Assessing non-parametric estimators of species richness. A case study with birds in green areas of the city of Puebla, Mexico Our objective was to evaluate the performance of non-parametric estimators of spe-cies richness with real data. During the 2003 breeding season, bird communities were sampled in two green areas in the city of Puebla (Mexico), and the corresponding sample-based rarefaction curves were obtained. Mean data were adjusted to two non-asymptotic and seven asymptotic accumulation functions, and the best model was selected by means of reliability criteria in information theory. The cumulative Weibull and the beta-P functions were the best-fit models. Bias, precision and accuracy of five non-parametric estimators of species richness (ICE, Chao2, Jackknife 1, Jackknife 2, and Bootstrap) were then assessed for increasing sampling efforts (1-53 sampling units) against the asymptote of the selected accumulation functions. All the non-parametric estimators here evaluated underestimated true richness most of the time, specially in one of the sites. However, after combining data from the two assemblages, only ICE, and Jackknife 1 and 2 exhibited bias below 10% with different sampling efforts, and only Jackknife 1 was globally accurate (scaled mean squared error x 100 < 5%, even with low sampling efforts, ca. 20% of the total). Therefore, we propose using the Jackknife 1 non-parametric estimator as a lower limit to measure bird species richness in urban sites similar to those in the present study.

Characterization and selection of nest sites by the Cuban sandhill crane (Grus canadensis nesiotes) in the grasslands of the El Venero Wildlife Refuge, Cuba Grus canadensis nesiotes is an endemic threatened subspecies of crane that inhabits freshwater wetlands. We characterized its nesting site and analyzed nest-site selection at three spatial scales in grasslands of El Venero Wildlife Refuge (Cuba), during the breeding seasons of 2005-2007. We monitored 26 nests until hatching. We also measured vegetation height, coverage at 30 and 100 cm, and distance between grass stems at nests. These values were compared with values measured at points 100 m away from nests. We used a GIS to obtain distances to channels, roads and forest patches, as well as to determine percentages of grass, water, palm-grass and casuarina-grass in circles of 100, 400, 700 and 1,000 m of radius around both nests and random points. Vegetation variables around nests (height: 78.9 ± 2.1; coverage at 30 cm: 97.8± 0.6; coverage at 100 cm: 64.7 ± 1.6) were lower than those at 18 m away. There were no differences in vegetation variables or distances to forests and water between nests and random points located farther. Percentage covers of grassland and forest influenced nest site selection. Average distance between simultaneous active nests was 1,305.8 ± 106 m, the smaller area of potential use was 30,3 km2 and the mean influence area was 2,13 ± 0,36 km2. Nest site selection by cranes, as well as nest site characteristics, depended of the presence of extensive areas of grassland.

A new species Anthrenus (Florilinus) loebli from Israel, Lebanon and Jordania is described, illustrated and compared with the similar species classified within the subgenus Florilinus Mulsant & Rey, 1868. The new species is characterized by oval eyes, eight-segmented antenna and subtriangular, occasionally triangular, scales on the dorsum. The yellowish/light brown scales are present on the anterior and terminal part of the elytra and create three irregular, transverse bands. Antennal segment eight are at least 4.8 to 5x longer than segment 7 in male, 2.1x longer in female. The new species is most similar to A. (F.) museorum (Linnaeus, 1761); A. (H.) fuscus Olivier, 1789 and A. (F.) flavidus Solsky, 1876. An identification key to externally similar species of the genus is given. The most distinctive taxonomic characteristics concern the male genitalia and antenna (in ratio of length of segments of antennal club) and are also described.

Headwaters can represent 80% of stream kilometers in a watershed, and they also have unique physical and biological properties that have only recently been recognized for their importance in sustaining healthy functioning stream networks and their ecological services. We sampled 60 headwater tributaries in the South Fork Trinity River, a 2,430 km2, mostly forested, multiple-use watershed in northwestern California. Our objectives were: (1) to differentiate unique headwater types using 69 abiotic and vegetation variables measured at three spatial scales, and then to reduce these to informative subsets; (2) determine if distinct biota occupied the different tributary types; (3) determine the environmental attributes associated with the presence and abundance of these biotic assemblages; and (4) using niche modeling, determine key attribute thresholds to illustrate how these biota could be employed as metrics of system integrity and ecological services. Several taxa were sufficiently abundant and widespread to use as bio-indicators: the presence and abundance of steelhead trout (Oncorhynchus mykiss), herpetofauna (reptile and amphibian) species richness, and signal crayfish (Pacifastacus leniusculus) represented different trophic positions, value as commercial resources (steelhead), sensitivity to environmental stress (amphibians), and indicators of biodiversity (herpetofauna species richness). Herpetofauna species richness did not differ, but abundances of steelhead trout, signal crayfish, and amphibian richness all differed significantly among tributary types. Niche models indicated that distribution and abundance patterns in both riparian and aquatic environments were associated with physical and structural attributes at multiple spatial scales, both within and around reaches. The bio-indicators responded to unique sets of attributes, reflecting the high environmental heterogeneity in headwater tributaries across this large watershed. These niche attributes represented a wide range of headwater environments, indicating responses to a number of natural and anthropogenic conditions, and demonstrated the value of using a suite of bio-indicators to elucidate watershed conditions, and to examine numerous disturbances that may influence ecological integrity.

The Citril finch Serinus citrinella is a Paleartic endemic species that breeds in the subalpine mountain zones of western temperate Europe. The species seems to be suffering a serious decline in its northern range, mainly in the Black Forest and the NE of the Alps. Numerous reasons have been provided for this decline, but all of them have been related to breeding habitats. Given that the species undergoes an altitudinal migration and that during winter it may use very different habitats, a sound knowledge of the distribution patterns and habitats used outside the breeding period is needed to conduct adequate conservation policies and management. This information, however, is largely lacking. The aim of this paper was to determine the current habitat used by Citril finches in north-eastern Spain during the winter, to analyse habitat suitability and to study movements, by investigating the origin of birds that overwinter in Catalonia. Citril finch distribution was modelled using both discriminant analysis and maximum entropy modelling, on the basis of species occurrences during winter in Catalonia (data from 1972-2009). Results showed that the presence of two tree species, Black pine (Pinus nigra subsp. salzmanii) and Scots pine (Pinus sylvestris), both as part of mixed open forests, and the presence of abundant farmland and arvensic plants -the two vegetation units located in a typical submediterranean context, where the warm temperatures (sunny days) in late winter permit the cones to open-, were the ecological and bioclimatic variables that explain the distribution model. All these variables in tandem seem to be the key for the current potential distribution of the Citril finch in winter (AUCscores: training data AUC= 0.955; test data AUC = 0.953). We analyzed recoveries (N = 238) of 2,368 birds ringed at wintering grounds and 12,648 birds ringed at subalpine localities in the adjacent Pyrenees from 1977-2004. We found that in the study area, we recovered ringed birds from many different locations from across the distributional range of the species, including trans-Pyrenean birds from the Alps. This stresses the high mobility of Citril finch populations to reach wintering areas. From a conservation point of view, the high importance of pines (mainly Black pine) for the wintering distribution of the species stresses that any threat on pines, especially forest fires, will have acute detrimental effects for Citril finch populations.

A juvenile loggerhead turtle with buoyancy problems was captured in the Alboran Sea (Mediterranean Sea, south of Spain) and released 14 months later after healing. Six days after the release, the turtle was seen swimming 42 km from the point of release, displaying unusual behaviour. We re-captured and released it again, 95 nautical miles offshore, near the Alboran Island. Ten days later the turtle arrived at the beach close to where it had been maintained in captivity. We discuss these findings in the context of behavioural alteration and habituation in released sea turtles. Capture-mark-recapture studies of sea turtles should be approached with caution as manipulated animals may modify their usual behaviour.

Ecological studies focused on small-scale habitat alterations have found positive, null, and negative effects on biodiversity. In this study, we describe the effects that establishing a relatively small area of garden allotments had on bird communities. To assess such effects, we analyzed avian community diversity (i.e., species richness and abundance) and behavioral traits (i.e., foraging, perching). Although land transformation was recent and on a small geographic-scale, our results showed that bird communities in the allotments were dominated by a few species, while in the almond plantation (former habitat) evenness was higher. When perching and foraging behavior was compared in the two study areas, we found a significantly higher proportion of foraging in the garden allotments, and a higher proportion of birds perching in the naturalized plantation. Although new habitats often enhance regional bird species richness in Mediterranean landscapes, we found no evidence of an increase in regional avian diversity related to the establishment of small garden allotments. We propose that future harvesting activities should consider the scale, intensity, and frequency of the generated perturbation in order to promote biodiversity.

A few years ago, Camus & Lima (2002) wrote an essay to stimulate ecologists to think about how we define and use a fundamental concept in ecology: the population. They concluded, concurring with Berryman (2002), that a population is ‘a group of individuals of the same species that live together in an area of sufficient size to permit normal dispersal and/or migration behaviour and in which population changes are largely the results of birth and death processes’. They pointed out that ecologists often forget ‘to acknowledge that many study units are neither natural nor even units in terms of constituting a population system’, and hence claimed that we ‘require much more accuracy than in past decades in order to be more effective to characterize populations and predict their behaviour’. They stated that this is especially necessary ‘in disciplines such as conservation biology or resource pest management, to avoid reaching wrong conclusions or making inappropriate decisions’. As a population ecologist and conservation biologist I totally agree with these authors and, like them, I believe that greater precision and care is needed in the use and definition of ecological terms. The point I wish to stress here is that we ecologists tend to forget that when we use statistical tools to infer results from our sample to a population we work with what statisticians term ‘imaginary’, ‘hypothetical’ or ‘potential’ popula-tions. As Zar (1999) states, if our sample data consist of 40 measurements of growth rate in guinea pigs “the population about which conclusions might be drawn is the growth rates of all the guinea pigs that conceivably might have been administered the same food supplement under identical conditions”. Such a population does not really exist, and hence it is considered a hypothetical or imaginary population. Compare that definition with the population concept that would be in our minds when performing such measurements. We would probably assume that our study population consisted of pigs (not the growth rates of pigs!) and probably all the pigs at the farm we were sampling, rather than the all the growth rates of the pigs that might conceivably have been administered the same food. We overlook the fact that we are using the statistical tools to try to estimate ecological population para-meters (and test specific hypotheses on the values of these population parameters) but that the ecological population which is in our minds and the statistical (imaginary) population of our tests need not necessarily be the same (and most often are not). So, to avoid wrong inferences (with wide-ranging consequences if we are dealing with decision-making processes) we should do all we possibly can to ensure that our natural populations are as similar as possible to the imaginary populations of statisticians, or at least we should discuss our results within the framework in which our inference was developed. Statistics is not an ad hoc tool invented for us, but rather a tool that we have borrowed from statisticians for our purposes. We should always keep this in mind.

Small-scale canopy gaps created by logging may retain adequate habitat structure to maintain amphibian abundance. We used pitfalls with drift fences to measure relative abundance of amphibians in 44 harvested gaps, 19 natural treefall gaps, and 36 closed-canopy forest plots. Metamorphs had relatively lower capture rates in large harvest gaps for Ambystoma maculatum, Lithobates catesbeianus, L. clamitans, and L. sylvaticus but we did not detect statistically significant (p < 0.1) differences among gap types for Lithobates palustris metamorphs. L. clamitans juveniles and L. sylvaticus juveniles and adults had relatively lower capture rates in large harvest gaps. For juvenile-adult A. maculatum, we caught relatively fewer individuals in all gap types than in closed-canopy areas. Some groups with overall lower capture rates (immature Plethodon cinereus, juvenile L. palustris) had mixed differences among gap types, and Notophthalmus viridescens (efts) and adult P. cinereus showed no differences among gap types. One species, L. clamitans, was captured more often at gap edges than gap centers. These results suggest that harvest gaps, especially small gaps, provided habitat similar to natural gaps for some, but not all, amphibian species or life-stages.