Implications of Climate Change for Bird Conservation in the Southwestern U.S. under Three Alternative Futures

Future expected changes in climate and human activity threaten many riparian habitats, particularly in the southwestern U.S. Using Maximum Entropy (MaxEnt3.3.3) modeling, we characterized habitat relationships and generated spatial predictions of habitat suitability for the Lucy’s warbler (Oreothlypis luciae), the Southwestern willow flycatcher (Empidonax traillii extimus) and the Western yellow-billed cuckoo (Coccyzus americanus). Our goal was to provide site- and species-specific information that can be used by managers to identify areas for habitat conservation and/or restoration along the Rio Grande in New Mexico. We created models of suitable habitat for each species based on collection and survey samples and climate, biophysical, and vegetation data. We projected habitat suitability under future climates by applying these models to conditions generated from three climate models for 2030, 2060 and 2090. By comparing current and future distributions, we identified how habitats are likely to change as a result of changing climate and the consequences of those changes for these bird species. We also examined whether land ownership of high value sites shifts under changing climate conditions. Habitat suitability models performed well. Biophysical characteristics were more important that climate conditions for predicting habitat suitability with distance to water being the single most important predictor. Climate, though less important, was still influential and led to declines of suitable habitat of more than 60% by 2090. For all species, suitable habitat tended to shrink over time within the study area leaving a few core areas of high importance. Overall, climate changes will increase habitat fragmentation and reduce breeding habitat patch size. The best strategy for conserving bird species within the Rio Grande will include measures to maintain and restore critical habitat refugia. This study provides an example of a presence-only habitat model that can be used to inform the management of species at intermediate scales.     

Context-dependent post-dispersal predation of acorns in a California oak community

Seed dispersal and predation play important roles in plant life history by contributing to recruitment patterns in the landscape. Mast-seeding – extensive synchronized inter-annual variability in seed production – is known to influence the activity of acorn consumers at source trees, but little is known about its effect on post-dispersal predation. We conducted a planting experiment over three years to investigate the relationship between habitat-level post-dispersal predation and landscape-wide acorn production of three sympatric oak species (Quercus spp.). We measured post-dispersal predation in three oak-dominated habitats – savanna (under Q. lobata), forest edge (under Q. agrifolia), and woodland (under Q. douglasii) – as well as in chaparral and open fields. Overall, landscape-level predation was similarly high among study years, averaging 61.4%. Neither species nor mass of planted acorns affected predation. Habitat had a significant effect on post-dispersal predation risk with acorns disappearing most rapidly in chaparral and least rapidly in woodlands. However, a significant interaction between year and habitat (Z = −4.5, P < 0.001) showed that the hierarchy of predation risk among habitats was inconsistent among years. Using annual acorn census data from local populations of each oak species, we found that predation risk in oak-dominated habitats was significantly and positively related to acorn production of the overstory species (Z = −9.53, P = 0.009). Our findings add to growing evidence that seed dispersal, predation, and regeneration are context-dependent on annual variation in community-level seed production, and we discuss the potential consequences of these dynamics on oak recruitment and animal behavior.     

Mexican Jay social group size varies with habitat in northeastern Mexico

ABSTRACT.   We evaluated the hypothesis that social group size in Mexican Jays ( Aphelocoma ultramarina ) varies with habitat structure. We counted the social group size of Mexican Jays over a range of elevations and forest types in a single mountain range in northern Mexico (Sierra El Carmen, Coahuila). Group size increased significantly with elevation, in contrast to a population of Mexican Jays in Arizona that showed no such trend in another study. Among the vegetation variables measured, those relating to size of pines and oaks were especially important in explaining variation in group size. Because acorns and pine nuts are a major part of the diet of Mexican Jays, sites with larger oaks and pines may produce larger nut crops and support larger groups of jays. Elevation did not significantly explain variance in group size after taking vegetation into account. We compared group size and habitat variation across different parts of the geographic range of Mexican Jays. Our analysis indicates that variation of social group size in Mexican Jays is influenced by habitat quality at both local and geographic scales. Detailed studies on habitat structure and demographics of this population are needed to further clarify aspects of habitat quality important to these jays, and the mechanisms by which variation in social structure is maintained.     

Population cytology of the genus Phaulacridium

Twenty seven populations of the grasshopper Phaulacridium marginale were sampled from South Island, New Zealand. An analysis of the chiasma frequency data showed that populations differed significantly for this metric. The populations appeared to fall into two distinct size groups. Morphological measurements confirmed this and a reanalysis of the chiasma frequency data revealed that although the two groups differed significantly for both mean cell chiasma frequency and between cell variances, there was no difference between populations within a group. Analysis of climatological data suggests that the “larger” individuals show different environmental (habitat) preferences from the smaller, which are restricted to one region of South Island. The taxonomic status of Ph. marginale as a single species is called into question.     

Phylogeny, diversity, and species delimitation of the North American Round-Nosed Minnows (Teleostei: Dionda), as inferred from mitochondrial and nuclear DNA sequences

Accurate delimitation of species is a critical first step in protecting biodiversity. Detection of distinct species is especially important for groups of organisms that inhabit sensitive environments subject to recent degradation, such as creeks, springs, and rivers in arid or semi-desert regions. The genus Dionda currently includes six recognized and described species of minnows that live in clear springs and spring-fed creeks of Texas, New Mexico (USA), and northern Mexico, but the boundaries, delimitation, and characterization of species in this genus have not been examined rigorously. The habitats of some of the species in this genus are rapidly deteriorating, and many local populations of Dionda have been extirpated. Considering the increasing concerns over degradation of their habitat, and pending a more detailed morphological revision of the genus, we undertook a molecular survey based on four DNA regions to examine variation over the range of the genus, test species boundaries, and infer phylogenetic relationships within Dionda. Based on analyses of two mitochondrial (cytb and D-loop) and two nuclear (Rag1 and S7) DNA regions from specimens collected throughout the range of Dionda, we identified 12 distinct species in the genus. Formerly synonymized names are available for two of these species, and four other species remain undescribed. We also redefine the known range of six species. The limited distribution of several of the species, coupled with widespread habitat degradation, suggests that many of the species in this genus should be targets for conservation and recovery efforts.     

Dragma hippomanicum IX. A new astragalus (Leguminosae: Astragalanae) from sandstone rim-rock in New Mexico

Astragalus knightii, related to ammophilousA. (sect.Cusickiani)ceramicus Sheld. but adapted to a specialized habitat and reciprocally modified in growth-form, is described from north-central New Mexico, illustrated and discussed.     

Variable helper effects, ecological conditions, and the evolution of cooperative breeding in the acorn woodpecker

The ecological conditions leading to delayed dispersal and helping behavior are generally thought to follow one of two contrasting scenarios: that conditions are stable and predictable, resulting in young being ecologically forced to remain as helpers (extrinsic constraints and the habitat saturation hypothesis), or that conditions are highly variable and unpredictable, leading to the need for helpers to raise young, at least when conditions are poor (intrinsic constraints and the hard life hypothesis). We investigated how variability in ecological conditions influences the degree to which helpers augment breeder fitness in the cooperatively breeding acorn woodpecker (Melanerpes formicivorus), a species in which the acorn crop, territory quality, and prior breeding experience all vary in ways that have important effects on fitness. We found that the relationship between ecological conditions and the probability that birds would remain as helpers was variable but that helpers generally yielded greater fitness benefits when ecological conditions were favorable, rather than unfavorable, for breeding. These results affirm the importance of extrinsic constraints to delayed dispersal and cooperative breeding in this species, despite its dependence on a highly variable and unpredictable acorn crop. Our findings also confirm that helpers can have very different fitness effects, depending on conditions, but that those effects are not necessarily greater when breeding conditions are unfavorable.     

Influence of physiographic and climatic factors on spatial patterns of acorn production in Maryland and Virginia,USA

Aim The aims of this study were to identify the effects physiographic differences have on the spatial synchrony of acorn production within red (Quercus rubra) and white (Quercus alba) oak subgenus groups, to identify climatic factors associated with acorn production patterns, and to assess if and how these relationships vary across a distinct physiographic boundary. Location Maryland and Virginia in the eastern United States. Methods Using data from 36 survey sites in Virginia (1973–2000) and Maryland (1977–2000), we described the spatial synchrony of annual acorn production based on Mantel tests and modified correlograms at three spatial scales: (1) the entire study area, (2) within two ecological regions (mountain and Piedmont), and (3) between these ecoregions. Using climate data obtained from the National Climate Data Centre, we described the relationship between climate and acorn production within each ecological region using linear regression. Results Spatial synchrony in the white oak group acorn production was strong among sites closest together, and declined with distance. The average April temperature during the year of acorn drop was positively related to acorn crop size within the mountain and Piedmont ecoregions. Spatial synchrony in the red oak group was strong among sites closest together and declined with distance in the mountain region. Synchrony was weaker in the Piedmont than in the mountain ecoregion and declined slightly with increasing distance. Between the mountain and Piedmont ecoregions, synchrony was not detected among the closest sites, but was detected with increasing strength as the distance between site pairs increased. In the Piedmont ecoregion, the number of April freeze events and total July precipitation, both 2 years prior to acorn drop, were negatively related to red oak acorn production. In the mountains, average July temperature 2 years prior to acorn drop was positively related to acorn production. Main conclusions Physiographic differences affected the spatial acorn production synchrony in the red oak but not in the white oak subgenus group. Climatic factors related to annual acorn production variability differed between subgenus groups and physiographic regions. The physiographic differences between the mountain and Piedmont ecoregions may define spatial patterns of acorn production synchrony in some oak species and mediate climatic influences on acorn production.     

Biogeographic variation in nest placement: a case study with conservation implications

Abstract. Local habitat characteristics are often used to describe a species' niche despite the fact that habitat use can vary across the geographical range. We sought to quantify variation in habitat preferences by asking how nesting habit varies within and between populations of Bell's vireo ( Vireo bellii ) across its geographical range. Analyses of detailed nest placement data from three localities (Kansas, eastern New Mexico and western New Mexico) showed a general trend towards use of dense vegetation. However, there was substantial variation in nest placement and vegetation at nest sites between localities. Furthermore, a review of nest placement data from the literature shows strong differences in nest heights and species of trees even between populations less than 100 km apart. We evaluate these results in light of conservation and suggest that to be most effective, habitat conservation plans should be based on data collected at the locality where the population of interest occurs.     

Predicting the potential distribution of the beaded lizard and identification of priority areas for conservation

The beaded lizard (Heloderma horridum) is listed as a threatened species in Mexico. Scientific research has been limited to two sites within its range (Chamela and Valle Motagua) outside of these two regions there have not been adequate surveys to define range limits or measure environmental correlates for defining suitable habitat. We constructed an ensemble model (EM) for the distribution of suitable habitat for H. horridum in both Mexico and Guatemala and then used that model to identify potential areas to focus conservation. We used nine presence-only modeling methods, and selected three to generate our EM. We used the EM to evaluate the efficacy of the existing Protected Natural Areas (PNAs) in Mexico and Guatemala for H. horridum. Also we used the best individual predictive model (Maxent) to obtain the most important factors for H. horridum presence and used them to analyse the habitat use; finally we used our predictive model to calculate niche breath for the species. The estimated potential distribution of H. horridum is 370,474 km²; within this area we identified nine zones based on continuity and natural barriers. About 1.5% of the species distribution is under protection in the PNAs. The five most important factors for the presence of this species explained 78.2% of the generated model and are related to seasonality and soil cover, and these are used selectively. This species is closely associated with tropical deciduous forests, one of the most threatened ecosystems worldwide and is inadequately protected in both Mexico and Guatemala. Our results clearly show the necessity of a protection plan for this species.     

Habitat use of the Rio Grande silvery minnow (Hybognathus amarus) during a long-term flood pulse in the Middle Rio Grande, New Mexico

The Middle Rio Grande (MRG) of New Mexico has been influenced by man for over 500?years. Native Americans began diverting water to irrigate agricultural crops in the floodplain in the 14th century. The Spanish followed and increased agricultural irrigation to over 125 000 acres. Frequent flooding of the MRG valley in the 19th century led to many engineering projects in the early 20th century to control flooding. A series of impoundment dams, diversion dams, and levees were constructed. The loss of floodplain habitats throughout the MRG Valley has altered the riparian community and caused the demise of many fish species. A controlled flood pulse from Cochiti Reservoir, New Mexico was initiated in April 2005 to support the recovery of the endangered Rio Grande silvery minnow, Hybognathus amarus. This study documents habitat selection by larval fishes in a restored floodplain in the Rio Grande, NM. Larval fish light traps captured 394 larvae representing four cyprinid species (Pimephales promelas, H. amarus, Cyprinella lutrensis and Cyprinus carpio). Results for CCA indicate that Hybognathus amarus prefer shallow, low velocity habitats. Results from Chao-Jaccard similarity index indicated that relative contribution was highest in P. promelas at 64% followed by H. amarus 33%. Results from (dis)similarity analysis reveal that species composition between habitat orientation and date was highest in H. amarus at 42% followed by P. promelas 40%. Cyprinella lutrensis and C. carpio represented 9.5 and 8.5%, respectively. A general linear model indicated that only depth and velocity were significantly different (p?=?0.02 and p?=?0.03 respectively).     

Experimentally induced helper dispersal in colonially breeding cooperative cichlids

The ‘benefits of philopatry’ hypothesis states that helpers in cooperatively breeding species derive higher benefits from remaining home, instead of dispersing and attempting to breed independently. We tested experimentally whether dispersal options influence dispersal propensity in the cooperatively breeding Lake Tanganyika cichlids Neolamprologus pulcher and N. savoryi. Cooperative groups of these fishes breed in densely packed colonies, surrounded by unoccupied, but apparently suitable breeding habitat. Breeding inside colonies and living in groups seems to benefit individuals, for example by early detection and deterrence of predators. We show that despite a slight preference of both species for habitat with a higher stone cover, 40% of the preferred habitat remained unoccupied. On average, the colonies contained a higher number of (1) predators of adults, juveniles and eggs, (2) shelter competitors, and (3) other species including potential food competitors, compared to the outside colony habitat. Apparently, habitat differences cannot explain why these cichlids breed in colonies. Accordingly, dispersal may not be limited by a lack of suitable breeding shelters, but by the relatively higher risk of establishing an outside- compared to a within-colony breeding territory. To test whether cichlids prefer within- to outside-colony breeding territories, we provided breeding shelters inside the colony and at the colony edge and studied helper dispersal. As expected, significantly more shelters were occupied within the colony compared to the edge. New breeding pairs with several helpers occupied these shelters. We conclude that although breeding habitat is plentiful outside the colonies, helpers delay dispersal to obtain a higher quality breeding position within the group or colony eventually, or they disperse in groups. Our results suggest that (1) group augmentation and Allee effects are generally important for dispersal decisions in cooperatively breeding cichlids, consistent with the ‘benefits of philopatry hypothesis’, and (2) habitat saturation cannot fully explain delayed dispersal in these species.     

Context dependence of acorn handling by the Algerian mouse (Mus spretus)

Perceived predation risk and competition for acorns are expected to affect scatter-hoarding decisions by Algerian mice (Mus spretus). We manipulated both factors by means of predator fecal scents and ungulate exclosures. We hypothesized that high-risk perception and ungulate presence would promote acorn dispersal. In the former case, it would stimulate acorn mobilization to safe microhabitats rather than in situ consumption. In the latter, increased competition for acorns would promote their storage for later consumption. We also expected that mice would adapt their foraging behavior to previous experience modulating the strength of these effects.In the presence of ungulates, mice focused their foraging activities on food acquisition at the expenses of vigilant behaviors. However, a more efficient foraging did not entail enhanced dispersal services. Lack of anti-predatory cover in tree surroundings may have deterred mice from transporting seeds outside canopies. Increased risk interacted with previous experience. In control trees (no predator odor), mice confidence increased throughout the night resulting in decreased vigilance and enhanced acorn mobilization rates. In contrast, in risky conditions (trees with predator odor) mice maintained a base-line vigilant behavior. Contrary to our expectations, increased risk did not result in higher acorn mobilization, but the opposite. Again, the scarcity of safe microhabitats for mobilization may have been the underlying cause of this behavior.Our results show that successful acorn dispersal depends, at least partly, on plant-animal relationships that are beyond the oak-rodent mutualism. Thus, any conservation policy aimed at restoring natural regeneration of oaks should take into account the interaction network in which oak-rodent encounters are embedded. In addition, they suggest that mice incorporate direct and indirect cues of risks (habitat structure) through recent experience. A better understanding of this process will improve our ability to incorporate such temporal and spatial variability in models of acorn dispersal.     

Travel Time Predicts Fecal Glucocorticoid Levels in Free-Ranging Howlers (Alouatta palliata)

Environmental stressors impact physiology in many animal species. Accordingly, the monitoring of fecal glucocorticoid metabolites (fGCM) has been increasingly used to evaluate the physiological costs of habitat disturbance on wild animal populations, providing a powerful tool for conservation and management. Several studies have suggested that primates in forest fragments have higher fGCM levels than those in continuous forests, yet the proximate causes of fGCM variation remain to be identified. In previous studies of Mexican howlers (Alouatta palliata mexicana) in Los Tuxtlas, Mexico, we found that individuals living in a smaller and more disturbed forest fragment consumed significantly less fruit and had a significantly higher feeding effort than those living in a bigger, more conserved forest fragment. Here, we aimed to examine the effects of fruit consumption and travel time on fGCM levels in the same two groups of howlers, during three sampling sessions that differed markedly in fruit availability. We found that fGCM levels (N?=?202 fecal samples) were higher in the howler group living in the smaller forest fragment and varied seasonally in both focal groups, being lowest when fruit consumption was highest. However, our results suggest that travel time is the main factor predicting fGCM levels in howlers, and that although fruit consumption may be negatively related to fGCM levels, this relationship is probably mediated by the strong effect that fruit consumption has on travel time. Our results provide important insight into the proximate causes of fGCM variation in primates in fragments and highlight the potential conservation significance of studies showing that habitat loss and transformation can lead to increases in travel time in wild primates.     

An Analysis of Overstory Tree Canopy Cover in Sites Occupied by Native and Introduced Cottontails in the Northeastern United States with Recommendations for Habitat Management for New England Cottontail

The New England cottontail (Sylvilagus transitionalis) is a high conservation priority in the Northeastern United States and has been listed as a candidate species under the Endangered Species Act. Loss of early successional habitat is the most common explanation for the decline of the species, which is considered to require habitat with dense low vegetation and limited overstory tree canopy. Federal and state wildlife agencies actively encourage landowners to create this habitat type by clearcutting blocks of forest. However, there are recent indications that the species also occupies sites with moderate overstory tree canopy cover. This is important because many landowners have negative views about clearcutting and are more willing to adopt silvicultural approaches that retain some overstory trees. Furthermore, it is possible that clearcuts with no overstory canopy cover may attract the eastern cottontail (S. floridanus), an introduced species with an expanding range. The objective of our study was to provide guidance for future efforts to create habitat that would be more favorable for New England cottontail than eastern cottontail in areas where the two species are sympatric. We analyzed canopy cover at 336 cottontail locations in five states using maximum entropy modelling and other statistical methods. We found that New England cottontail occupied sites with a mean overstory tree canopy cover of 58% (SE±1.36), and was less likely than eastern cottontail to occupy sites with lower overstory canopy cover and more likely to occupy sites with higher overstory canopy cover. Our findings suggest that silvicultural approaches that retain some overstory canopy cover may be appropriate for creating habitat for New England cottontail. We believe that our results will help inform critical management decisions for the conservation of New England cottontail, and that our methodology can be applied to analyses of habitat use of other critical wildlife species.     

Comparison of the epifauna spatial distribution in Posidonia oceanica,Cymodocea nodosa and unvegetated bottoms: Importance of meadow edges

In order to detect the influence of seagrass, the most important habitats of shallow soft-bottom along the Mediterranean coast, on spatial distribution of epifauna, four different types of habitat were sampled: Posidonia oceanica, Cymodocea nodosa, edge of Posidonia meadow and sandy bottoms. Sampling was carried out, using the hand net method, in various random sites and at different times (April 95, August 95 and February 96) on the Alicante coast (SE Spain). A double taxonomic approach was used in order to detect spatial and temporal changes in the abundance of the main taxonomic groups and amphipod species. The differences among habitats were detected by non-parametric multidimensional scaling (MDS) for community structure and by analysis of variance for groups and amphipod populations. The community structure defined by the abundance of taxonomic groups was not significantly modified by the habitats. Single abundance of taxonomic groups also had no significant preference for the type of habitat except in the case of Acari, a group linked to Posidonia. However, certain trends of preference, such as mysids on Posidonia edge and isopods on Cymodocea, were detectable. On other hand, the amphipod assemblage showed important differences among habitats. Some species changed significantly in abundance depending on the habitat considered, e.g. Dexamine spiniventris and Perioculodes longimanus. It was possible to conclude that there is an important influence of Posidonia and Cymodocea on epifauna distribution by diversification of habitat structure on sandy bottoms, but it was more important at the species level than when considering taxonomic groups. Furthermore, sandy bottoms and the meadow edges had a relatively high importance on fauna distribution, depending on taxa and the period of the year.     

STUDIES IN THE QUERCUS UNDULATA COMPLEX. V. THE TYPE OF QUERCUS UNDULATA

The original material of Quercus undulata Torr. was collected by Edwin James on Major Long's expedition to the Rockies in 1820. The type locality was stated by Torrey as “sources of the Canadian and the Rocky Mountains.” Evidence is here adduced that the type locality is on Ute Creek, a tributary of the Canadian River, in northeastern New Mexico. The site was found to harbor Q, gambelii, Q. grisea, and numerous intermediate hybrid forms. Certain of the latter match the type of Q. undulata quite closely. The type sheet includes three elements—a branchlet regarded as the type, a twig of Q. grisea, and an isolated acorn of Q. havardii. Torrey's new species was illustrated by a figure which does not closely resemble the type, but which is more similar to Q. havardii. The acorn of Q. havardii on the type sheet must have been collected in the Texas Panhandle or western Oklahoma, where Long's party would have encountered this species. In my opinion, Torrey's figure could have been drawn from a specimen collected there, which, except for the isolated acorn, has since been lost.     

A mechanistic assessment of seasonal microhabitat selection by drift-feeding rainbow trout <Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis> in a Southwestern headwater stream

The positioning of fishes within a riverscape is dependent on the proximity of complementary habitats. In this study, foraging and non-foraging habitat were quantified monthly over an entire year for a rainbow trout (Oncorhynchus mykiss) population in an isolated, headwater stream in southcentral New Mexico. The stream follows a seasonal thermal and hydrologic pattern typical for a Southwestern stream and was deemed suitable for re-introduction of the native and close relative, Rio Grande cutthroat trout (O. clarkii virginalis). However, uncertainty associated with limited habitat needed to be resolved if repatriation of the native fish was to be successful. Habitat was evaluated using resource selection functions with a mechanistic drift-foraging model to explain trout distributions. Macroinvertebrate drift was strongly season- and temperature-dependent (lower in winter and spring, higher in summer and fall). Models identified stream depth as the most limiting factor for habitat selection across seasons and size-classes. Additionally, positions closer to cover were selected during the winter by smaller size-classes (0, 1, 2), while net energy intake was important during the spring for most size-classes (0, 1, 2, 3). Drift-foraging models identified that 81% of observed trout selected positions that could meet maintenance levels throughout the year. Moreover, 40% of selected habitats could sustain maximum growth. Stream positions occupied by rainbow trout were more energetically profitable than random sites regardless of season or size-class. Larger size-classes (3, 4+) were energetically more limited throughout the year than were smaller size-classes. This research suggests that habitat in the form of deep pools is of paramount importance for rainbow trout or native cutthroat trout.