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Soaring and gliding flight of migrating broad-winged hawks : behavior in the nearctic and neotropics compared

Careau, Vincent, Therrien, Jean-Francois, Porras, Pablo, Thomas, Don and Bildstein, Keith 2006, Soaring and gliding flight of migrating broad-winged hawks : behavior in the nearctic and neotropics compared, Wilson journal of ornithology, vol. 118, no. 4, pp. 471-477, doi: 10.1676/05-140.1.

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Title Soaring and gliding flight of migrating broad-winged hawks : behavior in the nearctic and neotropics compared
Author(s) Careau, Vincent
Therrien, Jean-Francois
Porras, Pablo
Thomas, Don
Bildstein, Keith
Journal name Wilson journal of ornithology
Volume number 118
Issue number 4
Start page 471
End page 477
Total pages 7
Publisher Wilson Ornithological Society
Place of publication Albion, Mich.
Publication date 2006
ISSN 1559-4491
1938-5447
Summary We compared migrating behavior of Broad-winged Hawks (Buteo platypterus) at two sites along their migration corridor: Hawk Mountain Sanctuary in eastern Pennsylvania and the Kéköldi Indigenous Reserve in Limón, Costa Rica. We counted the number of times focal birds intermittently flapped their wings and recorded the general flight type (straight-line soaring and gliding on flexed wings versus circle-soaring on fully extended wings). We used a logistic model to evaluate which conditions were good for soaring by calculating the probability of occurrence or absence of wing flaps. Considering that even intermittent flapping is energetically more expensive than pure soaring and gliding flight, we restricted a second analysis to birds that flapped during observations, and used the number of flaps to evaluate factors influencing the cost of migration. Both the occurrence and extent of flapping were greater in Pennsylvania than in Costa Rica, and during periods of straight-line soaring and gliding flight compared with circle-soaring. At both sites, flapping was more likely during rainy weather and early and late in the day compared with the middle of the day. Birds in Costa Rica flew in larger flocks than those in Pennsylvania, and birds flying in large flocks flapped less than those flying alone or in smaller flocks. In Pennsylvania, but not in Costa Rica, the number of flaps was higher when skies were overcast than when skies were clear or partly cloudy. In Costa Rica, but not in Pennsylvania, flapping decreased as temperature increased. Our results indicate that birds migrating in large flocks do so more efficiently than those flying alone and in smaller flocks, and that overall, soaring conditions are better in Costa Rica than in Pennsylvania. We discuss how differences in instantaneous migration costs at the two sites may shift the species' migration strategy from one of time minimization in Pennsylvania to one of energy minimization in Costa Rica.
Language eng
DOI 10.1676/05-140.1
Field of Research 059999 Environmental Sciences not elsewhere classified
Socio Economic Objective 970105 Expanding Knowledge in the Environmental Sciences
HERDC Research category C1.1 Refereed article in a scholarly journal
Copyright notice ©2006, Wilson Ornithological Society
Free to Read? Yes
Persistent URL http://hdl.handle.net/10536/DRO/DU:30056118

Document type: Journal Article
Collections: School of Life and Environmental Sciences
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Every reasonable effort has been made to ensure that permission has been obtained for items included in DRO. If you believe that your rights have been infringed by this repository, please contact drosupport@deakin.edu.au.