Winter herbivory by voles during a population peak: the relative importance of local factors and landscape pattern

1. We studied the relative role of local habitat variables and landscape pattern on vole–plant interactions in a system with grey-sided voles ( Clethrionomys rufocanus (Sund.)) and their favourite winter food plant, bilberry ( Vaccinium myrtillus L.). The study was conducted during a vole peak year (1992–93) in a tundra area in northern Norway.
2. Using Mantel statistics we were able to separate the direct effects of the spatial patterning of habitats and the indirect effects due to spatial aggregations of similar habitats.
3. Results indicate that knowledge about the explicit spatial patterning of patches does not improve our understanding of the system. Instead, two local factors, vegetation height and bilberry biomass, explained more than 50% of the variation in cutting intensity in winter (defined as the proportion of above-ground shoots cut). Increasing vegetation height increased, and increasing bilberry biomass decreased, the cutting intensity.
4. The conclusion that grey-sided voles are able to distribute themselves relative to habitat quality was also partially supported by our estimated over-winter persistence by voles in the various habitats. Vole persistence was uncorrelated with vegetation height, the important predictor of autumn vole density, but tended to correlate with the deviation from the relation between vegetation height and autumn vole density. This conforms to the expectations from the theory of ideal-free habitat distribution.
5. The cue for vole habitat choice, i.e. vegetation height, indicates that either predation or freezing risk is important for voles when selecting over-wintering habitat.     

VOCAL DIALECTS AND THE STRUCTURE OF GEOGRAPHIC VARIATION IN MORPHOLOGICAL AND ALLOZYMIC CHARACTERS IN THE RUFOUS-COLLARED SPARROW,ZONOTRICHIA CAPENSIS

The geographical patterns of variation shown at 20 allozyme and non-enzymatic protein-coding loci, in 8 external, and in 12 skeletal morphological characters in the rufous-collared sparrow, Zonotrichia capensis, were analyzed in order to test the local (genetic) adaptation hypothesis regarding the origin and maintenance of vocal dialects in birds. Approximately 20 males were collected from each of four sites within each of six different dialect zones. There was significant variability in both external and skeletal morphology among all 24 sites and among dialect groups. Average Wright's corrected fixation coefficient (F_ST) was 0.118, indicating significant genetic differentiation among all sites, regardless of dialect. Hierarchical F statistics indicated that only 50% of among site variability was due to a dialect effect. Puna dialect sites were highly differentiated from all other sites with respect to both morphology (external and skeletal measures) and allozyme frequencies. Heterogeneity at the PGM-1 locus among puna scrub sites was the major cause of the high average F_ST across all sites, and within the puna scrub dialect. Average genetic differentiation among non-puna sites (F_ST = 0.018) was similar to differentiation among sites within each of the five non-puna dialect groups (mean F_ST = 0.0132 ± 0.0069). Hierarchical F statistics indicated that none of the among-site differentiation in this subset of samples was due to a dialect effect. These observations are not consistent with the local adaptation hypothesis. All significant genetic heterogeneity occurred among sites in mountainous habitats, and we suggest that topography and patchiness of habitat may have been major factors involved in population differentiation, rather than vocal dialects.     

Timing of migration dates and detection of first wintering sites for the Turtle Dove in Northwest Africa

The identification of migration dates and wintering zones for migratory birds are key elements for the understanding of the Afro-Palearctic migration system. From 2015 to 2022, a large-scale survey of Turtle Doves Streptopelia turtur, a vulnerable species, was established in Northwest Africa, including Morocco, Algeria, and Tunisia. We monitored migration dates and wintering individuals using the line-transect method. We found that Turtle Doves arrived in the last week of March and left the North African region in mid-October. Compared with Morocco, Doves arrived significantly earlier in Algeria and Tunisia. Moreover, Doves were discovered wintering on nine Northwest African sites, from October to February, where individuals feed in groups. We found that the occurrence probability of wintering Turtle Doves decreased significantly with increasing temperature and rainfall. Birds wintered most often close to wetlands since the overwintering probability decreased with the increasing distance from the recording area to the nearest water body. These are the first and only detailed findings on the migration phenology of the globally vulnerable Turtle Dove in north western Africa.     

栖息地演变与人为干扰对升金湖越冬水鸟的影响

2002年10月—2003年4月,选择安徽升金湖6个不同干扰程度和栖息地质量的固定监测点,研究人为干扰对升金湖越冬水鸟分布格局的影响;同时结合前期调查数据,研究栖息地演变对升金湖越冬水鸟的影响.结果表明:同一越冬期不同监测点水鸟种类和数量与栖息地质量无显著相关关系,但水鸟数量与栖息地干扰程度显著负相关;不同年份升金湖越冬水鸟种类和数量与栖息地质量显著相关.升金湖越冬水鸟存在的主要威胁包括栖息地丧失、人为活动干扰以及生物杀灭剂的影响.提出了一些保护升金湖越冬水鸟的建议.     

Where do Swainson's hawks winter? Satellite images used to identify potential habitat

During recent years, predictive modelling techniques have been increasingly used to identify regional patterns of species spatial occurrence, to explore species–habitat relationships and to aid in biodiversity conservation. In the case of birds, predictive modelling has been mainly applied to the study of species with little variable interannual patterns of spatial occurrence (e.g. year‐round resident species or migratory species in their breeding grounds showing territorial behaviour). We used predictive models to analyse the factors that determine broad‐scale patterns of occurrence and abundance of wintering Swainson's hawks (Buteo swainsoni). This species has been the focus of field monitoring in its wintering ground in Argentina due to massive pesticide poisoning of thousands of individuals during the 1990s, but its unpredictable pattern of spatial distribution and the uncertainty about the current wintering area occupied by hawks led to discontinuing such field monitoring. Data on the presence and abundance of hawks were recorded in 30 × 30 km squares (n = 115) surveyed during three austral summers (2001–03). Sixteen land‐use/land‐cover, topography, and Normalized Difference Vegetation Index (NDVI) variables were used as predictors to build generalized additive models (GAMs). Both occurrence and abundance models showed a good predictive ability. Land use, altitude, and NDVI during spring previous to the arrival of hawks to wintering areas were good predictors of the distribution of Swainson's hawks in the Argentine pampas, but only land use and NDVI were entered into the model of abundance of the species in the region. The predictive cartography developed from the models allowed us to identify the current wintering area of Swainson's hawks in the Argentine pampas. The highest occurrence probability and relative abundances for the species were predicted for a broad area of south‐eastern pampas that has been overlooked so far and where neither field research nor conservation efforts aiming to prevent massive mortalities has been established.     

Daily torpor and hibernation in birds and mammals

Many birds and mammals drastically reduce their energy expenditure during times of cold exposure, food shortage, or drought, by temporarily abandoning euthermia, i.e. the maintenance of high body temperatures. Traditionally, two different types of heterothermy, i.e. hypometabolic states associated with low body temperature (torpor), have been distinguished: daily torpor, which lasts less than 24 h and is accompanied by continued foraging, versus hibernation, with torpor bouts lasting consecutive days to several weeks in animals that usually do not forage but rely on energy stores, either food caches or body energy reserves. This classification of torpor types has been challenged, suggesting that these phenotypes may merely represent extremes in a continuum of traits. Here, we investigate whether variables of torpor in 214 species (43 birds and 171 mammals) form a continuum or a bimodal distribution. We use Gaussian‐mixture cluster analysis as well as phylogenetically informed regressions to quantitatively assess the distinction between hibernation and daily torpor and to evaluate the impact of body mass and geographical distribution of species on torpor traits. Cluster analysis clearly confirmed the classical distinction between daily torpor and hibernation. Overall, heterothermic endotherms tend to be small; hibernators are significantly heavier than daily heterotherms and also are distributed at higher average latitudes (～35°) than daily heterotherms (～25°). Variables of torpor for an average 30 g heterotherm differed significantly between daily heterotherms and hibernators. Average maximum torpor bout duration was >30‐fold longer, and mean torpor bout duration >25‐fold longer in hibernators. Mean minimum body temperature differed by ～13°C, and the mean minimum torpor metabolic rate was ～35% of the basal metabolic rate (BMR) in daily heterotherms but only 6% of BMR in hibernators. Consequently, our analysis strongly supports the view that hibernators and daily heterotherms are functionally distinct groups that probably have been subject to disruptive selection. Arguably, the primary physiological difference between daily torpor and hibernation, which leads to a variety of derived further distinct characteristics, is the temporal control of entry into and arousal from torpor, which is governed by the circadian clock in daily heterotherms, but apparently not in hibernators.     

Construct social‐behavioral association network to study management impact on waterbirds community ecology using digital video recording cameras

Studying social‐behavior and species associations in ecological communities is challenging because it is difficult to observe the interactions in the field. Animal behavior is especially difficult to observe when selection of habitat and activities are linked to energy costs of long‐distance movement. Migrating communities tend to be resource specific and prefer environments that offer more suitability for coexisting in a shared space and time. Given the recent advances in digital technologies, digital video recording systems are gaining popularity in wildlife research and management. We used digital video recording cameras to study social interactions and species–habitat linkages for wintering waterbirds communities in shared habitats. Examining over 8,640 hr of video footages, we built tetrapartite social‐behavioral association network of wintering waterbirds over habitat (n = 5) selection events in sites with distinct management regimes. We analyzed these networks to identify hub species and species role in activity persistence, and to explore the effects of hydrological regime on these network characteristics. Although the differences in network attributes were not significant at treatment level (p = .297) in terms of network composition and keystone species composition, our results indicated that network attributes were significantly different (p = .000, r ² = .278) at habitat level. There were evidences suggesting that the habitat quality was better at the managed sites, where the formed networks had more species, more network nodes and edges, higher edge density, and stronger intra‐ and inter‐species interactions. In addition, we also calculated the species interaction preference scores (SIPS) and behavioral interaction preference scores (BIPS) of each network. The results showed that species synchronize activities in shared space for temporal niche partitioning in order to avoid or minimize any potential competition for shared space. Our social network analysis (SNA) approach is likely to provide a practical use for ecosystem management and biodiversity conservation.     

THE BEHAVIOUR OF THE HOTTENTOT TEAL

Following recovery and successful rehabilitation, a young Steppe Eagle Aquila nipalensis was tagged with a 45 g GPS satellite transmitter to track its migration and identify potential wintering and summering areas of the species passing through the United Arab Emirates (UAE). The study is part of a larger study on understanding migration of important birds of prey species from the UAE. The satellite-tagged Steppe Eagle was released near the town of Al Ain, UAE on 5 January 2009 and was tracked until 6 November 2010. Two complete spring and autumn migrations were tracked in addition to its onward autumn migration from the UAE. The tagged eagle continued its autumn migration from its release site and reached Yemen after stopovers in Saudi Arabia. Unlike other Steppe Eagles, the bird did not cross the strait of Bab-al-Mandeb and wintered in the area before undertaking its first spring migration. In the second spring migration in 2010, the bird migrated along the Suez–Eilat route and demonstrated a loop migration. The bird spent the summer on the steppes in Kazakhstan, with marked differences in the home ranges between 2009 and 2010, whereas wintering areas used in 2009 and 2010 in Tanzania were overlapping.     

PROCEEDINGS of the 21st ANNUAL GENERAL MEETING of the SOUTH AFRICAN ORNITHOLOGICAL SOCIETY,HELD at the DEPARTMENT OF ZOOLOGY University of Cape Town,RONDEBOSCH, at 2.15 p.m., 9th DECEMBER, 1950

A fragmentary skull of a small passerine from the mid-Holocene organic-rich deposits at Florisbad, South Africa, shows a pattern of distinctive characters that allows its identification as a Cercomela chat. It resembles most closely the Familiar Chat C. familiaris and Karoo Chat C. schlegelii, which are still part of the avifauna in this part of South Africa. Furthermore, the significance of several characters of the skull for hypotheses on the phylogeny of Muscicapoidea in general, and Saxicolinae in particular, is discussed.     

Nest success of grassland sparrows on reclaimed surface mines

Grasslands resulting from surface mine reclamation support grassland songbird populations in several midwestern and eastern states in the United States, especially where reclaimed mines are large (>1,000 ha). However, most reclaimed surface mines in Pennsylvania are small (<200 ha), and nest success is unknown. We evaluated nest success of grasshopper (Ammodramus savannarum), Henslow's (A. henslowii), and Savannah sparrows (Passerculus sandwichensis) on 4 reclaimed surface mines (50–180 ha) in western Pennsylvania, USA from 2006 to 2007. Overall nest success based on mean covariate values was 0.435 (95% CI = 0.376–0.504) for grasshopper sparrows, 0.396 (95% CI = 0.295–0.533) for Henslow's sparrows, and 0.158 (95% CI = 0.063–0.392) for Savannah sparrows. These estimates of nest success are comparable to those on larger reclaimed mines and other habitats. Grasshopper and Henslow's sparrow nests that were well concealed were less likely to fail than highly visible nests (β_visible = −0.028, CI = −0.051 to −0.005 for grasshopper sparrows; β_visible = −0.063, CI = −0.112 to −0.014 for Henslow's sparrows), and nests in areas with surrounding deep litter were more likely to fail than nests in areas with shallow litter (β_litterD = −0.145, CI = −0.335 to 0.045 for grasshopper sparrows; β_litterD = −0.676, CI = −1.187 to −0.116 for Henslow's sparrows). Savannah sparrow nests in areas with high visual obstruction by vegetation were less likely to fail than nests in areas with sparse and short vegetation (β_VisOb = 0.048, CI = 0.006–0.091). Daily probability of survival for grasshopper sparrow nests was greatest early and late in the breeding season, and Savannah sparrow nest survival followed a decreasing linear trend. Nest survival of Henslow's sparrows was greater on warm days (β_temp = 0.197, CI = 0.014–0.379), whereas for Savannah sparrows nest survival decreased on warm days and on days with rain, but for Savannah sparrows confidence intervals of weather effects included zero (β_temp = −0.098, CI = −0.246 to 0.050; β_rain = 3.13, CI = −14.19 to 20.45). We suggest that small reclaimed surface mine grasslands can provide valuable nesting habitat and could be important to the conservation of grassland bird populations. Because nest success can increase in the latter part of the nesting season, agricultural disturbances or management activities in mid- to late summer could adversely affect reproductive success. © 2011 The Wildlife Society.