Future breeding and foraging sites of a southern edge population of the locally endangered Black Guillemot Cepphus grylle

Capsule: One of the southernmost populations of the Black Guillemot Cepphus grylle is currently endangered, and the risk may be exacerbated by climate change.

Aims: We evaluated the future vulnerability of the Black Guillemot by predicting the impact of climate change on the geographic distribution of its breeding and foraging range in the Baltic Sea.

Methods: We used MaxEnt, a species distribution modelling technique, to predict the current and future breeding grounds and foraging sites.

Results: We found that although the foraging range is expected to increase in the southern Baltic Sea in future, these areas will no longer be suitable as breeding grounds due to a changing climate, creating a spatial mismatch.

Conclusion: Our predictions indicate where threats to the species may be most severe and can be used to guide conservation planning. We advocate conservation measures which integrate potential future threats and focus on breeding sites across the current and future potential geographic range of the Black Guillemot.     

Colony attendance and censusing of Black Guillemots Cepphus grylle in Shetland

The diurnal rhythm of colony attendance by Black Guillemots varied seasonally. No tidal effects were detected but in April attendance was lower when winds exceeded force 4. Numbers were most stable during 05.00–08.00 GMT in the pre-breeding period. Counts at this time and in winds of force 4 or less provide the best estimate of adult populations. Between late March and mid-May, counts of adults associated with breeding habitat account for most birds occupying suitable nest sites and censuses in northern Britain should be conducted in this period. As the proportion of non-breeding adults varies between colonies, no universal correction factor can be used to estimate the number of breeding attempts from counts of birds. Counts aimed at detecting maximum attendance provide greater accuracy than single counts made by flushing all birds on to the sea but take longer. Monitoring units should be stretches o-f coastline that include a number of colonies of different sizes.     

Earlier laying by Black Guillemots Cepphus grylle in Northern Ireland in response to increasing sea-surface temperature

Capsule Breeding season becomes earlier by 2.5 days for every 1°C increase in April sea-surface temperature.     

The ecology of Black Guillemot Cepphus grylle grylle chicks in the Baltic Sea region: insights into their diet,survival, nest predation and moment of fledging

Capsule: The diet of Black Guillemot Cepphus grylle grylle chicks in the Baltic Sea region was dominated by Viviparous Eelpout Zoarces viviparus. Risk of nest predation by avian and mammalian predators was perceived to be low, and hatching and fledging success were high.

Aims: To gain insight into the ecology of nestling Black Guillemots in the Baltic Sea region to fill knowledge gaps and benefit its conservation.

Methods: Two island groups in the Baltic Sea were visited several times during the breeding season of 2014 and 2015 to monitor nestling survival and fledging. In addition, camera traps were used in 2014 to monitor prey brought to chicks by adults and record possible nest predation events.

Results: Hatching success was 0.89 and 0.73 in 2014 and 2015, respectively, and fledging success was very high (0.95 and 0.97). No incidences of avian or mammalian predation were observed. Chicks fledged at night between 32 and 38 days after hatching. Viviparous Eelpout made up 95% of the prey items brought to the chicks by adults.

Conclusions: The hatching rate and fledging rate of the Black Guillemot was high in our study region. Juveniles seemed highly dependent on the availability of eelpout. Changes in the abundance of this species may therefore have negative effects on chick survival.     

The breeding biology of Black Guillemots Cepphus grylle in Shetland

The breeding biology of Black Guillemots Cepphus grylle was studied from 1982 to 1984 in Shetland, on islands lacking introduced mammalian predators. Adult survival (94%), clutch size (1.75-1.92) and breeding output (1.05-1.34 young fledged per breeding pair) were very high, indicating that conditions were relatively favourable on the islands studied. The timing of breeding varied significantly between years and was somewhat later than in other temperate parts of the range. In 1984 food was probably more readily available (possibly due to better weather conditions) in the pre-breeding period, which enabled more inexperienced birds to reach the condition threshold for breeding. It is likely that these birds tended to lay single-egg clutches in more open sites which were more susceptible to egg predation by crows. Nest-site quality and food availability were the key determinants of breeding productivity.     

Sexual differences in natal dispersal and philopatry of the grey-sided vole

The natal dispersal distance of the grey-sided vole,Clethrionomys rufocanus (Sundevall), was measured in a large outdoor enclosure (2.1 ha) in Hokkaido, Japan. Voles in about half of the enclosure (1 ha) were fed. Distance from the natal site to the site of reproduction was significantly greater in males (64.9 m) than in females (35.3 m). In males, 24.8% settled within one home range length of their natal site and 49.6% settled further than two range lengths from their natal site. In femles, the respective percentages were reversed: 51.2% and 22.0%. The timing of large movements (≥50 m) was related to body mass in both sexes. The population density was always higher on the fed grid than on the control grid, which resulted in the frequency of large movements being greater on the fed grid that on the control grid. Thus, the percentage of voles performing a large movement was not different between the grids in both sexes.     

Sex-biased dispersal and natal philopatry in the diamondback terrapin, Malaclemys terrapin

Nesting ecology and population studies indicate that diamondback terrapins (Malaclemys terrapin) exhibit nest site fidelity and high habitat fidelity. However, genetic studies indicate high levels of gene flow. Because dispersal affects the genetics and population dynamics of a species, we used six highly polymorphic microsatellite markers to investigate sex-biased dispersal and natal philopatry of M. terrapin in Barnegat Bay, NJ. We compared results of spatial autocorrelation analysis, assignment methods and Wright's F(ST) estimators to a mark-recapture analysis. Mark-recapture analysis over a 4-year period indicated that most individuals have relatively small home ranges (<2 km), with mature females displaying greater home ranges than males. Goodness of fit analysis of our mark-recapture study indicated that some juvenile males were likely transient individuals moving through our study location. Mean assignment indices and first-generation migrant tests indicated that mature males were more prone to disperse than mature females, but first-generation migrant tests indicated that per capita there are more female than male dispersers. Thus, the relative importance of males and females on gene flow in terrapin populations may change in relation to population sex ratios. Spatial autocorrelation analysis indicated that mature females exhibited natal philopatry to nesting beaches, but first-generation migrant tests indicated that a small number of females failed to nest on natal beaches. Finally, we discuss the important conservation implications of male-biased dispersal and natal philopatry in the diamondback terrapin.     

The diet of black guillemots Cepphus grylle in Shetland

The diet of black guillemots Cepphus grylle (L.) was studied in Shetland between 1982 and 1985, both during and outside the breeding season. Full-grown birds consumed a wide variety of fish and invertebrate species in summer, broadly reflecting the diversity of the inshore benthic fauna. In winter a greater diversity of invertebrates was taken, which assumed increased importance in the diet as the availability of benthic fish probably declined. Chicks were fed a diet of fish, with 70–80% being sandeels Ammodytes marinus and butterfish Pholis gunnellus on the island of Mousa. Sandeels were delivered more frequently in the early morning, coincident with a peak in their feeding activity. Older chicks were fed significantly longer fish. The composition of chick diet varied significantly with date, not chick age. A seasonal decline in the proportion of sandeels in the chick diet may have reflected changes in Zooplankton abundance, but the possibility that intensive industrial fishing of sandeels had adversely affected local stocks can not be ruled out.     

Kleptoparasitic interactions of Arctic Skuas Stercorarius parasiticus and Black Guillemots Cepphus grylle in northeastern Hudson Bay, Canada

Kleptoparasitic behaviour of Arctic Skuas was studied at a Black Guillemot colony in northeastern Hudson Bay, Canada. Skuas procured fish in 7-2% and 19-9% of attacks, and Black Guillemots lost fish in 7-2% and 21-2% of chases in 1982 and 1983, respectively. In 1983 chase outcome was related to distance between birds at the end of a chase and number of skuas in pursuit. The skuas' foraging efficiency (energy intake/energy expended during hunting) was estimated at 45 for 1982 and 5–8 for 1983, and total daily energy expenditure was estimated at 2–4 and 2-1 × b.m.r. for these years. Energetic calculations suggested that skuas obtained sufficient food to meet their daily needs in 3–6 h of hunting in 1982 and 2–7 h in 1983. The absence of intensive kleptoparasitic activity by breeding skuas in North America is attributed to the paucity of colonies suitable for both feeding (due to available host species and colony topography) and nesting (due to presence of arctic foxes and/or polar bears).     

Juvenile dispersal behaviour and natal philopatry of a long-lived raptor, the Spanish Imperial Eagle Aquila adalberti

The dispersal behaviour of 30 radio-tagged young Spanish Imperial Eagles Aquila adalberti was studied in southwestern Spain in 1986–1990. The dispersal process involved first departure from the natal population, exploratory movements, temporary settlements and returns to the natal population. The dispersal process lasted for the whole of the immature period studied, and behaviour was radically different from that displayed by territorial adults. Movements between temporary settling areas and the natal population occurred continually throughout the dispersal period. Return to the natal population could be used by the young to explore the possibilities for pair formation where a vacancy may have occurred in the breeding population.     

Extraordinary high natal philopatry in a migratory passerine

Natal dispersal is a key component of population dynamics in birds. It guarantees the genetic exchange of populations, favours range expansions and reduces intraspecific competition. In general, natal philopatry of migratory passerines is quite low (0–13.5%). In this study, we give evidence that, under specific conditions, migratory populations of passerine birds may show a considerably elevated natal philopatry. In a Linnet Carduelis cannabina population on the remote island of Helgoland in the North Sea, we found an extraordinary high return rate of yearlings (38%), which corresponds exactly to the annual survival rate of the species. Despite being completely migratory, the Linnets of Helgoland apparently return to a large extent to their native area and consequently might support the population maintenance on the island. Further studies are needed to reveal if this high natal philopatry is only an unusual 1-year event or a general characteristic of this partially isolated island population.     

Breeding site fidelity and natal philopatry in the Redshank Tringa totanus

This paper presents the results of a study carried out on breeding Redshank in the Ribble Marshes, Lancashire, England.
Redshank tend to return to the same breeding area year after year. There was no detectable sex bias in return rates. Experienced birds were more site faithful than inexperienced birds, with previously successful birds exhibiting the highest degree of breeding site fidelity. Older, more experienced birds were more successful at hatching eggs than inexperienced birds.
Breeding dispersal was the same both within and between years. Faithful pairs and males nesting with a new mate dispersed significantly shorter distances than females nesting with a new partner. Dispersal distances in female Redshank were affected by breeding success: unsuccessful females, nesting with a new mate, dispersed significantly farther than successful females. A pair's breeding success influenced the following year's mate fidelity. However, other factors such as overwintering survival and date of return may also have influenced mate fidelity.
Redshank were highly faithful to their natal area; a high proportion of birds that survived post-fledging mortality returned to breed in their area of birth. No sex bias in natal dispersal was detected. Approximately 50% of Redshank breed in their first year of life.     

Integrating across life-history stages: consequences of natal habitat effects on dispersal

Ecological and evolutionary processes are affected by forces acting at both local and regional scales, yet our understanding of how these scales interact has remained limited. These processes are fundamentally linked through individuals that develop as juveniles in one environment and then either remain in the natal habitat or disperse to new environments. Empirical studies in a diverse range of organisms have demonstrated that the conditions experienced in the natal habitat can have profound effects on the adult phenotype. This environmentally induced phenotypic variation can in turn affect the probability that an individual will disperse to a new environment and the ecological and evolutionary impact of that individual in the new environment. We synthesize the literature on this process and propose a framework for exploring the linkage between local developmental environment and dispersal. We then discuss the ecological and evolutionary implications of dispersal asymmetries generated by the effects of natal habitat conditions on individual phenotypes. Our review indicates that the influence of natal habitat conditions on adult phenotypes may be a highly general mechanism affecting the flow of individuals between populations. The wealth of information already gathered on how local conditions affect adult phenotype can and should be integrated into the study of dispersal as a critical force in ecology and evolution.     

Diving behaviour of Black Guillemots Cepphus grylle in the Pentland Firth,UK: potential for interactions with tidal stream energy developments

Capsule Black Guillemots Cepphus grylle were recorded diving in the Pentland Firth to an average depth of 32 metres and an overall maximal depth of 43 metres. The majority (88%) of dives were benthic with a median dive duration of 95 seconds, and a maximal dive duration of 131 seconds. The results provide empirical evidence that Black Guillemots use depths within the water column at which tidal turbines are likely to operate. Although limited, our data suggest the potential for interactions between Black Guillemots and marine renewable energy devices.     

Costs and benefits of female-biased natal philopatry in the common goldeneye

Sex-biased natal dispersal in long-lived species may resultin interactions between parents and mature young of the philopatricsex. To investigate the evolutionary basis of natal philopatryin a noncooperative species, the common goldeneye Bucephalaclangula, we studied possible costs and benefits of simultaneousbreeding of females and philopatric daughters. We did not find any fitness consequences of a daughter's breeding on their mother'sbreeding in terms of nest-site selection, body weight, clutchsize, hatching date, or hatching success. Our results, therefore,did not support the assumption of the local resource competitionhypothesis, that the natally philopatric sex should be morecostly to a breeding parent. As possible benefits for daughters returning to their natal area, we tested inheritance of nestsites from mothers and explored whether daughters utilize thepresence of their mother by parasitically sneaking into hermother's nest. Daughters' nest-site selection was not associatedwith the presence of their mothers. A comparison between daughtersand control females revealed that daughters chose their nestsite closer to their natal nest than expected by nest-siteavailability alone. Daughters could not expect to inherit anest site from their mother, and we did not find other indicationsof cooperation between relatives either. The mother's clutchsize did not increase in the year breeding with the daughter, indicating daughters do not parasitize their mother's nest.We suggest that benefits such as decreased nest predation riskassociated with nesting close to the natal nest site may beimportant in the natal philopatric behavior of the species.     

Effects of short-term hunger and competitive asymmetry on facultative aggression in nestling black guillemots Cepphus grylle

Siblings in a diversity of species are facultatively aggressive,yet the proximate control of the aggressive response and theecological conditions selecting for such systems are poorlyunderstood. In this study, we investigated the effects of foodamount (food amount hypothesis) and competitive asymmetry onsibling aggression in black guillemot broods. Parental provisioningrates were experimentally manipulated in broods comprisinga range of hatching intervals over a 12-h period. Aggressionbecame evident only after parental provisioning rates wereexperimentally reduced. When parental provisioning resumed,adults did not increase their feeding rate to compensate forthe induced food deficit, and the result of sibling rivalry was a change in the allocation of parental deliveries from oneof equality to one in favor of the dominant chick. Food-deprivedchicks from synchronous broods were more aggressive than thosefrom asynchronous broods, suggesting that one benefit of hatchingasynchrony in the black guillemot is to establish an efficientcompetitive hierarchy among siblings which minimizes the needfor costly aggressive interactions. On the following day, siblingaggression ceased, and chicks regained an equal share of parentalfeeds. Our results provide the first evidence that short-termfood shortage per se acts as an initial trigger for aggressionand also show that the aggressive response is complicated byfactors associated with hatching and laying order.