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Kirtland's Warbler and Its Bahama Wintering Grounds
Bruce E. Radabaugh
The Wilson Bulletin
Vol. 86, No. 4 (Dec., 1974), pp. 374-383
Published by: Wilson Ornithological Society
Stable URL: http://www.jstor.org/stable/4160537
Page Count: 10
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The population of Kirtland's Warbler declined from an estimated 1,000 in 1961 to about 400 in 1971. Principle causes appear to be parasitism by the Brown-headed Cow-bird and a possibly inadequate amount of breeding habitat. The species requirements on its wintering grounds in the Bahama Islands are virtually unknown. Necessary conditions there may be worsening. Most of the winter records of Kirtland's Warbler are reviewed. I spent 800 hours in the field on 11 of the larger islands during the winters of 1971-1972 and 1972-1973, trying to find Kirtland's Warblers by means of recorded song, and surveying habitats and recent habitat changes. One male Kirtland's was seen on Crooked Island. The bird was under observation for just under two hours during three days--11, 12, and 22 March 1973. It occupied an area perhaps twice the size of an average breeding territory. This area consisted of low, broad-leaved scrub with a stunted habit, possibly due to the brackish ground water. The plants on this foraging area are described in some detail. The most profound habitat change observed has been the lumbering off of the Caribbean pines by the Owens-Illinois Company on the "pine islands" of Grand Bahama, Abaco, and Andros between 1956 and 1973. This destruction of the pine ecosystem may well have contributed to the recent decline in the Kirtland's Warbler population. It may be, however, that most of the population utilizes young or stunted broad-leaved scrub areas in winter. The proportions are unknown. A drought in the Bahamas and southern Florida in the winter of 1970-1971 may have led to the observed heavy loss of birds in the spring migration of 1971. This, too, may have contributed to the Kirtland's Warbler decline.
The Wilson Bulletin © 1974 Wilson Ornithological Society