Destruction of Nests by the Short-Billed Marsh Wren

Abstract

-Short-billed Marsh Wrens (Cistothorus platensis) examined experimentally offered nests of Red-winged Blackbirds, Yellow-headed Blackbirds, Long-billed Marsh Wrens, and conspecifics. They also pecked eggs of Zebra Finches, Long-billed Marsh Wrens, Red-winged Blackbirds, and Cinnamon Teal, and once a male wren also pecked nestling Red-winged Blackbirds. Marsh wrens broke all small eggs, but the largest (teal) eggs survived the wrens' attacks. Results suggested that Short-billed Marsh Wrens attack eggs regardless of their size and color, but can destroy only small eggs. These wrens probably have a significant impact on nesting success of other small sympatric birds, including conspecifics. By destroying nests, Shortbilled Marsh Wrens probably exclude other birds from the vicinity of their activity centers and thereby reduce interference from them. Among all temperate zone passerines, marsh-nesting birds suffer the highest nest mortality rates, mainly through predation (Ricklefs 1969). Predators include raccoons, mink, hawks, owls, jays, crows, and water snakes (Allen 1914, Bent 1958, Robertson 1972). Other studies have shown that one of the most important predators destroying nests of marsh-dwelling passerines in North America is the Long-billed Marsh Wren (Cistothorus palustris; Allen 1914, Orians and Willson 1964, Burt 1970, Verner 1975, Picman 1977a, 1980). Destruction of nests by small passerines appears rare, but has been observed in several species of wrens, including the House Wren (Troglodytes aedon; Kendeigh 1941); Long-billed Marsh Wren (Allen 1914); Cactus Wren (Campylorhynchus brunneicapillus; Anderson and Anderson 1973); and Bewick's Wren (Thryomanes bewickii; Picman, pers. observ.). This indicates that nest-destroying behavior might be a common feature of the wren family. In this study, we investigated nest-destroying behavior of another wren, the Short-billed Marsh Wren (Cistothorus platensis) which breeds on wet sedge and grass meadows adjacent to marshes of eastern and central North America (Bent 1948). This species frequently is sympatric with Redwinged Blackbirds (Agelaius phoeniceus), Long-billed Marsh Wrens, Common Yellowthroats (Geothlypis trichas), Savannah Sparrows (Passerculus sandwichensis), Henslow's Sparrows (Ammodramus henslowii), Swamp Sparrows (Melospiza georgiana), and Song Sparrows (Melospiza melodia; Walkinshaw 1935, Bent 1948, Kroodsma and Verner 1978, this study). Nest destruction by this wren, therefore, might present an important factor reducing reproductive success of these and possibly other marsh-nesting birds. The questions we asked during this study were: (1) Do Short-billed Marsh Wrens normally destroy nests? (2) What kinds of nests and eggs will these wrens attack? (3) Do they attack nestlings? (4) Do affected species interact behaviorally with Shortbilled Marsh Wrens? (5) Why do these wrens attack nests with eggs or young?