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Conservation implications of past and present nesting habitat selection of the endangered Osprey Pandion haliaetus population of the Canary Islands
Abstract
We studied nesting habitat selection of the endangered non-migratory Osprey Pandion haliaetus population of the Canary Islands and evaluated the effect of human expansion in recent decades. Compared with randomly selected potential nest-sites, Osprey nests were more frequently found on taller, southwest-facing cliffs, char-acterized by lower human pressure and closer to Yel-low-legged Gull Larus michahellis colonies and Barbary Falcon Falco pelegrinoides breeding sites. Furthermore, changes in some breeding habitat features have been detected in recent decades. According to our predictive models, large areas of suitable habitat are available but unoccupied in the Canaries, and human activities are probably limiting the settlement and dispersion of new pairs.
... for food resources or nesting sites (Katzner et al. 2003;Hakkarainen et al. 2004;Martínez et al. 2008); and usually, large species are very sensitive to human disturbances during breeding so they seek refuge in rugged, isolated, or protected areas (Richardson and Miller 1997;Rodríguez et al. 2013;Krü ger et al. 2015). They are considered umbrella species as their protection acts upon many other species, so areas with high density of breeding raptors support higher biodiversity levels than ones with low density of raptors (Murphy and Noon 1992;Sergio et al. 2008). ...
... Only some raptor populations, mainly the most threatened, are systematically monitored on the Macaronesian archipelagos (Don azar et al. 2002;Palma et al. 2004;Siverio 2006;Gangoso et al. 2015), and quantitative information on raptor communities, their distributions, and habitat associations are scarce (but see Gangoso 2006). In fact, only a few studies quantifying breeding habitat features or nest characteristics of particular species are available for the Canary Islands (see Carrillo and Gonz alez-D avila 2005;Gangoso 2006; Rodríguez and Siverio 2006;Rodríguez et al. 2007Rodríguez et al. , 2010bRodríguez et al. , 2013Gangoso et al. 2015). ...
... Our results highlight the high conservation value of Teno for birds of prey. It is a very important stronghold for the threatened studied raptors: 1) the unique ospreys breeding pairs of the island, which constitute more than 30% of the Canarian breeding population, are bound to the Teno coastal cliffs (Rodríguez et al. 2013); 2) the first Barbary falcon breeding pairs of Tenerife were discovered on Teno in the early 1990s, since then the insular population has spread through the island reaching more than 35 pairs at present (31% of them breeding in Teno; Siverio et al. 2009Siverio et al. , 2010a; 3) the common raven was formerly distributed through the island, but during the last four decades it has suffered a sharp decline and the bulk of the breeding insular population survived restricted to Teno (Lorenzo 2007;Siverio et al. 2007). In addition, many endemic plants and invertebrates occur there (Reyes-Betancort et al. 2008;Martín 2010), and some vertebrates maintain their more important or unique insular breeding populations there, such as for example the Canarian spotted lizard Gallotia intermedia, the Manx shearwater Puffinus puffinus, or the rock sparrow Petronia petronia (Rodríguez et al. 2014). ...
The specific spatial distribution and habitat association -strongly influenced by environmental factors or competitive interactions- are major issues in ecology and conservation. We located and georeferenced nesting sites of five cliff-nesting raptors (Egyptian vulture Neophron percnopterus, common buzzard Buteo buteo, osprey Pandion haliaetus, common kestrel Falco tinnunculus, Barbary falcon Falco peregrinus pelegrinoides), and common raven Corvus corax on one of the most biodiverse hotspot within the Canary Islands (Teno, Tenerife). We used generalised linear models to evaluate the factors affecting abundance, richness and intra- and interspecific interactions. Raptor abundance increased with slope, shrub-covered area, and habitat diversity, and decreased with altitude, and forested and grassed areas. Richness increased with slope and decreased with altitude. Threatened species (osprey, Barbary falcon and raven) occupied cliffs farther away from houses and roads, and more rugged areas than the non-threatened species. The models suggested that the probability of cliff occupation by buzzards, falcons and ravens depended only on inter-specific interactions. Buzzard occupation increased with the distance to the nearest raven and kestrel nests, whereas falcons and ravens seek proximity to each other. Teno holds between 75-100% of the insular breeding populations of the most endangered species (osprey and raven), indicating the high conservation value of this area. Our study suggests that the preservation of rugged terrains and areas of low human pressure are key factors for raptor conservation and provide basic knowledge on the community structure and habitat associations to develop appropriated management actions for these fragile island populations.
... En las islas Canarias y Baleares ambos modelos destacan las zonas costeras donde predominan los acantilados. Numerosos sectores costeros de Canarias, en los que hoy día no hay águilas pescadoras afincadas, son adecuados para albergar territorios si se tienen en cuenta las características físicas que poseen (Rodríguez et al., 2013). ...
... En el archipiélago canario, los nidos se sitúan en acantilados marinos situados en las costas orientadas al sur y suroeste de las islas, sobre todo de las occidentales. No obstante, podrían asentase en otros acantilados que cumplan ciertos requisitos, como por ejemplo tener más de 50 m de altura, aunque probablemente las actividades humanas impidan esa expansión (Rodríguez et al., 2013). De igual forma podría ocurrir en las Baleares, donde la población es rupícola como la canaria y existe hábitat disponible, si bien las actividades turísticas también condicionarían ese posible aumento de superficie ocupada (Martínez y Muntaner en Siverio et al., 2018). ...
... The Osprey (Pandion haliaetus) has a very fragmented breeding distribution in the Mediterranean region, being restricted to a few pockets in islands and some coastal stretches of northwest Africa (Monti, 2012), besides the founder populations reintroduced in southern continental Spain (Muriel et al., 2010) and southern Portugal (Palma et al., 2013). The species also has a small breeding population in the Canaries (Rodríguez et al., 2013;Siverio et al., 2018) and a much larger one in Cabo Verde, of about 100 pairs (Palma et al., 2004;L. Palma, unpublished data). ...
... Она îгранè÷åна нåñêîльêèмè îблаñòямè на îñòрîâаõ è нåêîòîрûмè îòрåçêамè бåрåгîâîé çîнîé ñåâåрî-çаïаднîé Àфрèêè (Monti, 2012), ïîмèмî åùё дâуõ ïîïуляцèé, âнîâь îñнîâаннûõ ñ ïîмîùью мåòîда рåèнòрîдуêцèè â южнîé êîнòèнåнòальнîé Иñïанèè (Muriel et al., 2010) è южнîé Ïîрòугалèè (Palma et al., 2013). Нåбîльшая гнåçдîâая ïîïуляцèя òаêжå åñòь на Канараõ (Rodríguez et al., 2013;Siverio et al., 2018) è îдна, çна-÷èòåльнî бîльшå è ÷èñлåннîñòью îêîлî 100 ïар, â Кабî Âåрдå (Palma et al., 2004;L. Palma, нåîïублèêîâаннûå даннûå). ...
Ospreys bred along most of coastal Portugal until the beginning of the 20th century. Thereafter, a continuous decline due to persistent persecution and habitat loss led the species to extinction as a breeder in 2002, long after its disappearance from the rest of continental Iberia. Reintroduction by hacking was the only remaining option to restore a breeding population. With the collaboration of Finland and Sweden as donor countries, a 5-year translocation project (2011–2015) was carried out in a vast inland reservoir. A total of 56 nestlings were translocated, of which 47 successfully dispersed. From 2016–2018, the follow-up of the project was devoted to improving nesting conditions through putting in place artificial platforms in a wide set of favourable areas (reservoirs, estuarine marshlands, large rivers), especially those regularly used by over-summering ospreys. So far, 25 platforms of different types were set up. The first two breeding pairs settled down in 2015, the last year of translocations, one in the release area and the other on the rocky coast, both with a successful outcome. During the 2018 breeding season there were already 5 territorial pairs, of which one bred successfully.
... The Osprey Pandion haliaetus is a long-distance migratory raptor that is widely distributed across the northern hemisphere. Research on Ospreys worldwide has often focused on the breeding season (Green 1976, Bustamante 1995 and informing conservation strategies at breeding sites, eg guiding the width of disturbance-buffer zones around nests, identifying priority areas for reserves and informing the location of artificial nesting structures (Lőhmus 2001, Toschik et al 2006, Bai et al 2009, Rodríguez et al 2013. Such a focus on the breeding season is disproportionate, as northern European Ospreys spend over half of their year away from the breeding grounds on migration and at wintering sites in tropical West Africa , Dennis 2008, Bai & Schmidt 2012. ...
... Overall, we found that Ospreys avoided urban areas, which supports previous literature showing that Ospreys prefer habitat with low human disturbance during the non-breeding season (Galarza & Dennis 2009. Similarly, Rodríguez et al (2013) found that nesting Canarian Ospreys avoided human settlements and access routes, indicating that human settlements limit habitat use by Ospreys. However, Casado & Ferrer (2005) found that Ospreys wintering in Spain selected water bodies closer to urban centres. ...
In this study, we use satellite-tracking data from five juvenile Scottish Ospreys Pandion haliaetus to explore habitat preferences at stopover and wintering sites. Daily activity patterns were analysed using a binomial generalised linear model. Kernel density estimation was used to identify core areas at stopover sites and seasonal ranges at the wintering site. A ‘use versus available habitat’ study design was implemented to test whether Ospreys showed preference for a variety of landscape and land-cover variables and for protected areas. Autumn migration strategies varied between individuals, with some Ospreys using stopover sites in France, Spain and Morocco. Ospreys wintered at sites in West Africa. Activity levels varied through the day, with localised peaks at 11:00 and 15:00 h. Ospreys preferred to be near to water features (rivers, lakes, ocean) while avoiding urban areas. Individual differences were observed when considering preference for forest and open-area land-cover classes. Overall, Ospreys did not preferentially use protected areas. Our research confirms already well-established preferences for aquatic habitats, but preference for or avoidance of other habitats, including protected areas, varied between individuals. We highlight the potential of combining satellite-tracking data with environmental data sources to explore the spatial ecology of migratory birds at stopover and wintering sites abroad.
... Therefore, human disturbances might explain our findings. In the Canary Islands, where the osprey population is declining, current nests are located higher on coastal cliffs than those used in the past, as a consequence of human disturbance (Rodríguez et al., 2013b). ...
The use of anthropogenic debris as nest-building materials may affect nest function. We study ospreys (Pandion haliaetus) on an island with scarce vegetation and high availability of beached marine debris. We describe the anthropogenic debris in osprey nests, evaluate the factors affecting its prevalence and abundance, and test its potential effects on breeding parameters. We also quantify plastic entanglements among adults and nestlings. Of the 36 studied nests, 92 % included non-natural items, with plastic being the most frequent material (88.9 %). Nests that were bigger and closer to the coast had more anthropogenic items. The abundance of anthropogenic items in nests did not correlate with osprey breeding parameters. We recorded two live entangled adult females, which represent 3.9 % of the adult population. Monitoring the abundance of anthropogenic debris and its effects on wildlife is necessary to guarantee long-term viability of coastal wildlife.
... La investigación reciente sobre el águila pescadora se ha centrado principalmente en la población reproductora (Crawford y Long, 2017), especialmente en la conservación de las áreas de reproducción (Lohmus, 2001;Toschik et al., 2006;Bai et al., 2009;Rodríguez et al., 2013). Sin embargo, las águilas pescadoras de Europa occidental pasan más de la mitad del año en migración y en sus áreas de invernada tradicionales en África (Hake et al., 2001;Alerstam et al., 2006;Dennis 2008;Bai y Schmidt, 2012) y, más recientemente, en el sur de Europa (Sanz, 1997). ...
... La investigación reciente sobre el águila pescadora se ha centrado principalmente en la población reproductora (Crawford y Long, 2017), especialmente en la conservación de las áreas de reproducción (Lohmus, 2001;Toschik et al., 2006;Bai et al., 2009;Rodríguez et al., 2013). Sin embargo, las águilas pescadoras de Europa occidental pasan más de la mitad del año en migración y en sus áreas de invernada tradicionales en África (Hake et al., 2001;Alerstam et al., 2006;Dennis 2008;Bai y Schmidt, 2012) y, más recientemente, en el sur de Europa (Sanz, 1997). ...
Osprey Pandion haliaetus breeding population in Portugal (2018)
Palma, L. y Safara, J. 2018. Censo de la población reproductora de guincho o águila pescadora en Portugal en 2018. En, M. Siverio, F. Siverio, B. Rodríguez y J. C. del Moral (Eds.): El águila pescadora en España y Portugal: población invernante 2016-2017, reproductora en 2018 y método de censo, pp. 35-38. SEO/BirdLife. Madrid.
... La investigación reciente sobre el águila pescadora se ha centrado principalmente en la población reproductora (Crawford y Long, 2017), especialmente en la conservación de las áreas de reproducción (Lohmus, 2001;Toschik et al., 2006;Bai et al., 2009;Rodríguez et al., 2013). Sin embargo, las águilas pescadoras de Europa occidental pasan más de la mitad del año en migración y en sus áreas de invernada tradicionales en África (Hake et al., 2001;Alerstam et al., 2006;Dennis 2008;Bai y Schmidt, 2012) y, más recientemente, en el sur de Europa (Sanz, 1997). ...
... For most raptors, including Ospreys, the availability of nest sites and food supply can limit breeding density (Newton et al. 1977;Newton 1979;Donazar and Ceballos 1989;Poole 1989b;Donazar et al. 1993;Sergio et al. 2002;Rodríguez et al. 2013). In the case of Ospreys, proximity to water bodies, which serve as the only foraging sites for this species, are among the most important factors limiting distribution (Poole 1989b;Lõhmus 2001;Bai et al. 2009) as are suitable trees for nesting (Saurola 1997). ...
The Osprey (Pandion haliaetus) is an emblematic example of conservation. Currently, the species is progressively recovering in population size and range after dramatic reductions as a consequence of human persecution and the use of pesticides in the nineteenth and twentieth centuries. Here, we analysed the population trend and productivity in relation to the nesting substrate (artificial structures or trees) and the protection status of the nest location (inside or outside protected areas) in the eastern German population of Ospreys. The Osprey population steadily grew during the study period (2000–2009), accompanied by the increased use of artificial structures for nesting, possibly due to the scarcity of suitable natural nest sites in the region. Pairs nesting in trees showed higher variance in productivity than those nesting on artificial supports during the study period. Further, the productivity recorded in Ospreys nesting on natural sites decreased during the study period, regardless of the protection status of the nest location, whereas it did not vary for pairs nesting on artificial structures. The productivity of Ospreys was also related to the protection status of the nest location since pairs breeding inside protected areas, either in natural or on artificial nest sites, showed higher productivity than pairs nesting outside protected areas. These findings suggest that the protection of the nest location and the type of substrate used for nesting are relevant factors underlying the breeding performance in this Osprey population and are therefore key to its management.
... These species, locally associated with rocky habitats, made nests on rocky ledges, and their territories included cliffs and inaccessible rocks which could be continuously occupied for long period, highlighting the great importance of this type of nesting site (Ciach 2005; Czy owicz 2014). The inaccessibility of nesting sites could be one of the major drivers of habitat selection (Rodríguez et al. 2013) and could be a (Amato et al. 2014). Apart from enhancing biodiversity, rocky environments also increase the diversity of ecological relationships. ...
Rocky habitats are regarded as biodiversity hot-spots. Along with high species diversity, diverse ecological relationships can be observed in these habitats. Large groups of bird species use rocks in various ways: as perching/roosting sites, breeding or foraging habitats, information exchange sites, display arenas or as sources of minerals and water. Because of the inaccessibility of these environments, their role and importance to animals has been underestimated. We evaluated the use of rocky habitats by birds in the Tatra Mountains (49°13′N; 19°57′E, Carpathians, central Europe). Rocky habitats were used by 29 bird species, eight of which used cliffs directly (i.e. for nesting, foraging or resting). The number of species recorded as using cliffs was correlated with the surface area of the cliff face. A total of 20 forms of rocky habitat use were recorded, in five behavioural categories: vocalization, foraging, perching, flight and nesting. Prevailing behaviours were flying by a rock face, circling above the face, and vocalization on a tree/shrub growing next to a rock. Rocks provide a nesting habitat for specialized petrophilic species and permit the existence of numerous ecological relations between species and habitats. The results of this study show that rocky habitats support the diversity of ecological relationships.
Pandion haliaetus en El Oeste Paleártico: Tamaño de La Población Reproductiva Y Tendencias A Comienzos Del Siglo XXI El número de parejas nidificantes de Pandion haliaetus registradas en Europa, el norte de África y Oriente Medio ha alcanzado entre 9500 y 11 500 a comienzos del siglo XXI. Comparado con los números de la década de 1980 (ca. 5500 pares), la población casi se ha duplicado. El incremento es más obvio en países como Alemania y el Reino Unido. Las poblaciones europeas más grandes e importantes en Suecia, Finlandia y Rusia parecen ser estables. En contraste, Portugal, España continental y Turquía perdieron sus últimas parejas reproductivas en las décadas de 1980 y 1990. También fueron reportadas tendencias negativas en Polonia debido a la persecución y en el sudeste europeo y norte de África, donde sólo quedan pocas parejas. Las reintroducciones en Inglaterra, España e Italia han resultado en unas cuantas parejas reproductivas nuevas en años recientes.
The Teno range of mountains, located in the northwest Tenerife, Canary Islands, is still a refuge for the flora and fauna of the island. Until now, at least four native species of reptiles, 232 of birds (both breeding and migrant), and six mammals have been recorded for that site. For some of these animals, such as Canarian Spotted Lizard (Gallotia intermedia), Manx Shearwater (Puffinus puffinus), Osprey (Pandion haliaetus), Rock Sparrow (Petronia petronia) and Northern Raven (Corvus corax), these cliffs, gorges, tablelands or forests hold a good part or all of their insular populations. This illustrated and annotated checklist synthesizes and updates the available information on terrestrial vertebrates for the entire northwestern area of Tenerife. A current and comprehensive list of extant species supports effective management strategies and conservation projects as well as the efficient dissemination of information regarding this Natural Heritage. More info at http://www.gohnic.org/noticias/nuevas-publicaciones-gohnic/
In situ visual surveys using a hierarchical sampling design were carried out at 36 sublittoral rocky locations along the central-east Atlantic Canarian Archipelago to find relationships among (1) benthic primary producers, (2) the demographic structure of the herbivorous sea urchin Diadema antillarum Phillipi and (3) the trophic structure of coastal fish communities. Our correlation approach displayed a relationship between the lack of large macroinvertebrate-eating predatory fish and the increase in density of sea urchins, in addition to a decrease in fish richness. In contrast, increases in fast-growing plankton feeding fish species were detected. The size structure of D. antillarum is dominated by small-to-intermediate sized sea urchins in environments with a high density of individuals, whereas low sea urchin density locations are characterized by the dominance of large
sized individuals. The physical complexity of the substrate seems to play an important role in determining the local patchiness of D. antillarum. Finally, a non-linear decrease in the percentage of fleshy macroalgal cover with increasing density of D. antillarum was observed. We therefore propose D. antillarum as a key herbivorous species, which plays an important role in determining the structure of shallow, hard-substratum, infralittoral benthic communities throughout the Canary Islands.
In 1998 and 1999, we carried out a systematic survey of the Osprey (Pandion haliaetus) in the Cape Verde Islands, to evaluate its population and conservation status. Some poorly surveyed areas were revisited in the summer of 2001 to complete our status assessment. We found an estimated 72-81 pairs on the archipelago, of which 94% were concentrated in the northern Barlavento (windward) islands group. In this area the species is common and seems to be recovering from a presumed decline, probably caused by a long-term overharvesting of eggs and nestlings by humans during past decades. On the contrary, in the southern Sotavento (leeward) islands the species is currently scarce, seemingly still on the decline and already extirpated in the southwesternmost islands. The high percentage of abandoned near-shore nests in the eastern ''flat'' islands is probably associated with the increasing tourism activities. ESTADO ACTUAL DEL A ´ GUILA PESCADORA PANDION HALIAETUS EN LAS ISLAS DE CABO VERDE RESUMEN.-Durante el año 1998 y la primavera de 1999 se hizo una prospección sistemática del a ´guila pescadora (Pandion haliaetus) en las islas de Cabo Verde con la intención de actualizar la información sobre su estado poblacional y de conservación. Algunas a ´reas peor prospectadas fueran visitadas en el verano de 2001 para confirmar datos anteriores. Se obtuvo como estimación más probable el nú mero de 72-81 parejas reproductoras en todo el archipiélago, largamente (94%) concentradas en el grupo de islas septentrionales del Barlavento. En este a ´rea, la especie es bastante común y parece estar recu-perándose de un presunto declive durante las décadas pasadas, como resultado probable de un contínuo expolio de huevos y pollos para la alimentación humana. Al contrario, en las islas del grupo sureño del Sotavento, la especie es actualmente muy escasa y sigue aparentemente en declive y incluso ya extinguida en las islas del extremo suroccidental. El incremento del turismo costero constituye una amenaza adi-cional para los nú cleos poblacionales de las islas ''llanas'' orientales al echar la especie de sus sitios vulnerables de nidificación costera, como lo indica el alto porcentaje de nidos abandonados a lo largo del litoral. [Traducción de los autores]
El Águila Pescadora se encuentra En Peligro Crítico 1 por tener una población muy pequeña (2001-2002) de unas 30-38 parejas repartidas en dos núcleos aislados (archipiélagos balear y canario).Alo largo de las décadas de los años sesenta, setenta y principios de los ochenta, sufrió una drástica disminución en sendas subpoblaciones, habiendo desaparecido como reproductor de las costas levantinas y andaluzas. A pesar de haber mostrado una recuperación importante en las últimas décadas, sus efectivos se consideran demasiado exiguos, probablemente muy cercanos al límite de la capacidad de acogida del hábitat, siendo por ello muy incierta su viabilidad.
Breeding population size and some reproductive aspects of Osprey Pandion haliaetus in La Gomera and El Hierro (Canary Islands) were studied during the 2003 and 2004 breeding seasons. All active nests were situated in the southern coasts of both islands. A total of five territorial pairs were detected in La Gomera and one in El Hierro, nesting three in La Gomera and one in El Hierro. These islands contain about 30% of the entire Canarian Osprey population and 16-17% of the Spanish population. Laying dates, estimated in ten day periods, were 21-31 March (n=3) and 1-10 May (n=2). Mean productivity (0.86) was lower than that estimated by some authors for stable populations. Human activities such as recreational sailing, trekking or camping near the nests could limit the establishment of new pairs and cause low productivity.
We studied the causes of raptor admissions to the only wildlife rehabilitation center on the largest island of the Canarian Archipelago (Tenerife) over ten years (1998–2007). A total of 2611 birds of prey, belonging to nine falconiform diurnal raptor and four strigiform species, were admitted. The Eurasian Kestrel (Falco tinnunculus) and the Long-eared Owl (Asio otus) were the species most commonly admitted and jointly made up 85.6% of admissions. The most frequent causes of admission to the wildlife rehabilitation center were collisions (with cars, high-voltage electric transmission towers, etc.; 42.2%), starvation (5.1%) and entanglement in glue traps intended for rodents (4.7%). Poisoning and shooting were recorded for 2.4 and 1.5% of the birds admitted, respectively. Only collisions increased during the study period. A total of 1010 birds (44.4% of the total) were released to the wild following rehabilitation. We recommend more financial support for rehabilitation centers to develop detailed analytical diagnoses and rehabilitation services.
Recent insights from habitat selection theory may help conservation managers encourage released animals to settle in appropriate habitats. By all measures, success rates for captive–release and translocation programs are low, and have shown few signs of improvement in recent years. We consider situations in which free-living dispersers prefer new habitats that contain stimuli comparable to those in their natal habitat, a phenomenon called natal habitat preference induction (NHPI). Theory predicts NHPI when dispersers experienced favorable conditions in their natal habitat, and have difficulty estimating the quality of unfamiliar habitats. NHPI is especially likely to occur when performance in a given habitat is enhanced if an animal developed in that same habitat type. Animals exhibiting NHPI are expected to rely on conspicuous cues that can be quickly and easily detected during search, and to prefer new habitats possessing cues that match those encountered in their natal habitat.A major obstacle to successful relocations is that newly released animals often reject the habitat near the release site and rapidly travel long distances away before settling. An NHPI perspective argues that long-distance movements away from release sites occur because releasees prefer to settle in familiar types of habitat, and reject novel areas lacking cues similar to those in their habitat of origin. Similarly, a preference by releasees for familiar cues may encourage them to seek out inappropriate, low quality habitats following release at a new location. We review evidence from a number of studies indicating that problems with habitat selection behavior compromise conservation efforts, and provide recommendations that may encourage animals to “feel more at home” in post-release habitats.
Territory spacing and breeding rates of an insular population (north-western Tenerife, Canary Islands) of Barbary Falcon Falco peregrinus pelegrinoides was studied from 1993 to 2008. The population increased constantly since the outset, from two pairs in 1993 to 12 in 2008. Mean density was 5.48 pairs per 100 km and mean nearest neighbour distance was 3 119 m. The regularity of the spatial distribution pattern of the nests, observed in most years, may be maintained in the future despite the expectation that new pairs may occupy still-vacant territories. Considering the 79 breeding attempts analysed, the mean number of fledged young per territorial pair was 1.92, per laying pair was 2.0 (n = 76), and per successful pair was 2.24 (n = 68). No significant variations were observed between the annual mean number of fledged young per laying pair, nor between the number of fledged young of pairs according to density in a 5 km radius. All fledglings (brood size one to four) left the nest in the month of May. In order to avoid affecting breeding success, sporting activities practised in the breeding areas must be correctly managed by the appropriate authorities.
We studied density, habitat selection and reproduction of Barbary Falcons Falco peregrinus pelegrinoides on Tenerife Island during 2004 and 2005. A total of 26 breeding pairs were counted, all of them occupying natural cliffs around the island. Density observed was 1.27 pairs/100 km2, and was positively correlated with cliff availability. Mean distance between neighbouring pairs was 5869 ± 3338 m, ranging from 1388–13 610 m; in some areas this value was as low as 2062 ± 673 m. Tenerife still shows potential for further increase regarding the observations of single females and the availability of potentially suitable but unoccupied cliffs. Falcons selected taller cliffs, more apart from roads and houses, near the coast, with lower presence of cultivated and urban areas, and associated with other cliff-nesting species. Stepwise discriminant analysis of habitat selection selected cliff height, nearest neighbour distance and distance to road, and correctly classified 71.1% of the cases. Productivity averaged 1.55 fledged young/pair and breeding success was 81.1%. No correlations were observed between habitat features and productivity. Since most territories are located in protected zones and human disturbance seems to be absent, special management measures are not necessary. However, further study into the biology of this population is required for effective and timely conservation of this species if need be.
We studied the diet of the osprey Pandion haliaetus in the Canary Islands during 1997-2008 using prey remains under perches and nests, and direct observations. We collected data both in breeding territories and in non-breeding areas. We counted a minimum of 307 fish individuals as prey remains (both during breeding and non-breeding seasons), and identified another 78 during 433 hours of field observations. According to our results, ospreys consumed at least 15 taxa belonging to 12 families. We found slight differences in the spatial (both intra and inter insular) and temporal diet composition. During the breeding season, the main prey species were flying fishes (belonging to the family Exocoetidae) and needlefishes (belonging to the family Belonidae) according to the two employed methods (i.e. prey remains and direct observations). In the non-breeding period, the diet was composed primarily of non-autochthones freshwater fishes such as common carp Cyprinus carpio and goldfish Carassius auratus. In general, the diet diversity was similar to the diversity reported in other breeding populations of subtropical areas, and being less diverse than those of tropical areas. More precise studies evaluating the effect of fish availability in marine reserves, overfishing areas or fish farms on the demographic parameters are necessary for the management and conservation of threatened Canarian ospreys.
The advent of GIS is initiating a rapid increase in the utilization of wildlife-habitat models as tools for species and habitat management. However, such models rarely include estimates of interspecific interactions among explanatory variables. We tested the importance of such variables by using the peregrine falcon Falco peregrinus, a medium-sized raptor frequently reported to be affected by heterospecifics, as a model species. In an Alpine population, compared to random locations, peregrines selected breeding sites farther from conspecifics, on taller cliffs, with higher availability of farmland and closer to raven Corvus corax nests. Within suitable habitat, peregrines selected sites near ravens and far from elevations associated with golden eagle Aquila chrysaetos nests. Productivity increased with cliff size, farmland availability (rich in the local main prey) and with proximity to ravens, suggesting that the observed choices were adaptive. Finally, at the regional level, peregrine density peaked at low elevation and was positively associated with raven density. The results suggested an active breeding association of peregrines with ravens, which may provide early-warning cues against predators and safe alternative nest-sites. They also confirmed the importance of including estimates of interspecific interactions among explanatory variables, which may: 1) make models more realistic; 2) increase their predictive power by lowering unexplained variance due to unmeasured factors; 3) provide unexpected results such as the cryptic, large-scale breeding association of our study; and 4) stimulate further hypothesis formulation and testing, ultimately leading to deeper ecological knowledge of the study system.
We studied the nest site selection and distribution pattern at landscape level of the German Osprey population, and demonstrated
how to test the predictions of the ideal free distribution theory and its derivatives on such an expanding population. Information
about the location and breeding success of each Osprey nest site between 1995 and 2005 was collected through a long-term monitoring
programme. Data of land cover types were acquired from the administrations of each federal state and the CORINE Land Cover
database. The results showed that Ospreys preferred landscapes with more water bodies and forests. Such sites were also occupied
earlier and had higher local population density. However, in the study period of 11years, there was a gradual shift from
forest-dominated landscapes to agricultural land-dominated landscapes. The breeding success increased over time, with no difference
in the breeding success between pairs nesting on trees and poles, whereas there was higher breeding success at nest sites
surrounded by more agricultural land and less forest. The more efficient foraging in eutrophic lakes in agricultural landscapes
was the most likely cause for the higher breeding success. The distribution pattern of the Ospreys did not match the resource
allocation, which deviated from the models tested. We suggested that the proximate cues used for nest site selection mismatched
site quality due to anthropogenic environmental changes.
According to the "habitat copying" hypothesis, animals use the reproductive performance of conspecifics to assess habitat suitability and choose their future breeding site. This is because conspecifics share ecological needs and thus indicate habitat suitability. Here, we propose the "heterospecific habitat copying" hypothesis, which states that animals should use public information (i.e., information derived from the performance of others) from con- and heterospecifics sharing ecological needs. In a correlational approach we test some assumptions and predictions of this hypothesis with a data set from two sympatric bird populations, rollers (Coracias garrulus) and kestrels (Falco tinnunculus), using the same nest-boxes and exploiting similar food resources. Since kestrels are residents and breed earlier, we assumed that they are dominant over rollers for nest-box acquisition. The environment appears to be patchy for both species and temporally predictable for kestrels only. Two results suggest that the use of heterospecific public information in breeding habitat selection may be at work: (1) an increase in the reoccupancy probability by kestrels of previous roller nests with increasing nest success, and (2) an increase in roller breeding population with increasing local kestrel success. Most of the other observed patterns could be explained by alternative mechanisms such as natal philopatry, breeding fidelity, conspecific attraction, intraspecific habitat copying, and the effect of interspecific competition. Copyright 2005.
The earth's biodiversity currently faces an extinction crisis that is unprecedented. Conservationists attempt to intervene in the extinction process either locally by protecting or restoring important species and habitats, or at national and international levels by influencing key policies and promoting debate. Reliable information is the foundation upon which these efforts are based, which places research at the heart of biodiversity conservation. The role of research in such conservation is diverse. It includes understanding why biodiversity is important, defining 'units' of biodiversity, priority-setting for species and sites, managing endangered and declining populations, understanding large-scale processes, making predictions about the future and interfacing with training, education, public awareness and policy initiatives. Using examples from a wide range of bird conservation work worldwide, researchers consider the principles underlying these issues, and illustrate how these principles have been applied to address actual conservation problems for students, practitioners and researchers in conservation biology.
Several studies have documented flushing distance responses of raptors to a variety of activities during breeding and nonbreeding seasons (Table 2); however, except for anecdotal and incidental reports, few studies have experimentally documented disturbance distances for use in buffer-zone recommendations (White and Thurow 1985, Holmes et al. 1993). The wide range of recommendations (Table 1) probably reflects site-specific anthropogenic and environmental conditions (Suter and Joness 1981, Fraser 1983). To be effective, buffer zones should be based on empirical evidence of wildlife responses to disturbance (Knight and Skagen 1988). Several authors suggest the need for further disturbance studies to determine flushing responses among different species (White and Thurow 1985, Postovit and Postovit 1987, Knight and Temple 1995). The City of Boulder Open Space Department and Mountain Parks Division have used spatial and temporal buffer zones successfully for a number of years to protect cliff-nesting peregrine falcons, prairie falcons, and golden eagles. Closures are in effect from February through July annually and vary in distance by 50-400 m depending on topography, nest location, and species. Extensive public education accompanies the closures, including direct mailings to outdoor recreation shops in the area, closure signs at trailheads, press releases, and access to a 24-hour telephone information line and a site on the World Wide Web. In addition, nest sites are monitored weekly by trained volunteers. With proper planning, extensive observations of target individuals and groups, and aggressive public education, spatial and temporal buffer zones provide a useful tool for protecting raptors to resource managers.
An Osprey (Pandion haliaetus) population nesting in the vicinity of Cascade Reservoir in west-central Idaho was studied for three years. The area supported about 50 nesting pairs, which laid an average of 2.58 eggs and fledged an average of 1.37 young per active nest throughout the study. These productivity estimates suggest a healthy, increasing population. Most nests were atop snags (66%) and on private land (70%). Ospreys nesting on artificial sites and those nesting more than 1,500 m from human disturbances produced more offspring. Fish in the 11-30 cm range constituted the bulk of the diet (89%) with brown bullheads being the most important prey species (38%). Osprey captures reflected prey availability. Establishment of Cascade Reservoir increased the availability of fish, which, in turn, allowed the Osprey population to increase. Productivity of these hawks appears to be chiefly related to reservoir level and prey availability.
The status and distribution of the Osprey (Pandion haliaetus) in Japan is poorly known, although it is considered as a near threatened species nationally. We studied the status, distribution and habitat characteristics of Ospreys breeding in Hokkaido, the northern island of Japan, from 2002 to 2003. During this period we located 62 Osprey nests and confirmed breeding in 8 of 14 districts of Hokkaido, indicating a sizable population breeding in Japan. Most Ospreys occurred in the western part of Hokkaido. We also found nests in two northern (16%) and one central (16%) districts, where breeding had not previously been confirmed, possibly representing a range expansion or previous underreporting. More than half of all nest sites (n = 35) were on rocks or cliffs, while elsewhere in the world nests in such situations appear to be scarce. The distribution of nesting Ospreys is concentrated where the frequency of the White-tailed Eagle (Haliaeetus albicilla) is lower, suggesting that the Osprey's range in these areas is restricted by avoidance of competition with or predation by eagles. The breeding population should be carefully monitored, because human activity at breeding sites or associated foraging sites could affect the population trend.
Se conoce muy poco sobre el estatus y la distribución de Pandion haliaetus en Japón, aunque es considerada como una especia casi amenazada a nivel nacional. Estudiamos el estatus, la distribución y las características del hábitat de individuos reproductivos de P. haliaetus en Hokkaido, la isla norte de Japón, desde 2002 hasta 2003. Durante este período localizamos 62 nidos y confirmamos la reproducción en 8 de 14 distritos de Hokkaido, indicando una población considerable reproduciéndose en Japón. La mayoría de los individuos se localizaron en la parte oeste de Hokkaido. También encontramos nidos en dos distritos norte (16%) y uno central (16%), donde la reproducción no había sido confirmada anteriormente, posiblemente representando una expansión del rango de distribución o la falta previa de detección. Más de la mitad de todos los sitios de nidificación (n = 35) estuvieron sobre rocas o en acantilados, mientras que en cualquier otro lugar del mundo los nidos en estas situaciones parecen ser escasos. La distribución de los individuos anidando se concentra donde la frecuencia de Haliaeetus albicilla es baja, sugiriendo que el rango de distribución de los individuos de P. haliaetus en estas áreas está restringido para evitar la competencia o la depredación por parte de las águilas. La población reproductiva debe ser monitoreada cuidadosamente, debido a que la actividad humana en los sitios reproductivos o en los sitios de forrajeo asociados puede afectar la tendencia poblacional.
In 1998 and 1999, we carried out a systematic survey of the Osprey (Pandion haliaetus )i nthe Cape Verde Islands, to evaluate its population and conservation status. Some poorly surveyed areas were revisited in the summer of 2001 to complete our status assessment. We found an estimated 72-81 pairs on the archipelago, of which 94% were concentrated in the northern Barlavento (windward) islands group. In this area the species is common and seems to be recovering from a presumed decline, probably caused by a long-term overharvesting of eggs and nestlings by humans during past decades. On the contrary, in the southern Sotavento (leeward) islands the species is currently scarce, seemingly still on the decline and already extirpated in the southwesternmost islands. The high percentage of abandoned near-shore nests in the eastern ''flat'' islands is probably associated with the increasing tourism activities.
Ospreys (Pandion haliaetus) have been the focus of conservation efforts since their dramatic population decline attributed to dichlorodiphenyltrichloroethane and related chemicals in the 1960s. Several recent studies of ospreys nesting in the United States have indicated improved reproduction. However, the density of breeding ospreys varies greatly among locations, with some areas seemingly habitable but not occupied. Because of concerns about pollution in the highly industrialized portions of the Delaware River and Bay, USA, we evaluated contaminant exposure and productivity in ospreys nesting on the Delaware River and Bay in 2002. We characterized habitat in the coastal zone of Delaware, USA, and the area around the river in Pennsylvania, USA, using data we collected as well as extant information provided by state and federal sources. We characterized habitat based on locations of occupied osprey nests in Delaware and Pennsylvania. We evaluated water clarity, water depth, land use and land cover, nest availability, and contaminants in sediment for use in a nest-occupancy model. Our results demonstrated that the presence of occupied nests was associated with water depth, water clarity, distance to an occupied osprey nest, and presence of urban land use, whereas a companion study demonstrated that hatching success was associated with the principal components derived from organochlorine-contaminant concentrations in osprey eggs (total polychlorinated biphenyls, p,p′-dichlorodiphenylethylene, chlordane and metabolites, and heptachlor epoxide). Our study provides guidelines for resource managers and local conservation organizations in management of ospreys and in development of habitat models that are appropriate for other piscivorous and marsh-nesting birds.
Exploiting the nest defence behaviour of another relatively aggressive species is one of the most unusual amongst a great diversity of strategies used by animals to evade predation. Here we review 62 studies that have looked at protective nesting associations in which at least one species is a bird. Most ‘protected’ associates are found in the Anseriformes, the Charadriiformes and the Passeriformes, while most ‘protective’ associates come from the Charadriiformes and the Falconiformes. Protected associates primarily benefit from a reduced predation rate when nesting near protective species although a variety of other, often unusual benefits have been described, including early warning of predators, lower parasitism, lower brood-parasitism, nest stability and higher mating success. Protected associates sometimes also pay costs when they or their young are killed by their aggressive associate, or when they are forced to abandon their nest. Two studies demonstrate that protected species manipulate the trade-off between the costs and benefits of nesting near an aggressive associate, while only a handful of studies have found specific adaptations to help avoid costs. In contrast, there is little evidence to suggest that the protective associates pay costs or gain benefits. This is probably because few researchers set out to test this hypothesis specifically, but we tentatively conclude that the majority of nesting associations are commensal in nature, and that only a few are parasitic or mutualistic. Many studies show that nesting associations occur by active choice and not because the associate species choose similar habitat, but only one study does so experimentally. In two cases the nesting association is obligatory for one of the species but there was also evidence for significant local adaptation to nesting near protective species, sometimes across a broad geographical range. Finally, we identify potential pathways that may have led to the evolution of nesting associations, discuss some possible implications for the populations involved and argue that nesting associations provide many novel research opportunities.
Sequential habitat occupation and productivity of Ospreys Pandion haliaetus were studied in the recovering Estonian population from 1985 to 1999. During this period, the number of known nests increased from five to 32. Nest-sites closer to the foraging grounds and with more lakes nearby were occupied first and had the highest productivity. Through a reduction in the quality of sites available, the average productivity of Ospreys decreased as their numbers rose, consistent with despotic distribution models. The sites occupied first during the recolonization were also those that had been the last to be abandoned during the population's decline prior to 1980. However, newcomers preferred sites near established pairs. Therefore, conspecific attraction explained some stochasticity left unexplained by deterministic resource models.
Patch use theory and the marginal value theorem predict that a foraging patch should be abandoned when the costs and benefits of foraging in the patch are equal. This has generally been interpreted as all patches being abandoned when their instantaneous intake rate equals the foraging costs. Bayesian foraging – patch departure is based on a prior estimate of patch qualities and sampling information from the current patch – predicts that instantaneous quitting harvest rates sometimes are not constant across patches but increase with search time in the patch. That is, correct Bayesian foraging theory has appeared incompatible with the widely accepted cost–benefit theories of foraging. In this paper we reconcile Bayesian foraging with cost–benefit theories. The general solution is that a patch should be left not when instantaneous quitting harvest rate reaches a constant level, but when potential quitting harvest rate does. That is, the forager should base its decision on the value now and in the future until the patch is left. We define the difference between potential and instantaneous quitting harvest rates as the foraging benefit of information, FBI. For clumped prey the FBI is positive, and by including this additional benefit of patch harvest the forager is able to reduce its penalty of ignorance.
1. Understanding how density-dependent and independent processes influence demographic parameters, and hence regulate population size, is fundamental within population ecology. We investigated density dependence in growth rate and fecundity in a recovering population of a semicolonial raptor, the osprey Pandion haliaetus [Linnaeus, 1758], using 31 years of count and demographic data in Corsica. 2. The study population increased from three pairs in 1974 to an average of 22 pairs in the late 1990s, with two distinct phases during the recovery (increase followed by stability) and contrasted trends in breeding parameters in each phase. 3. We show density dependence in population growth rate in the second phase, indicating that the stabilized population was regulated. We also show density dependence in productivity (fledging success between years and hatching success within years). 4. Using long-term data on behavioural interactions at nest sites, and on diet and fish provisioning rate, we evaluated two possible mechanisms of density dependence in productivity, food depletion and behavioural interference. 5. As density increased, both provisioning rate and the size of prey increased, contrary to predictions of a food-depletion mechanism. In the time series, a reduction in fledging success coincided with an increase in the number of non-breeders. Hatching success decreased with increasing local density and frequency of interactions with conspecifics, suggesting that behavioural interference was influencing hatching success. 6. Our study shows that, taking into account the role of non-breeders, in particular in species or populations where there are many floaters and where competition for nest sites is intense, can improve our understanding of density-dependent processes and help conservation actions.
Regulation of Osprey Pandion haliaetus populations: the role of nest site availability
- A F Poole
Poole, A.F. 1989b. Regulation of Osprey Pandion haliaetus populations: the role of nest site availability. In Meyburg, B.-U. & Chancellor, R.D. (eds) Raptors in the Modern World: 227–234.
The status and breeding biology of Ospreys in Hokkaido
- A Shoji
- A Sugiyma
- M A Brazil
Shoji, A., Sugiyma, A. & Brazil, M.A. 2011. The status and breeding biology of Ospreys in Hokkaido, Japan. Condor 113: 762–767.
The Osprey Pandion haliaetus on the Portuguese coast: past, present and recovery potential
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Palma, L. 2001. The Osprey Pandion haliaetus on the Portuguese coast: past, present and recovery potential. Vogelwelt 122: 179–190.
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Instituto Canario de Estadística.Gobierno de Canarias
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