Agri-environment schemes usually assume that suitable management in patches of grassland habitat may benefit bird populations in improving the overall demographic balance. In this study, we investigate the hypothesis that nesting site fidelity after previous breeding success might lead meadow birds to select late mown fields where the risk of breeding failure is lower. It was carried out in 4 study areas of the Mézenc volcanic massif (south-east of France) within the altitude range 1,150-1,350 m. Meadow passerine territories were defined by the territory mapping method, and reproductive success in Whinchat Saxicola rubetra territories was assessed by the observation of prey carrying and juveniles just leaving nests. A comparison of models led us to consider that territorial birds selected hay fields under the influence of grass structure rather than through a theoretical successful experience of late mowing. Higher territory density was observed in fields with dense grass cover C50 cm which were usually more fertilized ([75 kg ha -1 nitrogen per year) and mown earlier. In 3 study sites, however, the rate of nesting failure due to mowing was lower than expected under the hypothesis of randomly distributed nesting sites, suggesting that the risk was not ignored by territorial birds. Within each study site, we also observed higher invertebrate abundance during the chick feeding period in fields with high bird territory density. ZusammenfassungWählen Singvögel des Offenlandes aufgrund von erhöhtem Bruterfolg spät gemähte Felder? Agrar-Umweltprogramme gehen normalerweise von der Annahme aus, dass Vogelpopulationen von geeigneten Managementmaßnahmen auf fleckenarteigen Teilflächen des Graslands profitieren könnten, weil durch sie die demographische Bilanz insgesamt verbessert würde. In der vorliegenden Studie bearbeiten wir die Hypothese, dass Nestortstreue nach vorherigem Bruterfolg Wiesenbrüter dazu führt, spät gemähte Felder auszuwählen, auf denen das Brutverlust-Risiko geringer ist. Die Studie wurde auf vier Teilflächen des Mézenc Vulkanmassivs (Südost-Frankreich) in Höhenlagen von 1,150-1,350 m durchgeführt. Die Brutreviere von wiesenbrütenden Singvögeln wurden mit Hilfe einer Revierkartierungsmethode erfasst, und der Reproduktionserfolg in Revieren des Braunkehlchens Saxicola rubetra durch Beobachtung Futter tragender Altvögel und gerade flügger Jungvögel bestimmt. Ein Vergleich von Modellen führte uns zu dem Schluss, dass territoriale Vögel Wiesen für die Heuernte eher unter dem Einfluss der Vegetationsstruktur auswähl-ten, als unter dem Aspekt einer theoretisch erfolgreichen Bruterfahrung durch späte Mahd. Eine höhere Revierdichte konnte vor allem in Feldern mit dichter Grasbedeckung C50 cm beobachtet werden, die normalerweise besser gedüngt waren ([75 kg ha -1 Stickstoff pro Jahr) und früher gemäht wurden. In drei Untersuchungsflächen war die Brutverlustrate durch Mähen allerdings niedriger, als Communicated by F. Bairlein.
Assessing population trends and their underlying factors is critical to propose efficient conservation actions. This assessment can be particularly challenging when dealing with highly mobile, shy and nocturnal animals such as flying-foxes. Here we investigated the dynamics of hunted populations of Pteropus ornatus and P. tonganus in the Northern Province of New Caledonia. First, an ethno-ecological survey involving 219 local experts identified 494 flying-fox roosts. Current status was assessed for 379 of them, among which 125 were no longer occupied, representing a loss of 33% over ca. 40 years. Second, species-specific counts conducted at 35 roosts, and a sample of animals killed by hunters, revealed that the endemic species, P. ornatus, was dominant (68.5%). Between 2010 and 2016, 30 roosts were counted annually during the pre-parturition period. Roosts size averaged 1,425 ± 2,151 individuals (N = 180 counts) and showed high among-year variations (roost-specific CV = 37–162%). If we recorded significant inter-annual variation, we did not detect a significant decline over the 7-yr period, although one roost went possibly extinct. Population size of the two species combined was estimated at 338,000−859,000 individuals distributed over ca. 400 roosts in the Northern Province. Flying-foxes are popular game species and constitute traditional food for all communities of New Caledonia. Annual bags derived from a food survey allowed us to estimate harvesting rates at 5–14%. Such a level of harvesting for species with a ‘slow’ demography, the occurrence of poaching and illegal trade, suggest the current species use might not be sustainable and further investigations are critically needed.
Conservation of endangered habitats of South Pacific islands is partially dependent on activity of seed dispersers. In consuming fruits, animals can spread seeds from parent plants to distant sites, thus contributing to plant regeneration and colonization of new sites. In the dry forests of New Caledonia, the red-bellied fruit-dove, Ptilinopus greyii, is a potential disperser of many fleshyfruited species. Trials with a captive bird showed that gut passage enhanced seed germination for Diospyros fasciculosa and Mimusops elengi but not for Vitex cf. collina, compared with whole fruits. Gut passage did not shorten duration of seed dormancy, which is consistent with evidence of a simple deinhibition effect for D. fasciculosa and M. elengi. Minimum Retention Time (MRT) of seeds in the gut differed significantly between the three tree species, from a mean of 17.4 min for D. fasciculosa to a mean of 52.4 min for M. elengi. These times are longer than observed foraging times in fruiting trees, potentially making this fruit-dove an effective seed disperser.
sera mis en ligne en texte intégral en septembre 2019International audienceGuano accumulated in caves by bats or birds contains a stratigraphic record of the environment which may supplement or supply conventionnal terrestrial sedimentary records like lacustrine/palustrine deposits or peat. Thus, guano study allows the understanding of recent or past climate and environment changes, which ability has expanded recently with the development of more sophisticated analytical tools, based on proxies that are indirect measures of past climates or environments preserved in natural archives. In New Caledonia, diurnal cave swiftlet Collocalia spodiopygia and nocturnal Chiroptera Micropterus robustior, both insectivores, share very often the same cavities. The comparison of the content of pollen and isotopes δ13C and δD in their respective guano, shows a great variability of constituents which reflects the sources of the feeding grounds of the eaten preys and their interaction with the ecosystem, more particularly the vegetation. The high richness of pollen taxa, identical to 50 % between the two guanos, underlines the respective food resource areas. The pollen content also shows seasonal variations probably in response to changes in food availability and in turn environmental change, if not climatic changes. This paper presents a preliminary set of results obtained on the 92cm-long core HAK1 retrieved in a guano mound taken under a cave swiftlet roost site in Hama Cave from Lifou (Loyalty Islands). The comparison between yearly mean daily rainfall, carbon (δ13C) and hydrogen (δD) isotopes compositions of high-molecular weight n-alkane (n-C29) from guano shows a good covariation, which is interpreted as a proxy of ENSO occurrences. Our work confirms that the guano piles are promising records for palaeoenvironmental change studies at high temporal resolution.L'intérêt est grandissant pour le potentiel présenté par les acccumulations cavernicoles de guano de chauves-souris et d'oi-seaux en tant qu'enregistrements stratigraphiques continentaux, complémentaires voire alternatifs aux archives étudiées générale-ment (sédiments lacustres, palustres, tourbeux, etc.). Ces dépôts permettent des reconstructions de la variabilité climatique à haute résolution pour des échelles de temps récentes à plus anciennes, grâce à la calibration de nouveaux proxies susceptibles d'enregistrer ces variations. Ainsi la comparaison du contenu pollinique et des traceurs isotopiques δ 13 C et δD des n-alcanes du guano de différents animaux insectivores, les salanganes diurnes (Collocalia spodiopygia) et les chiroptères nocturnes (Micropterus robustior) cohabitant dans de nombreuses grottes de Nouvelle-Calédonie, met en évidence une grande variabilité. Celle-ci est à l'image des cibles de nourrissage des proies appétées et de leur interaction avec les composantes de l'écosystème, en particulier les plantes. La grande richesse du contenu pollinique observée dans les deux types de guano, bien que présentant 50 % de taxons...
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