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Comment un pivert fait un trou dans un arbre

Les oiseaux excavateurs, tels que la plupart des pics, s'attaquent à des arbres morts, plus faciles à creuser. Le trou est terminé en quelques semaines et la petite famille l'utilise durant une seule année. Le pic à face blanche (Picoides borealis), par contre, adopte une autre stratégie. Dans les forêts de pins des marais du sud-est des États-Unis, il creuse des arbres vivants. Le volatile consacre ainsi beaucoup d’énergie à cette tâche, qui peut durer de longues années ! Mais l'excavation du nid dans un arbre peut être facilitée par la présence, sur la zone à creuser, de champignons parasites. De fait, le tronc de l'arbre pourrit ; le bois devient plus tendre.


Last September I walked by the dining room window and saw a Pileated Woodpecker in a dead snag, about 75’ from the house. The tree was diseased and in danger of hitting the house, so a couple of years ago we had it topped, but left it standing – just for the woodpeckers. I cracked the window and slipped the scope out the window, and videoed him creating what appeared to be a new cavity, but he ended up making just a shallow depression.

Six months passed, and I saw him only occasionally. In March I looked out and he was back working very seriously on his well-aged starter cavity. He worked for a couple of days, excavating an enormous amount of wood. During the time he was still excavating the cavity, I looked out one morning to see him at the cavity, but his crest was up and he clearly didn’t want to go in. He hopped around the tree, came back, looked in, raised his crest, and left. Later in the day we say him working on the cavity again. We thought there might have been a rat snake in the cavity, so that afternoon, after he'd "knocked off" for the day, we went out and were about to wrap the base of the tree with some nylon mesh we use to protect nests from snakes, and saw that there was a fresh, broken egg on the ground at the base of the tree. Apparently a Wood Duck was in the cavity laying an egg, even before the Woodpecker had finished it. The most important tree in the woods is a snag, and the most important bird is the woodpecker.

I hope you enjoy this, it was a lot of fun to film and edit.

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