[{"command":"settings","settings":{"ajaxPageState":{"theme":"hm_theme","theme_token":"IPZMPqmdYcrTjnpfscpR_IVmjm-9jP5ybHjUkKLwhbA","libraries":"eJwDAAAAAAE"},"ajaxTrustedUrl":{"form_action_p_pvdeGsVG5zNF_XLGPTvYSKCf43t8qZYSwcfZl2uzM":true},"pluralDelimiter":"\u0003","user":{"uid":0,"permissionsHash":"2af85631393b514cbde3779a1f71d92618d53b94b54ea1960d28b2e2d121ff12"}},"merge":true},{"command":"openDialog","selector":"#drupal-modal","settings":null,"data":"\u003Cdiv id=\u0022republish_modal_form\u0022\u003E\u003Cform class=\u0022modal-form-example-modal-form ecl-form\u0022 data-drupal-selector=\u0022modal-form-example-modal-form\u0022 action=\u0022\/en\/article\/modal\/6998\u0022 method=\u0022post\u0022 id=\u0022modal-form-example-modal-form\u0022 accept-charset=\u0022UTF-8\u0022\u003E\u003Cp\u003EHorizon articles can be republished for free under the Creative Commons Attribution 4.0 International (CC BY 4.0) licence.\u003C\/p\u003E\n \u003Cp\u003EYou must give appropriate credit. We ask you to do this by:\u003Cbr \/\u003E\n 1) Using the original journalist\u0027s byline\u003Cbr \/\u003E\n 2) Linking back to our original story\u003Cbr \/\u003E\n 3) Using the following text in the footer: This article was originally published in \u003Ca href=\u0027#\u0027\u003EHorizon, the EU Research and Innovation magazine\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003ESee our full republication guidelines \u003Ca href=\u0027\/horizon-magazine\/republish-our-stories\u0027\u003Ehere\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003EHTML for this article, including the attribution and page view counter, is below:\u003C\/p\u003E\u003Cdiv class=\u0022js-form-item form-item js-form-type-textarea form-item-body-content js-form-item-body-content ecl-form-group ecl-form-group--text-area form-no-label ecl-u-mv-m\u0022\u003E\n \n\u003Cdiv\u003E\n \u003Ctextarea data-drupal-selector=\u0022edit-body-content\u0022 aria-describedby=\u0022edit-body-content--description\u0022 id=\u0022edit-body-content\u0022 name=\u0022body_content\u0022 rows=\u00225\u0022 cols=\u002260\u0022 class=\u0022form-textarea ecl-text-area\u0022\u003E\u003Ch2\u003EBird immune systems reveal harshness of city life\u003C\/h2\u003E\u003Cp\u003EResearchers have found that many internal defence mechanisms that are quiet in rural birds are much more active in those in cities. These biological pathways are pumping out extra antioxidants, immune system cells and detoxifiers \u2013 a sign that urban life is challenging their health.\u003C\/p\u003E\u003Cp\u003EGlobally, bird numbers are dropping. According to figures published by conservation organisation \u003Ca href=\u0022https:\/\/www.birdlife.org\/research-and-innovation\/sites\/default\/files\/hm\/attachments\/BL_ReportENG_V11_spreads.pdf\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003EBirdLife International\u003C\/a\u003E last year, 40% of bird\u0026nbsp;species have declining populations while 7% are increasing in number. BirdLife cites urbanisation as a force destructive to many bird species, but a few do well in cities, such as the adaptable \u003Ca href=\u0022https:\/\/www.iucnredlist.org\/species\/22735990\/87431138\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Egreat tit\u003C\/a\u003E, whose population is on the rise.\u003C\/p\u003E\u003Cp\u003ECity wildlife have a different experience of predators, food availability and diseases than those in the country. This may be helpful to them \u2013 for example, humans leave food out for birds in their gardens. But they also have to cope with a fragmented habitat and with noise, air and light pollution. Scientists want to understand these forces in order to get a better grasp of the dramatic drop in some bird populations. \u0026nbsp;\u003C\/p\u003E\u003Cp\u003EA research group in Sweden has been studying great tits living in 500 nestboxes in the city of Malm\u00f6, and a similar number in the forest. Great tits were chosen partly because they are well-studied and also because their use of nestboxes makes it easy for researchers to locate and examine them. The researchers check the boxes weekly during spring, weighing chicks with tiny balances, measuring them with adapted rulers, and tapping them for blood, according to Dr Hannah Watson, an ecologist at Lund University in Sweden.\u003C\/p\u003E\u003Cp\u003EAn early study revealed that the urban birds had higher levels of antioxidants circulating in their blood than rural birds \u2013 a defence mechanism against attack from free radicals - toxic versions of oxygen atoms.\u003C\/p\u003E\u003Cp\u003E\u2018Exposure to air pollution would generate more free radicals (in the body) which can then increase what\u2019s called oxidative stress \u2013 a kind of cellular level stress,\u2019 said Dr Watson. \u2018The free radicals cause damage to DNA, lipids, proteins \u2013 all the macromolecules in the cell.\u2019\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ESwitched on\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003ETo explore the consequences in more detail, she compared RNA (a counterpart to DNA) samples between the two populations, in a project called \u003Ca href=\u0022https:\/\/cordis.europa.eu\/project\/rcn\/195821\/factsheet\/en\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003EURBAN EPIGENETICS\u003C\/a\u003E.\u003C\/p\u003E\u003Cp\u003EWhile genes code for the structure and maintenance of a living thing, they only function if they are switched on \u2013 or expressed. This happens via a bit of chemistry, methylation, which can be triggered by environmental factors.\u003C\/p\u003E\u003Cp\u003EDr Watson found that genes responsible for the city birds\u2019 immune responses had been upregulated, implying that they were fighting off more infections than rural birds. Similarly, other genes, such as those for neutralising poisons, for inflammation and for antioxidant production to combat free radicals, were also switched on.\u003C\/p\u003E\u003Cp\u003E\u003Cblockquote class=\u0022tw-text-center tw-text-blue tw-font-bold tw-text-2xl lg:tw-w-1\/2 tw-border-2 tw-border-blue tw-p-12 tw-my-8 lg:tw-m-12 lg:tw--ml-16 tw-float-left\u0022\u003E\n \u003Cspan class=\u0022tw-text-5xl tw-rotate-180\u0022\u003E\u201c\u003C\/span\u003E\n \u003Cp class=\u0022tw-font-serif tw-italic\u0022\u003E\u2018It\u2019s only the birds of really good quality that are able to actually survive the nestling period in the city.\u2019\u003C\/p\u003E\n \u003Cfooter\u003E\n \u003Ccite class=\u0022tw-not-italic tw-font-normal tw-text-sm tw-text-black\u0022\u003EDr Hannah Watson, Lund University, Sweden\u003C\/cite\u003E\n \u003C\/footer\u003E\n\u003C\/blockquote\u003E\n\u003C\/p\u003E\u003Cp\u003E\u2018We showed big differences in terms of the genes that are expressed and the levels they are expressed at,\u2019 she said. \u2018We interpret this as being consistent with our prediction that birds living in the city are exposed to more of these environmental stressors.\u2019\u003C\/p\u003E\u003Cp\u003EBut this doesn\u2019t necessarily mean that urban birds are suffering, says Dr Watson. \u2018It could just indicate that they\u2019re able to respond and cope.\u2019\u003C\/p\u003E\u003Cp\u003ETo understand whether the birds were taking urban stress in their stride, Dr Watson joined a study led by one of her colleagues in which they measured the caps \u2013 telomeres \u2013 at the ends of the birds\u2019 chromosomes.\u003C\/p\u003E\u003Cp\u003EOver the last decade, scientists have shown that telomeres gradually shorten each time a cell divides, and also in response to other stressors, eventually reaching a stage of senescence, or deterioration, which corresponds to an organism\u2019s old age and death. In fact, the length of a creature\u2019s telomeres, it turns out, seems to foretell its lifespan. The team conjectured that, if the urban stresses were actually affecting the great tits\u2019 ability to survive, this would be revealed in the lengths of their telomeres.\u003C\/p\u003E\u003Cp\u003EThey found that city chicks that were ready to fledge had on average shorter telomeres than those of fledgling forest chicks.\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EWeeded out\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EThose with the shortest telomeres were less able to cope with urban stresses and died before reaching adulthood. Paradoxically, that meant that adult great tits in the city were likely to be stronger than the average forest adult because the weaker ones had been weeded out.\u003C\/p\u003E\u003Cp\u003E\u2018It\u2019s only the birds of really good quality that are able to actually survive the nestling period in the city,\u2019 said Dr Watson.\u2019 In fact, the researchers think that while multiple stressors in the city are wiping out younger, weaker birds, they may not be of much consequence during adult life for those tough enough to make it that far.\u003C\/p\u003E\u003Cp\u003E\u003Cfigure role=\u0022group\u0022 class=\u0022@alignleft@\u0022\u003E\n\u003Cimg alt=\u0022Great tits living in urban areas fight off more infections than their rural cousins. Image Credit - CC BY-SA 4.0\u0022 height=\u00221491\u0022 src=\u0022\/research-and-innovation\/sites\/default\/files\/hm\/IMCEUpload\/great-tit-walnut.jpg\u0022 title=\u0022Great tits living in urban areas fight off more infections than their rural cousins. Image Credit - CC BY-SA 4.0\u0022 width=\u00222476\u0022\u003E\n\u003Cfigcaption class=\u0022tw-italic tw-mb-4\u0022\u003EGreat tits living in urban areas fight off more infections than their rural cousins. Image Credit - CC BY-SA 4.0\u003C\/figcaption\u003E\n\u003C\/figure\u003E\n\u003C\/p\u003E\u003Cp\u003EUrban living may also mean that the social structures that served a species well in the natural habitat have become no longer necessary or even harmful.\u003C\/p\u003E\u003Cp\u003EHouse sparrows in the wild, for example, compete with each other for food according to a dominance hierarchy that is determined largely by size. But in cities, there are two key differences \u2013 food is more abundant and house sparrows are smaller, possibly because they don\u2019t need to store body fat since winters are milder. Either factor could undermine the way they normally compete for food.\u003C\/p\u003E\u003Cp\u003ELikewise, house sparrows are known for the way they cooperate to mob potential predators. But when the danger shifts from a bird of prey to a cat or dog, this behaviour could become redundant.\u003C\/p\u003E\u003Cp\u003EWith their numbers in decline, but still strong at as many as 1.3 billion globally, their \u003Ca href=\u0022https:\/\/www.audubon.org\/field-guide\/bird\/house-sparrow\u0022\u003Etoughness\u003C\/a\u003E, aggression and ability to survive around humans suggests they seem to do well in urban areas.\u003C\/p\u003E\u003Cp\u003EDr Lyanne Brouwer, an animal ecologist at Radboud University Nijmegen in the Netherlands, is studying house sparrows in a variety of urban habitats as they engage in their cooperative and competitive\u0026nbsp;behaviours in a project called\u0026nbsp;\u003Ca href=\u0022https:\/\/cordis.europa.eu\/project\/rcn\/215398_en.html\u0022\u003EUrbanBird\u003C\/a\u003E, which runs until 2020. She is using observations gathered by ordinary people, as well as her own field work to understand the causes and longterm effects of any\u0026nbsp;behavioural\u0026nbsp;change in the way house sparrows interact with each other. Ultimately this could help\u0026nbsp;predict how\u0026nbsp;urbanisation\u0026nbsp;could affect other species and biodiversity.\u003C\/p\u003E\u003Cp\u003E\u2018It\u2019s really interesting to see that all the factors that could affect social behaviour, like for example food availability or the predators that are around, are all very different in cities - so how would that affect these social behaviours? It turns out there is basically nothing known about how such behaviours change in cities,\u2019 she said.\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThe research in this article was funded by the EU. 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