A Chromosome-Level Reference Genome for the Black-Legged Kittiwake (Rissa tridactyla), a Declining Circumpolar Seabird.

Amidst the current biodiversity crisis, the availability of genomic resources for declining species can provide important insights into the factors driving population decline. In the early 1990s, the black-legged kittiwake (Rissa tridactyla), a pelagic gull widely distributed across the arctic, subarctic, and temperate zones, suffered a steep population decline following an abrupt warming of sea surface temperature across its distribution range and is currently listed as Vulnerable by the International Union for the Conservation of Nature. Kittiwakes have long been the focus for field studies of physiology, ecology, and ecotoxicology and are primary indicators of fluctuating ecological conditions in arctic and subarctic marine ecosystems. We present a high-quality chromosome-level reference genome and annotation for the black-legged kittiwake using a combination of Pacific Biosciences HiFi sequencing, Bionano optical maps, Hi-C reads, and RNA-Seq data. The final assembly spans 1.35 Gb across 32 chromosomes, with a scaffold N50 of 88.21 Mb and a BUSCO completeness of 97.4%. This genome assembly substantially improves the quality of a previous draft genome, showing an approximately 5× increase in contiguity and a more complete annotation. Using this new chromosome-level reference genome and three more chromosome-level assemblies of Charadriiformes, we uncover several lineage-specific chromosome fusions and fissions, but find no shared rearrangements, suggesting that interchromosomal rearrangements have been commonplace throughout the diversification of Charadriiformes. This new high-quality genome assembly will enable population genomic, transcriptomic, and phenotype-genotype association studies in a widely studied sentinel species, which may provide important insights into the impacts of global change on marine systems.

Sex-specific responses to GnRH challenge, but not food supply, in kittiwakes: Evidence for the "sensitivity to information" hypothesis.

Seasonal timing of breeding is usually considered to be triggered by endogenous responses linked to predictive cues (e.g., photoperiod) and supplementary cues that vary annually (e.g., food supply), but social cues are also important. Females may be more sensitive to supplementary cues because of their greater role in reproductive timing decisions, while males may only require predictive cues. We tested this hypothesis by food-supplementing female and male colonial seabirds (black-legged kittiwakes, Rissa tridactyla) during the pre-breeding season. We measured colony attendance via GPS devices, quantified pituitary and gonadal responses to gonadotropin releasing hormone (GnRH) challenge, and observed subsequent laying phenology. Food supplementation advanced laying phenology and increased colony attendance. While female pituitary responses to GnRH were consistent across the pre-breeding season, males showed a peak in pituitary sensitivity at approximately the same time that most females were initiating follicle development. The late peak in male pituitary response to GnRH questions a common assumption that males primarily rely on predictive cues (e.g., photoperiod) while females also rely on supplementary cues (e.g., food availability). Instead, male kittiwakes may integrate synchronising cues from their social environment to adjust their reproductive timing to coincide with female timing.

Point-of-care blood analyzers measure the nutritional state of eighteen free-living bird species.

Point-of-care devices offer the potential to democratize a suite of physiological endpoints and assess the nutritional state of wild animals through plasma metabolite profiling. Measurements of plasma metabolites typically occur on frozen tissue in the laboratory, thus dissociating measurements from field observations. Point-of-care devices, widely used in veterinary and human medicine, provide rapid results (seconds or minutes) allowing in situ measurements of wild animals in remote areas without the need for access to freezers. Using point-of-care devices, we measured glucose, triglyceride, cholesterol and ß-hydroxybutyrate levels in plasma from 18 wild bird species spanning nine families and three orders. The values from six different point-of-care devices correlated strongly with one another, and with traditional laboratory measurements from stored plasma (R2 = 0.70-0.90). Although POC devices provided accurate relative values in wild birds, absolute values varied from laboratory measurements by up to 50% illustrating the need for calibration equations. Furthermore, three case studies showed the potential for point-of-care devices at research stations where participants do not have access to a lab and sample preservation is difficult: (i) at a remote seabird colony, birds that were provided with supplemental food had higher levels of glucose and lower ß-hydroxybutyrate and cholesterol levels than unfed birds, suggesting they were in a better nutritional state; (ii) at a migration monitoring station, levels of triglycerides of two migratory songbirds increased with time of day, implying that they were fattening during stopover; and (iii) for diving seabirds, individuals that worked harder (shorter surface intervals) had higher glucose and lower ß-hydroxybutyrate implying that nutritional state is an index of foraging effort and success. We demonstrate that point-of-care devices, once validated, can provide accurate measurements of the nutritional state of wild birds. Such real-time measurements can aid in ecological research and monitoring, care of wildlife at rehabilitation centres, and in veterinary medicine of exotics.

Yolk androstenedione in domestic chicks (Gallus gallus domesticus): uptake and sex-dependent alteration of growth and behavior.

In birds, causes and consequences of variation in maternally-derived steroids in egg yolk have been the subject of intense experimentation. Many studies have quantified or manipulated testosterone ("T") and one of its immediate precursors, androstenedione ("A4") - often lumping the two steroids as "androgens" and treating them as functionally equivalent. However, yolk A4 is deposited in substantially higher concentrations than T, binds only weakly to the androgen receptor, and is readily converted into either T or estrone by steroidogenic enzymes present during embryonic development. Thus it may not be appropriate to assume that A4 has the same effect as T. In addition, A4's metabolic fate is likely to differ between females and males. The goals of this study were to examine the sex-specific uptake and metabolism of yolk A4 and consequences of elevated levels of yolk A4 on development and behavior of domestic chicks. Eggs were injected with 2µ Ci of tritiated androstenedione; radioactivity was detected in all tissues of day 7 and day 16 embryos and found in both aqueous and organics phases of day 7 yolk, with no difference between sexes. A second set of eggs was injected with 125ng of A4. A4 increased growth of morphological traits (tarsus, beak) in females, but not males. A4 males had smaller combs than controls; there was no treatment effect in females. A4 reduced tonic immobility behavior in both sexes. The results of this study illustrate the importance of distinguishing both between androgens and between sexes when investigating avian endocrine maternal effects.

Are yolk androgens adjusted to environmental conditions? A test in two seabirds that lay single-egg clutches.

It is widely believed that female birds strategically allocate androgens to yolk in the manner that best equips offspring for feeding conditions during their development. Because most avian studies have focused on multi-egg clutch species, and interpreted results within the framework of sibling competition, we still know little about how yolk androgens might be allocated in direct response to environmental conditions. Most oceanic birds are long-lived and lay single-egg clutches, and their breeding success is tightly linked to highly variable marine production. That combination: a variable breeding environment, long lives, and single-egg clutches, makes oceanic birds good subjects to test hypotheses about yolk androgen allocation strategies. We measured concentrations of two yolk androgens, androstenedione (A4) and testosterone (T), in the single-egg clutches laid by early-laying Cassin's (Ptychoramphus aleuticus) and rhinoceros (Cerorhinca monocerata) auklets at Triangle Island, British Columbia, Canada, in 2002-2004. Environmental conditions including sea-surface temperatures and the timing and intensity of marine primary production varied over the 3 years, and in response, both the timing and success of seabird breeding varied. As in other avian species, concentrations of A4 and T varied markedly among individual eggs in both species (by factors of 3-8), yet contrary to expectation, little of the variation could be attributed to year effects. The high interindividual variation and the lack of interannual variation suggest a non-adaptive explanation for yolk androgen deposition relative to environmental conditions in these species.

Steroids in allantoic waste: an integrated measure of steroid exposure in ovo.

Recent studies examining patterns and consequences of variation in maternally deposited steroids in avian egg yolk have demonstrated that these maternal hormones can have dramatic effects on chick phenotypes. However, maternal steroids are not the only source for avian embryos, which activate endocrine axes relatively early in development and are capable of producing substantial amounts of endogenous steroids. Although organizational effects of steroids have been demonstrated, the interactions between steroids from yolk and endogenous production have not been addressed. Steroids in the yolk are likely to alter development of the embryo's endocrine axes. The ability to assess total steroid exposure in ovo in a nonlethal fashion would improve our understanding of these interactions and help elucidate the mechanisms by which maternal steroids alter chick phenotype. Steroid levels in allantoic waste provide a cumulative measure of steroids excreted in ovo and may prove to be a useful tool. We present data from semiprecocial seabirds, common murres, demonstrating the presence of detectable steroids in allantoic waste and suggesting that some reflect differences in timing of hatching and may provide information about aspects of chick phenotype.

Increased sensitivity of the serotonergic system during the breeding season in free-living American tree sparrows.

In order to understand the physiological role of serotonin in regulating aggressive behaviour it is important to understand how this neuromodulator acts within the context of a naturally fluctuating social and physical environment. To accomplish this, we examined the effect of the selective serotonin reuptake inhibitor fluoxetine during the breeding season in free-living male American tree sparrows (Spizella arborea) in Northern Alaska. During this time period males are maximally aggressive towards territorial intruders. Male, territorial sparrows were injected with either vehicle or a 10 mg/kg dose of fluoxetine. One hour later, aggression was measured using a simulated territorial intrusion. Depending upon when birds were sampled, the aggression scores for vehicle and fluoxetine treatments were grouped according to the number of days after territorial behaviour was initiated. The three groups were: early, days 1-5; middle, days 6-10; and late, days 11-15. There was a significant overall difference between groups (F(5,36)=5.18, P<0.0015). Post hoc analysis demonstrated that the level of aggression did not differ between the three groups of saline injected birds. However, fluoxetine injected birds showed a time dependent decrease in aggression. When compared to control birds the middle and late fluoxetine groups had significantly less aggression. Furthermore, the late group of fluoxetine treated birds were significantly less aggressive than the early group of fluoxetine birds. This demonstrates that free-living male ATSPs show a rapid change in their behavioural response to fluoxetine across the first 2 weeks of the breeding season. The rapidity of the change in responsiveness suggests a dynamic sensitivity of the serotonergic system.