Jean-Luc E. Cartron

Ground Arthropods as Potential Indicators of Flooding Regime in the Riparian Forest of the Middle Rio Grande, New Mexico

Abstract In 2001 and 2002, we pit trapped arthropods at eight riparian forest sites along the middle Rio Grande, four characterized by flooding in some years (flood sites) and four others where periodic flooding no longer occurs (nonflood sites). All flood sites flooded in 2001 but not in 2002, while nonflood sites never flooded. Arthropod counts and hierarchical cluster analyses of the sites indicated (1) significantly greater abundance of carabid beetles and the isopod Porcellio laevis in 2001 than in 2002; (2) significantly greater carabid beetle abundance at flood sites during each year of the study, with the relative abundance of one carabid species, Calathus opaculus, significantly higher at nonflood sites in 2002; (3) marginally significantly higher (2001) or significantly higher (2002) carabid species richness at flood sites; (4) no obvious response of the other taxa examined (isopods, tenebrionid beetles, and the cricket Gryllus alogus) to flooding regime, although differences in isopod abundance between flood and nonflood sites approached significance in 2001; (5) successful classification of all nonflood sites and three flood sites using the Bray–Curtis Similarity Index and carabid abundance. Overall, our results suggest that carabid beetles are fairly sensitive indicators of hydrologic connectivity between the Rio Grande and its riparian forest, while the other taxa examined are not. With the number of ongoing or planned restoration efforts increasing along the middle Rio Grande, carabids may represent an important tool for monitoring the response of riparian areas to managed flooding.

Avian diversity in a priority area for conservation in North America: the Janos-Casas Grandes Prairie Dog Complex and adjacent habitats in northwestern Mexico

From February 1994 to January 2004, we studied the avifauna of a 25,000-ha area centered on the Janos-Casas Grandes Prairie Dog Complex of Northwestern Chihuahua, Mexico. Avian diversity totalled 227 species, of which 86 (38%) were residents, 78 (35%) winter migrants, 30 (14%) summer migrants, 27 (11%) transients, and 6 (2%) accidental vagrants. Around 84 (38%) species were observed in at least two habitat types, with riparian areas supporting the highest observed diversity of birds (112 species). Of the 143 species observed in only one habitat type, 44 (30%) occurred in riparian areas, 35 (26%) in association with ponds and aquatic vegetation, 28 (20%) in grasslands, 16 (11%) in the oak woodland–grassland ecotone, 12 (9%) in mesquite scrubland, 5 (3%) around human settlements, and 3 (2%) in crop fields. In particular, summer rains influenced the abundance and/or distribution of several species in grasslands such as the long-billed curlew (Numenius americanus). The present study, which was part of a larger effort to document the merits of establishing a large biosphere reserve in the area, confirmed the importance of the prairie dog complex and grasslands to many species of conservation concern, including the threatened mountain plover (Charadrius montanus), a winter resident. With the␣higher-elevation habitats yet to be surveyed, the local diversity of bird species here already places the proposed reserve among the most important protected areas in all of Mexico. The establishment of the reserve is urgently needed, especially for the protection of grasslands and their associated fauna.

PREY OF NESTING FERRUGINOUS HAWKS IN NEW MEXICO

Abstract During June and July 2000, we collected regurgitated pellets and uneaten prey remains at 26 nests occupied by ferruginous hawks (Buteo regalis) in northwestern, western, and central New Mexico. Analysis of remains from all nests yielded a minimum of 260 individual prey from at least 18 vertebrate (13 mammals, 3 birds, and 2 reptiles) and 2 arthropod species. The taxa most frequently represented were Bottas pocket gopher (Thomomys bottae), ground squirrels (Spermophilus), Gunnisons prairie dog (Cynomys gunnisoni), and desert cottontail (Sylvilagus audubonii). Western diamondback rattlesnake (Crotalus atrox) and barn owl (Tyto alba) were recorded for the first time as prey of ferruginous hawks.

CACTUS FERRUGINOUS PYGMY-OWL IN ARIZONA, 1872–1971

Abstract 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.

Ecology and conservation of the cactus ferruginous pygmy-owl in Arizona

This report is the result of a cooperative effort by the Rocky Mountain Research Station and the USDA Forest Service Region 3, with participation by the Arizona Game and Fish Department and the Bureau of Land Management. It assesses the state of knowledge related to the conservation status of the cactus ferruginous pygmy-owl in Arizona. The population decline of this owl has been attributed to the loss of riparian areas before and after the turn of the 20th century. Currently, the cactus ferruginous pygmy-owl is chiefly found in southern Arizona in xeroriparian vegetation and well-structured upland desertscrub. The primary threat to the remaining pygmy-owl population appears to be continued habitat loss due to residential development. Important information gaps exist and prevent a full understanding of the current population status of the owl and its conservation needs.