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THE WILSON JOURNAL OF ORNITHOLOGY • Vol 124. No. 1. March 2012 
13, 1, and 16 individuals observed, respectively. 
December. March, and April were the only 
months in which there were no records of this 
species. The frequency of occurrence of Lesser 
Yellowlegs was regular over both years with 
greatest abundance between May and October, 
and lowest between December and April. Abun¬ 
dance beginning in May 2008 increased the 
following month and then decreased until Sep¬ 
tember with a significant increase in October 
2008, reaching 270 individuals before rapidly 
declining in November. This species was absent in 
October and November 2007. and April 2009. 
Ruddy Turnstones (Arenaria interpret,) were 
regularly observed every month of the 2-year 
period, and had low abundance ranging from one 
to six individuals. However, 15 individuals were 
observed in December 2007 and the greatest 
abundance occurred in April 2009 with 70 in¬ 
dividuals distributed among three flocks of 30, 15. 
and 25 individuals spatially separated I and 7 km 
from one another, respectively. 
The Red Knot was the ihird most abundant 
species and was observed regularly in the first 
year and sporadically in the second year. The 
greatest abundance occurred between April and 
September with uneven distribution among the 
remaining months of the year. Monthly abundance 
in 2008 ranged from 1,669 individuals in April to 
96 individuals in May, and rising in June and July. 
A considerable number of individuals (/? = 322) 
was recorded in April 2009. but only four were 
observed in May, none in June or July, before 
becoming abundant in September (n = 1.562). 
This species w'as absent in December and March 
with only one individual recorded in February 
2009, two individuals in October 2007, and two in 
January 2008. Thirty-eight and 71 Red Knots 
were observed in June and July 2008, respective¬ 
ly; some were in nuptial plumage while in flocks 
with non-breeding plumage birds, which were 
likely not migrants that year. 
The Sanderling was the most abundant species 
with regular frequency of occurrence. The greatest 
numbers occurred between September and April 
with an abrupt increase and decline at the be¬ 
ginning and end ol this period. Peaks (// = 5.943) 
were recorded at the beginning of the austral 
summer (Nov 2007) and beginnine (n = 10 757) 
o f the i f us >™' winter (Apr 2008); the same pattern 
in ° C ' 0ber 2I,0H = s - 2% ' and 
Apr.! 2009 („ = 9,759). The lowest abundance 
occurred between May and August, and flocks 
most likely consisted of non-breeding immature 
individuals. The lowest numbers were recorded in 
July (n = 1) and August (// - 3) 2008. 
The frequency of occurrence of White-ramped 
Sandpipers was regular and this species was the 
second most abundant. This species also had two 
yearly peaks of abundance with largest numbers 
in November 2007 (n = 1,204) and March 2008 
(n = 1,060). and in August 2008 (n = 561) and 
February 2009 (n = 1,012). This species was 
absent in May. June, and July in both years. 
DISCUSSION 
The presence of 17 species of shorebirds, some 
highly abundant, confirms the importance of the 
beaches (Balncario Pinhal to Mostardas) on the 
coast of Rio Grande do Sul State (southern Brazil) 
as stopover and wintering sites for migratory 
shorebirds. Fourteen species of shorebirds record¬ 
ed in the present study were migratory that breed 
in the Northern Hemisphere. These shorebirds use 
the beaches of Rio Grande do Sul as stopover or 
wintering areas for feeding and resting, mainly 
between October and April. This period coincides 
with greater availability of macroinvertebrates 
along the beaches and banks of coastal lakes 
(Lara-Resende and Leeuwenberg 1987). when 
lower water levels allow greater foraging area. 
The number of shorebirds was lowest between 
May and September when most populations 
migrate to breeding areas in the Northern 
Hemisphere. However, a small number of repro- 
ductively immature juveniles (Semipahnated Plo¬ 
ver. Greater Yellowlegs, Lesser Yellowlegs. Red 
Knot, Sanderling, and White-rumped Sandpiper) 
remain on the beach throughout the austral winter, 
as has also been reported for beaches in northern 
and northeastern Brazil (Azevedo-Jtinior and 
Larra/abal 1994, Azevedo-Junior et al. 2001a. b: 
Barbicri and Mendon^a 2005. Barbieri and 
Hvenegaard 2008). 
1 he most frequent and abundant species on the 
beaches between Balncario Pinhal and Mostardas 
were Sanderlings, White-rumped Sandpipers, and 
Red Knots. These species have previously been 
recorded on other beaches of Rio Grande do Sul 
( Lara-Resende and Leeuwenberg 1987. Vooren and 
Chiaradia 1990). The Rio Grande do Sul beaches ate 
among the most important wintering areas on the 
Atlantic Coast of South America for Sanderling 1 ' 
(Morrison and Ross 1989). The three species are 
highly abundant in Lagoa do Peixe National Park 
(Lara-Resende and Leeuwenberg 1987), using the 
