Cory's Shearwater Calonectris Research Articles

Colony attendance and moult pattern of Cory's Shearwaters (Calonectris borealis) differing in breeding status and age

Migratory birds must fit three costly life‐history events within the annual cycle, reproduction, moult and migration, to minimize their overlap and maximize survival and breeding success. However, some seabirds, such as Cory's Shearwater Calonectris borealis, overlap body moult and breeding, with flight feather renewal occurring in late chick‐rearing. In contrast, the moult patterns of non‐breeding adult (sabbatical) and immature Cory's Shearwaters, which also attend the colony during the breeding season, remain poorly understood. Furthermore, the potential implications of life‐stage and breeding status trade‐offs on moult status and colony attendance in non‐breeders has rarely been investigated. Surveying different areas within one colony between June and September 2013 and 2014, we studied the age and breeding status composition of birds attending the breeding colony and scored moult of their body (breast and upper‐neck), wing and tail feathers. We found that in addition to breeders (n = 165), 57.6% of the birds (n = 389) attending the colony were 4‐ to 10‐year‐old immatures (n = 132) and adult sabbatical shearwaters (n = 92). Sabbaticals and 8‐ to 10‐year‐old immatures (n = 28) were present at the colony during incubation, whereas only three sabbatical birds and no 8‐ to 10‐year‐old immatures were captured in late chick‐rearing. Conversely, 4‐ to 7‐year‐old immatures arrived later in the season but were still present in late chick‐rearing. Sabbatical and 8‐ to 10‐year‐old immatures were moulting body feathers at the same time as adult breeders, whereas, among 4‐ to 7‐year‐old immatures, older birds moulted earlier than younger birds. A larger proportion of sabbatical birds were replacing tail feathers compared with adult breeders. However, there was no evidence that sabbaticals or 8‐ to 10‐year‐old immatures differed in wing moult from adult breeders until August. Overall, our study shows that colony attendance by non‐breeding adults and immatures is widespread in this population. The synchronous moult schedule of flight and body feathers across age groups at different life‐history stages may suggest that this aspect of moult is controlled by environmental conditions.

Surveying Cory Shearwater colonies with camera traps and identifying potential invasive nest predators.

The Azores holds the largest population of Cory's shearwater Calonectrisborealis (Cory, 1881) (Aves, Procellariiformes, Procellariidae) in the world. One of the major threats of this species in the Azores is the predation by invasive mammals, which were introduced during European colonisation of the islands.The present study provides a dataset from a camera-trapping survey performed in colonies of Cory's shearwater. The sampling was conducted between 7 April and 23 October 2019, covering the entire breeding season, in three colonies of the Terceira Island (Azores). A total of 32 nests were sampled using motion-triggered cameras. The aims of this study are to provide information about the ecological patterns of the Cory shearwater and to identify potential nest predators. Our results include a total of 6972 records of 15 species (nine species of birds, five of mammals and one reptile), of which 5414 records are of Cory's shearwater, 478 of potential mammal predators and 1080 of another vertebrate species. Information about the biology of the species is also provided, as species circadian behaviour and habitat description.

Higher mercury contamination is associated with shorter telomeres in a long-lived seabird – A direct effect or a consequence of among-individual variation in phenotypic quality?

Mercury is a heavy metal, which is pervasive and persistent in the marine environment. It bioaccumulates within organisms and biomagnifies in the marine food chain. Due to its high toxicity, mercury contamination is a major concern for wildlife and human health. Telomere length is a biomarker of aging and health, because it predicts survival, making it a potential tool to investigate sublethal effects of mercury contamination. However, the relationship between telomeres and mercury contamination is unclear. We measured feather mercury concentration in Cory's Shearwaters Calonectris borealis, long-lived seabirds and top predators, between 9 and 35 years of age and related it to telomere length in erythrocytes. Cory's Shearwaters with higher mercury concentrations had shorter telomeres and the effect was sex-dependent, reaching significance in males only. This may be explained by the fact that males have longer telomeres and higher and more variable mercury concentrations than females in this population. The mercury effect on telomere length was stronger on longer telomeres in the genome within individuals. We discuss the hypotheses that the negative correlation could either be a direct effect of mercury on telomere shortening and/or a consequence of variation in phenotypic quality among individuals that results in a covariation between mercury contamination and telomere length.

Breeding of Cory's shearwaterCalonectris borealison Selvagem Grande and beneficial effects of removal of invasive mammals

AbstractThe largest colony of Cory's shearwaterCalonectris borealisnests on the island of Selvagem Grande in the north-eastern Atlantic. In 2002, a programme of eradication was conducted to remove two alien invasive mammals, the house mouseMus musculusand European rabbitOryctolagus cuniculus. Preliminary studies recorded beneficial effects of the eradications for a variety of plant and animal species, including Cory's shearwater. We recorded fledging rates of shearwaters for 1982–2001, prior to the eradication, and for 2002–2020, after the eradication, from two quadrats, each containing 134–329 nest sites. Although there was annual fluctuation in fledging rates in the quadrats, the mean rate of 40.74 ±SD 3.92 fledglings per 100 nest sites for the two quadrats combined prior to the eradication of mammals increased significantly, to 52.88 ± SD 5.03 per 100 nest sites, after the eradications. Because the two mammals were removed synchronously it is difficult to know which factors depressed fledging of Cory's shearwaters on Selvagem Grande. However, the predatory behaviour of house mice on other oceanic islands, and the fact that increased fledging was seen soon after the eradications occurred, suggest predation by house mice on shearwater hatchlings was the main cause of losses.

Breeding Success of Cory's Shearwater in Relation to Nest Characteristics and Predation by Alien Mammals

Procellariiformes are one of the most threatened groups of birds of the world so knowledge of nesting habitat and factors affecting breeding rates are vital issues for their conservation. Although Cory's Shearwater Calonectris borealis is a well-studied seabird species on the whole, information on the relationship between its breeding parameters and nest site characteristics is quite limited. To address this gap, during 2017-2019, we conducted a study on its breeding performance on Tenerife, the largest and the most densely populated island of the Canarian archipelago. We constructed generalized linear mixed models to evaluate the potential effects of nest features on breeding performance. Two variables explained breeding success: the distance from the nest to the nearest paved road, and the presence of pebbles at the entrance of the nest-burrow, which correlated negatively and positively with breeding success, respectively. The majority of failures occurred during the incubation period. Breeding failures were mainly related to egg abandonment and rat predation upon eggs or chicks. Effective measures mitigating human-instigated disturbance (e.g. control of dogs, rats and feral cat populations, and reducing light pollution), together with studies on factors affecting demographic parameters, are needed to guarantee the long-term conservation of Cory's Shearwater and other seabird species on the main Canary Islands.—Rodríguez, B., Siverio, F., Acosta, Y. & Rodríguez, A. (2022). Breeding success of Cory's Shearwater in relation to nest characteristics and predation by alien mammals. Ardeola, 69: 115-128.

Year-round element quantification of a wide-ranging seabird and their relationships with oxidative stress, trophic ecology, and foraging patterns

Multidisciplinary approaches are essential to diligently assess environmental health status of ecosystems. In this study, year-round chemical elements' exposure and impacts were assessed on the wide-ranging Cory's shearwater Calonectris borealis breeding in Berlenga Island, offshore Portugal, North Atlantic Ocean. The aim was to identify potential contamination and oxidative stress sources associated with trophic ecology, habitat and spatial use, and foraging patterns. A set of 20 chemical elements were quantified, along with oxidative stress biomarkers, stable isotope analyses, and GPS tracking data. Birds presented higher accumulation to some non-essential elements along the year (i.e. arsenic, As; cadmium, Cd; mercury, Hg; lead, Pb; and strontium, Sr), in which concentrations were similar or surpassed other procellariform seabird populations all over the world. No significant differences were found for any of the elements between different periods within the breeding season, with exception of Hg. However, a Principal Component Analysis taking into consideration a group of elements showed differences between pre-laying and chick-rearing periods, with overall higher concentrations in the former. Individuals spending more time engaging in an intensive search for food, and in more coastal environments, presented overall higher element concentrations, and particularly Hg. Contrary to expectations, no relationships were found between chemical elements and oxidative stress. On the other hand, spatial use and foraging patterns of Cory's shearwaters influenced their oxidative stress responses. Our results highlight the need for multidisciplinary approaches to deepen understanding of the large-scale vulnerability of bioindicators such as seabirds and, by extension, the overall environmental health of ecosystems in which they rely.

Absence of haemosporidian parasite infections in the long-lived Cory's shearwater: evidence from molecular analyses and review of the literature.

The apparent scarcity or absence of blood parasites in some avian groups, such as seabirds, has been related to intrinsic and extrinsic factors including host immunological capacity, host-parasite assemblage, and ecological parameters, but also to reduced sensitivity of some methods to detect low parasite prevalence/intensities of infection. Here, we examined the haemosporidian parasite prevalence in a breeding population of Cory's shearwater Calonectris diomedea borealis, a long-distance migrant seabird, nesting in the Macaronesian region, in the Eastern Atlantic. Previous studies on Calonectris diomedea complex were based on small sample sizes providing weak evidence for a lack of infections by haemoparasites. Here, we investigated the presence of both parasite infections in C. d. borealis and larvae of potential mosquito vectors on the area. By employing a PCR-based assay, we extensively examined the prevalence of blood parasites belonging to the genera Plasmodium, Haemoproteus, and Leucocytozoon in 286 individuals from different life stages (i.e., chicks, immatures, sabbatical, and breeding adults), facing their specific energetic trade-offs (immunological functions vs. life history activities). We sampled immatures and adult shearwaters, of different sexes, ages, and migratory origins, from two sub-colonies. None of the sampled individuals were infected by these parasites, supporting the hypothesis that there was no in situ or ex situ transmission of vector-borne parasites in marine habitats irrespective of host's life stage and in spite of the presence of the potential Plasmodium vector Culiseta longiareolata breeding in the area. These results suggest that the lack of transmission of haemosporidian parasites on Selvagem Grande may be related to the lack of suitable dipteran vectors at the study sites, which may result from the geographic isolation of this area.

Noteworthy seabird records from Paraná state, southern Brazil

We inventoried seabird specimens—skeletons and skins—collected during beach surveys of Parana, south Brazil, both the mainland coast and offshore islets during the period 1992–94. We found 184 specimens comprising four orders and 17 species. This represents the most important collection of seabirds from Parana and includes three new records for the state, Cory's Shearwater Calonectris borealis, Sooty Shearwater Puffinus griseus and Snowy Sheathbill Chionis albus. We recommend the removal of two species from the avifauna of Parana—Shy Albatross Thalassarche cauta and Broad-billed Prion Pachyptila vittata—due to the lack of tangible evidence. All of this material is held in publicly accessible natural history museums.

Sex and migratory strategy influence corticosterone levels in winter-grown feathers, with positive breeding effects in a migratory pelagic seabird.

To overcome unpredictable stressful transitory events, animals trigger an allostatic response involving the hypothalamic-pituitary-adrenal cortex. This hormonal response, which involves the release of glucocorticoids which in turn mediate between the main physiological mechanisms that regulate the energetic demands and resource allocation trade-off with behavioural responses to environmental perturbations and may ultimately lead to variation in fitness. We have used the Cory's shearwater Calonectris borealis, a sexually dimorphic pelagic seabird with a partial migratory strategy, as a model bird species to analyse a number of traits related to the stress response. We investigated whether the activation of a stressful response, mediated by corticosterone, during the wintering period (1) correlated with the previous breeding success, (2) was affected by the migratory behaviour of male birds and (3) had consequences in the fitness of the birds. Corticosterone levels in feathers grown overwinter were analysed in 61 adult birds during three consecutive migratory periods (2009-2012) and in 14 immature birds in the wintering period 2010-2011. Moreover, the levels of corticosterone were analysed in experimental birds which were freed from their reproductive duties and compared with control birds which raised fledglings to the end of the breeding period. The results show that the levels of corticosterone were sex dependent, differed between years and were affected by the migratory strategy performed by the birds. The activation of the stressful response over the wintering period generated residual carry-over effects that positively affected the reproductive output in the subsequent breeding stage, a phenomenon previously undescribed in a long-lived pelagic seabird. Our study provides evidence that the analysis of corticosterone from feathers is a useful tool to evaluate carry-over effects in birds far away from breeding sites, opening new possibilities for future studies in this field.

New species of the feather mite genus Promegninia Gaud & Atyeo (Acari: Avenzoariidae) from petrels and shearwaters (Procellariiformes: Procellariidae).

Two new species of the feather mite genus Promegninia Gaud & Atyeo, 1967 (Avenzoariidae: Bonnetellinae) are described from procellariids in the northeasterm Atlantic Ocean: Promegninia bulweriae n. sp. from the Bulwer's petrel Bulweria bulwerii (Jardine & Selby) and P. calonectris n. sp. from the Cory's shearwater Calonectris borealis (Cory) (Procellariiformes: Procellariidae). Males of P bulweriae n. sp. are most clearly distinguished from the other known species in the genus by having short legs III extending only to the level of lobar apices and short conical tarsi III with lanceolate ventral seta w; females of this species are characterised by the absence of additional sclerites at postero-lateral angles of the prodorsal shield. Males of P. calonectris differ from the other known species in having bidentate terminal lamellae on the lobar apices and the entire adanal shield; females of this species are distinguished by having well-developed pygidial shields and a hysteronotal shield encompassing the bases of setae c2. Sequence data of the mitochondrial cytochrome c oxidase subunit I gene fragment (COI) are also obtained for the new species. An updated diagnosis of Promegninia and a key to the known species are provided.

Unusual Mass Stranding of Atlantic Yellow-Nosed Albatross (Thalassarche chlororhynchos), Petrels and Shearwaters in Southern Brazil

Abstract. Mass strandings of seabirds occur frequently on many beaches worldwide and commonly involve penguins, petrels, shearwaters, and prions, among others. Large numbers of stranded albatrosses are rarely reported. In this paper, an unusual stranding event that involved five species of Procellariiformes, predominantly the Atlantic Yellow-nosed Albatross (Thalassarche chlororhynchos), is described in southern Brazil. Carcasses and debilitated specimens of Atlantic Yellow-nosed Albatrosses (n = 125), unidentified petrels/shearwaters (Procellariidae; n = 63), White-chinned Petrels (Procellaria aequinoctialis; n = 52), Great Shearwaters (Puffinus gravis; n = 11), Manx Shearwaters (Puffinus puffinus; n = 4) and Cory's Shearwater (Calonectris borealis; n = 1) were found stranded between 15 and 22 March 2013. Atlantic Yellow-nosed Albatrosses (n = 20) and White-chinned Petrel (n = 1) were found alive and remained in the rehabilitation center for a few days before being released. A total of at least 256 birds...

Spatial foraging segregation by close neighbours in a wide-ranging seabird.

Breeding seabirds are central-place foragers and therefore exploit food resources most intensively nearer their colonies. When nesting aggregations are close to one another density-dependent competition is likely to be high, potentially promoting foraging segregation (i.e. neighbouring colonies may segregate to search for food in different areas). However, little is known about spatial segregation in foraging behaviour between closely adjacent colonies, particularly in species that are wide-ranging foragers. Here, we tested for foraging segregation between two sub-colonies of a wide-ranging seabird, Cory's shearwater Calonectris borealis, separated by only 2 km, on a small Island in the North Atlantic. During the 2010 chick-rearing period, 43 breeding adults of both sexes were simultaneously sampled at both sub-colonies. A GPS logger was deployed on each individual and removed after several foraging trips at sea. Blood samples (plasma and red blood cells) were collected from each tracked individual for stable isotope analysis. Results indicated partial spatial segregation between the two sub-colonies during local foraging trips (i.e. those of ≤1 day duration and 216 km from the colony) accounting for 84.2% of all trips recorded. The location of the breeding sub-colony influenced the direction of travel of birds during local trips resulting in sub-colony-specific foraging areas. Although the oceanographic conditions associated with the foraging range of the two sub-colonies differed, no differences were found in the habitat exploited and in their estimated diets. This suggests that birds concentrated their feeding activity in patches of similar habitat and prey during the chick-rearing period.

Do Cory’s Shearwaters Calonectris borealis choose mates based on size?

Many bird species rely on visual cues for mate choice, including those provided by body size or by the size of a body appendage. Mate choice based on size may lead to size-assortative mating, which may in turn have consequences for reproductive performance. In this study, we examined whether body size influences mate choice decisions of Cory's Shearwater Calonectris borealis ,a seabird with nocturnal activity on land. We found evidence of negative assortative mating for bill morphology (nostril height and bill length), but found no assortative mating according to body mass, tarsus length, and wing length. In addition, we investigated the influence of negative assor- tative mating and individual body size-related traits on reproductive performance, i.e., laying date and breeding success. We found that laying date and breeding success were not correlated with the extent of assortative mating, i.e., the assortatively mating breeders did not lay earlier and were not more likely to breed successfully. However, we found that heavier females (body mass measured during pre-laying) laid later in the season. We discuss these results in the light of possible effects of acoustic signals and for- aging strategies on the mating pattern. Furthermore, we suggest that some female attributes may be crucial for breeding success in Cory's Shearwaters.

Population Structure and Dispersal Patterns within and between Atlantic and Mediterranean Populations of a Large-Range Pelagic Seabird

Dispersal is critically linked to the demographic and evolutionary trajectories of populations, but in most seabird species it may be difficult to estimate. Using molecular tools, we explored population structure and the spatial dispersal pattern of a highly pelagic but philopatric seabird, the Cory's shearwater Calonectris diomedea. Microsatellite fragments were analysed from samples collected across almost the entire breeding range of the species. To help disentangle the taxonomic status of the two subspecies described, the Atlantic form C. d. borealis and the Mediterranean form C. d. diomedea, we analysed genetic divergence between subspecies and quantified both historical and recent migration rates between the Mediterranean and Atlantic basins. We also searched for evidence of isolation by distance (IBD) and addressed spatial patterns of gene flow. We found a low genetic structure in the Mediterranean basin. Conversely, strong genetic differentiation appeared in the Atlantic basin. Even if the species was mostly philopatric (97%), results suggest recent dispersal between basins, especially from the Atlantic to the Mediterranean (aprox. 10% of migrants/generation across the last two generations). Long-term gene flow analyses also suggested an historical exchange between basins (about 70 breeders/generation). Spatial analysis of genetic variation indicates that distance is not the main factor in shaping genetic structure in this species. Given our results we recommend gathering more data before concluded whether these taxa should be treated as two species or subspecies.

Carry‐over effects from breeding modulate the annual cycle of a long‐distance migrant: an experimental demonstration

Carry-over effects relate to events or processes that influence individual performance in a subsequent season, but their occurrence in the annual cycle of migratory avian taxa is seldom studied. We investigated if different levels of resource allocation to reproduction may result in carry-over effects that change the timing and destination of long-distance migration. We reduced the parental investment of Cory's Shearwaters Calonectris diomedea by removing their chick at an early stage. When compared to individuals with greater parental investment (controls that raised chicks to close to fledging), manipulated birds started most stages of migration sooner and returned to the colony earlier at the start of the following breeding season. Late arrival in the subsequent nesting season increased the probability of skipping a breeding year. Manipulated males were less likely to engage in long-distance migration, which supports the idea that partial migration is condition dependent. Our study demonstrates experimentally that energetic or time-dependent costs of reproduction may have an enduring impact on migration schedule and on nonbreeding geographical distribution of long-distance migrants, which may also influence the ability to breed in the following season.

Diurnal seabird movements at Cabo Carvoeiro (Peniche, Portugal): observations in early October 2012

The ecology and movements of seabirds are still inadequately understood, mainly because they can rarely be studied efficiently from land. The potential of Cabo Carvoeiro (Peniche, Portugal) for monitoring seabird movements from land is poorly known internationally, as few results from this site have been published in English. Here we present data from standardised counts in October 2012 and draw attention to recent organised seabird counts in Portugal. Despite unfavourable weather conditions for concentrating seabirds towards land, we observed a strong passage of Northern Gannet Morus bassanus, Cory's Shearwater Calonectris diomedea, Great Skua Stercorarius skua, and Balearic Shearwater Puffinus mauretanicus (mean morning passage of 252, 99, 19, and 21 birds / hour, respectively). Manx Shearwater Puffinus puffinus, Sooty Shearwater P. griseus and Great Shearwater P. gravis occurred regularly in low numbers. Extrapolation indicates that thousands of seabirds passed daily within a few kilometres from land. The high counts of some species and the fairly high species diversity observed by us and in the RAM (Rede de observação de Aves e Mamiferos marinhos) initiative show that Cabo Carvoeiro is an outstanding site for monitoring and studying seabirds in the eastern Atlantic, as it is also located further south in the flyway than most other seawatch points. We hope this note will inspire ornithologists from other countries to participate in standardised seabird counts at Cabo Carvoeiro and other Portuguese sites.

Do Seabirds Differ from Other Migrants in Their Travel Arrangements? On Route Strategies of Cory’s Shearwater during Its Trans-Equatorial Journey

Long-distance migrants have developed diverse strategies to deal with the challenges imposed by their annual journeys. These are relatively well studied in some avian groups, such as passerines, shorebirds and raptors. In contrast, few studies have addressed the migratory behaviour of pelagic birds in the light of current theories of optimal migration. Using a dataset of 100 complete migratory tracks gathered along four years, we performed a detailed study on the migratory strategy of a pelagic trans-equatorial migrant, the Cory’s shearwater Calonectris diomedea. We analysed daily routines, stopover ecology and travel speed, as well as the influence of the moon on several behavioural patterns. Cory’s shearwaters adopted a “fly-and-forage” strategy when migrating, similarly to what has been observed in some raptors. However, by flying by dynamic soaring, shearwaters attained high overall migration speeds, and were able to travel thousands of kilometres without making major stopovers and, apparently, without a noticeable pre-migratory fattening period. Other major findings of this study include the ability to adapt daily schedules when crossing major ecological barriers, and the constant adjustment of migration speed implying higher rates of travel in the pre-breeding movement, with a final sprint to the nesting colony. The present study also highlights a preference of Cory’s shearwaters for starting travel at twilight and documents a strong relationship between their migratory activity and the moon phase.

Contrasting effects of climatic variability on the demography of a trans‐equatorial migratory seabird

Large-scale seasonal climatic indices, such as the North Atlantic Oscillation (NAO) index or the Southern Oscillation Index (SOI), account for major variations in weather and climate around the world and may influence population dynamics in many organisms. However, assessing the extent of climate impacts on species and their life-history traits requires reliable quantitative statistical approaches. We used a new analytical tool in mark-recapture, the multi-event modelling, to simultaneously assess the influence of climatic variation on multiple demographic parameters (i.e. adult survival, transient probability, reproductive skipping and nest dispersal) at two Mediterranean colonies of the Cory's shearwater Calonectris diomedea, a trans-equatorial migratory long-lived seabird. We also analysed the impact of climate in the breeding success at the two colonies. We found a clear temporal variation of survival for Cory's shearwaters, strongly associated to the large-scale SOI especially in one of the colonies (up to 66% of variance explained). Atlantic hurricane season is modulated by the SOI and coincides with shearwater migration to their wintering areas, directly affecting survival probabilities. However, the SOI was a better predictor of survival probabilities than the frequency of hurricanes; thus, we cannot discard an indirect additive effect of SOI via food availability. Accordingly, the proportion of transients was also correlated with SOI values, indicating higher costs of first reproduction (resulting in either mortality or permanent dispersal) when bad environmental conditions occurred during winter before reproduction. Breeding success was also affected by climatic factors, the NAO explaining c. 41% of variance, probably as a result of its effect in the timing of peak abundance of squid and small pelagics, the main prey for shearwaters. No climatic effect was found either on reproductive skipping or on nest dispersal. Contrarily to what we expect for a long-lived organism, large-scale climatic indexes had a more pronounced effect on survival and transient probabilities than on less sensitive fitness parameters such reproductive skipping or nest dispersal probabilities. The potential increase in hurricane frequency because of global warming may interact with other global change agents (such as incidental bycatch and predation by alien species) nowadays impacting shearwaters, affecting future viability of populations.

Factors affecting mortality of shearwaters stranded by light pollution

AbstractEvery year and across the world, thousands of fledglings of different petrel species crash into human structures because they are disorientated by artificial lights during their first flights. As this phenomenon is rather predictable, rescue campaigns are organized to help birds to reach the ocean, but unfortunately, a low proportion gets hurt or dies. Despite the huge number of affected individuals, and the fact that the problem was detected a long time ago, little is known on this source of mortality. We have studied the factors (i.e. body condition, plumage development, fledging date and sex) influencing the mortality of Cory's Shearwater Calonectris diomedea fledglings stranded inland due to light pollution in Tenerife (Canary Islands) during two consecutive breeding seasons (2009 and 2010). Late fledglings showed lower values of a body condition index than early ones. No sex biases were detected, neither considering stranded birds overall, nor for recovery dates or in the body condition of rescued fledglings. Our results indicate that late birds stranded by lights showing abundant down are more susceptible to fatal collisions and that the lights do not selectively kill birds with lower body condition indices. An enhancement of veterinary care should be done during the last part of the fledging period when more fatal collisions occur, especially focused on fledglings with abundant down. More research to determine why some individuals end up disoriented around artificial lights and others do not is urgently needed to minimize or prevent fallouts.

First description of post-fledging migration of Maltese Cory's Shearwaters Calonectris diomedea diomedea

Three juvenile Cory's Shearwaters Calonectris diomedea diomedea were fitted with back-mounted satellite tags and tracked during post-fledging migration. The birds spent several weeks in the central Mediterranean before migrating westwards. Two tags stopped transmitting after 21 and 35 days; the third bird passed through the Strait of Gibraltar and along the West African coast until transmitting ceased after day 43, by which time it was 114.6 km off the coast and 4,390 km from Malta. Cory's Shearwaters from other Mediterranean islands winter further south in equatorial waters, in the eastern South Atlantic or in the northeast tropical Atlantic associated with the Canary current, and further research is needed to define the wintering areas of Maltese Cory's Shearwaters.