Beneharo Rodríguez

High prevalence of parental delivery of plastic debris in Cory's shearwaters (Calonectris diomedea)

Plastic ingestion by adult Procellariiformes has been widely recorded, but few studies have evaluated intergenerational transfer. We assessed the prevalence of plastic particles, as well as their basic characteristics, in the gut content of dead Corys shearwater fledglings stranded by light pollution on Canary Islands. Eighty-three percent of birds were affected, containing on average 8.0 plastic pieces per bird. The average plastic weight per bird was low (2.97±3.97mg) compared with other petrel species. We found no relationships between plastic loads and body condition or body size, but negative effects may be hidden or delayed. We propose to use the fledglings stranded by light pollution to carry out more precise studies to understand the potential hidden costs of plastic ingestion; and to monitor in a long-term the marine debris to develop management actions for the control of pollution at the marine environment.

Causes of Raptor Admissions to a Wildlife Rehabilitation Center in Tenerife (Canary Islands)

Abstract 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.

Temporal and Spatial Variation in the Diet of the Endemic Lizard Gallotia galloti in an Insular Mediterranean Scrubland

Abstract We analyzed 621 lizard fecal pellets to assess the diet of the endemic lizard Gallotia galloti (Lacertidae) throughout one year in the thermophilous scrubland, the most threatened habitat in the Canary Islands. Indicating the importance of frugivory, 98.1% of pellets contained seeds from fleshy-fruited plant species (8,028 seeds in total), and the fruit volume reached 47.5%. The Canarian endemic plants Rhamnus crenulata and Canarina canariensis were most important in frequency of occurrence and number of seeds found in pellets, respectively. Lizards were more frugivorous during the summer (63.0% of volume), and seasonal variation was associated with temporal changes in availability of ripe fleshy fruits. We detected microspatial differences in the consumption of fruits and plant material. Significant correlations were found between plant cover of each species and their respective consumption by lizards. Lizards consumed invertebrates throughout the year; Formicidae, Hemiptera, Coleoptera, and Hymenoptera were the most frequently consumed prey (76.5% of the animal prey items). Our results indicate that G. galloti is one of the most frugivorous lacertids studied. The high number of undamaged seeds removed by these lizards also implies an important role in the seed dispersal processes of many fleshy-fruited plant species from this threatened habitat.

GPS tracking for mapping seabird mortality induced by light pollution

Light pollution and its consequences on ecosystems are increasing worldwide. Knowledge on the threshold levels of light pollution at which significant ecological impacts emerge and the size of dark refuges to maintain natural nocturnal processes is crucial to mitigate its negative consequences. Seabird fledglings are attracted by artificial lights when they leave their nest at night, causing high mortality. We used GPS data-loggers to track the flights of Cory’s shearwater Calonectris diomedea fledglings from nest-burrows to ground, and to evaluate the light pollution levels of overflown areas on Tenerife, Canary Islands, using nocturnal, high-resolution satellite imagery. Birds were grounded at locations closer than 16 km from colonies in their maiden flights, and 50% were rescued within a 3 km radius from the nest-site. Most birds left the nests in the first three hours after sunset. Rescue locations showed radiance values greater than colonies, and flight distance was positively related to light pollution levels. Breeding habitat alteration by light pollution was more severe for inland colonies. We provide scientific-based information to manage dark refuges facilitating that fledglings from inland colonies reach the sea successfully. We also offer methodological approaches useful for other critically threatened petrel species grounded by light pollution.

Seabird mortality induced by land-based artificial lights

Artificial lights at night cause high mortality of seabirds, one of the most endangered groups of birds globally. Fledglings of burrow-nesting seabirds, and to a lesser extent adults, are attracted to and then grounded (i.e., forced to land) by lights when they fly at night. We reviewed the current state of knowledge of seabird attraction to light to identify information gaps and propose measures to address the problem. Although species in families such as Alcidae and Anatidae can be grounded by artificial light, the most affected seabirds are petrels and shearwaters (Procellariiformes). At least 56 species of Procellariiformes, more than one-third of them (24) threatened, are subject to grounding by lights. Seabirds grounded by lights have been found worldwide, mainly on oceanic islands but also at some continental locations. Petrel breeding grounds confined to formerly uninhabited islands are particularly at risk from light pollution due to tourism and urban sprawl. Where it is impractical to ban external lights, rescue programs of grounded birds offer the most immediate and employed mitigation to reduce the rate of light-induced mortality and save thousands of birds every year. These programs also provide useful information for seabird management. However, these data are typically fragmentary, biased, and uncertain and can lead to inaccurate impact estimates and poor understanding of the phenomenon of seabird attraction to lights. We believe the most urgently needed actions to mitigate and understand light-induced mortality of seabirds are estimation of mortality and effects on populations; determination of threshold light levels and safe distances from light sources; documentation of the fate of rescued birds; improvement of rescue campaigns, particularly in terms of increasing recovery rates and level of care; and research on seabird-friendly lights to reduce attraction.

Seasonal Diet of the Grey Heron Ardea cinerea on an Oceanic Island (Tenerife, Canary Islands): Indirect Interaction with Wild Seed Plants

Abstract. In 199 pellets analyzed a total of 7 460 prey items were counted, 96.2% of which were arthropods. Aeshnidae larvae (Odonata) made up 66.1% of the total prey items and were the main invertebrate group. Vertebrates constituted 3.8%, with reptiles and mammals being the main prey of this type (1.8% each). Despite the small size of the invertebrates, this group reached > 60% in terms of biomass. All the main prey items varied significantly among seasons. Odonata was the most important group in all seasons, reaching its maximum value in summer. In the case of vertebrates, reptiles were captured mainly in spring, mammals in winter. With regard to indirect interaction with seeds, a total of 901 seeds associated with lizard remains were found in 77 pellets, indicating that they had previously been consumed by these reptiles. External visual damage of seeds was low and only 1.1% was destroyed. No seeds germinated after the four-month germination experiment and practically all of them were unviable. In conclusion, these results indicate that Grey Heron diet on islands varies in comparison with continental zones, including an important number of invertebrates and reptiles. Furthermore, this bird acts as an opportunistic secondary seed disperser, although its ecological effect does not seem to be very significant for the dynamics of the Canary Island ecosystems.

Density, habitat selection and breeding success of an insular population of Barbary Falcon Falco peregrinus pelegrinoides

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.

Incidence of entanglements with marine debris by northern gannets (Morus bassanus) in the non-breeding grounds

The quantification of entanglements of megafauna with plastic debris at sea is difficult to assess for several reasons, such as detection and reporting biases. We used standardized vessel based counts to describe and quantify the occurrence of marine debris entanglements in northern gannets Morus bassanus at five of its main wintering areas. We observed 34 entangled birds in total, representing 0.93% of all gannets counted (n=3672 individuals). The incidence of entanglements largely varied geographically, being exceptionally high off Mauritania (20.2% of the birds in late spring). Most birds affected were immature (1.88% compared to 0.06% in adults), which in turn represented 52.4% of all the birds. Entanglements in the lower bill mandible were the most frequent, mainly with red-colored plastic objects. Further research is urgently needed to evaluate the impact of entanglements at the population level and its occurrence in other marine species, and to seek potential solutions.

Density, habitat selection and breeding biology of Common Buzzards Buteo buteo in an insular environment

Capsule Taller and sheltered cliffs located in rugged areas are selected for breeding and only some life history traits fit the predictions of the so‐called ‘insular’ syndrome. Aims To analyse the density and nesting habitat preferences of Buzzards on the island of Tenerife, and describe the life history traits of this population. Methods Density was studied by intensive field searching for all established pairs in a well‐defined area. Habitat features of breeding territories were compared with randomly selected sites using univariate and multivariate analysis (glm). Breeding biology was described based upon a total of 57 breeding attempts. Results Density was positively correlated with estimated surface of forested areas. The best model explaining characteristics of territory used for nesting reflected land ruggedness, nest shelter and distance to the nearest Barbary Falcon breeding site. Mean clutch size was 2.60 ± 0.82, productivity was 1.68 ± 0.97 and the percentage of successful pairs was 84.2%. Conclusions Buzzards mainly use cliffs to nest, especially taller and sheltered ones, located in rugged areas and in sympatry with Barbary Falcons. Characteristics of breeding territory did not predict productivity. All reproductive rates were similar to those reported for some continental populations except nesting success, which was higher.

Satellite tracking of Bulwer's Petrels Bulweria bulwerii in the Canary Islands

Capsule The breeding foraging and post-breeding dispersal movements of five satellite-tagged Bulwers Petrels from the Canary Islands were recorded. Foraging trips lasted 5.6 days in average (n = 3), while the mean distance covered was 1261 km, and foraging areas were located over the continental slope and the adjacent pelagic waters, around 1200–2000 m depth and up to 350 km from the colony. After the chick-rearing period, birds dispersed southwestwards to the tropical waters of the central Atlantic.