Nest-site Selection Behaviour Research Articles

Self-Organizing Strategy Design for Heterogeneous Coexistence in the Sub-6 GHz

Due to the worldwide ongoing pressure to massively exploit the Sub-6 GHz spectrum for the deployment of independently-operated and heterogeneous networks, innovative solutions for network coexistence are deeply required. Hence, in this paper, we design a self-organizing strategy with the aim of minimizing the coexistence interference among heterogeneous networks sharing the Sub-6 GHz spectrum. The design is performed under the constraints of promoting selfless network utilization and avoiding any direct communication among the heterogeneous networks. For this, we develop an analytical framework, grounded on the nest-site selection behavior observed in honeybee swarms, to model the coexistence problem among multiple heterogeneous networks. Specifically, first, different heterogeneous networks are mapped into different populations and the allocation of a Sub-6 GHz band to a network is mapped into the population commitment. Then, the evolution of the commitment process is described through a multi-dimensional differential system. We analytically study the stability of such a system at the equilibrium, and we derive the conditions that assure the optimal allocation of the available Sub-6 GHz bands among the different heterogeneous networks. Finally, the proposed strategy is validated through an extensive performance evaluation.

NeSS: A modified artificial bee colony approach based on nest site selection behavior

This paper proposes a new version of the Artificial Bee Colony (ABC) optimization algorithm based on the natural nest-site selection behavior of honey bee swarms. The algorithm offers three advantages. First, the responsibility of bees in the proposed algorithm is dynamic, meaning that bee agents may change states (explorer, resting, observer, and committed) during the execution. New feasible solutions are randomly generated in every iteration by varying the numbers of bee agents, thus introducing diversified candidate solutions into the solution space. Second, each bee records its own satisfaction with each nest-site and this satisfaction value is added to the quality measure for the nest site, allowing lower quality nest sites to be retained as candidate solutions and again providing greater diversity. Third, a quorum mechanism provides the stopping criterion, instead of the maximum cycle number (MCN). This mechanism helps the algorithm to converge more quickly. Experiments on the traveling salesman and clustering problems have been conducted in order to observe the algorithm performance. The results show promising performance in solving combinatorial problems when compared with other state-of-the-art algorithms. In addition, the proposed algorithm can converge more quickly with the quorum mechanism.

A Design Pattern for Decentralised Decision Making.

The engineering of large-scale decentralised systems requires sound methodologies to guarantee the attainment of the desired macroscopic system-level behaviour given the microscopic individual-level implementation. While a general-purpose methodology is currently out of reach, specific solutions can be given to broad classes of problems by means of well-conceived design patterns. We propose a design pattern for collective decision making grounded on experimental/theoretical studies of the nest-site selection behaviour observed in honeybee swarms (Apis mellifera). The way in which honeybee swarms arrive at consensus is fairly well-understood at the macroscopic level. We provide formal guidelines for the microscopic implementation of collective decisions to quantitatively match the macroscopic predictions. We discuss implementation strategies based on both homogeneous and heterogeneous multiagent systems, and we provide means to deal with spatial and topological factors that have a bearing on the micro-macro link. Finally, we exploit the design pattern in two case studies that showcase the viability of the approach. Besides engineering, such a design pattern can prove useful for a deeper understanding of decision making in natural systems thanks to the inclusion of individual heterogeneities and spatial factors, which are often disregarded in theoretical modelling.

Effects of Habitat on Breeding Success in a Declining Migrant Songbird: the Case of Pied FlycatcherFicedula hypoleuca

Habitat is a key determinant of breeding success in hole-nesting birds. Identifying the factors that influence breeding success is important in understanding nest-site selection behaviour and devising appropriate conservation strategies. This is especially true for declining species like the migratory Pied Flycatcher Ficedula hypoleuca. Here, I analyse the effect of 24 habitat variables on clutch size, hatching success and fledging success for 137 Pied Flycatcher nests in Gloucestershire, UK, using volunteer-collected data from a 5-year period. More successful nests tended to be located in areas with a lower density of mature trees but abundant saplings. Tree and sapling species richness was also important. Success was positively related to abundance of Oak Quercus robur and Silver Birch Betula pendula and negatively related to Beech Fagus sylvatica, Sycamore Acer pseudoplatanus and Bracken Pteridium aquilinum. Success was lower in boxes facing south-southwest and higher in boxes located on sorter trees. Despite Pied Flycatchers often being regarded as birds of grazed (open) woodland, success was not related directly to grazing. Close proximity to footpaths was associated with significantly lower clutch size, numbers of young to fledge, and percentage success, while close proximity to water was associated with increased success at all stages of breeding. This is a single-site study and the generality of these findings at other sites cannot be assumed without empirical testing. However, the results provide useful additional insight into success-habitat interactions in this species that, to some extent, challenge the general view of Pied Flycatchers, in the UK at least, as grazed woodland specialists.

Nest-site preference of Hooded Crow (Corvus cornix L.) in Debrecen, Hungary

In the past decade, the population of the Hooded Crow has shown significant growth in Debrecen, Hungary. The aim of this study was to become acquainted with the nest-site selection behavior of Hooded Crows in urban spaces. While our research revealed that the Hooded Crow is not particular when it comes to selecting among tree species for nesting, we did notice differences regarding nesting height. Hooded Crows living in the city build their nests higher up than those living outside Debrecen’s city limits. We also discovered a slight, insignificant difference between nesting heights and tree species, which is probably due to the different characteristics of the given tree species. As for nesting heights, we found that in typical urban habitats there were no relevant differences. However, when we compared these habitats in pairs, it came to light that nesting heights -when comparing solitary trees - wood segments and tree rows - wooded segments- did show significant differences, which can be explained by the various conditions provided by the habitats mentioned.In summary, the following results emerged from our research:1. The Hooded Crow prefers approximately the same nesting heights in all kinds of habitats, urban environment and tree species.2. The nesting height does not significantly depend on the habitat itself or on the tree species.

Effects of intraguild predators on nest-site selection by prey

Nest-site selection involves tradeoffs between the risk of predation (on females and/or nests) and nest-site quality (microenvironment), and consequently suitable nesting sites are often in limited supply. Interactions with "classical" predators (e.g., those not competing for shared resources) can strongly influence nest-site selection, but whether intraguild predation also influences this behavior is unknown. We tested whether risk of predation from an intraguild predator [the diurnal scincid lizard Eutropis (Mabuya) longicaudata] influences nest-site selection by its prey (the nocturnal gecko Gekko hokouensis) on Orchid Island, Taiwan. These two species putatively compete for shared resources, including invertebrate prey and nesting microhabitat, but the larger E. longicaudata also predates G. hokouensis (but not its hard-shelled eggs). Both species nested within a concrete wall containing a series of drainage holes that have either one ("closed-in") or two openings ("open"). In allopatry, E. longicaudata preferred to nest within holes that were plugged by debris (thereby protecting eggs from water intrusion), whereas G. hokouensis selected holes that were open at both ends (facilitating escape from predators). When we experimentally excluded E. longicaudata from its preferred nesting area, G. hokouensis not only nested in higher abundances, but also modified its nest-site selection, such that communal nesting was more prevalent and both open and closed-in holes were used equally. Egg viability was unaffected by the choice of hole type, but was reduced slightly (by 7%) in the predator exclusion area (presumably due to higher local incubation temperatures). Our field experiment demonstrates that intraguild predators can directly influence the nest density of prey by altering maternal nest-site selection behavior, even when the predator and prey are active at different times of day and the eggs are not at risk of predation.

Características de la anidación de la tortuga verde Chelonia mydas (Testudinata, Cheloniidae) en la playa Caleta de los Piojos, Cuba, a partir de marcaciones externas

Nesting characteristics of the Green turtle Chelonia mydas (Testudinata, Cheloniidae) at Caleta de los Piojos Beach, Cuba, determined from tagging studies Green turtle (Chelonia mydas) females nesting during 2002 and 2003 nesting seasons at Caleta de los Piojos Beach, Cuba, were studied using data from individual tagging. Nesting occurred on average twice per season with a mean interval of 10.9 days. A high number of turtles nested only once per season (39% and 40% respectively). The percentage of failed multiple nesting attempts was high in both seasons. However, the percentage of failed attempts prior to the first nesting was higher in the 2003 season. Vegetation areas seem to be the most suitable sites for nesting and have a significant effect on nest-site selection behaviour. Fidelity to first nest-site was high, 50.3% and 72.9% respectively for 2002 and 2003. Observed mean clutch size (117 eggs) was closely related to body dimensions.

IMPACT OF NEST-SITE SELECTION ON NEST SUCCESS AND NEST TEMPERATURE IN NATURAL AND DISTURBED HABITATS

Nest-site selection behavior is a maternal effect that contributes to offspring survival and variation in offspring phenotypes that are subject to natural selection. We investigated nest-site selection and its consequences in the snapping turtle, Chelydra serpentina, in northwestern Illinois. We evaluated nest-site selection at both the microhabitat and habitat patch levels. Turtles selected nest sites with shorter vegetation, more open sand, and fewer cacti than random locations. These microhabitat characteristics described sandy patches where both nest density and success were higher compared to grassy patches in 1999. We subsequently investigated nest-site selection within two discrete subdivisions of the study area that varied in the degree of human disturbance to determine if nesting behavior, nest success, or nest temperatures were affected. The tendency to nest in sandy patches was much stronger at the natural site due to habitat modifications at the residential site that have blurred the distinction between sandy and grassy patches. Additionally, the residential site had a high density of nests within 5 m of houses and a fence (both areas with disturbed habitat similar to sandy patches), compared to the overall density. Thus, nest success associated with sandy patches may be compromised at the residential site; an ecological trap may result in lower nest success in areas with preferred microhabitat characteristics. Despite a similar basis for nest-site selection in terms of microhabitat characteristics at both sites, nest temperatures were correlated with microhabitat characteristics used to select nest sites only at the natural site. Nest temperatures at the residential site were instead correlated only with the percentage overstory vegetation cover and therefore averaged 2°C lower than at the natural site, a temperature difference that influenced offspring sex. The higher percentage overstory vegetation cover at the residential site was due to human alterations of the habitat, and may serve to extend the ecological trap biasing the sex ratio of this population. This study illustrates the importance of (1) nest-site selection as a substantive maternal effect, (2) understanding habitat use during crucial life-history events, and (3) the potential for human disturbance to modify offspring phenotypes and negatively impact nest success despite adaptive nesting behavior.

Colony and Nest-Site Selection Behaviour in Silver Gulls <I>Larus novaehollandiae</I> in Queensland, Australia

Colony and Nest-Site Selection Behaviour in Silver Gulls <I>Larus novaehollandiae</I> in Queensland, Australia

Breeding success and nest site stereotypy in a population of Brewer's Blackbirds (Euphagus cyanocephalus).

Nest site stereotypy and nest-site related breeding success was studied in a population of Brewer's Blackbirds in eastern Washington, USA. Four types of nest sites could be distinguished. Based on individually colour-ringed nestlings, imprinting or genetic fixation of a particular type of nest site can be ruled out since there is no correspondence between the type of nest a bird grew up in and the type it used when breeding. Bush nests make up about two thirds of all nests, and they are relatively more frequent than the other types in the first half of the breeding season, whereas the other types become more frequent in the second half of the nesting season. Differential breeding success was studied and its dependence on colony composition was investigated.The hypothesis that the birds are able to utilize nest site flexibility as an anti-predator strategy within colonies is not supported. Some nest sites are predictably less suitable at a particular time of the season, and the birds have been at least partially able to incorporate this into their nest-site selection behaviour. There is no optimal type of nest site for all conditions. The selective pressures on birds using the different types of nest sites are discussed.