Mónica E. Riojas-López

Organchlorine content and shell thickness in brown booby (Sula leucogaster) eggs in the Gulf of California and the southern Pacific coast of Mexico

We determined egg concentrations of organochlorines and thickness of eggshells from brown boobies at eight colonies ranging from the northern Gulf of California to southern Mexico. The only common residue was that of DDE, which was found in almost all eggs. DDE content apparently reflected pre-1990 DDT use in nearby agricultural areas and, at one site, intensive mosquito control for high-end tourism development. There were no inter-colony differences in eggshell thickness, and variation in this variable likely reflected individual bird characteristics and/or individual feeding source. This variable was not a good proxy to DDE exposure of brown boobies, under current DDE levels in the brown booby trophic chain. In the northern Gulf of California, eggshell thickness has recovered to pre-DDT conditions. Our data indicate that the Gulf of California and southwestern coast of Mexico have a healthy near-shore marine environment, as far as organochlorines are concerned.

Breeding Locations of Seven Charadriiformes in Coastal Southwestern Mexico

Abstract. Between April and July 2007 we surveyed the coasts of Jalisco, Colima, Michoacán and Guerrero, in southwestern Mexico. We documented 33 breeding localities of seven species of Charadriiformes: six of Snowy Plover, two of Collared Plover, five of Wilsons Plover, three of Killdeer, one of Gull-billed Tern, and 16 of the Least Tern. We also located a potential colony of the Black Skimmer. Twenty of these locations were documented for the first time. Excepting breeding localities of the Killdeer and three-four of the Least Tern, all colonies were on salt-flats, likely due to the sand dunes bordering beaches being narrow, well vegetated and used heavily by humans, or, for Snowy Plovers, perhaps owing to greater food availability on saltflats. Our data elevated the conservation value of Laguna Cuyutlán, Colima, and discovered the value of the Xola-Paramán system, in Jalisco, and Laguna El Potosí system and La Parota, in Guerrero.

Plovers Breeding in the Highlands of Jalisco, Aguascalientes, Zacatecas, and San Luis Potosí, Central México

ABSTRACT. From April to July 2008, we surveyed for breeding plovers at 32 sites in the semiarid highlands of Jalisco, Aguascalientes, Zacatecas, and San Luis Potosí, in the Central Mexican High Plateau. We documented evidence or presumption of breeding Snowy Plovers (Charadrius alexandrinus) at 3 sites, Killdeer (C. vociferus) at 15 sites, and Mountain Plovers (C. montanus) at 1 site Our surveys showed that the region is important breeding ground for only the Killdeer. We documented an apparent breeding range extension of the Mountain Plover to slightly more than 200 km south of its previously known breeding range.

Biodiversity conservation in an anthropized landscape: Trees, not patch size drive, bird community composition in a low-input agro-ecosystem

One of the most typical agro-ecosystems in the Llanos de Ojuelos, a semi-arid region of central Mexico, is that of fruit-production orchards of nopales (prickly pear cacti). This perennial habitat with complex vertical structure provides refuge and food for at least 112 species of birds throughout the year. Nopal orchards vary in their internal structure, size and shrub/tree composition, yet these factors have unknown effects on the animals that use them. To further understand the conservation potential of this agro-ecosystem, we evaluated the effects of patch-size and the presence of trees on bird community composition, as well as several habitat variables, through an information-theoretical modelling approach. Community composition was obtained through a year of census transects in 12 orchards. The presence of trees in the orchards was the major driver of bird communities followed by seasonality; bird communities are independent of patch size, except for small orchard patches that benefit black-chin sparrows, which are considered a sensitive species. At least 55 species of six trophic guilds (insectivores, granivores, carnivores, nectivores, omnivores, and frugivores) used the orchards. Orchards provide adequate habitat and food resources for several sensitive species of resident and migratory sparrows. The attributes that make orchards important for birds: trees, shrubs, herb seeds, and open patches can be managed to maintain native biodiversity in highly anthropized regions with an urgent need to find convergence between production and biological conservation.

A New Wood Stork (Mycteria americana) Colony in Western México

Abstract. Breeding of Wood Storks (Mycteria americana) in western Mexico is limited to a few known sites from Guerrero to Chiapas. However, except for nesting at one Oaxaca site in 2005, all the colonies were reported over 35 years ago, while more recently published bird surveys in coastal wetlands of western Mexico have not reported any nesting Wood Storks. During April 2014, a newly established colony at Mogote Prieto, a mangrove-fringed island in Laguna Cuyutláns Basin III, Colima, was documented. This colony was visited on seven occasions during the spring and summer of 2014 and 2015. Maximum numbers in 2014 were 300 adult Wood Storks, including 36 clearly on nests and four carrying nesting materials (15 April 2014); 17 large, feathered chicks (12 June 2014); and 15 fledglings (12 July 2014). During 2015, there were fewer adults and nests, but more fledglings (n = 25 on 20 July 2015). Although the source of the nesting adults cannot be established, attention should be given to the conservation of this Wood Stork colony in western Mexico.

Half a century of changes in waterbird populations in a semiarid wetland system

Mexican inland wetlands in the arid and semiarid interior highlands historically held very large numbers of waterbirds. However, they have been deteriorated by agriculture, industrial and urban development, tourism and aquaculture, although the effects of this are known poorly. At the southern end of the Central Plateau of Mexico, the region of El Llano, in the states of Aguascalientes and Jalisco, is densely dotted with wetlands amidst an agricultural landscape. The wetlands that existed at the time of Spanish contact have disappeared or been modified, but many new ones have been created, including large and mid-size reservoirs, as well as small cattle watering tanks. The importance of this region for waterbirds was analyzed based on the data from the USFWS mid-winter Mexican waterfowl surveys, and surveys by ourselves in 1984–1985 and from 2010 to 2014. The data exhibited a peak in diving ducks in the late 1970s, which might reflect reservoir restoration and, or creation. Wetland water levels as well as their use by waterbirds was highly variable during the study period, and some sites that were important in 1984–1985 have silted and dried up. The major waterbird trend in the survey area has been a steady increase in the number of the threatened Mexican Duck since the late 1970s until 2010–2011, that might have been resulted from a reduction in its hunting and egg collecting, and, or improvement in nesting habitat, along with reservoir creation or restoration.

Reconsideration of the nomadic condition of the southernmost Guachichiles based on the relationship with their environment

BackgroundThe Guachichiles were a group of Chichimeca people that inhabited the southern and central parts of the Mexican Plateau. In the southern area of their distribution, they occupied and used the tunales, extensive forests of arborescent nopales (Opuntia spp.). Their pre-Columbian distribution was dissected by the Royal Silver Road established by the Spaniards, and this lead to them being main protagonists in the so-called Chichimeca War, during the sixteenth century. With very little first-hand documentation, the Guachichiles were described as savage, warring, primitive, hunting nomads, but little efforts have been done to understand their daily life habits. Based on the relationship of pre-Columbian southern Guachichiles with their environment, we re-valuate whether they were nomads, as the Chichimecas collectively have been labeled, or whether those living in tunales could live year-round in this habitat. As part of our analysis, we propose the primary plant and animal species that integrated their diet.MethodsWe draw information from a review of bibliographic sources, complemented with extensive searches in all pertinent Mexican archives. We carried out field work to define the geographical extent of the pre-Columbian territory of the southernmost Guachichiles, based on the Spanish Chronicles, remnant fragments of vegetation, landscape characteristics, and geographic names related with nopales. Using approaches from wildlife ecology, historical sciences and ethnobiological information on wild resources currently or recently used in the area, we proposed which resources were available to the southernmost Guachichiles, and how their primary diet might have been.ResultsThe habitat of the southern Guachichiles, the tunal forest, was exuberant and rich in resources, having provided numerous plant products, of which tunas (prickly pears) and mesquite pods were of uttermost importance. At least 10 plant foods were available within the tunales. They would have consumed at least seven birds (including their eggs), six mammals, four reptiles, grubs, and honey, in addition to at least six vertebrate species hunted at the edges of the tunal with grasslands and shrublands or in more open patches of tunal. In addition to food, they prepared at least three alcoholic beverages, had access to two species of probable psychoactive beehive cacti and to one hallucinogenic mushroom species, and might have traded peyote from the north with outside-tunal Guachichiles.ConclusionsThe rich habitat in which southern Guachichiles lived allowed them to be largely sedentary, but this required that they prevented other groups from gathering and hunting in their habitat. As a result of them living in and defending the tunales, the Guachichiles could have been divided into two or three habitat-driven groups: Tunal Guachichiles, and grassland and, or shrubland Guachichiles.

The Demise of a Tropical Coastal Lagoon as Breeding Habitat for Ground-Nesting Waterbirds: Unintended, but Anticipated Consequences of Development

ABSTRACT Laguna Cuyutlán (Colima, Mexico), an Important Bird Area, used to provide breeding habitat for ground-nesting waterbirds. During 2014 and 2015, nesting efforts of laughing gull, black skimmer, and royal, gull-billed and Forsters terns failed almost completely due to inundation, while least terns and snowy plovers fared the same during 2014. No anomalies in rainfall, tidal level, or coseismic subsidence explained such failure. Rather, the inundations were due to the enlarging of Canal Tepalcates that connects the lagoon with the sea, which was widened from 100 to 300 m and dredged to 17-m deep. Before this, the hydrodynamics were regulated by evaporation and runoff. Now, increased seawater volumes dominate the basins hydrodynamics. The failure of Laguna Cuyutlán as a breeding habitat for these birds is an important threat for these species, as this lagoon held one of the < 20 colonies known for several of these species along the western coast of North and Central America. Documenting this demise of Laguna Cuyutlán for ground-nesting waterbirds transcends the regional scale as it emphasizes the little consideration still given to biodiversity vs. economic development, and is a warning for coastal projects in other developing areas of the world.