Edge effects and ecological traps: Effects on shrubland birds in Missouri

The effect of habitat edge on avian nesting Success has been the focus of c onsiderable debate. We studied relationships between habitat edges, locatio ns of nests, and predation. We tested the ecological trap hypothesis for 5 shrubland bird species in the Missouri Ozarks. We compared habitat selectio n and daily nest predation rates among 3 distance-to-edge categories. Edge effects were species specific. Indigo bunting (Passerina cyanea) and northe rn cardinal (Cardinalis cardinalis) preferred nest sites that were close (l ess than or equal to 20 m) to habitat edges. Yellow-breasted chat (Icteria virens) and prairie warbler (Dendroica discolor) preferred nest sites >20 i n front the edge. Field sparrow (Spizella pusilla) used habitat in proporti on to availability. Daily nest predation varied by as much as 200-300% amon g distance-to-edge categories but did not decrease monotonically with dista nce front edge. The nest predation models without distance-to-edge categori es were ranked the best models based on Akaike's Information Criterion: how ever, Akaike weights indicated some support for alternative models with dis tance-to-edge categories. Edges did not act as ecological traps for shrubla nd birds in this study because habitat preference was not positively correl ated with nest predation across the 3 distance-to-edge categories. Research ers and land managers should not assume that shrubland birds respond to edg es in the same way that forest species respond to edges. Furthermore, speci es with similar nesting ecology do not necessarily have similar nest-site p references or nest predation rates in relation to distance to habitat edges .