Quercus Emoryi Research Articles

Feeding Ecology of Hummingbirds in the Highlands of the Chisos Mountains, Texas

-The feeding habits of three species of hummingbirds were examined during the summer of 1975 in the highlands of the Chisos Mountains, Big Bend National Park, Texas. The Blue-throated Hummingbird (Lampornis clemenciae), the Broad-tailed Hummingbird (Selasphorus platycercus) and the Rufous Hummingbird (S. rufus) were common in the study area, the first occupying the mesic Cypress-Pine-Oak Association and the other two species inhabiting the Pinyon-Juniper-Oak Woodland. Blue-throated Hummingbirds were almost exclusively insectivorous prior to the flowering of mountain sage (Salvia regla), after which their diet began to include its nectar. Males fed outside their territories in the morning at nectar sources in the woodland. Selasphorus hummingbirds overlapped extensively in diet. S. platycercus was common prior to the full flowering of sage, and migrating S. rufus entered the area later, when the sage was in bloom. Males of both species typically established territories around large patches of the sage and open areas while females were relegated to smaller Salvia stands in the woodlands. Such a pattern is apparently maintained by the aggressiveness of the dominant males. Recent examinations of tropical nectarivorous guilds (Feinsinger 1976, Feinsinger and Colwell 1978) have shown that such communities are organized about the distribution of nectar resources. Niche differences among tropical hummingbirds may result from aggression (Wolf 1970, Lyon 1976, Wolf et al. 1976), different foraging patterns (Linhart 1973, Feinsinger 1976), microhabitat selection (Stiles and Wolf 1970), or the exploitation of specific resources by highly specialized species (Snow and Snow 1972). Far fewer hummingbird species inhabit temperate areas than the tropics, and most species are migratory. North American hummingbirds differ from one another ecologically in the same ways as their tropical counterparts. These differences include habitat selection (Pitelka 1951, Lyon 1973, Yeaton and Laughrin 1976), spatial distribution of individuals through territoriality (Pitelka 1942, Cody 1968), and variations in foraging patterns (Feinsinger and Chaplin 1975, Yeaton and Laughrin 1976). We examined the feeding ecology of three interacting hummingbird species with emphasis on their habitat partitioning and timing. We hypothesized that these characteristics would be important to the organization of a nectarivore guild where nectar sources are uncommon. Such conditions appear to occur in the highlands of the Chisos Mountains during the summer. STUDY AREA AND METHODS Data were obtained in the Chisos Mountains (29'15', 103'18') of Big Bend National Park, Brewster Co., Texas during the summer of 1975. The study area was located in Boot Canyon (2,072 m) and centered in two highland plant associations: the Cypress-Pine-Oak Association and the Pinyon-Juniper-Oak Woodland (Wauer 1973). We also examined open areas located within Boot Canyon because they contained patches of nectar-producing flowers and were often visited by the hummingbirds. The Cypress-Pine-Oak Association (henceforth woodland) occurs in the most mesic sections of the Chisos highlands, Pine and Boot canyons, where annual rainfall may exceed 500 mm (Wauer 1973). In the study area, this association occupies a narrow band along Boot Creek and is less diverse than the other woodland association. Arizona cypress (Cupressus Arizonica), pifion pine (Pinus cembroides) and Graves oak (Quercus gravesii) predominate. The Pinyon-JuniperOak Woodland (henceforth juniper woodland) is the most common plant association in the Chisos Mountains and in our study area. Typically, it contains pifion pine, emory oak (Q. emoryi), Graves oak and Mexican drooping (Juniperus flaccida), which can be found on north-facing slopes from 1,650 m to 2,300 m. Within Boot Canyon, the woodland adjoins the cypress woodland. Plant species diversity is greatest in the few open or exposed areas along upper Boot Creek, where herbaceous growth is abundant. Nectar sources were most plentiful in these areas.

Ecological Relationships between Mule Deer and White‐Tailed Deer in Southeastern Arizona

Niche relationships between the desert mule deer (Odocoileus hemionus crooki) and Coues white—tailed deer (Odocoileus virginianus couesi) were studied in the San Cayetano and Dos Cabezas mountains in southeastern Arizona from September 1969 to March 1972. Walk transects were established on the study areas on which deer were observed. Altitude, slope exposure, and habitat selection were used to describe distributional patterns of the two species. Food habits were studied by analyzing fecal samples microscopically for epidermal fragments of important forage plants. Behavioral interaction between mule deer and white—tailed deer, browse utilization on Cercocarpos breviflorus, and recruitment were also investigated. Spatial distributions according to altitude and slope exposure indicated that a 'buffer' zone existed between populations of mule deer and white—tailed deer in the San Cayetano Mountains. Mule deer were associated with fewer vegetational types than white—tailed deer on this study area; Prosopis juliflora and Fouquieria splendens were indicative of mule deer habitat. White—tailed deer utilized a greater diversity of vegetational types in the San Cayetanos and did not appear to be associated with any particular plant species, although Quercus oblongifolia, Dasylirion wheeleri, and Eysenharditia polystachya were important. The most important forage plants for white—tailed deer in the San Cayetano Mountains were E. polystachya, Eriogonum wrightii, Krameria parvifolia, and Fendlera rupicola. Similarly, the primary food items of mule deer were E. polystachya, Calliandra eriophylla, and K. parvifolia. There was much overlap in food preferences of mule deer and white—tailed deer (55% to 67% seasonally) particularly on E. polystachya and K. parvifolia. Populations of mule deer and white—tailed deer were sympatric in the Dos Cabezas Mountains; the coefficients of association were highly positive. There was also a great similarity in habitat selection between the two species. Both species were associated with those habitat types dominated by Quercus emoryi, Juniperus deppeana, C. breviflorus, Quercus gambelii, Nolina microcarpa, Symphoricarpos ereophilus, and/or Bouteloua spp. White—tailed deer displayed a greater preference for the Quercus Symphoricarpos and Quercus—Cercocarpus habitat types than mule deer, whereas Juniperus—Cercocarpus habitats were preferred more by mule deer. Food habits of mule deer and white—tailed deer were very similar: all plant species important to white—tailed deer were also important to mule deer. The most frequent forage plants, in order of importance, were C. breviflorus, E. wrightii, J. deppeana, and Q. gambelii. Recruitment to the population was higher for mule deer than for white—tailed deer. Utilization of the annual leader growth on the key browse plant (C. breviflorus) was extremely high. Mule deer were dominant over white—tailed deer in all behavioral interactions observed during the study. In half of these instances, mule deer displayed aggressive threat in asserting their dominance; the rest were of a passive nature. The low coefficients of distributional overlap and high indices of overlap in food habits for the San Cayetano Mountains lead us to conclude that mule deer and white—tailed deer competitively exclude each other. The high overlap in spatial distributions, habitat selection, and food habits coupled with the high utilization of the key forage plant (C. breviflorus) in the Dos Cabezas Mountains during the winter months lead to the conclusion that direct competition between the two species probably was occurring during that time. This direct competition can be explained on the basis that it is a temporary phenomenon. It is hypothesized that the factors that have brought mule deer and white—tailed deer into direct competition in this area have been vegetational changes, livestock overgrazing and/or range fire suppression.

Emory Oak (Quercus emoryi) Litter Phenolics as Environmental Hazards for Aquatic Animals in Southeastern Arizona

Emory Oak (Quercus emoryi) Litter Phenolics as Environmental Hazards for Aquatic Animals in Southeastern Arizona

Reproduction in the Audubon Cottontail in Arizona

The Audubon cottontail, Sylvilagus audubonii arizonae , is a common mammal of the desert regions of southern Arizona. It is found from the lowest elevations in the state, about 100 feet above sea level in southwestern Arizona, to an elevation of about 4,000 feet above sea level on the slopes of the desert mountain ranges in southeastern Arizona. This cottontail is found in the vegetational types classified by Nichol (1943) as: Creosote bush–atriplex desert, characterized by Larrea tridentata and Atriplex canescens ; Palo verde–cacti desert, where palo verde, Cercidium microphyllum , and sahuaro, Carnegiea gigantea , are the dominant larger plants; and Desert-grassland, characterized by mesquite, Prosopis juliflora , yucca, Yucca elata , and a great variety of grasses. It is also found in several types of chaparral country where such species as scrub oak, Quercos turbinella , smooth sumac, Rhus ovata , jojoba, Simmondsia chinensis , and a variety of other shrubs form a dense cover. In some parts of southeastern Arizona, at about 4,000 feet elevation, it is found in the oak woodland where Mexican blue oak, Quercus oblongifolia , Emory oak, Q. Emoryi , beargrass, Nolina microcarpa , skunk bush, Rhus trilo-bata , and manzanita, Arctostaphylos pringlei , are characteristic larger plants. In this vegetational type the Audubon cottontail is replaced by a larger species of cottontail, S. floridanus holzneri , which extends its range up into the forest of yellow pine, Pinus ponderosa . This species of cottontail sometimes occurs with audubonii in the lower fringe of the oak woodland. The published literature on the desert cottontail is fragmentary. In late 1951 I began a study to determine the breeding season and litter size of the desert cottontail and to gather miscellaneous items on its life history. From December, 1951, to September, 1955, I collected 407 …