| Abstract: | Conventional 35 mm photography was used to conduct an aerial photographic census of canvasbacks (A. valisineria) throughout Chesapeake Bay (tidal Maryland and Virginia) and coastal North Carolina, Jan. 26-30, 1981. Flock size and sex ratio characteristics were determined from examination of color transparencies of 165 canvasback flocks totaling > 95,000 birds. A sex ratio of 2.91 males/female was determined from 68,769 birds, 80% of the birds in 150 flocks. Sex ratio for the Atlantic Flyway was projected as 2.90 males/female. The greatest number of canvasbacks and the widest range of flock size were recorded in Maryland waters; the fewest canvasbacks and the smallest average flock size in Virginia; and the fewest but on average the largest flocks of canvasbacks in North Carolina. Sex ratio varied latitudinally in the flyway with a tendency for males to occupy more northern and females more southern latitudes in winter. Sex ratio (males/female) was highest in Maryland (3.98), slightly lower in Virginia (3.71), and lowest in North Carolina (1.70). Locally, sex ratio varied with flock size. In Chesapeake Bay, small flocks (< 100 birds) had lower sex ratio (P < 0.05) than medium (100-1000) or large (> 1000) flocks. By providing large-sample sex ratio information, as well as exact counts of birds, low-level 35-mm aerial photography is the most efficient and accurate means of determining canvasback population status in eastern coastal habitats. |
| Genre: | Article |
| ProdID: | 5222030 |
| Citation Author: | Haramis, G.M.; Goldsberry, J.R.; McAuley, D.G.; Derleth, E.L. |
| Citation Contributing Office: | Patuxent Wildlife Research Center |
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| Citation End Page: | 454 |
| Citation Issue: | 2 |
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| Citation Language: | English |
| Citation Larger Work Title: | Journal of Wildlife Management |
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| Citation Number Of Pages: | 6 |
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| Citation Phsyical Description: | 449-454 |
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| Citation Search Results Text: | An aerial photographic census of Chesapeake Bay and North Carolina canvasbacks; 1985; Article; Journal; Journal of Wildlife Management; Haramis, G.M.; Goldsberry, J.R.; McAuley, D.G.; Derleth, E.L. |
| Citation Start Page: | 449 |
| Citation Volume: | 49 |
| Citation Year: | 1985 |
| Type: | citation/reference |
| Text: | An aerial photographic census of Chesapeake Bay and North Carolina canvasbacks; 1985; Article; Journal; Journal of Wildlife Management; Haramis, G.M.; Goldsberry, J.R.; McAuley, D.G.; Derleth, E.L. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| URL (DOCUMENT): | http://www.jstor.org/stable/3801550 |
| Date Other: | Wed, 16 Jun 2010 12:19 -0500 |
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