A 10-m-long core was recovered from the coastal flood plain on the eastern margin of the Gulf of California (Bahia Kino, Sonora). Sediments were analysed for loss-on-ignition, magnetic susceptibility, pollen, diatoms, ostracodes and foraminifera. Three levels were dated by 14C. The combined data suggest that the site was flooded during the middle Holocene as sea level increased. At about 6600 yr BP the area was a freshwater to brackish marsh dominated by Typha domingensis and Cyperaceae. Freshwater to brackish conditions suggest the presence of a local source of freshwater during this time and therefore a climate wetter than present. Continued rise in sea level was associated with an increase in depth and salinity. By c. 6350-6250 yr BP, the coring site was an inner lagoon, by c. 6125 yr BP a central lagoon and by c. 5900 yr BP the site was close to the mouth of the lagoon (lower lagoon). Lower lagoon conditions persistel until the top of the record, showing sea-level stabilization; which was followed by the formation of the dune ridge that presently separates the coring site from the sea.

regiones con selvas bajas en México. El trabajo se realizó entre junio de 2005 y octubre de 2006, registrando 113 especies pertenecientes a 13 órdenes y 34 familias; 6 especies son muy abundantes, 10 abundantes, 20 comunes, 32 poco comunes y 37 raras; 79 de las especies registradas fueron residentes, 28 visitantes invernales, 2 visitantes de verano, 3 transitorias y 5 residentes con movimientos estacionales; 15 especies son endémicas a México y 23 están dentro de alguna categoría de riesgo. La avifauna estudiada representa una mezcla de especies características de la cuenca del Balsas, las vertientes pacífi ca y atlántica y los ambientes montanos y áridos del centro de México. Por su composición específi ca la avifauna estudiada se relacionó con las avifaunas de la cuenca del Balsas. La selva baja del cañón del Sabino es prioritaria para la conservación debido a su riqueza en especies endémicas y a la presencia una colonia reproductora de la guacamaya verde, Ara militaris, especie globalmente amenazada. Palabras clave: avifauna, cañada del río Sabino,

A list of the marine invertebrate species identified until now from the rocky intertidal shore at Montepío, Veracruz, is presented. The information was obtained from 10 years of collections made by the Colección Nacional de Crustáceos and additional records were compiled from published information. The species list includes the life form in relation to the substrate, epifauna or criptofauna, as well as its type of distribution considering the 2 main zoogeographic provinces recognized for the Gulf of Mexico: Carolinean and Caribbean; the species found only in the Gulf of Mexico are also noted. The list includes 195 species belonging to 9 groups of which Crustacea is the most diverse with 73 species, followed by Mollusca with 69 and Echinodermata with 18; the less diverse groups were Chelicerata with 2 species and Platyhelminthes and Sipuncula with 1 species each. Seventy-four species represent new locality records and 7 are new records for Veracruz. A total of 5 517 invertebrate species have been reported for the Mexican portion of the Gulf of Mexico, thus 3.5% of this total can be found in Montepio. More species were part of the epifauna (70%) than the criptofauna (30%) which is composed mainly by molluscs, polychaetes and sipunculids. A larger tropical affinity was observed in the obtained species composition; however, an important number of species are more subtropical or Carolinean (86) and 51 species occur only in the Gulf of Mexico.

It has been suggested that a latitudinal gradient exists of a low density of snags and high density of naturally-formed tree-cavities in tropical vs. temperate forests, though few cavities may have characteristics suitable for nesting by birds. We determined snag and cavity density, characteristics, and suitability for birds in a tropical dry forest biome of western Mexico, and evaluated whether our data fits the trend of snag and cavity density typically found in tropical moist and wet forests. We established five 0.25-ha transects to survey and measure tree-cavities and snags in each of three vegetation types of deciduous, semi-deciduous, and mono-dominant Piranhea mexicana forest, comprising a total of 3.75 ha. We found a high density of 77 cavities/ha, with 37 cavities suitable for birds/ha, where density, and characteristics of cavities varied significantly among vegetation types. Lowest abundance of cavities occurred in deciduous forest, and these were in smaller trees, at a lower height, and with a narrower entrance diameter. Only 8.6% of cavities were excavated by woodpeckers, and only 11% of cavities were occupied, mainly by arthropods, though 52% of all cavities were unsuitable for birds. We also found a high density of 56 snags/ha, with greatest density in deciduous forest (70 snags/ha), though these were of significantly smaller diameter, and snags of larger diameter were more likely to contain cavities. The Chamela-Cuixmala tropical dry forest had the highest density of snags recorded for any tropical or temperate forest, and while snag density was significantly correlated with mean snag dbh, neither latitude nor mean dbh predicted snag density in ten forest sites. The high spatial aggregation of snag and cavity resources in tropical dry forest may limit their availability, particularly for large-bodied cavity adopters, and highlights the importance of habitat heterogeneity in providing resources for primary and secondary cavity-nesters.