Morning flight behavior of nocturnally migrating birds along the western basin of Lake Erie

Abstract

Many species of birds that normally migrate during the night have been observed engaging in so‐called morning flights during the early morning. The results of previous studies have supported the hypothesis that one function of morning flights is to compensate for wind drift that birds experienced during the night. Our objective was to further explore this hypothesis in a unique geographic context. We determined the orientation of morning flights along the southern shore of Lake Erie's western basin during the spring migrations of 2016 and 2017. This orientation was then compared to the observed orientation of nocturnal migration. Additionally, the orientation of the birds engaged in morning flights following nights with drifting winds was compared to that of birds following nights with non‐drifting winds. The morning flights of most birds at our observation site were oriented to the west‐northwest, following the southern coast of Lake Erie. Given that nocturnal migration was oriented generally east of north, the orientation of morning flight necessarily reflected compensation for accumulated, seasonal wind drift resulting from prevailingly westerly winds. However, the orientation of morning flights was similar following nights with drifting and non‐drifting winds, suggesting that birds on any given morning were not necessarily re‐orienting as an immediate response to drift that occurred the previous night. Given the topographical characteristics of our observation area, the west‐northwest movement of birds in our study is likely best explained as a more complex interaction that could include some combination of compensation for wind drift, a search for suitable stopover habitat, flying in a direction that minimizes any loss in progressing northward toward the migratory goal, and avoidance of a lake crossing.

Flight directions of songbirds are unaffected by the topography of Lake Erie’s southern coastline during fall migration

“…Rather, fall migrants on the southern coast of Lake Erie appear more likely to seek out stopover habitat away from the lakefront as well as perhaps during their morning flights (Gauthreaux 1978), which are overwhelmingly oriented along the coast (Tuck et al. 2018).…”

Geographic barriers and season shape the nightly timing of avian migration

“…Only a few measurements exist from radio telemetry and activity loggers, and those studies suggest a high variation in flight time up to the full length of the night but generally ceasing at sunrise (Bowlin et al, 2005; Liechti et al, 2018; Sjöberg et al, 2021). Following nocturnal flights sometimes short morning flights are observed (Tuck et al, 2018; Van Doren et al, 2016).…”