Wing size but not wing shape is related to migratory behavior in a soaring bird

Abstract

Both wing size and wing shape affect the flight abilities of birds. Intra and inter‐specific studies have revealed a pattern where high aspect ratio and low wing loading favour migratory behaviour. This, however, have not been studied in soaring migrants. We assessed the relationship between the wing size and shape and the characteristics of the migratory habits of the turkey vulture Cathartes aura, an obligate soaring migrant. We compared wing size and shape with migration strategy among three fully migratory, one partially migratory and one non‐migratory (resident) population distributed across the American continent. We calculated the aspect ratio and wing loading using wing tracings to characterize the wing morphology. We used satellite‐tracking data from the migratory populations to calculate distance, duration, speed and altitude during migration. Wing loading, but not aspect ratio, differed among the populations, segregating the resident population from the completely migratory ones. Unlike what has been reported in species using flapping flight during migration, the migratory flight parameters of turkey vultures were not related to the aspect ratio. By contrast, wing loading was related to most flight parameters. Birds with lower wing loading flew farther, faster, and higher during their longer journeys. Our results suggest that wing morphology in this soaring species enables lower‐cost flight, through low wing‐loading, and that differences in the relative sizes of wings may increase extra savings during migration. The possibility that wing shape is influenced by foraging as well as migratory flight is discussed. We conclude that flight efficiency may be improved through different morphological adaptations in birds with different flight mechanisms.

Temperature and aridity determine body size conformity to Bergmann’s rule independent of latitudinal differences in a tropical environment

“…2 ). Therefore, we eliminate the possibility of misinterpreting an interrupted foraging response due to breeding (Nwaogu et al 2017 ), starvation risk (Macleod and Gosler 2006 ) or migration (Hahn et al 2015 ; Grilli et al 2017 ) as conforming to Bergmann’s rule. Unfortunately, both wing length and body mass have been used on their own to test Bergmann’s rule (Watt et al 2010 ) and this may lead to misleading interpretations.…”

A three-decade review of telemetry studies on vultures and condors

“…They found that the heart rate of the studied bird only slightly increased with distance traveled, demonstrating the highly efficient flight performance of this long-distance migrating species. Similarly, a recent study also found that migrating Turkey Vultures showed differences in a set of movement-related metrics (i.e., distance, duration, speed and altitude of migration) as a result of differences in wing loading, which suggests that wing morphology could influence the selection of migration routes [ 71 ]. Among the internal mechanistic components that shape vulture migration, navigation capacity remains largely unexplored.…”

Understanding the relationship between climatic niches and dispersal through the lens of bat wing morphology

“…Wing morphology has increased importance for species relationships with the environment because they dictate the type of flight, the energetics of flight performance, the life‐history strategies and the ecological patterns such as habitat use and foraging strategies in several spatial scales (Norberg & Rayner, 1987; Marinello & Bernard, 2014; Grilli et al ., 2017; Sullivan, Meyers & Arzt, 2019). For bats, RWL and AR influence ecological dynamics, from local to broad geographical scales, exemplified by their impacts on habitat, resource use and biogeography (Norberg & Rayner, 1987; Marinello & Bernard, 2014; Luo et al ., 2019).…”