Harris, R. J. & Reed, J. M. 2002: Behavioral barriers to non-migratory movements of birds. — Ann. Zool. Fennici 39: 275–290.

Although effects of physical barriers to animal movement are well established, the behavioral inhibition of individuals moving across habitat gaps, ecotones, and inter-patch (matrix) habitat has received little attention. Birds are often cited as a taxon in which movements should not be disrupted by gaps in landscape connectivity. Here we synthesize evidence from the literature for behavioral inhibition of movements by birds, and find that a wide variety of behavioral inhibitions to movements have been observed. We also present a model for describing edge or gap permeability that incorporates the propensity of an individual to cross an ecotone or enter a gap, and the effect of gap width. From published observations, we propose five ecologically based patterns of behavioral inhibition of bird movements as hypotheses: that habitat specialists, understory-dwellers, tropical species, solitary species, and non-migratory species are more inhibited than are species that are their ecological counterparts. Understanding what animals perceive as impediments to movement will contribute to efforts to maintain populations through landscape design, and will allow us to predict the types and degrees of habitat fragmentation that will cause persistence problems for various species.

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Hauber, M. E. 2002: First contact: A role for adult-offspring social association in the species recognition system of brood parasites. — Ann. Zool. Fennici 39: 291–305.

Social parasites typically develop in the absence of close relatives and receive parental care from foster parents. How do these parasitic offspring later recognize their kin or conspecifics as compatible social or sexual partners? Recent evidence suggests that association of fledgling obligate brood parasitic birds with adults of their own species may be more frequent than previously thought. This early social contact has been implicated to function in cuing species-typical behaviors, including conspecific recognition. I tested assumptions and predictions of this "first contact" hypothesis using field observations and laboratory choice trials with brown-headed cowbirds (Molothrus ater). In support of the "first contact" scenario, playback experiments in the field indicated that female cowbirds were predictably detected near fledgling cowbirds. In the laboratory, adult cowbirds of both sexes spent consistently more time in the proximity of conspecific juveniles than adult hosts. Independent, hand-reared juvenile cowbirds also showed consistent biases in spatial preference for female cowbirds over hosts, even in the absence of prior conspecific experience. This preference for conspecific stimuli by juvenile parasites may have been mediated not only by phenotypic but also by behavioral cues in choice trials because the heterospecific social stimuli more frequently directed aggressive behaviors at the young cowbirds than did conspecific stimuli. These findings support the claim that, against conventional wisdom, adult brood parasites may play a role in the earliest stages of social development of conspecific young. Returning to parasitized broods to facilitate the conspecific recognition of their own offspring is likely to increase the fitness of, and represent a form of parental care by, territorial female cowbirds because most parasitic fledglings encountered within their breeding range are predictably their progeny.

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Starks, P. T. 2002: The adaptive significance of stabilimenta in orb-webs: a hierarchical approach. — Ann. Zool. Fennici 39: 307–315.

Conditional strategy theory provides a theoretical and experimental framework from which to predict both population differences in the expression of alternative behavioral phenotypes and the condition above and below which individuals will perform different tactics. Here I briefly review the current functional explanations for stabilimentum production in orb-web spiders and reinterpret previous results within a conditional strategy framework. I argue that using this framework and incorporating a hierarchical approach to the multiple possible selective benefits of the structure is sufficient to explain some of the seemingly contradictory results in the literature.

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Kauhala, K. & Tiilikainen, T. 2002: Radio location error and the estimates of home range size, movements, and habitat use: a simple field test. — Ann. Zool. Fennici 39: 317–324.

The effect of location error on the estimates of home range size, movements and habitat use of an animal in a radio-tracking study was tested in the field. One person, outfitted with a transmitter (made for hares) and a GPS-instrument, imitated hare movements in the woods, while researchers located her every 15 min. using techniques used to locate true hares. The mean location error was 281 m and varied between seasons and persons. The route the `hare' moved, calculated from radio locations, was 1.5 x the true route, but radio-tracking gave a correct picture of the home range size, especially that of the core area. When habitat patches were small (mean size 2.9 ha), only 22% of the radio locations were in a correct forest patch, whereas radio-tracking gave a better picture of habitat use when habitat patches were larger (mean size 7.1 ha). In radio-tracking studies, the effect of the location error on the reliability of the results should thus always be tested and taken into account. The acceptable error depends on the aims of the study.

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Sundell, J. & Norrdahl, K. 2002: Body size-dependent refuges in voles: an alternative explanation of the Chitty effect. — Ann. Zool. Fennici 39: 325–333.

In cyclic vole populations the body size of voles tends to vary with population density, voles being smaller in the decline and low density phases than in the peak phase of the cycle. We have studied this `Chitty effect' using field measurements of vole (Microtus agrestis, M. rossiaemeridionalis) body size and predator densities, and laboratory experiments on the minimum passable hole size for voles and their major predator, weasels (Mustela nivalis nivalis). We found that many voles can pass through smaller holes than the smallest weasels, which implies that these small voles can have a refuge from weasel predation. Consequently, predation pressure is expected to be greater on larger voles. In the field we found a negative association between the mean body size of voles and weasel abundance. Our laboratory and field results suggest that size selective predation might be an important cause of the observed smaller size of voles in the decline phase of cycles.

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Virtanen, R., Parviainen, J. & Henttonen, H. 2002: Winter grazing by the Norwegian lemming (Lemmus lemmus) at Kilpisjärvi (NW Finnish Lapland) during a moderate population peak. — Ann. Zool. Fennici 39: 335–341.

Winter grazing of the Norwegian lemming (Lemmus lemmus) was studied at Kilpisjärvi at the edge of the Scandinavian mountain chain during a moderate population peak and the year after. Signs of lemming grazing were recorded soon after snow melted along elevational and topographic gradients on three mountains. On all mountains in both winters, grazing peaked at the lower part of the alpine zone and then declined both in the forest zone and on the highest summits. Grazing was most intense in snow-protected depressions and slopes, whereas hillocks with thin snow were very little grazed. In the first winter, grazing was most intense in the mountains juxtaposed to the Scandes. In the following winter, grazing had clearly declined on these mountains, but remained unchanged at the most distant mountain from the Scandes. Topography and snow conditions played a key role for over-wintering of lemmings, but no clear link between annual variation in snow conditions and grazing patterns could be detected. The spatio-temporal pattern of lemming grazing conformed to a travelling wave type population dynamics.

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