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Flowering and fruiting phenology of Acacia berlandieri, A. minuata, A. rigidula, A. schaffneri, and Chloroleucon ebano were studied at 3 sites in the Lower Rio Grande Valley of Texas from July 1998 through August 1999. Severe drought conditions prevailed for the 6 months preceding this study, and rainfall was 20% lower during the study than the long-term mean. Acacia berlandieri had the longest flowering period (5 months); each of the other 3 Acacia species flowered for 3 months. All of the Acacia species flowered in winter or spring (at relatively low temperatures and increasing photoperiod). Peak flowering occurred in February in A. berlandieri, A. rigidula, and A. schaffneri. Peak flowering occurred in March in Acacia minuata. There was significant variation in percent flowering among months within A. minuata, A. rigidula, and A. schaffneri. Significant variation in percent flowering occurred among species during February, March, and April. Chloroleucon ebano flowered in only 1 month (September) following heavy rain. All of the Acacia species dropped their fruit before new fruit were developed, but C. ebano had mature fruit from the previous year and developing fruit on the same individuals. Few shrubs or trees of any species had fruit from November through April. There were significant differences in percentage of individuals with mature fruit among species in most months, and there was significant variation in percentage of shrubs and trees with mature fruit among sites within species. Acacia minuata and A. schaffneri showed significant positive correlations between percent fruiting and photoperiod and temperature. We suggest C. ebano flowers at higher temperatures than the Acacia species and at peak or declining photoperiod rather than during increasing photoperiod.
The freshwater unionoid mussel Popenaias popeii is restricted to river drainages of the Gulf of Mexico in southwestern North America. Previously, this species has been classified as both a short-term and long-term larval brooder based on limited data. Histological analysis of gonadal tissue from specimens collected in New Mexico indicated gonochoric individuals; hermaphroditism was not observed in any specimens. Although male and female gametes were present for almost the entire year, gonadal activity appeared lowest in October and November, when tissue recovery and reorganization were more evident than gametogenesis. Gravid females were observed from March through August, with all stages of embryos and larvae present on every sampling date during this period. Non-gravid females always were present, even if they contained active gonads. Contrary to previous reports, P. popeii is considered an asynchronous short-term brooder with an extended period (late winter to mid-summer) of oviposition. A small percentage of gravid females used posterior portions of inner demibranchs as marsupia. This character suggests that inner demibranchs might function in a facultative capacity as an overflow reservoir for larvae unable to fit into full marsupia of the specialized outer demibranchs.
We examined seasonal and spatial distribution of all life stages of the diminutive cyclopoid copepod Tropocyclops prasinus mexicanus in 2 years in the nearly thermally constant environment of Montezuma Well, Arizona, USA. Although annual temperatures remained relatively constant (21 ± 4°C), densities of T. prasinus mexicanus displayed a bimodal pattern, with highest densities during the summer and winter. Also, the vertical water column was nearly homeothermal, but all life stages avoided the top 2 m of the water column during clear summer days and utilized this stratum during the winter when light was reduced. Females within the population were egg-bearing throughout the entire year, which led to high annual mean densities (>200 animals/L). Mean annual biomass of T. prasinus mexicanus was estimated at ≥50 µg/L.
We surveyed the amphibians and reptiles of the Whetstone Mountains in southeastern Arizona using a combination of intensive small-area plots, extensive walking searches, trap arrays, road-driving, spot checks, and review of previous records. We found 43 species within the National Forest boundary and within 1 mile of the boundary. Composition of the herpetofauna is typically Madrean and included 5 anuran, 2 turtle, 21 lizard, and 14 snake species. Previous records from the study area documented only 15 species. Quantitative results of intensive and extensive searches provide additional baseline data that could be used for future monitoring efforts.
White-faced ibises (Plegadis chihi) nesting in Arizona in 2000 exhibited extreme eggshell thinning and possible reproductive failure associated with high egg residues of DDE. A small colony of approximately 75 pairs nested relatively late in the season, and egg laying occurred from about June 15 to June 29. Average clutch size in 19 marked nests was 2.5, which was low compared to that reported for most other ibis populations. Hatching success was 43% (13 of 30 eggs remaining in active nests). The geometric mean DDE egg residue (2.23 µg/g wet weight) was similar to those reported in other ibis populations where DDE-induced shell thinning adversely affected reproductive success. Two of 16 eggs collected from marked nests had a flexible shell that easily indented with slight finger pressure. Overall mean eggshell thickness of 23 eggs was 0.264 mm, 15% thinner than shells of museum eggs collected before the widespread use of DDT. Only 1 of 23 eggs contained mercury at potentially harmful concentrations (>2.5 µg/g dry weight). Selenium in 74% of the eggs exceeded background concentrations (<3.0 µg/g dry weight), but none exceeded the toxic threshold (>8.0 µg/g dry weight).
Data from neck-band observations were used to determine breeding-ground affiliation, period of use, and winter movement patterns of greater white-fronted geese (Anser albifrons frontalis) observed in the Winchester Lakes region of northwestern Texas. Over 1,265 observations of nearly 800 individual neck-banded geese (3.2% of all neck-banded white-fronted geese in North America) were recorded in the region from 1988 through 1996. More than 4,200 observations of these individuals were recorded throughout North America. Observations peaked in November and February, indicating that the Winchester Lakes region is a migratory staging area for white-fronted geese. Only 6% of the birds in this region remained throughout the winter. Most birds staging in the Winchester Lakes region wintered in the rice prairies of coastal Texas and interior Mexico. Eighty-eight percent of the neck-banded geese were from the western portion of the midcontinent population of greater white-fronted geese, primarily representing Interior-Northwest Alaska, Yukon, and Anderson River breeding populations. These breeding populations are characterized by declining trends in population size and survival rates. The status (e.g., population trends, productivity, survival) of these breeding populations must be considered when managing birds in the Winchester Lakes region.
In central New Mexico, breeding populations of Bewick's wren (Thryomanes bewickii) recently colonized riparian forests of the Middle Rio Grande and have increased rapidly to become the sixth most abundant breeding bird species in bosque habitats. In 1997–1998, I studied the potential roles that cottonwood forest succession and alien plant species invasion might have had in facilitating this change in the distribution of the wren. Habitat preference and nest cavity limitation were examined at 12 sites near Albuquerque, New Mexico. Bewick's wrens nested only in native tree species, especially large cottonwoods (Populus deltoides). Territories defended by males had greater coverage of mature cottonwood and lower amounts of open, early successional habitats than areas not occupied by wrens. Analysis of wren abundance data from 70 sites throughout the Middle Rio Grande found wren abundance to be highest at sites dominated by cottonwoods, especially at sites having alien salt cedar (Tamarix chinensis) understories. However, at sites dominated by alien plant species, Bewick's wren abundance was low. When the number of suitable nest cavities was experimentally increased through provision of nest boxes, wren abundance increased and their distribution expanded, suggesting nest-site availability was a limiting factor in this population. The mature, even-aged cottonwood populations established around 1950 currently provide suitable conditions for breeding Bewick's wrens. However, the remarkable speed at which this species has increased suggests that other population factors might have affected its distribution and abundance.
From mid-May through July, 1992 to 1998, we searched for black-headed grosbeak (Pheucticus melanocephalus) nests in riparian and Gambel oak (Quercus gambelii) pastures in La Plata County, Colorado. Twenty-six nests (63%) were successful in fledging at least 1 young, and 15 nests (37%) failed because of predation. The mean number of grosbeaks hatched and fledged per nest did not differ between riparian pastures and oak pastures. The proportion of nests depredated in riparian pastures (10/25, 40%) and oak pastures (5/17, 29%) did not differ significantly. Mortality rates did not differ between habitats during the incubation stage (riparian: 0.056 nests/day; oak: 0.046 nests/day) or during the nestling stage (riparian: 0.011 nests/day; oak: 0.0 nests/day). Mean nest height did not differ between depredated nests and successful nests in either riparian pastures or oak pastures.
The ferruginous pygmy-owl (Glaucidium brasilianum) has a wide geographic range centered on the Neotropics. At the northern edge of its distribution, 1 subspecies, the cactus ferruginous pygmy-owl (G. b. cactorum) reaches Texas and Arizona. However, in both states it has experienced important range and population declines. In Arizona in particular, the owl was originally described as common along several rivers and streams. There were many specimens collected and the subspecies was often mentioned in ornithological publications. Today, the cactus ferruginous pygmy-owl is found in low numbers in Arizona, and since 1997, it has been federally listed as endangered in that state. Determining when and why this owl began to decline sharply in numbers and range in Arizona has proven difficult. In retrospect, inadequate information apparently led to a lapse of several decades between the actual change in the population status and its recognition by ornithologists. Here we examine the most complete list of cactus ferruginous pygmy-owl records to date, including unpublished specimen collection records. Collectively, these records strongly suggest that a severe downward population trend began as early as the 1920s, not the 1950s, as is commonly reported in the literature. Using our revised time frame and the history of the cactus ferruginous pygmy-owl in Texas, we also examine possible reasons for the occurrence of the decline. The best information available might indicate a combination of biogeographic and human-related factors.
A right femur (KCSP-128) from late Pleistocene deposits (ca. 36,210 yr B.P.; Rancholabrean) in Kartchner Caverns State Park, southeastern Arizona, is identified as the larger-than-modern roadrunner, Geococcyx californianus conklingi. This large form is best known from late Pleistocene localities in New Mexico and Nuevo Leon, as well as from assumed mixed late Pleistocene/Holocene deposits from New Mexico, Texas, and Chihuahua. It has never been reported from Arizona. Fossils of the modern-sized form, Geococcyx californianus californianus, have been reported from late Pleistocene localities in California and New Mexico, and from mixed late Pleistocene/Holocene deposits in Chihuahua. Comparisons of the Kartchner Caverns specimen to modern G. c. californianus specimens, and to published data of fossil G. c. californianus and G. c. conklingi, indicate KCSP-128 is relatively larger than the G. c. conklingi data and notably larger than G. c. californianus. KCSP-128 is added to the Rancholabrean record as the first late Pleistocene roadrunner reported from Arizona.
High densities of an aridland granivore, Ord's kangaroo rat (Dipodomys ordii), have been documented in floodplain habitats along the Yampa River in northwestern Colorado. Despite a high probability of inundation and attendant high mortality during the spring flood period, the habitat is consistently recolonized. To understand factors that potentially make riparian habitats attractive to D. ordii, we compared density and spatial pattern of seeds, density of a competitor (western harvester ant, Pogonomyrmex occidentalis), and digging energetics within floodplain habitats and between floodplain and adjacent upland habitats. Seed density within the floodplain was greatest in the topographically high (rarely flooded) floodplain and lowest immediately after a spring flood in the topographically low (frequently flooded) floodplain. Seed densities in adjacent upland habitat that never floods were higher than the lowest floodplain habitat. In the low flood-plain prior to flooding, seeds had a clumped spatial pattern, which D. ordii is adept at exploiting; after spring flooding, a more random pattern resulted. Populations of the western harvester ant were low in the floodplain relative to the upland. Digging by D. ordii was energetically less expensive in floodplain areas than in upland areas. Despite the potential for mortality due to annual spring flooding, the combination of less competition from harvester ants and lower energetic costs of digging might promote the use of floodplain habitat by D. ordii.
We examined effects of the exotic fire ant Solenopsis invicta on habitat use by hispid cotton rats (Sigmodon hispidus) and northern pygmy mice (Baiomys taylori) over a 17-month period in an open grassland community in central Texas. We divided the study area into 10 adjacent plots. Five alternating plots were treated with an ant-toxic bait to reduce density of S. invicta. The remaining 5 plots were left untreated. We trapped small mammals monthly and calculated capture per unit effort (CPUE) for each small mammal species in each of 3 treatments (treated, untreated, border) each month. Trap months were partitioned into 2 seasons, summer and winter. Sigmodon hispidus altered habitat use, as indicated by CPUE, in the presence of S. invicta during summer, and B. taylori did not alter habitat use in the presence of fire ants during either season.
Northern grasshopper mice (Onychomys leucogaster) were sampled periodically from June 1977 to November 1986 in the mixed-grass prairie region of north-central Kansas. Necropsies were performed on 175 mice to assess number of pregnancies and litter size for females and testis size for males. Fourteen of 87 females were pregnant with the earliest and latest dates of captures of pregnant females on 22 March and 18 August, respectively. The proportion of pregnant females peaked during May–June. The average number of fetuses was 4.0 (range: 2 to 5), and number of fetuses was correlated positively with body length of the mother. Testes of large males (≥110 mm) increased in size from January to August, and then rapidly regressed through October, whereas smaller males either exhibited a high degree of variability in testes size or had relatively small testes throughout this period. Temporal patterns for pregnancies and testis size suggested that the reproductive cycle for northern grasshopper mice in north-central Kansas was unimodal, and reproductive activity was greatest in late spring to mid-summer.
Kit foxes (Vulpes macrotis) are socially monogamous and live in male-female pairs or small family groups. These small desert foxes are nocturnal and spend the day in an underground den. Mated pairs often shared the same den on the same day. However, on days when they did not share the same den, mated pairs did not occupy dens that were closer together (or farther apart) than expected by chance. Closely related foxes on adjacent home ranges also occasionally shared dens. However, foxes living on adjacent home ranges, even when closely related, also did not occupy dens that were closer together or farther apart than expected by chance.
The original descriptions of the bats Sturnira lilium lilium and S. l. parvidens are general and fragmented. Therefore, we provide standardized redescriptions of the type specimens, as well as external and cranial measurements, to clarify differences between the types and to provide information that will allow for better recognition of specimens of S. l. parvidens and S. l. lilium. The skulls of both type specimens are partially broken and incomplete. In S. l. parvidens the skull and braincase are smaller than in S. l. lilium, and the inner upper incisors are bilobed with the internal lobule larger, while in S. l. lilium the upper incisors are pointed with a single lobe. The measurements of the forearm, tibia, maxillary toothrow, greatest breadth across the upper molars, least postorbital breadth, and greatest breadth across the canines are smaller in the specimen of S. l. parvidens.
More than 60 fossil achenes of Eleofimbris svensonii (Cyperaceae) were recovered from strata in Scott County, Kansas tentatively assigned to the late Miocene Ash Hollow Formation. This collection extends the temporal range of the taxon in this formation more than 130 km west and 20 km south and more than doubles the number of specimens available for study.
Previously, no Odonata have been reported from 44 Texas counties (17%), mainly from the northern Panhandle. Adult dragonflies and damselflies collected since September of 1999 are reported from 24 sites in 14 counties throughout the Texas Panhandle. A total of 35 species is discussed, representing 73 new county records and 4 new state records. First records of Odonata are included for 6 counties.
A nest of the honey ant (Myrmecocystus mendax), excavated in October 2000 at an elevation of 5,500 ft near Portal, Arizona, contained 2,797 ants: 1,991 workers, 18 callows, 29 winged queens, 169 winged males, and 590 swollen ants. The swollen ants varied in weight from 0.017 to 0.608 g and had gasters ranging in color from light to dark amber. The nest also contained numerous larvae, 6 pupae, the ant-loving cricket (Myrmecophilia), a staphylinid larva, collembolans, and mites (Gymnolaelaps). The 36 chambers of the nest radiated 10 to 55 cm from the entrance and ranged in depth from 11 to 105 cm.
In the 1960s, the gynogenetic fish Poecilia formosa was at least 4.2 times as abundant as its sexual host P. latipinna in habitats in and near Brownsville, Texas. That is consistent with theoretical expectations. In winter 1998–1999, both species were found at 10 sampled ponds and ditches in Brownsville. At 7 of the sites, P. latipinna was more abundant in samples than was P. formosa, while the reverse was true at 3 sites. At all but 1 of the locations, the hypothesis that the gynogen was 4.2 times as abundant as its host was rejected on Chi-square criteria. Whether environmental changes since the historical data were collected in the 1960s have been sufficient to change the relationship between the 2 species, or whether the 2 species vary in relative numbers due to their ongoing population interaction, as suggested by recent experimental evidence, is not yet known.
Percina macrolepida has previously been reported from 5 localities in the western portion of the Arkansas River basin in Colorado, New Mexico, and Oklahoma, presumably as a result of introductions. Examination of museum specimens and field sampling in 2000–2001 revealed that P. macrolepida is more widely distributed in the Arkansas River drainage than previously known. We documented the first records of P. macrolepida from the Arkansas River in Arkansas, where it occurs in large numbers throughout the McClellan-Kerr Arkansas River Navigation System. In the Arkansas portion of the Arkansas River, P. macrolepida occurred only in habitats in the main channel, often at the same localities as the morphologically similar P. caprodes. Percina caprodes was the only logperch species found in Arkansas River tributaries or reservoirs on tributaries in Arkansas. Arkansas River basin records for P. macrolepida in Oklahoma are currently known only from the Canadian River drainage, but additional sampling from the Arkansas River main channel in that state could produce new records for this species. It might not be possible to determine whether P. macrolepida is native or introduced in the Arkansas River basin, but it has likely increased in numbers in the Arkansas River in recent decades as a result of the construction of the navigation system.
We determined the fates of artificial and natural bird nests in Conservation Reserve Program (CRP) fields in northeastern Kansas from mid May through early August 1994. The CRP fields had been planted to native grasses in 1988 or 1989. Artificial nests contained Japanese quail (Coturnix japonica) or house sparrow (Passer domesticus) eggs in nest baskets in bunchgrass clumps to simulate nests of dickcissels (Spiza americana), the most common avian species nesting in the CRP fields. Natural dickcissel nests were found by rope dragging and intensive searches of the CRP fields. Losses among 562 artificial nests did not differ by egg type; however, the 9.8% loss of artificial nests was significantly lower than the 70.1% loss-level among 97 natural dickcissel nests in those CRP fields. The daily survival rate for artificial nests was 0.99, significantly more than the 0.92 for natural dickcissel nests. An assessment of nest depredation based on data from artificial nests might not be representative of depredation on natural nests in grasslands.
The seaside sparrow, Ammodramus maritimus, is known to breed only as far south as Nueces and Copano bays, Texas. Systematic point counts conducted in the spring and summer of 1999 on the Boca Chica Tract of the Lower Rio Grande Valley National Wildlife Refuge revealed 3 attempted seaside sparrow nests, seaside sparrow eggshell fragments, and at least 5 seaside sparrows. Presented here is probable evidence of this species breeding near Brownsville, Texas, over 190 km south of its known breeding range.
Along the northern periphery of their range, populations of the hispid cotton rat, Sigmodon hispidus, are vulnerable to major reductions in density and occasional local extinctions as a result of severe winter weather. Between our sampling periods on 3 December 2000 and 14 January 2001, 3 independent winter weather events, in conjunction with the coldest month in the state since 1983, affected central and eastern Oklahoma. We recorded a drastic decline in the population of hispid cotton rats at the Center for Subsurface and Ecological Assessment Research in central Oklahoma following these winter weather events. Densities dropped from 58.6 cotton rats/ha on 3 December 2000 to 1.2 cotton rats/ha on 14 January 2001. Although hispid cotton rat densities were declining before these winter weather events occurred, we attributed the dramatic decrease to severe winter weather and below-normal temperatures. As of 19 November 2001, the population of hispid cotton rats at the site had not recovered. Abundances between January and November 2001 ranged from 0.6 to 2.6 cotton rats/ha compared with a range of 30.1 to 112.5 during the same period in 2000. Additionally, we present evidence of populations of hispid cotton rats being affected at a statewide scale as a result of the weather in December 2000. We suspect that severe winters, such as the events described, might slow the northward advance of hispid cotton rats and serve to indirectly regulate populations along the intermediate and northern fringes of its range.
In 1998, we made an inventory of mammals in the Valle de los Cirios Reserve of the central portion of the state of Baja California, Mexico. New records of Reithrodontomys megalotis were obtained and were collected in 3 years at the same locality. This species is restricted to small marshes within an arid region. The range expanded 230 km to the south.