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Use of Laguna de Bustillos, Chihuahua, by waterbirds during the 2011-2012 wintering season.

Introduction

Laguna de Bustillos, in the center of the Mexican state of Chihuahua, has been touted as an important wetland for waterbirds based on anecdotal information about large concentrations of migratory waterbirds and on the midwinter bird counts conducted by the U.S. Fish and Wildlife Service (USFWS). About 23,000 Snow Geese wintered in the interior lagoons of Mexico from 1958 to 1964, of which 1500 did so in Laguna de Bustillos (Bellrose, 1976). Although not specific for Bustillos, about 10,000 Northern Shovelers spend the winter in lagoons in the state of Chihuahua (Bellrose, 1976) and of the 10,500 White-fronted Geese that winter in Mexico, 6000 do so in interior lagoons and reservoirs (Bellrose, 1967).

Laguna de Bustillos was considered a Priority Wetland by the USFWS (Wilson and Ryan, 1997), a priority site for the conservation of the Mexican Duck (Anas diazi; Perez-Arteaga et al., 2002a), and a priority site for wildfowl conservation in Mexico (Perez-Arteaga et al., 2005). It was recognized as an Important Bird Area (AICA, in Mexico) in 1999 (http://avesmx.conabio.gob. mx/FichaRegion.html#AICA_62), and it was included among the important wetlands for the conservation of migratory waterbirds in Mexico (Ducks Unlimited de Mcxico, 2008). It is also considered a Priority Hydrologic Region and a Region of High Biodiversity by Mexico's Comision Nacional para el Conocimiento y Uso de la Biodiversidad (CONABIO, 2007; Arriaga et al, 2000). It has not been designated as a Ramsar site, although it meets the criteria to be included (Perez-Arteaga et al, 2002b). The most abundant waterbirds of the lagoon were said to be the Sandhill Crane (Grus canadensis), Snow Goose (Chen caenilescens), Ross's Goose (Chen rossii), and the Mexican Duck (Anas platyrhynchos diazi) (Comision para la Cooperacion Ambiental, 1999; based on unpubl. data by Ducks Unlimited de Mexico, A.C.).

Despite the touted importance of Laguna de Bustillos for waterbirds in several reports, there are no recent articles, academic or otherwise, providing field data. The only articles formally published on the lagoon pertain to water quality (Benavides et al., 2008; Rubio Arias et al 2005) and the possibilities of extracting its water for agriculture (Amado et al, 1993; Amado and Ortiz, 1999; Ortiz and Amado, 2001). All designations of the lagoon as biologically important have so far been based on the USFWS midwinter censuses, on workshops and experts meetings, and on unpublished data by Ducks Unlimited de Mexico, A.C. This paucity in published information on the waterbirds prevents the objective evaluation of its biological importance and the design of management objectives. As a first step in providing robust field data, we documented the use of Laguna de Bustillos by waterbirds throughout the 2011-2012 winter season.

Methods

STUDY AREA

Laguna de Bustillos (28[degrees]33'31"N, 106[degrees]45'50"W; Fig. 1) is an 11 X 7 km lagoon in die midst of a highly mechanized agricultural area in the center of the Mexican state of Chihuahua (Arellano and Rojas, 1956). It is a shallow, but usually permanent, water body fed by rainwater (mostly summer) through the San Antonio, Napavechi, La Vieja, and smaller unnamed washes (Arellano and Rojas, 1956; Berlanga-Robles et al., 2008). Its water level depends largely on the rainfall of the region and is, accordingly, highly variable among years. In drought years I he lagoon dries out entirely, as has happened in the early 1950s, 1990s, and in 2012 (M. Martinez, pers. comm.), due to low precipitation in those years, as well as the extraction of water for agriculture.

In the early 20th century, the shores of the lagoon were covered by sedges and grass that had been removed by grazing livestock by the 1960s (Saunders and Saunders, 1981). Currently, the shores are devoid of tall vegetation and have only small patches of sparse grass that is constantly grazed and trampled by livestock.

Several small villages that surround the lagoon, as well as one large city nearby, use it to discharge sewage waters (Benavides et al., 2008). It was suspected the lagoon received contaminants from a paper factory that was established on its shore in 1955 (Arellano and Rojas, 1956; Saunders and Saunders, 1981; Amado and Ortiz, 1999). Drewien et al. (1996) indicated pollution from the factory could have contributed to a Sandhill Crane decline, but impoundments constructed by 1993 to contain and treat the factory's effluents could lead to the improvement of water quality in the lagoon. Hunting, fishing, water extraction, and tourism also occur in or near the lagoon (Lopez-Saut et al., 2011).

SURVEYS

We surveyed the use of Laguna de Bustillos by waterbirds during the 2011-2012 season from 12 counting stations around the lagoon (Fig. 1). Distances between adjacent stations averaged 3.28 km but varied as a function of accessibility (Fig. 1). To characterize the area covered by each station, we measured pH, depth at 20 m from the shoreline, substrate characteristics, and presence of emergent vegetation (Table 1).

Waterbirds were counted or estimated on 14 occasions between October 2011 and April 2012, about every 13 d (Table 2). All stations were visited twice on two consecutive days, reversing the route on the second day. All waterbirds visible from each station that were less than 200 m away were identified and counted, if few, or estimated if too many to count individually. To estimate the number of individuals in large flocks, patches of uniform density were visualized using binoculars and a spotting scope, and groups of 10 or 20 birds within these patches were extrapolated to the entire area. Counts or estimations were usually performed in about 20 min.

DATA ANALYSIS

For each 2-d sampling event, the highest (ally for each species at each station was used as the best indicator of that site's use by the birds. High within-site variation mostly led to no significant differences in 2-way analysis of variance to determine whether there were effects of site and sampling period on the abundance of the most common species.

Results

During the 2011-2012 winter season, we recorded 280,000 waterbirds of 40 species in Laguna de Bustillos (Table 2). Of the 40 species, there were nine species of shorebirds, seven dabbling ducks, five diving ducks, four waders, three gulls, and two "geese" (one was light geese, which includes Snow and Ross' Geese), in addition to Ruddy Duck (Oxyura jamaicensis), American Coot (Fulica americana), White Pelican (Pelecanus erythrorhynchus), Double-crested Cormorant (Phalacrocorax auritus), Tundra Swan (Cygnus columbianus), Sandhill Crane, Caspian Tern (Hydroprogne caspia), and two species that could not be identified (one dabbling duck and one sandpiper). However, 37% of all waterbirds were light geese, and another 44% were Northern Shovelers (Anas clypeata), Sandhill Cranes, and White-fronted Geese (Anser albifrons; Fig. 2).

Abundance of waterbirds fluctuated and exhibited three peaks: mid-fall, early-winter, and mid-winter. However, a general pattern of increase from the initiation of the wintering season to a peak in early-winter, and a decrease to the end of the migratory season was evident (Fig. 3a). The highest number of species occurred in the fall (22 October 2011), after which it decreased steadily until the end of the wintering season (Fig. 3b). Caballos had the largest total abundance (67,416 individuals), followed by El Rincon, Favela, La Vieja, and Anahuac, which had about 30,000 each (Table 3). Some species were detected throughout the lagoon, while others showed a preference for specific sites (Fig. 4).

DISCUSSION

The highest richness of waterbirds at Laguna de Bustillos coincided with the fall southbound migration in North America. The steady decline in species after its maximum in mid-October reflects those species that use the area only as a stopover point. The highest waterbird numbers occurred later, with the arrival and increase in numbers of Snow/Ross's Geese and of Sandhill Cranes. These, along with Northern Shovelers and the Greater Whitefronted geese, comprised the majority of waterbirds using Laguna de Bustillos. By midwinter these populations were at their highest level. Hence, if the pattern of the 2011-2012 season occurs during a mid-winter Mexican Waterfowl Survey, the abundance of the most common users of the lagoon would be well recorded but that of several species that use the lagoon only as a Fall or Spring Stopover would not.

There were two drops in waterbird abundance for which we have no explanation. However, many species were affected simultaneously, especially in the 29 January 2012 drop, after which numbers increased. The simultaneous reduction of different species suggests local factors, such as disturbance, were involved. Local inter-wetlands movements could have occurred but cannot be addressed due to the lack of concurrent monitoring at other locations. These fluctuations in numbers point to the need for multiple observations throughout the season and across a greater number of wetland groups, rather than individual sites.

The dominant species at Bustillos were the light geese (Snow/Ross's): They began to arrive in early October and over the following weeks increased to 6000 individuals. Their highest numbers were in mid-winter (22,546 on 29 December 2011), and the species left the area in late winter-early spring. These species preferred sites at the NW part of the lagoon (Fig. 4), which consists of swallow waters and soft substrate.

In contrast with our recent data, between 1951 and 2000, the mid-winter population of light geese in Laguna de Bustillos fluctuated between 0 and 8660 (mean = 3323 [+ or -] 3230 SD; USFWS database). Hence, use of Laguna de Bustillos by these geese during our survey was several times higher. Indeed, during the 2006 USFWS mid-winter census there were already signs of their increase, as 12,350 individuals were counted. The mid-continent population of light geese has been increasing from the mid-1960s to the late 1990s (Ankney, 1996; Abraham et al., 2005; Alisauskas et al., 2006; U.S. Fish and Wildlife Service, 2011). However, the increase of light geese at Bustillos does not match this general increase in the mid-continent population as it occurred much later. Therefore, against a background of very large populations, the increase of light geese at Laguna de Bustillos is likely explained by-changes in local or regional conditions. Their local increase can be linked to a change in agricultural practices, as the area farmed in the region increased considerably after 2000, and changed from rain-fed to high-yield irrigated maize (Echanove-Huacuja, 2009; C.M., pers. observ.). This could have caused a large increase in the availability of post-harvest grains in the fields.

The Northern Shoveler was the second most abundant species in Laguna de Bustillos. Its overall abundance was relatively constant, although it exhibited some fluctuations in numbers. There were clear peaks in the fall (9227 on 22 October 2011), winter (8718 on 11 February 2012) and early spring (8466 on 23 March 2012). Therefore, the lagoon provides wintering habitat for some Shovelers and fall and late winter-early spring stopover habitat for others. About 10,000 Northern Shovelers have been estimated to spend the winter in Chihuahuan lagoons (Bellrose, 1976). Based on this estimate, Laguna de Bustillos is clearly an important location for the species. Our figures fall within the range of reported USFWS mid-winter counts. The broad tolerance of Northern Shovelers to different habitat conditions during the nonbreeding season (Dubowy, 1988) was reflected by its lack of preference for sites in the lagoon.

The Sandhill Crane began to arrive 22 October and had high numbers until its departure in early spring. Crane numbers fluctuated much throughout the season (Table 1), which suggests the possibility of them moving between different wetlands in response to a currently unknown factor (sensu Pogson and Lindstedt, 1991). As with the light geese, large numbers of Sandhill Cranes in Laguna de Bustillos occurred after decades of low values. Most USFWS mid-winter counts recorded no cranes and the few that did reported only a few hundred (maximum: 1400 in 1967). However, 42,000 cranes were estimated in February 1947, before the formal mid-winter surveys began (Saunders and Saunders, 1981) and 25,000 were estimated from the ground in January 1963 (Drewien et al., 1996). In contrast to the ground survey, during the mid-winter aerial count of that year, no Sandhill Cranes were detected in Bustillos, suggesting mid-winter aerial counts of this species should be interpreted with care and reinforces the need for multiple counts. Despite these caveats there seems to have been an increase in local Sandhill Crane numbers starting in 2006, when 6300 were counted during the mid-winter survey, coinciding with the increase in light geese. Along the middle Rio Grande Valley, Sandhill Crane numbers, although variable, increased from 1967 to 1995 and then decreased until 2001 (Mitchusson, 2003), after which no data are available. As with light geese, the increase in crane numbers at Laguna Bustillos coincided with the post-2000 agricultural shift, likely for the same reasons as the geese. Additionally, if agriculture has shifted from maize to less desirable crops in other wintering areas, cranes might be concentrating in Bustillos, where conditions have actually improved for them (Pogson and Lindstedt, 1991; Krapu et al., 2004). The cranes preferred the southern shores of the lagoon, which has gross sediments and hard substrate. As they do elsewhere (Krapu et al, 1984), the cranes were concentrated in a wide unvegetated inlet where they had unobstructed visibility for some distance.

Greater White-fronted Geese began arriving at about the time we began to monitor. On 7 October there were 325 individuals; 2 wk later, 2071; and 2 wk thereafter (4 November 2011), 5326. After this date they remained as a population of 1000-2000 individuals, until disappearing from the area in mid-January. The species reappeared in March, when we counted >2000 individuals, in tune with its northward spring migration. A large number of individuals use the area as a stopover during migration, both in fall and in spring, and a subset of them remain during part of the wintering season. Although the Greater Whitefronted Goose is lumped with Canada Goose (Branta canadensis) and Bean Goose (Anser fabalis) in the mid-winter censuses, under the name of "dark geese," the Canada Goose if present, occurs in low numbers (indeed, we did not record any), and the Bean Goose is very unlikely to be in our area.

During the mid-winter census, "dark geese" numbers have usually ranged 0-100s, except in 1955 (2415), 1956 (2345), 1980 (1460), and 1997 (2755). Our mid-winter counts of 2216 (29 December 2011) and 2547 (14 January 2012) are therefore among the higher counts for the species. These species, like the light geese, preferred the soft substrate areas of the northwestern section of die lagoon. The northwestern part of the lagoon has a softer finer-textured bottom; which becomes harder and thicker-grained as one progresses towards the southern part of the lagoon. The Favela site falls outside this pattern likely due to its sandy substrate and presence of vegetation, in the form of both emergent vegetation and as grassy patches.

From our study we conclude:

1. Laguna de Bustillos is an important waterbird area in North-Central Mexico, although mostly for Snow/White and Greater White-fronted Geese, Sandhill Cranes and, locally, Northern Shovelers. However, this importance could depend, at least to some extent, on the permanence of other, nearby lagoons, which would offer complementary habitat for birds, when moving from Bustillos after disturbance.

2. Importance of Laguna de Bustillos for Snow/Ross's Geese and Sandhill Crane has increased, particularly after 2000, probably due to an increase in irrigated maize agriculture. Therefore, increases in the efficiency of maize harvesting or change in crops grown in the area might negatively impact the populations of these species.

3. Greatest waterbird abundance was in January, but highest species richness, was in the fall. Hence, the results of the USFWS mid-winter census appear to be more useful for monitoring the abundance of certain species but not that of other species or overall species richness.

4. For management purposes Laguna de Bustillos should not be considered a uniform simple wetland, but the gradation in bottom characteristics, which promote differential use by waterbirds, should be taken into account when designing management strategies.

Acknowledgments.--We thank P. Gallegos, S. Tafova, M. Gutierrez. L. Villezcas, R. Anava, G. Trevizo, F. Zamudio, J. Zuniga, D. Yenegas, 15. Flores, P. Flores, and J. Flores for their assistance during fieldwork, and V. Ferreira and J. Luevano for suggestions during data analysis. Two anonymous reviewers greatly helped to improve this article. This work was carried out while C.M. held a M.Sc. scholarship from Consejo Nacional de Ciencia y Tecnologia and was carried out with economic support from the Centro de Investigacion Cientifica y de Educacion Superior de Ensenada, B.C.

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Submitted 15 September 2015

Accepted 29 March 2017
Appendix.--Scientific names of species recorded at Laguna Bustillos
during the 2011-2012 winter season

Common name                   Scientific name

Greater White-fronted Goose   Anser albifrons
Snow/Ross's Goose             Chen sp.
Tundra Swan                   Cygnus columbianus
Mexican Duck                  Anas diazi
Mallard                       Anas platyrhynchos
Green Teal                    Anas crecca
Gadwall                       Anas strepera
Pintail                       Anas acuta
American Wigeon               Anas americana
Northern Shoveler             Anas clypeata
Unidentified dabbling duck    Anas sp.
Redhead                       Ay thy a americana
Ring-necked Duck              Aythya collaris
Canvasback                    Aythya valisineria
Lesser Scaup                  Aythya afpnis
Bufflehead                    Bucephala albeola
Ruddy Duck                    Oxyura jamaicensis
Eared Grebe                   Podiceps nigricollis
Clark's Grebe                 Aechmophorus clarkii
Double-crested Cormorant      Phalacrocorax auritus
American White Pelican        Pelecanus erythrarhynchos
Great Blue Heron              Ardea herodias
Cattle Egret                  Bubulcus ibis
White-faced Ibis              Plegadis chihi
American Coot                 Fulica americana
Sandhill Crane                Grus canadensis
Killdeer                      Charadrius vociferans
Semipalmated Plover           Charadrius semipalmatus
Black-necked Stilt            Himantopus mexicanus
American Avocet               Recurvirostra americana
Solitary Sandpiper            Tringa solitaria
Spotted Sandpiper             Actitis mandarins
Long-billed Curlew            Numenius americanus
Generic sandpiper             Calidris sp.
Long-billed Dowitcher         Limnodromus scolopaceus
Wilson's Phalarope            Phalaropus tricolor
Laughing Gull                 Leucophaeus atricilla
Ring-billed Gull              Larus delawarensis
Herring Gull                  Larus argentatus
Unidentified Gull             Larus sp.
Caspian Tern                  Hydroprogne caspia.


CINTHIA MIRELES (1) and ERIC MELLINK (2)

Centro de Investigation Cientifica y Education Superior de Ensenada, Carretem Ensenada-Tijuana # 3918, 22860 Ensenada, B.C., Mexico

(1) Present address: Heroico Colegio Militar #23; 31100 Chihuahua, Chih., Mexico

(2) Corresponding author: e-mail: emellink@cicese.mx

Caption: Fig. 1.--Location of Laguna de Bustillos, Chihuahua, Mexico and waterbird monitoring stations during the 2011-2012 winter season. The numbers between two sites indicates the linear distance between them

Caption: Fig. 2.--Abundance of waterfowl species in Laguna de Bustillos during the 2011-2012 winter season

Caption: Fig. 3.--Waterbird abundance and species richness in Laguna de Bustillos, northern Mexico during the 2011-2012 winter season

Caption: Fig. 4.--Site preference of the four main waterfowl species that used Laguna de Bustillos in the winter season 2011-2012. Bars indicate their mean abundance, and the numbers above them are coefficient of variation (CV) values. Stations without bar and CV were not used by the species. The white graphs exhibit each species' pattern of abundance along the season
Table 1.--Characteristics of the study sites at Laguna Bustillos

Station         Depth (cm)    Substrate     Emergent vegetation

Caballos          0-2.5      Silly-clay             Yes
La Vieja          0-2.5      Silty-clay             No
El Rincon         0-2.5      Silty-clay             No
Los Taraises      0-2.5      Silty-clay             No
Favela             2--12      Sand                Abundant
Anahuac            2-12      Sand                Abundant
Potreros           4-15      Sand with              Yes
                             some cobbles
Campos             2-10      Sand                   No
La Cal             2-15      Sand                   No
La Cruz            5-20      Sand                   No
La Selva          10-70      Sand                   No
Centro Calles      5-15      Cobbles                Yes

Table 2.--Abundance of waterbirds in Laguna de Bustillos
throughout the 2011-2012 winter season. Values given are
the highest value among two counts on the day indicated in
the heading and the following day

Species                                            Date

                         07/10/2011   22/10/2011   04/11/2011

Gr White-fronted Goose         325         2071            5326
Snow/Ross's Goose                2           78            6426
Tundra Swan                      0            0               1
Mexican Duck                     0            0               0
Mallard                          0            0              75
Green Teal                       0         1113            2057
Gadwall                       1422           20               0
Pintail                          0           30            2179
American Wigeon                  3           63              76
Northern Showier              2328         9227            5994
Unid. dabbling duck              0            0             400
Redhead                          0          933              14
Ring-necked Duck                 0            0               0
Canvasback                       0            0               1
Lesser Scaup                     0            0              15
Ruddy Duck                       0            2              22
Eared Grebe                      0           11               4
Clark's Lire be                  0            7               0
Db-crested Cormorant             0            1               0
American White Pelican          59           70              19
(.rear Blue Heron                5           15              12
Cattle Egret                     0            4               0
White-faced Ibis                11            0               0
American (nor                   92           28              88
Sandhill Crane                   0         4249            4132
Killdeer                         4            0               0
Semipalmatcd Plover              0            5               3
Black-necked Stilt              10            2               0
American Avocet                460          459             372
Solitary Sandpiper               0            4               0
Spotted Sandpiper                0            0               0
Long-billed Curlew             671         1805             829
Generic sandpiper             2916          703             660
Long-billed Dowitcher            0            3              22
Wilson's Phalarope               0            0               0
Laughing Gull                    2            2               0
Ring-billed Gull               182          188             228
Herring Gull                     0            0               0
Unidentified Gull                0            0               0
Caspian Tern                     0            4               0

Total                         8492       21.097          28,955

Species

                         19/11/2011   04/12/2011   15/12/2011

Gr White-fronted Goose        1148         1070         1838
Snow/Ross's Goose           13.640       10.944       12,850
Tundra Swan                      0            0            0
Mexican Duck                   531           37            0
Mallard                          0         10(1          230
Green Teal                     358           55          172
Gadwall                          0            0            0
Pintail                          9          176           24
American Wigeon                  0            0            0
Northern Showier              2785         3051         2437
Unid. dabbling duck            351         1105           45
Redhead                          0            0            2
Ring-necked Duck                 0            0            0
Canvasback                       0           10            0
Lesser Scaup                     0            0            0
Ruddy Duck                      26           74          147
Eared Grebe                      5            2            0
Clark's Lire be                  1            1            2
Db-crested Cormorant             0            0            0
American White Pelican           8           13            0
(.rear Blue Heron               11            5            3
Cattle Egret                     0            0            0
White-faced Ibis                 0           (1            0
American (nor                  265           85            6
Sandhill Crane                6939          938         4790
Killdeer                         0            0            1
Semipalmated Plover              0            0            0
Black-necked Stilt               0            0            0
American Avocet                 32           59           44
Solitary Sandpiper               9            1            1
Spotted Sandpiper                0            0            0
Long-billed Curlew             158           77          477
Generic sandpiper              301          220          233
Long-billed Dowitcher           36          440          403
Wilson's Phalarope               0           (1            0
Laughing Gull                    0           (1            0
Ring-billed Gull               327         1026          272
Herring Gull                    27            0           15
Unidentified Gull                0           10          161
Caspian Tern                     0            0            0

Total                       26,960       19,499       24,153

Species

                         29/12/2011   14/01/2012   29/01/2012

Gr White-fronted Goose        2216         2547            0
Snow/Ross's Goose           22,546       18,776         5192
Tundra Swan                      0            0            0
Mexican Duck                     0            2            0
Mallard                        269          159           18
Green Teal                      16           80            0
Gadwall                          0            0           36
Pintail                          1            1            0
American Wigeon                 23            0            0
Northern Showier              2848         4668         1615
Unid. dabbling duck            196          578          501
Redhead                          0            0            0
Ring-necked Duck                 0            0            0
Canvasback                       0            0            0
Lesser Scaup                     0            0            0
Ruddy Duck                       7           15            1
Eared Grebe                      0            0            0
Clark's Lire be                  3            4            0
Db-crested Cormorant             0            0            0
American White Pelican           0            0            1
(.rear Blue Heron                8           11            7
Cattle Egret                     0            0            0
White-faced Ibis                 0            0            0
American (nor                   30          214            0
Sandhill Crane                3325         2800          212
Killdeer                         1            0            2
Semipalmatcd Plover              0            0            0
Black-necked Stilt               0            0            0
American Avocet                 17           22            0
Solitary Sandpiper               0            0            0
Spotted Sandpiper                0            0            0
Long-billed Curlew             345          615           13
Generic sandpiper              148          382          162
Long-billed Dowitcher           84          100           45
Wilson's Phalarope               0            0            0
Laughing Gull                    0            0            0
Ring-billed Gull               360          160          365
Herring Gull                    10            0            0
Unidentified Gull              814          728          853
Caspian Tern                     0            0            0

Total                       33,267       31,862         9022

Species                  Date

                         11/02/2012 23   1/02/2012   10/03/2012

Gr White-fronted Goose              0           0            0
Snow/Ross's Goose                7504        4950          487
Tundra Swan                         0           0            0
Mexican Duck                        0           0            0
Mallard                             0          71           13
Green Teal                         76         210          421
Gadwall                           107         122           52
Pintail                          2388         260            0
American Wigeon                     0           0            0
Northern Showier                 8718        2986         2236
Unid. dabbling duck                65         373          425
Redhead                             0           0            0
Ring-necked Duck                    0           1            0
Canvasback                          0          11            0
Lesser Scaup                        0           0            0
Ruddy Duck                          0          36           21
Eared Grebe                         0           0            0
Clark's Lire be                     1           0            0
Db-crested Cormorant                0           0            0
American White Pelican             17         200          107
(.rear Blue Heron                   4           4            2
Cattle Egret                        0           0            0
White-faced Ibis                    0           0            0
American (nor                     130           0            0
Sandhill Crane                   4076        7640         2905
Killdeer                            2           6           16
Semipalmated Plover                 0           0            0
Black-necked Stilt                  0           0            0
American Avocet                    28          96           86
Solitary Sandpiper                  0           0            0
Spotted Sandpiper                  47           0            0
Long-billed Curlew                 59         207          101
Generic sandpiper                   0          86          295
Long-billed Dowitcher              80          45           36
Wilson's Phalarope                  2           0            0
Laughing Gull                       0           0            0
Ring-billed Gull                  225          43            0
Herring Gull                        1           0            0
Unidentified Gull                 679        1606          500
Caspian Tern                        0           0            0

Total                          24,209      18,953         7703

Species                                             Total

                         23/03/2012   14/04/2012

Gr White-fronted Goose        2071            0     18,612
Snow/Ross's Goose               78           19    103,492
Tundra Swan                      0            0          1
Mexican Duck                    18            2        590
Mallard                          0            0        935
Green Teal                    1101           25       5684
Gadwall                         20            0       1779
Pintail                         30            0       5098
American Wigeon                 63            0        228
Northern Showier              8466         2313     59,672
Unid. dabbling duck              0          112       4151
Redhead                        933            0       1882
Ring-necked Duck                 0            0          1
Canvasback                       0            0         22
Lesser Scaup                     0            0         15
Ruddy Duck                       2            2        354
Eared Grebe                     11            0         33
Clark's Lire be                  7            0         26
Db-crested Cormorant             1            0          2
American White Pelican          70          265        829
(.rear Blue Heron               16            3        106
Cattle Egret                     4            0          8
White-faced Ibis                 0            0         11
American (nor                   20            0        958
Sandhill Crane                2599            0     44,605
Killdeer                         1            0         33
Semipalmated Plover              5            0         13
Black-necked Stilt               3            0         15
American Avocet                459          747       2881
Solitary Sandpiper               4            0         12
Spotted Sandpiper                0            0         47
Long-billed Curlew            1883            0       7240
Generic sandpiper              767         1140       8013
Long-billed Dowitcher            3           32       1329
Wilson's Phalarope               0            0          2
Laughing Gull                    3            5         12
Ring-billed Gull               188            6       3570
Herring Gull                     0            0         53
Unidentified Gull                0          199       5550
Caspian Tern                     4            0          8

Total                       18,830         4870    277,872

Table 3.--Abundance of waterbirds at 12 counting stations in Laguna
de Bustillos throughout the 2011-2012 winter season. Values given
are the highest value among two counts on consecutive days (see
Table 2)

Species                                 Site

                              Anahuac   Caballos   Campos   Centro
                                                            Calles

Greater White-fronted Goose      328       9580     1980        1
Snow/Ross's Goose               1304     41,316     4794     6726
Tundra Swan                        0          0        0        1
Mexican Duck                      18         57      275      112
Mallard                           13        320        0        0
Green Teal                       818        253       79      936
Gadwall                          273        160        0      102
Pintail                           23       1836        1       14
American Wigeon                   10         68        0        0
Northern Shoveler             10,186       6266     4767     3363
Unidentified dabbling ducks      323        173      533      195
Redhead                            0          0       14        0
Ring-necked Duck                   0          0        0        0
Ganvasback                         8          0        0        2
Lesser Scaup                       0          0        9        0
Ruddy Duck                       108          0        0      180
Eared Grebe                       10          0        0        9
Clark's Grebe                      0          0        0        7
Double-crested Cormorant           0          0        0        0
American White Pelican            18         80        6       99
Great Blue Heron                  10         14        1        3
(Cattle Egret                      0          0        0        0
White-faced Ibis                   0          0        0        0
American Coot                    823        134        0        0
Sandhill Crane                 11,725      4058     6872     2464
Killdeer                           9          0        0        0
Semipaltnated Plover               0         10        0        0
Black-necked Stilt                 1          0        0        0
American Avocet                  236         20               580
Solitary Sandpiper                 6          0        0        0
Spotted Sandpiper                 30          6        0        0
Long-billed Curlew               186        963      128      118
Generic sandpiper                632       1626      296     1067
Long-billed Dowitcher           1210         54        0        0
Wilson's Phalarope                 0          0        0        0
Laughing Gull                      5          0        0        0
Ring-billed Gull                 243        243      185      787
Herring Gull                       0          0        0       21
Unidentified Gull                300        179      989     1608
Caspian Tern                       0          0        0        0

Total                         28,856     67,416    20,937   18,395

Species

                              El Rincon   Favela     La Cal

Greater White-fronted Goose       2077        150         0
Snow/Ross's Goose               24,455       8790         0
Tundra Swan                          0          0         0
Mexican Duck                        21          0         2
Mallard                            145          0        10
Green Teal                         879        309       389
Gadwall                              0        252        92
Pintail                            164         23         0
American Wigeon                     36         16         0
Northern Shoveler                 5787       6089      2012
Unidentified dabbling ducks        982         94       566
Redhead                              0          0         0
Ring-necked Duck                     0          0         1
Ganvasback                           0          0        11
Lesser Scaup                         0          0         0
Ruddy Duck                           0          9        27
Eared Grebe                          3          0         0
Clark's Grebe                        1          0         4
Double-crested Cormorant             0          0         0
American White Pelican             225         81        93
Great Blue Heron                     4          3         5
(Cattle Egret                        0          0         0
White-faced Ibis                     0         11         0
American Coot                        0          0         0
Sandhill Crane                       0     17,983         0
Killdeer                             3          4         1
Semipaltnated Plover                 0          0         3
Black-necked Stilt                   0         10         4
American Avocet                    514        844        37
Solitary Sandpiper                   2          4         0
Spotted Sandpiper                    0          11        0
Long-billed Curlew                1227        418         8
Generic sandpiper                  654        173       194
Long-billed Dowitcher               45         20         0
Wilson's Phalarope                   0          2         0
Laughing Gull                        0          0         0
Ring-billed Gull                   134         84        45
Herring Gull                         0          0         0
Unidentified Gull                  885        120        14
Caspian Tern                         0          0         4

Total                           38,243     35,493      3522

Species

                              La Cruz           La Selva   La Vieja

Greater White-fronted Goose         0                 0       4017
Snow/Ross's Goose                   0                 0     14,288
Tundra Swan                         0                 0          0
Mexican Duck                       12                21          0
Mallard                           299                 6         40
Green Teal                        642               392        205
Gadwall                           520               295          0
Pintail                           430                 0       1969
American Wigeon                    21                 0          0
Northern Shoveler                8756              3261       2602
Unidentified dabbling ducks       475                 6        467
Redhead                             0                 0          2
Ring-necked Duck                    0                 0          0
Ganvasback                          0                 0          0
Lesser Scaup                        0                 0          0
Ruddy Duck                         21                16          0
Eared Grebe                         4                 6          0
Clark's Grebe                      14                 0          0
Double-crested Cormorant            2                 0          0
American White Pelican             34               104         84
Great Blue Heron                   14                16          9
(Cattle Egret                       0                 2          0
White-faced Ibis                    0                 0          0
American Coot                       1                 0          0
Sandhill Crane                      0                 3       1355
Killdeer                            0                 0          2
Semipaltnated Plover                0                 0          0
Black-necked Stilt                  0                 0          0
American Avocet                    61               155        217
Solitary Sandpiper                  0                 0          0
Spotted Sandpiper                   0                 0          0
Long-billed Curlew                  7                18       3966
Generic sandpiper                  85               121       1684
Long-billed Dowitcher               0                 0          0
Wilson's Phalarope                  0                 0          0
Laughing Gull                       0                 0          2
Ring-billed Gull                   76                69        543
Herring Gull                        0                 0          0
Unidentified Gull                   6               325        344
Caspian Tern                        4                 0          0

Total                          11,484              4816     31,796

Species

                              Los        Potreros           Total
                              Taraises

Greater White-fronted Goose         0        479             18,612
Snow/Ross's Goose                   0       1819            103,492
Tundra Swan                         0          0                  1
Mexican Duck                       45         27                590
Mallard                           102          0                935
Green Teal                        165        617               5684
Gadwall                            85          0               1779
Pintail                            16        622               5098
American Wigeon                    65         12                228
Northern Shoveler                2633       3950             59,672
Unidentified dabbling ducks        97        240               4151
Redhead                             0       1866               1882
Ring-necked Duck                    0          0                  1
Ganvasback                          0          1                 22
Lesser Scaup                        0          6                 15
Ruddy Duck                          0          0                354
Eared Grebe                         0          1                 33
Clark's Grebe                       0          0                 26
Double-crested Cormorant            0          0                  2
American White Pelican              3          2                829
Great Blue Heron                   23          4                106
(Cattle Egret                       6          0                  8
White-faced Ibis                    0          0                  11
American Coot                       0          0                958
Sandhill Crane                      0        145             44,605
Killdeer                            0         14                 33
Semipaltnated Plover                0          0                 13
Black-necked Stilt                  0          0                 15
American Avocet                   207          2               2881
Solitary Sandpiper                  0          0                 12
Spotted Sandpiper                   0          0                 47
Long-billed Curlew                 81        120               7240
Generic sandpiper                 270       1211               8013
Long-billed Dowitcher               0          0               1329
Wilson's Phalarope                  0          0                  2
Laughing Gull                       5          0                 12
Ring-billed Gull                  972        189               3570
Herring Gull                       32          0                 53
Unidentified Gull                 355        425               5550
Caspian Tern                        0          0                  8

Total                            5162     11,752            277,872
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Author:Mireles, Cinthia; Mellink, Eric
Publication:The American Midland Naturalist
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Geographic Code:1MEX
Date:Jul 1, 2017
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