Keywords: Birds

“Millions have been released.” Hawaii’s beautiful birds are dying. But scientists have a controversial plan to save them

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James Fair,  BBC Wildlife Magazine,  2026-02-24 09:58:30.
About 6-7 million years ago, common rosefinches – which are today found across a vast expanse of northern Eurasia and are even occasional winter visitors to the British Isles – island-hopped their way from the Russian Far East across the Pacific Ocean and arrived in the newly formed, volcanic land masses of Hawaii. There, a single species evolved into an extended family of 56 Hawaiian honeycreepers, many of which only barely resemble their pioneering ancestor. Take, for example, the gorgeous scarlet honeycreeper or i’iwi, with its huge downward curving bill that is perfectly adapted for extracting nectar from endemic Hawaiian flowers. At first glance, it looks nothing like a finch. It’s an amazing story, but also a tragic one, because according to the US Fish & Wildlife Service, 39 of Hawaii’s honeycreepers are extinct, and 11 of the remaining 17 are threatened. One of the biggest factors in this natural history catastrophe is avian malaria. Neither the single-celled organism that causes malaria, nor the mosquito that transmits it, are native to Hawaii, so honeycreepers and other endemic birds have almost no immunity to it. All conservationists agree that something needs to be done – and quickly – if we are to save those that remain. Step forward scientists such as Tim Harvey-Samuel, an expert in arthropod genetics at the University of Keele. Harvey-Samuel and his team are seeing whether they can “modify the mosquito population in Hawaii such that it’s no longer able to transmit avian malaria.” The idea is to insert a gene into the mosquito (Culex quinquefasciatus) so that it doesn’t allow the Plasmodium protozoan that causes malaria to complete its life-cycle.

Judge sides with Hawaii to block challenge to mosquito release plan

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Candice Cheung,  Courthouse News Service,  2024-02-27 16:29:17.
A planned program to save endemic Hawaiian birds from avian malaria by releasing thousands of biopesticide mosquitoes into Maui’s rainforest will go on, despite an attempt by an environmental nonprofit to block the project.First Circuit Court Judge John Tonaki ruled Tuesday in favor of the state of Hawaii, its Department of Land and Natural Resources and conservationists to block a lawsuit claiming the state agency did not complete a proper environmental evaluation of program aimed at curbing mosquito population to prevent them from spreading avian malaria.“This is a victory for our endangered forest birds who some native Hawaiians consider their ancestors,” Dawn Chang, chair of the state’s Board of Land and Natural Resources said in a statement. “The HEPA is an important tool that enables decisionmakers to assess environmental impacts — not the sword by which misinformation kills a project, aimed at saving native species.”

Millions of Mosquitoes Will Rain Down on Hawaii to Save an Iconic Bird

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S. Wild,  Scientific American,  2023-10-06 06:53:13.
Millions of mosquitoes dropped from helicopters could be the greatest hope for Hawaii’s iconic honeycreepers. At least four species of the brightly colored birds could go extinct within the year if no action is taken to save them. “We’re seriously in a race against time at the moment,” says Hanna Mounce, program manager of the Maui Forest Bird Recovery Project. These small birds evolved on the islands over the course of millions of years and are uniquely adapted to their niche habitat, where they are crucial pollinators for many of Hawaii’s flora. For the people of Hawaii, the honeycreepers are also woven into the cultural fabric, featuring prominently in many legends and providing feathers for traditional garments. More than 50 species of honeycreepers once flitted across the archipelago, but because of introduced predators, habitat destruction and disease, that number has dwindled to only 17. Invasive Culex quinquefasciatus mosquitoes—possibly introduced via water barrels on European ships in the early 19th century—pose a particular threat because they spread the deadly avian malaria parasite.IIT works like this: C. quinquefasciatus mosquitoes, as well as many other arthropods, naturally contain Wolbachia bacteria in their gut. In order to produce offspring together, mating mosquitoes must be infected with the same strain of the bacteria. Birds, Not Mosquitoes’ plan involves releasing male mosquitoes bred by Verily Life Sciences—the life sciences research arm of Alphabet, which also owns Google. These mosquitos will host a different Wolbachia strain than those on Maui. The idea is that the existing female mosquitoes will mate with the male newcomers, but because of their incompatible Wolbachia bacteria, they will not produce viable offspring. If all goes according to plan, the overall mosquito population will plummet.

East Maui project hopes mosquito v. mosquito mating battle will save endangered birds

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K. Cerizo,  MAUINOW,  2022-12-11 11:03:34.

Mendelian nightmares: the germline-restricted chromosome of songbirds

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P. Borodin, A. Chen, W. Forstmeier, S. Fouché, L. Malinovskaya, Y. Pei, R. Reifová, F. J. Ruiz-Ruano, S. A. Schlebusch, M. Sotelo-Muñoz, A. Torgasheva, N. Vontzou and A. Suh,  Chromosome Res,  2022-04-13 09:33:56.
Germline-restricted chromosomes (GRCs) are accessory chromosomes that occur only in germ cells. They are eliminated from somatic cells through programmed DNA elimination during embryo development. GRCs have been observed in several unrelated animal taxa and show peculiar modes of non-Mendelian inheritance and within-individual elimination. Recent cytogenetic and phylogenomic evidence suggests that a GRC is present across the species-rich songbirds, but absent in non-passerine birds, implying that over half of all 10,500 bird species have extensive germline/soma genome differences. Here, we review recent insights gained from genomic, transcriptomic, and cytogenetic approaches with regard to the genetic content, phylogenetic distribution, and inheritance of the songbird GRC. While many questions remain unsolved in terms of GRC inheritance, elimination, and function, we discuss plausible scenarios and future directions for understanding this widespread form of programmed DNA elimination.

A test for meiotic drive in hybrids between Australian and Timor zebra finches

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U. Knief, W. Forstmeier, Y. Pei, J. Wolf and B. Kempenaers,  Ecology and Evolution,  2020-11-03 16:16:43.
We did not find evidence for meiotic driver loci on specific chromosomes. However, we observed a weak overall transmission bias toward Timor alleles at centromeres in females (transmission probability of Australian alleles of 47%, nominal p = 6 ? 10?5). While this is in line with the centromere drive theory, it goes against the expectation that the subspecies with the larger effective population size (i.e., the Australian zebra finch) should have evolved the more potent meiotic drivers. We thus caution against interpreting our finding as definite evidence for centromeric drive. Yet, weak centromeric meiotic drivers may be more common than generally anticipated and we encourage further studies that are designed to detect also small effect meiotic drivers.

A Framework for the risk assessment and management of gene drive technology in contained use

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van der Vlugt, CJBB, David D.; Lehmann, Kathleen; Leunda, Amaya; Willemarck, Nicolas,  Applied Biosafety,  23:25-31. 2018-01-21 00:00:00.
The utilisation of the CRISPR/Cas9 technology has sparked a renewed interest in gene drive mechanisms. These mechanisms of biased inheritance may yield promising applications in the fields of vector control and nature conservation. However, the same properties that will enable these applications may also pose a risk if organisms that are equipped with gene drive cassettes are unintentionally released into the environment. Although several groups of scientists and regulators have started to address these safety concerns, there are currently no dedicated guidelines published on the required risk assessment and minimal control measures applicable to gene drive organisms in contained use. To fill this gap, this paper describes a fundamental approach to assessing the risks of these organisms while handled in a contained laboratory environment. Based on the likelihood that an adverse effect will arise from the handling of a gene drive organism and the severity of this effect, three risk classes for contained use activities are presented. Finally, specific minimum requirements regarding physical measures and working practices are proposed according to the presented risk classes and tailored to activities with rodents, insects, and fungi, which are most likely to be used for gene drive applications in the near future.

How Genetically Modified Mice Could One Day Save Island Birds

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Borel, B,  Audubon,  2017-06-07 00:00:00.
The silent black-and-white footage opens on a seemingly tranquil setting: a burrow where an Atlantic Petrel tends to its chick. Then mice begin scurrying in and out of frame. The dark blurs jostle the adult, darting up to the exposed chick and tearing off bloody bites. They’re eating it alive.; ; The horrific scene is captured by nest cams on Gough (rhymes with “off”), a rugged volcanic island about 1,700 miles west of South Africa. It has one of the world’s largest seabird nesting colonies, with millions of birds representing 22 species. It’s also home to hundreds of thousands of mice, descendants of stowaways on 19th-century seal-hunting ships. The tiny predators devour some 900,000 chicks a year and threaten to decimate the island’s Atlantic Petrels and Tristan Albatrosses, which breed here almost exclusively. In a rodent-free landscape, more than two-thirds of the albatross chicks should make it to adulthood; on Gough, mice cut survival to as low as 10 percent.

Re-Coding for Conservation

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Hawkes, A,  Bay Nature Magazine,  2016-06-27 00:00:00.
very year, as summer turns to fall, the mouse population on the South Farallon Islands explodes to plague-like densities, numbering 490 mice per acre, among the highest found on any island in the world. The scientists who live and work there describe the assault of the invasive house mouse as a kind of purgatory in the otherwise stunning, windswept smattering of rocky islets and sea stacks 30 miles outside the Golden Gate. “At night they would be everywhere,” says Peter Pyle, a wildlife biologist who spent more than 20 fall seasons living at the research station on Southeast Farallon Island. “I had them crawling on top of me at night and in my hair. I tried to mouse-proof the house but we’d catch 50 mice in the night.”

The dawn of active genetics

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Gantz, VMB, E.,  Bioessays,  38:50-63. 2016-01-03 00:00:00.
On December 18, 2014, a yellow female fly quietly emerged from her pupal case. What made her unique was that she had only one parent carrying a mutant allele of this classic recessive locus. Then, one generation later, after mating with a wild-type male, all her offspring displayed the same recessive yellow phenotype. Further analysis of other such yellow females revealed that the construct causing the mutation was converting the opposing chromosome with 95% efficiency. These simple results, seen also in mosquitoes and yeast, open the door to a new era of genetics wherein the laws of traditional Mendelian inheritance can be bypassed for a broad variety of purposes. Here, we consider the implications of this fundamentally new form of active genetics, its applications for gene drives, reversal and amplification strategies, its potential for contributing to cell and gene therapy strategies, and ethical/biosafety considerations associated with such active genetic elements.

A prezygotic transmission distorter acting equally in female and male zebra finches Taeniopygia guttata

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Knief, US, H.; Ellegren, H.; Kempenaers, B.; Forstmeier, W.,  Molecular Ecology,  24:3846-3859. 2015-01-18 00:00:00.
The two parental alleles at a specific locus are usually inherited with equal probability to the offspring. However, at least three processes can lead to an apparent departure from fair segregation: early viability selection, biased gene conversion and various kinds of segregation distortion. Here, we conduct a genome-wide scan for transmission distortion in a captive population of zebra finches (Taeniopygia guttata) using 1302 single-nucleotide polymorphisms (SNPs) followed by confirmatory analyses on independent samples from the same population. In the initial genome-wide scan, we found significant distortion at three linked loci on chromosome Tgu2 and we were able to replicate this finding in each of two follow-up data sets [overall transmission ratio=0.567 (95% CI=0.536-0.600), based on 1101 informative meioses]. Although the driving allele was preferentially transmitted by both heterozygous females [ratio=0.560 (95% CI=0.519-0.603)] and heterozygous males [ratio=0.575 (95% CI=0.531-0.623)], we could rule out postzygotic viability selection and biased gene conversion as possible mechanisms. Early postzygotic viability selection is unlikely, because it would result in eggs with no visible embryo and hence no opportunity for genotyping, and we confirmed that both females and males heterozygous for the driving allele did not produce a larger proportion of such eggs than homozygous birds. Biased gene conversion is expected to be rather localized, while we could trace transmission distortion in haplotypes of several megabases in a recombination desert. Thus, we here report the rare case of a prezygotically active transmission distorter operating equally effectively in female and male meioses.

Multiple sex chromosomes in the light of female meiotic drive in amniote vertebrates

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Pokorna, MA, M.; Kratochvil, L.,  Chromosome Research,  22:35-44. 2014-01-11 00:00:00.
It is notable that the occurrence of multiple sex chromosomes differs significantly between major lineages of amniote vertebrates. In this respect, birds are especially conspicuous, as multiple sex chromosomes have not been observed in this lineage so far. On the other hand, in mammals, multiple sex chromosomes have evolved many times independently. We hypothesize that this contrast can be related to the different involvement of sex-specific sex chromosomes in female meiosis subjected to the female meiotic drive under male versus female heterogamety. Essentially, the male-specific Y chromosome is not involved in female meiosis and is therefore sheltered against the effects of the female meiotic drive affecting the X chromosome and autosomes. Conversely, the Z and W sex chromosomes are both present in female meiosis. Nonrandom segregation of these sex chromosomes as a consequence of their rearrangements connected with the emergence of multiple sex chromosomes would result in a biased sex ratio, which should be penalized by selection. Therefore, the emergence of multiple sex chromosomes should be less constrained in the lineages with male rather than female heterogamety. Our broader phylogenetic comparison across amniotes supports this prediction. We suggest that our results are consistent with the widespread occurrence of female meiotic drive in amniotes.

Guidance on the environmental risk assessment of genetically modified animals

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European Food Safety Authority,  European Food Safety Authority,  2013-05-23 20:45:04.
This document describes the six sequential steps for the ERA of GM animals, as indicated in Directive 2001/18/EC: (1) problem formulation including hazard and exposure identification; (2) hazard characterisation; (3) exposure characterisation; (4) risk characterisation; (5) risk management strategies; and (6) an overall risk evaluation. The Scientific Panel on Genetically Modified Organisms of the European Food Safety Authority follows Annex II of Directive 2001/18/EC, considering specific areas of risk to be addressed by applicants and risk assessors during the ERA of GM fish, GM insects and GM mammals and birds.

Segregation distortion in chicken and the evolutionary consequences of female meiotic drive in birds

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Axelsson, EA, A.; Van, A. P.; Li, L.; Megens, H. J.; Vereijken, A. L. J.; Crooijmans, Rpma; Groenen, M. A. M.; Ellegren, H.; Willerslev, E.; Nielsen, R.,  Heredity,  105:290-298. 2010-01-11 00:00:00.
As all four meiotic products give rise to sperm in males, female meiosis result in a single egg in most eukaryotes. Any genetic element with the potential to influence chromosome segregation, so that it is preferentially included in the egg, should therefore gain a transmission advantage; a process termed female meiotic drive. We are aware of two chromosomal components, centromeres and telomeres, which share the potential to influence chromosome movement during meioses and make the following predictions based on the presence of female meiotic drive: (1) centromere-binding proteins should experience rapid evolution as a result of a conflict between driving centromeres and the rest of the genome; and (2) segregation patterns should be skewed near centromeres and telomeres. To test these predictions, we first analyze the molecular evolution of seven centromere-binding proteins in nine divergent bird species. We find strong evidence for positive selection in two genes, lending support to the genomic conflict hypothesis. Then, to directly test for the presence of segregation distortion, we also investigate the transmission of B9000 single-nucleotide polymorphisms in 197 chicken families. By simulating fair Mendelian meioses, we locate chromosomal regions with statistically significant transmission ratio distortion. One region is located near the centromere on chromosome 1 and a second region is located near the telomere on the p-arm of chromosome 1. Although these observations do not provide conclusive evidence in favour of the meiotic drive/genome conflict hypothesis, they do lend support to the hypothesis that centromeres and telomeres drive during female meioses in chicken. Heredity (2010) 105, 290-298; doi:10.1038/hdy.2009.193; published online 27 January 2010

Testosterone has a long-term effect on primary sex ratio of first eggs in pigeons-in search of a mechanism

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Goerlich, VCD, C.; Schaafsma, S. M.; Groothuis, T. G. G.,  General and Comparative Endocrinology,  163:184-192. 2009-01-21 00:00:00.
Despite accumulating evidence that birds, in which females are the heterogametic sex, are able to manipulate primary offspring sex ratio, the underlying mechanism remains elusive. Steroid hormones. which govern female reproduction and are also accumulated by the developing follicle could potentially affect primary sex ratio by differential follicle development in relation to future sex and meiotic drive, or by sex specific influence on oocyte abortion or fertilization. So far, experimental results on the involvement of maternal testosterone (T) in offspring sex manipulation are ambiguous. To investigate the effect of T on primary sex ratio and elucidate underlying mechanisms, we elevated circulating T levels in female homing pigeons (Columba livia). During the course of the experiment females produced three clutches-before and during T implantation, and one year after implant removal. Intriguingly, first eggs, but not second eggs of T females were significantly male biased relative to sham-implanted controls. One year after cessation of the treatment the male bias was still present, indicating long-term effects on female reproductive physiology. T treatment did not affect maternal body condition, nor was body condition correlated with offspring sex ratio. Our data on timing of oviposition, lack of infertile eggs, and yolk weight indicate a possible role for sex specific follicle abortion, perhaps in combination with meiotic drive. However, despite T treatment elevating maternal plasma levels, egg yolk T concentrations did not differ between treatment groups and did not vary with embryo sex, suggesting that yolk T is not involved in meiotic drive. (C) 2009 Elsevier Inc. All rights reserved.

Broadening the application of evolutionarily based genetic pest management

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Gould, F,  Evolution,  62:500-510. 2008-01-15 00:00:00.
Insect- and tick-vectored diseases such as malaria, dengue fever, and Lyme disease cause human suffering, and current approaches for prevention are not adequate. Invasive plants and animals such as Scotch broom, zebra mussels, and gypsy moths continue to cause environmental damage and economic losses in agriculture and forestry Rodents transmit diseases and cause major pre- and postharvest losses, especially in less affluent countries. Each of these problems might benefit from the developing field of Genetic Pest Management that is conceptually based on principles of evolutionary biology This article briefly describes the history of this field, new molecular tools in this field, and potential applications of those tools. There will be a need for evolutionary biologists to interact with researchers and practitioners in a variety of other fields to determine the most appropriate targets for genetic pest management, the most appropriate methods for specific targets, and the potential of natural selection to diminish the effectiveness of genetic pest management. In addition to producing environmentally sustainable pest management solutions, research efforts in this area could lead to new insights about the evolution of selfish genetic elements in natural systems and will provide students with the opportunity to develop a more sophisticated understanding of the role of evolutionary biology in solving societal problems.

Meiotic drive and sex determination: molecular and cytological mechanisms of sex ratio adjustment in birds

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Rutkowska, JB, A. V.,  Philosophical Transactions of the Royal Society B-Biological Sciences,  363:1675-1686. 2008-01-04 00:00:00.
Differences in relative fitness of male and female offspring across ecological and social environments should favour the evolution of sex-determining mechanisms that enable adjustment of brood sex ratio to the context of breeding. Despite the expectation that genetic sex determination should not produce consistent bias in primary sex ratios, extensive and adaptive modifications of offspring sex ratio in relation to social and physiological conditions during reproduction are often documented. Such discordance emphasizes the need for empirical investigation of the proximate mechanisms for modifying primary sex ratios, and suggests epigenetic effects on sex-determining mechanisms as the most likely candidates. Birds, in particular, are thought to have an unusually direct opportunity to modify offspring sex ratio because avian females are heterogametic and because the sex-determining division in avian meiosis occurs prior to ovulation and fertilization. However, despite evidence of strong epigenetic effects on sex determination in pre-ovulatory avian oocytes, the mechanisms behind such effects remain elusive. Our review of molecular and cytological mechanisms of avian meiosis uncovers a multitude of potential targets for selection on biased segregation of sex chromosomes, which may reflect the diversity of mechanisms and levels on which such selection operates in birds. Our findings indicate that pronounced differences between sex chromosomes in size, shape, size of protein bodies, alignment at the meiotic plate, microtubule attachment and epigenetic markings should commonly produce biased segregation of sex chromosomes as the default state, with secondary evolution of compensatory mechanisms necessary to maintain unbiased meiosis. We suggest that it is the epigenetic effects that modify such compensatory mechanisms that enable context-dependent and precise adjustment of primary sex ratio in birds. Furthermore, we highlight the features of avian meiosis that can be influenced by maternal hormones in response to environmental stimuli and may account for the precise and adaptive patterns of offspring sex ratio adjustment observed in some species.

Bewildering Bs – An impression of the 1st B-chromosome conference

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Beukeboom, LW,  Heredity,  73:328-336. 1994-01-06 00:00:00.
Ever since their first discovery B chromosomes have attracted attention. Why are they so appealing? The standard chromosomes of an organism are A chromosomes; B chromosomes are extra to this normal complement. In the B chromosome 'bible' (Jones & Rees, 1982) Bs are defined as dispensable supernumerary chromosomes that are not homologous and do not pair with A chromosomes. They have been further characterized as (1) morphologically different from As (usually smaller), (2) being inherited in a nonMendelian fashion, (3) not (or only rarely) having nucleolus organisers, (4) often displaying nondisjunction at anaphase of mitosis resulting in frequencies varying between organs in the same individual, (5) reducing fertility and growth when present in high numbers, and (6) carrying no genes with major effects. These features of Bs were recently discussed at an international conference and the main ideas presented by the participants are reported here. From 21 to 25 September 19