FACTORS AFFECTING NESTING SUCCESS OF COEXISTING SHOREBIRDS AT GREAT SALT LAKE, UTAH

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FACTORS AFFECTING NESTING SUCCESS OF COEXISTING
SHOREBIRDS AT GREAT SALT LAKE, UTAH John F.
Cavitt, Department of Zoology, Weber State
University
Results and Discussion
A total of 1,222 AMAV and 631 BNST nests were
located and monitored for this study. Nest
predation was the most important source of nest
failure at all sites (Figure 2). DSR differed
significantly between sites (AMAV X2 15.41 df
3 P 0.002 BNST X2 26.71 df 2 P
0.001). AMAV had the lowest DSR at SHORE
relative to the other sites and BNST had the
lowest DSR at BEAR (Figure 3). Both FARM and
BEAR utilize mammalian predator control. DSR
also differed significantly between years (AMAV
X2 19.63 df 2 P 0.002 BNST X2 33.7 df
2 P lt 0.001). The DSR for both species was
significantly lower in 2003 relative to 2004 and
2005 (Figure 4). This difference in DSR may be
related to reduced precipitation and spring
runoff during 2003. DSR increased throughout the
breeding season for both AMAV and BNST (Figure
5). I also broadly classified nests according to
their location (island, dike, marsh). For AMAV,
nest location significantly affected DSR (X2
17.57 df 2 P lt 0.002). Nests placed in open
marshes had significantly higher DSR relative to
those on dikes and islands (Figure 6). Nest
location did not significantly affect BNST DSR
(X2 0.124 df 2 P 0.940). Although both
BEAR and FARM utilize mammalian predator control,
predation continues to be a substantial source of
nest failure. The primary predators are
difficult to identify, but California Gull (Larus
californicus) breeding populations are large
(particularly at BEAR) and have increased over
the last three years.