suggest a leading role of visual cues in the migratory orientation of Pied Flycatchers Ficedula hypoleuca

Migratory birds use both geomagnetic and celestial cues to select and maintain their seasonally appropriate migratory direction. The integration of the different compass cues is still poorly understood. Previous cue-conflict experiments suggested that Pied Flycatchers Ficedula hypoleuca did not recalibrate their magnetic compass against the polarization pattern at twilight, but the available evidence is problematic given the high variability of birds’ directional preferences. We performed a new set of cue-conflict experiments where (1) we modified the protocol in order to try to reduce scatter of data and (2) we integrated the results of two experimental approaches, i.e. orientation cages and releases of radio-tagged birds. Pied Flycatchers were tested in Emlen funnels without access to celestial cues before and after being exposed to conflicting visual and geomagnetic information. After the second test, birds were equipped with radio-transmitters and followed until the vanishing of the radio signal. Contrary to previous experiments, our data showed a general dominance of celestial cues: polarized light sun-related pattern in captive birds tested without access to stars and stellar dominance in free-flying birds released under a starry sky at night-time. These results underline the importance of experimental protocols when testing ways in which birds integrate their compass systems.ZusammenfassungNeue Experimente mit widersprüchlichen Signalgebern deuten auf eine Führungsrolle visueller Signalgeber bei der Zugorientierung von TrauerschnäppernFicedula hypoleucahin Zugvögel nutzen sowohl geomagnetische als auch Himmelssignalgeber, um die der Jahreszeit entsprechende Zugrichtung zu wählen und einzuhalten. Die Integration der verschiedenen Kompasssignalgeber ist nach wie vor kaum verstanden. Vorherige Experimente mit widersprüchlichen Signalgebern deuteten darauf hin, dass Trauerschnäpper Ficedula hypoleuca ihren Magnetkompass nicht anhand des Abenddämmerung-Polarisationsmusters rekalibrieren, doch die vorliegenden Befunde sind in Anbetracht der hohen Variabilität der Richtungspräferenzen von Vögeln problematisch. Wir haben einen neuen Satz von Experimenten mit widersprüchlichen Signalgebern durchgeführt, in dem wir (1) das Protokoll modifiziert haben, in dem Versuch, die Streuung der Daten zu reduzieren, und (2) die Ergebnisse zweier experimenteller Ansätze, Orientierungskäfige und Freilassung von mit Radiosendern versehenen Vögeln, integriert haben. Trauerschnäpper wurden in Emlen-Trichtern ohne Zugang zu Himmelssignalgebern getestet, bevor und nachdem sie widersprüchlicher visueller und geomagnetischer Information ausgesetzt worden waren. Nach dem zweiten Test wurden die Vögel mit Radiosendern versehen und solange verfolgt, bis das Radiosignal verschwand. Im Gegensatz zu vorherigen Experimenten zeigten unsere Daten eine generelle Dominanz von Himmelssignalgebern–das Polarisationsmuster des Tageshimmels bei Vögeln in Gefangenschaft, die keinen Zugang zu den Sternen hatten, und Sterne bei Vögeln, die nachts bei sichtbarem Sternenhimmel freigelassen wurden. Diese Ergebnisse unterstreichen die Bedeutung experimenteller Protokolle, wenn untersucht wird, wie Vögel ihre verschiedenen Kompasssysteme integrieren.

Pattern of Wing Moult and Its Relationship to Breeding in the Eurasian Stone-Curlew Burhinus oedicnemus

The timing, duration and pattern of the poorly documented wing moult in the Eurasian Stone-curlew Burhinus oedicnemus were described and related to the breeding cycle. Between 1998 and 2007, 141 birds were trapped in the Taro River Regional Park (Parma, Italy) both while incubating and during the post-breeding season. The timing of primary moult was estimated according to the method of Underhill & Zucchini (1988) and Underhill et al. (1990). Primary moult was very slow and overlapped most of the breeding season, beginning in early May and ending in October. Secondary moult was much more irregular and was not completed within a single moult cycle. Innermost and outermost secondaries were more likely to be shed than those at the centre of this tract. Juvenile secondaries were not shed during the first winter. The study provides the first detailed analysis of wing moult in the Eurasian Stone-curlew and suggests some useful ageing criteria based on the pattern of secondary moult. The extensive overlap between breeding and moulting is relatively uncommon compared to other waders. This could be interpreted as a way to maximize breeding success through renesting potential (up to 4 attempts), i.e. by spreading the cost of moult over a prolonged time period. A between-species comparison using independent contrasts was consistent with this hypothesis: species with a prolonged breeding season also showed considerable overlap in the timing of primary moult and breeding activities.

The effect of clock-shift on the initial orientation of wild rock doves ( Columba l. livia )

Previous experiments on wild rock doves (Columba l. livia Gmelin) released within their familiar area revealed an evident effect of fast-shifting, although shifted doves, but not controls, tended to orient homeward. Such an outcome suggested a possible influence of the release time per se on the directional choices of the tested doves. In the present study, this hypothesis was investigated by comparing the orientation of slow-shifted birds to that of two control groups released at different times of the day. As would be expected if doves make use of a time-compensated sun compass, the bearings of shifted birds were deflected clockwise with respect to controls. The time of release itself seemed to influence only the scatter of the vanishing bearings of controls. These findings testify to the substantial similarity of clock-shift effects on the initial orientation of rock doves to those on homing pigeons released from familiar sites.

The Vocal Repertoire of the Eurasian Stone-Curlew (Burhinus oedicnemus)

Abstract We collected behavioral observations and recordings of adult Eurasian Stone-curlews (Burhinus oedicnemus) in central and northern Italy, and of chicks in northern Italy. Eurasian Stone-curlews are highly vocal during spring and summer, and vocalize routinely, but less frequently, during fall and winter nights. Adult Eurasian Stone-curlews have a complex and relatively wide vocal repertoire composed of at least 11 different call types and some subtypes. Two of these calls (Kurlee and Gallop) are the most used and important; the Kurlee call is uttered year-round, while Gallop is uttered usually during the breeding season with a peak in spring. Adult vocalizations are structurally diverse; call syllable duration spans from < 0.1 to > 1.1 sec and average center frequency is between 2,190 to 3,037 Hz. The highest frequency is associated with a high intensity alarm call; some adult vocalizations can be compared to the loud rhythmically repeated calls which often occur in several species of Charadrii and Scolopaci. Five call types are used in well-defined circumstances suggesting specialized functions; the remaining calls are used mostly in combination with other call types, particularly Kurlee and Gallop calls. There are preferred and typical call combinations, which cannot be explained as random choices. We identified two main call types for chicks, which are completely different from adult calls and are developed before hatching. Juveniles up to 70 days of age utter these calls without major changes. We discuss preliminary data on vocal ontogenesis, as well as correspondences and differences between our findings and the existing literature on the adult repertoire.

RELEASE EXPERIMENTS WITH WILD ROCK DOVES (COLUMBA L. LIVIA GM.)

The homing behaviour of free-living birds has rarely been systematically investigated, and so it is difficult to give a satisfactory comparative picture. Data are here presented on the initial orientation of rock doves displaced inside and outside the area that they daily cross during their foraging flights. Inside the familiar area, the results show marked variability in the directional choices of the released birds, probably related to temporal variability in the location of food patches during the year. Indeed, in autumn, when the doves feed almost exclusively near the colony site, they tend to fly home, but in summer, when food patches are dispersed over a wide area around the colony, this behaviour is not evident. Outside the familiar area, no clear evidence of a homeward directedness is obtained. Two releases inside the familiar area with clock-shifted birds produced ambiguous results and it is difficult to attribute the behaviour of the animals to a change in their motivation to reach home in different times of the day, or to the use of a time-compensated sun compass. On the whole, the presented results point to the difficulties of comparing rock dove behaviour to that of the homing pigeon, and show the importance of considering the influence of ecological and motivational variables in evaluating the orienting performances of wild birds.