A forensic approach to understanding habitat use from stable isotope analysis of (avian) claw material

1. The potential of using stable isotope signatures of avian claws in order to infer diet and habitat use was investigated. 2. Highly significant relationships observed between stable carbon and nitrogen isotope ratios (13C, 15N) in the claws and body feathers of resident birds were expected since it was predicted that they were synthesized in the same habitat and approximately the same time of year. 3. Likewise the non-significant relationships observed between 13C and 15N in the claws and tertial feathers of neotropical migrant birds were also predicted since the claws were synthesized in the wintering area and the tertials in the breeding area. 4. The growth rates measured in the claws of five species of palearctic passerines provide evidence that this tissue should integrate dietary and habitat information over a medium temporal scale (probably weeks to months). 5. It is suggested that claws may offer a unique combination of attributes to the isotope ecologist: they are non-invasively sampled; metabolically inert but grow continuously, and are therefore a more flexible tool than feathers. 6. It is also suggested that that the stable isotope signatures in the claws of mammals and reptiles may provide similar information. 6. It is also suggested that that the stable isotope signatures in the claws of mammals and reptiles may provide similar information

Social information use and collective foraging in a pursuit diving seabird

This is the final version. Available on open access from Public Library of Science via the DOI in this recordData Availability: Data files are available from an online data repository (DOI: 10.6084/m9.figshare.9798491).Individuals of many species utilise social information whilst making decisions. While many studies have examined social information in making large scale decisions, there is increasing interest in the use of fine scale social cues in groups. By examining the use of these cues and how they alter behaviour, we can gain insights into the adaptive value of group behaviours. We investigated the role of social information in choosing when and where to dive in groups of socially foraging European shags. From this we aimed to determine the importance of social information in the formation of these groups. We extracted individuals’ surface trajectories and dive locations from video footage of collective foraging and used computational Bayesian methods to infer how social interactions influence diving. Examination of group spatial structure shows birds form structured aggregations with higher densities of conspecifics directly in front of and behind focal individuals. Analysis of diving behaviour reveals two distinct rates of diving, with birds over twice as likely to dive if a conspecific dived within their visual field in the immediate past. These results suggest that shag group foraging behaviour allows individuals to sense and respond to their environment more effectively by making use of social cues

A bird's eye view of discard reforms: bird-borne cameras reveal seabird/fishery interactions.

notes: PMCID: PMC3590202types: Journal Article; Research Support, Non-U.S. Gov'tCopyright: © 2013 Votier et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Commercial capture fisheries produce huge quantities of offal, as well as undersized and unwanted catch in the form of discards. Declines in global catches and legislation to ban discarding will significantly reduce discards, but this subsidy supports a large scavenger community. Understanding the potential impact of declining discards for scavengers should feature in an eco-system based approach to fisheries management, but requires greater knowledge of scavenger/fishery interactions. Here we use bird-borne cameras, in tandem with GPS loggers, to provide a unique view of seabird/fishery interactions. 20,643 digital images (one min(-1)) from ten bird-borne cameras deployed on central place northern gannets Morus bassanus revealed that all birds photographed fishing vessels. These were large (>15 m) boats, with no small-scale vessels. Virtually all vessels were trawlers, and gannets were almost always accompanied by other scavenging birds. All individuals exhibited an Area-Restricted Search (ARS) during foraging, but only 42% of ARS were associated with fishing vessels, indicating much 'natural' foraging. The proportion of ARS behaviours associated with fishing boats were higher for males (81%) than females (30%), although the reasons for this are currently unclear. Our study illustrates that fisheries form a very important component of the prey-landscape for foraging gannets and that a discard ban, such as that proposed under reforms of the EU Common Fisheries Policy, may have a significant impact on gannet behaviour, particularly males. However, a continued reliance on 'natural' foraging suggests the ability to switch away from scavenging, but only if there is sufficient food to meet their needs in the absence of a discard subsidy.EU INTERREG project CHARM-IIINatural Environment Research CouncilAssociation for the Study of Animal Behaviour research gran

Excess baggage for birds: inappropriate placement of tags on gannets changes flight patterns.

Published onlineJournal ArticleResearch Support, Non-U.S. Gov'tThis is the final version of the article. Available from Public Library of Science via the DOI in this record.Devices attached to flying birds can hugely enhance our understanding of their behavioural ecology for periods when they cannot be observed directly. For this, scientists routinely attach units to either birds' backs or their tails. However, inappropriate payload distribution is critical in aircraft and, since birds and planes are subject to the same laws of physics during flight, we considered aircraft aerodynamic constraints to explain flight patterns displayed by northern gannets Sula bassana equipped with (small ca. 14 g) tail- and back-mounted accelerometers and (larger ca. 30 g) tail-mounted GPS units. Tail-mounted GPS-fitted birds showed significantly higher cumulative numbers of flap-glide cycles and a higher pitch angle of the tail than accelerometer-equipped birds, indicating problems with balancing inappropriately placed weights with knock-on consequences relating to energy expenditure. These problems can be addressed by carefully choosing where to place tags on birds according to the mass of the tags and the lifestyle of the subject species.This study would have not been carried out without the financial support from the California Department of Fish and Game's Oil Spill Response Trust Fund (through the Oiled Wildlife Care Network at the Wildlife Health Center, School of Veterinary Medicine, University of California, Davis) and the Royal Society for Prevention of Cruelty to Animals (RSPCA, Wilberforce Way, Southwater, Horsham, West Sussex, RH13 9RS, United Kingdom). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Size matters in quantitative radar monitoring of animal migration: estimating monitored volume from wingbeat frequency

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this record.Quantitative radar studies are an important component of studying the movements of birds. Whether a bird, at a certain distance from the radar, is detected or not depends on its size. The volume monitored by the radar is therefore different for birds of different sizes. Consequently, an accurate quantification of bird movements recorded by small-scale radar requires an accurate determination of the monitored volume for the objects in question, although this has tended to be ignored. Here, we demonstrate the importance of sensitivity settings for echo detection on the estimated movement intensities of birds of different sizes. The amount of energy reflected from a bird and detected by the radar receiver (echo power) depends not only on the bird's size and on the distance from the radar antenna, but also on the beam shape and the bird's position within this beam. We propose a method to estimate the size of a bird based on the wingbeat frequency, retrieved from the echo-signal, independent of the absolute echo power. The estimated bird-size allows calculation of size-specific monitored volumes, allowing accurate quantification of movement intensities. We further investigate the importance of applying size-specific monitored volumes to quantify avian movements instead of using echo counts. We also highlight the importance of accounting for size-specific monitored volume of small scale radar systems, and the necessity of reporting technical information on radar parameters. Applying this framework will increase the quality and validity of quantitative radar monitoring.COST – European Cooperation in Science and Technolog

Mesoscale fronts as foraging habitats: composite front mapping reveals oceanographic drivers of habitat use for a pelagic seabird

The oceanographic drivers of marine vertebrate habitat use are poorly understood yet fundamental to our knowledge of marine ecosystem functioning. Here, we use composite front mapping and high-resolution GPS tracking to determine the significance of mesoscale oceanographic fronts as physical drivers of foraging habitat selection in northern gannets Morus bassanus. We tracked 66 breeding gannets from a Celtic Sea colony over 2 years and used residence time to identify area-restricted search (ARS) behaviour. Composite front maps identified thermal and chlorophyll-a mesoscale fronts at two different temporal scales—(i) contemporaneous fronts and (ii) seasonally persistent frontal zones. Using generalized additive models (GAMs), with generalized estimating equations (GEE-GAMs) to account for serial autocorrelation in tracking data, we found that gannets do not adjust their behaviour in response to contemporaneous fronts. However, ARS was more likely to occur within spatially predictable, seasonally persistent frontal zones (GAMs). Our results provide proof of concept that composite front mapping is a useful tool for studying the influence of oceanographic features on animal movements. Moreover, we highlight that frontal persistence is a crucial element of the formation of pelagic foraging hotspots for mobile marine vertebrates

Seabird movement reveals the ecological footprint of fishing vessels.

Exploitation of the seas is currently unsustainable, with increasing demand for marine resources placing intense pressure on the Earth's largest ecosystem [1]. The scale of anthropogenic effects varies from local to entire ocean basins [1-3]. For example, discards of commercial capture fisheries can have both positive and negative impacts on scavengers at the population and community-level [2-6], although this is driven by individual foraging behaviour [3,7]. Currently, we have little understanding of the scale at which individual animals initiate such behaviours. We use the known interaction between fisheries and a wide-ranging seabird, the Northern gannet Morus bassanus[3], to investigate how fishing vessels affect individual birds' behaviours in near real-time. We document the footprint of fishing vessels' (≥15 m length) influence on foraging decisions (≤11 km), and a potential underlying behavioural mechanism, by revealing how birds respond differently to vessels depending on gear type and activity. Such influences have important implications for fisheries, including the proposed discard ban [8]), and wider marine management

Ecological Responses to Extreme Flooding Events: A Case Study with a Reintroduced Bird.

Published onlineJournal ArticleIn recent years numerous studies have documented the effects of a changing climate on the world's biodiversity. Although extreme weather events are predicted to increase in frequency and intensity and are challenging to organisms, there are few quantitative observations on the survival, behaviour and energy expenditure of animals during such events. We provide the first data on activity and energy expenditure of birds, Eurasian cranes Grus grus, during the winter of 2013-14, which saw the most severe floods in SW England in over 200 years. We fitted 23 cranes with telemetry devices and used remote sensing data to model flood dynamics during three consecutive winters (2012-2015). Our results show that during the acute phase of the 2013-14 floods, potential feeding areas decreased dramatically and cranes restricted their activity to a small partially unflooded area. They also increased energy expenditure (+15%) as they increased their foraging activity and reduced resting time. Survival did not decline in 2013-14, indicating that even though extreme climatic events strongly affected time-energy budgets, behavioural plasticity alleviated any potential impact on fitness. However under climate change scenarios such challenges may not be sustainable over longer periods and potentially could increase species vulnerability.We thank Mitch Weegman, Miguel Villoslada and Anne Harrison for technical support and advice; to Jorge S. Gutierrez for helpful suggestions on the drafts of the manuscript; and to Damon Bridge and RSPB (Royal Society for the Protection of Birds) volunteers for providing survival and breeding data. We also thank the Environmental Agency for allowing us access to water gauge measurements in the study area. We are grateful to Larry Griffin, Amy King, Harry Nevard and numerous volunteers for assistance with telemetry deployments. SB is funded by an EU consolidator’s grant: STATEMIG 310820. ASR is supported by a joint predoctoral grant from the University of Exeter, the Wildfowl and Wetlands Trust (WWT) and the RSPB

Using time-series similarity measures to compare animal movement trajectories in ecology

Identifying and understanding patterns in movement data are amongst the principal aims of movement ecology. By quantifying the similarity of movement trajectories, inferences can be made about diverse processes, ranging from individual specialisation to the ontogeny of foraging strategies. Movement analysis is not unique to ecology however, and methods for estimating the similarity of movement trajectories have been developed in other fields but are currently under-utilised by ecologists. Here, we introduce five commonly used measures of trajectory similarity: dynamic time warping (DTW), longest common subsequence (LCSS), edit distance for real sequences (EDR), Fréchet distance and nearest neighbour distance (NND), of which only NND is routinely used by ecologists. We investigate the performance of each of these measures by simulating movement trajectories using an Ornstein-Uhlenbeck (OU) model in which we varied the following parameters: (1) the point of attraction, (2) the strength of attraction to this point and (3) the noise or volatility added to the movement process in order to determine which measures were most responsive to such changes. In addition, we demonstrate how these measures can be applied using movement trajectories of breeding northern gannets (Morus bassanus) by performing trajectory clustering on a large ecological dataset. Simulations showed that DTW and Fréchet distance were most responsive to changes in movement parameters and were able to distinguish between all the different parameter combinations we trialled. In contrast, NND was the least sensitive measure trialled. When applied to our gannet dataset, the five similarity measures were highly correlated despite differences in their underlying calculation. Clustering of trajectories within and across individuals allowed us to easily visualise and compare patterns of space use over time across a large dataset. Trajectory clusters reflected the bearing on which birds departed the colony and highlighted the use of well-known bathymetric features. As both the volume of movement data and the need to quantify similarity amongst animal trajectories grow, the measures described here and the bridge they provide to other fields of research will become increasingly useful in ecology

Bottom-up effects of a no-take zone on endangered penguin demographics

This is the author's postprint version of the article. Data used for analyses in this manuscript are available in Dryad: http://dx.doi.org/10.5061/dryad.t446r. Supplementary materials are available under the Creative Commons License CC-BY version 4.0 at http://rsbl.royalsocietypublishing.org/content/roybiolett/suppl/2015/07/08/rsbl.2015.0237.DC1/rsbl20150237supp1.pdfThe definitive published version of the article is available via DOI: 10.1098/rsbl.2015.0237Marine no-take zones can have positive impacts for target species and are increasingly important management tools. However, whether they indirectly benefit higher order predators remains unclear. The endangered African penguin (Spheniscus demersus) depends on commercially exploited forage fish. We examined how chick survival responded to an experimental 3-year fishery closure around Robben Island, South Africa, controlling for variation in prey biomass and fishery catches. Chick survival increased by 18% when the closure was initiated, which alone led to a predicted 27% higher population compared with continued fishing. However, the modelled population continued to decline, probably because of high adult mortality linked to poor prey availability over larger spatial scales. Our results illustrate that small no-take zones can have bottom-up benefits for highly mobile marine predators, but are only one component of holistic, ecosystem-based management regimes.The Earthwatch InstituteThe Bristol Zoological SocietyThe Leiden Conservation FoundationThe National Research Foundation (South Africa