Stormy Seas for Some North American Songbirds: Are Declines Related to Severe Storms During Migration?

摘要: "Many large flocks of birds flew over, coming from the north and flying to SW. They were more varied in kind than any we had seen before they land .... I know that most islands discovered by Portuguese have been found because birds."-Christopher Columbus, east Bermuda, 7 October 1492 Several hypotheses presented explain population declines long-distance migrant songbirds eastern central North America (Rappole 1995). Although probably result interplay several factors (Blake et al. 1992), habitat destruction on wintering grounds Neotropics breeding is believed be a major cause (e.g. Terborgh 1989, Askins al.1990, Rappole 1995, Sauer 1996). However, evidence for causal link between large-scale not strong (Petit 1992). Many species breed migrate over western Atlantic Ocean or Gulf Mexico winter Caribbean, Central America, South (Williams 1977, Williams 1985, Moore Nisbet During these transoceanic flights, migrants tend avoid periods unfavorable weather, movements often coincide with favorable wind conditions (Richardson 1976, Stoddard 1983, Alerstam 1990). In contrast, through (Moore 1995), where can make landfall if deteriorate. succumb during weather while attempting cross 1990:337-338) (Lowery 1946). Consequently, abundance might affected strongly frequency events migration would latter group does ocean. The "storm hypothesis" posits abundances Neotropical are negatively related severity storms autumn passage Predictions storm hypothesis that: (1) long flights ocean should exhibit greater de-