42 
THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 124. No. 1. March 2012 
TABLE 1. Occurrence and total abundance of 
shorebirds (in decreasing order) from October 2007 to 
September 2000 on the coast of Rio Grande do Sul. 
southern Brazil. Status: seasonal visitor from the Northern 
Hemisphere (VN). seasonal visitor from the Southern 
Hemisphere (VS), and Resident (R). 
Species 
Slums 
Abundance 
* 
Sanderling 
Calidris alba 
VN 
78.247 
80.8 
White-rumped Sandpiper 
C. fiuscicollis 
VN 
7.588 
7.8 
Red Knot 
C. canutus 
VN 
5,103 
5.3 
Collared Plover 
Charadrius collaris 
R 
2.042 
2.1 
Lesser Yellowlegs 
Tringa flavipes 
VN 
1.517 
1.6 
Grey Plover 
Pluvialis squatarola 
VN 
822 
0.8 
Semipalmated Plover 
Charadrius semipalmatus 
VN 
547 
0.6 
Southern Lapwing 
Vanellus cliilensis 
R 
481 
0.5 
American Golden Plover 
Pluvialis dominica 
VN 
218 
0.2 
Ruddy Turnstone 
Arenaria inierpres 
VN 
127 
0.1 
Greater Yellowlegs 
Tringa rnelanoleuca 
VN 
95 
0.1 
Solitary Sandpiper 
T. solitaria 
VN 
36 
0.04 
Buff-breasted Sandpiper 
Tryngites subrupcoUis 
VN 
35 
0.04 
Whimbrel 
Numenius phaeopus 
VN 
17 
0.02 
Semipalmated Sandpiper 
Calidris pusilla 
VN 
7 
0.01 
Rufous-chested Plover 
Charadrius modestus 
VS 
6 
0.01 
Hudsonian Godwit 
Limosa haeinastica 
VN 
1 
0.001 
Totals 
96.889 100 
the aid ol 10 X 50 binoculars and use of field 
guides (Crossley et al. 2006, Mata et al. 2006). 
Flocks of shorebirds with <100 individuals were 
considered small, those with between 100 and 
1,000 individuals were considered medium-sized, 
and those with >1,000 individuals were consid¬ 
ered large. The seasons are in accordance with the 
Southern Hemisphere: austral summer (Oct to 
Mar) and austral winter (Apr to Sep). The 
frequency of occurrence (C) of each species was 
calculated using the equation C = 1 J x 100/A' in 
which P is the number of counts containing the 
species, and N is the total number of counts 
throughout the study period (n = 24). Classifica¬ 
tions recorded were: regular (present in >50% of 
counts), sporadic (present between 25 and 50% of 
counts), occasional (present <25% of counts), 
and absent (not present in counts) (Dajoz 1983). 
RESULTS 
Seventeen species of shorebirds were recorded, 
six species of Charadriidae and 11 Scolopacidae, 
totaling 96.889 individuals. Sanderlings (Calidw 
alba). White-rumped Sandpipers (C. fuscicoUh). 
and Red Knots (C. canutus) were the most 
abundant species, accounting for 93.9% of the 
overall abundance. Sanderlings accounted for 
80.8% of the overall abundance. Collared Plover 
(Charadrius col laris) and Lesser Yellowlegs 
(Tringa flavipes) accounted for >1% of the overall 
abundance, whereas the remaining 12 species 
accounted for <1% (Table 1 j. The greatest 
abundance of shorebirds occurred between October 
(arrival at stopover or wintering areas) and April 
(return to breeding areas), and the lowest occurred 
between May and September (Fig. 2). 
Nine species were recorded regularly over a 2-year 
period (2007 to 2009) (all but the Red Knot were also 
regular when years were analyzed separately/ two 
were sporadic, and six were occasional (Table 2). 
The Hudsotiian Godwit (Limosa haemastica ) was 
absent throughout the 2007/2008 period and only one 
individual was recorded in January 2009. The 
Rufous-chested Plover (Charadrius modestus). a 
visitor from the Southern Hemisphere, was recorded 
as occurring occasionally. One individual was 
recorded in July 2008 and five were recorded in 
May 2009, Five Semipalmated Sandpipers (Calidris 
pusilla ) were observed in February 2008 and two in 
September 2009. Six Buff-breasted Sandpiper^ 
(Tryngites mbruficollis) were observ ed in November 
2007 and 29 (distributed among three sites) were 
recorded in October 2008. Abundances during 
monthly surveys varied seasonally (Fig. 3). 
The frequency of occurrence of the Southern 
Lapwing (Vanellus chilensis), a resident species, was 
regular as it was recorded in all counts. The greatest 
abundance of this species occurred between April aid 
July with a peak (n = 81) in July 2008. and was 
lowest between October and December with only one 
individual recorded in November 2008. The Amer¬ 
ican Golden Plover (Pluvialis dominica) was occa¬ 
sional but present in 4 months with a peak (n = 126) 
in February 2009; six individuals were recorded in 
April in the 2007/2(X)8 period. The frequency of 
occurrence of Grey Plovers (P. squatarola) was 
