Tulsa Audubon Society
Year 2002 Zink Island and 71st Street Island
Least Tern Breeding Survey
Robert J. Harwood
Least Tern Observers: Ann Burke, Bill Carrell, Colin Davy, Lynda Fritts, Bob Harwood, Jo Loyd, Tomye Mainer, Janet Slater, Gail Storey, Suzy Tramel
The least tern breeding success was even poorer this year than last year, possibly because of the negative impacts of flooding and Canada geese.
The purpose of the least tern breeding survey is to determine the breeding success this year in comparison to previous years. This year another island was surveyed in addition to Zink Island, the latter which is man made and built-up several feet above river level. A large low-lying island south of 71st street was added to the survey because of appreciable least tern nesting observed the past year in this location. The survey extended from May 5 to August 18 this year, an extension necessitated by the late arrival of the least terns and extensive flooding in mid June. Heavy rains in mid June upstream from Keystone Dam required large releases of water, which partially flooded Zink Island and completely flooded the 71st street island for approximately a week. The nesting on Zink Island was somewhat impacted, but on the 71st street island the nests were completely washed away and nesting had to begin anew after the flooding had subsided. Zink Island was treated for vegetation removal by the U.S. Corps of Engineers and the U.S. Fish and Wildlife Service before the nesting season, but the vegetation rapidly grew back. Also, large numbers of Canada geese were present on and around Zink Island during the breeding season.
I would like to thank all the members of the survey team for the time spent in collecting the excellent data. Also, as before I would like to thank Neely Lowrie for his very useful advice. We wish success to the new least tern chairman, Colin Davy, who will start in late September.
(1) The breeding success was even poorer this year than last year. Only 6 chicks were fledged on Zink Island and on 71st Street island as opposed 18 fledged on Zink Island last year. The ratios of fledged/nests this year are 0.35 (Zink) and 0.29 (71st St.) as opposed to 0.43 (Zink) last year.
(2) The nesting season appeared to begin two weeks late this year.
(3) The vegetation rapidly grew back on Zink Island during the year making counting of chicks, fledged young , and adults difficult.
(4) Large numbers of both adult and young Canada geese were seen in the vicinity of nesting least terns on Zink Island.
The vegetation should be removed from Zink Island with a stronger herbicide before next year’s least tern breeding season. Also, the Canada geese should be trapped and removed before least tern nesting next year.
The least tern breeding success is even worse in terms of numbers and ratios of fledged/nests this year than last year (Figures 1a,b, 2, 3). Only 6 young fledged on each of the islands this year, whereas 18 young fledged on Zink Island last year (Figure 2). The fledged/nest ratios this year are 0.35 and 0.29 versus 0.43 (Zink) last year (Figure 3). Numbers of adults after the flooding were down as compared to last year, 59 at Zink Island and 44 at 71st Street compared to 93 adults at Zink last year (Figure 3). Even before the flooding the arrival of the adults appeared delayed by two weeks, and the flooding then caused even more delay and damage to breeding. Growth back of vegetation on Zink Island made counting chicks, fledged young, and adults difficult in the hot weather because they would be in the vegetation to escape the heat. Large numbers of Canada geese on and around the nesting areas of Zink Island continued to be a problem as in previous years.
In this unusual year the success of the least tern breeding continues to decline in the Tulsa area.
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