Seasonal richness and abundance of raptors across the bioclimatic belts of the Sierra de San Pedro Mártir, Baja California, Mexico

Freshwater availability is one of the most pressing environmental concerns in arid ecosystems. The use of free-standing water by raptors has been little studied, and in the context of climate change has become increasingly important as extended droughts are expected to become more frequent. We analyzed digital images from camera traps captured in the freshwater springs of Sierra El Mechudo, during summer to early autumn of 2023 and 2024 in Baja California Sur, Mexico. We recorded 165 detections of four raptor species. The Turkey Vulture (Cathartes aura) was the most frequently detected (n = 55), followed by the Great Horned Owl (Bubo virginianus) (n = 50), the Red-tailed Hawk (Buteo jamaicensis) (n = 45), and the Cooper’s Hawk (Astur cooperii), which was observed only in early autumn 2024 (n = 15). The Great Horned Owl exhibited a distinct detection pattern (mainly crepuscular, with the highest peak at 6 a.m.), in contrast with the other three species, which were detected mainly at midday and in the afternoon, during the hottest hours of the day. All raptors were recorded drinking water; however, species differed in the proportion of behaviors they exhibited at the freshwater springs. The Turkey Vulture showed the highest drinking activity (76.3%), whereas both hawks exhibited the same lowest proportions (26.6%) among all species detected. The proportion of behaviors remained constant across years. The time spent at the freshwater springs did not differ across species or years. The Red-tailed Hawk, the Great Horned Owl, and the Turkey Vulture increased their detections at the springs in 2024, when a severe and prolonged drought affected the southern peninsula. The results showed that the importance of freshwater springs for raptors extends beyond their use for drinking only; the surrounding habitat as a refuge and availability of prey in the area are evidently essential for these birds of prey. Further studies should extend research into the diverse use of springs and home ranges of raptors in the southern Baja California peninsula.

Effects of habitat degradation on the abundance, richness and diversity of raptors across Neotropical biomes

The presence of superabundant prey resources can influence the abundance and distribution of raptors. To investigate how an unintentionally provided prey superabundance may affect the regional distribution of raptors, we extracted data on Red-tailed Hawk (Buteo jamaicensis) and Turkey Vulture (Cathartes aura) observations from eBird (ebird.org) for a 3.3-km2 region surrounding a Ring-necked Pheasant (Phasianus colchicus) production facility and 1.6-ha composting facility in Ithaca, New York, USA. Then we extracted data from a 3990-km2 block centered on this “game farm/compost” region. On average, hawk counts were greater near the game farm/compost region (mean = 4.28 ± 3.09 SE) than in the surrounding buffer (mean = 0.14 ± 0.12 SE), with numbers increasing through the fall and winter. Similarly, more vultures were counted near the game farm/compost region (mean = 8.4 ± 4.9 SE) than in the surrounding buffer (mean = 0.24 ± 0.29 SE), with numbers peaking during late summer and early fall. To examine fine-scale patterns at the game farm/compost region, we conducted point counts at least three times per week from September 2019 through January 2020. The mean number of hawks per point count was 7.57 (±0.97 SE); numbers increased through the winter, with greater numbers detected later in the day and at lower temperatures. Hawk counts were not correlated with precipitation or snow cover. The mean number of vultures was 16.2 (±2.05 SE), with the greatest counts in February and during the warmest days; fewer vultures were detected during precipitation and during snow cover. This research demonstrates that an unintentionally provided, superabundant prey resource can influence raptor abundance and distribution.

El monitoreo biológico es esencial para comprender la dinámica poblacional, los procesos ecológicos y los problemas emergentes. En este estudio determinamos la riqueza y abundancia de las rapaces diurnas en el Parque Estatal Cañón de Fernández en Durango, México. Detectamos 11 especies, cinco de éstas están bajo alguna categoría de riesgo según la Norma Oficial Mexicana 059-2010: gavilán pecho canela (Accipiter striatus), gavilán de cooper (A. cooperii), aguililla negra menor (Buteogallus anthracinus), aguililla rojinegra (Parabuteo unicinctus) y aguililla pecho rojo (Buteo lineatus). Las especies más abundantes fueron Coragyps atratus, Cathartes aura y Buteo jamaicensis. El hábitat donde obtuvimos más registros fue el bosque de galería. Las rapaces del área ven amenazada su conservación por la pérdida de hábitat, cacería y electrocución.

The black-tailed prairie dog (Cynomys ludovicianus) is a burrowing rodent native to the Great Plains currently experiencing large population declines. It is debated whether prairie dogs are keystone species; however, areas with prairie dogs have higher levels of biodiversity and presumably increased biotic interactions. The goal of this study is to quantify the importance of black-tailed prairie dogs, hereafter prairie dog, by comparing abundance and diversity of raptors and small mammals on prairie dog (PD) and non-prairie dog (NON) inhabited prairie. A significant difference was detected between the two treatments (PD and NON) in the number of raptors counts; the PD treatment observed a greater abundance of individuals (n = 192) in contrast to the NON treatment (n = 115). Small mammal richness was low with only the following species detected on each treatment; 2 species (Onychomys leucogaster and Ictidomys tridecemlineatus) on the PD treatment and 5 species (Chaetodipus hispidus, Onychomys leucogaster, Perognathus flavus, Peromyscus maniculatus, and Reithrodontomys montanus) on the NON treatment. Although I did not detect abundance or all species caught in both treatments, other studies have reported higher abundances of small mammals, including Onychomys leucogaster, on prairie dog inhabited land. These data have the potential to influence prairie dog conservation efforts, as well as our knowledge of other vertebrate prairie-specialist species. Species in need of conservation, including ferruginous hawk (Buteo regalis) and burrowing owl (Athene cunicularia), rely on prairie dogs for food, shelter, or nesting sites. These species and others will be forced elsewhere as prairie dog distribution continues to decrease, and might be pushed out of their historical distribution, or towards extinction. It is essential for landowners and agencies to understand the complex ecological associations occurring on the prairie, and realize the black-tailed prairie dog is a “Species of Greatest Concern” in Kansas.

The El Niño Southern Oscillation (ENSO) phenomenon is responsible for important physical and biogeochemical anomalies in the Northeastern Pacific Ocean. The event of 1997-98 has been one of the most intense in the last decades and it had large implications for the waters off Baja California (BC) Peninsula with a pronounced warm sea surface temperature (SST) anomaly adjacent to the coast. Downscaling of reanalysis products was carried out using a mesoscale-resolving numerical ocean model to reproduce the regional SST anomalies. The nested model has a 9 km horizontal resolution that extend from Cabo Corrientes to Point Conception. A downscaling experiment that computes surface fluxes online with bulk formulae achieves a better representation of the event than a version with prescribed surface fluxes. The nested system improves the representation of the large scale warming and the localized SST anomaly adjacent to BC Peninsula compared to the reanalysis product. A sensitivity analysis shows that air temperature and to a lesser extent wind stress anomalies are the primary drivers of the formation of BC temperature anomaly. The warm air-temperature anomalies advect from the near-equatorial regions and the central north Pacific and is associated with sea-level pressure anomalies in the synoptic-scale atmospheric circulation. This regional warm pool has a pronounced signature on sea level anomaly in agreement with observations, which may have implications for biogeochemistry.

Spatial and temporal evolution of basalts and magnesian andesites (“bajaites”) from Baja California, Mexico: the role of slab melts

The fall and spring migration routes of numerous raptor species converge in the Rio Grande Plains ecoregion of Texas resulting in a high seasonal diversity and abundance of raptors. Raptors are believed to be an important source of mortality for northern bobwhite (Colinus virginianus). Because of the economic importance of bobwhites and the high concentration of raptors in south Texas, we investigated the relationship between bobwhite mortality and raptor abundance. Our objectives were to document raptor diversity and abundance, correlate bobwhite mortality with raptor abundance, and correlate ambient temperature with raptor abundance.We monitored radiomarked bobwhites (n = 164) biweekly during September–February 2000–01 in Brooks County, Texas. We conducted raptor surveys bimonthly during October–February 2000–01 between 1100 and 1500 hours along a 24-km road. We documented a total of 96 bobwhite mortalities. Raptors accounted for 16 % of the mortalities, with 43% by mammals, 13% unknown predator, and 28% hunter. We observed a total of 310 raptors, representing 15 identified species. Red-tailed hawk (Buteo jamaicensis) and white-tailed hawk (Buteo albicaudatus) comprised a large percentage (38%) of the raptors observed. A weak correlation (r = - 0.11) existed between raptor abundance and total bobwhite mortality. A stronger correlation (r = 0.86) existed between Accipter abundance and raptor depredation of bobwhites. We detected a relatively strong negative correlation (r = -0.65) between raptor abundance and ambient temperature. Our limited data suggest that general raptor abundance may not be a strong indicator of actual bobwhite mortality, and that it may be erroneous to infer that a high abundance of raptors results in a high mortality of bobwhites. Understanding the relationship between bobwhite and raptors will involve determining species-specific migration timing and numbers.

Ants account for 30% of terrestrial biomass and are highly sensitive to environmental variables. Present study investigated the effect of altitude (400-900 m) and vegetation type (mixed woodland and pine plantations in Hanthana forest) on litter ants. Two transects were laid at each of the five 100 m elevation levels. For hand-picking and litter extraction of ants, 1 m2 plots were laid at every 20 m intervals along the two sides of each transect. A total of 8689 ants in 9 subfamilies 32 genera and 56 morpho-species were collected. Subfamily Myrmicinae had the highest number of genera (15) and species (26 spp.). Genus Pheidole was represented by the highest number of species (5 spp.) while Solenopsis sp. 1 was the most widely distributed and abundant (6420 individuals) species. The mixed woodlands, regardless of elevation, were richer in ant species than pine plantations. Permutation test (ρ=0.30, P=3%) revealed a weak relationship between ant assemblages and environmental variables. Findings indicated that the difference in litter ant species assemblages and diversity in Hanthana Forest is possibly due to differences in vegetation types rather than altitude.

To date, the knowledge of bee diversity in the Baja California Peninsula has primarily relied on large, sporadic expeditions from the first half of the 20th century. To address the knowledge gaps, we conducted extensive fieldwork from 2019 to 2023, visited entomological collections in Mexico and USA, and accessed digital databases and community science platforms to compile records. As a result of our field surveys, we identified 521 morphospecies, with 350 recognized as valid species, including 96 new records for the Baja California Peninsula and 68 new findings for Mexico, including the rediscovery of Megachile seducta Mitchell, 1934, ranked as possibly extinct. Additionally, museum visits added 24 new species records for the peninsula, including 12 new to Mexico. Integrating the new and existing records results in a comprehensive checklist that documents 728 species for the peninsula, 613 for Baja California, and 300 for Baja California Sur. Notably, 62 species are endemic to the peninsula, of which 22 are only found in Baja California, and 23 in Baja California Sur. Our findings show a greater bee diversity in northern latitudes, with a sharp decrease to the central and southern peninsula, which corresponds to the geographic distribution of the records. This supports the premise that the Baja California peninsula remains an unexplored area and highlights the importance of conducting studies like the one presented here.

Tropical cyclones (TCs) are large-scale natural disturbances that generate strong winds and heavy rainfall, impacting coastal and inland environments. TCs also influence biogeochemical and hydrological cycles controlling aquatic primary productivity in tropical and subtropical coastal ecosystems. We assessed TC landfall activity and identified sites along the Mexican east and west coasts with high frequency in the period 1970–2010 and evaluated TCs with significant precipitation. Changes in chlorophyll-a (Chl-a) concentrations before and after storm impacts were estimated using remotely sensed ocean color. There were 1,065 named TCs with a wide diversity in tracks. Three states with the highest number of landfalls were identified: Baja California Sur and Sinaloa on the west coast and Quintana Roo on the east coast. While a relative increase in Chl-a values following TC landfalls in the Baja California and Yucatan Peninsula regions appeared to be strongly linked to TC strength, the intensity of precipitation, the spatial scales of the two peninsulas, and the relative movement of TCs appeared to have contributed to Chl-a variability. Satellite estimates of Chl-a in the nearshore coastal waters following TC passage were likely enhanced by coastal morphology and water discharge along with constituents such as suspended particulate, colored dissolved organic matter and nutrients from rivers, tributaries, and groundwater.

Specimens of Porites californica contained in the sediments of upper Pleistocene, +12-m marine terrace deposits developed on the east coast of the Baja California (Mexico) peninsula at Mulege have yielded /sup 239/Th//sup 234/U dates of 124 +/- 5 and 144 +/- 7 ka (+/- 1 sigma). These dates can be assigned to the well-documented late Pleistocene oxygen-isotope stage 5e high sea stand. Differences between the eustatic and present elevations of this terrace indicate average uplift rates since terrace formation of approximately 4 to 5 cm/1000 yr, indicating a relative stability and lack of major vertical deformation since the late Pleistocene. This terrace in the Mulege area can now be correlated with other marine terraces throughout the Baja California peninsula and southern California.

Red-tailed Hawks (Buteo jamaicensis) occasionally scavenge, yet the circumstances that can prompt carrion consumption are still unclear. The first record of a Red-tailed Hawk consuming human carrion was captured during Winter Storm Uri by camera trap imagery collected by the Forensic Anthropology Center at Texas State University in central Texas, USA. The Red-tailed Hawk was observed scavenging on human remains on 16 February 2021 during a period of record low temperature (as low as −16.7°C) and high snow cover (up to ∼18 cm) for Texas, which suggests that facultative scavenging may be influenced by temperature and snow cover. Additionally, as the Red-tailed Hawk arrived at the cadaver site (n = 13 times on one day), it frequently displaced the larger Black Vultures (Coragyps atratus) and Turkey Vultures (Cathartes aura) that were feeding, although in one case an arriving Crested Caracara (Caracara plancus) displaced the Red-tailed Hawk (and other scavengers). When the Red-tailed Hawk departed from the site (n = 13 times on one day), more scavengers of other species returned. The study yielded novel observations and can encourage future researchers to evaluate the dynamics that influence facultative scavenging by Red-tailed Hawks, as well as the factors that influence scavenger dominance hierarchies.

An investigation of terrestrial bryophyte species diversity and community structure along an altitudinal gradient from 2,001 to 4,221 m a.s.l. in Gongga Mountain in Sichuan, China was carried out in June 2010. Factors which might affect bryophyte species composition and diversity, including climate, elevation, slope, depth of litter, vegetation type, soil pH and soil Eh, were examined to understand the altitudinal feature of bryophyte distribution. A total of 14 representative elevations were chosen along an altitudinal gradient, with study sites at each elevation chosen according to habitat type (forests, grasslands) and accessibility. At each elevation, three 100 m × 2 m transects that are 50 m apart were set along the contour line, and three 50 cm × 50 cm quadrats were set along each transect at an interval of 30 m. Species diversity, cover, biomass, and thickness of terrestrial bryophytes were examined. A total of 165 species, including 42 liverworts and 123 mosses, are recorded in Gongga mountain. Ground bryophyte species richness does not show any clear elevation trend. The terrestrial bryophyte cover increases with elevation. The terrestrial bryophyte biomass and thickness display a clear humped relationship with the elevation, with the maximum around 3,758 m. At this altitude, biomass is 700.3 g m−2 and the maximum thickness is 8 cm. Bryophyte distribution is primarily associated with the depth of litter, the air temperature and the precipitation. Further studies are necessary to include other epiphytes types and vascular vegetation in a larger altitudinal range.

Squash leaf curl (SLC) disease causes serious damage in a great diversity of horticultural crops worldwide and is due to infection by different ssDNA bipartite begomoviruses (Family Geminiviridae). Symptoms of leaf yellowing, stunting and curling have been observed in squash crops in the southern region of the Baja California (BC) Peninsula in the northwestern region of Mexico for at least a decade. The damage estimated for all localities showed disease incidence of 73.3% to 97.7% and severity of 49%. Infected plants were collected in three localities in addition to adult whiteflies for species determination. Squash leaf curl virus (SLCuV) was detected in both infected plants and whiteflies by PCR using specific primers that amplified a 601 bp fragment. The full-length DNA-A sequence was 99.1% identical to sequences in GenBank. Phylogenetic studies using the core CP region showed that the BC isolate grouped within a well-defined clade together with SLCuV from the Mediterranean Middle East and USA. The molecular analysis in individual adult whiteflies determined that all populations belonged to Bemisia tabaci (MEAM1) (biotype B) species. No evidence of the Mediterranean (MED) species (biotype Q) was found. The SLC disease has prevailed in squash in the region in several growing cycles and in geographically separated localities. To the best of our knowledge, this is the first report of SLCuV associated with squash plants in BCS, Mexico.