A NEW PAPER ON THE WESTERN MARSH HARRIER MIGRATION

https://bioone.org/journals/acta-ornithologica/volume-58/issue-1/00016454AO2023.58.1.003/Differential-Flight-Strategies-of-Western-Marsh-Harrier-Circus-aeruginosus-in/10.3161/00016454AO2023.58.1.003.short

Differential flight strategies of Western Marsh Harrier Circus aeruginosus in relation to sex and age class during spring migration in the Central Mediterranean

Nicolantonio Agostini, Marco Gustin, Michele Cento, Jost von Hardenberg, Gianpasquale Chiatante

Acta Ornithologica 58: 41-53.

 

Several bird species show differential migration in relation to age and/or sex classes, often associated with morphological and behavioural differences. The Western Marsh Harrier Circus aeruginosus is a partial migrant, showing a strong sexual dimorphism in size. This species migrates on a broad front, undertaking long water crossings through the Mediterranean Sea. In this study we carried out a two-year survey on the pre-breeding migration of this species at three sites located in the Central Mediterranean region: the islands of Ustica and Panarea (Tyrrhenian Sea) and the Strait of Messina (Peloritani Mountains). The aim of this study was to analyse the flight strategies of this broad front migrant in relation to wind patterns, such as in relation to different sex and age classes. Our results revealed differential flight behaviours among harriers belonging to different sex classes, with adult females less attracted to islands than adult males during a sea crossing, and adult males reaching higher altitude early in the season along a mountain chain. It is suggested that adult males, thanks to their smaller size, use to a larger extent soaring flight by exploiting even weak thermals en route. Unlike the Tyrrhenian islands, few immatures were seen passing along the Peloritani Mountains, probably because they fly at lower altitudes over mainland, passing over areas where they can eventually find prey and/or rest at stop-over site en route. In conclusion, our study shows that the location of the observation post can affect the result concerning migration survey of both sex and age classes in this species, leading to evident bias.

 

NUOVO ARTICOLO SULLA MIGRAZIONE DEL FALCO DI PALUDE PUBBLICATO SU ACTA ORNITHOLOGICA

 

Numerose specie di uccelli mostrano migrazioni differenziali in relazione alle classi di età e/o sesso, spesso associate a differenze morfologiche e comportamentali. Il Falco di palude Circus aeruginosus è un migratore parziale, che mostra un forte dimorfismo sessuale nelle dimensioni. Questa specie migra su un ampio fronte, intraprendendo lunghe traversate attraverso il Mar Mediterraneo. In questo studio abbiamo condotto un'indagine sulla migrazione primaverile di questa specie in tre siti situati nella regione del Mediterraneo centrale: le isole di Ustica e Panarea e lo Stretto di Messina (Monti Peloritani). Lo scopo di questo studio era quello di analizzare le strategie di volo di questo migratore su fronte ampio in relazione alle diverse classi di sesso e di età. I nostri risultati hanno rivelato differenti strategie migratorie adottate da individui appartenenti alle diverse classi di sesso, con le femmine adulte meno attratte dalle isole rispetto ai maschi adulti durante la traversata del Mar Tirreno, e i maschi adulti che guadagnano quote più elevate all’inizio della stagione lungo una catena montuosa. Si ipotizza che i maschi adulti, grazie al loro minor peso, utilizzino in misura maggiore il volo veleggiato sfruttando anche le termiche più deboli. Pochi immaturi sono stati visti transitare lungo i Monti Peloritani, probabilmente perché essi tendono a volare a quote più basse sulla terraferma, passando su aree dove possono eventualmente trovare prede e/o riposarsi. In conclusione, il nostro studio mostra che l’ubicazione del posto di osservazione può influenzare il risultato relativo al monitoraggio del passaggio di individui appartenenti a differenti classi di età e sesso in questa specie, portando ad evidenti distorsioni.

NEW PAPERS OUT NOW!

Agostini N., Panuccio M., von Hardenberg J. & Monti F. 2022. Potential importance of wind patterns and guidance opportunities for the conservation of the Egyptian Vulture Neophron percnopterus in Italy. Bird Conservation International 1-10, doi:10.1017/S0959270922000089.

Movement ecology and environmental factors are topics of paramount importance to consider when planning conservation programmes for target species. Here we discuss this topic by reviewing the available information related to the Egyptian Vulture Neophron percnopterus, with reference to the remnant breeding population of Southern Italy, of high conservation concern and subject of a long-term captive-breeding re-stocking programme. We describe how adverse wind conditions over the Central Mediterranean Sea make the sea-crossing challenging with detrimental effects on the survival of inexperienced birds, and coupled this information with count data of migrating Egyptian Vultures. Furthermore, we indicate how low population size and scarce opportunities in meeting migrating conspecifics could potentially lead juvenile Egyptian Vultures to follow unfavourable migratory routes, with possible repercussions on survival. We postulate how these concomitant factors could be indirectly influencing the longterm survival of this small population, principally affected by anthropogenic threats. We also discuss how the same factors could actually be affecting captive-bred young individuals released in late summer in southern continental Italy, in the framework of the restocking programme. An integrative approach with tailor-made release methods, which also takes into account the age of released birds and geographical and environmental factors, would likely be useful for a more goal-oriented and long-lasting conservation outcome, for the preservation of this endangered scavenger.

Chiatante G., Panuccio M., Pastorino A., Dell’Omo G., Scacco M. & Agostini N. 2022. Small-scale migratory behavior of three facultative soaring raptors approaching a water body: a radar study investigating the effect of weather, topography and flock size. Journal of Ethology. DOI:10.1007/s10164-022-00766-x                                   

Water bodies are considered a barrier to the migration of large bird species, mainly because of the absence of thermals that these birds heavily rely on to move large distances with little energy expenditure. In this two-year study, we combined vertical and horizontal radar data with visual observations to compare the autumn migratory behavior of three facultative soaring species: European honey buzzards Pernis apivorus, western marsh harriers Circus aeruginosus and black kites Milvus migrans. Here we used non-parametric tests, linear and generalized linear models to investigate the efect of fock size, age, local weather conditions, time of the day and topography on the small-scale fight behavior of these species, quantifed in terms of fight altitude, fight direction and distance from the mountain ridge. European honey buzzards, both adults and juveniles, were detected over the plateau near the mountain chain during suitable weather conditions for soaring fight (especially high temperature) and during high species fow, which facilitated the location of thermals. In contrast, inexperienced juveniles were less concentrated in space, forming smaller focks and fying at lower altitudes, probably being less facilitated than adult in exploiting the soaring fight. The Western marsh harrier, a raptor largely using the fapping fight even over land, few lower than adult honey buzzards and nearer to the mountain ridge during strong tailwinds, perhaps being efcient in exploiting their support using the fapping fight even during inter-thermal gliding. Such as western marsh harriers, black kites few nearer the mountain chain during strong tailwinds, but they probably use soaring fight during such weather conditions to exploit their onward support even when circling in thermals.