Seasonal variations in shorebird abundance in the state of Rio Grande Do Sul, Southern Brazil.
Abstract: We describe the frequency of occurrence and seasonal variations of shorebirds (Charadriidae and Scolopacidae) along a 120-kin transect of beach between Balneario Pinhal and Mostardas north of Lagoa do Peixe National Park, Rio Grande do Sul State over a 2-year period (Oct 2007 to Sep 2009). A total of 96,889 shorebirds was recorded. The greatest abundance occurred between October and April and the lowest occurred between May and September. The most abundant of the 17 species recorded were Sanderlings (Calidris alba), Wbite-rumped Sandpipers (C. fuscicollis), and Red Knots (C. canutus). The least abundant were Semipalmated Sandpipers (C. pusilla), Rufous-chested Plovers (Charadrius modestus), and Hudsonian Godwits (Limosa haemastica). Fourteen species were migrants from the Northern Hemisphere, one was a migrant from the Southern Hemisphere, and two were residents. Nine species were recorded regularly, two were recorded sporadically, and six were recorded occasionally. Six Nearctic species were recorded in June and July most likely indicating the presence of non-breeding immatures. The beaches of Rio Grande do Sul are important migration stopover and wintering sites for many shorebirds in southern Brazil and should be a focus of conservation efforts, especially given the increasing development pressure that threatens these areas.
Article Type: Report
Subject: Shore birds (Physiological aspects)
Shore birds (Environmental aspects)
Authors: Scherer, Angelo L.
Petry, Maria V.
Pub Date: 03/01/2012
Publication: Name: The Wilson Journal of Ornithology Publisher: Wilson Ornithological Society Audience: Academic Format: Magazine/Journal Subject: Biological sciences Copyright: COPYRIGHT 2012 Wilson Ornithological Society ISSN: 1559-4491
Issue: Date: March, 2012 Source Volume: 124 Source Issue: 1
Topic: Event Code: 310 Science & research
Geographic: Geographic Scope: Brazil Geographic Code: 3BRAZ Brazil
Accession Number: 285207240
Full Text: Brazil is visited by thousands of birds that migrate seasonally from the Northern to Southern Hemisphere and vice-versa (Morrison and Ross 1989, Chesser 1994). Those that come from the north prior to the boreal winter (Antas 1994) arrive in Brazil seeking wintering sites rich in food resources (Telino-Junior et al. 2003). Shorebirds from the Northern Hemisphere occur in Brazil during the austral summer and those from the Southern Hemisphere occur in the country during the austral winter. Immature individuals of certain shorebirds occur throughout nearly the entire year, as they are not yet capable of breeding and return to breeding areas only when they are sufficiently mature to begin nesting (Sick 1979, Azevedo-Junior and Larrazabal 1994, Azevedo-Junior et al. 200la, b).

The sites at which shorebirds stop during migrations are of considerable importance for conservation. Lagoa do Peixe National Park and nearby beaches on the coast of the State of Rio Grande do Sul in southern Brazil attract large concentrations of migratory shorebirds (Lara-Resende and Leeuwenberg 1987, Morrison and Ross 1989, Vooren and Chiaradia 1990, Belton 2000). The availability of food resources at these sites offers the birds the opportunity to gain body mass and acquire adequate energy for molting and return to breeding areas (Azevedo Junior et al. 200la, b; Baker et al. 2004, Fedrizzi et al. 2004).

Shorebird populations fluctuate during the breeding and wintering periods in number of individuals and migratory species using the beaches of southern Brazil (Lara-Resende and Leeuwenberg 1987, Barbieri et al. 2003, Telino-Junior et al. 2003, Barbieri and Mendonca 2005). The greatest abundance occurs from September to April along the Brazilian shoreline with slight temporal variations (Barbieri 2007, Barbieri and Hvenegaard 2008, Barbieri and Paes 2008). In southern Brazil, Lara-Resende and Leeuwenberg (1987) found the highest abundance of shorebirds from November to April in Lagoa do Peixe National Park (Ramsar site) (31[degrees] 21' S; 051[degrees] 03' W). The beaches from Balneario Pinhal to Mostardas, which are north of this conservation unit, offer adequate stopover, feeding, and resting sites for migratory shorebirds and are important locations for their conservation (A. L. Scherer, pers. obs.).

The coast of Rio Grande do Sul is considered a key area for shorebird conservation in the Western Hemisphere (Serrano 2008). Our objectives were to: (1) record the occurrence and seasonal variations of shorebirds (Charadriidae and Scolopacidae) along a 120-kin transect of beach north of Lagoa do Peixe National Park, and (2) document the frequency of occurrence of species of shorebirds over a 2-year period.

[FIGURE 1 OMITTED]

METHODS

Study Area.--We studied shorebirds along the coast of the State of Rio Grande do Sul (southern Brazil) between the municipalities of Mostardas in the south (31[degrees] 10' 52" S, 050[degrees] 50' 03" W) and Balneario Pinhal in the north (30[degrees] 14' 57" S, 050[degrees] 13' 48.4" W), totaling 120 km of beach (Fig. 1). The area is characterized by large sandy beaches and dunes with a series of coastal lakes beyond the dunes (Belton 2000). Human occupation along this region has altered the landscape, which is used for tourism and recreation. Fifteen kilometers of shoreline in Balneairio Pinhal are highly urbanized and the entire region is used intensively for irrigated crops and tree plantations.

The climate of the region is wet subtropical with a mean temperature of 17[degrees]C and annual rainfall of 1,200 mm. The width of the 120-km stretch of beach ranges from 50 to 120 m, at times reaching 200 m. The beach has a low slope and the wash zone is broad, generally ~10 m with a high density of invertebrates. The dominant species are bivalve mollusks including yellow clams (Mesodesma mactroides) and wedge clams (Donax hanleyanus), crustaceans such as mole crabs (Emerita brasiliensis) and cirolanid isopods (Excirolana armata), and polychaetes (Euzonus furciferus and Spio gaucha) (Gianuca 1983).

Surveys.--Monthly surveys (n = 24) were conducted between October 2007 and September 2009 along the 120 km of beach in an automobile traveling from north to south at a maximum speed of 20 km/hr between 0700 and 1700 hrs. Direct counts were made of the individuals of each species (Bibby et al. 2000). Surveys were conducted by two observers on randomly chosen sunny days. Shorebird abundance was recorded at a distance (50 to 100 m) to keep birds from flushing. The first observer recorded the birds from the edge of the water to the middle portion of the beach and the second observer recorded the birds from this portion to the dunes, taking care to avoid recounts. Data were recorded on a portable voice recorder and field spreadsheets. Birds were identified with the aid of 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 considered 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 = P X 100/N, 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). Classifications 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 (Calidris alba), White-rumped Sandpipers (C. fuscicollis), 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 collaris) and Lesser Yellowlegs (Tringaflavipes) accounted for > 1% of the overall abundance, whereas the remaining 12 species accounted for <1% (Table 1). 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 Hudsonian 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 Sandpipers (Tryngites subruficollis) were observed 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 and 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 American Golden Plover (Pluvialis dominica) was occasional but present in 4 months with a peak (n = 176) in February 2009; six individuals were recorded in April in the 2007/2008 period. The frequency of occurrence of Grey Plovers (P. squatarola) was regular with greatest abundance occurring between October and February (n = 353 in Feb 2009) and lowest between April and September; this species was absent in June and July.

[FIGURE 2 OMITTED]

The frequency of occurrence of Semipalmated Plovers (Charadrius semipalmatus) was sporadic in the 2007/2008 period and regular in 2008/2009. The greatest abundance was recorded between February and March 2008, and between April and May 2009 with no records of occurrence between October and January in either year. The frequency of occurrence of Collared Plovers was regular and the species was recorded in all months. The greatest abundance of this species occurred between March and August, and was lowest between September and February. A large part of the increase in abundance beginning in March was due to the presence of young of the year, which were observed foraging in the wash zone and near the drainage sandbars of lakes. Abundance was considerably higher in May, June, and August 2008 than during the same period in 2009.

[FIGURE 3 OMITTED]

The frequency of occurrence of Whimbrels (Numenius phaeopus) was occasional as the species was absent in 2007/2008 and sporadic in 2008/2009. The greatest number of individuals was recorded in November 2008 (n = 6) and May 2009 (n = 9). Only one individual was observed in each of two other months. Solitary Sandpipers (Tringa solitaria) occurred sporadically in 2007/ 2008 and occasionally in 2008/2009. This species had no clear tendency of occurrence, but was recorded in two consecutive months (Nov and Dec 2007) with greatest abundance (n = 18) in November 2007.

The frequency of occurrence of Greater Yellowlegs (T. melanoleuca) was regular over both years. The greatest abundance occurred between May and September with a peak in July 2008 (n = 16) and in September 2009 (n = 16). This species exhibited abrupt variation from one month to the next as observed in May, June, and July 2008 with 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. Abundance beginning in May 2008 increased the following month and then decreased until September 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 interpres) 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 individuals 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 third 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 (n = 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 was 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, respectively; 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 beginning and end of this period. Peaks (n = 5,943) were recorded at the beginning of the austral summer (Nov 2007) and beginning (n = 10,757) of the austral winter (Apr 2008); the same pattern was observed in October 2008 (n = 8,296) and April 2009 (n = 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 = 7) and August (n = 3) 2008.

The frequency of occurrence of White-rumped 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 (Balneario 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 recorded 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 reproductively immature juveniles (Semipalmated Plover, 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-Junior and Larrazabal 1994, Azevedo-Junior et al. 200la, b; Barbieri and Mendonca 2005, Barbieri and Hvenegaard 2008).

The most frequent and abundant species on the beaches between Balneario 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 are among the most important wintering areas on the Atlantic Coast of South America for Sanderlings (Morrison and Ross 1989). The three species are highly abundant in Lagoa do Peixe National Park (Lara-Resende and Leeuwenberg 1987), using the area as either a wintering site or stopover point for the part of the population that winters in areas further south, such as Tierra del Fuego (Harrington et al. 1986, Morrison et al. 2004, Piersma 2007).

Nine species had a regular frequency of occurrence over the 2-year period, whereas other species occurred occasionally and in low abundance (Rufous-chested Plover, Hudsonian Godwit, Semipalmated Sandpiper, and Buff-breasted Sandpiper). The Rufous-chested Plover is an austral winter visitor from Patagonia, where it breeds (Belton 2000). This species occurs in low abundance on the beaches of southern Brazil (Lara-Resende and Leeuwenberg 1987, Vooren and Chiaradia 1990, Belton 2000) and Argentina (Blanco et al. 2006). Hudsonian Godwits occur throughout the year in Lagoa do Peixe with highest abundance in November during its migration south (up to 1,300 individuals) and in March prior to migration north (Lara-Resende and Leeuwenberg 1987). Up to 3,000 individuals have been recorded at the site (Harrington et al. 1986, Morrison and Ross 1989). This species is highly sensitive to disturbed environments (Parker et al. 1996) and is rarely seen on beaches with people and vehicles. The Semipalmated Sandpiper occurs with low frequency and abundance in southern Brazil (Lara-Resende and Leeuwenberg 1987, Vooren and Chiaradia 1990, Costa and Sander 2008), but is frequent and abundant on beaches of northern and northeastern Brazil, where it winters (Morrison and Ross 1989, Azevedo-Junior et al. 2001b, Telino-Junior et al. 2003, Barbieri 2007).

The Buff-breasted Sandpiper is considered endangered (BirdLife International 2011) and occurs in wet grassland areas and grazed pasturelands near lagoons (Lara-Resende and Leeuwenberg 1987, Lanctot et al. 2002). This species generally migrates through the interior of the continent, using the central Amazon/ Pantanal wetland route, where it follows large rivers and wetlands until reaching Paraguay and Argentina (Antas 1984). This explains the low frequency and abundance on the beaches between Balneairio Pinhal and Mostardas, where it was recorded on only two occasions (Nov 2007 and Oct 2008).

The resident Southern Lapwing, which is endemic to South America, was among the species with regular frequency of occurrence and was observed on all counts. This species is common in grassland areas of Rio Grande do Sul, where it breeds, and Belton (2000) considered its occurrence on the shore as rare. It is observed with greater frequency foraging on the beach near sandbars with drainage of waters from lakes between April and July; lower numbers are observed between October and December when this species is in its breeding season (Belton 2000).

The American Golden Plover had a lesser frequency of occurrence and lower abundance than the Grey Plover with greatest abundance occurring between November and March, as previously reported for wintering areas in southern Brazil (Lara-Resende and Leeuwenberg 1987, Vooren and Chiaradia 1990). This species is found mostly on beaches within the proximity of Lagoa do Peixe (Morrison and Ross 1989) where they encounter habitat with less direct influence from humans and vehicles along the beach. The Grey Plover had low frequency and abundance along the beach throughout the year (Lara-Resende and Leeuwenberg 1987, Vooren and Chiaradia 1990).

The frequency of the Semipalmated Plover was uneven with greater abundance in February and March 2008, and April and May 2009. However, this species has been observed in low abundance in southern Brazil (Lara-Resende and Leeuwenberg 1987, Vooren and Chiaradia 1990). It is more abundant on beaches of northeastern Brazil, where most of the population winters (Rodrigues 2000, Telino-Junior et al. 2003, Barbieri 2007, Barbieri and Hvenegaard 2008). The resident Collared Plover, which breeds among the dunes along the Brazilian coast, occurs throughout the year. Little is known about this species. Its greatest abundance on the beaches between Balneario Pinhal and Mostardas was between March and August. This was during the breeding season, which extends from November to January, when the species is frequently found foraging near dunes where it breeds, as well as throughout the nonbreeding season in the austral winter (LaraResende and Leeuwenberg 1987, Belton 2000). Juveniles were observed foraging in the wash zone and drainage sandbars of lakes in every month of the year, but with a considerable increase beginning in March and greater abundance in the subsequent months.

Whimbrel occurred in low frequency and abundance. This species needs conserved environments due to high sensitivity to environmental disturbances (Parker et al. 1996). The largest flocks occur in the northern and northeastern regions of Brazil, and northern portion of South America (Morrison and Ross 1989, Azevedo-Junior and Larrazabal 1994, Azevedo-Junior et al. 2004). This species in southern Brazil is only observed foraging in small numbers in Lagoa do Peixe (n < 8) (Lara-Resende and Leeuwenberg 1987) and in the surrounding beaches.

Solitary Sandpipers were observed sporadically and in small numbers along the beach, as reported by Costa and Sander (2008) on other beaches in Rio Grande do Sul. Greater Yellowlegs were observed regularly in both years as reported by Lara-Resende and Leeuwenberg (1987) with peaks of abundance in July and September, but was much rarer than Lesser Yellowlegs. Many non-migrating individuals of Greater Yellowlegs that winter in interior areas of the state, according to Belton (2000), concentrate on the beach during the austral winter. Lesser Yellowlegs are recorded in every month of the year in Rio Grande do Sul, appearing rarely during the austral winter and more commonly from September to March (Belton 2000). However, we found the species was more abundant between May and October and was rare between November and April. Those observed from May to July were likely flocks of juveniles that had wintered on the beaches and lakes in the interior of Rio Grande do Sul and then concentrated on the coast. The greatest abundance in October coincides with migration to South America with the species using beaches and lakes as either wintering or stopover areas. Lesser and Greater yellowlegs were observed foraging on the banks of small lakes near dunes and drainage sandbars of these lakes and, at times, in the wash zone.

The Ruddy Turnstone is common along the coast of the Province of Buenos Aires (Myers and Myers 1979, Blanco et al. 2006) during the austral summer. We found low abundance of this species on the beaches from Balneario Pinhal to Mostardas with greater frequencies occurring between April and July, and between September and December. This has also been reported in previous studies (Harrington et al. 1986, Lara-Resende and Leeuwenberg 1987, Vooren and Chiaradia 1990). This indicates that small groups stop to feed and rest during migrations south and north between wintering and breeding areas in Argentina and the Northern Hemisphere, respectively.

The pattern of occurrence of the Red Knot corroborates that observed at other sites in southern Brazil (Lara-Resende and Leeuwenberg 1987, Vooren and Chiaradia 1990). The greater abundance in September indicates arrival of migrants from the Northern Hemisphere moving toward wintering areas in Patagonia and Tierra del Fuego. This species use the lakes and beaches of Rio Grande do Sul as stopover areas for feeding, resting, and molting. A few individuals remain in winter and join flocks that stopover in April on return to breeding areas in the Northern Hemisphere. The stopover period on the beaches from Balneario Pinhal to Mostardas is short, but of considerable importance to the migratory process between the extremes of the two hemispheres (Piersma 2007). This beach serves as one of the most important stopover sites during the molting process and for gain in body mass (Morrison and Ross 1989, Vooren and Chiaradia 1990).

The regular frequency throughout the year and high abundance of Sanderlings confirms the beaches of Rio Grande do Sul are one of the most important wintering areas for this species along the Atlantic Coast of South America (Harrington et al. 1986, Lara-Resende and Leeuwenberg 1987, Morrison and Ross 1989, Myers et al. 1990). Large flocks begin to arrive in September with peak abundance in October and a decrease in the following month as the areas are used as a stopover site during migration farther south to wintering areas. The abundance of Sanderlings remains stable from November to February because of individuals that winter in the area, decreases from February to March, when these same individuals begin to migrate north, and reaches its largest peak in April, when those that wintered to the south (Argentina and Patagonia) again use the site as a stopover, and declines in May. We found the species in greater densities than at other sites in southern Brazil (Vooren and Chiaradia 1990, Costa and Sander 2008), indicating greater availability of food resources on these beaches and lower human impacts.

White-rumped Sandpipers occurred in numbers and pattern of occurrence similar to that of the Red Knot. This species is reported in Lagoa do Peixe to be highly abundant between November and January, both on the lake and the beach (LaraResende and Leeuwenberg 1987), and part of the population uses the site as stopover and wintering areas (Morrison and Ross 1989). The greatest abundance occurs at the beginning of the austral summer with arrival of migrants from the Northern Hemisphere to winter in Lagoa do Peixe and Argentina, where they are abundant throughout the austral summer (Myers and Myers 1979, Lara-Resende and Leeuwenberg 1987, Morrison and Ross 1989, Blanco et al. 2006). We observed a few individuals on the beaches from Balneario Pinhal to Mostardas during the austral summer with abundance increasing at the beginning of the austral autumn (Mar and Apr), when the population returns from wintering areas on migration to North America. This indicates the importance of these beaches for stopover and feeding sites prior to migration.

CONSERVATION IMPLICATIONS

Knowledge of stopover and wintering areas is critical to the conservation of migratory shorebirds, as these sites require special care (LaraResende and Leeuwenberg 1987, Myers et al. 1990) through an internationally coordinated effort directed at protecting breeding, stopover, and wintering areas (Morrison 1984, Morrison et al. 2004). The beaches from Balneario Pinhal to Mostardas in the State of Rio Grande do Sul (southern Brazil) are used by large numbers of shorebirds as stopover and wintering areas, especially Sanderlings, White-rumped Sandpipers, and Red Knots. Our study underscores the importance of these beaches as priority areas for implementation of conservation projects directed at these shorebirds and serves as a basis for future comparisons addressing the impact of environmental changes on these species (Piersma and Lindstrom 2004).

ACKNOWLEDGMENTS

The authors are grateful to the Wildlife Conservation Society (WCS) for funding this study (Contract # 2008005). A. L. Scherer is grateful to the Brazilian fostering agency Coordenacao de Aperfeicoamento de Pessoal de Ensino Superior (CAPES) for a study grant awarded from the Programa de Suporte a Pos-Graduacao de Instituicoes de Ensino Particulares (PROSUP). We thank R. G. de Moura for help drawing Figure 1, and S. M. Azevedo-Junior and L. R. Oliveira for helpful comments and reviews.

Received 10 February 2011. Accepted 25 October 2011.

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ANGELO L. SCHERER (1,2) AND MARIA V. PETRY (1)

(1) Graduate Program in Biology, Laboratory of Ornithology and Marine Animals, Center for Health Sciences, Universidade do Vale do Rio dos Sinos, Avenida Unisinos, 950, 93022-000, P. O. Box 275, Room 2D223E, Sao Leopoldo, Rio Grande do Sul, Brazil.

(2) Corresponding author; e-mail: alscherer@pop.com.br
TABLE 1. Occurrence and total abundance of
shorebirds (in decreasing order) from October 2007 to
September 2009 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                      Stains   Abundance     %

Sanderling
  Calidris alba              VN        78,247      80.8
White-rumped Sandpiper
  C. fitscicollis            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 flc?vipes           VN         1,517       1.6
Grey Plover
  Pluvialis syuatarola       VN           822       0.8
Semipalmated Plover
  Charadrius semipalmc?tus   VN           547       0.6
Southern Lapwing
  Vanellus chilensis         R            481       0.5
American Golden Plover
  Pluvialis dominica         VN           218       0.2
Ruddy Turnstone
  Arenaria interpres         VN           127       0.1
Greater Yellowlegs
  Tringa melanoleuca         VN            95       0.1
Solitary Sandpiper
  T. solitaria               VN            36       0.04
Buff-breasted Sandpiper
  Tryngites subruficollis    VN            35       0.04
Whimbrel
  Numenius phaeopus          VN            17       0.02
Semipalmated Sandpiper
  Calidris pusilla           VN             7       0.01
Rufous-chested Plover
  Charadrius madestus        VS             6       0.01
Hudsonian Godwit
  Limosa haemastica          VN             1       0.001
Totals                                 96,889     100

TABLE 2. Frequency of occurrence (C) of shorebirds from October 2007
to September 2009 on the coast of Rio Grande do Sul, southern Brazil.

                          Oct 2007 to Sep 2008   Oct 2008 to Sep 2009

Species                     C      Constancy     C     Constancy

Southern Lapwing           100     Regular       100   Regular
American Golden Plover       8     Occasional     33   Sporadic
Grey Plover                 58     Constant       83   Regular
Semipalmated Plover         33     Sporadic       50   Regular
Collared Plover            100     Regular       100   Regular
Rufous-chested Plover        8     Occasional      8   Occasional
Hudsonian Godwit             0     Absent          8   Occasional
Whimbrel                     0     Absent         33   Sporadic
Solitary Sandpiper          33     Sporadic       17   Occasional
Greater Yellowlegs          50     Regular        67   Regular
Lesser Yellowlegs           83     Regular        92   Regular
Ruddy Turnstone             67     Regular        58   Regular
Red Knot                    67     Regular        33   Sporadic
Sanderling                 100     Regular       100   Regular
Semipalmated Sandpiper       8     Occasional      8   Occasional
White-rumped Sandpiper      83     Regular        67   Regular
Buff-breasted Sandpiper      8     Occasional      8   Occasional

                          2007 to 2009

Species                     C    Constancy

Southern Lapwing          100    Regular
American Golden Plover     21    Occasional
Grey Plover                71    Regular
Semipalmated Plover        42    Sporadic
Collared Plover           100    Regular
Rufous-chested Plover       8    Occasional
Hudsonian Godwit            8    Occasional
Whimbrel                   17    Occasional
Solitary Sandpiper         25    Sporadic
Greater Yellowlegs         58    Regular
Lesser Yellowlegs          88    Regular
Ruddy Turnstone            63    Regular
Red Knot                   58    Regular
Sanderling                100    Regular
Semipalmated Sandpiper      8    Occasional
White-rumped Sandpiper     75    Regular
Buff-breasted Sandpiper     8    Occasional
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