Parasitic Jaeger at Lake McConaughyNebraska Bird Review
Date of this Version12-1-1998
Dinsmore & Silcock in Nebraska Bird Review (December 1998) 66(4).
AbstractOn 5 October, 1997, we joined Joel G. Jorgensen and John Sullivan for a pelagic trip on Lake McConaughy. A similar trip in late September 1996 yielded a Sabine's Gull, but we were really hoping to see a jaeger. From 7:00 to 8:30 a.m. we gradually worked our way from the dam towards the western end of the lake. Besides moderate numbers of Franklin's and Ring-billed Gulls, there were few birds on the lake. At approximately 8:45 a.m. Dinsmore noticed that all of the gulls at the western end of the lake had suddenly taken flight. Less than a minute later, we simultaneously spotted a jaeger soaring directly overhead. The size, dark coloration, and prominent white flashes in the Wings identified the bird as a jaeger. The bird made a couple of attacks on Franklin Gulls and then flew east down the lake. We chased the jaeger for more than ten miles before losing it. We relocated the bird a short time later just above the dam. This time, the bird attacked a couple of Ring-billed Gulls before flying west up the lake. We again took chase, but lost the bird before reaching Lemoyne. The gull-like shape, generally brown coloration, and prominent white bases to the primaries identified the bird as a jaeger. The bird was smaller but longer-winged than a Ring-billed Gull and larger and slimmer than a Franklin's Gull. The overall coloration was dark brown, except for some warmer rufous tones on the underparts. We saw no visible barring on the underparts. The bill was straight and slender, but the color pattern was not noted. The upperwing was dark brown except for white at the base of at least the outermost four primaries. The underwing was also dark except for a prominent white area on the undersides of the bases of the primaries. The rectrices were dark and the central feathers were slightly elongated with pointed tips. We all agreed on the identification as a juvenile Parasitic Jaeger. Careful size comparisons to Franklin and Ring-billed Gulls eliminated juvenile Pomarine Jaeger, which also generally shows more white color on both surfaces of the wing. Juvenile Long-tailed Jaeger was eliminated on the basis of the pattern of white on the wing and size and wing proportions. We further concluded the bird was an intermediate or dark morph individual based on the dark plumage and lack of a contrasting paler head or rump. This represents the second accepted record of a Parasitic Jaeger for Nebraska. The only other record is of a juvenile picked up alive in Sheridan County on 23 Aug 1968 which died the next day (specimen number UNSM ZM12309) (Gates, Doris. 1969. Parasitic Jaeger rather than Skua. Nebraska Bird Review 37:31.). There are also five records of Pomarine Jaegers and a single Long-tailed Jaeger record for Nebraska. Another 16 reports are of jaegers that were not identified to species.
Citation InformationStephen J Dinsmore and W. Ross Silcock. "Parasitic Jaeger at Lake McConaughy" (1998)
Available at: http://works.bepress.com/stephen_dinsmore/39/