Fishing in the Dark: A Pursuit-Diving Seabird Modifies Foraging Behaviour in Response to Nocturnal Light Levels

Visual predators tend not to hunt during periods when efficiency is compromised by low light levels. Yet common murres, a species considered a diurnal visual predator, frequently dive at night. To study foraging of murres under different light conditions, we used a combination of archival tagging methods and astronomical models to assess relationships between diving behaviour and light availability. During diurnal and crepuscular periods, murres used a wide range of the water column (2–177 m), foraging across light intensities that spanned several orders of magnitude (103–10−10 Wm−2). Through these periods, they readily dived under conditions equivalent to ambient moonlight (∼10−4 Wm−2) but rarely under conditions equivalent to starlight (∼10−8 Wm−2). At night, murres readily foraged during both moonlit and starlit periods, and diving depth and efficiency increased with nocturnal light intensity, suggesting that night diving is at least partially visually guided. Whether visually guided foraging is possible during starlit periods is less clear. Given the dense prey landscape available, random-walk simulations suggest that murres could benefit from random prey encounters. We hypothesise that murres foraging through starlit periods rely either on close-range visual or possibly nonvisual cues to acquire randomly encountered prey. This research highlights the flexibility of breeding common murres and raises questions about the strategies and mechanisms birds use to find prey under very low light conditions

Miniaturized data loggers and computer programming improve seabird risk and damage assessments for marine oil spills in Atlantic Canada

Obtaining useful information on marine birds that can aid in oil spill (and other hydrocarbon release) risk and damage assessments in offshore environments is challenging. Technological innovations in miniaturization have allowed archival data loggers to be deployed successfully on marine birds vulnerable to hydrocarbons on water. A number of species, including murres (both Common, Uria aalge, and Thick-billed, U. lomvia) have been tracked using geolocation devices in eastern Canada, increasing our knowledge of the seasonality and colony-specific nature of their susceptibility to oil on water in offshore hydrocarbon production areas and major shipping lanes. Archival data tags are starting to resolve questions around behaviour of vulnerable seabirds at small spatial scales relevant to oil spill impact modelling, specifically to determine the duration and frequency at which birds fly at sea. Advances in data capture methods using voice activated software have eased the burden on seabird observers who are collecting increasingly more detailed information on seabirds during ship-board and aerial transects. Computer programs that integrate seabird density and bird behaviour have been constructed, all with a goal of creating more credible seabird oil spill risk and damage assessments. In this paper, we discuss how each of these technological and computing innovations can help define critical inputs into seabird risk and damage assessments, and when combined, can provide a more realistic understanding of the impacts to seabirds from any hydrocarbon release

Effects of an Arctic Fox Visit to a Low Arctic Seabird Colony

A visit by an arctic fox (Alopex lagopus) to Funk Island, Newfoundland, during 2009 had a negative impact on the breeding performance of five of the nine breeding seabird species. Species that nest in burrows (Atlantic puffin Fratercula arctica) or on the ground (northern fulmar Fulmarus glacialis, great black-backed Larus marinus and herring gulls Larus argentatus) did not fledge any offspring in 2009, and common murres (Uria aalge) at this colony, the largest for this species in North America, experienced an estimated 4.9% (~19 712.4 breeding pairs) reduction in the number of nesting birds. Later-than-normal persistence of Arctic sea ice on the Newfoundland-Labrador Shelf in 2009 likely provided the fox access to the colony up until late April, which coincided with the seabirds’ return. The persistent predation threat near the onset of breeding likely resulted in large-scale abandonment of breeding attempts by vulnerable seabirds

Foraging strategies of a pursuit-diving seabird in a dynamic marine environment

Flexible foraging tactics are critical to survival for predators foraging in dynamic environments. This is especially true for breeding seabirds as they have to fuel their own energy needs and those of their offspring from a fixed breeding site. To succeed parents must employ foraging strategies that maximize overlap with prey through a range of environmental conditions. Off Newfoundland, breeding common murres Uria aalge specialize on capelin Mallotus villosus. The spatial and temporal distribution of capelin is, therefore, expected to influence the foraging decisions of murres. Though capelin are predictable in many ways, several physical challenges (travel time, light limitations, etc.) limit the murres’ foraging activities. This research focuses on how common murres breeding in Newfoundland deal with their foraging ocean-scape. Integrated analyses of tracking data, colony-based observations, vessel surveys of prey, and physical environmental measurements were used to assess this question. To deal with environmental change, murres exhibited remarkable behavioural flexibility. Though diel vertical migrations of capelin challenged their diving and visual abilities, murres successfully captured capelin throughout diurnal, crepuscular (twilight), and nocturnal periods. They used moonlight to capture capelin at night and also appeared to rely on non-visual cues to capture capelin under a starlit sky – when virtually no light is available in the water column. Over horizontal scales, murres appear to rely on memory to relocate successful foraging patches and area-restricted search to refine their foraging efforts. Because capelin tend to occur in predictable patches that are ephemeral at fine scales, this is likely the most efficient strategy. In combination with flexible time budgets, these strategies likely help murres buffer chick-feed rates across a range of prey densities. However, during mismatch between chick-rearing and peak capelin availability, parental murres were unable to fully compensate for limited access to prey and breeding success was consequently reduced. Though murres exhibit remarkable behavioural plasticity, there are limits to their plasticity. Revealing the limits improves our mechanistic understanding of the links between environmental variability and population dynamics

Seasonal Variation in Parental Care Drives Sex-Specific Foraging by a Monomorphic Seabird

<div><p>Evidence of sex-specific foraging in monomorphic seabirds is increasing though the underlying mechanisms remain poorly understood. We investigate differential parental care as a mechanism for sex-specific foraging in monomorphic Common Murres (<i>Uria aalge</i>), where the male parent alone provisions the chick after colony departure. Using a combination of geolocation-immersion loggers and stable isotopes, we assess two hypotheses: the reproductive role specialization hypothesis and the energetic constraint hypothesis. We compare the foraging behavior of females (n = 15) and males (n = 9) during bi-parental at the colony, post-fledging male-only parental care and winter when parental care is absent. As predicted by the reproductive role specialization hypothesis, we found evidence of sex-specific foraging during post-fledging only, the stage with the greatest divergence in parental care roles. Single-parenting males spent almost twice as much time diving per day and foraged at lower quality prey patches relative to independent females. This implies a potential energetic constraint for males during the estimated 62.8 ± 8.9 days of offspring dependence at sea. Contrary to the predictions of the energetic constraint hypothesis, we found no evidence of sex-specific foraging during biparental care, suggesting that male parents did not forage for their own benefit before colony departure in anticipation of post-fledging energy constraints. We hypothesize that unpredictable prey conditions at Newfoundland colonies in recent years may limit male parental ability to allocate additional time and energy to self-feeding during biparental care, without compromising chick survival. Our findings support differential parental care as a mechanism for sex-specific foraging in monomorphic murres, and highlight the need to consider ecological context in the interpretation of sex-specific foraging behavior.</p></div

Improving the communication and accessibility of stock assessment using interactive visualization tools

Scientists across many fields are faced with the challenge of synthesizing and communicating information from large and complex data sets. The field of stock assessment is no exception as the volume and variety of the data has grown alongside the computational methods used to integrate them. While this growth in data and model complexity has improved many stock assessments, the process of communicating key results to colleagues and stakeholders in a meaningful way has become more daunting. The traditional approach of presenting information across a series of static slides often fails to convey the richness of information available, and as such, important patterns and details are easily overlooked. Here we contend that this problem can be mediated through the effective use of new open source tools for building interactive visualizations. These tools allow a broader audience to conduct detailed explorations of the results, leading to a deeper and collective understanding of both the data and models used to inform stock assessments. As a consequence, the peer review process is more open and accessible.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Deployments (Out), retrievals (In) and data outcomes by site, year, sex and log type.

<p>^<b>A</b> Arctic fox disturbance (details in [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0141190#pone.0141190.ref065" target="_blank">65</a>])</p><p>^B partial (i.e. < 3 logs)</p><p>^C <10 days</p><p>^UM unsuccessful male (i.e. not accompanied by chick at sea)</p><p>^U unknown sex</p><p>^W dive data recorded after 1-Nov.</p><p>Numbers refer to individuals. Letter superscripts explain discrepancies in sample size.</p

Stable isotope values (fractionation adjusted) of murres according to sex and stage.

<p>δ¹⁵N‰ and δ¹³C‰ (mean ± SE) values of blood (BPC; n = 65), secondary covert (MOC; n = 75) and breast (NPC; n = 78) feathers of female (grey) and male (black) murres.</p

Mean time spent foraging (accumulated dive time; mean ± se) of independent females (n = 11; white circle), single-parenting males (n = 6; black circle) and one unsuccessful male (blue circle) from logger deployment to 31 Jan, showing one data point every third day.

<p>Mean time spent foraging (accumulated dive time; mean ± se) of independent females (n = 11; white circle), single-parenting males (n = 6; black circle) and one unsuccessful male (blue circle) from logger deployment to 31 Jan, showing one data point every third day.</p

Mean percent daily number of dives by female and male murres according to light phase during BPC (top left), MOC (top right) and NPC (bottom left).

<p>Values are mean ± SE percent total number of dives day^-1 across individuals (χ² tests: <i>p</i> < 0005). Sample sizes provided in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0141190#pone.0141190.s001" target="_blank">S1 Table</a>.</p