{"id":254,"date":"2018-12-02T09:11:43","date_gmt":"2018-12-02T08:11:43","guid":{"rendered":"https:\/\/blogs.futura-sciences.com\/lehning\/?p=254"},"modified":"2019-01-04T11:58:24","modified_gmt":"2019-01-04T10:58:24","slug":"la-taille-des-oeufs-de-coucous","status":"publish","type":"post","link":"https:\/\/blogs.futura-sciences.com\/lehning\/2018\/12\/02\/la-taille-des-oeufs-de-coucous\/","title":{"rendered":"La taille des \u0153ufs de coucous"},"content":{"rendered":"

Certaines esp\u00e8ces de coucous font couver leurs \u0153ufs par des oiseaux de tailles tr\u00e8s diff\u00e9rentes. Chacune a sa strat\u00e9gie de parasitage. Certains, dont le coucou gris, semblent adapter la taille de leurs \u0153ufs \u00e0 celle de ceux de leur h\u00f4te involontaire.<\/span><\/span><\/p>\n

Le coucou gris<\/h2>\n

Le coucou gris, qui a la taille d\u2019un pigeon, parasite des passereaux. \u00c0 premi\u00e8re vue, le sc\u00e9nario est simple. La femelle coucou pond un \u0153uf dans le nid de rousserolles, de roitelets, de fauvettes, ou d\u2019autres. Son \u0153uf est le premier \u00e0 \u00e9clore. Le petit coucou expulse alors la couv\u00e9e enti\u00e8re du nid. Les passereaux nourrissent ensuite l\u2019intrus jusqu\u2019\u00e0 ce qu\u2019il soit adulte.<\/span><\/span><\/p>\n

\"\"
Jeune coucou se faisant nourrir par une rousserolle.<\/figcaption><\/figure>\n

Strat\u00e9gies du coucou<\/h2>\n

Pour atteindre son but, le couple de coucous rep\u00e8re puis guette un nid de passereau, de l\u2019esp\u00e8ce qui les a \u00e9lev\u00e9s de pr\u00e9f\u00e9rence. Ce choix n\u2019est pas toujours possible, et une erreur peut \u00eatre fatale au jeune coucou. Par exemple, si la femelle pond dans un nid de granivores, son petit mourra de faim, car le coucou est insectivore.<\/span><\/span><\/p>\n

Quand la femelle passereau a pondu, celle du coucou profite de son absence, pour gober un \u0153uf et le remplacer rapidement par l\u2019un des siens. Son \u0153uf \u00e9clot avant ceux des passereaux car il a commenc\u00e9 \u00e0 incuber dans son corps. Sit\u00f4t n\u00e9, encore aveugle, le petit coucou expulse tous les \u0153ufs du nid afin d\u2019\u00eatre nourri seul par ses parents adoptifs.<\/span><\/span><\/p>\n

\"\"
Oisillon coucou jetant un \u0153uf hors du nid.<\/figcaption><\/figure>\n

Les math\u00e9matiques du coucou<\/h2>\n

Bien que le coucou soit cinq \u00e0 six fois plus grand que les passereaux qu\u2019il parasite, sa femelle pond des \u0153ufs de taille comparable aux leurs. Plus \u00e9trange, elle semble adapter la taille de ses \u0153ufs \u00e0 celle de ceux qui se trouvent dans le nid dans lequel elle pond. L\u2019un des premiers scientifiques \u00e0 avoir \u00e9tudi\u00e9 la question quantitativement, Oswald Latter en 1902, a r\u00e9colt\u00e9 29 \u0153ufs de coucous dans des nids de roitelets et de fauvettes et not\u00e9s les diam\u00e8tres.\u00a0En r\u00e9unissant ces donn\u00e9es dans deux histogrammes, nous obtenons deux courbes en cloche distinctes ce qui indique que nous avons affaire \u00e0 deux populations distinctes. Autrement dit, la femelle coucou adapte bien la taille de ses \u0153ufs \u00e0 ceux d\u00e9j\u00e0 pr\u00e9sents dans le nid dans lequel elle pond.<\/span><\/span><\/p>\n

\"\"<\/p>\n

Distributions des diam\u00e8tres des \u0153ufs pondus dans les nids de roitelets (en orange) et de fauvettes (en vert).Cette \u00e9tude a depuis \u00e9t\u00e9 confirm\u00e9e pour plusieurs esp\u00e8ces de coucous. La recherche est d\u2019autant plus active sur la question que, suivant les esp\u00e8ces, les coucous pratiquent le parasitisme de couv\u00e9e, ou non et, parmi les coucous parasites, certains sont \u00e9jecteurs (ils d\u00e9truisent les \u0153ufs de leur h\u00f4te d\u00e8s leur \u00e9closion) et d\u2019autres, non. Les seconds parasitent des esp\u00e8ces de taille comparable \u00e0 la leur alors que les autres choisissent des oiseaux plus petits.<\/span><\/span><\/p>\n

Le parasitisme de couv\u00e9e<\/h2>\n
\"\"
Les canards colverts pratiquent le parasitisme de couv\u00e9e, mais \u00e0 l\u2019int\u00e9rieur de leur esp\u00e8ce. \u00a9 Herv\u00e9 Lehning<\/figcaption><\/figure>\n

Le parasitisme de couv\u00e9e ne se limite pas \u00e0 certaines esp\u00e8ces de coucous. Cependant, le ph\u00e9nom\u00e8ne d\u2019adaptation de la taille de l\u2019\u0153uf \u00e0 celle de ceux de l\u2019h\u00f4te n\u2019a pas forc\u00e9ment lieu. Par exemple, certaines canes colverts pondent dans des nids d\u2019autres colverts. Les flamands roses font de m\u00eame ainsi que bien d\u2019autres esp\u00e8ces d\u2019oiseaux (on en a d\u00e9nombr\u00e9 236). Dans d\u2019autres cas, les oiseaux parasitent des esp\u00e8ces de taille similaire \u00e0 la leur. Seuls ceux qui parasitent des oiseaux plus petits connaissent ce ph\u00e9nom\u00e8ne d\u2019adaptation de la taille de leurs \u0153ufs.<\/span><\/span><\/p>\n\n\n\n
<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

 <\/p>\n

 <\/p>\n

\u00a0<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

Certaines esp\u00e8ces de coucous font couver leurs \u0153ufs par des oiseaux de tailles tr\u00e8s diff\u00e9rentes. Chacune a sa strat\u00e9gie de parasitage. Certains, dont le coucou gris, semblent adapter la taille de leurs \u0153ufs \u00e0 celle de ceux de leur h\u00f4te involontaire. Le coucou gris Le coucou gris, qui a la taille d\u2019un pigeon, parasite des … Continuer la lecture de La taille des \u0153ufs de coucous<\/span> →<\/span><\/a><\/p>\n","protected":false},"author":12,"featured_media":262,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_links_to":"","_links_to_target":""},"categories":[67,29,11,13],"tags":[126,128,127,129],"class_list":["post-254","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-ecologie","category-maths-2","category-nature","category-photographies","tag-coucous","tag-oiseaux","tag-parasite","tag-statistiques"],"yoast_head":"\nLa taille des \u0153ufs de coucous, par Herv\u00e9 Lehning<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/blogs.futura-sciences.com\/lehning\/2018\/12\/02\/la-taille-des-oeufs-de-coucous\/\" \/>\n<meta property=\"og:locale\" content=\"fr_FR\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"La taille des \u0153ufs de coucous, par Herv\u00e9 Lehning\" \/>\n<meta property=\"og:description\" content=\"Certaines esp\u00e8ces de coucous font couver leurs \u0153ufs par des oiseaux de tailles tr\u00e8s diff\u00e9rentes. Chacune a sa strat\u00e9gie de parasitage. Certains, dont le coucou gris, semblent adapter la taille de leurs \u0153ufs \u00e0 celle de ceux de leur h\u00f4te involontaire. 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