Assay optimisation and age-related baseline variation in biochemical markers in Lesser Black-backed gulls.

Free-ranging animals are often used as bioindicators of both short- and long-term changes in ecosystem health, mainly to detect the presence and effects of contaminants. Birds, and gulls in particular, have been used as bioindicators over a broad range of marine and terrestrial ecosystems. In this study, we standardise the conditions for the use of a suite of biochemical markers in non-destructive matrices of Lesser Black-backed Gull (Larus fuscus) to facilitate future biomonitoring of marine and terrestrial contaminants. We characterized cholinesterase (ChE) in plasma and optimized assay conditions for ChE activity as a marker of neurotoxic damage. Moreover, we quantified variation in activity of ChE, lactate dehydrogenase (LDH), glutathione-S-transferase (GST) and catalase (CAT) as well as variation ranges of lipid peroxidation (LPO), in free-ranging adults and captive chicks. The main ChE form present in plasma of both adults and chicks was butyrylcholinesterase (BChE) followed by acetylcholinesterase (AChE), whose relative proportion in plasma tended to decrease with increased chick age. LPO levels and GST activity in blood cells (BCs) decreased significantly with increasing chick age, while BChE and LDH activity in plasma were not age-dependent. CAT in BCs tended to decline non-significantly in older chicks. Results of this study underscore the importance of standardising assay conditions and assessing intrinsic baseline variation in biochemical markers, before biochemical quantification. Data presented here provide a foundation for future use of BChE and LDH activity in plasma, as well as oxidative stress markers (LPO, CAT and GST) in BCs, to monitor environmental stress effects in Lesser Black-backed gulls.

Drivers of bat activity at wind turbines advocate for mitigating bat exposure using multicriteria algorithm-based curtailment.

Wind turbine development is growing exponentially and faster than other sources of renewable energy worldwide. While multi-turbine facilities have small physical footprint, they are not free from negative impacts on wildlife. This is particularly true for bats, whose population viability can be threatened by wind turbines through mortality events due to collisions. Wind turbine curtailment (hereafter referred to as "blanket curtailment") in non-winter periods at low wind speeds and mild temperatures (i.e. when bats are active and wind energy production is low) can reduce fatalities, but show variable and incomplete effectiveness because other factors affect fatality risks including landscape features, rain, turbine functioning, and seasonality. The combined effects of these drivers, and their potential as criteria in algorithm-based curtailment, have so far received little attention. We compiled bat acoustic data recorded over four years at 34 wind turbine nacelles in France from post-construction regulatory studies, including 8619 entire nights (251 ± 58 nights per wind turbine on average). We modelled nightly bat activity in relation to its multiple drivers for three bat guilds, and assessed whether curtailment based on algorithm would be more efficient to limit bat exposure than blanket curtailment based on various combinations of unique wind speed and temperature thresholds. We found that landscape features, weather conditions, seasonality, and turbine functioning determine bat activity at nacelles. Algorithm-based curtailment is more efficient than blanket curtailment, and has the potential to drastically reduce bat exposure while sustaining the same energy production. Compared to blanket curtailment, the algorithm curtailment reduces average exposure by 20 to 29 % and 7 to 12 % for the high-risk guilds of long- and mid-range echolocators, and by 24 to 31 % for the low-risk guild of short-range echolocators. These findings call for the use of algorithm curtailment as both power production and biodiversity benefits will be higher in most situations.

Mercury Uptake Affects the Development of Larus fuscus Chicks.

Current emission and mobilization rates of mercury (Hg) in the environment pose extensive threats to both wildlife and human health. Assessing the exposure risk and effects of Hg contamination in model species such as seabirds is essential to understand Hg risks at the population and ecosystem levels. The lesser black-backed gull (Larus fuscus), a generalist seabird species, is an excellent model species because it forages in both marine and terrestrial habitats, which in turn differ in their Hg exposure risk. To identify possible deleterious effects of Hg exposure on developing L. fuscus chicks, a dietary experiment was carried out and chicks were provided a marine, terrestrial, or mixed diet. The effects of embryonic and dietary Hg exposure on chick body condition and physiological state were assessed at different developmental stages until fledging age (30 d). Overall physiological condition was lower in chicks fed a predominantly marine diet, which coincided with higher Hg loads in blood and primary feathers. However, no effect of dietary uptake of Hg was observed on body condition or in terms of genotoxic damage. Body condition and genotoxic damage correlated instead with Hg exposure during embryonic development, which seems to indicate that embryonic exposure to Hg may result in carry-over effects on later chick development. Environ Toxicol Chem 2020;39:2008-2017. © 2020 SETAC.

Time and energy costs of different foraging choices in an avian generalist species.

BACKGROUND: Animals can obtain a higher foraging yield by optimizing energy expenditure or minimizing time costs. In this study, we assessed how individual variation in the relative use of marine and terrestrial foraging habitats relates to differences in the energy and time investments of an avian generalistic feeder (the Lesser Black-backed Gull, Larus fuscus), and how this changes during the course of the chick-rearing period. METHODS: We analyzed 5 years of GPS tracking data collected at the colony of Zeebrugge (Belgium). Cost proxies for energy expenditure (overall dynamic body acceleration) and time costs (trip durations and time spent away from the colony), together with trip frequency, were analyzed against the relative use of the marine and terrestrial habitats. RESULTS: The marine habitat was most often used by males and outside weekends, when fisheries are active. Marine trips implied higher energetic costs and lower time investments. As chicks became older, terrestrial trips became more prevalent, and trip frequency reached a peak towards 20 days after hatching of the first egg. Over a full chick rearing period, energy costs varied widely between individuals, but no trends were found across the marine foraging gradient. Conversely, a higher use of marine foraging implied lower overall amounts of time spent away from the colony. CONCLUSIONS: Foraging habitat choice was related to overall time costs incurred by gulls, but not to energy costs. The effect of chick age on foraging habitat choice and effort may be driven by energy expenditure constraints on the amount of marine foraging that can be performed. If time is less constraining to them, Lesser Black-backed Gulls may meet the increasing chick demand for food by switching from high to low energy demanding foraging strategies.

Recently-adopted foraging strategies constrain early chick development in a coastal breeding gull.

Human-mediated food sources offer possibilities for novel foraging strategies by opportunistic species. Yet, relative costs and benefits of alternative foraging strategies vary with the abundance, accessibility, predictability and nutritional value of anthropogenic food sources. The extent to which such strategies may ultimately alter fitness, can have important consequences for long-term population dynamics. Here, we studied the relationships between parental diet and early development in free-ranging, cross-fostered chicks and in captive-held, hand-raised chicks of Lesser Black-backed Gulls (Larus fuscus) breeding along the Belgian coast. This traditionally marine and intertidal foraging species is now increasingly taking advantage of human activities by foraging on terrestrial food sources in agricultural and urban environments. In accordance with such behavior, the proportion of terrestrial food in the diet of free-ranging chicks ranged between 4% and 80%, and consistent stable isotope signatures between age classes indicated that this variation was mainly due to between-parent variation in feeding strategies. A stronger terrestrial food signature in free-ranging chicks corresponded with slower chick development. However, no consistent differences in chick development were found when contrasting terrestrial and marine diets were provided ad libitum to hand-raised chicks. Results of this study hence suggest that terrestrial diets may lower reproductive success due to limitations in food quantity, rather than quality. Recent foraging niche expansion toward terrestrial resources may thus constitute a suboptimal alternative strategy to marine foraging for breeding Lesser Black-backed Gulls during the chick-rearing period.

Offspring Hg exposure relates to parental feeding strategies in a generalist bird with strong individual foraging specialization.

Generalist species can potentially exploit a wide variety of resources, but at the individual level they often show a certain degree of foraging specialization. Specific foraging strategies, however, may increase exposure to environmental contaminants that can alter the cost-benefit balance of consuming particular food items. The Lesser Black-backed Gull (Larus fuscus) is known to opportunistically feed on a wide range of marine and terrestrial prey that differ in contaminant load, such as mercury (Hg) that strongly biomagnifies through the aquatic food web. The hypothesis tested in this study were: i) a predominant use of marine prey by females during egg-formation and by both parents during chick rearing increases the exposure to Hg during embryonic development and chick growth, and ii) this affects parental investment in clutch volume, chick growth and body condition. Total Hg burden and isotopic signatures of carbon (δ13C) and nitrogen (δ15N) were determined for eggs, down feathers, and primary feathers of L. fuscus chicks collected at a coastal colony in Belgium. As expected, eggs and feathers of chicks from parents with a stable isotope signature that suggested a predominantly marine diet had higher levels of Hg. The use of marine resources by females during the egg-formation period positively correlated to maternal investment in egg size, though entailing the cost of increased Hg-concentrations which in turn negatively affected clutch volume. Furthermore, it is shown that the use of chick down feathers is a suitable matrix to non-lethally estimate Hg concentrations in eggs. Contrary to our expectations, no relationship between Hg exposure and chick growth or chick body condition was found, which may be due the low concentrations found. We conclude that currently Hg contamination does not constitute a risk for development and condition of L. fuscus offspring at the levels currently observed at the Belgian coast.

GPS tracking data of Lesser Black-backed Gulls and Herring Gulls breeding at the southern North Sea coast.

In this data paper, Bird tracking - GPS tracking of Lesser Black-backed Gulls and Herring Gulls breeding at the southern North Sea coast is described, a species occurrence dataset published by the Research Institute for Nature and Forest (INBO). The dataset (version 5.5) contains close to 2.5 million occurrences, recorded by 101 GPS trackers mounted on 75 Lesser Black-backed Gulls and 26 Herring Gulls breeding at the Belgian and Dutch coast. The trackers were developed by the University of Amsterdam Bird Tracking System (UvA-BiTS, http://www.uva-bits.nl). These automatically record and transmit bird movements, which allows us and others to study their habitat use and migration behaviour in great detail. Our bird tracking network is operational since 2013. It is funded for LifeWatch by the Hercules Foundation and maintained in collaboration with UvA-BiTS and the Flanders Marine Institute (VLIZ). The recorded data are periodically released in bulk as open data (http://dataset.inbo.be/bird-tracking-gull-occurrences), and are also accessible through CartoDB and the Global Biodiversity Information Facility (GBIF).