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Response to Castillo-Guerrero et al. (2021) Critique of Albores-Barajas et al. (2020) on Establishing Seabird Conservation Needs in Northwestern Mexico
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In Northwestern Mexico, approximately 40 breeding species of seabirds have been reported, with several threats (e.g., invasive species introduction and habitat loss) affecting the viability of their populations. As such, it is necessary to take action for their protection. To prioritize conservation activities, 119 reports (governamental agency monitoring programs, grey literature, and scientific literature) were analyzed for research and monitoring results from 1922-2018 (93 of 119 published after 1990) and ranked the different islands (91 sites, including archipelagos with multiple islands) based on their breeding seabird communities (35 species in 11 seabird families, including 7 endemic breeders). For the ranking exercise, three criteria were considered: conservation category, preferred habitat, and foraging guild for each species. Taking into consideration the breeding species on each island, an index to rank the islands was created. Ten islands or archipelagos have high conservation priority (index score > 10 = high priority; mean index = 4.7, median = 5.0, max = 17.9, n = 91), and the most important are: Revillagigedo and San Benito archipelagos, Coronado, San Lorenzo, and Natividad Islands. It is necessary to use new tools and techniques to determine populations' sizes and trends and to create a baseline to compare with future studies. Furthermore, many of the species breeding or feeding in the Mexican Economic Exclusive Zone migrate to other latitudes, elevating the conservation problem to an international scale.
The Baja California Pacifi c Islands, Mexico, are globally important breeding sites for 22 seabird species and subspecies. In the past, several populations were extirpated or reduced due to invasive mammals, human disturbance, and contaminants. Over the past two decades, we have removed invasive predators and, for the last decade, we have been implementing a Seabird Restoration Programme on eight groups of islands: Coronado, Todos Santos, San Martín, San Jerónimo, San Benito, Natividad, San Roque, and Asunción. This programme includes monitoring; social attraction techniques; removal of invasive vegetation; reducing human disturbance; and an environmental learning and biosecurity programme. Here, we summarise historical extirpations and recolonisations during the last two decades of restoration actions, and we update the status of breeding species after more than a decade. To date, from 27 historically extirpated populations, 80% have returned since the fi rst eradication in 1995. Social attraction techniques were key in recolonisations of Cassin’s auklet (Ptychoramphus aleuticus), royal tern (Thalasseus maximus), and elegant tern (T. elegans). A total of 19 species breed on these islands, four more species than a decade ago, including 12 new records. The most abundant seabirds, black-vented shearwater (Puffi nus opisthomelas), Cassin’s auklet, western gull (Larus occidentalis), and Brandt’s cormorant (Phalacrocorax penicillatus), have shown a remarkable population increase. Current threats include the potential reintroduction of invasive mammals, guano mining, recreational activities, pollution, and commercial fisheries. To maintain these conservation gains in the long-term it is necessary to continue implementing restoration actions and reinforcing protection on these important natural protected areas.
Estimating the population of burrow-nesting seabirds is a challenging task, as human presence in the colony creates disturbances and can damage burrows and occupants. Here, we present a novel method using aerial photographs taken with Unmanned Aerial Vehicles (UAVs) to estimate the population size of a burrow-nesting seabird, the Black-vented Shearwater (Puffinus opisthomelas), on Natividad Island, Mexico. Our results provide a census of burrows in the colony, with very low detection error (5.6%). This is greater accuracy compared to other methods based on extrapolating results from sample plots to total colony area. We then combined this burrow census with ground truth data on occupancy to estimate population size. We obtained a population estimate of 37,858 and 46,322 breeding pairs for 2016 and 2017 respectively. The proposed method provides a cost effective and repeatable approach for monitoring numbers of burrows occupied in a colony, thereby enabling easier and faster estimates of population trends. We suggest this method can be valid for other burrow-nesting species in habitats without dense vegetation cover.
Conservation resources are limited, yet an increasing number of species are under threat. Assessing species for their conservation needs is, therefore, a vital first step in identifying and prioritizing species for both ex situ and in situ conservation actions. Using a transparent, logical and objective method, the Conservation Needs Assessment process developed by Amphibian Ark uses current knowledge of species in the wild to determine those with the most pressing conservation needs, and provides a foundation for the development of holistic conservation action plans that combine in situ and ex situ actions as appropriate. These assessments allow us to maximize the impact of limited conservation resources by identifying which measures could best serve those species requiring help. The Conservation Needs Assessment complements the IUCN Red List assessment, and together they provide a more holistic guide to conservation priorities and actions. Conservation Needs Assessments generate national prioritized lists of species recommended for conservation action. These can subsequently be used to assist in the development of species recovery plans and national action plans, or to inform national conservation priorities better. Additional tools that will evaluate the recommendations for ex situ rescues, to determine the best candidates for conservation breeding programmes, are currently under development.
The Red-billed Tropicbird (Phaethon aetehreus) is a seabird that breeds on islands in tropical seas. The Mexican government has listed it as threatened; however, the International Union for Conservation of Nature considers it of least concern, although it recognizes that its global population is decreasing. Its breeding ecology was studied at Peña Blanca island, Colima, México, through monthly visits from 15 January 2008 to 10 December 2009. By extrapolating density in a 4,227-m2 survey area, 1,390 (2008) and 1,225 (2009) nests were estimated for the entire colony. In both years, the earliest eggs were laid in September, and the last active nests were recorded during 14 May-19 June, with peak activity on 7 March 2008 and 25 February 2009. Egg volume was not different between years (57.4 cm3 ± 5.1 vs. 56.8 ± 3.3), but nest success was higher in 2008 (77% vs. 57% in 2009). Highest nest densities occurred between January and May, coincident with regional upwelling processes (colder water and high concentration of nitrites, nitrates and chlorophyll-a). The Red-billed Tropicbird colony on Peña Blanca is the largest
Mexican colony and one of the two largest colonies of the world.
The breeding distribution and population size of the Red-billed Tropicbird (Phaethon aethereus) in Mexico were reviewed. This species has been confirmed to breed on 14 and potentially breed on six Mexican Pacific islands: two in the North Pacific, 12 in the Gulf of California, and six in the Tropical Pacific. The breeding population has been estimated to be approximately 1,901-2,725 breeding pairs. This estimate includes between 507-713 pairs in the Gulf of California, 1,391-2,004 pairs in the Tropical Pacific, and the rest in the North Pacific. The largest colonies are Peña Blanca in Colima (1,250-1,650 pairs), Farallón de San Ignacio in Sinaloa (150-228 pairs), San Pedro Mártir in Sonora (150-190 pairs), San Benedicto in the Revillagigedo archipelago (50-200 pairs), Isabel in Nayarit (87-155 pairs), and Morros El Potosí in Guerrero (100 pairs). The portion of the population that breeds in Mexico is numerically important at both regional (Pacific Ocean) and global scales, representing approximately 50% of eastern Pacific breeding pairs and 25% of the global population, respectively. Therefore, protection of these colonies can play an important role in the global conservation of this species.
Breeding ecology of the Brown Booby (Sula leucogaster) in three islands of the Mexican tropical Pacific Ocean The Brown Booby (Sula leucogaster) is a seabird that breeds in islands of tropical and subtropical seas. In the Mexican Pacific, it has been the subject of several studies, but little was known on the dynamics of its colonies and the influence of oceanic variables on them. We studied the breeding ecology of the Brown Booby at three southern Mexico islands: Paja‐ rera and Cocinas in Bahía Chamela, Jalisco, and Peña Blanca in Colima. We visited each island monthly from, respectively) was 724 and 758 breeding pairs at Cocinas, 895 and 1,071 at Pajarera, and 15,215 and 15,801 at Peña Blanca. We observed active nesting year‐round, but the highest densities in both years were from April to July, when sea surface temperature was higher and levels of chlorophyll a, lower. The breeding period was associated with the presence of warm water masses, which is the opposite to the pattern previously recorded in Gulf of California colonies, but coin‐ cided with the presence of migratory fish. This difference in breeding phenology seems an adaptation to match local con‐ ditions (prey availability) during chick rearing. Breeding parameters (higher clutch size, egg volume, hatching success) point out that Peña Blanca, the largest colony, was superior to the other colonies in terms of breeding. Differences among years and colonies seem related to oceanic variability, which affects the local availability of prey. Based on the size of the colony, which makes it one of the largest colonies along the Mexican Pacific coast, the Peña Blanca colony qualifies to be nominated as Important Bird Area (IBA).
The California Brown Pelican subspecies (Pelecanus occidentalis californicus) was removed from the US endangered species list in 2009, along with the entire species of Brown Pelican throughout North America. The Gulf of California subpopulation within the entire metapopulation (= subspecies) comprises the majority of nesting (~76% of P. o. californicus). The US classifications were based on pollution effects in the Southern California Bight (SCB) during the early 1970s; official listing-recognition in Mexico (NOM-059-SEMARNAT-2010) occurred in 2010 and it continues. Unfortunately, Brown Pelican conservation across the US/Mexico border has been largely uncoordinated. Recent declines in the SCB subpopulation are not well-documented, whereas representative subpopulations in the Gulf of California have received continual study since the US listing. Until the early 2000s, Gulf pelican breeding populations changed little. El Niño/Southern Oscillation continues to be a major factor driving annual pelican breeding intensity and success, with a slightly weaker effect to the north. Nest attempts (NA) in the southern Midriff zone and to the south of our monitoring zone have declined in the last decade, in especially extreme and unprecedented ways in a period of unusual warming in the last 3 years (2014-2016), termed by some as the “Blob”. Other factors (such as human disturbance and commercial fishing) have likely exacerbated recent warming effects in some areas. Recent data also suggest the pelican is in a process of minor range-shifting toward the northern Gulf, and there are no definitive indications of a recent NA decline in that zone. Monitoring over the entire range, past 2016, will be important to determine whether populations have begun a long-term decline or will recover to normal baseline levels. The health of pelican populations is an important indicator of overall ecological health in the Pacific region and not an isolated phenomenon.
During the 2010-2011 and 2011-2012 breeding seasons (November to June), there were 21 colonies of 13 species, with at least 40,000 to 50,000 pairs of seabirds on six islands of Bahía Santa María-La Reforma in Mexico. Bahía Santa María maintains the largest breeding congregation of the west coast of Mexico for Laughing Gull (Leucophaeus atricilla; 22,000 pairs), Royal Tern (Thalasseus maximus; 11,000 pairs) and Black Skimmer (Rynchops niger; 1,500 pairs). In the past decade, most of the species that breed on El Rancho Island (coastal dune habitat) have increased their population size, apparently related to a combination of factors such as colonies recently established (and hence still expanding) and increased habitat availability. On the other hand, species breeding on islands with mangroves seem to be decreasing (in particular the Brown Pelican (Pelecanus occidentalis) population), but with no obvious reason to explain these low numbers of some species. Despite the small size of the islands used by breeding seabirds, this coastal system supports important seabird populations and its conservation should be a priority.
In early June 2000 we surveyed 3 islets at the southern end of Isla Guadalupe, Mexico: Islote de Afuera (or Islote Zapato), Islote de Adentro (or islote Toro), and Islote Negro, to document nesting seabirds. We found vestiges of over 100 Leach's Stormpetrels (Oceanodroma leucorhoa), 31 Xantus Murrelets (Synthliboramphus hypoleuca), and 1 Cassin's Auklet (Ptychoramphus aleuticus) that had been depredated. The evidences point to Burrowing Owls (Athene cunicularia) as the predator of the stormpetrels, but, because of its size, probably other birds were involved in murrelet and auklet predation. Based on the characteristics of the remains, the depredated Leach Stormpetrels belonged to the population that had nested during the previous winter. The information is not sufficient to determine whether such predation represents a conservation problem for small seabirds on Isla Guadalupe, but suggest that the issue should be studied further.
Vertebrates are currently going extinct at an alarming rate, largely because of habitat loss, global warming, infectious diseases, and human introductions. Island ecosystems are particularly vulnerable to invasive species and other ecological disturbances. Properly documenting historic and current species distributions is critical for quantifying extinction events. Museum specimens, field notes, and other archived materials from historical expeditions are essential for documenting recent changes in biodiversity. The Islas Revillagigedo are a remote group of four islands, 700-1100 km off the western coast of mainland México. The islands are home to many endemic plants and animals recognized at the specific- and subspecific-levels, several of which are currently threatened or have already gone extinct. Here, we recount the initial discovery of an endemic snake Hypsiglena ochrorhyncha unaocularus Tanner on Isla Clarión, the later dismissal of its existence, its absence from decades of field surveys, our recent rediscovery, and recognition of it as a distinct species. We collected two novel complete mitochondrial (mt) DNA genomes and up to 2800 base-pairs of mtDNA from several other individuals, aligned these with previously published mt-genome data from samples throughout the range of Hypsiglena, and conducted phylogenetic analyses to infer the biogeographic origin and taxonomic status of this population. We found the Isla Clarión population to be most closely related to populations in the Sonora-Sinaloa state border area of mainland México and Isla Santa Catalina, in the Gulf of California. Based on genetics, morphology, and geographic distributions, we also recognize these two other lineages as distinct species. Our study shows the importance of museum specimens, field notes, and careful surveys to accurately document biodiversity and brings these island endemics (Clarión and Santa Catalina nightsnakes) and mainland population near the Sonora-Sinaloa state border to the attention of conservation biologists currently monitoring biodiversity in these fragile subtropical ecosystems.
Human activities, especially increased nutrient loads that set in motion a cascading chain of events related to eutrophication, accelerate development of hypoxia (lower oxygen concentration) in many areas of the world's coastal ocean. Climate changes and extreme weather events may modify hypoxia. Organismal and fisheries effects are at the heart of the coastal hypoxia issue, but more subtle regime shifts and trophic interactions are also cause for concern. The chemical milieu associated with declining dissolved oxygen concentrations affects the biogeochemical cycling of oxygen, carbon, nitrogen, phosphorus, silica, trace metals, and sulfide as observed in water column processes, shifts in sediment biogeochemistry, and increases in carbon, nitrogen, and sulfur, as well as shifts in their stable isotopes, in recently accumulated sediments.
In 2009, the Brown Pelican Pelecanus occidentalis was removed from the US Endangered Species List. The California subspecies P. o. californicus (hereafter CABRPE) was also removed from the California state endangered species list. Three years earlier (2006), we estimated the metapopulation of CABRPE to be 70 680 ± 2 640 breeding pairs (mean ± SD) and 195 900 ± 7 225 individuals. The largest single breeding aggregation within the range occurred among two to three islands of the San Lorenzo Archipelago, Gulf of California (GOC), totaling ~17 225 breeding pairs, or ~24.4% of the metapopulation. This and the other 4 subpopulations were composed of a single "core" breeding aggregation (on one or a few adjacent islands) and many smaller but isolated colonies (a colony represents all birds on a single island). Extremely small colonies (<65 nests) made up ~35.6% of total colonies, but only ~ 0.9% of the total estimated numbers, corrected for detectability. Modal colony size throughout the range was much smaller (230 to 1 300 breeding pairs), indicating that small, scattered colonies and sub-colonies have a function in CABRPE distributional dynamics and demography. Thus, negative single-survey data (no occupancy and small numbers) still have conservation importance as alternate or growing colonies in source-sink dynamics. Little numerical change in CABRPE in at least three decades was indicated from less precise data south of the northernmost Southern California Bight (SCB) subpopulation, but significant recent improvements in the SCB were reflected by our high estimates in 2006, supporting the USFWS delisting. At that time, we estimated the improved SCB breeding population as 11 695 ± 450 pairs. However, continuing threats throughout the range, especially in the south, now include commercial fishing, tourist developments, increased human activities, and extensive/expanding aqua-cultural developments (as well as, to a lesser degree, agricultural activities). Repeated endangerment is a possibility. Continued monitoring will be important.
During the 1983/84 winter breeding season, Laysan Albatrosses Phoebastria immutabilis bred in the eastern Pacific for the first time in recorded history, on Guadalupe Island, Mexico. By 1991/92, the last reported census, the population had grown to 45 pairs. We conducted censuses during 1999/2000 and 2000/01 and found that, in addition to nesting at the only previously known colony (on the main island), albatrosses were breeding at another site on the main island and on two offshore islets. We estimated the entire population to be a minimum of 119 and 193 pairs for each of the two seasons respectively. Although the colonies on the main island are threatened by predation pressure from introduced mammals, the offshore islets remain predator-free. During June 2000, we also collected 27 chick regurgitation pellets (comprised only of indigestible hard parts) for analysis of diet. The pellets included beaks from a minimum of 964 individual cephalopods representing a minimum of 12 families and 22 species. The most common species were squids: Histioteuthis hoylei (20.4% of identified beaks), Taonius borealis (13.8%), Gonatus pyros (11.2%), and Galiteuthis? sp. A (11.0%). A previous study from colonies in Hawaii identified ommastrephid squids as the most important prey, but we did not find any in our sample. The reason(s) for this discrepancy are not clear. It has been suggested that Laysan Albatrosses catch squid at night, taking them alive when they migrate to the surface. Most of the squids that we identified were species that live only in deep water, but after mating the females die and float to the surface. That knowledge, coupled with recently published results indicating that foraging Laysan Albatrosses regularly feed during the daytime, leads us to conclude that Laysan Albatrosses probably take most of their squid prey by diurnal scavenging.
Description of the population growth of the Laysan albatrosses (Diomedea immutabilis) at Isla Guadalupe from 1983 to 1993.
A vast number of prioritization schemes have been developed to help conservation navigate tough decisions about the allocation of finite resources. However, the application of quantitative approaches to setting priorities in conservation frequently includes mistakes that can undermine their authors’ intention to be more rigorous and scientific in the way priorities are established and resources allocated. Drawing on well-established principles of decision science, we highlight 6 mistakes commonly associated with setting priorities for conservation: not acknowledging conservation plans are prioritizations; trying to solve an ill-defined problem; not prioritizing actions; arbitrariness; hidden value judgments; and not acknowledging risk of failure. We explain these mistakes and offer a path to help conservation planners avoid making the same mistakes in future prioritizations.
Seis Errores Comunes en la Definición de Prioridades de Conservación
Resumen
Se ha desarrollado un vasto número de esquemas de priorización para ayudar a que la conservación navegue entre decisiones difíciles en cuanto a la asignación de recursos finitos. Sin embargo, la aplicación de métodos cuantitativos para la definición de prioridades en la conservación frecuentemente incluye errores que pueden socavar la intención de sus autores de ser más rigurosos y científicos en la manera en que se establecen las prioridades y se asignan los recursos. Con base en los bien establecidos principios de la ciencia de la decisión, resaltamos seis errores comúnmente asociados con la definición de prioridades para la conservación: no reconocer que los planes de conservación son priorizaciones; tratar de resolver un problema mal definido; no priorizar acciones; arbitrariedad; juicios de valor ocultos y no reconocer el riesgo de fracasar. Explicamos estos errores y ofrecemos un camino para que planificadores de la conservación no cometan los mismos errores en priorizaciones futuras.
Usamos una técnica de muestreo doble (muestreos aéreos y terrestres) en 2006, con cobertura doble parcial, para estimar el tamaño poblacional actual de las poblaciones reproductivas de Pandion haliaetus en el noroeste de México (costa de Baja California, islas en el Golfo de California y las costas de Sonora y Sinaloa). Con excepción de las islas de Natividad, Cedros y San Benitos a lo largo de la costa pacífica de Baja California (las tres fueron excluidas de nuestra cobertura en 2006 debido a la niebla), este estudio repitió los muestreos que habíamos realizado con el mismo protocolo en 1977 y 1992/1993, lo que nos permitió estimar las tendencias poblacionales a nivel regional. El tamaño poblacional mínimo estimado para el área de estudio en 2006 fue de 1343 parejas anidando, lo que significa un aumento de 81% desde 1977, pero sólo de 3% desde 1992/1993. La población de Baja California del lado del Golfo permaneció generalmente estable durante los tres muestreos (255, 236 y 252 parejas, respectivamente). Las poblaciones de las Islas Midriff (Golfo de California, próximas a la latitud 29°N) permanecieron similares desde 1992/1993 (308 parejas) hasta 2006 (289 parejas), pero con cambios poblacionales notables en las dos islas más grandes (Ángel Guardián: 45 a 105 parejas [133% de aumento]; Tiburón: 164 a 109 parejas [34% de disminución]). El tamaño estimado mínimo de la población de P. haliaetus en Sonora continental disminuyó de manera similar al de la Isla Tiburón adyacente, i.e., en un 26%, desde 214 parejas en 1993 a 158 parejas en 2006. En contraste, la población en la costa de Sinaloa, que había disminuido en un 150% entre 1977 y 1993, creció de nuevo en un 58% entre 1993 y 2006, desde 180 hasta 285 parejas. Nuestros estudios confirmaron los patrones descriptos previamente de cambios poblacionales rápidos a escala local, junto con cambios aparentes en la distribución espacial. La gran población que nidifica en el suelo, que hasta hace poco anidaba en dos islas en la laguna San Ignacio (lado del Océano Pacífico, Baja California), no estuvo presente en las islas en 2006. Sin embargo, un número equivalente de parejas fue encontrado al norte y al sur de la laguna, anidando en pueblos y a lo largo de líneas eléctricas elevadas, sin un cambio global en el tamaño poblacional para esta área en general (198 parejas en 1992; 199 en 2006). El uso de estructuras artificiales de anidación fue de 4.3% en 1977 y de 6.2% en 1992/1993, pero aumentó a 26.4% en 2006. El uso de los postes que sostienen las líneas eléctricas elevadas representa un riesgo de electrocución para P. haliaetus y también causa cortes de energía e incendios. Recomendamos la modificación de estos postes para que puedan alojar de modo seguro los nidos de P. haliaetus, como se ha logrado exitosamente en muchos países.
Many seabird species of conservation concern have large geographic ranges that span political borders, forcing conservation planners to facilitate their protection in multiple countries. Seabird conservation planning within the seabird-diverse California Current System (CCS) marine ecoregion presents an important opportunity for transboundary collaborations to better protect seabirds across the USA/México border. While seabird populations in the USA are relatively well-studied and well-protected, the status of seabird populations in the Mexican region of the CCS is not well known and seabird colonies have been virtually unprotected. This study synthesizes and supplements information on breeding seabird diversity and distribution, identifies and ranks threats to seabirds and evaluates conservation capacity in the Mexican CCS to provide a framework for transboundary seabird conservation throughout the CCS ecoregion. Island-breeding seabirds in México support 43–57% of CCS breeding individuals, 59% of CCS breeding taxa and a high level of endemism. Connectivity between populations in México and the USA is high. At least 17 of the 22 extant Mexican CCS breeding seabirds are USA/México transboundary breeders or foragers, 13 of which are federally listed in the USA or México. Introduced predators and human disturbance have caused multiple seabird population extirpations in the Mexican CCS because breeding colonies lack legal protection or enforcement. However, conservation capacity in this region has increased rapidly in recent years through the establishment of new protected areas, growth of local conservation non-governmental organizations, and increase in local community support, all of which will allow for more effective use of conservation funds. Transboundary conservation coordination would better protect CCS seabirds by facilitating restoration of seabird colonies in the Mexican CCS and enabling an ecoregion-wide prioritization of seabird conservation targets to direct funding bodies to the most cost-effective investments.
Along the Pacific coast of North America, from Alaska to Mexico, harmful algal blooms (HABs) have caused losses to natural resources and coastal economies, and human sicknesses and deaths for decades. Recent reports indicate a possible increase in their prevalence and impacts of these events on living resources over the last 10–15 years. Two types of HABs pose the most significant threat to coastal ecosystems in this ‘‘west coast’’ region: dinoflagellates of the genera Alexandrium, Gymnodinium, and Pyrodinium that cause paralytic shellfish poisoning (PSP) and diatoms of the genus Pseudo-nitzschia that produce domoic acid (DA), the cause of amnesic shellfish poisoning (ASP) in humans. These species extend throughout the region, while problems from other HABs (e.g., fish kills linked to raphidophytes or Cochlodinium, macroalgal blooms related to invasive species, sea bird deaths caused by surfactant-like proteins produced by Akashiwo sanguinea, hepatotoxins from Microcystis, diarrhetic shellfish poisoning from Dinophysis, and dinoflagellate-produced yessotoxins) are less prevalent but potentially expanding. This paper presents the state-of-knowledge on HABs along the west coast as a step toward meeting the need for integration of HAB outreach, research, and management efforts.
National red lists of threatened animal and plant species prepared according to the criteria of the World Conservation Union (IUCN) adequately reflect the extinction risk of species within a country but cannot be used directly to set conservation priorities. In particular, the significance of national populations for the conservation of the species as a whole is not taken into account. We present a procedure that can be used to assess national responsibility based on the national red-list status of a species, the international impor-tance of the national population, and the species' "historical rarity" status. We distinguished five responsibility classes for breeding birds: B1, threatened species with internationally important populations in Switzerland; B2, threatened species with internationally less important populations; B3, nonthreatened species with inter-nationally important populations; B4, nonthreatened species with internationally less important populations; and B5, species that have never been common in Switzerland. Two responsibility classes were distinguished for birds occurring in Switzerland as visitors: G1, species with large concentrations in Switzerland and an unfavorable conservation status in Europe, and G2, species with large concentrations in Switzerland and a favorable conservation status in Europe. Two additional classes (G3 and G4) for visiting species occurring in internationally less important numbers are possible but were not analyzed in detail. Responsibility classes B1, B2, B3, G1, and G2 were defined as species of national conservation concern. We developed the method for birds in Switzerland, but it can be used in other countries and for other taxonomic groups as well. It is particularly suitable where national red lists are established according to IUCN guidelines.
En 1998 y 1999 revisé las colonias de aves acuáticas que anidan en Isla San Jorge, La Purinera e Isla Montague, en el norte del Golfo de California, al igual que la de lobos marinos de la Isla San Jorge. Encontré que El Niño coincidió con que los bobos cafés de San Jorge dejaran de anidar y se ausentaran de la isla, al tiempo que llegaban varios miles de bobos de patas azules. Las condiciones de El Niño coincidieron con un incremento en el número de individuos anidantes de gallitos menor, elegante y máximo y de rayadores, en Montague. Ni los patos buzo orejones en San Jorge, ni los gallitos menores en La Purinera, ni las garzas níveas, perros de agua , gaviotas risueñas, ni gallitos picogrueso, en Montague, parecen haber sido afectados. Los lobos marinos en San Jorge duplicaron aproximadamente su población, sin que esto repercutiera sobre la producción de crías. La Niña coincidió con un regreso de las poblaciones de las especies anteriores a las condiciones previas a El Niño. Además, durante 1999 en San Jorge anidaron gaviotas plomas y patos buzo de Brandt. Esa gaviota había dejado de anidar hacía mucho tiempo en San Jorge, y el pato buzo nunca se había registrado anidando ahí. Es prematuro concluir si estos registros fueron resultado de La Niña o de fenómenos en otra escala.
doi: https://doi.org/10.22201/igeof.00167169p.2003.42.3.944
Slowing rates of global biodiversity loss requires preventing species extinctions. Here we pinpoint centers of imminent extinction, where highly threatened species are confined to single sites. Within five globally assessed taxa (i.e., mammals, birds, selected reptiles, amphibians, and conifers), we find 794 such species, three times the number recorded as having gone extinct since 1500. These species occur in 595 sites, concentrated in tropical forests, on islands, and in mountainous areas. Their taxonomic and geographical distribution differs significantly from that of historical extinctions, indicating an expansion of the current extinction episode beyond sensitive species and places toward the planet's most biodiverse mainland regions. Only one-third of the sites are legally protected, and most are surrounded by intense human development. These sites represent clear opportunities for urgent conservation action to prevent species loss.
• biodiversity
• conservation
• protected area
• threatened species
The Islas Revillagigedo consist of four volcanic, oceanic islands located 400 miles west of Colima, Mexico. The islands in order of increasing size are: Roca Partida, San Benedicto, Clarion, Socorro. The terrestrial fauna of the islands is depauperate and disharmonic and consists of birds, three species of reptiles, and flying and rafting arthropods. Many of the species of sea birds and shore birds are cosmopolitan or cosmotropic, while the plants, reptiles and land birds show their greatest affinity to the mainland Sonora-Sinaloa are of Mexico. Prevailing currents in the Gulf of California favour chance dispersal to the islands. The percentage of the biota which is endemic is high. The degree of endemism of birds seems to be favoured by the size of the island and the diversity of habitats, while endemism and success of establishment by reptiles seems favoured by the age of the island. This seems consistent with methods of dispersal (flying versus rafting). There is no evidence of adaptive radiation of the terrestrial vertebrates within the islands. Recent introductions of exotic species have upset the apparent stability of the fauna and flora of these islands.
Heermann's Gulls (Larus heermanni) have been reported to nest on 19 islands in Mexico, but during 1999-2000 they bred on only twelve. Of the known active colonies, one, Isla Rasa, harbors over 95% of the breeding numbers, with between 300,000-400,000 adults. Three islands each support between 2,000 and 20,000 adults, and the rest from 4 to 2,000 adults. The colonies of this species have exhibited major variations through time, but data are inadequate to judge whether human activities or changes in oceanographic conditions were the cause of these variations. These two, along with size and distribution of nesting colonies, should be monitored, if the species' population dynamics are to be understood.
Population genetic structure was characterized in Xantus's Murrelet (Synthliboramphus hypoleucus) by analyzing variation in the mitochondrial control region (505 samples) and 12 microsatellite loci (428 samples) in birds captured at all 13 current breeding areas in southern California and northwestern Baja California, Mexico. The two types of molecular markers were consistent in revealing strong genetic differentiation between the two currently recognized subspecies (S. h. hypoleucus and S. h. scrippsi) and little or no differentiation among breeding areas within subspecies. Estimates of gene flow were essentially zero, and no evidence for admixture was found. Gene flow among breeding locations within subspecies, on the other hand, was seemingly high. Given these genetic results, as well as clear morphological differences between the subspecies and the apparent lack of interbreeding at breeding areas where the two forms are sympatric, we suggest that two species be recognized. Both forms are genetically distinct from Craveri's Murrelet (S. craveri), a closely related species whose breeding range partially overlaps that of Xantus's Murrelet. Taxonomic subdivision of Xantus's Murrelet introduces new conservation concerns, especially for S. h. hypoleucus, which urgently requires greater study and protective efforts.
The brush and tree lizards (Urosaurus) are a small clade of phrynosomatid lizards native to western North America. Though not as well known as their diverse sister clade, the spiny lizards (Sceloporus), some Urosaurus have nonetheless become model organisms in integrative biology. In particular, dramatic phenotypic and behavioral differences associated with specific mating strategies have been exploited to address a range of ecological and evolutionary questions. However, only two phylogenies have been proposed for the group, one of which is pre-cladistic and both based principally on morphological characters that might not provide robust support for relationships within the group. To help provide investigators working on Urosaurus with a robust phylogeny in which to frame ecological and evolutionary questions, we establish a molecular phylogeny for the group. We sampled three mitochondrial and three nuclear loci, and estimated phylogenetic relationships within Urosaurus using both maximum parsimony (MP) and Bayesian inference (BI), as well as a coalescent-based species tree approach. Finally, we used two methods of ancestral state reconstruction (ASR) to gain insight into the evolution of microhabitat preference and male display signals, traits that have been the focus of studies on Urosaurus. All reconstruction methods yield nearly the same ingroup topology that is concordant in most respects with the previous cladistic analysis of the group but with some significant differences; our data suggest the primary divergence in Urosaurus occurs between a clade endemic to the Pacific versant of Mexico and the lineages of Baja California and the southwestern US, rather than placing Urosaurus graciosus as the basal taxon and linking the Baja and Mexican endemics. We find support for a single transition to a saxicolous lifestyle within the group, and either the independent gain or loss of arboreality. The evolution of throat color patterns (i.e. dewlaps) appears complex, with multiple color morphs likely involving orange reconstructed as ancestral to the group and to most lineages, followed by a single transition to a fixed blue-throated morph in one clade. These results should provide a useful framework for additional comparative work with Urosaurus, and establish the phylogenetic context in which Urosaurus diversity arose.
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.
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