Cue-conflict experiments between magnetic and visual cues in dunlin Calidris alpina and curlew sandpiper Calidris ferruginea

Despite our extensive knowledge on various aspects of their lives, there has been limited investigation into the hierarchical relationships among different compass systems in shorebirds. The aim of this study was to investigate the relationship between magnetic and celestial compasses in two species of shorebirds, the curlew sandpiper (Calidris ferruginea; prebreeding migration) and the dunlin (Calidris alpina; postbreeding migration) using cue-conflict experiments. Birds were captured in a Mediterranean stopover site, after which their magnetic orientation was determined under simulated overcast conditions at sunset using modified Emlen funnels fitted with infrared video cameras. Birds that demonstrated a well-defined directional preference were then exposed over two sunsets to conflicting directional information between the local geomagnetic field and the ±90° shifted band of maximum polarisation. These individuals were tested again for magnetic orientation at sunset in the same conditions as previous test, to determine whether their directional choices had changed after the cue-conflict. Our results showed that individuals from both species did not recalibrate their magnetic compass from visual cues after the cue-conflict, even though at least dunlins did not appear to completely disregard the information derived from celestial cues. This study is one of the few experimental studies on the migratory orientation of Charadriiformes and on the hierarchical relationships between the different compasses used by these birds during their extensive migratory movements

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

On the interplay between phylogeny and environment on behaviour of two urban bird species, <em>Columba livia</em> and <em>Corvus corone</em> (Aves)

International audienceDifferent hypotheses exist to explain the ability of individuals or species to modify their behaviours in response to the urban environment. Our study addresses risk-taking in urban birds as an essential behavioural change in cities allowing the species to manage living in anthropic habitats. Specifically, we tested role of phylogeny and the environment on risk-taking, expressed in lower escape distances. We adopted a comparative approach and compared the flight distance of urban pigeons and urban crows in Paris with rural wild rock doves and crows in Sardinia, thus contrasting environmental conditions (urban or rural), species (columbids vs. corvids) and type (feral or wild). Pigeons had lower flight distance than crows in both rural and urban environments, and rural individuals of both species had higher flight distance than urban individuals. However, this intraspecific difference was higher in pigeons than in crows, and the interspecific difference was higher in urban than in rural areas. Our study shows that risk-taking in birds is the outcome of a complex interplay between several environmental and phylogenetic factors, and confirms the hypothesis of increased risk-taking in urban pigeons as a result of a pre-adaptation due to artificial selection, as often suggested but never scientifically demonstrated

Caratterizzazione genetica di esemplari domestici e urbani di colombo (Columba livia)

Obbiettivo principale della ricerca è stato quello di descrivere la variabilità genetica esistente in sei razze domestiche di colombo (Columba livia) e in alcune popolazioni urbane italiane. Sono stati raccolti 189 campioni di penne da colombi appartenenti a sei razze domestiche, quattro autoctone italiane (Reggianino, Sottobanca, Triganino Modenese e Viaggiatore Italiano da Esposizione) e due di origine straniera (Colombo Viaggiatore e Pavoncello), ma allevate in Italia da molto tempo, nonché da ulteriori 78 individui provenienti da quattro città dell’Italia centro-settentrionale. Tra quelle autoctone, il Triganino Modenese e il Reggianino hanno origini antichissime ed entrambe sono suddivise in due sottorazze. Il DNA estratto dai campioni è stato analizzato con un pannello di 14 loci microsatellite e i risultati sono stati analizzati con metodi di statistica classica e bayesiana. I risultati preliminari presentano una chiara distinzione fra le diverse razze domestiche, evidenziando una maggiore distanza genetica fra quelle che storicamente hanno avuto origine in aree differenti. I dati ottenuti dalle analisi di Triganino Modenese e Reggianino inoltre mostrano distanze genetiche compatibili con il frequente scambio di riproduttori tra le sottorazze. Gli individui provenienti dai contesti urbani analizzati mostrano generalmente una composizione genetica molto simile a quella di alcune razze domestiche, anche se sono ben evidenti differenze riconducibili ai singoli processi di formazione delle diverse popolazioni urbane, oltre al modesto interscambio esistente tra di esse. I dati sulle razze domestiche confermano quelli storici relativi ai processi di selezione a partire da razze molto antiche o da individui selvatici. Ulteriori informazioni per chiarire i processi di addomesticamento e l’origine di alcune popolazioni cittadine potrebbero derivare dallo studio di popolazioni selvatiche di Columba livia. A tal proposito prevediamo di ampliare il campionamento con esemplari appartenenti a colonie selvatiche in Sardegna e Tunisia, di incrementare lo studio dei colombi domestici con l’analisi di nuove razze e di ampliare il numero di contesti urbani campionati. Dati recenti relativi allo studio del genoma di colombo permetteranno l’integrazione dello studio dei geni neutrali con l’analisi di geni funzionali negli esemplari domestici, urbani e selvatici

Feral pigeon populations: their gene pool and links with local domestic breeds

Columba livia is a wild bird whose domestication has led&nbsp;to a large number of pigeon breeds. The occasional loss or straying&nbsp;of domestic birds determined the origin of feral pigeons, which are now widespread all around the world. In this study, we assumed that the main contribution to feral populations is provided by domestic breeds reared in the same areas. We tested this hypothesis by analysing the variability of 12 microsatellite loci in nine Italian feral populations sampled in areas with different intensities of breeding and selecting domestic breeds. We included in the analysis samples belonging to ten domestic lineages commonly bred in Italy. The pattern of geographic differentiation of feral populations turned out to be rather complex and only partially explained by the geographic distance between populations. This pattern can be understood only when the domestic breeds were included in the analysis. In particular, feral populations located in regions with a long-lasting tradition of pigeon breeding showed a high level of admixture with domestic breeds, in particular with Racing Homer and Piacentino. Ferals from Bolzano, Venice and Sassari were characterized by unique genetic components, mostly&nbsp;not shared by other feral populations and by the considered domestic breeds. Our results further emphasize the complex genetic structure of feral populations whose origin can be properly investigated by taking into account&nbsp;the pool of domestic pigeons bred in the considered area

Pattern of non-breeding movements by Stone-curlews Burhinus oedicnemus breeding in Northern Italy

The identification of year-round geographical ranges and the quantification of the degree of migratory connectivity are fundamental to the successful conservation of migratory bird populations. The Stone-curlew Burhinus oedicnemus is a species of conservation concern in Europe, but its ecology and behaviour are relatively poorly investigated. In particular, its migratory behaviour and the locations of the wintering ranges of most European populations are not known in detail because of a lack of specific studies and the scarcity of ringing recoveries. This study aimed to identify the wintering areas of a Stone-curlew population breeding in the Taro River Regional Park (Parma, northern Italy) by integrating the information obtained from ringing recoveries (n = 2), geolocators (n = 7), and GPS data loggers (n = 2). Furthermore, we compared two approaches to inferring the location of an assumed stationary bird using geolocator data. The different sources were quite coherent, indicating that tagged Stone-curlews did not leave the Mediterranean basin throughout the year and passed the winter in Sardinia or in Tunisia. The recorded wintering sites coincided with areas where breeding (and possibly resident) populations are reported, further emphasising the importance of these areas for the conservation of the species throughout the annual cycle. To our knowledge, our study represents the first thorough analysis performed to uncover the movements of a Mediterranean population of Stone-curlews. Furthermore, it proves the great potential of the tracking devices used in this work to provide information on the migration and non-breeding sites of elusive species, for which the application of mark–recapture/re-sighting techniques is hindered by profound limitations