Vitor H. Paiva

The interaction between reproductive cost and individual quality is mediated by oceanic conditions in a long‐lived bird

Environmental variability, costs of reproduction, and heterogeneity in individual quality are three important sources of the temporal and interindividual variations in vital rates of wild populations. Based on an 18-year monitoring of an endangered, recently described, long-lived seabird, Monteiros Storm-Petrel (Oceanodroma monteiroi), we designed multistate survival models to separate the effects of the reproductive cost (breeders vs. nonbreeders) and individual quality (successful vs. unsuccessful breeders) in relation to temporally variable demographic and oceanographic properties. The analysis revealed a gradient of individual quality from nonbreeders, to unsuccessful breeders, to successful breeders. The survival rates of unsuccessful breeders (0.90 +/- 0.023, mean +/- SE) tended to decrease in years of high average breeding success and were more sensitive to oceanographic variation than those of both (high-quality) successful breeders (0.97 +/- 0.015) and (low-quality) nonbreeders (0.83 +/- 0.028). Overall, our results indicate that reproductive costs act on individuals of intermediate quality and are mediated by environmental harshness.

Influence of environmental factors and energetic value of food on Little Tern Sterna albifrons chick growth and food delivery

Capsule Chick diet and early growth parameters differed between birds breeding on natural (sandy beaches) and alternative (salinas) habitats. Aims To describe diet and growth of Little Tern chicks, to examine the influence of tide and wind speed on food delivered to chicks in southern Portugal, and to determine whether diet and early chick growth parameters differed between birds breeding in natural (sandy beaches) and man-made alternative (salinas) habitats. Methods Nests were marked and visited regularly. Chicks were ringed and weighed at hatching. Between 12 and 14 nests were enclosed by a fence in order to measure and weigh chicks every day. Prey items delivered to fenced chicks were observed daily from hides, in different tidal periods and wind speed conditions. Prey items dropped in the colonies were collected. Foraging efficiency of adults was evaluated in relation to tide and wind speed. Fresh prey items were collected to determine their energetic content using a calorimeter. Results A chicks grew faster than B chicks, but both attained the same weight, tarsus-length and wing-length at 19 days old; C chicks attained the same values at day 21. There were significant differences in early growth parameters. A and B chicks grew faster on sandy beaches than on salinas. The main prey items were Atherina spp., Fundulus sp. and shrimps in salinas and Sardina pilchardus, Atherina spp. and Belone belone on sandy beaches. There was no correlation between ingestion rate and chick age, but mean length of prey ingested by chicks increased significantly with age. Conclusion Tide and wind speed influenced both size and type of prey delivered to chicks. Parents met the increasing energy demands of the growing chicks by adjusting prey size rather than prey delivery frequency. Differences in chick growth between salinas and sandy beaches could be related to both parental quality and diet. The presence of a high energy-content euryhaline fish species in the salinas, together with more sheltered conditions and no tidal influences, may be important in explaining the use of salinas by Little Terns.

Pelagic seabird flight patterns are consistent with a reliance on olfactory maps for oceanic navigation

Homing studies have provided tantalizing evidence that the remarkable ability of shearwaters (Procellariiformes) to pinpoint their breeding colony after crossing vast expanses of featureless open ocean can be attributed to their assembling cognitive maps of wind-borne odours but crucially, it has not been tested whether olfactory cues are actually used as a system for navigation. Obtaining statistically important samples of wild birds for use in experimental approaches is, however, impossible because of invasive sensory manipulation. Using an innovative non-invasive approach, we provide strong evidence that shearwaters rely on olfactory cues for oceanic navigation. We tested for compliance with olfactory-cued navigation in the flight patterns of 210 shearwaters of three species (Corys shearwaters, Calonectris borealis, North Atlantic Ocean, Scopolis shearwaters, C. diomedea Mediterranean Sea, and Cape Verde shearwaters, C. edwardsii, Central Atlantic Ocean) tagged with high-resolution GPS loggers during both incubation and chick rearing. We found that most (69%) birds displayed exponentially truncated scale-free (Lévy-flight like) displacements, which we show are consistent with olfactory-cued navigation in the presence of atmospheric turbulence. Our analysis provides the strongest evidence yet for cognitive odour map navigation in wild birds. Thus, we may reconcile two highly disputed questions in movement ecology, by mechanistically connecting Lévy displacements and olfactory navigation. Our approach can be applied to any species which can be tracked at sufficient spatial resolution, using a GPS logger.

Terrestrial and Marine Foraging Strategies of an Opportunistic Seabird Species Breeding in the Wadden Sea

Lesser black-backed gulls Larus fuscus are considered to be mainly pelagic. We assessed the importance of different landscape elements (open sea, tidal flats and inland) by comparing marine and terrestrial foraging behaviours in lesser black-backed gulls breeding along the coast of the southern North Sea. We attached GPS data loggers to eight incubating birds and collected information on diet and habitat use. The loggers recorded data for 10–19 days to allow flight-path reconstruction. Lesser black-backed gulls foraged in both offshore and inland areas, but rarely on tidal flats. Targets and directions were similar among all eight individuals. Foraging trips (n = 108) lasted 0.5–26.4 h (mean 8.7 h), and ranges varied from 3.0–79.9 km (mean 30.9 km). The total distance travelled per foraging trip ranged from 7.5–333.6 km (mean 97.9 km). Trips out to sea were significantly more variable in all parameters than inland trips. Presence in inland areas was closely associated with daylight, whereas trips to sea occurred at day and night, but mostly at night. The most common items in pellets were grass (48%), insects (38%), fish (28%), litter (26%) and earthworms (20%). There was a significant relationship between the carbon and nitrogen isotope signals in blood and the proportional time each individual spent foraging at sea/land. On land, gulls preferentially foraged on bare ground, with significantly higher use of potato fields and significantly less use of grassland. The flight patterns of lesser black-backed gulls at sea overlapped with fishing-vessel distribution, including small beam trawlers fishing for shrimps in coastal waters close to the colony and large beam-trawlers fishing for flatfish at greater distances. Our data show that individuals made intensive use of the anthropogenic landscape and seascape, indicating that lesser black-backed gulls are not a predominantly marine species during the incubation period.

INTERCOLONY AND ANNUAL DIFFERENCES IN THE DIET AND FEEDING ECOLOGY OF LITTLE TERN ADULTS AND CHICKS IN PORTUGAL

Abstract We used pellets and prey dropped near nests to study the diet and feeding ecology of Little Tern (Sterna albifrons) adults and chicks in northern and southern Portugal during 2000–2004. We compared diets among study areas, years, and birds breeding in two main habitat types: sandy beaches and salinas (man-made salt-pans). We also sampled prey fish in one study area and used published data from another area to examine whether the diet of Little Tern adults and chicks corresponded with the abundance of prey found in primary foraging habitats. Adult Little Terns fed mainly on sand-smelts (Atherina spp.) and gobies (Pomatoschistus spp.), which were the most abundant fish species in our estuarine and lagoon study areas. Despite some differences among colonies we did not find clear differences in adult diets among study areas and habitat types. Little Tern chicks also ate primarily Atherina spp., but their diet was more diverse than that of the adults, and characterized by a significantly higher proportion of prey with a high energetic value such as sardines (Sardina pilchardus), garfish (Belone belone), and killifish (Fundulus spp.). Chick diets differed significantly between habitat types, which may be a consequence of the limited foraging range of adult breeding birds. Both adult and chick diets matched the abundance of the main prey in our study areas, confirming the opportunistic foraging character of this species. We suggest that annual variation in prey availability may be the most important factor explaining annual variation in adult diets.

Global spatial ecology of three closely-related gadfly petrels

The conservation status and taxonomy of the three gadfly petrels that breed in Macaronesia is still discussed partly due to the scarce information on their spatial ecology. Using geolocator and capture-mark-recapture data, we examined phenology, natal philopatry and breeding-site fidelity, year-round distribution, habitat usage and at-sea activity of the three closely-related gadfly petrels that breed in Macaronesia: Zino’s petrel Pterodroma madeira, Desertas petrel P. deserta and Cape Verde petrel P. feae. All P. feae remained around the breeding area during their non-breeding season, whereas P. madeira and P. deserta dispersed far from their colony, migrating either to the Cape Verde region, further south to equatorial waters in the central Atlantic, or to the Brazil Current. The three taxa displayed a clear allochrony in timing of breeding. Habitat modelling and at-sea activity patterns highlighted similar environmental preferences and foraging behaviours of the three taxa. Finally, no chick or adult was recaptured away from its natal site and survival estimates were relatively high at all study sites, indicating strong philopatry and breeding-site fidelity for the three taxa. The combination of high philopatry, marked breeding asynchrony and substantial spatio-temporal segregation of their year-round distribution suggest very limited gene flow among the three taxa.

Nest fidelity is driven by multi-scale information in a long-lived seabird

Although the reproductive success of most organisms depends on factors acting at several spatial scales, little is known about how organisms are able to synthesize multi-scale information to optimize reproduction. Using longitudinal data from a long-lived seabird, Monteiros storm-petrel, we show that average breeding success is strongly related to oceanic conditions at the population level, and we postulate that (i) individuals use proximal information (their own reproduction outcome in year t) to assess the qualities of their mate and nest and to decide to retain them or not in year t + 1; (ii) the intensity of these responses depends on the quality of the oceanic environment in year t, which affects the predictability of reproduction outcome in year t + 1. Our results confirm that mate and nest fidelities are higher following successful reproduction and that the relationship between the success of a given pair and subsequent nest fidelity is stronger in years with unfavourable oceanic conditions, suggesting that individuals rely on distant information to modulate their use of proximal information and adjust their breeding strategy.

Colony Foundation in an Oceanic Seabird

Seabirds are colonial vertebrates that despite their great potential for long-range dispersal and colonization are reluctant to establish in novel locations, often recruiting close to their natal colony. The foundation of colonies is therefore a rare event in most seabird species and little is known about the colonization process in this group. The Cory’s shearwater (Calonectris diomedea) is a pelagic seabird that has recently established three new colonies in Galicia (NE Atlantic) thus expanding its distribution range 500 km northwards. This study aimed to describe the establishment and early progress of the new Galician populations and to determine the genetic and morphometric characteristics of the individuals participating in these foundation events. Using 10 microsatellite loci, we tested the predictions supported by different seabird colonization models. Possibly three groups of non-breeders, adding up to around 200 birds, started visiting the Galician colonies in the mid 2000’s and some of them eventually laid eggs and reproduced, thus establishing new breeding colonies. The Galician populations showed a high genetic diversity and a frequency of private alleles similar to or even higher than some of the large historical populations. Most individuals were assigned to several Atlantic populations and a few (if any) to Mediterranean colonies. Our study suggests that a large and admixed population is settling in Galicia, in agreement with predictions from island metapopulation models of colonization. Multiple source colonies imply that some birds colonizing Galicia were dispersing from very distant colonies (> 1500 km). Long-distance colonizations undertaken by relatively large and admixed groups of colonizers can help to explain the low levels of genetic structure over vast areas that are characteristic of most oceanic seabird species.

Projected distributions of Southern Ocean albatrosses, petrels and fisheries as a consequence of climatic change

Given the major ongoing influence of environmental change on the oceans, there is a need to understand and predict the future distributions of marine species in order to plan appropriate mitigation to conserve vulnerable species and ecosystems. In this study we use tracking data from seven large seabird species of the Southern Ocean (Black-browed Albatross Thalassarche melanophris, Grey-headed Albatross T. chrysostoma, Northern Giant Petrel Macronectes halli, Southern Giant Petrel M. giganteus, Tristan Albatross Diomedea dabbenena Wandering Albatross D. exulans and White-chinned Petrel Procellaria aequinoctialis , and on fishing effort in two types of fisheries (characterised by low or high-bycatch rates), to model the associations with environmental variables (bathymetry, chlorophyll-a concentration, sea surface temperature and wind speed) through ensemble Species Distribution Models. We then project these distributions according to four climate change scenarios built by the Intergovernmental Panel for Climate Change for 2050 and 2100. The resulting projections were consistent across scenarios, indicating that there is a strong likelihood of poleward shifts in distribution of seabirds, and several range contractions (resulting from a shift in the northern, but no change in the southern limit of the range in four species). Current trends for southerly shifts in fisheries distributions are also set to continue under these climate change scenarios at least until 2100; some of these may reflect habitat loss for target species that are already over-fished. It is of particular concern that a shift in the distribution of several highly threatened seabird species would increase their overlap with fisheries where there is a high-bycatch risk. Under such scenarios, the associated shifts in distribution of seabirds and increases in bycatch risk will require much-improved fisheries management in these sensitive areas to minimise impacts on populations in decline. This article is protected by copyright. All rights reserved.

Environmentally driven sexual segregation in a marine top predator

Sexual segregation in foraging occurs in many animal species, resulting in the partitioning of resources and reduction of competition between males and females, yet the patterns and drivers of such segregation are still poorly understood. We studied the foraging movements (GPS-tracking), habitat use (habitat modelling) and trophic ecology (stable isotope analysis) of female and male Cory’s shearwaters Calonectris borealis during the mid chick-rearing period of six consecutive breeding seasons (2010–2015). We found a clear sexual segregation in foraging in years of greater environmental stochasticity, likely years of lower food availability. When food became scarce, females undertook much longer foraging trips, exploited more homogeneous water masses, had a larger isotopic niche, fed on lower trophic level prey and exhibited a lower body condition, when compared to males. Sexual competition for trophic resources may be stronger when environmental conditions are poor. A greater foraging success of one sex may result in differential body condition of pair mates when enduring parental effort, and ultimately, in an increased probability of breeding failure.