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Mesoamericana 13 (1) Agosto de 2009 Table 1. Waterfowl species consuming Ruppia maritima drupelets reported in wetlands of the northern cays of Ciego de Avila. Abundance: A (abundant), NC (non-common), C (common), R (rare). Permanence: WR (winter resident), PR (permanent resident), T (transient), BR (bimodal resident). Locality: CC (Cayo Coco), CG (Cayo Guillermo), CPG (Cayo Paredón Grande), BP (bahía de Los Perros). Habitat: LE (tideland and lagoons), 1 ZC (coastal zone). wintering grounds (Table 1). Other bird families such as Rallidae, Scolopacidae and diving ducks (Aythya sp.) were ruled out. DISCUSSION Scientific name Abundance and permanence status Recording the occurrence of R. maritima in Laguna Larga in 2001 entails taking into consideration the current described distribution of this macrophyte in Cuba. According to Urquiola and Cabrera (2000), the nearest population is located in Cayo Guajaba (about 120 km away), but most localities have also been recorded in the western provinces such as Pinar del Río (Playa La Salina), Dietary importance Ciego de Ávila Northern Cays CC CG CPG BP Habitat LE ZC Order Anseriformes Family Anatidae Anas discors A, WR High * * * * * Anas acuta NC, WR-T High * * Anas bahamensis NC, PR High * * * Anas strepera V High * * * * Anas americana C, WR High * * * Anas clypeata C, WR High * * * Aythya affinis NC, WR-T Moderate * * Aythya collaris NC, WR-T Moderate * * Lophodytes cucullatus V Moderate * * * Oxyura jamaicensis NC, BR-T Moderate * * Order Gruiformes Family Rallidae Rallus longirostris C, PR Low * * * * * Porphyrio martinica C, BR Low * * * Gallinula chloropus A, BR Low * * * * Fulica americana A, BR Moderate * * * * Order Chraradiiformes Family Recurvirostridae Himantopus mexicanus A, BR-T Low * * * * * * Family Scolopacidae Tringa melanoleuca C, WR-T Low * * * * * Tringa flavipes C, WR-T Low * * * * * Tringa solitaria NC, WR Low * * * * Tringa semipalmata C, WR-T Low * * * * * * Calidris canutus R, T-WR Low * * * Limnodromus griseus C, WR-T Low * * * * * * Gallinago gallinago C, WR Low * * * * 1 (sandy shores and coastal shallow waters). 31 Habana (Batabanó), Ciudad Habana (Playa de Marianao), and in the eastern region in Granma (Manzanillo). Known dispersal means of this angiosperm are water, fish and birds (Kantrud, 1991) and in this regard, the discontinuity of the coast line in the study area (arrays of cays) and the predominant wave patterns, especially during fall, do not significantly favour effective movements of drupelets from one site to another in a consistent manner. On the other hand, fish-mediated dispersion is ruled out as few fish species feed on this aquatic plant and its detritus (Austin and Austin, 1971; Congdon and
Mesoamericana 13 (1) Agosto de 2009 McComb, 1981) and wigeongrass is more frequently used as nursery areas (Congdon and McComb, 1981). With regards this issue, Darnell (1958) found out that just one species consumes significant amount of this plant in Luoisiana state; and Carr and Adams (1973) found low rates of consumption among 10 foraging groups of fish in Florida, out of three just developed an herbivory stage. In our study area, there are just two species of genera Opsanus and Archosargus, but considered as local residents (F. P. Amargós, pers. comm.), just migrating towards coral reefs during breeding seasons. In the particular case of bird-mediated endozoochory, the broad spatial overlap between the angiosperm geographic distribution in Northamerica and the Atlantic Coast Migratory Route must be taken into account. Such a fact could have favoured the accessibility of this important food resource to various waterfowl species for refuelling in critical stopovers during fall migrations movements. In fact, there is a trend for migratory ducks in the northern hemisphere to feed more on seeds with high carbohydrate levels during fall and winter (Baldassarre and Bolen, 1994). Endozoochory experienced by these ducks is based on the fact that this group of birds is widely recognized as important dispersers of various aquatic organisms due to their abundance, wide distribution ranges and long-distance migrations along the wetlands of the world. Besides, the importance of the R. maritima drupelets in dabbling ducks diet has been broadly pointed out by an extensive literature compiled for over 70 yr (McAtee, 1915; Mabbott, 1920; Campbell, 1946; Smith, 1951; Chamberlain, 1959; Stewart, 1962; Tamisier, 1971; Johnsgard, 1975; Krapu and Swanson, 1978; Prevost et al., 1978; Saunders and Saunders, 1981; Swiderek, 1982; Euliss, 1989). Once the plausibility of waterfowl feeding on the R. maritima seeds while migrating southward is considered, another key phase involved in a possible internal transport is the retention time of drupelets in the gut. Such a factor determines the distance range these seeds can travel (Proctor, 1968). Therefore, the farthermost distance the seeds can be transported will be limited by their duration in the gut and how far the disperser can fly during this time. For instance, if the flight speed of Anas sp. ranges between 60 to 78 km/h (Welham, 1994), and the pattern of retrieved seeds from the disperser indicates that dispersion will take place some hours after ingestion, then endozoochory could be a feasible event between southern regions of the U.S.A. and Cayo Coco during fall 32 migrations. Such a statement is supported by the fact that the highest probabilities of dispersion can occur about 4 h after ingestion, comprising distances ranging from 80 to 320 km, even though periods of time exceeding 8 h could be also attainable (Charalambidou et al., 2003), but at lower probabilities. In addition, the proportion of seeds capable of germination once excreted must be also considered as key factor involved in the occurrence of any dispersion event. Despite the fact the proportion of seeds successfully germinating after being released by any given duck is low, ranging from 0.4 to 1.3% (Charalambidou et al., 2003), in wetlands where hundreds and thousands of individuals are passing through during fall migration, coinciding with the peak of consumption of R. maritma seeds (Cramp and Simmons, 1977), the overall figures become significantly higher. Besides, as the number of individuals carrying the propagule increases, the probability of one of them dispersing the seeds over a long distance to a suitable habitat will be favoured, according to Green et al. (2002). According to the criteria of abundance and permanence during winter season in the salty and brackish wetlands of Cayo Coco, the species Anas discors, A. americana and A. clypeata, are thought to be possible dispersers in the study site. On the contrary, species such as A. strepera (Gadwall), A. bahamensis (White-cheeked Teal), A. acuta (Northern Pintail), Aythya affinis (Lesser Scaup) and A. collaris (Ring-necked Duck) considered as rare and vagrants, are represented by only small populations in this insular territory. Particularly, A. clypeata should be an interesting candidate based on the fact this species showed the highest probability of germinating seeds per digested seeds recorded in SE Spain (Figuerola et al., 2002, 2003), and because of its lamellar density, particularly high among the northern hemisphere ducks (Nudds et al., 1994). In this regard, the range sizes of Ruppia drupelets (0.5-4 mm) can be easily ingested as the high lamellar densities enable ducks to filter smaller particles (Crome, 1985) by reducing the costs of filtering small items, leading to negative correlations between lamellar densities and seed size (Nummi, 1993; Tamisier and Dehorter, 1999). Other species presented in the study area, have also been reported as possible dispersers of R. maritima, such as shorebirds (Scolopacidae) (Sperry, 1940; Bourn and Cottam, 1950; Martin et al., 1951), and gallinules (Rallidae) (Quay and Critcher, 1962; Gaevskaya, 1966). Nonetheless, more updated researches approaching the feeding ecology of Himantopus mexicanus (Black-necked Stilt) (Hamilton,
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