Esa Huhta

Forest management is associated with physiological stress in an old-growth forest passerine.

We investigated how physiological stress in an area–sensitive old–growth forest passerine, the Eurasian treecreeper (Certhia familiaris), is associated with forest fragmentation and forest structure. We found evidence that the concentrations of plasma corticosterone in chicks were higher under poor food supply in dense, young forests than in sparse, old forests. In addition, nestlings in large forest patches had lower corticosterone levels and a better body condition than in small forest patches. In general, corticosterone levels were negatively related to body condition and survival. We also found a decrease in corticosterone levels within the breeding season, which may have been a result of an increase in food supply from the first to the second broods. Our results suggest that forest fragmentation may decrease the fitness of free–living individual treecreepers.

Effects of forest patch size on physiological stress and immunocompetence in an area-sensitive passerine, the Eurasian treecreeper (Certhia familiaris): an experiment

We manipulated the primary brood size of Eurasian treecreepers (Certhia familiaris) breeding in different sized forest patches (0.5–12.8 ha) in moderately fragmented landscapes. We examined the effects of brood size manipulation (reduced, control, enlarged) and forest patch size on physiological stress (heterophil–lymphocyte ratios; H/L), body condition and cell–mediated immunocompetence (phytohaemagglutinin test). Nestlings H/L ratios were negatively related to forest patch area in control and enlarged broods, whereas no effects were found in reduced broods. The effects of forest patch area were strongest in enlarged broods, which had, in general, twofold higher H/L ratios than control and reduced broods. The elevated H/L ratios were positively related to nestling mortality and negatively correlated with body–condition indices suggesting that the origin of stress in nestlings was mainly nutritional. Cell–mediated immunity of nestlings was not related to brood manipulation or to forest patch size. Also, the H/L ratios of adults were not related to brood manipulation or forest patch size. In addition, parental H/L ratios and body condition were not related to nestling H/L ratios. Our results suggest that during the breeding period the deleterious effects of habitat loss are seen explicitly in growing young.

Foraging conditions, tooth wear and herbivore body reserves: a study of female reindeer

Abstract Several aspects of the life history of reindeer (Rangifer tarandus) are related to the nutritional condition of the animals. Moreover, compensatory growth and fattening in summer decreases with age. The interaction of tooth wear and the standing crop of lichens on age-related variation in body size and tissue reserves was examined to evaluate the proximate causes of density-dependent food limitation on life history parameters in female reindeer. Studies in nine semi-domesticated free-ranging reindeer herds showed that molar height depended on the mean standing crop of terrestrial lichens in winter habitats. The extent of tooth wear had the strongest effect on body reserves among the oldest females (11–14 years). This indicates that severe tooth wear limits the animals´ ability to process food efficiently and, hence, to maintain their body reserves. Both tooth wear and the biomass of lichens influenced body mass in old females, probably because on heavily exploited winter ranges reindeer had to use higher proportions of lower-ranking coarser foods, especially dwarf shrubs.

Effects of landscape structure and forest reserve location on old-growth forest bird species in Northern Finland

Old-growth forest birds in Fennoscandia have sharply declined in numbers during the last decades apparently due to commercial forest harvesting and fragmentation of old-growth forests. Conservation measures have led to the establishment of a forest reserve network to assure the persistence of forest birds at a regional scale. However, little is known about the effects of landscape structure within and around the reserves on the distribution of old-growth forest birds. We used a hierarchical approach to address the questions of how landscape structure and composition within forest reserves, landscape composition of surrounding areas and reserve location affect the abundance of resident, old-growth forest birds in the Northern Finnish forest reserve network. The positive role of particular landscape features on bird distribution indicates that both the proportion of old-growth forests and the structure of boreal landscape mosaic has an important role in determining the distribution of these birds. The landscape composition surrounding the reserves proved to be only a weak predictor in species distribution models, which argues against the primary role of the surrounding matrix in determining species distribution within forest reserves. Reserves located near the Russian border showed a higher abundance of old-growth birds than more western ones. Once east-west gradients in overall landscape composition had been accounted for, however, reserves did not differ significantly in the number of species present. These results suggest that landscape gradients, rather than ecological processes such as the presence of source areas located along the border with Russia, are the main determinant of the distribution of old-growth forest birds in the Finnish reserve network. We propose that to enhance regional persistence of old-growth forest birds, conservation efforts should be primarily directed towards the protection and enhancement of forest habitat quality and natural heterogeneity of landscapes within targeted areas.

Forest fragmentation is associated with primary brood sex ratio in the treecreeper (Certhia familiaris)

We studied the primary brood sex ratio of an old–growth forest passerine, the Eurasian treecreeper (Certhia familiaris), along a gradient of forest fragmentation. We found evidence that male nestlings were more costly to produce, since they suffered twofold higher nestling mortality and were larger in body size than females. Furthermore, the proportion of males in the brood was positively associated with the provisioning rate and the amount of food delivered to the nestlings. During the first broods, a high edge density and a high proportion of pine forests around the nests were related to a decreased production of males. The densities of spiders, the main food of the treecreeper, were 38% higher on spruce trunks than on pine trunks. This suggests that pine–dominated territories with female–biased broods may have contained less food during the first broods. The observation was further supported by the fact that the feeding frequencies were lower in territories with high proportions of pines. In the second broods, territories with a high forest patch density produced female–biased broods, whereas high–quality territories with a large amount of deciduous trees and mixed forests produced male–biased broods. Our results suggest that habitat quality as measured by habitat characteristics is associated with sex allocation in free–living birds.

Temporal variation of bird assemblages in moderately fragmented and less-fragmented boreal forest landscapes: a multi-scale approach.

Abstract To test whether landscape structure affects the temporal variability of bird populations and species turnover, we estimated breeding bird abundances in a boreal forest area in northern Finland during the years 1990-1995. The analyses were conducted at three spatial scales: point-count station (4 ha), block (12.5 km2), and landscape unit levels. At the census point scale, temporal variability (CV) of generalist species correlated negatively with amount of unforested habitat. At the block scale, temporal variability of forest edge and managed forest species correlated negatively with the amount of forested area in the landscape. No response was observed among sedentary, migratory, and virgin forest species at these lower scales. At the landscape unit scale, forest-edge and managed-forest species such as chaffinch (Fringilla coelebs L.), and redpoll (Carduelis flammea L.) showed higher temporal variability, whereas sedentary and virgin forest species such as cuckoo (Cuculus canorus L.), raven (Corvus corax L.), and hooded crow (Corvus corone cornix L.) showed lower temporal variability in the moderately fragmented landscape than in the less-fragmented landscape. Of the virgin-forest species, crossbills (Loxia spp.) and titmice (Parus spp.) showed more variability in the less-fragmented landscape, whereas the rest of the virgin-forest species (hawks, grouses, woodpeckers, etc.) reflected more temporal variability in the moderately fragmented landscape unit. The results were only partially in accordance with expected trends, and there were differences between scales in variability patterns of species and species groups. Large-scale landscape characteristics mainly affected the temporal variability of sedentary and virgin-forest species, whereas species not restricted to special habitat structures were more affected by smaller-scale habitat structure.

A method for assessing ecological values to reconcile multiple land use needs

We present a new method for ecologically sustainable land use planning within multiple land use schemes. Our aims were (1) to develop a method that can be used to locate important areas based on their ecological values; (2) to evaluate the quality, quantity, availability, and usability of existing ecological data sets; and (3) to demonstrate the use of the method in Eastern Finland, where there are requirements for the simultaneous development of nature conservation, tourism, and recreation. We compiled all available ecological data sets from the study area, complemented the missing data using habitat suitability modeling, calculated the total ecological score (TES) for each 1 ha grid cell in the study area, and finally, demonstrated the use of TES in assessing the success of nature conservation in covering ecologically valuable areas and locating ecologically sustainable areas for tourism and recreational infrastructure. The method operated quite well at the level required for regional and local scale planning. The quality, quantity, availability, and usability of existing data sets were generally high, and they could be further complemented by modeling. There are still constraints that limit the use of the method in practical land use planning. However, as increasing data become available and open access, and modeling tools improve, the usability and applicability of the method will increase.