"They have been known to destroy bluebird and other cavity nester's eggs by piercing them (holes of 3 mm or less, or a large ragged hole in the middle), and then often removing them from the nest. They can remove an entire chickadee nest in a matter of hours. In one study in eastern MA, 20% of Black-capped Chickadee nests were destroyed by House Wrens. Althea Sherman reported that House Wrens destroyed eggs of 29 different birds. House Wrens may even displace the uncommon Bewick's Wren.
There have been occasional reports of House Wrens killing young nestlings (4-5 days old) and throwing them out of the nest (Ann Wick, Linda Moore has a nestcam video showing three 1-2 day old bluebirds taken out of nest at about 8 p.m. and then again the next evening; also Linda S. reported 2 day old Carolina Wrens tossed out of box). Kendeigh (1941) reported death of an adult bird. House Wrens have also been observed filling a red-naped sapsucker nest with sticks while the sapsucker chicks were still in the nesting cavity."
-----------------------------------------From: "Pat Lueders" <[log in to unmask]>
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