Drivers of resource allocation for breeding under variable environments in a bet hedger.

The evolutionary theory of life histories predicts that there is a trade-off between survival and reproduction: since adult survival in long-lived organisms is high, then breeding investment is more variable and more dependent on conditions (e.g. food availability and individual experience). Clutch features influence fitness prospects, but how a bet hedger builds its clutch in temporally varying environments is quite unknown. Using 27-year data on 2847 clutches of known-age breeders, we analyse how Audouin's gulls (Larus audouinii), a species showing a combination of conservative and adaptive bet-hedging breeding strategies, can allocate energy by laying clutches and eggs of different sizes. Results show that both food availability and age influenced clutch size and total egg volume in a clutch. Interestingly, we found an interaction between food and age on egg parameters: total volume in two-egg clutches, laid mostly by younger breeders, did not significantly change with food availability and the quadratic pattern in clutch size over the range of ages was less marked as long as food conditions became harsher. With increased food, females invested more by building larger first eggs, whereas they were more conservative on second and third eggs. Furthermore, asymmetries in egg volume within three-egg clutches increased with food availability for old females. Egg size profiles of two-egg clutches suggest that gulls should exhibit progressive reduction of the size of the third egg before shifting to a two-egg clutch size. Food availability influenced all parameters studied, whereas age affected the amount of energy allocated for producing eggs (their size and number) but not the way of allocating those energies (i.e. asymmetries within the clutch). Despite the range of factors affecting the clutch, results suggest that females can allocate the amount of resources in a clutch optimally to increase their fitness under variable environments via bet-hedging.

Legacy and emerging contaminants in flamingos' chicks' blood from the Ebro Delta Natural Park.

The Ebro Delta is a wetland of international importance for waterbird conservation but severally affected by intensive agriculture, toxic waste discharges from a past chloro-alkali industry and affluence of tourism. The discharge of contaminants associated to these activities pose waterbirds breeding in the Ebro Delta at risk. The aim of this study is to evaluate the exposure of 91 emerging and legacy micropollutants in flamingo chicks (Phoenicopterus roseus), an emblematic species of the area. Fifty chicks of 45-60 days were captured, biometric parameters measured and whole blood collected. Compounds analyzed included perfluoroalkyl substances (PFASs), pharmaceuticals, organophosphate esters (OPEs), in-use pesticides, polychlorinated biphenyls (PCBs), organochlorine pesticides (OCs), and polycyclic aromatic hydrocarbons (PAHs). The results indicate a multi-exposure of flamingo's chicks from a very young age. PFASs were the most ubiquitous compounds with ∑PFASs ranging from 9.34 to 576 ng/mL, being PFOA, PFOS and PFHxS detected in all samples. ∑PAHs ranged from 0.19 to 423 ng/mL, ∑PCBs from 0.5 to 15.6 ng/mL and ∑OCs from 1.35 to 37.8 ng/mL. Pharmaceuticals, OPEs and in-use pesticides were not detected. The flamingo's filtering behavior on mud and maternal ovo-transference are the more likely routes of exposure of organic micropollutants to flamingos' chicks. The reported levels of micropollutants were not associated with any alteration in the body condition of chicks. This is the first study to describe flamingos chicks' exposure to multiple contaminants, highlighting the importance of biomonitoring for wildlife conservation and biodiversity preservation.

Inferring the age of breeders from easily measurable variables.

Age drives differences in fitness components typically due to lower performances of younger and senescent individuals, and changes in breeding age structure influence population dynamics and persistence. However, determining age and age structure is challenging in most species, where distinctive age features are lacking and available methods require substantial efforts or invasive procedures. Here we explore the potential to assess the age of breeders, or at least to identify young and senescent individuals, by measuring some breeding parameters partially driven by age (e.g. egg volume in birds). Taking advantage of a long-term population monitored seabird, we first assessed whether age influenced egg volume, and identified other factors driving this trait by using general linear models. Secondly, we developed and evaluated a machine learning algorithm to assess the age of breeders using measurable variables. We confirmed that both younger and older individuals performed worse (less and smaller eggs) than middle-aged individuals. Our ensemble training algorithm was only able to distinguish young individuals, but not senescent breeders. We propose to test the combined use of field monitoring, classic regression analysis and machine learning methods in other wild populations were measurable breeding parameters are partially driven by age, as a possible tool for assessing age structure in the wild.

It's not all abundance: Detectability and accessibility of food also explain breeding investment in long-lived marine animals.

Large-scale climatic indices are extensively used as predictors of ecological processes, but the mechanisms and the spatio-temporal scales at which climatic indices influence these processes are often speculative. Here, we use long-term data to evaluate how a measure of individual breeding investment (the egg volume) of three long-lived and long-distance-migrating seabirds is influenced by i) a large-scale climatic index (the North Atlantic Oscillation) and ii) local-scale variables (food abundance, foraging conditions, and competition). Winter values of the North Atlantic Oscillation did not correlate with local-scale variables measured in spring, but surprisingly, both had a high predictive power of the temporal variability of the egg volume in the three study species, even though they have different life-history strategies. The importance of the winter North Atlantic Oscillation suggests carry-over effects of winter conditions on subsequent breeding investment. Interestingly, the most important local-scale variables measured in spring were associated with food detectability (foraging conditions) and the factors influencing its accessibility (foraging conditions and competition by density-dependence). Large-scale climatic indices may work better as predictors of foraging conditions when organisms perform long distance migrations, while local-scale variables are more appropriate when foraging areas are more restricted (e.g. during the breeding season). Contrary to what is commonly assumed, food abundance does not directly translate into food intake and its detectability and accessibility should be considered in the study of food-related ecological processes.

Distribution and ten-year temporal trends (2009-2018) of perfluoroalkyl substances in gull eggs from Spanish breeding colonies.

Gull eggs are excellent bioindicators of environmental pollution as reflect the contamination levels of coastal areas, especially of persistent and bioacumulative compounds such as perfluoroalkyl substances (PFAS). This study aims to evaluate the geographical distribution and 10-year temporal trends (2009-2018) of 17 PFAS in eggs of two gull species (Larus michahellis and Larus audouinii) from 5 main Spanish colonies. ∑PFAS ranged from 13.7 ± 5.9 to 164 ± 17 ng g-1 wet weight and higher concentrations were observed in L. audouinii than in L. michahellis. Perfluorooctane sulfonate (PFOS) was the predominant compound in all samples, followed by perfluoroundecanoic acid (PFUnA) and perfluorotridecanoic acid (PFTriDA). Perfluorododecanoic acid (PFDoA), perfluorodecanoic acid (PFDA) and perfluorooctanoic acid (PFNA) were also found in all studied areas but at lower concentrations, while perfluorooctanoic acid (PFOA) was only detected in the Medes Islands. Principal Component Analysis revealed the co-occurrence of the 6 detected PFAS, and differentiated samples from Ebro Delta and Medes Islands, both located in the North-Eastern Mediterranean Sea, with high contribution of all PFAS, from Chafarinas and Atlantic Islands with lower concentration levels and variability. Also, different patterns were observed among colonies, suggesting the fish-based diet plays an important role in PFAS bioaccumulation. In all colonies, except for the Medes Islands, ∑PFAS decreased through the 10-year study period, with PFOS, PFUnA, and PFTriDA showing a significant concentration reduction in a colony-specific manner. This study demonstrates the usefulness and importance of continuous systematic long-term monitoring to determine the geographical distribution and temporal variations of PFAS in marine protected areas using gull eggs as bioindicators of environmental pollution.

Temporal and Spatial Distribution of Mercury in Gulls Eggs from the Iberian Peninsula.

We examined how coastal mercury contamination varied spatially and temporally across the Iberian Peninsula by measuring mercury concentrations in the eggs of the sentinel biomonitor yellow-legged gull (Larus michahellis). Samples were collected from eight colonies that ranged from the Atlantic across the south and northern areas of the Mediterranean. We also measured Hg residues in eggs of the one of the most endangered gull species in the world, the Audouin's gull (Larus audouinii) from the Ebro Delta, where colonies of yellow-legged and Audouin's gull co-occur. Fresh eggs were collected in 2009 and 2016 and samples were pooled from each colony for analysis. Mercury concentrations in yellow-legged gulls ranged between 0.4 and 2.8 mg/kg dry weight (dw); although there were no significant differences in concentrations between sampling periods, significant differences were found between colonies. Higher concentrations were associated with northern Mediterranean colonies (Columbretes and Ebro Delta), likely due to proximity to emission sources, circulatory marine currents and diet composition. Mercury concentrations in yellow-legged gull eggs were lower than those reported to result in impaired hatching. Residues in Audouin's gull eggs from the Ebro Delta were significantly higher (4.0-5.6 mg/kg dw) than those in yellow-legged gull from the same location, probably associated with dietary differences. Mercury levels in Audouin's gull were ten times above the benchmark suggested to reduce nest success by 10%. Overall, these results raise concern for adverse health impacts in this protected seabird species and further investigation in Audouin's gull eggs from the Ebro Delta is recommended.

Presence and impact of Stockholm Convention POPs in gull eggs from Spanish and Portuguese natural and national parks.

The aim of the present work was to comparatively assess the occurrence and impact of persistent organic pollutants (POPs) in nine natural and national parks from Spain and Portugal using gull eggs (Larus michahellis and L. audouinii) as bioindicators of environmental contamination. Sampling was performed during the breeding season of 2016. Compounds studied include polychlorinated biphenyls (PCBs), organochlorinated pesticides (OC pesticides), perfluorooctane sulfonic acid (PFOS) and polybrominated diphenyl ethers (PBDEs), and were analyzed using mass spectrometric based techniques. The results showed a high contamination by PCBs in all colonies, with total levels ranging from 59 to 1278ng/g wet weight (ww), despite their use is not currently authorized. OC pesticides were also present in all colonies, with a high incidence of 4,4'-DDE in gull eggs at levels up to 218±50ng/g ww in L. michahellis and 760±412ng/g ww in L. audouinii from the Ebro Delta natural park. PBDEs and PFOS were also detected at levels up to 91.7±21.3ng/g ww, which can be attributed to a more recent use. Except for PBDEs, the POP levels in eggs from L. audouinii were higher than in L. michahellis, presumably associated to the fish-based diet of the former. Finally, the effect of POP levels on eggshell parameters (volume, eggshell thickness and desiccation index) were investigated for each colony and gull species in order to evaluate the egg viability and, therefore, the reproduction success.

The effect of growth rate and ageing on colour variation of European pond turtles.

Many chelonians have colourful dots, patches and stripes throughout their body that are made up, at least in part, of carotenoids. Therefore, turtles are very suitable models to study the evolution and functionality of carotenoid-based colouration. Recent studies suggested a close link between colouration and immune system in these taxa. However, more research is needed to understand the role of these colourful stripes and patches in turtle visual signalling. The purpose of this study was to explore the relationship between growth rate and colouration in European pond turtles. In particular, we wanted to answer the question of whether there is a trade-off between growth and colour expression. We also aimed to explore the effect of body size and age on colour variation. Turtles from a reintroduction-breeding program were recaptured, weighed and measured over an 8-year period to estimate their growth rates and age. We also measured with a spectrometer the reflectance of colour patches in two different body parts: shell and forelimb. We found that turtles with a faster growth rate had brighter limb stripes independently of their age. On the other hand, shell colouration was related to body size with larger turtles having brighter shell stripes and higher values of carotenoid chroma. Our results suggest that fast-growers may afford to express intense colourful limb stripes likely due to their higher intake of carotenoids that would modulate both growth and colour expression. However, shell colouration was related to body size probably due to ontogenetic differences in the diet, as juveniles are strictly carnivorous while adults are omnivorous. Alternatively, shell colouration might be involved in crypsis as the shell is visually exposed to predators.

Dioxins and dl-PCBs in gull eggs from Spanish Natural Parks (2010-2013).

The aim of this study was to evaluate the presence and distribution of polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDD/Fs) and biphenyls (PCBs), concretely those so-called as dioxin-like PCBs, in yellow-legged gull eggs (Larus michahellis) collected from five Natural Parks (some of them National Parks) in Spain during the period 2010-2013. PCDD/Fs and dl-PCBs were detected in all the samples. Due to the proximity to important urban and industrial areas higher concentrations were determined in colonies located in the Northern Mediterranean coast than those found in the Southern Mediterranean or Atlantic colonies where a softer anthropogenic impact occurs. Mean ∑PCDD/F concentrations ranged from 49 to 223pg/g lipid weight (lw) and ∑dl-PCB concentrations varied from 146 to 911ng/g lw. In the Natural Park of the Ebro Delta (Northern Mediterranean coast) two gull species share habitat: yellow-legged and Audouin gull (Larus audouinii). Eggs from both species were collected and PCDD/F and dl-PCB levels compared. The species that feeds exclusively on pelagic fish (L. audouinii) had significantly higher PCDD/F and dl-PCB levels than the scavenger L. michahellis, pointing out the diet-dependent differences in the accumulation of persistent organic pollutants between similar cohabitant breeding species. Finally, mean TEQ values were in general below those considered as critical for toxicological effects in birds.

Variation in immune parameters and disease prevalence among Lesser Black-backed Gulls (Larus fuscus sp.) with different migratory strategies.

The ability to control infections is a key trait for migrants that must be balanced against other costly features of the migratory life. In this study we explored the links between migration and disease ecology by examining natural variation in parasite exposure and immunity in several populations of Lesser Black-backed Gulls (Larus fuscus) with different migratory strategies. We found higher activity of natural antibodies in long distance migrants from the nominate subspecies L.f.fuscus. Circulating levels of IgY showed large variation at the population level, while immune parameters associated with antimicrobial activity showed extensive variation at the individual level irrespective of population or migratory strategy. Pathogen prevalence showed large geographical variation. However, the seroprevalence of one of the gull-specific subtypes of avian influenza (H16) was associated to the migratory strategy, with lower prevalence among the long-distance migrants, suggesting that migration may play a role in disease dynamics of certain pathogens at the population level.

Accumulation and maternal transfer of perfluorooctane sulphonic acid in yellow-legged (Larus michahellis) and Audouin's gull (Larus audouinii) from the Ebro Delta Natural Park.

This study aimed to determine the accumulation and maternal transfer of perfluorooctane sulphonic acid (PFOS) in yellow-legged gulls (YLG, Larus michahellis) and the protected species Audouin's gull (AG, Larus audouinii), which cohabit in the Ebro Delta Natural Park (Catalonia, Spain). The Estimated Daily Intake (EDI) through diet (fish and crayfish), depuration rates and transfer capacity from blood to first eggs was studied for a set of 44 pairs. For AG, mean (±SD) EDI was of 128 ± 36 ng/d in males and 119 ± 32 ng/d in females, and for YLG, 170 ± 48 ng/d in males and 159 ± 42 ng/d in females. PFOS levels in blood were higher in males than females (60.6 ± 21 and 61.1 ± 2 7ng/g ww in AG and YLG males versus 25.2 ± 12 and 27.3 ± 14 ng/g ww in AG and YLG females), with little differences among species. The lower levels in females were attributed to the annual release of PFOS to eggs during the laying period, which was estimated of 5544 ± 1571 ng/egg for AG females and 6716 ± 2689 ng/egg for YLG. The overall mass balance of PFOS calculated for both species clearly demonstrates that uptake is higher than elimination rates, considering depuration rates and transfer of PFOS to eggs, and this explains that PFOS is accumulated in gulls in a yearly basis.

Living on the edge: demography of the slender-billed gull in the Western Mediterranean.

Small and peripheral populations are typically vulnerable to local extinction processes but important for the metapopulation dynamics of species. The Slender-billed gull (Chroicocephalus genei) is a long-lived species breeding in unstable ephemeral coastal habitats. Their Western Mediterranean populations are relatively small and represent the edge of their global geographical distribution. At a local scale, using long-term data (14 years) on annual breeding success and capture-resights of marked individuals, we estimated and compared the vital rates and evaluated the connectivity of two Spanish populations (Ebro Delta and Doñana) varying in their local environmental conditions. At a metapopulation scale, we analyzed 22 years of data on breeding numbers to predict their future prospects by means of population demographic models. Local survival and breeding success of gulls from the Ebro Delta was lower than those from Doñana, which is likely the result of higher permanent emigration and/or winter mortality in the former. Gulls from the Ebro Delta wintered mostly in Mediterranean areas whereas those from Doñana did so in Atlantic coasts, where food availability is higher. Whereas adult local survival was constant, juvenile local survival showed temporal parallel variations between colonies, probably related to natal dispersal to other breeding colonies. Our results suggested that dispersal was higher at the Ebro Delta and gulls emigrating from their natal colonies settled preferentially in close patches. We found large fluctuations in breeding numbers among local populations probably related to the fact that the Slender-billed gull is a species adapted to unstable and unpredictable habitats with high abilities to disperse between suitable patches depending on environmental stochastic conditions during breeding.

Persistent Organic Pollutants in gull eggs of two species (Larus michahellis and Larus audouinii) from the Ebro delta Natural Park.

The aim of this study was to determine the impact of priority and emerging Persistent Organic Pollutants (POPs) in gull eggs from two species, the scavenger Larus michahellis and the protected species, Larus audouinii. These two species share habitat in the Natural Park of the Ebro delta (Catalonia, Spain). Compounds studied are included or under consideration in the Stockholm Convention and comprise polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs), polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), organochlorinated compounds (OCs), perfluorinated compounds (PFCs) and short chain chlorinated paraffins (SCCPs). Four methods based in selective extraction and gas or liquid chromatography coupled to mass spectrometry were used and quality parameters are provided. OC pesticides and marker PCBs were the most abundant chemical families detected in eggs from the two species, followed by PFCs, PBDEs (especially BDE 209) and SCCPs. Dioxin-like PCBs and PCDD/Fs were also detected in all samples. The overall widespread presence of POPs is discussed in terms of feeding habits, bird ecology and anthropogenic pressures in the protected Ebro delta breeding area.

Distribution of perfluorinated compounds in Yellow-legged gull eggs (Larus michahellis) from the Iberian Peninsula.

This study is aimed to evaluate the presence and distribution of Perfluorinated Compounds (PFCs) in Yellow-legged gull eggs (Larus michahellis) collected from 8 National or Natural Parks from the Iberian Peninsula. In each colony, 12 eggs were randomly collected and pooled from 3 areas of the colony and analyzed using liquid-solid extraction and liquid chromatography coupled to tandem mass spectrometry. Perfluorooctanate sulfonate (PFOS) was the only compound detected in the eggs and its presence was higher in the colonies situated in NE Iberian Peninsula due to the more industrial and mass urbanization in this area compared to the SW Mediterranean or Atlantic colonies. Accordingly, the Medes site, followed by the Ebro Delta and Columbretes, all situated in the NW Mediterranean coast, contained the highest PFOS levels (40.5-54.0ng/g-ww). In all other colonies, PFOS was detected at levels of 10.1-18.6ng/g-ww. Egg shell biometry was studied and it was found that the presence of PFOS did not affect the development of the egg.