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Many seabirds are attracted to anthropogenic light, and the risk is greater for recent fledglings. Moon phase predicts the probability of stranding (fewer birds strand on the full moon), but it remains uncertain whether moon phase is associated with when young seabirds fledge. Fledging behaviour of nocturnal, burrowing seabirds can be difficult to monitor using traditional methods but can provide insight into environmental factors that influence the risk of stranding. We used passive integrated transponder tags to monitor the fledging dates and times of Leach's storm-petrel (Hydrobates leucorhous) chicks across four breeding seasons (2017, 2018, 2021, 2022) at a major colony in Newfoundland and Labrador, Canada. We also assessed whether moon phase and incident illumination related to fledging date and time. The median fledge time was 1.6 h after sunset (0.6–11.7 h). The median fledge date was 10 October, and fledging dates ranged from 13 September to 13 November. Most importantly, moon phase was not associated with the time and date that Leach's storm-petrel chicks fledged. These results suggest that recently fledged storm-petrels are less attracted to anthropogenic light during high levels of natural illumination, which could indicate periods of higher stranding risk and help concentrate conservation efforts.

Reproductive timing in many taxa plays a key role in determining breeding productivity1 , and is often sensitive to climatic conditions2 . Current climate change may alter the timing of breeding at different rates across trophic levels, potentially resulting in temporal mismatch between the resource requirements of predators and their prey3 . This is of particular concern for higher-trophic-level organisms, whose longer generation times confer a lower rate of evolutionary rescue than primary producers or consumers4 . However, the disconnection between studies of ecological change in marine systems makes it difficult to detect general changes in the timing of reproduction5 . Here, we use a comprehensive meta-analysis of 209 phenological time series from 145 breeding populations to show that, on average, seabird populations worldwide have not adjusted their breeding seasons over time (−0.020 days yr−1) or in response to sea surface temperature (SST) (−0.272 days °C−1) between 1952 and 2015. However, marked between-year variation in timing observed in resident species and some Pelecaniformes and Suliformes (cormorants, gannets and boobies) may imply that timing, in some cases, is affected by unmeasured environmental conditions. This limited temperature-mediated plasticity of reproductive timing in seabirds potentially makes these top predators highly vulnerable to future mismatch with lower-trophic-level resources2 . Time of reproduction may be altered as the climate changes. For seabirds, it is shown that there has not been an adjustment in timing as the climate changes and the sea surface warms. This lack of plasticity could result in a mismatch with food resources.

Animal tracking provides new means to assess far-reaching environmental impacts. In the aftermath of the Deepwater Horizonexplosion in the Gulf of Mexico, a long-distance migrant, the northern gannet (Morus bassanus) suffered the highest oiling among beach-wrecked birds recovered. Analysis of bird-borne tracking data indicated that 25 per cent of their North American population from multiple colonies in eastern Canada migrated to the pollution zone. Findings contrasted sharply with available mark-recapture (band recovery) data. The timing of movement into and out of the Gulf indicates that immature birds would have absorbed most oil-induced mortality. Consequently, one of two outcomes is likely: either a lagged (likely difficult to assess) population decrease, or an undetectable population response buffered by age-related life-history adaptations. Tracking research is especially useful when little information on animal distributions in pollution zones is available, as is the case in the Gulf of Mexico. Ongoing research highlights current risks and conservation concerns.

The applicability of using stomach temperature telemetry to detect and estimate milk intake throughout lactation was investigated in harbour seals (Phoca vitulina). Observations of a mother-pup pair were conducted daily while stomach temperature was concurrently logged. Milk intake caused a decrease in the pup's stomach temperature. The duration of stomach temperature change was related to the length of the nursing bout (r2=0.82, P<0.001). Laboratory stomach simulations suggested a strong relationship between milk volume and duration of temperature change (r2=0.98, P<0.001). This relationship was used to estimate the volume of milk consumed by the pup. Suckling bout length and the estimated milk intake per bout increased, as a weekly average, with pup age (one-way ANOVA; F3.67=11.66, P<0.001) over the 5-week lactation period. A diel change in nursing time was noted, with a transition from largely nocturnal to daytime feedings. Although not visually confirmed, stomach temperature data collected from the mother provided evidence of seawater ingestion. Methods that could improve estimates of milk intake are discussed. Stomach temperature telemetry proved to be a useful technique for detecting ingestion events in harbour seals, and may provide a valuable tool for investigating lactation energetics and aspects of maternal investment in a variety of nursing species.

Abstract: To examine seasonal and inter-annual shifts in the energy requirements of captive harp seals (Phoca groenlandica), metabolic rate and body temperature were repeatedly measured over the annual cycle. Seasonal shifts were evident in both parameters, with spring and summer (April to September) peaks decreasing throughout fall and winter (October to March). Seasonal changes in oxygen consumption concur with earlier published reports and data presented here validate these trends inter-annually. The standard metabolic rates (SMRs) of all seals were lower than predicted during fall/winter, but were indistinguishable from expected rates during spring/summer. Although individual variation in metabolic rate was largely independent of changes in both total body mass and predicted total body fat over the year, such variation was more closely related to changes in predicted lean body mass. Both deep rectal and core body temperatures co-varied with metabolic rate, perhaps indicating a metabolic defense of fat for thermoregulation. The implications of these shifting basal requirements are considered in the light of calculating the impact of the harp seal herd on fisheries resources in the Northwest Atlantic.

In 1992, the eastern Canadian gillnet fisheries for northern cod and Atlantic salmon were largely closed. These large-scale fishery closures resulted in the removal of tens of thousands of gillnets known to inflict high levels of seabird mortality. We used this unprecedented opportunity to test the effects of gillnet removal on seabird populations. Consistent with predictions, we show that the breeding populations of divers (auks, gannets; susceptible to gillnet bycatch) have increased from pre-closure levels, whereas the populations of scavenging surface-feeders (gulls; low vulnerability to gillnet bycatch but susceptible to removal of fisheries discards) have decreased. Using the most complete series of seabird census data for the species most vulnerable to bycatch, we demonstrate a positive population response of common murres to reduction in gillnet fishing within its foraging range. These findings support the widespread but seldom documented contention that fisheries bycatch negatively impacts populations of non-target large vertebrates.

Dissection and measurement of the carcasses of shy albatrosses, Diomedea cauta cauta, provided morphometric data from known-sex birds from fledgling age to adulthood. These data were used to determine the efficacy of external measures for reliably identifying the sex of birds in the field. As fledglings were smaller than adults and subadults in all measures, separate age-specific equations were developed for assigning their sex. Sexual dimorphism was evident in all head, beak and leg measurements for the adult and subadult birds, with males being significantly larger than females, while there were no sex differences in measures of the wings and tail. Beak and head measurements, along with the weight of fledglings, were taken, and sex differences were evident for all parameters. A stepwise discriminant function analysis of the seven head and beak measures (head length, head width, basal bill width, culmen length, basal bill depth, minimum bill depth and upper bill depth) indicated that 98% of adult and subadult birds could be correctly sexed by measuring the upper bill depth and head width, whilst the sex of 89% of fledglings could be discerned by measuring head length and width and the minimum bill depth. Discriminant scores overlapped less for adults–subadults than for fledglings, indicating that external measurements may be used more reliably to sex this age-class. Data from three experienced observers indicated significant differences in the morphometric measures taken from the same individual albatrosses. The extent of these differences, however, varied greatly depending on the measure taken (i.e. beak v. wing measures), with head and beak measures showing the least inter-observer differences. Such differences resulted in a decrease in the success rate of the adult–subadult discriminant function analysis from 98 to 90%. When working with breeding birds, sex-allocation errors can be reduced by measuring both members of a pair and allowing the relative size of the discriminant score to identify the individuals concerned.