Validation of Water Flux and Body Composition in Glaucous Gulls (Larus hyperboreus)

Multiple stressors including contaminant exposure and parasite infection predict spleen mass and energy expenditure in breeding ring-billed gulls

Daily energy expenditure (DEE) in animals is influenced by many factors although the impact of stressors remains largely unknown. The objective of this study was to determine how multiple physiological stressors (parasite infection and contaminant exposure) and natural challenges (energy-demanding activities and weather conditions) may affect DEE in nesting ring-billed gulls (Larus delawarensis) exposed to high concentrations of persistent organic contaminants (POPs). Physical activity, temperature, gastrointestinal parasitic worm abundance, relative spleen mass, plasma thyroid hormone levels and liver concentrations of POPs were determined; field metabolic rate (FMR) was used as a measure of DEE. For females, FMR was best explained by the percent of time spent in nest-site attendance and exposure to temperatures below their lower critical limit (65% of variation); 32% was also explained by relative spleen mass. In males, FMR was best explained by the number of hours spent in nest site attendance and either relative spleen mass or liver concentrations of tetra-brominated diphenyl ethers (tetra-BDEs) (55% of variation). Relative spleen mass, as an important factor relating to FMR, was best explained by models with a combination of parasite abundance (Diplostomum for females and Eucoleus for males) in a negative relationship, and liver POP concentrations (p,p'-DDE for females and tetra-BDEs for males) in a positive relationship (34%, 55% of variation for females and males, respectively). This study demonstrates that immune activity may be an important factor affecting energy expenditure in ring-billed gulls, and that contaminants and parasite abundance may have both a direct and/or indirect influence on FMR.

Short-term fasts increase levels of halogenated flame retardants in tissues of a wild incubating bird

Many species are adapted for fasting during parts of their life cycle. For species undergoing extreme fasts, lipid stores are mobilized and accumulated contaminants can be released to exert toxicological effects. However, it is unknown if short-term fasting events may have a similar effect. The objective of this study was to determine if short successive fasts are related to contaminant levels in liver and plasma of birds. In ring-billed gulls (Larus delawarensis), both members of the pair alternate between incubating the nest for several hours (during which they fast) and foraging, making them a useful model for examining this question. Birds were equipped with miniature data loggers recording time and GPS position for two days to determine the proportion and duration of time birds spent in these two activities. Liver and plasma samples were collected, and halogenated flame retardants (HFRs) (PBDEs and dechlorane plus) and organochlorines (OCs) (PCBs, DDTs, and chlordane-related compounds) were determined. Most birds (79%) exhibited plasma lipid content below 1%, indicating a likely fasted state, and plasma lipid percent declined with the number of hours spent at the nest site. The more time birds spent at their nest site, the higher were their plasma and liver concentrations of HFRs. However, body condition indices were unrelated to either the amount of time birds fasted at the nest site or contaminant levels, suggesting that lipid mobilization might not have been severe enough to affect overall body condition of birds and to explain the relationship between fasting and HFR concentrations. A similar relationship between fasting and OC levels was not observed, suggesting that different factors are affecting short-term temporal variations in concentrations of these two classes of contaminants. This study demonstrates that short fasts can be related to increased internal contaminant exposure in birds and that this may be a confounding factor in research and monitoring involving tissue concentrations of HFRs in wild birds.

Sexual Size Dimorphism and Body Condition in the Australasian Gannet

Sexual size dimorphism is widespread throughout seabird taxa and several drivers leading to its evolution have been hypothesised. While the Australasian Gannet (Morus serrator) has previously been considered nominally monomorphic, recent studies have documented sexual segregation in diet and foraging areas, traits often associated with size dimorphism. The present study investigated the sex differences in body mass and structural size of this species at two colonies (Pope’s Eye, PE; Point Danger, PD) in northern Bass Strait, south-eastern Australia. Females were found to be 3.1% and 7.3% heavier (2.74 ± 0.03, n = 92; 2.67 ± 0.03 kg, n = 43) than males (2.66 ± 0.03, n = 92; 2.48 ± 0.03 kg, n = 43) at PE and PD, respectively. Females were also larger in wing ulna length (0.8% both colonies) but smaller in bill depth (PE: 2.2%; PD: 1.7%) than males. Despite this dimorphism, a discriminant function provided only mild accuracy in determining sex. A similar degree of dimorphism was also found within breeding pairs, however assortative mating was not apparent at either colony (R² < 0.04). Using hydrogen isotope dilution, a body condition index was developed from morphometrics to estimate total body fat (TBF) stores, where TBF(%) = 24.43+1.94*(body mass/wing ulna length) – 0.58*tarsus length (r² = 0.84, n = 15). This index was used to estimate body composition in all sampled individuals. There was no significant difference in TBF(%) between the sexes for any stage of breeding or in any year of the study at either colony suggesting that, despite a greater body mass, females were not in a better condition than males. While the driving mechanism for sexual dimorphism in this species is currently unknown, studies of other Sulids indicate segregation in foraging behaviour, habitat and diet may be a contributing factor.

Evidence for an intrinsic energetic ceiling in free-ranging kittiwakes Rissa tridactyla

1. The rate at which free-living animals can expend energy is limited but the causes of this limitation are not well understood. Theoretically, energy expenditure may be intrinsically limited by physiological properties of the animal constraining its capacity to process energy. Alternatively, the limitation could be set extrinsically by the amount of energy available in the environment or by a fitness trade-off in terms of reduced future survival associated with elevated metabolism. 2. We measured daily energy expenditure (DEE) using the doubly labelled water method in chick-rearing black-legged kittiwakes (Rissa tridactyla) at a study site close to the northern limit of their breeding range over 5 years. We measured breeding success, foraging trip duration and diet composition as proxies of resource availability during these years and estimated the probability of parent kittiwakes to return to the colony in relation to their energy expenditure in order to determine whether kittiwakes adjust their DEE in response to variation in prey availability and whether elevated DEE is associated with a decrease in adult survival. 3. We found that DEE was strikingly similar across all five study years. There was no evidence that energy expenditure was limited by resource availability that varied considerably among study years. Furthermore, there was no evidence of a negative effect of DEE on adult return rate, which does not support the hypothesis of a survival cost connected to elevated energy expenditure. 4. The additional lack of variation in DEE with respect to ambient temperature, brood size or between sexes suggests that kittiwakes at a time of peak energy demands may operate close to an intrinsic metabolic ceiling independent of extrinsic factors.

Organohalogen and metabolically-derived contaminants and associations with whole body constituents in Norwegian Arctic glaucous gulls

Comprehensive surveys of organohalogen contaminants have been conducted in various tissues and blood of glaucous gulls (Larus hyperboreus), a top scavenger-predator species in Svalbard in the Norwegian Arctic. However, the physico-chemical properties of organohalogens (e.g., type and degree of halogenation and the presence or absence of additional phenyl group substituents) that may influence toxicokinetics, and subsequently tissue-specific accumulation, have yet to be studied in this species. We investigated the concentrations, total body burdens, and compositional patterns of legacy chlorinated compounds (PCBs and chlordanes (CHLs)), metabolically-derived PCBs (methylsulfonyl (MeSO(2))- and OH-PCBs), brominated flame retardants (polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs), total-hexabromocyclododecane (HBCD)), and PBDE metabolites and/or naturally-occurring compounds with similar structures (MeO- and OH-PBDEs) in liver, blood and whole body homogenate samples of adult glaucous gulls (n=19) from Svalbard. Further, we examined the distribution of these organohalogens and metabolites in relation to whole body composition of glaucous gulls, i.e., the total water, protein, lipid and mineral contents in whole homogenate carcasses. The total body burden of organohalogens and metabolites in glaucous gulls ranged between 3.3 and 33.0 mg. Compound class distribution showed that the relative proportions of sum (Sigma) OH-PCB and SigmaOH-PBDE to the total organohalogen concentrations were significantly highest in blood. Conversely, the SigmaCHL and SigmaPCB showed generally higher proportions in the lipid-rich liver as well as in whole body homogenates. No significant difference in the compositional patterns of individual congeners/compounds was found among tissues/blood, with the exception of the classes comprised of less polar brominated compounds (PBDEs, PBBs and total-(alpha)-HBCD). Total proteins isolated from the whole body homogenates of glaucous gulls were significantly associated to the proportions of SigmaOH-PCB and SigmaPBDE. A non-significant positive association was found between total lipids and the SigmaPCB proportions. The present study suggests that both protein association and lipid solubility are important concomitant factors to be considered in the toxicokinetics and fate of contaminants as a function of chemical structure and properties, e.g., chlorination, bromination and the presence of other phenyl substituents such as OH group. An enhanced, selective retention of these organohalogen classes in given tissues/body compartments may thus lead to site-specific toxicological actions and adverse effects in the highly-contaminated Svalbard glaucous gulls.