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Coastal waterbirds of El Chorro and Majahuas, Jalisco, Mexico, during the non-breeding season, 1995-1996.

RESUMEN

Durante la estacion no reproductiva de 1995-1996 estudiamos las aves acuaticas de los estuarios El Chorro y Majahuas, Jalisco, Mexico. El Chorro es un cuerpo de agua mas abierto, mientras que Majahuas esta formado por eanales rodeados por manglares. Registramos 77 especies de aves. Las aves marinas comprendieron el 66%, los patos y similares el 16%, las aves playeras el 12% y las garzas el 5%. Sterna hirundo y Phalacrocorax brasilianus representaron el 40 y 33%, respectivamente, del total de aves marinas. El que la bocabarra de El Chorro estuviera abierta o cerrada influyo en la concentracion de aves en los dos esteros, debido a la exposicion o inundacion de areas lodosas y arenosas. A pesar de las diferencias entre los dos estuarios, la epoca del ano fue mas importante en la composicion de las comunidades de aves. Ambos esteros deben considerarse como una sola entidad ecologica.

Abstract: We studied how waterbirds used two small estuaries during the non-breeding season of 1995-1996. These estuaries, El Chorro and Majahuas, were located in the middle of a large span of non-wetland habitat along the Pacific coast of Mexico. Whereas El Chorro was basically a large and open waterbody, Majahuas was a long and narrow corridor flanked by mangroves. The two estuaries had 77 species throughout our study, but shared only 58, due to differences in their habitat. Seabirds comprised 66% of all the birds; grebes, ducks and rails 16%; shorebirds 12% and herons and egrets 5%. During late winter and early spring a very reduced number of migratory species accounted for the dominance of seabirds. Sterna hirundo and Phalacrocorax brasilianus accounted for 40 and 33%, respectively, of all the seabirds. Opening or closure of the estuary mouth at El Chorro affected the bird communities at both sites, by exposing or inundating a large mudflat in that estuary. Overall, however, time of the year was more important in the composition of the bird assemblages. Both estuaries should be considered as a single unit.

Key words: Coastal waterbirds, Jalisco, Mexico, seasonality.

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Coastal waterbirds depend on coastal wetlands, either permanent or seasonal, during an important part of the year. Many of these birds are migratory, and during their migration rely on a chain of specific, irreplaceable sites to feed and store energy to fly to their next stop (Myers et al. 1987). The disparity between the extensive breeding areas and the much smaller sites used during migration can result in enormous concentrations of birds in small coastal estuaries (Myers 1983), where they use available food to its maximum (Goss-Custard 1977, Clark et al. 1993). Adequate environmental conditions and feeding resources in these areas are fundamental for the survival of such birds (Senner 1979, Blem 1980, Myers 1983, Morrison 1984, Myers et al. 1987).

Although Mexico has the longest coastline among Latin American countries, valorization of most of its coastal wetlands for migrating or wintering birds has been neglected (Saunders & Saunders 1981, Scott & Carbonell 1986). This is particularly true for small wetlands, which nevertheless might be important sites along a migratory route. Along the Pacific coast of Mexico, between Marismas Nacionales, Nayarit and the center of the state of Guerrero, a span of roughly 1150 Km, there is only one group of large coastal wetlands: Laguna de Cuyutlan and associated wetlands, in state of Colima. The few, small, isolated, wetlands between Laguna de Cuyutlan and that of Marismas Nacionales, may play an important role in the migration of waterbirds, and the objective of this work was to document the use by waterbirds of two such wetlands: El Chorro, and Majahuas, during the non-breeding season. Although nearby Playon de Mismaloya, ah important sea turtle hatching beach, has been under close scrutinity and protection for many years, use by waterbirds of the local wetlands had never been evaluated.

MATERIALS AND METHODS

Study area: El Chorro (132.22 ha) and Majahuas (72.39 ha) are located on the coast of Jalisco, western Mexico (19[grados]52, N, 105[grados]23' W). El Chorro receives fresh water mostly from La Tigra and Cabeza de Otate creeks. Its coastal lagoon is separated from the sea by a 50 m-wide and 2.5 m-high barrier beach, but sea waves, rain, and most often fishermen open it periodically, allowing the wetland to empty into the sea, which causes the exposure of about 40 ha of mudflats. One side of the estuary has 7 m-high sand dunes with patches of thornscrub and low deciduous tropical forest. The area closest to the sea is vegetated with Pectis arenaria, Okenia hypogaea, Tephrosia leiocarpa var. costenya, Chamaecrista chamaecristoides, Zinnia maritima, Ipomea pes-caprae and Jouvea pilosa. The upper reaches of the sand dunes and sandy canadas are covered with xerophitic scrub, which includes Opuntia excelsa, Acacia spp. and Heliocereus spp. The waterbody is surrounded mostly by Conocarpus erectus and, to a lesser degree, Laguncularia racemosa, Hibiscus pernambucensis, Cenchrus brownii, Jouvea straminea, and other grasses.

Majahuas is 7 km SE of El Chorro. To the sides of the estuary, there are long channels along the coast separated from the sea by a 2.5 m-high barrier beach, that is about 80 m-wide near the mouth of the estuary. Fresh water comes mostly from Tomatlan river, and the estuary is connected to the sea during most of the year. Majahuas is dominated by mangroves (63.03 ha). The channels SE of the main waterbody are dominated by H. pernambucensis, along with Sarcostemma clausum, and aquatic low-salinity vegetation, such as Eichhornia crassipes, Crinum erubecens and Phragmites australis, in addition to coconut palms. Along the NE channels L. racemosa, with small patches of H. pernambucensis, are the dominant vegetation, whereas Ipomea pes-caprea is the main plant on sand dunes. Some areas near the estuaries have been cleared for production of banana, watermelon, mango, lime, chile, com, papaya, rice, and coconuts, or for the establishment of pasturelands.

Methods: Between 1 September 1995 and 25 April 1996, we visited both estuaries every 15 days. From each of five observation points (per estuary) we identified and counted all the birds in sight, with the help of 10x binoculars and a spotting telescope (60x). On each sampling date we did one count when the tide began to ebb and one when it started to rise. Each census took about three hours. The channels in Majahuas were surveyed from an fiberglass skiff with a out-of-board motor. The visits were arranged in six periods: late summer (3-15 Sep. 1995), early and late autumn (1 0ct.-3 Nov., and 17 Nov.-18 Dec., 1995, respectivity), early and late winter (5 Jan.-3 Feb., and 18 Feb.-18 Mar., 1996, respectively), and early spring (8-25 Apr. 1996). For each species, we considered the highest tally within a period as its best estimator. The two estuaries were compared in terms of their species richness and bird abundance with chi-2 test.

RESULTS

Wetland characteristics: Two relevent differences occured between the two sites. El Chorro was basically a large and open water-body, Majahuas a long and narrow corridor flanked by mangroves. Whereas the estuary mouth of Majahuas was kept mostly open by river discharge (except on 3 January and 16 February when it was closed), El Chorro's mouth alternated between open and close (Open on 1 Sep., 16 Oct., 1 Nov., 15 Nov., 16 Jan., 16 Feb., 2 Mar., 8 Apr., and 24 Apr. Closed on 15 Sep., 1 Oct., 17 Dec., 3 Jan., 2 Feb., and 17 Mar). At El Chorro, during the first half of the study water flow was not sufficient to fill the coastal lagoon, even when the mouth was closed, allowing for the exposure of a large mudflat that was protected by mangrove communities and sand dunes.

Species: Using the high values of each period we tallied 48 848 birds of 77 species (Table 1, Appendixes 1 and 2). Both sites were clearly dominated by seabirds, with grebes, ducks and rails, and shorebirds following with modest numbers (Table 1). Herons and egrets exhibited low numbers and "other waterbirds" where almost non-present. As a reflection of the differences in their characteristics, both estuaries shared only 58 species, and they were significantly different with respect to each other in the number of species of grebes, ducks and rails, and that of shorebirds (Table 1, [X.sup.2], a<0.05, in both cases), and in the number of individuals in all groups (a<0.01), except "other waterbirds", which were not analized.

The much greater abundance of seabirds was restricted to late winter and later. Moreover, the total numbers of seabirds were due to two species: Sterna hirundo, which accounted for 40% of all seabirds (of which 81% were tallied in a single period), and Phalacrocorax brasilianus, with 33% of the individuals. Of the 20 species of seabirds we never recorded more than 12 in any single period.

Sterna hirundo is a common species along the Mexican Pacific during rail and winter (Schaldach 1963, Binford 1989, Howell & Webb 1995). We found it feeding at sea and resting on sandy areas on the barrier beach. Although there were almost twice as many Sterna hirundo in Majahuas as in El Chorro, the proportion of this species among the seabirds was similar at both localities (41 and 38%, respectively). Phalacrocorax brasilianus is a widesprad resident of the region (Howell & Webb 1995). It fed within the coastal lagoons, and rested on sandy areas. It was proportionately more abundant at El Chorro where it accounted for 46% of all seabirds present (vs. 25% in Majahuas). Among the other common seabirds, the gulls preferred Majahuas, where they used the sandy areas.

Seabirds exhibited a strong seasonal variation, and they gradually increased from less than 1% of the total birds tallied in late summer, to 46% in early spring. To a large degree this reflects the increase of Sterna hirundo during this last period. It is also notable that the Phalacrocorax brasilianus, despite being a local resident, was most abundant during late winter. Larus heermanni had their largest numbers in early spring, but the other seabird species had their maximum numbers in late winter.

Throughout the study we observed 14 species of grebes, ducks and rails. In late summer we recorded only Dendrocygna autumnalis, a regional resident, and migratory species began to arrive in the fall until ten species were found in early winter. After that, species began to dissapear, and in early spring there were only seven. Number of individuals followed a similar pattern. Two species accounted for the majority of birds in this: Anas americana (34% of all grebes, ducks and rails) and Fulica americana (30%). Both are common in the area outside the breeding season, and both preferred the waterbody.

We identified 15 species of herons and egrets throughout the study, and there were from nine to 13 species in each individual period. Egretta thula accounted for 64% of all herons and egrets. This species preferred mangrove associations and mudflats to rest, and shallow waters to feed. It was common throughout the study, but there was a clear reduction in numbers in late summer. This suggests that the areas are used by a number of wintering birds, but that there might also be a local breeding population. Bubulcus ibis had a clear concentration in late fall. At other locations along the coast of southern Mexico, this species also exhibits high numbers in the fall, and later move to cattle pastures to forage (Mellink et al. 1998). Different species of herons and egrets had differences in the timing of the highest tallies: Ardea herodias and Egretta caerulea had their greatest abundance during early fall; Plegadis chihi and Bubulcus ibis in late fall; Nyctanassa violacea in early winter; Ardea alba in late winter; and the other species in early spring. Egretta tricolor was equally abundant the last two study periods. Some of these data should be taken with care, because of the low numbers involved.

We tallied 6 178 shorebirds of 22 species throughout the study. However, two species accounted for almost half of all individuals: Calidris alba (24%) and Himantopus mexicanus (21%), with two other species having moderate numbers: Catoptrophorus semipalmatus and Recurvirostra americana (12% each). Calidris alba preferred the sandy habitats, such as the outside beaches of the barrier beach, and sand flats at the mouth of the estuary, while Himantopus mexicanus, Catoptrophorus semipalmatus, and R. americana fed in shallow waters, mudflats, and sandflats.

Abundance of shorebirds was bimodal, with peaks in early fall and late winter, reflecting the general migration pattern of shorebirds. However, not all species of shorebirds exhibited both peaks. Those that did were the Calidris mauri, Charadrius alexandrinus, C. alba, Catoptrophorus semipalmatus, H. mexicanus, and Pluvialis squatarola. The peaks of C. mauri abundance were in late summer and early winter, those of C. alexandrinus in late summer and late winter. The other species with two peaks had one in early fall and one in late winter. Actitis macularia, Charadrius semipalmatus, Charadrius wilsonia, and Gallinago gallinago had only one peak, in in early fall. Calidris minutilla and Tringa melanoleuca, one peak in late fall; Numenius americanus, Numenius phaeopus, and R. americana one peak in early winter; and Calidris mauri and Haematopus palliatus one peak in late winter. The remaining species exhibited no clear peak in their abundance.

We recoded six additional waterbirds during the study (Appendixes land 2). However, their numbers were to low to merit discussion.

DISCUSSION

The two estuaries summed 77 species throughout our study, 48% of all the waterbird species potentially present in the area (Howell & Webb 1995). The avifauna at both estuaries were dominated by seabirds, especially by a very reduced number of migratory species during late winter and early spring. The two estuaries had a similar variation in the number of species of seabirds. However, the differences in habitat caused Pelecanus erythrorhynchos, Sula nebouxii and a single Mycteria americana to use El Chorro, only. Majahuas had a more abrupt and later increase in its richness of grebes, ducks and rails, and less variation in shorebirds than El Chorro (Table 1). Overall, during the first four periods El Chorro had a similar, or larger, number of birds than Majahuas, but during the last two periods Majahuas greatly outnumbered it, except for the shorebirds. The seabird species that were shared by both sites either preferred Majahuas or had similar numbers in both places, except the P. brasilianus, which was slightly more abundant at El Chorro. This later preference was due to the conjunction of mangrove with open relatively deep, waters. The preference of most larids for Majahuas was a function of its very shallow waters in which they could stand. A similar preference has been found in wetlands of the Costa Chica of Oaxaca (Mellink et al. 1998).

The late winter change in preference by A. americana appears to have been the result of the exposure of the mudflat at El Chorro. The D. autumnalis change from Majahuas to El Chorro in early spring might reflect its wandering behavior (Howell & Webb 1995).

Only two species of herons and egrets clearly preferred one of the sites. The preference of the B. ibis for El Chorro and its near-abscence from Majahuas is puzzling as this is a very common occupant of other well vegetated tropical wetlands (Mellink et al. 1998). Although the E. thula preferred Majahuas, this preference developed only after the water level of El Chorro rised inundating habitat it had been using.

The preference of mid-sized and large shorebirds, except H. mexicanus (and, in this species because of one event of high abundance), and several small shorebirds (A. macularia, Arenaria interpres, C. minutilla, Charadrius semipalmatus, C. wilsonia and, and P squatarola) for El Chorro, appeared to be a response to its larger mudflats. The preference of C. alba, C. mauri, and C. alexandrinus for Majahuas was due to its sandier habitat.

Despite the differences between both estuaries, the migratory birds that used them produced a seasonal pattern, more than a locality pattern. The importance of resident species, which have more defined habitat preferences, was swamped by the numbers of the migratory birds. The high dynamism of the avifauna of the two estuaries was a function of the migration of the species that used them, but also of the status of the mouth of one estuary, which caused changes in the availability of certain habitats inside the estuary and according movements of birds between estuaries. So, rather than two different estuaries, they should be considered, and managed, as a single, coherent unit.
TABLE 1

Number of species (first value in each cell) and individuals (second
value) of estuarine birds during the non-breeding season at estuaries
Majahuas and El Chorro, Jalisco, Mexico. 1995-1996

                           Late      Early       Late
                           Summer    Fall        Fall

                                   Majahuas

Seabirds                   4/75      5/227       6/106
Grebes, ducks and rails    0/0       0/0         1/77
Herons and egrets          7/69      11/69       8/75
Shorebirds                 11/395    13/479      12/370
Other                      0/0       2/7         2/3
TOTAL                      22/539    31/782      29/631

                                   El Chorro

Seabirds                   8/226     7/344       4/1 221
Grebes, ducks and rails    1/8       5/384       6/1 606
Herons and egrets          7/33      8/320       10/245
Shorebirds                 10/126    17/652      17/604
Other                      0/0       1/4         1/2
TOTAL                      26/393    38/1 704    38/3 678

                           Early       Late         Early
                           Winter      Winter       spring

                                       Majahuas

Seabirds                   9/1 903     11/8 223     12/8 692
Grebes, ducks and rails    7/1 520     9/2 252      6/172
Herons and egrets          12/150      10/253       11/580
Shorebirds                 17/414      17/891       13/158
Other                      4/11        6/23         4/6
TOTAL                      49/398      53/11 642    46/9 605

                                       El Chorro

Seabirds                   11/1 580    12/3 613     10/5 967
Grebes, ducks and rails    9/1 241     5/231        3/178
Herons and egrets          9/139       7/328        8/98
Shorebirds                 20/936      19/841       8/312
Other                      2/2         3/4          2/6
TOTAL                      51/3 898    46/5 017     31/6 561

APPENDIX 1

Estuarine birds of Majahuas, Jalisco, Mexico, during the non-breeding
season, 1995-1996

                               L-sum    E-fall    L-fall

Seabirds
Puffinusgriseus                  0        0         0
Pelecanus erythrorhynchos        0        0         0
Pelecanus occidentalis          36       26        30
Phalacrocorax brasilianus       10      161        59
Phalacrocorax auritus           10       34         0
Fregata magnificens              0        0         1
Larus atricilla                  0        0         0
Larus pipixcan                   0        0         0
Larus heermanni                  0        0         1
Larus argentatus                 0        4         0
Sterna caspia                    0        2         7
Sterna elegans                   0        0         0
Sterna hirundo                   0        0         0
Sterna forsteri                 19        0         8
Sterna antillarum                0        0         0
Chlidonias niger                 0        0         0
Rynchops niger                   0        0         0

Grebes, Ducks and Rails
Podylimbus podiceps              0        0         0
Podiceps nigricollis             0        0         0
Dendrocygna autumnalis           0        0         0
Aix sponsa                       0        0         0
Anas americana                   0        0         0
Anas discors                     0        0         0
Anas cyanoptera                  0        0         0
Anas clypeata                    0        0         0
Anas acuta                       0        0         0
Aythya affinis                   0        0         0
Porphyrula martinica             0        0         0
Gallinula chloropus              0        0         0
Fulica americana                 0        0        77

Herons and Egrets
Tigrisoma mexicanum              0        2         0
Ardea herodias                   0        5         5
Ardea alba                       0        6         1
Egretta thula                   45       26        55
Egretta caerulea                 2        5         7
Egretta tricolor                 1        2         3
Egretta rufescens                0        0         0
Bubulcus ibis                    0        6         0
Butorides virescens              0        0         0
Nycticorax nycticorax            1        2         2
Nyctanassa violacea              6       12         1
Eudocimus albus                  2        2         0
Plegadis chihi                   0        0         1
Ajaia ajaja                     12        1         0

Shorebirds
Pluvialis squatarola             0        0         1
Charadrius alexandrinus         56       20         2
Charadrius wilsonia             18        1         9
Charadrius semipalmatus          0       28         9
Charadrius melodus               0        0         0
Haematopus palliatus             0        0         0
Himantopus mexicanus            27       98        42
Recurvirostra americana          3        0         0
Tringa melanoleuca              34       12        57
Tringa flavipes                  0       11         0
Catoptrophorus semipalmatus     40       61        25
Actitis macularia                0        6         2
Numenius phaeopus                3        4         3
Numenius americanus              2        6         2
Limosa fedoa                     0        0         0
Arenaria interpres               2        7         0
Calidris alba                  180      220       168
Calidris mauri                  30        5        50
Calidris minutilla               0        0         0

Other
Anhinga anhinga                  0        1         1
Jacana spinosa                   0        6         0
Pandion haliaetus                0        0         0
Ceryle torquata                  0        0         0
Ceryle alcyon                    0        0         2
Chloroceryle americana           0        0         0

                               E-win    L-win     E-spr

Seabirds
Puffinusgriseus                   0        3         0
Pelecanus erythrorhynchos         0        4         0
Pelecanus occidentalis          152       53       147
Phalacrocorax brasilianus      1490     2449       575
Phalacrocorax auritus             0        0         0
Fregata magnificens               7        7         3
Larus atricilla                 175      967       146
Larus pipixcan                   22     2255        60
Larus heermanni                   1       20       660
Larus argentatus                  0        0         0
Sterna caspia                    19       95        60
Sterna elegans                    0        0       150
Sterna hirundo                    0     2050      5846
Sterna forsteri                  34        0         0
Sterna antillarum                 0        0        18
Chlidonias niger                  0        0       917
Rynchops niger                    3      320       110

Grebes, Ducks and Rails
Podylimbus podiceps               1        0         1
Podiceps nigricollis              0       15         0
Dendrocygna autumnalis          360        1        15
Aix sponsa                        0        4         0
Anas americana                  389      850        44
Anas discors                     60       10        28
Anas cyanoptera                   0       60         0
Anas clypeata                    35       40         0
Anas acuta                       45        0         0
Aythya affinis                    0      130         0
Porphyrula martinica              0        0         2
Gallinula chloropus               0        0         3
Fulica americana                630     1134        79

Herons and Egrets
Tigrisoma mexicanum               1        6         2
Ardea herodias                    4        4         4
Ardea alba                        4       14         6
Egretta thula                    74      195       478
Egretta caerulea                  1        5         4
Egretta tricolor                  4        4        11
Egretta rufescens                 0        0         4
Bubulcus ibis                     0        0         0
Butorides virescens               3        6        11
Nycticorax nycticorax             1        0         0
Nyctanassa violacea              43       12        13
Eudocimus albus                   8        5        36
Plegadis chihi                    1        0         0
Ajaia ajaja                       6        2        11

Shorebirds
Pluvialis squatarola              2        1         0
Charadrius alexandrinus          10       37         0
Charadrius wilsonia               6       12         1
Charadrius semipalmatus          21       17        10
Charadrius melodus                0        4         0
Haematopus palliatus              2        2         0
Himantopus mexicanus            135      453        48
Recurvirostra americana          32        3         4
Tringa melanoleuca               12        3         5
Tringa flavipes                   7        0         0
Catoptrophorus semipalmatus      64       30        49
Actitis macularia                 4        2         2
Numenius phaeopus                 2        5         3
Numenius americanus               8        5         4
Limosa fedoa                      0        0         4
Arenaria interpres                2        0         0
Calidris alba                    80      290        18
Calidris mauri                   20       22         7
Calidris minutilla                7        5         0

Other
Anhinga anhinga                   0        1         1
Jacana spinosa                    3        6         2
Pandion haliaetus                 2        1         1
Ceryle torquata                   2        1         0
Ceryle alcyon                     4       12         2
Chloroceryle americana            0        2         0

L=Late, E=early: sum=summer, win=winter, spr=spring.

APPENDIX 2

Estuarine birds of El Chorro, Jalisco, Mexico, during the non-breeding
season, 1995-1996.

                             L-sum    E-fall    L-fall

Seabirds
Sula nebouxii                  4        0          0
Pelecanus erythrorhynchos      0        0          0
Pelecanus occidentalis        45        5         32
Phalacrocorax brasilianus     13      230      1 120
Phalacrocorax auritus          0        1          0
Fregata magnificens            4        3          0
Larus atricilla                1        0          0
Larus pipixcan                 0        0          0
Larus heermanni                0        0          0
Larus californicus             0        1          0
Sterna caspia                  0       10          8
Sterna elegans                15        0          0
Sterna hirundo                 0        0          0
Sterna forsteri                0       94         61
Sterna antillarum            140        0          0
Chlidonias niger               0        0          0
Rynchops niger                 4        0          0
Mergus serrator                0        0          0

Grebes, Ducks and Rails
Dendrocygna autumnalis         8        4          0
Anas americana                 0       56        900
Anas discors                   0      189         56
Anas cyanoptera                0        0          0
Anas clypeata                  0        1         29
Anas acuta                     0        0         95
Anas crecca                    0        0        383
Aythya affinis                 0        0          0
Fulica americana               0      134        143

Herons and Egrets
Ardea herodias                 2       12          5
Ardea alba                     2        4         10
Egretta thula                 10      253         43
Egretta caerulea               3       32          5
Egretta tricolor               3        2          7
Egretta rufescens              0        0          0
Bubulcus ibis                  0        8        135
Nyctanassa violacea            4        7         16
Eudocimus albus                0        2          4
Plegodis chihi                 0        0         13
Ajaia ajaja                    9        0          0
Mycteria americana             0        0          7

Shorebirds
Pluvialis squatarola           3       28          3
Charadrius alexandrinus        0        4          8
Charadrius wilsonia            5       68          9
Charadrius semipalmatus       18       38         53
Charadrius vociferus           0        0          0
Charadrius melodus             0        0          0
Charadrius sp.                 5        0          0
Haematopus palliatus           0        0          0
Haematopus mexicanus           0       74        130
Recurvirostra americana        6       20         63
Tringa melanoleuca            11       39         27
Tringa flavipes                0        0          3
Catoptrophorus semipalmatus   16      144         44
Actitis macularia              0       36          4
Numenius phaeopus             46       35         87
Numenius americanus            3        8         19
Limosa fedoa                  13        1          4
Arenaria interpres             0        6         10
Calidris alba                  0      129         90
Calidris mauri                 0        6          0
Calidris minutilla             0        1         45
Gallinago gallinago            0       15          6

Other
Anhinga anhinga                0        4          0
Pandion haliaetus              0        0          0
Ceryle torquata                0        0          0
Ceryle alcyon                  0        0          2

                             E-win    L-win     E-spr

Seabirds
Sula nebouxii                   0        0         0
Pelecanus erythrorhynchos      13       15         0
Pelecanus occidentalis         72       41       440
Phalacrocorax brasilianus   1 200    2 643       758
Phalacrocorax auritus           0        0         0
Fregata magnificens             3       10         8
Larus atricilla               147       83        44
Larus pipixcan                 24      370         3
Larus heermanni                 0       11        68
Larus californicus              0        0         0
Sterna caspia                  38       20        46
Sterna elegans                  0       10         0
Sterna hirundo                 18      400     4 480
Sterna forsteri                28        4         0
Sterna antillarum               0        0         0
Chlidonias niger                0        0        60
Rynchops niger                 35        6        60
Mergus serrator                 2        0         0

Grebes, Ducks and Rails
Dendrocygna autumnalis          4        0       150
Anas americana                308       97         0
Anas discors                   70       40        10
Anas cyanoptera                15       15         0
Anas clypeata                  35       18        18
Anas acuta                     60        0         0
Anas crecca                   660        0         0
Aythya affinis                 28        0         0
Fulica americana               61       61         0

Herons and Egrets
Ardea herodias                  3        3         3
Ardea alba                      3       26         5
Egretta thula                  28      263        71
Egretta caerulea                3        2         2
Egretta tricolor                2       13         6
Egretta rufescens               0        0         2
Bubulcus ibis                  73        0         0
Nyctanassa violacea             3        7         5
Eudocimus albus                23       14         4
Plegodis chihi                  0        0         0
Ajaia ajaja                     1        0         0
Mycteria americana              0        0         0

Shorebirds
Pluvialis squatarola           16       82         0
Charadrius alexandrinus         6        5         0
Charadrius wilsonia             1        0         0
Charadrius semipalmatus         1        7         0
Charadrius vociferus            1        0         0
Charadrius melodus              1        0         0
Charadrius sp.                  0        0         0
Haematopus palliatus            4       10         6
Haematopus mexicanus          134      149        28
Recurvirostra americana       250      161       179
Tringa melanoleuca             59       36        18
Tringa flavipes                 1        6         0
Catoptrophorus semipalmatus    72      153        64
Actitis macularia               3        1         1
Numenius phaeopus              99       42         1
Numenius americanus            31       11         0
Limosa fedoa                    0        5         0
Arenaria interpres              6       12         0
Calidris alba                 185      125        15
Calidris mauri                 59       24         0
Calidris minutilla              2        8         0
Gallinago gallinago             5        4         0

Other
Anhinga anhinga                 0        0         0
Pandion haliaetus               1        1         5
Ceryle torquata                 0        1         0
Ceryle alcyon                   1        2         1

L=Late, E=early: sum=summer, win=winter, spr=spring.


ACKNOWLEDGEMENTS

We acknowledge support or assistance from Manoment Birds Observatory, Francisco de A. Silva and E. Santana-Castellon, the Cooperativa "Roca Negra" in Valle de Majahuas. Horacio de la Cueva, C. Valadez Gonzalez, and Julian Monge-Najera provided important comments and criticisms.

REFERENCES

Binford, L.C. 1989. A distributional survey of the birds of the Mexican state of Oaxaca. Ornithol. Monog. 43: 1-412.

Blem, C. R. 1980. The energetics of migration, p.175-224 In Gauthreaux (ed.), Animal migration, orientation, and navigation. Academic, New York.

Clark, K.E., L.J. Niles & J. Burger. 1993. Abundance and distribution of migrant shorebirds in Delaware Bay. Condor 95: 604-705.

Goss-Custard, J.D. 1977. The ecology of the Wash. III. Density related behaviour and the possible effects of a loss of feeding grounds on wading birds (Charadrii). J. Appl. Ecol. 14: 721-739.

Howell, S.N.G. & S. Webb. 1995. A guide to the birds of Mexico and northern Central America. Oxford University. New York. 851 pp.

Mellink, E., J. Luevano & I. Zuria. 1998. Nota sobre los pelecaniformes, ciconiiformes, gallitos marinos (Steminae) y rayadoras (Rynchopinae) de la Costa Chica de Oaxaca, Mexico. Ciencias Marinas. 24: 367-388.

Morrison, R.I.G. 1984. Migration systems of some New World shorebirds, Behav. Mar. Anim. 6: 125-202.

Myers, J.P. 1983. Conservation of migrating shorebirds: Staging areas, geographic bottlenecks, and regional movements. Amer. Birds 37: 23-25.

Myers, J.P., R.I.G. Morrison, P.Z. Antas, B.A. Harrington, T.E. Lovejoy, M. Sallaberry, S.E. Senner & A. Tarak. 1987. Conservation strategy for migratory species. Amer. Scient. 75: 18-26.

Saunders, G.B. & D.Ch. Saunders. 1981. Waterfowl and their wintering grounds in Mexico 1937-64. Fish and Wildlife Service Resource Publication 138. Washington, D.C. 151 pp.

Schaldach, W.J., Jr. 1963. The avifauna of Colima and adjacent Jalisco, Mexico. Proc. W. Found. Verteb. Zool. 1: 1-100.

Scott, D.A. & M. Carbonell. 1986. A Directory of neotropical wetlands. International Union for Conservation of Nature and Natural Resources and International Waterfowl Research Bureau. Cambridge, U.K.

Senner, S.E. 1979. An evaluation on the Copper River delta as critical habitat for migrating shorebirds, en EA. Pitelka (ed.). Stud. Avian Biol. 2: 131-146.

Salvador Hernandez-Vazquez (1) and Eric Mellink (2)

(1) Centro de Ecologia Costera, Universidad de Guadalajara. Gomez Farias No.82. 48980 San Patricio Melaque, Municipio de Cihuatlan, Jalisco, Mexico. Fax: 52 (335) 56331. sahernan@costera.melaque.udg.mx.

(2) Centro de Investigacion Cientifica y de Educacion Superior de Ensenada. Apdo. Postal 2732. Ensenada, Baja California, Mexico. emellink@eicese.mx

Received 19-1-2000. Corrected 3-VIII-2000. Accepted 19-IX-2000.
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Publication:Revista de Biologia Tropical
Date:Mar 1, 2001
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