https://popups.lib.uliege.be/2984-0317/index.php?id=1867 Publications de Auteurs Serge Fontaine fr 0 https://popups.lib.uliege.be/2984-0317/index.php?id=1972 Black grouse defending a territory on a display arena use visual landmarks to recognize their mutual borders : grass tufts, heather shrubs, young trees, dead twigs, moss clumps... If the population of the arena is stable, each cock knows these landmarks very well, avoids trespassing them, and waits for his neighbours at the precise limits. If the population is changing and if young intruders try to settle, developing a strong pressure against central territories, it is much more easy for the owners to defend them when visual landmarks enhance the limits. Thus, cocks on our study areas soon use the numbered pools that we regularly space out on the arena to allow a precise recording of the territorial limits. The best way to prove the role of the natural landmarks in the recognition of the territorial limits would be to suppress them all. This is not utopic at all ; it suffices that a heavy snow fall covers the vegetation. Such a situation has been witnessed twice during our observations. As a result, the limits stay stable whenever the cocks are able to see the slightest usual landmarks, whereas they fluctuate on a large scale where both the vegetation and the numbered pools have been covered by a thick snow. Black Grouse cocks so really use landmarks to recognize their territorial limits. Lorsque la population d’une arène de parade de Tétras lyres (Tetrao tetrix) est stabilisée, le parcellaire territorial est relativement stable, chaque oiseau reconnaissant les limites de son domaine et les frontières de ses voisins. Les oiseaux utilisent à cet effet des repères visuels au sol : touffe de mousse, touradon de molinie, buisson de bruyère, creux du terrain, arbrisseau, clôture, fossé..., voire le balisage de piquets numérotés mis en place pour les observations pour faciliter le repérage et la cartographie de ces frontières. À deux reprises en Fagne wallonne en 1973, on a été témoin d'une situation ayant valeur d'une expérience naturelle sur la reconnaissance de ces limites territoriales, par rapport aux repères visuels. Par deux fois, en mars et en avril, une épaisse couche de neige a recouvert en une nuit tous les repères visuels. Correctement disposés les uns par rapport aux autres sur la surface neigeuse, les coqs ne reconnaissaient plus les limites exactes de leur territoire ; ils effectuaient des avancées et reculs au-delà et en deçà des limites habituelles ; leur déplacement témoigne à chaque instant de leur détermination en fonction de leur position respective. Dès que des repères visuels réapparaissent par suite de la fonte de la neige, les frontières se cristallisent, le parcellaire territorial se fige. Fri, 23 Feb 2024 14:54:50 +0100 Fri, 08 Mar 2024 13:33:32 +0100 https://popups.lib.uliege.be/2984-0317/index.php?id=1972 https://popups.lib.uliege.be/2984-0317/index.php?id=1970 During the period of highest density of Black Grouse in the Hautes-Fagnes Nature Reserve, Belgium, we have used stuffed hens in order to test the territorial and sexual tactics of cocks, an experiment already imagined by KRUIJT in the Netherlands. By the way, we have observed that the stuffed hen, keeping the crouching posture which means sollicitation for the copulation, has a supernormal value. Territorial males try to mount the model each time it passes through their territories. When we allow a male to persist in his attempt by stopping the hen in his territory, he proceeds mounting, taking the neck feathers of the hen in his beak, beating the wings and ensuring the cloacal contact for minutes. If this takes place a few meters near the terrltorial borders, other males soon trespass them, invade the territory and disrupt the copulation taking place there. A territory ensures sufficient quietness to succeed in copulating provided that the whole copulation takes only a few seconds. If it takes more time, the inhibition preventing the neighbours to trespass the borders comes to an end. These data have been authentified by filming (1980). Une poule naturalisée dans l'attitude accroupie de sollicitation à l'accouplement est traînée par un jeu de poulies d'un territoire à l'autre sur une arène de parade de Tétras lyres. Lorsqu'elle passe dans son territoire, chaque coq la courtise et tente de la monter. Comme 1e leurre tient la position accroupie, le coq prolonge anormalement la monte et la tentative de copulation. Dès lors, l'inhibition qui empêchait les voisins de franchir les frontières tombe et ceux-ci envahissent le territoire, bousculent le couple, interrompent la tentative. Cette expérience démontre que le territoire ne peut assurer la tranquillité nécessaire à la cour et à la copulation qu'à la condition que cette dernière ne dure que quelques secondes. Ces observations ont été authentifiées par des prises de vues cinématographiques, diffusées depuis 1980. Fri, 23 Feb 2024 14:48:28 +0100 Fri, 08 Mar 2024 13:25:16 +0100 https://popups.lib.uliege.be/2984-0317/index.php?id=1970 https://popups.lib.uliege.be/2984-0317/index.php?id=1866 Black Grouse is a most endangered species in central and western Europe, and the Hautes-Fagnes plateau in the Belgian Ardenne is probably its most western sanctuary on the continent. This Hautes-Fagnes plateau (summit of Belgium), a mixture of peat bogs and large forests, turned into moorland through traditional agricultural practices. Moorland reached its largest extent (17,500 ha) two centuries ago, then declined progressively down to 5,002 ha in the early 1960s, as new economic needs caused them to be drained and planted with spruce tree cultures. About 4,000 ha were saved in 1957 and 1964 as parts of the Hautes-Fagnes Nature Reserve, but the population of Black Grouse, a flag species for all plants and animals sharing the same habitats, had already suffered a sensible decline at that time. ln order to contribute to its conservation, we organized inventories and descriptions of thirty arenas where cocks gather in spring for Iekking (the very places to watch and count them), and these provided most valuable knowledge of the fluctuations of their numbers over the Iast thirty years and insight into the nature of risk factors. Thanks to important recruitments in the late 1960s, the population grew up to 198 males in 1971, then it collapsed down to 42 cocks in 1976. During the next 20 years, it fluctuated between about 80 (e.g. 1977, 1987), and less than 40 (e.g. 1982, 1983, 1995). The latest surveys in 1996 and 1997 revealed less than 30 cocks. The present situation is thus more critical than in the mid l970s, and even made worse by the spontaneous evolution of some parts of the Nature Reserve from attractive moorlands to less attractive woodlands. Considering that this evolution partly originates from weather dependent variations of recruitment (see Loneux et al.), hard work and strict policies are urgently needed to restore Black Grouse’s habitat (see Keulen et al.) and to enhance their populations, bearing in mind that a stock of 50 cocks is the Iower limit to face hazards of any kind during low density periods. Such a Black Grouse centered management policy will also benefit to all plant and animal species inhabiting the same open landscape. Tue, 20 Feb 2024 09:39:58 +0100 Tue, 12 Mar 2024 16:08:17 +0100 https://popups.lib.uliege.be/2984-0317/index.php?id=1866