Proportions of mammalian-type and reptilian-type nephrons in the kidneys of two passerine birds

We compared the proportions of mammalian-type and reptilian-type nephrons in the kidneys of two species of passerine birds. The desert house sparrow (Passer domesticus) is relatively well adapted for water conservation, whereas the white-crowned sparrow (Zonotrichia leucophrys) is more mesic adapted. The two species do not differ in body mass, but the kidneys of P. domesticus are significantly smaller than those of Z. leucophrys. Associated with its smaller size, the house sparrow kidney has significantly fewer glomeruli (35,700 per kidney) than does the white-crowned sparrow kidney (53,000 per kidney). The medullary cones, which contain the loops of Henle of the mammalian-type nephrons, are significantly longer in house sparrows than in white-crowned sparrows (2.2 vs. 1.9 mm). The number of medullary cones, the number of nephrons per medullary cone, and, hence, the number of mammalian-type nephrons do not differ between the two species. The smaller number of nephrons in the kidney of the house sparrow therefore represents a smaller number of reptilian-type nephrons. Desert house sparrows have 18% mammalian-type nephrons, whereas white-crowned sparrows have 10% mammaliantype nephrons. The relative reduction of reptilian-type nephrons in P. domesticus may reduce the flow of dilute urine through the collecting ducts, thereby permitting a greater concentration gradient to be established along the length of the medullary cones.     

The role of native forest plantations in the conservation of Neotropical birds: the case of the Andean alder

The gradual increase in reforested areas worldwide, as a strategy for mitigating native forest loss, has stressed the need of assessing their real value as habitat for native species. Forest plantations, particularly those based on native species, could be valuable for conservation purposes, especially in heavily fragmented and disturbed ecosystems. We evaluated the value of a monoculture of a native tree species, the Andean alder (Alnus acuminata), for the conservation of avifauna in the Central Andes region, which is considered a bird species diversity hotspot but also suffers from high anthropogenic disturbance levels. Our results suggest that alder plantations are valuable for conservation from three points of view: (1) they have similar or greater bird species richness and abundance than secondary native forests; (2) low community similarities are found between this type of forest compared to secondary forest stands (with 27 species exclusive to alder plantations); and (3) three near threatened species (Odontophorus hyperythrus, Eriocnemis derbyi, and Cyanolyca viridicyanus). Further, 27 out of the 85 species found at the alder plantations were of least concern but showing decreasing population trends. While forest plantations do not replace native forests, they offer habitat for many bird species, some of them being of conservation concern (i.e., included in an IUCN threat category) or with decreasing populations. Hence establishing native species plantations among native forest remnants – especially in heavily fragmented landscapes – could have a positive effect in the conservation of threatened avifauna.     

Differential responses of the photoperiodic clock in two passerine birds possessing a strongly self-sustained circadian system

To investigate whether the photoperiodic clocks of species possessing strongly self-sustaining circadian clocks share identical features, we compared the full response cycle (initiation and termination of the response) in body mass and testes of the non-migratory house sparrow (Passer domesticus) with that of the migratory redheaded bunting (Emberiza bruniceps) under Nanda-Hamner experiments. Birds were exposed to a 36 h day (L:D=6:30 h), controls exposed to a 24 h day (L:D=6:18 h), for a period of 31 weeks. By week 18 of L:D=6:18 h, there was a small increase in body mass among sparrows, but not among buntings, and the testes of bunting did not grow, while those of sparrow grew slightly. The response to L:D=6:30 h is of particular interest. There was a rapid gain and subsequent loss in the body mass of bunting, but not of sparrows. Further, both species underwent a testicular cycle as if they were exposed to long days, but the response of sparrows was slower and hence delayed the attainment of peak testicular size. Such a differential response to exotic light cycles between these two photosensitive species, despite their similar circadian oscillatory properties (strong self-sustainment), could suggest a species-specific adaptation of the endogenous clock involved in photoperiodic regulation of avian seasonality.     

The direct and indirect effects of insectivory by birds in two contrasting Neotropical forests

A goal among community ecologists is to predict when and where trophic cascades occur. For example, several studies have shown that forest birds can limit arthropod abundances on trees, but indirect effects of bird predation (i.e. decreased arthropod damage to trees) are not always observed and their context is not well understood. Because productivity is one factor that is expected to influence trophic cascades, we compared the extent to which birds indirectly limit herbivore damage to trees in two lowland Neotropical forests that differed in seasonality of leaf production and rainfall. We compared the effects of bird predation on local arthropod densities and on damage to foliage through a controlled experiment using bird exclosures in the canopy and understory of two forests. We found that birds decreased local arthropod densities and leaf damage in the canopy of the drier site during periods of high leaf production, but not in the wetter forest where leaf production was low and sporadic throughout the year. Birds had no effect on arthropod abundances and leaf damage in the understory where leaf production and turnover rates were low. In support of these experimental interpretations, although we observed that arthropod densities were similar at the two sites, bird densities and the rate at which birds captured arthropods were greater at the drier, seasonally productive site. The influence of top-down predation by birds in limiting herbivorous insects appears to be conditional and most important when the production and turnover of leaves are comparatively high.Electronic Supplementary Material Supplementary material is available for this article at     

The direct and indirect effects of insectivory by birds in two contrasting Neotropical forests

A goal among community ecologists is to predict when and where trophic cascades occur. For example, several studies have shown that forest birds can limit arthropod abundances on trees, but indirect effects of bird predation (i.e. decreased arthropod damage to trees) are not always observed and their context is not well understood. Because productivity is one factor that is expected to influence trophic cascades, we compared the extent to which birds indirectly limit herbivore damage to trees in two lowland Neotropical forests that differed in seasonality of leaf production and rainfall. We compared the effects of bird predation on local arthropod densities and on damage to foliage through a controlled experiment using bird exclosures in the canopy and understory of two forests. We found that birds decreased local arthropod densities and leaf damage in the canopy of the drier site during periods of high leaf production, but not in the wetter forest where leaf production was low and sporadic throughout the year. Birds had no effect on arthropod abundances and leaf damage in the understory where leaf production and turnover rates were low. In support of these experimental interpretations, although we observed that arthropod densities were similar at the two sites, bird densities and the rate at which birds captured arthropods were greater at the drier, seasonally productive site. The influence of top-down predation by birds in limiting herbivorous insects appears to be conditional and most important when the production and turnover of leaves are comparatively high. Figure legends were missing in the original article published under Plant Animal Interactions, Oecologia (2005) 143: 106–166. The complete article is repeated here. The online version of the original article can be found at     

The effect of early experience on aggression in two territorial scorpaenid fishes

Synopsis The protogynous, Indo-Pacific serranid fish Anthias squamipinnis forms three types of social groupings, often within the same population: discrete groups, continuous masses, and intermediate groupings. In an intermediate grouping on Aldabra Island, Indian Ocean, females had larger home ranges than males and moved over the home range of several males. The movement rate of females into and out of specific locations within the grouping depended on the continuous presence of males. When males were removed, the movement rate increased. After females had completed sex reversal, thereby replacing the removed males, movement rate declined. These aspects of space use were identical to previous findings in discrete groups. It is suggested that the three types of social grouping each result from the interaction of these patterns of space use with plastic behavioral features at a particular site with particular substrate characteristics and a particular demographic history.     

On the evolution of clutch size and nest size in passerine birds

Summary I examined the hypothesis that the clutch size of some altricial birds may be limited by over-crowding of the nestlings in the nest, by comparing data on different species of European passerines. Large-sized birds build, relative to the body, larger nests than small-sized birds, both as regards the inner and the outer nest widths and as regards edge breadth; only inner nestcup depth did not change relatively to body size. Nest size also varied in relation to nesting place. Birds with open nests built off the ground had a rather narrow nestcup, whereas those with a domed nest, or which nest in a cavity, had a wide nestcup. When only open-nesters were compared, birds nesting on, or close to, the ground tended to have a wider nestcup than birds nesting above the ground. Inner nestcup width was correlated with the amount of mosses and lichens used in building the nest; the more of such materials the narrower the nestcup. The three variables: standardised body size, nesting place, and type of nesting material used accounted for 92% of the overall variation observed in inner nestcup width. When controlling for adult body size, clutch size was positively correlated with the size of the nestcup. A multiple regression analysis showed that relative nestcup depth, nest site, and type of nesting materials used, accounted for 64% of the overall variation in clutch size.     

Structure of communities of ground-dwelling animals at the junction of two phytogeographic zones

Changes in the structure of tenebrionid beetle, lizard and rodent communities along the aridity gradient that determines the position of a phytogeographic province boundary were studied to test: (1) whether there are two different species assemblages on either side of the boundary (2) the extent of their differentiation and (3) if they are composed of different or the same faunal elements. Several ordination methods were tested for their capacity to reflect community structure, and discriminant function analysis was selected as the primary method of ordination. Each of the ordination axes reflected a complex environmental gradient. The latter was different for each taxon. The gradient of productivity cross-cuts ecological space for each animal group in an individual manner. Revealed spatial assemblages of species were related to the level of productivity. There was one assemblage of species at high productivity and one or two assemblages occurred at low productivity in each taxon. The α–diversity curve of rodents changed weakly along the productivity gradient, whereas those of lizard and beetle communities were distinctly unimodal and had maxima near the middle of the gradient. β–diversity curves of rodents had a concave shape, but those of lizard and beetle communities increased from low productivity values to the middle of the gradient and after that weakly declined to the upper (productive) end of the gradient. Seven types of ranges or areographic groups of species were distinguished. Each species assemblage was composed of different faunal elements. Comparison of the results of ecological and areographic analyses demonstrated that two assemblages of rodents and lizards represent different guilds within the same community rather than different communities. The phytogeographic border for these taxa is an ecological rather than a geographical boundary. The difference between the two tenebrionid assemblages appears to be zoogeographical rather than ecological, and coincides with the phytogeographic boundary.     

Use of space and habitats by meadow voles at the home range,patch and landscape scales

Using capture/recapture methods, we examined the spatial usage patterns of Microtus pennsylvanicus within and between experimentally created habitat patches of three sizes (1.0, 0.25 and 0.0625 ha) and between a 20-ha fragmented and a 20-ha continuous habitat landscape. We tested the prediction that home ranges near patch edges would be qualitatively different from those in patch interiors, and that the edge:interior habitat ratio could be used to make predictions concerning the dispersion and spatial use of individuals occupying different sized patches and between landscapes with different habitat structure. We found adult females on patch edges to have larger and more exclusive home ranges, larger body sizes, longer residence times, and to reproduce at a higher frequency than those in patch interiors. These edge effects also appeared to be largely responsible for the greater proportion of larger, reproductive females we found in small than larger patches and in the fragmented than in the continuous habitat (control) landscape. The selection of higher quality edge habitats by dominant females and the relegation of sub-dominants to patch interiors provides an explanation for the observed differences in the distribution and performance of females over patches and between landscapes.     

Composition of uropygial gland waxes in relation to the classification of some passerine birds

The uropygial gland waxes of Aegithalos, Certhia, Leiothrix, Mesia, Panurus, Paradoxornis, Regulus, Remiz and Siva are monoester waxes composed of 2-; 2,x-; 2,x,y-; and 2,x,y,z-methyl-branched acids and unbranched as well as monomethyl-branched alcohols. Dimethylbranched alcohols occur in traces. All waxes are very similar. Chemotaxonomically all birds investigated are closely related and well separated from the family Paridae (tits).     

Ferns,frogs, lizards,birds and bats in forest fragments and shade cacao plantations in two contrasting landscapes in the Atlantic forest,Brazil

The traditional shade cacao plantations (cabrucas) of southern Bahia, Brazil, are biologically rich habitats, encompassing many forest-dwelling species. However, a critical question for the conservation management of this specific region, and the highly fragmented Atlantic forest in general, is to what extent the conservation value of cabrucas relies on the presence of primary forest habitat in the landscape. We investigated the relative importance of cabrucas and forests for the conservation of five diverse biological groups (ferns, frogs, lizards, birds and bats) in two contrasting landscapes in southern Bahia, one dominated by forest with some interspersed cabrucas, and one dominated by cabrucas with interspersed forest fragments. The community structure (richness, abundance and diversity) of all biological groups differed between cabrucas and forests, although these differences varied among groups. A high number of forest species was found in the cabrucas. However, there were pronounced differences between the two landscapes with regard to the ability of cabrucas to maintain species richness. Irrespective of the biological group considered, cabrucas located in the landscape with few and small forest fragments supported impoverished assemblages compared to cabrucas located in the landscape with high forest cover. This suggests that a greater extent of native forest in the landscape positively influences the species richness of cabrucas. In the landscape with few small forest fragments interspersed into extensive areas of shade cacao plantations, the beta diversity of birds was higher than in the more forested landscape, suggesting that forest specialist species that rarely ventured into cabrucas were randomly lost from the fragments. These results stress both the importance and the vulnerability of the small forest patches remaining in landscapes dominated by shade plantations. They also point to the need to preserve sufficient areas of primary habitat even in landscapes where land use practices are generally favorable to the conservation of biodiversity.     

Phenology of two interdependent traits in migratory birds in response to climate change

In migratory birds, arrival date and hatching date are two key phenological markers that have responded to global warming. A body of knowledge exists relating these traits to evolutionary pressures. In this study, we formalize this knowledge into general mathematical assumptions, and use them in an ecoevolutionary model. In contrast to previous models, this study novelty accounts for both traits—arrival date and hatching date—and the interdependence between them, revealing when one, the other or both will respond to climate. For all models sharing the assumptions, the following phenological responses will occur. First, if the nestling-prey peak is late enough, hatching is synchronous with, and arrival date evolves independently of, prey phenology. Second, when resource availability constrains the length of the pre-laying period, hatching is adaptively asynchronous with prey phenology. Predictions for both traits compare well with empirical observations. In response to advancing prey phenology, arrival date may advance, remain unchanged, or even become delayed; the latter occurring when egg-laying resources are only available relatively late in the season. The model shows that asynchronous hatching and unresponsive arrival date are not sufficient evidence that phenological adaptation is constrained. The work provides a framework for exploring microevolution of interdependent phenological traits.     

Home ranges, movements, and activity of wolves (Canis lupus) in the Dalmatian part of Dinarids, Croatia

Home-range sizes, movements, and daily activity of wolves (Canis lupus L. 1758) were studied in Dalmatia, Croatia in 1998–2001. The total home ranges (100% MCP) of two packs were 160 km² and 141 km², mean=150.5 km². Core areas (50% kernel) were 26.2 km² and 3.3 km², respectively. Differences in core area sizes were influenced by human activity—hunting and sheep grazing. Compared with random locations, wolf locations were closer to the nearest water source (mean=937 m) and farther from houses (mean=653 m). Wolves were significantly more active during the night than during the day (activity indexes were 0.53 vs. 0.35), and night activity was higher during summer (0.58), and lower during winter (0.48). A correlation was found between distances traveled and activity index (r=0.58, p=0.003). Home range, seasonal variations in home-range size, habitat use, and activity of wolves in Dalmatia were oriented to make the compromise from danger of proximity to humans and also to benefit from human-related food sources.     

Functional traits reveal the expansion and packing of ecological niche space underlying an elevational diversity gradient in passerine birds

Variation in species richness across environmental gradients may be associated with an expanded volume or increased packing of ecological niche space. However, the relative importance of these alternative scenarios remains unknown, largely because standardized information on functional traits and their ecological relevance is lacking for major diversity gradients. Here, we combine data on morphological and ecological traits for 523 species of passerine birds distributed across an Andes-to-Amazon elevation gradient. We show that morphological traits capture substantial variation in species dietary (75%) and foraging niches (60%) when multiple independent trait dimensions are considered. Having established these relationships, we show that the 14-fold increase in species richness towards the lowlands is associated with both an increased volume and density of functional trait space. However, we find that increases in volume contribute little to changes in richness, with most (78%) lowland species occurring within the range of trait space occupied at high elevations. Taken together, our results suggest that high species richness is mainly associated with a denser occupation of functional trait space, implying an increased specialization or overlap of ecological niches, and supporting the view that niche packing is the dominant trend underlying gradients of increasing biodiversity towards the lowland tropics.