Condition dependent strategies of egg size variation in the Common Eider Somateria mollissima.

We analysed intraclutch egg-size variation over the laying sequence in relation to clutch size, and the relation between clutch size and female body condition, in the Common Eider Somateria mollissima during an 8-year period. The aim was to assess if eiders adjusted egg size within the laying sequence depending on clutch sizes in response to body condition, as such an adjustment could have adaptive implications on reproductive success through a size advantage for the hatchlings. The analyses were performed on a population level; and then at the individual level using data from recaptured females that changed clutch size between years. Based on 1,099 clutches from 812 individual females, population clutch size averaged 4.13 eggs (range: 1-6), with 4- and 5-egg clutchesconstituting c.70% of all clutches, taking turns in being the most represented clutch size. Clutch size was positively related to female pre-laying body condition at both the population and individual levels. Egg size varied significantly within and between clutch sizes and changes were significantly related to the laying sequence. First eggs were significantly larger in 4-egg clutches and second eggs marginally smaller than in 5-egg clutches, a pattern also found among individual females changing clutch size between years. The relationship between female pre-laying body condition and clutch size, and the intraclutch egg-size pattern indicate that both clutch size and egg size are actively adapted to the pre-breeding body condition of the female. As egg size potentially optimise reproductive success through a size advantage in hatchlings, the observed pattern of intraclutch egg-size variation suggests that female eiders possesses a finely tuned conditional dependent mechanism that may optimize reproductive output in years were females are in suboptimal body condition for breeding.

Toxic lead gunshot persists accessible to waterbirds after a 33-year ban on their use.

Use of lead shot for hunting was banned under legislation on 26 Ramsar sites in Denmark from 1986, based on evidence of poisoning in waterbirds ingesting lead shot and high lead shot pellet densities in Danish wetland sediments caused by intensive hunting. To assess the fate of lead shot from hunting prior to 1986 and the degree to which such shot remains available to waterbirds, this study replicated the survey of shot pellet densities in substrates in Ringkøbing Fjord undertaken in the late 1970s. 287 shotgun pellets (282 lead, five steel) were recovered from 123 sediment samples at four locations, equivalent to a mean of 127 pellets m-2 in the top 20 cm of the sediment at the four locations, in certain hot spots equating to >250 kg lead ha-1, broadly similar to densities found in the 1970s. Possible explanations were given for the persistence of such high lead shot densities despite >30 years of regulation, during which time steel shot has been widely used as the alternative to lead. Field experiments showed that steel shot corroded in the marine environment, which likely contributes to lower steel shot densities found in this study. It is concluded that lead gunshot pellet dispersal and accumulation in natural ecosystems remains as a persistent and irreversible hazard to wildlife and ecosystems. Based on these Danish experiences, it is urgently recommended that international and national bodies in countries where hunting with lead shot continues recognise these results and act to prevent the accumulation of this toxic metal.

Problem-solving in a cooperative task in peach-fronted conures (Eupsittula aurea).

Cooperation is a complex behaviour found in many kinds of organisms and occurs between individuals of the same and different species. Several studies have examined the intentionality of this behaviour by testing the animals' understanding of the need for a partner when working in pairs. The mammalian species tested express such understanding, whereas most tested birds fail, especially when the test involves a delayed access to the setup by one of the co-operators. In the present study, the cooperative problem-solving capability of four peach-fronted conures (Eupsittula aurea) was investigated with the loose string test. All four parrots solved the paradigm by simultaneously pulling the ends of the same string to bring a platform with a food reward within reach. They were also capable of solving the task when one of the co-operators was delayed, even when visually isolated from each other. To further test their comprehension and to exclude the birds relying on task-associated cues, we video-recorded the trials and quantified possible cues and strategies for timing the pulling behaviour (e.g., sound of the partner's door when opening, sound of steps of partner approaching). The preferred cue to start pulling was to wait for their partner's arrival to the string. The number of vocalisations was significantly higher during visually isolated conditions and for successful trials compared to failed trials, suggesting possible information exchange. Our findings show that peach-fronted conures can solve a cooperative task, and that cooperation success is not determined by external cues or by partner identity or affinity.

Lead and Other Trace Elements in Danish Birds of Prey.

Lead is a widely used and toxic heavy metal that poses a serious hazard to wildlife species and their ecosystems. Lead is used for production of hunting ammunition. Via gunshot or rifle projectiles, it spreads in ecosystems and may end up in predators and scavengers feeding on wounded or dead animals shot with lead-based ammunition. To assess to what degree Danish raptors are subject to lead contamination, we measured the content of lead in liver tissue from Danish birds of prey (n = 137). Additionally, the study included values for 54 other trace elements. In our analysis, emphasis was put on interpretation of lead levels. Levels of cadmium, mercury and selenium were also discussed, while data for the remaining elements were provided for reference purposes. Bismuth was included to assess if lead originated from bismuth gunshot used as an alternative to lead shot. Concentrations of lead, cadmium, mercury and selenium were generally below the levels in similar studies of birds of prey in other northern European countries and none exceeded known and generally accepted threshold values for adverse health effects. As for lead, this is possibly related to the phase out of lead shot for hunting since 1986. The study confirms results from other studies showing that bismuth shot contains traces of lead that is deposited with bismuth in the target animal.

Danish pheasant and mallard hunters comply with the lead shot ban.

Denmark implemented a total ban on the use of lead shot for hunting and clay target shooting in 1996. Compliance was not studied systematically until recently. However, sporadic police checks and individual studies indicated that compliance was far from complete in the early years after regulation. To assess current levels of compliance with Danish regulations, we purchased 730 carcasses of pheasants (Phasianus colchicus) and mallards (Anas platyrhynchos) and a further 690 mallard gizzards were obtained from > 14 shooting events distributed across > 10 local authority districts throughout East and West Denmark in the 2016/2017 and 2017/2018 hunting seasons. All carcasses and gizzards were subject to radiography and those that contained shot were examined, pellets removed by dissection and identified to shot type. In all, 3589 pellets (intact or fragmented) were found in 1420 carcasses/gizzards, of which 799 pellets (some fragmented) were identified. Among the sample of pheasants with embedded shot (N = 447), 1.8% (in 2016) and 2.2% (in 2017) were lead shot. Among 148 mallards in 2017 with embedded shot, 3.1% had lead shot. None of the 2017 mallard gizzards had embedded lead shot. We conclude that Danish pheasant and mallard shooters mostly comply with the lead shot regulations. Steel was the most used non-lead alternative. The majority of ingested shot was non-lead, indicating that lead shot is not generally available to pheasant and mallard and suggesting compliance with regulations in recent years/decades. The study showed that the possibility to predict the metal composition of shot pellets from X-ray images alone was highly inaccurate, confirming the necessity of necropsy to determine shot type.

Does intensive goose grazing affect breeding waders?

Increasing goose population sizes gives rise to conflicts with human socioeconomic interests and in some circumstances conservation interests. Grazing by high abundances of geese in grasslands is postulated to lead to a very short and homogeneous sward height negatively affecting cover for breeding meadow birds and impacting survival of nests and chicks. We studied the effects of spring grazing barnacle geese Branta leucopsis and brent geese Branta bernicla on occupancy of extensively farmed freshwater grasslands by nesting and brood-rearing waders on the island Mandø in the Danish Wadden Sea. We hypothesized that goose grazing would lead to a shorter grass sward, negatively affecting the field occupancy by territorial/nesting and chick-rearing waders, particularly species preferring taller vegetation. Goose grazing led to a short grass sward (<5 cm height) over most of the island. To achieve a variation in sward height, we kept geese off certain fields using laser light. We analyzed effects of field size, sward height, mosaic structure of the vegetation, proximity to shrub as cover for potential predators, and elevation above ground water level as a measure of wetness on field occupancy by nesting and chick-rearing waders. The analysis indicated that the most important factor explaining field occupancy by nesting redshank Tringa totanus, black-tailed godwit Limosa limosa, oystercatcher Haematopus ostralegus and lapwing Vanellus vanellus as well as by chick-rearing black-tailed godwit and lapwing was short vegetation height. Distance to shrub cover and elevation were less important. Hence, despite very intensive goose grazing, we could not detect any negative effect on the field occupancy by nesting nor chick-rearing waders, including redshank and black-tailed godwit, which are known to favor longer vegetation to conceal their nests and hide their chicks. Possible negative effects may be buffered by mosaic structures in fields and proximity to taller vegetation along fences and ditches.

The number of neurons in specific amygdala regions is associated with boldness in mink: a study in animal personality.

Conspecifics vary consistently in their behavioural responses towards environment stimuli such as exposure to novel objects; ethologists often refer to this variability as animal personality. The neurological mechanisms underlying animal personality traits remain largely unknown, but linking the individual variation in emotional expression to brain structural and neurochemical factors is attracting renewed interest. While considerable research has focused on hormonal and neurotransmitter effects on behavioural responses, less is known about how individual variation in the number of specific neuron populations contributes to individual variation in behaviour. The basolateral amygdala (BLA) and the central nuclei of the amygdala (CeA) mediate emotional processing by regulating behavioural responses of animals in a potentially threatening situation. As such, these structures are good candidates for evaluating the relationship between neuronal populations and behavioural traits. We now show that individual American mink (Neovison vison) reacting more boldly towards novelty have more neurons in the BLA than do their more timid conspecifics, suggesting that a developmental pattern of the number of amygdala neurons can influence behavioural traits of an adult animal. Furthermore, post hoc correlations revealed that individuals performing with higher arousal, as reflected by their frequency of startle behaviour, have more CeA neurons. Our results support a direct link between the number of neurons in amygdala regions and aspects of animal personality.

Crude fucoidan content in two North Atlantic kelp species, Saccharina latissima and Laminaria digitata-seasonal variation and impact of environmental factors.

Fucoidans are sulphated fucose-rich polysaccharides predominantly found in the cell walls of brown algae. The bioactive properties of fucoidans attract increasing interest from the medico-pharmaceutical industries and may drive an increase in demand of brown algae biomass. In nature, the biochemical composition of brown algae displays a seasonal fluctuation driven by environmental factors and endogenous rhythms. To cultivate and harvest kelps with high yields of fucoidans, knowledge is needed on seasonal variation and impact of environmental conditions on the fucoidan content of brown algae. The relations between the fucoidan content and key environmental factors (irradiance, nutrient availability, salinity and exposure) were examined by sampling natural populations of the common North Atlantic kelps, Saccharina latissima and Laminaria digitata, over a full year at Hanstholm in the North Sea and Aarhus in the Kattegat. In addition, laboratory experiments were carried out isolating the effects of the single factors. The results demonstrated that (1) seasonal variation alters the fucoidan content by a factor of 2-2.6; (2) interspecific differences exist in the concentrations of crude fucoidan (% of dry matter): L. digitata (11%) > S. latissima (6%); and (3) the effects of single environmental factors were not consistent between species or between different conspecific populations. The ambiguous response to single environmental factors complicates prospective directions for manipulating an increased content of fucoidan in a cultivation scenario and emphasizes the need for knowledge on performance of local kelp ecotypes.

Mate choice screening in captive solitary carnivores: The role of male behavior and cues on mate preference and paternity in females of a model species, American mink (Neovison vison).

Mate choice studies suggest that choosy females benefit from increased fecundity, litter size, and offspring survival. Thus, providing females with the opportunity to choose among potential mates, deemed genetically suitable based on studbook data, might improve breeding management in production and zoo animals and thereby the sustainability of captive populations. Investigating mate preference via odor from potential mates before animal transfer is a proposed strategy for incorporating mate choice into breeding management. In this study, we test whether olfactory cues and signals from males can be used to assess and measure female mate preference in American mink. Eighteen females were subjected to a 4-day stimulus test in which females showed a preference for one of two males' urine and feces. Subsequently, each female was subjected to a 10-day mate preference test involving the same two males of the first test. Paternity tests revealed that 13 females had offspring, which could be assigned to only one male, suggesting that these females performed a mate choice. In nine of these females preference during the stimulus test was directed toward the male that fathered their offspring. Our results suggest that even though there was a preference difference in scent stimulus trials from potential mates this preference was not predictive of eventual mate preference or paternity. Other factors such as aspects of male behavior seem to play a role, when the mates are introduced. Our study supports that mate preference and mate choice are complex matters influenced by multiple cues and signals.

Context Matters: Multiple Novelty Tests Reveal Different Aspects of Shyness-Boldness in Farmed American Mink (Neovison vison).

Animal personality research is receiving increasing interest from related fields, such as evolutionary personality psychology. By merging the conceptual understanding of personality, the contributions to both fields of research may be enhanced. In this study, we investigate animal personality based on the definition of personality traits as underlying dispositional factors, which are not directly measurable, but which predispose individuals to react through different behavioural patterns. We investigated the shyness-boldness continuum reflected in the consistency of inter-individual variation in behavioural responses towards novelty in 47 farmed American mink (Neovison vison), which were raised in identical housing conditions. Different stages of approach behaviour towards novelty, and how these related within and across contexts, were explored. Our experimental design contained four tests: two novel object tests (non-social contexts) and two novel animated stimuli tests (social contexts). Our results showed consistency in shyness measures across multiple tests, indicating the existence of personality in farmed American mink. It was found that consistency in shyness measures differs across non-social and social contexts, as well as across the various stages in the approach towards novel objects, revealing that different aspects of shyness exist in the farmed American mink. To our knowledge this is the first study to reveal aspects of the shyness-boldness continuum in the American mink. Since the mink were raised in identical housing conditions, inherited factors may have been important in shaping the consistent inter-individual variation. Body weight and sex had no effect on the personality of the mink. Altogether, our results suggest that the shyness-boldness continuum cannot be explained by a simple underlying dispositional factor, but instead encompasses a broader term of hesitating behaviour that might comprise several different personality traits.