Bird Use Days

A bird day is defined as one bird spending 24 hours within the study area during the study period. The GSL bird use day five-year mean was 86,752,258 (Table 8). Data from 1997 were only used in the five-year mean calculations of selected suites of species in Table 10. The 1997 data were omitted from the other tables to minimize variation in individual year means, because the survey season in 1997 had eight fewer survey periods than the other four years.

Bird use days are noticeably smaller in 1999. Bird use days by avocets and stilts were greatest in 2000 and 2001, and for dowitchers and waterfowl in 1998. The years 2000 and 2001 showed greater bird use days for gulls. Herons and egrets seemed to be more uniform in their use of the lake through 1998-2000, but diminished in 2001. The greatest year of peep sandpiper presence was 2000, while for phalaropes the highest use year was 2001 (Table 9).

An examination of the five-year mean bird use days by suite reflects the importance of the lake to avocets, phalaropes, waterfowl, and gulls--each present at GSL in the millions of bird days (Table 10).

Table 8. Mean bird use days at Great Salt Lake by year, 1998-2001.

Year Mean Bird Days
1998 89,183,180
1999 77,469,285
2000 88,889,577
2001 85,349,660

Table 9. Annual bird use days at Great Salt Lake for selected suites of species.

Year Avocets
& Stilts
Dowitchers Waterfowl Gulls Herons & Egrets Peep Sandpipers Phalaropes
1998 8,815,020 1,669,340 38,070,840 16,164,400 227,635 1,434,150 4,630,780
1999 10,443,400 1,100,080 28,810,680 12,286,700 246,570 516,475 6,019,690
2000 15,776,080 792,795 23,412,310 19,671,630 238,620 3,198,305 9,135,470
2001 13,224,590 434,715 22,838,960 23,842,820 191,890 865,570 11,622,420

Table 10. Five-year mean bird use days at Great Salt Lake for selected suites of species.

Suite Mean Bird Days
Avocets & Stilts 14,696,844
Dowitchers 1,133,536
Waterfowl 32,563,640
Gulls 22,062,838
Herons & Egrets 262,739
Small Sandpipers 2,030,585
Phalaropes 7,044,632
All Waterbirds 86,752,258