Use of the sun compass by monocularly occluded homing pigeons in a food localisation task in an outdoor arena

Functional asymmetries of the avian visual system can be studied in monocularly occluded birds, as their hemispheres are largely independent. Right and left monocularly occluded homing pigeons and control birds under binocular view have been trained in a food localisation task in an octagonal outdoor arena provided with one coloured beacon on each wall. The three groups were tested after the removal of the visual beacons, so to assess their sun compass learning abilities. Pigeons using the left eye/right hemisphere system exhibited slower learning compared to the other monocular group. During the test in the arena void of visual beacons, the three groups of birds, regardless of their visual condition, were generally able to identify the training sector by exclusively relying on sun compass information. However, the directional choices of the pigeons with the left eye/right hemisphere in use were significantly affected by the removal of the beacons, while both control pigeons and birds with the right eye/left hemisphere in use displayed unaltered performances during the test. A subsample of pigeons of each group were re-trained in the octagonal arena with visual beacons present and tested after the removal of visual beacons after a 6 h fast clock-shift treatment. All birds displayed the expected deflection consistent to the sun compass use. While birds using either the left or the right visual systems were equally able to learn a sun compass-mediated spatial task, the left eye/right hemisphere visual system displayed an advantage in relying on visual beacons

GPS tracking technology and re-visiting the relationship between the avian visual Wulst and homing pigeon navigation

: Within their familiar areas homing pigeons rely on familiar visual landscape features and landmarks for homing. However, the neural basis of visual landmark-based navigation has been so far investigated mainly in relation to the role of the hippocampal formation. The avian visual Wulst is the telencephalic projection field of the thalamofugal pathway that has been suggested to be involved in processing lateral visual inputs that originate from the far visual field. The Wulst is therefore a good candidate for a neural structure participating in the visual control of familiar visual landmark-based navigation. We repeatedly released and tracked Wulst-lesioned and control homing pigeons from three sites about 10-15 km from the loft. Wulst lesions did not impair the ability of the pigeons to orient homeward during the first release from each of the three sites nor to localise the loft within the home area. In addition, Wulst-lesioned pigeons displayed unimpaired route fidelity acquisition to a repeated homing path compared to the intact birds. However, compared to control birds, Wulst-lesioned pigeons displayed persistent oscillatory flight patterns across releases, diminished attention to linear (leading lines) landscape features, such as roads and wood edges, and less direct flight paths within the home area. Differences and similarities between the effects of Wulst and hippocampal lesions suggest that although the visual Wulst does not seem to play a direct role in the memory representation of a landscape-landmark map, it does seem to participate in influencing the perceptual construction of such a map

Context-dependent foraging habitat selection in a farmland raptor along an agricultural intensification gradient

Gradients of agricultural intensification in agroecosystems may determine uneven resource availability for predators relying on these man-made habitats. In turn, these variations in resource availability may affect predators’ habitat selection patterns, resulting in context-dependent habitat selection. We assessed the effects of gradients of landscape composition and configuration on habitat selection of a colonial farmland bird of prey, the lesser kestrel (Falco naumanni), relying on 76 GPS-tracked nestling-rearing individuals from 10 populations scattered along an agricultural intensification gradient. Analyses were conducted considering two ecological levels of aggregation (the population and the individual) and two spatial scales of habitat availability (the colony surroundings and the individual home-range). Overall, non-irrigated croplands and semi-natural grasslands were the most preferred habitats at both spatial scales. At the colony scale, lesser kestrels showed a preference for grassland compared to non-irrigated crops, whereas the opposite was the case within individual home-ranges. Conversely, croplands were positively selected with comparable intensity at both spatial scales. Strong selection for grassland at the colony scale highlights the importance of this semi-natural habitat for the species. The weaker preference for grassland at the home-range scale is likely due to the phenology and structure of the vegetation in the late breeding season. Spatial scale differences in selection patterns may thus derive from spatiotemporal changes in resource availability through the breeding season. The strength of selection for the two most used habitats varied markedly among individuals. At the spatial scale of the colony, individual selection strength for grasslands increased with decreasing compositional diversity of the surrounding landscape, suggesting that agroecosystem heterogeneity may at least partly buffer the loss of semi-natural habitats. At the within homerange scale, higher cropland availability reduced the strength of individual preference for this habitat, suggesting a negative functional response possibly related to density-dependent processes acting on foraging movements. Our study provides evidence that farmland species show context-dependent habitat selection patterns in response to landscape gradients shaped by agricultural intensification as well as by intrinsic characteristics and habitat availability. Our findings highlight the importance of addressing both individual and population-level variability and considering multiple spatial scales in studies of habitat selection to inform species’ management and conservation

Environmental Factors Affecting Amphibian Communities in River Basins of the Southern Apennines

The study of the environmental features affecting amphibian communities is a priority task for addressing effective conservation initiatives. In the southern edge of the Apennines (Sila Massif, Calabria Region, Italy), we surveyed the distribution of amphibians in lotic freshwater habitats (eight rivers, 17 sampling stations, 87 transects) and recorded nine environmental variables, including the occurrence of potential predators (fish and Eurasian otter Lutra lutra), potentially affecting the distribution and breeding success of amphibian species. A total of seven amphibian species was recorded (75.9% of transects). Fish occurred in all rivers while the otter was found in four rivers (Amato, Lese, Neto, and Savuto). Illuminance and bank heterogeneity were the main factors affecting amphibian reproduction, while neither otter nor fish presence showed significant effects on the amphibian community. Overall, habitat complexity and coevolution history seemed to shape the distribution of amphibians and their breeding sites, while the ongoing recolonization of the study area by the otter is expected to have a negligible impact on the richness of the amphibian community

Vegetation height and structure drive foraging habitat selection of the lesser kestrel (Falco naumanni) in intensive agricultural landscapes

Habitat selection in animals is a fundamental ecological process with key conservation implications. Assessing habitat selection in endangered species and populations occupying the extreme edges of their distribution range, or living in highly anthropized landscapes, may be of particular interest as it may provide hints to mechanisms promoting potential range expansions. We assessed second- and third-order foraging habitat selection in the northernmost European breeding population of the lesser kestrel (Falco naumanni), a migratory falcon of European conservation interest, by integrating results obtained from 411 direct observations with those gathered from nine GPS-tracked individuals. The study population breeds in the intensively cultivated Po Plain (northern Italy). Direct observations and GPS data coincide in showing that foraging lesser kestrels shifted their habitat preferences through the breeding cycle. They positively selected alfalfa and other non-irrigated crops during the early breeding season, while winter cereals were selected during the nestling-rearing phase. Maize was selected during the early breeding season, after sowing, but significantly avoided later. Overall, vegetation height emerged as the main predictor of foraging habitat selection, with birds preferring short vegetation, which is likely to maximise prey accessibility. Such a flexibility in foraging habitat selection according to spatio-temporal variation in the agricultural landscape determined by local crop management practices may have allowed the species to successfully thrive in one of the most intensively cultivated areas of Europe. In the southeastern Po Plain, the broad extent of hay and non-irrigated crops is possibly functioning as a surrogate habitat for the pseudo-steppe environment where most of the European breeding population is settled, fostering the northward expansion of the species in Europe. In intensive agricultural landscapes, the maintenance of alfalfa and winter cereals crops and an overall high crop heterogeneity (deriving from crop rotation) is fundamental to accommodate the ecological requirements of the species in different phases of its breeding cycle

Context-dependent foraging habitat selection in a farmland raptor along an agricultural intensification gradient

Gradients of agricultural intensification in agroecosystems may determine uneven resource availability for predators relying on these man-made habitats. In turn, these variations in resource availability may affect predators’ habitat selection patterns, resulting in context-dependent habitat selection. We assessed the effects of gradients of landscape composition and configuration on habitat selection of a colonial farmland bird of prey, the lesser kestrel (Falco naumanni), relying on 76 GPS-tracked nestling-rearing individuals from 10 populations scattered along an agricultural intensification gradient. Analyses were conducted considering two ecological levels of aggregation (the population and the individual) and two spatial scales of habitat availability (the colony surroundings and the individual home-range). Overall, non-irrigated croplands and semi-natural grasslands were the most preferred habitats at both spatial scales. At the colony scale, lesser kestrels showed a preference for grassland compared to non-irrigated crops, whereas the opposite was the case within individual home-ranges. Conversely, croplands were positively selected with comparable intensity at both spatial scales. Strong selection for grassland at the colony scale highlights the importance of this semi-natural habitat for the species. The weaker preference for grassland at the home-range scale is likely due to the phenology and structure of the vegetation in the late breeding season. Spatial scale differences in selection patterns may thus derive from spatio-temporal changes in resource availability through the breeding season. The strength of selection for the two most used habitats varied markedly among individuals. At the spatial scale of the colony, individual selection strength for grasslands increased with decreasing compositional diversity of the surrounding landscape, suggesting that agroecosystem heterogeneity may at least partly buffer the loss of semi-natural habitats. At the within home-range scale, higher cropland availability reduced the strength of individual preference for this habitat, suggesting a negative functional response possibly related to density-dependent processes acting on foraging movements. Our study provides evidence that farmland species show context-dependent habitat selection patterns in response to landscape gradients shaped by agricultural intensification as well as by intrinsic characteristics and habitat availability. Our findings highlight the importance of addressing both individual and population-level variability and considering multiple spatial scales in studies of habitat selection to inform species’ management and conservation