Migratory birds undertake\nepic journeys connecting oceans and continents, awing people across the globe. Sadly,\nas spectacular as these seasonal movements are, many populations of migratory\nbirds are in decline due to human threats, but tackling\ntheir conservation is challenging, as for most species many mysteries of their\nmigrations remain unknown. <\/p>\n\n\n\n
Scientists believe birds migrate to\nincrease their energetic efficiency<\/em>:\nput simply, birds migrate in pursuit of better access to food, warmer\nclimates and less competition with birds of their own and other species. On the\nother side of the coin, though, by\nspending long periods in disparate areas during the year (like barn swallows\nbreeding in Lithuania and \u2018wintering\u2019 in Southern Africa) these amazing birds\nbecome exposed to very different threats that can affect their survival. Understanding\nthese connections between the different stages of the annual cycles, or the migratory\nconnectivity, is thus key for informing successful conservation action for\nmigratory species.<\/p>\n\n\n\n What is migratory connectivity<\/strong> and why is it important for conservation?<\/strong><\/p>\n\n\n\n Think of\nyour favorite migratory bird that you can observe in your backyard. Now think\nof all individuals of the same species that you can find across your town, or\neven across your country. If you live in the Southern hemisphere, have you\nwondered if they all came from the same breeding areas in the North?\nConversely, if you live in the Northern Hemisphere, have you wondered if, after\nraising their offspring, they all migrate to the same places in the South for\nspending the nonbreeding season? <\/p>\n\n\n\n Migratory connectivity<\/em> reflects exactly\nthat! The degree to which birds from one nonbreeding area migrate to the same breeding\ngrounds and vice versa. Now if you think of all the populations of that species,\nmigratory connectivity represents the degree to which different breeding populations\nmix in the (non)breeding areas.<\/p>\n\n\n\n Migratory\nconnectivity has important implications for the conservation of migratory birds,\nbecause threats may affect populations differently depending on their migratory\nroutes, distances covered and timings used. For example, a recent study has\nshown that populations of Ortolan Bunting migrating across France are in\ngreater decline than populations migrating eastwards, due to illegal hunting in\nthat country for gastronomy. Understanding connectivity is key for planning and\nmanage important sites for migratory birds; in the case of the Ortolan Bunting,\nstopping illegal hunting in France would help conserving the species\u2019\npopulations breeding across western and northern Europe!<\/p>\n\n\n\n A mathematical model to predict connectivity<\/strong><\/p>\n\n\n\n Insights\ninto the migratory connectivity of various species can be obtained through\nringing birds, using advanced laboratory techniques based on geochemical\nmarkers (isotopes) and genetics, and by fitting biologgers that allow recording\nindividual movements throughout the year. In the last decade or so, a\nremarkable number of studies were published contributing immensely to increasing\nour knowledge on the connectivity of several species of migratory birds.<\/p>\n\n\n\n Capitalizing\non this wealth of data, Marius Somveille and colleagues developed a\nmathematical model to predict where different populations of migratory birds in\nthe Americas go during the nonbreeding season. The authors predicted the flow\nof individuals from a breeding area to a nonbreeding area by assuming birds\nmigrate between these areas to maximize their energetic efficiency (birds are ideal<\/em>, that is, individuals have a\ncomplete knowledge of the resources available in a given area and compete for\nthem). According to the authors\u2019 idea, after breeding, birds migrate to areas\nwith a higher abundance of food, and disperse across the landscapes in order to\nreduce competition with other individuals.<\/p>\n\n\n\n Although\nbased in simple ecological assumptions, to develop the model the authors had to\nuse complex mathematical formulas from graph theory and economics to\ntheoretical ecology. To make the model predictions realistic, they used maps of\nspecies distributions and abundances generated with data from the eBird<\/a>, a citizen-science platform where\neveryone can contribute with bird observations. By integrating all this\ninformation, they managed to calculate how much energy was available for each\nspecies in their breeding and nonbreeding areas, how much energy birds had to\nspend to move between these places and how much energy they need to survive\neach step!<\/p>\n\n\n\n Then, the authors tested their model\npredictions with data from 25 bird species for which migratory connectivity\npatterns have been revealed with field studies, and found that the model\ncaptures very well the known migratory connectivity patterns of these species \u2212\nGreat job!<\/p>\n\n\n\n Does the model explain everything? No, but certainly it is useful for\nconservation!<\/strong><\/p>\n\n\n\n “The most that can be expected from any model is that it can supply a\nuseful approximation to reality: All models are wrong; some models are useful<\/em>”\n(Box, Hunter & Hunter 2005: Statistics for Experimenters)<\/p>\n\n\n\n The model by Somveille and\ncolleagues is necessarily a simplistic representation of the complex phenomena\nof bird migration and does not take into account many important aspects\ninherent to the migratory process. For example, the model only explores the\nlinks between breeding and \u2018final\u2019 nonbreeding areas, not capturing the immense\nand intricate network of sites in between, which are key for migratory animals\nto rest and refuel. <\/p>\n\n\n\n Nevertheless, this model is a very\nnice step towards our comprehension of migration and the connectivity of birds,\nproviding a novel tool with important applications for their conservation. For\nexample, the model can shed light on the migration patterns of populations for\nwhich movement (empirical) data are not yet available.\n\nThe\npaper by Marius Somveille and\ncolleagues that motivated this blog was recently published in Ecology Letters\nand can be found here: Somveille, M., Bay, R.A., Smith, T.B., Marra, P.P. & Ruegg, K.C. (2021): A general\ntheory of avian migratory connectivity<\/strong><\/a>. <\/strong>Ecology Letters<\/em><\/p>\n","protected":false},"excerpt":{"rendered":" Migratory birds undertake epic journeys connecting oceans and continents, awing people across the globe. Sadly, as spectacular as these seasonal movements are, many populations of migratory birds are in decline due to human threats, but tackling their conservation is challenging, as for most species many mysteries of their migrations remain unknown. Scientists believe birds migrate […]<\/p>\n","protected":false},"author":15,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"footnotes":""},"categories":[6,4],"tags":[],"class_list":["post-818","post","type-post","status-publish","format-standard","hentry","category-blog","category-news"],"rttpg_featured_image_url":null,"rttpg_author":{"display_name":"Joao Lopes Guilherme","author_link":"https:\/\/www.science4wildlife.com\/index.php\/author\/joao\/"},"rttpg_comment":0,"rttpg_category":"Blog<\/a> News<\/a>","rttpg_excerpt":"Migratory birds undertake epic journeys connecting oceans and continents, awing people across the globe. Sadly, as spectacular as these seasonal movements are, many populations of migratory birds are in decline due to human threats, but tackling their conservation is challenging, as for most species many mysteries of their migrations remain unknown. Scientists believe birds migrate…","_links":{"self":[{"href":"https:\/\/www.science4wildlife.com\/index.php\/wp-json\/wp\/v2\/posts\/818","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.science4wildlife.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.science4wildlife.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.science4wildlife.com\/index.php\/wp-json\/wp\/v2\/users\/15"}],"replies":[{"embeddable":true,"href":"https:\/\/www.science4wildlife.com\/index.php\/wp-json\/wp\/v2\/comments?post=818"}],"version-history":[{"count":3,"href":"https:\/\/www.science4wildlife.com\/index.php\/wp-json\/wp\/v2\/posts\/818\/revisions"}],"predecessor-version":[{"id":821,"href":"https:\/\/www.science4wildlife.com\/index.php\/wp-json\/wp\/v2\/posts\/818\/revisions\/821"}],"wp:attachment":[{"href":"https:\/\/www.science4wildlife.com\/index.php\/wp-json\/wp\/v2\/media?parent=818"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.science4wildlife.com\/index.php\/wp-json\/wp\/v2\/categories?post=818"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.science4wildlife.com\/index.php\/wp-json\/wp\/v2\/tags?post=818"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}