Search

El monitoreo biológico es un método para conocer la dinámica de los ecosistemas, por lo que el objetivo del proyecto de monitoreo de aves en la Reserva de la Biosfera Mapimí (RBM), Durango fue estimar la riqueza y abundancia de aves, así como su variación temporal (invernal y reproductiva). Este monitoreo lo hemos realizado de 2012 hasta 2017 en 122 puntos de conteo distribuidos en el área protegida. Identificamos especies y número de individuos visual y auditivamente durante periodos de 10 y 20 min y estimamos el porcentaje de la cobertura vegetal. Durante este periodo (5 años) registramos 149 especies de aves, siendo 2015 el de mayor número de especies observadas. La especie con el mayor número de individuos observados fue el gorrión de ala blanca Calamospiza melanocorys. Encontramos diferencias estadísticas en la riqueza (P < 0.05), número de individuos (P < 0.05) y porcentaje de cobertura vegetal (P < 0.05) de la temporada invernal y reproductiva entre los años 2012 y 2017. Entre los años 2016 y 2017 encontramos diferencias entre la riqueza de aves y número de individuos del periodo invernal (P < 0.05); mientras que no encontramos diferencias en la temporada reproductiva (P > 0.05).

Distribution models are increasingly being used to understand how landscape and climatic changes are affecting the processes driving spatial and temporal distributions of plants and animals. However, many modeling efforts ignore the dynamic processes that drive distributional patterns at different scales, which may result in misleading inference about the factors influencing species distributions. Current occupancy models allow estimation of occupancy at different scales and, separately, estimation of immigration and emigration. However, joint estimation of local extinction, colonization, and occupancy within a multi‐scale model is currently unpublished. We extended multi‐scale models to account for the dynamic processes governing species distributions, while concurrently modeling local‐scale availability. We fit the model to data for lark buntings and chestnut‐collared longspurs in the Great Plains, USA, collected under the Integrated Monitoring in Bird Conservation Regions program. We investigate how the amount of grassland and shrubland and annual vegetation conditions affect bird occupancy dynamics and local vegetation structure affects fine‐scale occupancy. Buntings were prevalent and longspurs rare in our study area, but both species were locally prevalent when present. Buntings colonized sites with preferred habitat configurations, longspurs colonized a wider range of landscape conditions, and site persistence of both was higher at sites with greener vegetation. Turnover rates were high for both species, quantifying the nomadic behavior of the species. Our model allows researchers to jointly investigate temporal dynamics of species distributions and hierarchical habitat use. Our results indicate that grassland birds respond to different covariates at landscape and local scales suggesting different conservation goals at each scale. High turnover rates of these species highlight the need to account for the dynamics of nomadic species, and our model can help inform how to coordinate management efforts to provide appropriate habitat configurations at the landscape scale and provide habitat targets for local managers.

Local winter abundance of grassland passerines is highly variable throughout the Chihuahuan Desert among years. The objective of this study is to determine if plant biomass in grasslands and precipitation are predictors of bird abundance in space and time through Chihuahuan Desert. We conducted avian surveys in 17 Grassland Priority Conservation Areas (GPCA) in northern Mexico and southwestern United States in the winters of 2007–2011. We used distance sampling on line transects to estimate annual winter bird density in all GPCAs. We used a hierarchical model of distance sampling to estimate the effect of summer precipitation and vegetative cover during the fall on bird density for 10 grassland species. We used the MODIS NDVI at a pixel resolution of 231.5 m as a measure of plant biomass. Grasshopper Sparrow, Baird's Sparrow, Savannah Sparrow, Vesper Sparrow, and Eastern Meadowlark showed a strict positive response to NDVI, while Horned Lark, Sprague's Pipit, Chestnut-collared Longspur and Lark Bunting did not show a strictly-positive response to NDVI. Our results provide a valuable tool for the conservation of declining migratory birds on their wintering grounds by identifying a wildlife-habitat relationship using a remotely-sensed and readily available index of vegetative growth.

Grazing on natural rangelands, which are areas dominated by native vegetation that are used for livestock grazing, can achieve desired vegetation outcomes, preserve native habitat, and economically benefit multiple stakeholders. It is a powerful tool that can be manipulated to reduce wildlife declines and benefit ecosystems. However, the benefits of conservation grazing systems on many wildlife communities remain relatively unexplored. We compared songbird communities between two grazing systems in eastern Montana: rest-rotation, which is a conservation grazing system, and season-long. We measured differences in abundance of eight songbird species over a two year period using dependent double-observer transect surveys and a multispecies dependent double-observer abundance model. The species were chosen to be representative of the sagebrush grassland community: a sagebrush obligate, Brewer's sparrow (Spizella breweri); a faculatative grassland species, brown-headed cowbird (Molothrus ater); grassland obligate species, chestnut-collared longspur (Calcarius ornatus), horned lark (Eremophila alpestris), lark bunting (Calamospiza melanocorys), McCown's longspur (Rhynchophanes mccownii), and western meadowlark (Sturnella neglecta); and a generalist, vesper sparrow (Pooecetes gramineus). Our results show that these species exhibit mixed responses to these two grazing systems. The sagebrush obligate (Brewer's sparrow), generalist (vesper sparrow), and two grassland associated species (horned lark and chestnut-collared longspur) were equally abundant on both grazing systems, suggesting grazing system had no effect on their abundance. However, the remainder of the grassland associated species showed a response to grazing: three (brown-headed cowbird, lark bunting, and western meadowlark) were more abundant in season-long than rest-rotation, whereas one (McCown's longspur) was more abundant in rest-rotation. These results suggest that differences in grazing management affect a subset of grassland obligate species and that only one species, McCown's longspur, preferred conservation grazing. Our findings provide useful information for assessing the suitability of grazing as a conservation tool for songbirds.

Downward trends in populations of many grassland bird species are of conservation concern. Declines in black-tailed prairie dog ( Cynomys ludovicianus ) populations result in loss of habitat for birds and other species associated with their colonies. We measured abundance, diversity, and species composition of avian communities on prairie dog colonies and noncolony sites in the Texas Panhandle. More resident species ( P P = 0.003) and nearctic-temperate migrants ( P P P Hirundo rustica ), red-winged blackbirds ( Agelaius phoeniceus ), horned larks ( Eremophila alpestris ), and chipping sparrows ( Spizella passerina ) were more abundant on noncolony sites than on prairie dog colonies. Burrowing owl ( Athene cunicularia ), Cassin’s sparrow ( Peucaea cassinnii ), and lark bunting ( Calamospiza melanocorys ) abundances were greater on prairie dog colonies. Vegetative alterations made by prairie dogs may not influence bird populations as much in these shortgrass prairies as has been reported in mixed-grass prairies.

Grassland songbird populations are declining, and one reason for this might be livestock management practices in native prairies. Although cattle grazing is a common practice in native mixed-grass prairie, little research has been conducted to date to determine its impact on prairie songbird nest survival. During the summers of 2006–2007, we examined the effects of low- to moderate-intensity cattle grazing typical of the region and nest site vegetation structure on nest survival of five species of ground-nesting songbirds in native mixed-grass prairie in southwestern Saskatchewan, Canada. There was no significant effect of grazing ( P > 0.10) on Sprague’s pipit ( Anthus spragueii ), Baird’s sparrow ( Ammodramus bairdii ), vesper sparrow ( Pooecetes gramineus ), lark bunting ( Calamospiza melanocorys ), or chestnut-collared longspur ( Calcarius ornatus ) nest survival. All five species used denser vegetation than was generally available ( P ≤ 0.001). Sprague’s pipit nest survival was negatively correlated with vegetation density ( P = 0.055) and litter depth ( P = 0.033), and vesper sparrow nest survival was positively correlated with increased visibility from above ( P = 0.056), but nest survival of the other species was independent of vegetation structure. Our results suggest that low- to moderate-intensity grazing is consistent with the conservation needs of ground-nesting songbirds in mixed-grass prairies of southwestern Saskatchewan.

The major forces of food and predation shape fitness-enhancing decisions of birds at all stages of their life cycles. During the breeding season, birds can minimize nest loss due to predation by selecting sites with a lower probability of predation. To understand the environmental and social aspects and consequences of breedingsite selection in prairie birds, we explored variation in nest-survival patterns of the Lark Bunting (Calamospiza melanocorys) in the shortgrass prairie region of North America. Over four breeding seasons, we documented the survival of 405 nests, conducted 60 surveys to estimate bird densities, and measured several vegetative features to describe habitat structure in 24 randomly selected study plots. Nest survival varied with the buntings' density as described by a quadratic polynomial, increasing with density below 1.5 birds ha-1 and decreasing with density between 1.5 and 3 birds ha-1, suggesting that an optimal range of densities favors reproductive success of the Lark ...

Competition over resources can lead to fights and injury, so many species have evolved badge-of-status signals to settle conflicts without resorting to overt aggression. Most studies of status signals have focused on a single trait, under the assumption that aggression is univariate and therefore multiple signals would be redundant. We examined the relationship between male–male social dominance and several plumage traits (wing patch size and colour, body colour and coverage of black feathers on the body or the rump) in lark buntings, Calamospiza melanocorys, using a combination of observation and experimental territorial intrusions. Large body size was correlated with elevated aggression in several assays. Our observational data suggest that some traits function as close-range badges of status, because males with a larger proportion of black feathers on the body and rump win escalated contests, whereas other traits function at longer distances, because males with larger wing patches experience fewer territorial intrusions. Experimental tests of social dominance further suggest that different male plumage traits convey different information: some traits were associated with physical aggression, whereas other traits were associated with the intensity of approach. Together, these results show that selection can favour multiple badges of status to accommodate different levels of escalation or context-dependent dominance interactions.

© 2015 British Ecological Society. Multiple signals should be favoured when the benefit of additional signals outweigh their costs. Despite increased attention on multiple-signalling systems, few studies have focused on signal architecture to understand the potential information content of multiple signals. To understand the patterns of signal plasticity and consistency over the lifetime of individuals we conducted a longitudinal study of multiple signals known to be under sexual selection in male lark buntings, Calamospiza melanocorys. Within years, we found extensive among-individual variation in all four plumage ornaments we measured. Surprisingly, there were few correlations among these signals, suggesting that individuals contain a mosaic of signals. Signals were only moderately repeatable across years, which indicates some signal plasticity or age related change. In some years, the direction of change in particular signals relative to the previous year was consistent for most individuals in the population, suggesting that broad scale ecological factors affected the ornament phenotype. Different ornaments were affected by different ecological or social factors because the population-wide shift in a given signal was independent of change in other signals. Our combined results suggest that different signals-including different components of the same color patch in some cases-provide diverse and independent information about the individual to signal receivers in the context of sexual selection.

Understanding the influences of habitat fragmentation on vertebrate populations is essential for the protection and ecological restoration of strategic sites for native species. We examined the effects of prairie fragmentation on avian reproductive success using artificial and natural nests on 26 randomly selected, privately owned patches of shortgrass prairie ranging in size from 7 to 454 ha within a cropland matrix in Washington County, Colorado, summer 2000. Survival trends of artificial and natural nests differed. Daily survival of artificial nests increased with patch size up to about 65 ha and differed little at larger patch sizes, whereas daily survival of Lark Bunting (Calamospiza melanocorys) and Horned Lark (Eremophila alpestris) nests decreased with increasing size of the grassland patch. We hypothesize that our unexpected findings of lower survival of natural nests with increasing patch sizes and different trends between artificial and natural nests are due to the particular structure...

During 2000–2001, small mammals, birds, and potential corn/soybean damage were studied at a low-tillage, non-irrigated agricultural research site in the Colorado Piedmont. A small mammal survey involved four trapping sessions and 18, 12-live-trap grids each. Within years, two grids each were placed at random, fixed locations in experimental corn, fallow, millet, pea, soybean, sunflower, and wheat plots at the site; two off-plot grids each were set at random, fixed locations X =2.2% ). Sixty-three small mammals were captured and 39 were recaptured. Captures included deer mouse (Peromyscus maniculatus), northern grasshopper mouse (Onychomys leucogaster), thirteen-lined ground squirrel (Spermophilus tridecemlineatus), and western harvest mouse (Reithrodontomys megalotis). Deer mice accounted for 56 of the initial captures (88.9%). In-crop captures (n=15) and recaptures (n=16) were most frequent in wheat plots. Bird counts were low and included horned lark (Eremophila alpestris), killdeer plover (Charadrius vociferus), lark bunting (Calamospiza melanocorys), mountain plover (Charadrius montanus), mourning dove (Zenaida macroura), and western meadowlark (Sturnella neglecta). No direct seed removal, sprout removal, or plant clipping by small mammals or birds was observed, but some clipping of soybean plants was attributed to deer (Odocoileus virginianus and O. hemionus) and jack rabbits (Lepus townsendii or L. californicus). Plant debris accumulation is viewed as a key factor determining small mammal abundance and potential damage in low-till agriculture.

The influence of recent climate change on the world's biota has manifested broadly, resulting in latitudinal range shifts, advancing dates of arrival of migrants and onset of breeding, and altered community relationships. Climate change elevates conservation concerns worldwide because it will likely exacerbate a broad range of identified threats to animal populations. In the past few decades, grassland birds have declined faster than other North American avifauna, largely due to habitat threats such as the intensification of agriculture. We examine the effects of local climatic variations on the breeding performance of a bird endemic to the shortgrass prairie, the Lark Bunting (Calamospiza melanocorys) and discuss the implications of our findings relative to future climate predictions. Clutch size, nest survival, and productivity all positively covaried with seasonal precipitation; yet relatively intense daily precipitation events temporarily depressed daily survival of nests. Nest survival was positively related to average temperatures during the breeding season. Declining summer precipitation may reduce the likelihood that Lark Buntings can maintain stable breeding populations in eastern Colorado although average temperature increases of up to 3 degrees C (within the range of this study) may ameliorate declines in survival expected with drier conditions. Historic climate variability in the Great Plains selects for a degree of vagility and opportunism rather than strong site fidelity and specific adaptation to local environments. These traits may lead to northerly shifts in distribution if climatic and habitat conditions become less favorable in the drying southern regions of the Great Plains. Distributional shifts in Lark Buntings could be constrained by future changes in land use, agricultural practices, or vegetative communities that result in further loss of shortgrass prairie habitats.

We evaluated the influences of several ecological, biological, and methodological factors on post-fledging survival of a shortgrass prairie bird, the Lark Bunting (Calamospiza melanocorys). We estimated daily post-fledging survival (n = 206, 82 broods) using radiotelemetry and color bands to track fledglings. Daily survival probabilities were best explained by drought intensity, time in season (quadratic trend), agesor = 3 d post-fledging, and rank given drought intensity. Drought intensity had a strong negative effect on survival. Rank was an important predictor of fledgling survival only during the severe drought of 2002 when the smallest fledglings had lower survival. Recently fledged young (agesor = 3 d post-fledging) undergoing the transition from nest to surrounding habitat experienced markedly lower survival, demonstrating the vulnerable nature of this time period. Survival was greater in mid and late season than early season, corresponding to our assumptions of food availability. Neither mark type nor sex of attending parent influenced survival. The model-averaged product of the 22-d survival calculated using mean rank and median value of time in season was 0.360 +/- 0.08 in 2001 and 0.276 +/- 0.08 in 2002. Survival estimates that account for age, condition of young, ecological conditions, and other factors are important for parameterization of realistic population models. Biologists using population growth models to elucidate mechanisms of population declines should attempt to estimate species-specific of post-fledging survival rather than use generalized estimates.

In the lark bunting, a grassland "sparrow," polygyny occurs. Pleszczynska (1978) demonstrated that certain females must choose between being the secondary female on a prime site or the only mate of a male on an inferior habitat. Here, we examine the decision process of those females and demonstrate that a simple decision model is insufficient to account for their behavior. Rather the decision arises from the solution of a conflict between seasonal and lifetime expected utility (number of fledged young).

1 describe here breeding season diets of Aplomado Falcons (Fc ground-doves (Mader 198 1); a wren (Cumpylorhynchus sp.), snipe (Gallinago sp.), antshrike (Thamnophilus p.; Cherrie 19 16); Horned Lark (Eremophila lpestris; Kellogg in Bailey 1928); Cassin’s Sparrow (Aimophila cussinii; Strecker 1930); plovers, sandpipers, nighthawks, Ruddy Ground-Dove (Columbina talpacotl], Scaled Dove (Scardafella squammata), Pale-vented Pigeon (Columba cayennensis), Rock Dove (C. livia), and a fledgling hummingbird (Friedmann and Smith 1950, 1955); Lark Bunting (Calamospiza melanocorys), and Lark Sparrow (Chondestes grammacus; Ligon 1961); doves and quail (Wetmore 1965); tinamou (Johnson 1965); Plain-breasted Ground-Dove (Columbina minuta; Howell 1972); and Dickcissel (Spiza americana; ffrench 1973). Other vertebrate prey are: bats (Ligon 196 1, ffrench 1973, and Mader 198 1); kangaroo rats (specimen notes of R. D. Camp); pocket mice (Perognathus sp.), white-footed mice (Peromyscus sp.; Strecker 1930); lizards (Bendire 1887, Wetmore 1965); frogs (Haverschmidt 1968); and small fish (Cherrie 19 16). Invertebrate prey include locusts, beetles, dragonflies, crickets, butterflies, wasps, and bees (Bendire 1887, Cherrie 1916, Bailey 1928, Brooks 1933, and Mitchell 19 5 7). This list of prey species indicates the variety of animals captured by Aplomado Falcons, but says nothing about the relative importance of various prey in the diet. Many older descriptions of these birds stated that they subsist on insects, small mammals, and reptiles (Bendire 1887, Sclater and Hudson 1889, Bailey 1928, Sprunt 1955, and Ligon 196 1). These assertions conflict with evidence that the species is an upper trophic-level predator (Kiff et al. 1980) and have led at least one recent authority to suggest that the Aplomado Falcon

The flight display of the male lark bunting (Calamospiza melanochorys) has been hypothesized to function in mate attraction, courtship, and establishment and maintenance of territory. However, empirical support for these suggestions has not yet been provided. The present investigation provides a behavioral analysis of male lark buntings in reproductive condition and documents three phases in the reproductive cycle: preterritorial, territorial, and mated. The flight display was observed in foraging groups of preterritorial males, apparently in response to conspecific flyovers. Solitary territorial males responded to conspecific flyovers (intrusions) with a flight display and pursuit of the intruder. Flight displays were not observed in mated males. The observations suggest that: (1) the communal flight displays of preterritorial males encourage dispersal of the males, and (2) the solitary flight-displays of territorial males subserve establishment and maintenance of territory. Hypotheses are advanced regarding the role of the males’ flight display in the reproductive development of females and the absence of these displays during the mating phase.

Field experiments on breeding populations of lark buntings (Calamospiza melanocorys) in South Dakota support the hypothesis that polygyny is promoted by a high variance in quality among male territories. Among these birds protection of the nest site from solar radiation is the major indicator of quality: nestling survival was significantly correlated with nest-site cover, and experimental increase of shading resulted in higher reproductive success. Males with superior territories attracted two mates, whereas those with poor territories failed to attract any. Secondary females had fledging success at least equal to that of contemporaneous monogamous pairs. On the sole basis of a shading score for each territory, the mating status of males (polygynous, monogamous, or bachelor) was predicted accurately in new areas of Colorado and North Dakota before females arrived.