Movements of Juvenile Blackpoll Warblers Prior to Autumn Migration in Newfoundland

Abstract

Mitchell et al. (2010) reported that juvenile Blackpoll Warblers (Dendroica striata) raised in northwestern Newfoundland moved generally toward the southeast during the post-fledging period. They concluded (p. 651) that this finding failed to support their prediction from the migratory-commencement hypothesis. Their basis for this prediction (p. 645) was as follows: “We predicted that if meso movements represent initial migratory displacements, these moves should be oriented to the southwest at each study site, parallel to the known axis of migration (Richardson 1972).” The article by Richardson (1972) summarized his radar studies of migration over Nova Scotia and New Brunswick, covering an area that extended east of Cape Breton Island (to 58° W), almost as far east as the longitude of the study area of Mitchell et al. (49o 47′ N, 57o 16′ W) in Newfoundland. Richardson did not report a single “axis of migration.” His summary statement was the following: “In addition to the dense SW movements and the less dense reverse flights, movements to the SE and [word omitted] were also very common. Both passerines and shorebirds were commonly involved.” The remainder of the article indicated that the word omitted from this passage was either S or SSE. Richardson did not identify the passerines involved in the SE movements in his 1972 article, but, from a variety of other lines of evidence, he identified them as primarily Blackpoll Warblers in several subsequent papers in major ornithological journals (Richardson 1976, 1978, 1980),. The transoceanic migration of the Blackpoll Warbler, in which it departs SE or SSE from southeastern Canada and the northeastern USA, crosses the western North Atlantic Ocean and makes landfalls in the West Indies and South America, has been abundantly documented in