R. Boettcher et al., HABITAT-RELATED FACTORS AFFECTING THE DISTRIBUTION OF NONBREEDING AMERICAN AVOCETS IN COASTAL SOUTH-CAROLINA, The Condor, 97(1), 1995, pp. 68-81
Changes in local environmental conditions can cause shifts in the dist
ribution of nonbreeding shorebirds at sites that offer a wide choice o
f habitats. We assessed effects of water level-related variables and s
alinity on the distribution of nonbreeding American Avocets (Recurviro
stra americana) among eight brackish water impoundments and two intert
idal mudflats in coastal South Carolina from mid-January to mid-May, 1
991 and 1992. Avocets exhibited nonrandom distribution on three spatia
l scales: between impoundments and natural tidal areas (impoundment us
e was greater), among impoundments, and within impoundments. Among all
sites, avocet distribution correlated with water level-related variab
les (P < 0.05), but not salinity. Most avocets used habitats with wate
r 10-17 cm deep and little or no exposed substrate. Furthermore, avoce
t numbers decreased in impoundments when the sites experienced large f
luctuations in water levels (+/-6-10 cm). Analyses conducted at the le
vel of one impoundment supported these results, indicating that macro-
(among impoundments) and microhabitat (within impoundments) use was i
nfluenced by similar factors.