American Avocet and Black­necked Stilt breeding status and  population trends at Kelowna, British Columbia, 1997­–2015

Les W. Gyug1 and Jason T. Weir2

1 Okanagan Wildlife Consulting, 3130 Ensign Way, West Kelowna, BC V4T 1T9

2 Dept. of Biological Sciences and Dept. of Ecology and Evolution, University of Toronto, 1265 Military Trail, ON  M1C 1A4

Abstract: The American Avocet (Recurvirostra americana) is a rare and localized breeder in British Columbia with the single largest known B.C. colony in the remnant southern half of Alki Lake in Kelowna. From 1997-2015, up to 27 nests with eggs were observed in a single year, although in some years there appeared to be no successful nesting. Pulses in spring of high numbers of avocets at Alki and Robert lakes in Kelowna appeared to be partly from avocets heading further north in B.C. on their spring migration. High numbers of avocets only appear to remain in Kelowna for the breeding season if water levels in Alki Lake are suitable to isolate nesting islands. Spring first arrival dates of avocets to Kelowna have become significantly earlier by, on average, 11 days from 1997-2015. Egg laying dates in 1999-2000 ranged between April 25 and June 22, while hatching dates ranged between May 29 and July 20. Mean clutch size from 1997-2001 was 3.97 eggs per clutch. Nesting success in terms of broods hatching was 33% in 1999 and 60% in 2000. Islands were used almost exclusively for nesting at Alki Lake (96% of 128 nests) from 1997-2015 with exact nesting locations in any given year depending on water levels and locations of islands in that year. At Robert Lake, where there were no nesting islands and nests were on shorelines, none of the ten avocet nests documented from 1997-2015 ever appear to have successfully fledged young, and only 20% appear to have ever hatched young. Black-necked Stilts (Himantopus mexicanus) were first recorded at Kelowna in 1988. They were recorded annually in spring in small numbers from 1998-2004 with the first unsuccessful nesting attempt at Alki Lake in 2004. They were recorded annually for short periods in the spring at Kelowna from 2007-2013 except in 2011 when none were recorded. One pair of stilts nested successfully at Alki Lake in Kelowna in 2014, while two pairs appeared to nest successfully in 2015.

Key words: American Avocet, Recurvirostra americana, Black-necked Stilt, Himantopus mexicanus, British Columbia, Alki Lake, Robert Lake, Kelowna, population, breeding status, nest success, clutch size

PDFicon Gyug,  L.W.  and  J.T.  Weir.  2017.  American  Avocet  and  Black­necked  Stilt  breeding  status  and  population  trends  at  Kelowna,  British Columbia, 1997–2015. British Columbia Birds 17:2–12. First published on­line May 2016.

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